DESC:FIELD OF THE INVENTION
The present invention relates to a hybrid composite material with high impact resistance and a method of fabrication thereof. More particularly, the present invention discloses a lightweight hybrid composite material with high impact resistance and a method of fabrication thereof that can provide protection from severe impact and projectiles to buildings, vehicles, and other structures for domains such as mining industry, aviation, space, civil infrastructures, oil and gas industry etc.

BACKGROUND OF THE INVENTION
An event causes severe impact when a significant amount of energy is released suddenly, resulting in a shock wave. Such events can be caused by various sources, including industrial accidents, natural disasters such as volcanic eruptions or earthquakes, and intentional human activities or events of severe impact . Accidental events of severe impact can occur in industrial sites, such as chemical plants, refineries, and storage facilities, due to improper handling of materials, equipment malfunction, or human error. Intentional events of severe impact can be due to acts of violence by terrorists or criminal organizations, aiming to cause destruction and harm to people and infrastructure.

The primary effects of an event causing severe impact are shock waves, thermal radiation, and debris. These waves are shock waves that propagate through the air and can cause structural damage, collapse of buildings, and injuries or death to people. Thermal radiation is the heat energy released by the events of severe impact that can cause burns and damage to structures. Debris can include fragments of buildings, equipment, and other materials that are propelled by these waves and can cause injuries to people and damage to structures. Secondary effects result from the primary effects and include fires, collapse of buildings, and injuries. Damage due to such events causing severe impact can have catastrophic consequences including loss of life, injury, and severe damage to infrastructure.

Apart from protection from severe impact, protection from projectiles is also a requirement in various sectors including, security, police forces and other paramilitary forces. It involves protection of body and eyes against projectiles of various shapes, sizes, and impact velocities. Therefore, it is essential to develop effective and efficient solutions for protection from severe impact and projectiles.

A number of literatures have been published including patent and non-patent documents in said domain.

Traditional materials such as concrete, steel, and masonry have been used as protective barriers
against events of severe impact . A non-patent literature by S.J. Cimpoeru, titled “The Mechanical Metallurgy of Armor Steels”, published in 2016, describes the utility of steel used for armor material or protection from projectiles and discusses the mechanical properties required for optimum performance by steel against impact. Although steel has high strength and toughness, its strength to weight ratio is low. Steel used as impact resistant material has limitations of being heavy, expensive and is prone to failures such as cracking due to various factors.

A patent document CN107842125A titled, “High strength anti-explosion wall with shock-absorbing capacity”, discloses use of high-intensity anti-cracking impervious concrete for protection from severe impact on critical structures. Although such materials provide high impact resistance these materials have limitations, such as being heavy, bulky, and expensive. Moreover, transporting these materials to remote or inaccessible areas can be challenging.

To overcome the limitations in use of traditional materials for protection from severe impact and projectiles, the use of lightweight hybrid composites has been explored as a potential solution. Researchers have been investigating various composite materials, such as fiber-reinforced polymers, ceramic matrix composites, metallic foam composites etc. for protection from severe impact. Although ceramic materials such as alumina, silicon carbide, boron nitride have good mechanical properties these cannot be used in their available form.

Another patent document, EP1098161A2 titled “Use of elements made of fiber-reinforced ceramic composite material” describes the use of a woven or nonwoven reinforced ceramic matrix composite to partially or completely absorb impactive point load. Here, on one hand the hardness of the ceramic matrix of silicon carbide (SiC) is drastically reduced by use of carbon fibers and on the other hand the damage tolerant effect of the fiber reinforcement is weakened by intimate interlocking of fiber bundles and a particulate SiC matrix. In order to obtain the desired protection from severe impact a combination of hardness and damage tolerance the ceramic must be designed much thicker at the expense of the lightweight construction and the dimensioning. Therefore, the draw in use of such composites is the challenge to optimize these materials to achieve the desired properties for protection from severe impact while maintaining their lightweight and cost-effective nature.

Another patent document EP2799412B1 titled, “Monolithic ceramics with fabric mesh reinforcement”, describes a ceramic material and a reinforcement formed therein in the form of a fabric grid for protection from severe impact. The fabric grid is formed of fiber roving placed at specific intervals. However, this material has a drawback that the efficiency and effectiveness achieved in terms of hardness, strength and impact resistance required for protection from severe impact and projectiles are not satisfactory.

Therefore, there is a sizable drawback in the state of the art implying that there is a need to develop a high impact resistant hybrid composite that offers effective protection from severe impact and projectiles and that while being lightweight, cost-effective, easy to transport, capable of minimizing the impact of events of severe impact and preventing or reducing the damages caused by them, has significant applications in various fields including security, aviation, space, and civilian infrastructure.

OBJECT OF THE INVENTION
In order to overcome the shortcomings in the existing state of the art the main object of the present invention is to provide a hybrid composite material with high impact resistance that can provide protection from severe impact to buildings, vehicles, and other structures.

Yet another object of the present invention is to provide a hybrid composite material with high impact resistance that can provide protection from projectiles in the form of body armor, vehicle armor etc.

Yet another object of the present invention is to provide a hybrid composite material with high impact resistance for protection from severe impact and projectiles that is light weight and compact.

Yet another object of the present invention is to provide a hybrid composite material with high impact resistance for protection from severe impact and projectiles protection that is cost effective and easy to transport to remote or inaccessible areas.

Yet another object of the present invention is to provide a hybrid composite material that is optimized for protection from severe impact and projectiles while maintaining lightweight and cost effectiveness.

Yet another object of the present invention is to provide a hybrid composite material having high strength to weight ratio and energy absorption properties that provides effective protection from severe impact and projectiles

Yet another object of the present invention is to provide a hybrid composite material that enhances the safety of workers and equipment in the vicinity of events causing severe impact and can reduce the impact on critical infrastructure.

Yet another object of the present invention is to provide a hybrid composite material with high impact resistance that is easy to fabricate and is versatile in application.

Yet another object of the present invention is to provide a method of fabrication of hybrid composite material with high impact resistance that can provide protection from severe impact to buildings, vehicles, and other structures.

Yet another object of the present invention is to provide a method of fabrication of hybrid composite material with high impact resistance that can provide ballistic protection from projectiles in the form of body protective wear, vehicle protective wear etc.

SUMMARY OF THE INVENTION
Accordingly, the present invention discloses a hybrid composite material with high impact resistance and a method of fabrication thereof that can provide protection from severe impact and projectiles to buildings, vehicles, and other structures.

The present invention provides a lightweight hybrid composite material with high impact resistance that can provide protection from severe impact and projectiles for domains such mining industry, aviation, space, civil infrastructures, oil and gas industry etc. This lightweight composite material for protection from severe impact and projectiles meets the required specifications as set by the STANAG 4569 standards as well as pre-existing norms at Terminal Ballistic Research Laboratory (TBRL), India .

The present invention is disclosed below with a non-limiting example. The invention provides a hybrid composite material that has a sandwich structure, consisting of a lightweight core material between two layers or face sheets of specific materials. The core material is in the form of a honeycomb panel that is lightweight in nature and is made of a structurally strong material with high strength to weight ratio such as a metal or metal alloys to include aluminium and aluminium alloys. This honeycomb panel acts as a sacrificial material that absorbs and dissipates energy from events of severe impact, thereby reducing the damage caused to the surrounding structures. This panel may be prepared by bonding together lightweight foil sheets of the material in a honeycomb configuration by bonding processes such as by using an adhesive material. The resulting structure has a high strength-to-weight ratio and is resistant to fire, corrosion, and moisture making it suitable for use in harsh environments.

The two face sheets or the two layers of specific material are bonded to the honeycomb panel. In a non-limiting example of the present invention the layer that is facing the impact may be composed of a lightweight composite material having high strength to weight ratio such as ceramic composites including but not limited to Silicon carbide plates, Reaction bonded silicon carbide plates etc. These materials may be in the form of plates or tiles of various shapes and may be used in single or multiple layers in the present invention. These materials have exceptional hardness and resistance to abrasion, corrosion and extreme temperatures. They also have strength and ability to withstand high-velocity impacts and are hence suitable for protection from severe impact and projectiles. Due to their ability to be produced with a high level of precision and complexity these materials have versatile application.

The other face sheet that acts as a backing plate or back panel for protection from severe impact or projectiles protective hybrid composite material comprises of a thermoplastic material such as but not limited to thermoplastics from the family of polyaryl ether ketones (PAEK) such as polyether ketone ketone (PEKK), polyether ether ketone (PEEK), Polyether ketone (PEK), polyether Imide (PEI) etc. This thermoplastic polymer material may be reinforced with fibers including but not limited to synthetic fibers such as para aramid fibers to form the thermoplastic composite material as the backing plate or back panel The fibers used may be in the form of amorphous, woven or knitted into fabrics. The fibers used in the backing plate composite have exceptional properties including but not limited to high tensile strength, durability, thermal stability, low elongation-to-break ratio, high modulus of elasticity and are highly resistant to abrasion, chemicals, and UV radiation.

The thermoplastic material used for the composite backing plate or back panel is a high-performance thermoplastic polymer. Thermoplastic may be semicrystalline and has various exceptional properties including mechanical, thermal, and chemical properties. This material is highly resistant to flame and smoke, making it suitable for impact resistance. Thermoplastic material may be in various forms including but not limited to films for the fabrication of high performance thermoplastic composite backing plate or back panel. In a non-limiting example, the composite material comprises of multiple layers of fiber fabric and the thermoplastic polymer films stacked and bonded to form the thermoplastic composite backing plate or back panel.
The structure may be configured as a sandwich panel with the various layers or as a combination of layers without the honeycomb panel. The layers of the composite material are bonded together using adhesives. Various types of adhesives can be used selected from a group of high temperature epoxy adhesive, polyimide adhesive including but not limited to room curing 2-component epoxy adhesive the components of which are mixed together in specific proportions to form a strong and durable bond in a relatively short period of time. The adhesive may comprise of a resin and a hardener and once mixed forms a strong bond that is resistant to impact, heat, water and chemicals. The adhesive has various desirable properties such as less working and curing time, high strength, durability etc. Due to its versatility, it can be used to bond a wide range of materials, including those with different coefficients of thermal expansion, and can also be used in high-stress and high-temperature applications. It has exceptional gap-filling properties, which makes it ideal for bonding irregular or uneven surfaces. These adhesives can be formulated to have different viscosities thus allowing for precise application and control over the bonding process.

The invention provides for a method of fabrication of the composite for protection from severe impact and projectiles that includes but is not limited to autoclaving, vacuum bagging etc. of thermoplastic composite layer, fabrication of honeycomb panel, assembly of layer facing severe impact and joining or bonding of these various layers in different configurations as per the application requirements. The method of joining or bonding of these layers may include surface preparation , cleaning and application of adhesives, curing etc. The method may include provision of a frame of material such as metal with a confining covering sheet selected from group comprising of polycarbonate covering , polymethyl methacrylate covering around the perimeter of the hybrid composite to ensure confinement of the specific layers such as ceramic tiles. Flexible material such as Elastomer sheet for packing purpose , Packaging foam material etc. might be utilized for tight packing inside the confinement frame.

The material of the invention has the potential to be used in a range of applications, including the protection from severe impact and projectiles of critical buildings, vehicles, and other structures to include mobile, portable, and air-borne systems. The hybrid composite sandwich panels of the invention can be used to construct walls, floors, and ceilings of buildings or structures from severe impact.

Accordingly, the present invention discloses a cost effective, portable, efficient, versatile, lightweight hybrid composite material with high impact resistance and a method of fabrication thereof that can provide effective protection from severe impact and projectiles to buildings, vehicles, and other structures while enhancing the safety of humans and equipment.

BRIEF DESCRIPTION OF DRAWINGS
Figure 1 displays the schematic representation of the hybrid composite material with high impact resistance for protection from severe impact (C1).
Figure 2 displays schematic representation of Vacuum Bagging (V).
Figure 3 displays the autoclave curing cycle.
Figure 4 displays the ceramic tiles layering design for front panel of hybrid composite material for protection from severe impact (C1) wherein 4 (a) depicts configuration for odd numbered. layers (C11C1) and 4 (b) depicts configuration for even numbered layers (C11C2).
Figure 5 displays (a) high temperature thermoplastic polymer film (C13CP/ C22CP) and (b) synthetic fiber or para aramid fabric (C13CF/ C22CF).
Figure 6 displays the thermoplastic (ALKEX/PEKK) composite (C13C) bonded with Honeycomb panel (C12H, of Aluminium).
Figure 7 displays the hybrid composite for high impact resistance for protection from severe impact ( C1) after fabrication.
Figure 8 displays the ceramic tiles layering design for front panel of hybrid composite for protection from projectiles (C2) wherein 8 (a) depicts configuration for odd numbered layers (C21C1) and 8 (b) depicts configuration for even numbered layers (C21C2).
Figure 9 displays the thermoplastic (ALKEX/PEKK) composite ( C22C) bonded with layered hexagonal lightweight ceramic composite (C21C) tiles.
Figure 10 displays the cross sectional view of the hybrid composite for protection from projectiles (C2)
Figure 11 displays the hybrid composite for protection from projectiles (C2) after fabrication wherein 11 (a) depicts front panel view and 11 (b) depicts back panel view.
Figure 12 displays the stress strain graph of PEK film.
Figure 13 displays the schematic representation of alternative stacking of three layers of thermoplastic polymer (C13CP/ C22CP) films and single layer of synthetic fiber fabric (C13CF/ C22CF) for good consolidation.
Figure 14 displays the picture of thermoplastic composite (C13C/ C22C) after fabrication.

DETAILED DESCRIPTION OF THE INVENTION WITH ILLUSTRATIONS AND EXAMPLES
While the invention has been disclosed with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made, and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from its scope.

Throughout the specification and claims, the following terms take the meanings explicitly associated herein unless the context clearly dictates otherwise. The meaning of “a”, “an”, and “the” include plural references. Additionally, a reference to the singular includes a reference to the plural unless otherwise stated or inconsistent with the disclosure herein.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure belongs. The system, methods, and examples provided herein are only illustrative and not intended to be limiting.
The abbreviations used in the invention are represented in Table 1 as below:
Table 1: Legend of abbreviations
S.no. Particulars Legend
1 Polyether ketone ketone PEKK
2 Polyether ketone PEK
2 Polyaryl ether ketones PAEK
3 Silicon carbide SiC
4 Reaction bonded silicon carbide RBSiC
5 Standardization Agreement STANAG
6 North Atlantic Treaty Organization NATO
7 Improvised explosive device IED
8 Terminal Ballistic Research Laboratory TBRL
9 Trinitrotoluene TNT
10 Polyether Imide PEI
11 Polyether ether ketone PEEK
Some of the technical terms used in the specification are elaborated as below:
Impact resistance – It is defined as the ability of a material to resist permanent deformation caused by high force or shock applied to it over an extremely short period of time. In this specification the impact resistance relates to resistance to severe impact due to events.
Severe impact - Impact caused when an event occurs with a sudden release of significant amount of energy, resulting in shock waves. Such events with severe impact can be caused by various sources, including industrial accidents, natural disasters such as volcanic eruptions or earthquakes, and intentional acts of violence such as terrorist attacks. The effects of the event causing severe impact can be classified into two categories, primary and secondary effects. The primary effects of such events include direct effects of the events of severe impact to include shock waves, thermal radiation, and debris. Secondary effects refer to the effects that result from the primary effects, such as fires, collapse of buildings, and injuries.
Projectile – A projectile is an object that is propelled by the application of an external force and then moves freely under the influence of gravity and air resistance.
Impact due to projectiles - Impact that is a high velocity impact caused by a small mass object, analogous to runway debris or objects flying at high velocity like projectiles etc.
Structure- A structure is an object that is required to be protected from effects of severe impact or effect due to projectiles. The structure can be a building, vehicle, equipment, installation, high value assets, critical infrastructures, etc.
Exterior (E) - The side or face of a hybrid composite for impact resistance that is away from the structure that is required to be protected by the composite and is likely to face the events causing severe impact or the effects due to projectiles.
Interior (I) - The side or face of a hybrid composite for impact resistance that is towards the structure that is required to be protected by the composite and is not likely to face the events causing severe impact or projectiles.
Armored steel - Armor also written as armored steel, known as ballistic protection steel or simply protection steel, is a steel that is utilized for the purpose of protection against an external threat in the form of incoming projectiles or objects causing severe impact.
Impact resistant hybrid composite – Hybrid composites are materials made up of two or more distinct materials that, when combined, create a material with improved properties compared to individual components. Composites that provide protection against events of severe impact are called impact resistant hybrid composites or hybrid composites or composites in this specification.
Honeycomb – Honeycomb assemblies are natural or man-made structures that have the geometry of a honeycomb to allow the minimization of the amount of used material to reach minimal weight and minimal material cost. The geometry of honeycomb structures can vary widely but the common feature of all such structures is an array of hollow cells formed between thin vertical walls. The cells are often columnar and hexagonal in shape. A honeycomb shaped structure provides a material with minimal density and relatively high out-of-plane compression properties and out-of-plane shear properties.
Honeycomb core for sandwich panel- An assembly of a material with honeycomb configuration can act as a core material between two face sheets of material and together they form a honeycomb sandwich panel.
Material- A material is a substance or a mixture of substances that can be used for making or doing something. The material as denoted in this specification can be chosen from a wide range of substances to include metals, alloys, non-metals, thermoplastics, plastics, glass etc.
Thermoplastic polymer – A thermoplastic polymer also known as thermosoftening plastic, is a form of plastic polymer that is pliable or moldable at a certain high temperature and solidifies when cooled. Such polymers can be very broadly classified as amorphous or crystalline. Thermoplastic polymers have linear and branched structures they soften when heated and harden when cooled. High performance thermoplastic polymers are thermoplastics that have better properties such as being extremely resistant to temperature and chemicals, hydrolysis, halogen-free and resistant to UV and gamma radiation. They also have very good dielectric strength and excellent mechanical properties.
Autoclaving - Autoclaving or autoclave processing is a manufacturing technique that is commonly used in the aerospace, automotive, and composites industries for the production of high-performance materials such as carbon fiber composites. Autoclave processing involves the use of an autoclave, which is a large pressure vessel that is used to subject the material to high temperature and pressure conditions in order to cure and bond the material.
Vacuum bagging – Vacuum bagging is a common process used in the autoclave manufacturing of composite materials to improve the consolidation and quality of the finished product. The process involves placing the material in a vacuum bag and drawing out the air to compress the layers together and remove any trapped air.
Para Aramid Fiber – Para-aramid fibers are a class of high performance synthetic fibers that are known for their exceptional strength, durability, and thermal stability that are highly resistant to abrasion, chemicals, and UV radiation. They are made from aromatic polyamide, which has a highly ordered molecular structure that gives them unique mechanical properties.
Polyether ketone ketone (PEKK) – Polyether ketone ketone or PEKK is a high-performance thermoplastic polymer that belongs to the family of Polyarylether ketones (PAEKs). It is a semi-crystalline polymer that exhibits excellent mechanical, thermal, and chemical properties, making it a suitable material for a wide range of applications including for protection from severe impact and projectiles .
Silicon carbide – Silicon carbide (SiC), also known as carborundum, is a hard chemical compound containing silicon and carbon. It occurs in nature as the extremely rare mineral moissanite but has been mass-produced as a powder and crystal since 1893 for use as an abrasive. Grains of silicon carbide can be bonded together by sintering to form very hard ceramics that are widely used in applications requiring high endurance, such as car brakes, car clutches and ceramic plates in vests for protection from projectiles.
Reaction bonded silicon carbide (RBSiC) – Reaction bonded silicon carbide, also known as siliconized silicon carbide or SiSiC, is a type of silicon carbide that is manufactured by a chemical reaction between porous carbon or graphite with molten silicon. Due to the left over traces of silicon, reaction bonded silicon carbide is often referred to as siliconized silicon carbide, or its abbreviation SiSiC.
Two-component epoxy adhesive – A two-component epoxy adhesive is a type of adhesive that consists of two components, a resin and a hardener, that are mixed together in specific proportions to form a strong and durable bond. A room temperature curing two-component epoxy adhesive is a type of adhesive designed to cure at room temperature, without the need for additional heat or curing agents. Due to their properties of high strength, durability, and resistance to chemicals, water, and temperature extremes etc. they are widely used in a variety of industrial applications, such as bonding metals, plastics, ceramics, and composites, as well as in construction, automotive, and aerospace industries.

STANAG - STANAG 4569 is a NATO standardization agreement that sets the minimum protection levels required for military vehicles to withstand different types of threats in a combat environment. The standard consists of four volumes, each focused on a specific aspect of vehicle protection. Volumes 1,2,3 relate to kinetic energy threats, mine threats, IED threats respectively.

The reference numerals used in the present invention are tabulated below in Table 2.
Table 2: Legend of Reference numerals
Ser no. Item description Reference numerals
1 Hybrid composite material with high impact resistance/hybrid composite C
Hybrid composite material for protection from severe impact C1
Hybrid composite material for protection from projectiles C2
Exterior E
Interior I
2 Hybrid Composite material for protection from severe impact C1
a Front /Impact facing panel C11
Lightweight ceramic composite C11C
Layer of lightweight ceramic composite C11CL
Configuration 1 C11C1
Configuration 2 C11C2
b Lightweight core material panel C12
honeycomb panel C12H
foil sheets C12HF
c Back panel or Backing plate C13
Thermoplastic composite C13C
Thermoplastic Polymer C13CP
Synthetic fiber/fabric C13CF
2. Hybrid composite material for protection from projectiles C2
a Front panel C21
Lightweight ceramic composite C21C
Layer of lightweight ceramic composite C21CL
Configuration 1 C21C1
Configuration 2 C21C2
b Back panel C22
Thermoplastic Composite C22C
Fabric/ synthetic fiber C22CF
Thermoplastic Polymer C22CP
c Lightweight material frame C24
d Confining sheet C25
e Elastomer sheet for packing purpose C26
f Packaging foam material C27
3 Adhesive A
4 Vacuum bagging V
Vacuum valve V1
Thermocouple V2
Sealant V3
Vacuum bagging film V4
Breather layer V5
Perforated film V6
Stacked layers V7
Release film V8
Surface plate V9

In the domain of protection or impact resistance due to severe impact or projectiles events, the use of hybrid composites has significant potential due to their high strength-to-weight ratio and excellent energy absorption properties. In order to achieve the desired properties for protection from severe impact and projectiles these materials are required to be optimized for impact resistance while maintaining their lightweight and cost-effective nature.

The present invention discloses hybrid composite material with high impact resistance (C) and method of fabrication thereof that can provide protection from severe impact (C1) and projectiles (C2) to living and non-living objects to include , vehicles, equipment, critical infrastructures and other such high value assets using a simple, easy to fabricate, portable and effective material at affordable cost.

The material lightweight impact resistant hybrid composites (C) have the potential to be used for protection of a wide range of structures including buildings, vehicles, equipment and other such high value assets, critical infrastructures etc., from the severe impact of events or from projectiles. These materials offer superior protection to structures against severe impact or from projectiles, enhance the safety of people and equipment, and can reduce the impact of such events on critical infrastructure. The material has a wide range of potential applications across various industries and sectors including mining industry, aviation, space, civil infrastructures, oil and gas industry etc.

Hybrid composite material with high impact resistance (C) can be fabricated either to provide protection from severe impact (C1) or to provide protection from projectiles (C2). The hybrid composite material for protection from severe impact (C1) is a simple, easy to fabricate, portable and effective material at affordable cost. The said hybrid composite material (C1) is fabricated in the form of a sandwich construct consisting of:
- A front panel (C11) or layer or panel that is facing the severe impact and is on the exterior (E) of the hybrid composite material (C1) that is deployed on the structure to be protected is composed of highly specific material such as lightweight ceramic composites (C11C). The lightweight ceramic composite (C11C) of front panel is in the form of layers of lightweight ceramic composites (C11CL) ranging in numbers from one to ten, preferably four.
- A back panel or layer or panel that acts as a backing plate (C13), on the interior (I) of the hybrid composite material (C1) that is deployed on the structure to be protected, comprises of highly specific material like a thermoplastic composite (C13C) made from material such as high-performance thermoplastics from the family of polyaryl ether ketones (PAEK) etc. that may be reinforced with fiber.
- A lightweight core material (C12) is deployed between the exterior (E) and the interior (I) of said hybrid composite material (C1) giving a sandwich construct or configuration using an adhesive (A). The lightweight core material (C12) is in the form of a honeycomb panel (C12H).
The front panel (C11) is prepared from lightweight ceramic composites (C11C) that have high resistance to penetration, exceptional hardness, ability to withstand high-velocity impacts, high strength to weight ratio and high resistance to abrasion, corrosion, and extreme temperatures, such as Silicon carbide ceramic composites. The layers (C11CL) of said lightweight ceramic composites (C11C) of said front panel (C11) of said hybrid composite material (C1) are stacked and bonded with each other using said adhesive (A). The material of lightweight ceramic composite (C11C) is selected from group of silicon carbides, reaction bonded silicon carbide, sintered silicon carbides, alumina, alumina silica of which silicon carbides provide excellent protection.

The panel of lightweight core material (C12) is prepared from a lightweight material that is resistant to fire, corrosion and moisture, has high strength to weight ratio of 2 to 3 times that of protection steel such as armored steel and is capable of being fabricated into a honeycomb configuration thus enabling absorption and dissipation of energy from severe impact. This material is fabricated into a honeycomb panel (C12H) configuration and is placed between the front panel (C11) of lightweight ceramic composites (C11C) and the back panel (C13) of thermoplastic composite (C13C) in a sandwich configuration using adhesive (A).

The back panel (C13) is made of thermoplastic composite (C13C) comprising of
- Thermoplastic polymer (C13CP) material from the family of polyaryl ether ketones (PAEK) that has high strength, toughness, stiffness, fatigue resistance, thermal stability and impact resistance and is capable of being formed into films. The thermoplastic polymers (C13CP) are selected from group of high-performance thermoplastic polymers comprising of polyether ketone ketone (PEKK), polyether ketone (PEK), polyether ether ketone PEEK, polyether Imide (PEI).
- Synthetic fiber (C13CF) that has high strength, durability, thermal stability, high resistance to abrasion, chemicals, and UV radiation and low elongation-to-break ratio to function as reinforcing phase for the said thermoplastic polymer (C13CP) and is capable of being knitted or woven in the form of fabrics.

The thermoplastic composite (C13C) has configuration such that layers of films of the thermoplastic polymer (C13CP) are stacked alternately with layers of fabric of synthetic fiber (C13CF) and is fabricated using processes of vacuum bagging (V) followed by autoclaving etc., to obtain the thermoplastic composite (C13C).

The panels of the hybrid composite material for protection from severe impact (C1) are assembled and bonded in a way that the panel of lightweight core material (C12) is sandwiched between the front panel (C11) and the back panel (C13) and is bonded together in this construct using adhesive (A). The adhesive (A) that is utilized to bond the various panels of the hybrid composite material for protection from severe impact (C1) may be selected from various types of adhesives that have high strength, durability, versatility and resistance to chemicals, water, and temperature extremes, that are capable of being cured at room temperature and may be selected from group of high temperature epoxy adhesive, polyimide adhesive to include room curing 2-component epoxy adhesive.

The hybrid composite material for protection from severe impact (C1) thus provides impact resistance and protection to a wide range of structures including buildings, vehicles, equipment and other such high value assets, critical infrastructures etc., from the severe impact of events. The said hybrid composite is easy to fabricate and provides a simple, portable and effective solution for protection from severe impact at affordable cost.

The hybrid composite material for protection from projectiles (C2) is fabricated to have a structure or configuration with a combination of layers, consisting of:
- The front panel (C21) or layer that is facing the projectile is deployed on the exterior (E) of the said material that is deployed on the structure to be protected, is composed of a lightweight composite material such as lightweight ceramic composites (C21C). The ceramic composites are in the form of layers ranging in number from one to ten, preferably four.
- The other face sheet that acts as a backing plate or back layer or a back panel (C22) for the hybrid composite material (C2) comprises of a thermoplastic composite (C22C) made of thermoplastic material such as thermoplastics from the family of polyaryl ether ketones (PAEK) etc. and may be reinforced with fibers. This panel is deployed in the interior (I) of the said hybrid composite material (C2). The thermoplastic polymers (C22CP) are selected from group of high-performance thermoplastic polymers comprising of polyether ketone ketone (PEKK), polyether ketone (PEK), polyether ether ketone PEEK, polyether Imide (PEI).

The front panel (C21) is prepared from lightweight ceramic composites (C21C) that have high resistance to penetration, exceptional hardness, ability to withstand high-velocity impacts, high strength to weight ratio and high resistance to abrasion, corrosion, and extreme temperatures such as Silicon carbide ceramic composites. The panel of ceramic composites (C21C) may be fabricated as single layered or multilayered with layers stacked and bonded with each other using adhesive (A).

The back panel (C22) is made of thermoplastic composite (C22C) comprising of
- Thermoplastic polymer (C22CP) from the family of polyaryl ether ketones (PAEK) with high strength, toughness, stiffness, fatigue resistance, thermal stability and impact resistance and is capable of being formed into films. The thermoplastic polymers (C13CP) are selected from group of high-performance thermoplastic polymers comprising of polyether ketone ketone (PEKK), polyether ketone (PEK), polyether ether ketone PEEK, polyether Imide (PEI).
- Synthetic fiber (C22CF) with high strength, durability, thermal stability, high resistance to abrasion, chemicals, and UV radiation and low elongation-to-break ratio to act as reinforcing phase for the said thermoplastic polymer (C22CP). This fiber may be knitted or woven in the form of fabrics.

The appearance of high temperature thermoplastic polymer film (C13CP/C22CP) and synthetic fiber (C13CF/C22CF) are illustrated in Figure 5 (a) and (b) respectively. A picture of thermoplastic composite (C13C/ C22C) after fabrication is as illustrated in Figure 14.

The back panel (C22) of thermoplastic composite (C22C) is fabricated in a way that layers of films of the thermoplastic polymer (C22CP) are stacked alternately with layers of fabric of synthetic fiber (C22CF) and made using process of vacuum bagging (V) followed by autoclaving etc. to obtain the thermoplastic composite (C22C).

The panels of hybrid composite material for protection from projectiles (C2) are assembled in a way that the front panel (C21) and the back panel (C22) are bonded together to form said hybrid composite using adhesive (A).
The layers of lightweight ceramic composite (C21C) are confined by providing a confining sheet (C25) selected from group comprising of polycarbonate covering, polymethyl methacrylate covering over the exposed surface of front panel (C21) and providing lightweight material frame (C24) along with packing material (C26) to include elastomer sheet for packing purpose (C26) such as silicone rubber sheet and packaging foam material (C27) such as extended polyethylene foam for tight packing around the perimeter of said hybrid composite for protection from projectiles (C2) to ensure tight packing.

The adhesive (A) utilized to bond the various panels of the hybrid composite material for protection from projectiles (C2) may be selected from various types of adhesives (A) that have high strength, durability, versatility and resistance to chemicals, water, and temperature extremes and is capable of being cured at room temperature and may be selected from group of high temperature epoxy adhesive, polyimide adhesive to include room curing 2- component epoxy adhesive.

The hybrid composite material for protection from projectiles (C2) thereby provides impact resistance and protection to humans, vehicles, equipment and other such high value assets, critical infrastructures etc., from the impact of projectiles using a simple, easy to fabricate, portable and effective material at affordable cost.

The lightweight ceramic composite (C21C) of the hybrid composite material for protection from projectiles (C2) may be in the form of flat tiles in each layer of the lightweight ceramic composite (C21CL) that are arranged and bonded laterally by the side in a compact and economic way to form each layer of the lightweight ceramic composite (C21CL).The layers of lightweight ceramic composite (C21C) are configured and bonded in a staggered approach such as double strap joint etc. so as to ensure the joining interface of the preceding layer is completely covered by the following layer (refer Figure 8 (a) and (b)).

The thermoplastic polymer (C22CP) of the hybrid composite material for protection from projectiles (C2) for preparing back panel (C22) is selected from group of high performance thermoplastic polymers comprising of polyether ketone ketone (PEKK), polyether ketone (PEK) , polyether ether ketone PEEK , polyether Imide (PEI).

The hybrid composite material for protection from projectiles (C2) provides impact resistance and protection to living and non-living objects to include , vehicles, equipment, critical infrastructures and other such high value assets from the impact of projectiles using a simple, easy to fabricate, portable and effective material at affordable cost.

The lightweight hybrid composite material for impact resistance for protection from severe impact (C1) and for protection from projectiles (C2) of the present invention also meets the required specifications as set by the STANAG 4569 standards as well as pre-existing norms at Terminal Ballistic Research Laboratory (TBRL), India. Accordingly, the material of the present invention is effective for STANAG Level III and STANAG Level IV IED protection from severe impact and STANAG Level III Bullet Protection.

As per an embodiment of the present invention, the various materials used for preparation of hybrid composite material for protection from severe impact (C1) and protection from projectiles (C2) and the method of their fabrication are described in the following paragraphs.

The back panel (C13/C22) of hybrid composite material for protection from severe impact (C1) or protection from projectiles (C2) is made of thermoplastic composites (C13C/ C22C) that are in turn made of high performance thermoplastic polymers such as PEK, PEEK, PEI and PEKK (C13CP/ C22CP) reinforced with synthetic fibers (C13CF/ C22CF). Normally the synthetic fiber used to reinforce thermoplastic polymers are selected from high performance para aramid fiber, glass fiber, meta aramid fiber, carbon fiber polyacrylonitrile (PAN), basalt, , polyethylene terephthalate (PET), or polypropylene fibers (PP) as most of these fibers depending on their respective properties offer good strength and stiffness, impact resistance, chemical resistance, and thermal stability.

.As per an embodiment of the present invention the synthetic fiber (C13CF/ C22CF) for preparing thermoplastic composite (C13C/ C22C) of back panel (C13/ C22) is selected from group of high performance para aramid fiber, meta aramid fiber etc. Para-aramid fibers are a class of high performance synthetic fibers that have unique properties making them ideal for high-performance applications. They have a very high tensile strength, which makes them resistant to tearing and punctures. They also have a low elongation-to-break ratio and hence they do not stretch significantly before breaking. Additionally, para-aramid fibers are highly resistant to abrasion, chemicals, and UV radiation.

Another key feature of para-aramid fibers is their exceptional thermal stability. They have a melting point of around 500°C, that is much higher than most other synthetic fibers. They also have a low thermal shrinkage, which means that they do not deform significantly when exposed to high temperatures. These properties make para-aramid fibers ideal for high-temperature applications such as fire-resistant clothing and hot gas filtration systems. Generally, para-aramid fibers can withstand high temperatures of up to 200°C to 400°C. Therefore, they are ideally suited to be used as backing plate or back face layer in protection from severe impact or protection from projectiles .

In a specific embodiment, the present invention uses ALKEX produced by Hyosung Advanced Materials. Alkex is an example of high-strength para-aramid fiber made from an aromatic polyamide polymer that has a highly ordered molecular structure, that gives the fiber its exceptional strength and durability. One of the key features of ALKEX is its high tensile strength. The fiber has a tensile strength of up to 3.6 GPa, that is about five times stronger than steel of the same weight. This makes ALKEX an ideal material for high-performance applications that require exceptional strength and durability, such as material for protection from severe impact or protection from projectiles to buildings and other structures, body armor, helmets for protection from projectiles , and aerospace components.

Another important feature of ALKEX is its high modulus of elasticity, which is the measure of a material's resistance to deformation under stress. ALKEX has a modulus of elasticity of up to 130 GPa, which is significantly higher than most other synthetic fibers. This makes ALKEX an ideal material for applications where stiffness and rigidity are required, such as structural composites and reinforcement materials.
ALKEX also has excellent resistance to abrasion, chemicals, and UV radiation, that makes it suitable for applications in harsh environments. It also has a low thermal shrinkage, that means it does not deform significantly when exposed to high temperatures. These properties make ALKEX an ideal material for applications of protection from severe impact or for protection from projectiles, hot gas filtration systems and protective clothing for firefighters and other first responders.

ALKEX is produced using a proprietary spinning process by the manufacturer that results in a highly uniform fiber structure. The fibers are then treated with various chemicals to improve their mechanical properties and enhance their adhesion to other materials. The treated fibers can be woven or knitted into fabrics or used to reinforce thermosets or thermoplastic composites.

As per an embodiment of the present invention, ALKEX fiber has been utilized as the reinforcement phase for the high performance thermoplastic composite (C13C) for hybrid composite material for protection from severe impact (C1) or the thermoplastic composite (C22C) for hybrid composite material for protection from projectiles (C2) of the impact resistant hybrid composite (C). The phrase ‘high performance thermoplastic composite’ refers to a group of thermoplastics that offer excellent temperature resistance along with exceptional mechanical performance.

The material utilized for preparing the back panel of the hybrid composite material for protection from severe impact (C1) or protection from projectiles (C2) are thermoplastic polymers that belong to the family of polyarylether ketones (PAEK) that have high strength, toughness, stiffness, fatigue resistance, thermal stability and impact resistance. Some of the polymers from this family that may be used for fabricating the thermoplastic composites are selected from group of high performance thermoplastic polymers comprising of polyether ether ketone PEEK are polyether ketone ketone (PEKK), polyether ketone (PEK) , polyether imide (PEI) etc.

Polyether ketone ketone or PEKK, a thermoplastic polymer that belongs to the family of polyarylether ketones (PAEKs), is a high-performance thermoplastic polymer and has excellent impact properties, making it ideal for applications that require high strength and toughness. Its unique molecular structure, that combines both crystalline and amorphous regions, contributes to its exceptional mechanical properties, including high tensile strength, stiffness, and fatigue resistance. Therefore, the material is ideally suitable for use where impact resistance is critical such as aerospace industry wherein it is used to manufacture components including brackets, clips, and fittings that require high strength and toughness to withstand the stresses of flight. PEKK is also highly resistant to flame and smoke, making it an ideal material for aerospace and applications. It has a low flammability rating, and it produces low levels of smoke and toxic gases when exposed to fire. Therefore, this thermoplastic polymer material is highly suitable for preparing hybrid composite for protection from severe impact (C1) and projectiles (C2).

As per an embodiment, an example of a material that belongs to the family of polyether ketone ketone (PEKK) polymers, is GAPEKK 3200 and is manufactured by Gharda Chemicals Limited. It is a semi-crystalline polymer that exhibits excellent mechanical, thermal, and chemical properties ideally suitable for protection from severe impact or protection from projectiles. The thermoplastic polymer (C13CP) was procured in the form of a film for the fabrication of thermoplastic composite panel (C13C or C22C) or plate.

Ceramic composite materials are versatile materials that have a wide range of applications in various sectors. They possess favorable features that make them useful in various areas such as aerospace, automotive, construction, sports, and biomedical. Ceramic composites show extraordinary structural and mechanical features like high strength-to-weight ratio, chemical resistance, fire, corrosion, and wear. The desirable characteristics of ceramic matrix composites include high-temperature stability, high thermal shock resistance, high hardness, high corrosion resistance, light weight, non-magnetic and non-conductive properties, and versatility in providing unique engineering solutions.

Some examples of lightweight ceramic composites utilized in the embodiments of the present invention are selected from group of silicon carbides such as sintered silicon carbide, reaction bonded silicon carbide that exhibit high impact resistance can be utilized in various domains such as aerospace for protection from severe impact or protection from projectiles.

Lightweight ceramic composite material such as silicon carbides are ideally suited to be used in the preparation of layer facing severe impact (C11 or C21) of the impact resistant hybrid composite (C). Silicon carbide plates are ceramic plates prepared from the composite material of silicon carbide (SiC) and a binding agent. Lightweight ceramic composite (C11C/ C21C) material such as silicon plates are known for their exceptional hardness, high strength, and resistance to abrasion, corrosion, and extreme temperatures. Silicon carbide plates have a wide range of applications, including in the aerospace and semiconductor industries. They are commonly used in the production of protection plates from projectiles due to their superior strength and ability to withstand high-velocity impacts.

As per an embodiment of the present invention a variety of the lightweight ceramic (C11C/ C21C) composite material like silicon carbide is reaction bonded silicon carbide (RBSiC) that is a dense and strong ceramic composite that has a high resistance to wear, corrosion, and thermal shock. One of the main advantages of RBSiC is its ability to be produced with a high level of precision and complexity, making it a suitable choice for manufacturing components with intricate geometries and tight tolerances, such as gas turbine components etc.

Another advantage of RBSiC is its excellent thermal shock resistance, that makes it ideal for high-temperature applications. It can withstand rapid temperature changes without cracking or deteriorating, that is particularly important in applications such as protection from severe impact or protection from projectiles , furnace components and heat exchangers. RBSiC also has a high strength-to-weight ratio, that makes it an ideal choice for structural components that require both strength and light weight, such as in aerospace applications. The silicon carbide plates or tiles used in an embodiment of the present invention are procured from Carborundum Universal Limited, Hosur.

As per an embodiment of the present invention the core material (C12) for protection from severe impact is made of honeycomb panel (C12H) is prepared from a lightweight material that has high strength to weight ratio of 2 to 3 times that of protection steel such as armored steel, that absorbs and dissipates energy from any event of severe impact , is resistant to fire, corrosion, and moisture. The lightweight material is selected from materials such as aluminium, aluminium alloys etc. that can be fabricated into a honeycomb panel (C12H) configuration and is placed between the front panel (C11) of lightweight ceramic composites (C11C) and the back panel (C13) of thermoplastic composite (C13C) in a sandwich configuration using the said adhesive (A). It is fabricated by bonding processes such as adhesive bonding of foil sheets (C12HF) of said lightweight material to form the honeycomb core and further assembled in the form of sandwich panels that comprise of face sheets or skin of same or other material bonded to the honeycomb core on each of its lateral side.

One of the examples of material fabricated as honeycomb panel uses aluminum honeycomb that is a lightweight and strong structural material with high strength to weight ratio, widely used in various industrial applications, including severe impact applications. Aluminum honeycomb acts as a sacrificial material that absorbs and dissipates energy from an event of severe impact, thereby reducing the damage caused to the surrounding structures. The phrase aluminium honeycomb includes honeycomb preparation from alloys of metal aluminium called aluminium alloys.

Aluminum honeycomb structures are typically made by bonding together aluminum foil sheets (C12HF) in a honeycomb configuration using an adhesive material. The resulting structure has a high strength-to-weight ratio, which makes it ideal for use in applications where weight and strength are critical factors.

In severe impact applications, material like aluminum honeycomb structures can be used in the form of sandwich panels, which consist of two face sheets or skin of material bonded to the material like aluminum honeycomb core. These sandwich panels can be used to construct walls, floors, and ceilings of impact -resistant buildings and structures.

The key advantage of using aluminium honeycomb in severe impact applications is its ability to absorb and dissipate energy from events of severe impact. When an event of severe impact occurs, the honeycomb structure deforms and crushes in a controlled manner, thereby absorbing the energy from the event of severe impact . This reduces the severe impact pressure and shock waves transmitted to the surrounding structures, thereby minimizing the damage caused.
Aluminium honeycomb structures are also resistant to fire, corrosion, and moisture, which makes them suitable for use in harsh environments. They are easy to install, maintain, and repair, which makes them a cost-effective solution for impact -resistant construction. Overall, aluminium honeycomb is a highly effective material for severe impact applications due to its high strength-to-weight ratio, energy-absorbing capabilities, and resistance to fire, corrosion, and moisture. It offers a reliable and cost-effective solution for impact -resistant construction in a variety of industrial settings.

As a non-limiting embodiment of the present invention, the aluminium honeycomb panel (C12H) used has been procured from Honylite Private Limited, Noida.

As per an embodiment of the present invention the fabrication of the impact resistant composite uses adhesives for bonding the various layers or panels. A variety of adhesives (A) can be used for the present invention such as high temperature epoxy adhesive, polyimide adhesive etc.

One example of the adhesives that may be used are room temperature curing 2-component epoxy adhesives that are known for their high strength, durability, and resistance to chemicals, water, and temperature extremes. The two – component adhesive used for preparation of hybrid composite for protection from severe impact or projectiles (C1 or C2) consists of two components, a resin and a hardener, which are mixed together in proportions with ratio ranging between 4: 1 to 1: 1 , preferably 2:1 to form a strong and durable bond in a short period of time such as 36 hrs or lesser preferably 24 hrs or lesser and is designed to cure at room temperature, without the need for additional heat or curing agents. Once the two components are mixed together, the adhesive (A) begins to cure, and the bond can reach full strength within a few hours, depending on the specific adhesive formulation.

Another advantage of this type of adhesive is its versatility. It can be used to bond a wide range of materials, including those with different coefficients of thermal expansion, and can also be used in high-stress and high-temperature applications. Room temperature curing 2-component epoxy adhesives are also known for their excellent gap-filling properties, which makes them ideal for bonding irregular or uneven surfaces. They can also be formulated to have different viscosities, which allows for precise application and control over the bonding process.

In a non-limiting example of an adhesive (A) used for fabricating the impact resistant composite material for protection from severe impact or projectiles ( C1 or C2) is Lapox Ultrafix, a high-strength epoxy adhesive, manufactured by Atul Ltd. It is a 2-component epoxy adhesive that comprises of a resin and a hardener mixed in ratio such as 2:1. Once mixed, it forms a strong bond that is resistant to impact, heat, and chemicals. Lapox Ultrafix is ideal for bonding various materials such as metals, alloys, ceramics, glass, concrete, and most plastics. It is commonly used in automotive, construction, and industrial applications due to its excellent bonding properties. Said adhesive has a working time of approximately 20-30 minutes, and it cures completely in lesser than 24 hours at room temperature. Lapox Ultrafix has a strong and durable bond, which makes it suitable for structural applications where high load-bearing capacity is required.

The thermoplastic composite panel (C13C) of hybrid composite material for protection from severe impact (C1) as per the present invention are manufactured using autoclave processing technique. ALKEX fabric reinforced PEKK or ALKEX/PEKK composite is an example of the high performance thermoplastic composites (C13C) used in the composite back panel (C13) of the hybrid composite material for protection from severe impact (C1) of the present invention. The steps involved in the autoclave processing of the thermoplastic composite (such as ALKEX/PEKK composite) are descriptively explained in the following paragraphs. It is to be noted that the specific names used are by way of specific embodiment and should not be seen as limiting .

The material of thermoplastic composite panel (C13C) is first prepared by cutting, shaping, and stacking or layering the various components to create the desired shape and structure. The thermoplastic composite (C13C) of back panel (C13) may be fabricated with layers of thermoplastic polymer (C13CP) and fabric of synthetic fiber (C13CF) stacked alternately keeping their ratio ranging from 4:1 to 1:1 wherein the thermoplastic composite (C13C) has layers of films of the thermoplastic polymer (C13CP) ranging in number from 10 to 200 stacked alternately with layers of fabric of synthetic fiber (C13CF) ranging in number from 10 to 50 to obtain the thermoplastic composite (C13C) with thickness in the range of 5 mm to 70 mm.

In an embodiment of the invention three layers of thermoplastic polymer (C13CP) films may be stacked alternately with one layer of fabric of synthetic fibers (C13CF) for good consolidation to obtain the thermoplastic composite (C13C) keeping the ratio of the two components 3:1 (refer Figure 13). In another embodiment the total number of layers of the thermoplastic polymer (C13CP) films are 21 and the total number of layers of fabric of synthetic fibers (C13CF) are 20 keeping the ratio of the two components 1:1 with thickness in the range of about 8-12 mm of approximately 10 mm.

The vacuum bagging (V) process as applicable to hybrid composite material for protection from severe impact (C1) and projectiles (C2) is briefly described here. The material for thermoplastic composite (C13C/ C22C), the synthetic fiber/ fabrics (C13CF/ C22CF) and the layers of film of the thermoplastic polymer (C13CP, C22CP) that are alternately stacked are subjected to vacuum bagging (V) to improve the consolidation of the layers to obtain the thermoplastic composite (C13C/ C22C) of back panel (C13/ C22 ).

As per an embodiment of this invention the thermoplastic composite (C13C/C22C) panel is obtained by vacuum bagging (V) of said fiber and film stacked layers (V7) utilizing materials from a group of vacuum valve (V1), thermocouple (V2), sealant (V3), vacuum bagging film (V4), breather layer (V5), perforated film (V6), release film (V8), surface plate (V9) etc. for the process of vacuum bagging (V). The configuration of the vacuum bagging (V) setup as described for the present invention is illustrated in Figure 2.

The vacuum bagged layers in the vacuum bag (V) are loaded into autoclave for curing cycle. The autoclave is heated and pressurized to the desired temperature and pressure conditions. The temperature in the range of 250 - 400 0C and pressure in the range of 4-10 bars conditions are carefully controlled and monitored throughout the process to ensure the proper curing of the material.
The vacuum bagged layers material is cured under the high temperature and pressure conditions for a specified period of time in the range of 4 - 8 hrs. The curing process allows the resin to flow and bond the various layers of material together, creating a strong and durable final product. After the curing process is complete, the autoclave is slowly cooled to room temperature to prevent any damage to the material. This cooling process may take several hours or more. The final product of composite panel (C13C or C22C) material is then removed from the autoclave and any excess material trimmed by waterjet cutting. The autoclave cycle followed during the fabrication of composite panel (C13C or C22C) material such as ALKEX/PEKK composite is shown in Figure 3.
The consolidated method of preparation of material for thermoplastic composite (C13C/ C22C) of back panel (C13/ C22) of hybrid composite material with high impact resistance for protection from severe impact (C1) and for protection from projectiles (C2) and the process of autoclaving or curing using autoclaving is described in the following paragraphs.

Films of thermoplastic polymer (C13CP/ C22CP) are prepared by cutting it into strips of desired width in the range of 100 mm to 500 mm and desired length. The fabric of synthetic fiber (C13CF/ C22CF) is prepared by cutting it into desired shape and size for the application purpose desired. A layer of thermoplastic polymer (C13CP/ C22CP) film is prepared by placing the said strips of the thermoplastic polymer (C13CP/ C22CP) side by side laterally to obtain the desired size for desired application purpose. The cut fabrics of synthetic fiber (C13CF/ C22CF) and said layers of thermoplastic polymer (C13CP/ C22CP) film are stacked alternately.

Stacked layers (V7) of the said two materials are placed in a vacuum bag (V) and the layers are vacuum bagged (V) or vacuumed as described previously by drawing out the air to compress the layers together and remove any trapped air. The vacuumed layers of the said two materials are loaded in the vacuum bag (V) into the autoclave for the curing cycle. The autoclave is heated and pressurized to the desired temperature and pressure conditions. Curing is carried out under the desired high temperature and pressure conditions for a specified period of time while keeping the desired temperature and pressure conditions controlled and monitored throughout the process to ensure the proper autoclaving and curing of the vacuumed layers of the two materials to obtain a single autoclaved product. The autoclave is cooled slowly to room temperature after completion of curing process to prevent any damage to the autoclaved product and the autoclaved product is removed from the autoclave and trimmed for any excess material by waterjet cutting.

The said vacuum bagging (V) process of the layers of the two material components of thermoplastic composite (C13C/C22C) of front panel (C11/C21) as applicable to hybrid composite material for protection from severe impact (C1) and projectiles (C2) is described in detail in the following paragraphs.

Thermocouple (V2) is embedded within the stacked layers (V7) of components of thermoplastic composite (C13C/ C22C) for monitoring the temperature. The bagging film/material (V4) of the vacuum bag (V) is pulled tightly against the stacked layers (V7) of components of thermoplastic composite (C13C/ C22C) to ensure good contact and removal of any wrinkles or folds.

The air from the material of stacked layers (V7) of components of thermoplastic composite (C13C/ C22C) placed inside the vacuum bag (V) is removed by using a vacuum pump thus creating a pressure differential between the inside of the bag and the outside, which compresses the layers of the material together and removes any trapped air. Sealing of the vacuum bag (V), after the vacuum is established, by using sealing tapes such as GS Tape and Kapton Tape to prevent any air from leaking back into the bag.

The conditions for autoclaving as described above are provided in the Table 3 below:
Table 3: Conditions of autoclaving
Ser. No. Condition Range of values Value
1 Holding Temperature 250 – 400 °C 310 °C
2 Heating rate 1-5 °C 3 °C
3 Holding time 30 -120 minutes 60 minutes
4 Cooling rate 2- 8 °C 5 °C
5 Pressure 4-10 bars 8 bars

Ceramic tiles that can be used for the purpose of any impact protection are categorized into two shapes: flat tiles and shaped tiles. The flat tiles can take various shapes such as square, hexagonal, or any other shape most commonly used shape being square and hexagonal. Square tiles have the advantage of being easy to manufacture and assemble but may be weaker at the corners. On the other hand, hexagonal tiles do not have right-angled corners, and therefore perform better than square tiles.

The lightweight ceramic composite (C11C/C21C) for preparing the front panel of hybrid composite material for protection from severe impact or from projectiles (C1/C2) are in the form of ceramic flat tiles whose shape is selected from square, hexagonal, any other shape capable of being assembled into layers in a compact manner. An effective shape out of these options is found to be square for C1 and hexagonal for C2. These flat tiles may have lateral dimensions in the range of 30 mm to 100 and thickness in the range of 2 mm to 20 mm, preferably 6 mm.

In an embodiment of the present invention the front panel or impact facing panel layer facing severe impact (C11 or C21) of the hybrid composite material for protection from severe impact (C1), or projectiles (C2) can be fabricated using flat tiles with either a single thick ceramic layer (monolithic) or multiple thin ceramic layers (layered ceramics). Therefore, the number of layers of lightweight ceramic composites (C11 or C21) of the hybrid composite for protection from severe impact (C1) or projectiles (C2) ranges from one to ten.

The use of layered ceramics improves the resistance to penetration during severe impact or impact from projectiles as this structure delays the rise of stress and reduces the peak stress, resulting in improved attenuation of the stress wave. An optimum number of layers is derived for maximizing the penetration resistance as compared to a monolithic ceramic layer.

The ceramic composite panel (C11C) for hybrid composite material for protection from severe impact (C1) can be fabricated with layers in the range of one to ten, in two configurations (such as but not limiting to C11C1 for odd numbered layers and C11C2 for even numbered layers) alternately, to ensure a staggered approach such as double strap joint etc., so that the joining interface of the preceding layer is completely covered by the following layer (refer Figure 4(a) and (b)) to achieve maximum impact resistance. The flat tiles of lightweight ceramic composite (C11C) are bonded laterally by the side using the adhesive (A) preferably the two-component epoxy adhesive in a compact and economic way to form each layer of the lightweight ceramic composite (C11CL). Figure 4(a) depicts the configuration of arrangement of tiles in a layer in odd numbered layers and Figure 4 (b) depicts the configuration of arrangement of tiles in a layer in even numbered layers. The alternate layers of ceramic composites are configured differently to ensure that the ceramic tiles are placed in a staggered approach so that the joining interface of the preceding layer is completely covered by the following layer for strong bonding.

As per an embodiment of the present invention the design configuration for the hybrid composite material with high impact resistance for protection from severe impact (C1) is shown in Figure 1. The hybrid composite material for protection from severe impact (C1) is fabricated and assembled by a method described in the following paragraphs.

The surface of thermoplastic composite (C13C) is prepared by cleaning with cleaning solvents such as acetone etc., roughening of the surface with roughening tools such as fine grain sandpaper etc. and further cleaning with solvents such as ethanol etc. The surfaces of honeycomb panel (C12H) are prepared by roughening with the help of roughening tools such as metallic brushes, fine grain sandpaper, sand blasting etc. and cleaning with cleaning solvents such as acetone etc. The two - component epoxy adhesive is prepared by mixing the first component and the second component of the said adhesive (A) in the desired ratio in the range of 4:1 to 1:1 preferably 2:1 .

A thin layer of the prepared adhesive (A) is applied over the said prepared surface of thermoplastic composite (C13C) and on the prepared surface of honeycomb panel ( C12H) and further bonding the two together to form a single unit. Weights are placed on the exposed surface of honeycomb panel (C12H) that is part of the single unit obtained, to allow for curing. A thin layer of the prepared adhesive (A) is applied over the surface of the said prepared and exposed surface of honeycomb panel (C12H) of the said single unit. Ceramic tiles of ceramic composite ( C11C) are placed aligned laterally to each other, above the said exposed surface of honeycomb panel ( C12H) of the said single unit, to obtain one layer of ceramic composites (C11CL) bonded to the honeycomb panel (C12H) of the said single unit. Weights are again placed on the said layer of ceramic composite (C11CL) bonded to the honeycomb panel (C12H) to allow curing.

The steps of applying thin coat of prepared adhesive (A) on the top surface of the previous layer, placing ceramic tiles over the surface of previous layer and curing using weights to obtain another layer of the ceramic composites (C11CL), while maintaining the placing on previous layer of ceramic composites (C11CL) in a staggered manner by methods such as double strap joint etc. are repeated to obtain a layer of the ceramic composites (C11CL). More such layers of the ceramic tiles are added to obtain the desired number of layers of the ceramic composite (C11C) for the front panel (C11) to obtain the desired configuration of the hybrid composite material for protection from severe impact (C1).

As per an embodiment the material for lightweight ceramic composite (C21C) of the hybrid composite for protection from projectiles (C2) is selected from group of sintered silicon carbides, reaction bonded silicon carbide, etc. One of the options for the lightweight ceramic composite (C21C) for C2 that is most effective for this purpose is reaction bonded silicon carbide.

The lightweight ceramic composite (C21C) for C2 is in the form of flat tiles whose shape is selected from square, hexagonal, any other shape etc. wherein the most effective shape is found to be hexagonal.

The ceramic composite panel (C21C) for hybrid composite material for protection from projectiles (C2) can be fabricated and adhesively bonded with layers in the range of one to ten, in two configurations (such as but not limited to C21C1 for odd numbered layers and C21C2 for even numbered layers) alternately in a staggered manner by methods such as double strap joint so that the joining interface of the preceding layer is completely covered by the following layer (refer Figure 8(a) and (b)) to achieve maximum impact resistance. The flat tiles of lightweight ceramic composite (C21C) are arranged by adhesive bonding laterally by the side using the adhesive (A) preferably the two-component epoxy adhesive in a compact and economic way to form each layer of the lightweight ceramic composite (C21CL).
Thermoplastic composite (C22C) fabricated as a part of hybrid composite material with high impact resistance for protection from projectiles (C2) is done by autoclave processing as described for the fabrication of thermoplastic composite (C13C) for hybrid composite material with high impact resistance for protection from severe impact (C1) in the previous pages. The material preparation, vacuum bagging(V) and curing cycle to be followed for fabrication of thermoplastic composite (C22C) as part of hybrid composite material for protection from projectiles (C2) are similar to the one explained previously in the case of fabrication of thermoplastic composite (C13C) for hybrid composite material with high impact resistance for protection from severe impact (C1).

In an embodiment of the invention, three layers of thermoplastic polymer films (C22CP) may be stacked alternately with one layer of fabric of synthetic fibers ( C22CF) for good consolidation to obtain thermoplastic composite (C22C) of back panel (C22) keeping the ratio of two components as 3:1 (refer Figure 13). In another embodiment of thermoplastic composite (C22C) has a total of 91 layers of films of the thermoplastic polymer (C22CP) stacked alternately with a total of 90 layers of fabric of synthetic fiber (C22CF), the two components in the ratio 1:1, to obtain the thermoplastic composite (C22C) with thickness in the range of 30- 55 mm of approximately 45 mm. In another specific embodiment of the invention thermoplastic composite (C22C) has a total of 116 layers of films of the thermoplastic polymer (C22CP) stacked alternately with a total of 115 layers of fabric of synthetic fiber (C22CF), the two components in the ratio 1:1, to obtain the thermoplastic composite (C22C) with thickness in the range of 40 - 65 mm of approximately 58 mm.

As per an embodiment of the present invention the design configuration for the hybrid composite for protection from projectiles (C2) is shown in Figure 10. The front panel view and the back panel view of the hybrid composite for protection from projectiles (C2) after fabrication are illustrated in Figure 11(a) and (b) respectively.

The steps of the method for fabrication of hybrid composite material with high impact resistance for protection from projectiles (C2) are described in the following paragraphs.

The surface of thermoplastic composite (C22C) of C2 is prepared by cleaning with cleaning solvents such as acetone etc., followed by roughening of the surface with roughening tools such as fine grain sandpaper etc. and further cleaning with solvents such as ethanol etc. two - component epoxy adhesive is prepared by mixing the first component and the second component of the said adhesive (A) in the desired ratio ranging from 4:1 to 1:1 preferably 2: 1 etc.

A thin layer of the prepared adhesive (A) is applied over the surface of the said prepared surface of thermoplastic composite (C22C) of C2. Ceramic tiles of ceramic composite ( C21C) are placed such that these are aligned laterally to each other and fabricated using adhesive (A) preferably by two-component epoxy adhesive bonding, above the surface of thermoplastic composite (C22C) with applied adhesive (A) to obtain one layer of ceramic composites (C21CL) bonded to the thermoplastic composite (C22C). Weights are placed on the said layer of ceramic composite (C21CL) bonded to the thermoplastic composite (C22C), to allow curing.

The said steps of applying thin coat of prepared adhesive (A), placing ceramic tiles over the surface of previous layer and curing to obtain another layer of the ceramic composites (C21CL), while maintaining the placing on previous layer of ceramic composites (C21CL) in a staggered manner by arrangements such as double strap joint ,are repeated to obtain a second layer of the ceramic tiles for the ceramic composites (C21CL).More layers of the ceramic tiles are added to obtain the desired number of layers of the ceramic composite (C21C) for the front panel (C21) of C2 to obtain the desired configuration of the hybrid composite material for protection from severe impact (C2).

The layers of lightweight ceramic composite (C21C) of C2 are confined by providing a confining sheet (C25) selected from group comprising of polycarbonate covering, polymethyl methacrylate covering etc. over the exposed surface of front panel (C21) and providing lightweight material frame (C24) along with packing material to include elastomer sheet for packing purpose (C26) such as silicone rubber sheet and packaging foam material (C27) such as extended polyethylene foam for tight packing around the perimeter of said hybrid composite for protection from projectiles (C2) to ensure tight packing.

The process of vacuum bagging (V) and autoclave are same as described for the fabrication of hybrid composites for protection from severe impact (C1). For purposes of brevity the description of vacuum bagging (V) and autoclaving as described for fabrication C1 in previous paragraphs are not repeated.

The efficacy and efficiency of the hybrid composite material with high impact resistance for protection from severe impact (C1) or projectiles (C2) have been tested successfully at various levels including by the Terminal ballistic research laboratory (TBRL), India, for STANAG Level III and STANAG Level IV IED and mine threats for protection from severe impact and STANAG Level III bullets threats for protection from projectiles.

EXAMPLES
The present invention shall now be explained with accompanying examples. These examples are non-limiting in nature and are provided only by way of representation. While certain language has been used to describe the disclosure, any limitations arising on account of the same are not intended. As would be seeming to a person skilled in the art, various working alterations may be made to the method in order to implement the inventive concept as taught herein. The figures and the preceding description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternately, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, order of steps of method or processes of data flow described herein may be changed and is not limited to the manner described herein. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts need to be necessarily performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples.

In an exemplary embodiment, the various materials which on fabrication form the hybrid composite with high impact resistance for protection from severe impact (C1) or for protection from projectiles (C2) along with the working of the invention and the method of fabrication thereof are illustrated below.

Para aramid fibers have been used as high performance synthetic fibers as the reinforcement phase for the high performance thermoplastic composite (C13C) for hybrid composite material for protection from severe impact (C1) or thermoplastic composite (C22C) for hybrid composite material for protection from projectiles (C2) of the impact resistant hybrid composite (C). ALKEX is an example of high-strength para-aramid fiber produced by Hyosung Advanced Materials. The synthetic fiber (C13CF/ C22CF) utilized in preparing thermoplastic composite (C13C/ C22C) is a high performance para aramid fiber has weave pattern selected from group of plain, twill, satin and basket, has width as required for the application, weight in the range of 220 gsm to 480 gsm, thickness in the range of 0.25 mm to 0.75 mm, yarn code selected from AF1000 to 3000D, threads per inch have warp in the range of 15- 20, weft in the range of 10- 20, density in the range of 1.34 g/cm3- 1.5 g/cm3, yarn has breaking tenacity in the range of 2.00 GPa to 3. 45 GPa, modulus in the range of 60 GPa to 140 GPa, and elongation in the range of 3.3% to 4.5%. The properties and specification of the ALKEX fabric which is high performance para aramid fiber utilized in an embodiment of the present invention are shown below in Table 4.
Table 4: Properties and specifications of ALKEX Fiber
PROPERTY SPECIFICATION
Weave pattern : Plain
Width : 1000 mm
Weight : 460 gsm
Thickness : 0.5 mm
Yarn Code : AF1000 – 3000D
Threads per inch- Warp : 17
Weft : 16
Density : 1.44 g/cm3
Yarn Properties- Breaking tenacity : 2.9 GPa
Modulus : 65 GPa
Elongation : 4.2%

Polyether ketone ketone (PEKK) is an example of thermoplastic polymer (C13CP/ C22CP) utilized for preparing the thermoplastic composite (C13C or C22C) and was procured in the form of a film. The stress strain graph for PEK material used in another such embodiment is illustrated in Figure 12 of drawings of the specification. The thermoplastic polymer (C13CP/C22CP) utilized for preparing the thermoplastic composite (C13C or C22C) has film thickness in the range of 0.05 mm to 0.5 mm, width in the range of 50 mm to 500 mm, density in the range of 0.75 g/cm3 to 2.5 g/cm3 , melting point in the range of 280°C to 372 °C, film tensile strength in the range of 70 MPa to 150 MPa and film elongation to break greater than 150%. The specifications of the film of thermoplastic polymer to include PEKK and PEKK utilized in embodiments of the present invention are tabulated below in Table 5.
Table 5: Properties and specifications of PEKK and PEEK Film
PROPERTY SPECIFICATION
Film thickness : 0.1 mm
Width : 100 mm
Density : 1.27 g/cm3
Melting point : 309 0C
Film tensile strength : 80 MPa
Film elongation to break : >150%
The lightweight ceramic composite (C11/C21) utilized in the front panel (C11/C21) of the hybrid composite material for protection from severe impact (C1) or protection from projectiles (C2) has bulk density in the range of 2.95 g/cm3 to 3.25 g/cm3, Rockwell hardness in the range of 70 HRA - 100 HRA, modulus of rupture in the range of 350 MPa to 450 MPa and sonic velocity in the range of 11300 m/s to 11600 m/s. A variety of the ceramic composite material silicon carbide is reaction bonded silicon carbide (RBSiC) that has been utilized in the front panel of the hybrid composite material for protection from severe impact (C1) or protection from projectiles (C2) and the properties of the material used are tabulated below in Table 6.
Table 6: Properties and specifications of Reaction Bonded Silicon Carbide Tiles
PROPERTY SPECIFICATION
Bulk density : 3.05 g/cm3
Rockwell hardness : 90 HRA
Modulus of rupture : 371 MPa
Sonic velocity : 11486 m/s

As per an embodiment of the present invention, aluminium in the form of aluminium alloy such as but not limited to aluminium alloy of 3000 series has been used for honeycomb panel (C12H) that forms the lightweight core material panel (C12) of the hybrid composite material for protection from severe impact(C1). The honeycomb panel (C12H) has total thickness in the range of 5 mm to 30 mm, skin thickness in the range of 0.5 mm to 2.0 mm, cell size in the range of 3.5 mm to 10.0 mm, foil thickness in the range of 0.02 mm to 2.0 mm, core density in the range of 75 Kg/m3 to 100 Kg/m3 , bare compressive strength in the range of 3.5 MPa to 6.5 MPa wherein the aluminium alloy is selected from 1000 to 8000 series fulfilling the characteristics mentioned herein. This material of aluminium honeycomb panel has been procured from Honylite Private Limited, Noida and its specifications are tabulated below in Table 7.
Table 7: Properties and specifications of Aluminium Honeycomb Panel
PROPERTY SPECIFICATION
Total thickness : 10 mm
Skin thickness : 1 mm
Cell size : 6.4 mm
Foil thickness : 0.07 mm
Core density : 85 kg/m3
Bare compressive strength : 4.69 MPa
Aluminium alloy : Al-3003

Adhesive (A), a two-component epoxy adhesive, utilized in an embodiment of the invention for preparing the composite material for protection from severe impact or projectiles (C1 or C2) has density in the range of 1.0 to 2.0 g/cm3, mixing ratio of said two components in the ratio of 4:1 to 1:1, pot life after mixing in the range of 10 minutes to 15 minutes, lap shear strength in the range of 10 MPa to 25 MPa, flexural strength in the range of 35 MPa to 60 MPa, tensile strength in the range of 15 MPa to 35 MPa, compressive strength in the range of 30 MPa to 50 MPa, hardness in the range of 65 shore D to 85 shore D and water absorption (24 hours)in the range of 0.2% to 0.4%. An example of an adhesive (A) used for fabricating the impact resistant composite material for protection from severe impact or projectiles (C1 or C2) is Lapox Ultrafix, a high-strength epoxy adhesive, manufactured by Atul Ltd. The property and specifications of the adhesive (A) , Lapox ultrafix, used in the present invention are tabulated below in Table 8.

Table 8: Properties and specifications of Lapox ultrafix adhesive
PROPERTY SPECIFICATION
Density : 1.55 g/cm3
Mixing ratio : 2:1
Pot life after mixing : 10 - 15 minutes
Lap shear strength : 15 MPa
Flexural strength : 43 MPa
Tensile strength : 25 MPa
Compressive strength : 40 MPa
Hardness : 75 shore D
Water absorption (24 hours) : 0.3%

A summary of the properties of the examples of various materials used in the embodiments of the present invention are presented in the table below in Table 9.
Table 9: Summary of materials used in the invention
Material Manufacturer Purpose
ALKEX Fabric Hyosung Advanced Materials, South Korea.

Weaved and supplied by Padmini Innovative Marketing Solutions (P)LTD Utilized as a Reinforcement for the rigid backing composite plate.

ALKEX fibre is a high strength fibre providing excellent protection against fragment impacts

PEKK Film Gharda Chemicals Limited, Mumbai Utilized as a matrix for the rigid backing composite plate.

Binds the high performance synthetic ALKEX fibre.
Aluminium Honeycomb Panel Honylite Private Limited, Greater Noida Provides energy absorption capabilities for the panel during a blast wave impact
Reaction Bonded Silicon Carbide Plates Carborundum Universal Limited, Hosur Provides thermal protection to mitigate the high temperatures a blast.

It also provides a high hardness surface for mitigation and blunting of fragments and shrapnel.
Lapox Ultrafix Adhesive Atul Adhesive Limited, Mumbai A two-component room temperature curing adhesive which provides excellent bonding capabilities for dissimilar materials and has good environmental resistance.

The material of thermoplastic composite (C12C) for the hybrid composite material for protection from severe impact (C1) is first prepared by cutting, shaping, and stacking or layering the various components to create the desired shape and structure. The para aramid fibers are cut into dimensions of 1000mm x 1000mm while PEKK polymer composite film of width 100 mm are cut into pieces of length 1000mm. The fiber and film are alternately stacked with 20 layers of fabric and 21 layers of film. Each layer of the film comprises ten lines, with each line consisting of a 100 mm wide strip of film placed side by side.

The configuration of the vacuum bagging (V) setup as described for the present invention is illustrated in Figure 2. The specific examples of the materials used for autoclave processing in the present invention are as follows:
• Release Film (V8): Kapton Film
• Perforated Film (V6): Kapton film with holes
• Vacuum Bagging Film (V4): Kapton Film
• Sealant (V3): GS Tape and Kapton Tape
As per the process of vacuum bagging (V) a thermocouple (V2) is embedded within the stacked layers (V7) of fiber and film for monitoring the temperature. Once the material of stacked layers (V7) is in the vacuum bag (V), the air inside the bag is evacuated using a vacuum pump. This evacuation creates a pressure differential between the inside of the bag and the outside, which compresses the layers of material together and removes any trapped air. The bagging film (V4) material is pulled tightly against the material of stacked layers (V7) to ensure good contact and remove any wrinkles or folds. After the vacuum is established, the bag (V) is sealed using sealing tapes (V3) such as GS Tape and Kapton Tape to prevent any air from leaking back into the bag.
The vacuum bagged layers in the vacuum bag (V) are loaded into the autoclave for curing cycle. The autoclave is heated and pressurized to the desired temperature and pressure conditions. The temperature of 310 0C and pressure 8 bar conditions are carefully controlled and monitored throughout the process to ensure the proper curing of the material.

The vacuum bagged layers material is cured under the high temperature and pressure conditions for a period of 6hrs. The curing process allows the resin to flow and bond the various layers of material together, creating a strong and durable final product. After the curing process is complete, the autoclave is slowly cooled to room temperature to prevent any damage to the material. This cooling process may take several hours or more. The final product of composite panel (C13C or C22C) material (of thickness of approximately 10 mm in case of C1) is then removed from the autoclave and any excess material trimmed by waterjet cutting. The autoclave cycle followed during the fabrication of composite panel (C13C or C22C) material such as ALKEX/PEKK composite is (thermoplastic composite ) shown in Figure 3.
A layered hybrid composite material for protection from severe impact (C1) of dimension 1000 mm x 1000 mm was fabricated.
- The flat surface of autoclave processed ALKEX/PEK composite is cleaned with acetone for any dust and other surface impurities. The surface is roughened with a fine grain sandpaper carefully. Further, the surface is cleaned with ethanol.
- The surface of the honeycomb panel is roughened with the help of metallic brushes, fine grain sandpaper and sand blasting. Further, the surface is thoroughly cleaned with acetone.
- Around 900g of adhesive (600 g of resin and 300 g of hardener in the ratio 2:1 is prepared by thorough mixing. A thin layer of adhesive is applied over the ALKEX/PEKK composite and honeycomb panel and they both are bonded together. C Clamps are used to ensure the panels do not slip over each other while loads are kept over the honeycomb plate. The setup is allowed to cure for 24 hours. The bonded panel at this stage of fabrication is shown in Figure 6.
- Square RBSiC ceramic tiles (50 mmx50 mm) of 6 mm thickness are layered above the aluminium honeycomb panel in a staggered manner by double strap joint. The adhesive is applied over the ceramic and placed on the hybrid composite to form the first layer. After one layer of ceramic tiles are placed over the surface, adequate weights are kept on the layer for curing. Four layers of ceramics tiles are stacked over each other in total resulting in a 24 mm thickness of ceramic panel.
- The ceramic composite panel (C11C) was fabricated with four layers in two configurations (C11C1 for odd numbered layers and C11C2 for even numbered layers)) alternately for maximum impact resistance.

Subsequent layers of ceramic tiles are bonded with a staggered approach so as to ensure the joining interface of the preceding layer is completely covered by the following layer. The final bonded hybrid composite is shown in Figure 7.

Fabrication of hybrid composite material for protection from projectiles (C2) is as described below.

ALKEX fabric reinforced PEKK or ALKEX/PEKK composite is an example of the high performance thermoplastic composites (C22C) used in the back panel (C22) of the hybrid composite material for protection from projectiles (C2). ALKEX/PEKK composite as a part of hybrid composite panel for protection from projectiles (C2) was fabricated by autoclave processing as described for the fabrication of ALKEX/PEKK composite for hybrid composite material for protection from severe impact (C1) in the previous examples. The material preparation, vacuum bagging and curing cycle to be followed for fabrication of ALKEX/PEKK composite as part of hybrid composite material for protection from projectiles (C2) are similar to the one explained previously in the case of fabrication of ALKEX/PEKK composite for hybrid composite material for protection from severe impact (C1).

The ALKEX/PEKK composites prepared for protection from projectiles are of dimensions 500 mm x 500 mm. Two variations of ALKEX/PEKK composite were fabricated as below.
- With 90 layers of ALKEX fabric stacked alternately with 91 layers of PEKK film resulting in an ALKEX/PEKK composite of thickness close to 45 mm.
- With 115 layers of ALKEX fabric stacked alternately with 116 layers of PEKK film resulting in an ALKEX/PEKK composite of thickness close to 58 mm.

As per an embodiment of the present invention the design configuration for the hybrid composite for protection from projectiles (C2) is shown in Figure 10.

A layered hybrid composite material for protection from projectiles (C2) of dimension 500 mm x 500 mm was fabricated. The said hybrid composite material for protection from projectiles (C2) is assembled in the following steps:
- The flat surface of autoclave processed ALKEX/PEKK composite is cleaned with acetone for any dust and other surface impurities. The surface is roughened with a fine grain sandpaper carefully. Further, the surface is cleaned with ethanol.
- The hexagonal ceramic tiles of 6 mm thickness are layered above ALKEX/PEKK composite in a staggered manner by double strap joint. Four layers of ceramics are stacked over each other in total resulting in a 24 mm thickness of ceramic layer. The ceramic composite panel (C21C) was fabricated with four layers in two configurations (C21C1 for odd numbered layers and C21C2 for even numbered layers)) alternately for maximum impact resistance in total resulting in a 24 mm thickness of ceramic composites.
- The adhesive is applied over the ceramic and placed on the hybrid composite. After one layer of ceramic tiles are placed over the surface, adequate weights are kept on the layer for curing. Subsequent layer of ceramic tiles is bonded with a staggered approach so as to ensure the joining interface of the preceding layer is completely covered by the following layer. The details of the ceramic layered configurations are given in Figure 8. The view of thermoplastic (ALKEX/PEKK) composite (C22C) bonded with layered hexagonal lightweight ceramic composite (C21C) tiles is as illustrated in Figure 9.
- An aluminium frame with a polycarbonate covering was provided around the perimeter of the hybrid composite to ensure confinement of the ceramic tiles. The image of the design and configuration are provided in the Figure 10. Silicone rubber sheet and extended polyethylene foam was utilized for tight packing.
,CLAIMS:We claim:
1. A hybrid composite material with high impact resistance for protection from severe impact (C1) on a structure wherein said hybrid composite material comprises of:
- at least one front panel (C1101, C1102, .., C11n), prepared from layer(s) (C11CL01, C11CL02, …, C11CLn) of lightweight ceramic composites (C11C), that is deployed on the exterior (E);
- at least one back panel (C1301, C1302, ..., C13n), made of thermoplastic composite (C13C), that is deployed on the interior (I) and
- at least one panel of lightweight core material (C1201, C1202, .., C12n), prepared using honeycomb panel (C12H), that is deployed between said front panel(s) (C1101, C1102, .., C11n) on the exterior (E) and said back panel(s) (C1301, C1302, ..., C13n) on the interior (I) of said hybrid composite material in a sandwich configuration using adhesive (A)
wherein
• said layers (C11CL01, C11CL02, …, C11CLn) of said lightweight ceramic composites (C11C) of said front panel (C11) of said hybrid composite material (C1) are stacked and bonded with each other using said adhesive (A),
• said adhesive (A), utilized to bond the various panels of said hybrid composite for protection from severe impact (C1), is capable of being cured at room temperature,
• said panel of lightweight core material (C12) comprises of lightweight material resistant to fire, corrosion and moisture and has high strength to weight ratio 2 to 3 times of that of protection steel such as armored steel, that is capable of being fabricated into a honeycomb configuration thus enabling absorption and dissipation of energy from severe impact,
• said back panel (C13) made of said thermoplastic composite (C13C), said thermoplastic composite (C13C) comprising of
o thermoplastic polymer (C13CP) from the family of polyaryl ether ketones (PAEK) that are high performance thermoplastics having high strength, toughness, stiffness, fatigue resistance, thermal stability and impact resistance that are capable of being formed into films and
o synthetic fiber (C13CF) having high strength, durability, thermal stability, high resistance to abrasion, chemicals, and UV radiation and low elongation-to-break ratio to act as reinforcing phase for said thermoplastic polymer (C13CP), capable of being knitted or woven in the form of fabrics
in a manner that a plurality of layers of films of said thermoplastic polymer (C13CP) are stacked alternately with a plurality of layers of fabric of synthetic fiber (C13CF) and fabricated using process of vacuum bagging (V) followed by autoclaving , to obtain said thermoplastic composite(C13C)
thereby providing impact resistance and protection to said structure from severe impact, said material (C1) being lightweight, easy to fabricate, portable and effective at affordable cost.
2. The hybrid composite material for protection from severe impact (C1) as claimed in claim 1, wherein said front panel (C11) is prepared from said lightweight ceramic composite (C11C) that has high resistance to penetration, exceptional hardness, ability to withstand high-velocity impacts, high strength to weight ratio and high resistance to abrasion, corrosion, and extreme temperatures.
3. The hybrid composite material for protection from severe impact (C1) as claimed in claim 2, wherein said lightweight ceramic composite (C11C) is selected from group of silicon carbides including sintered silicon carbides and reaction bonded silicon carbides.
4. The hybrid composite material for protection from severe impact (C1) as claimed in claim 3, wherein said lightweight ceramic composite (C11C) is reaction bonded silicon carbide that has bulk density in the range of 2.95 g/cm3 to 3.25 g/cm3, Rockwell hardness in the range of 70 HRA to 100 HRA, modulus of rupture in the range of 350 MPa to 450 MPa and sonic velocity in the range of 11300 m/s to 11600 m/s.
5. The hybrid composite material for protection from severe impact (C1) as claimed in claim 4, wherein said reaction bonded silicon carbide has properties and specifications as below:
PROPERTY SPECIFICATION
Bulk density : 3.05 g/cm3
Rockwell hardness : 90 HRA
Modulus of rupture : 371 MPa
Sonic velocity : 11486 m/s
6. The hybrid composite material for protection from severe impact (C1) as claimed in claim 1, wherein said lightweight ceramic composite (C11C) are in the form of flat tiles whose shape is selected from group of square, hexagonal and any other shape capable of being assembled into layers in a compact manner.
7. The hybrid composite material for protection from severe impact (C1) as claimed in claim 6, wherein said flat tiles of lightweight ceramic composite (C11C) are of square shape.
8. The hybrid composite material for protection from severe impact (C1) as claimed in claim 7, wherein said flat tiles have lateral dimension in the range of 30 mm to 100 mm, preferably 50 mm and thickness in the range of 2 mm to 20 mm, preferably 6 mm.
9. The hybrid composite material for protection from severe impact (C1) as claimed in claim 1, wherein said lightweight ceramic composite (C11C) is layered, with number of layers ranging from one to ten preferably four.
10. The hybrid composite material for protection from severe impact (C1) as claimed in claim 6, wherein said flat tiles of said lightweight ceramic composite (C11C) are arranged and bonded laterally by the sides using said adhesive (A) in a compact and economic way to form each layer of said lightweight ceramic composite (C11CL).
11. The hybrid composite material for protection from severe impact (C1) as claimed in claim 10, wherein said layers of lightweight ceramic composite (C11CL) are assembled in two configurations, configuration C11C1 for odd numbered layers and configuration C11C2 for even numbered layers, in a staggered approach so as to ensure that the joining interface of preceding layer is completely covered by the following layer.
12. The hybrid composite material for protection from severe impact (C1) as claimed in claim 1, wherein said panel of lightweight core material (C12) is fabricated from material with high strength to weight ratio 2 to 3 times of that of protection steel such as armored steel and is selected from group of aluminium, aluminium alloys.
13. The hybrid composite material for protection from severe impact (C1) as claimed in claim 12, wherein said lightweight core material (C12) is fabricated by bonding processes such as adhesive bonding together of foil sheets (C12HF) of said material into a honeycomb core configuration using adhesive (A) and further assembled in the form of sandwich panels that comprise of a face sheet or skin of same or other material, bonded to the honeycomb core on each of its lateral side by bonding processes such as adhesive bonding, using adhesive (A), wherein the adhesive (A) used is preferably two-component epoxy adhesive.
14. The hybrid composite material for protection from severe impact (C1) as claimed in claim 12, wherein said material with high strength to weight ratio for said lightweight core material (C12) is aluminium alloy selected from 1000 to 8000 series that has total thickness in the range of 5 mm to 30 mm, skin thickness in the range of 0.5 mm to 2.0 mm, cell size of honeycomb in the range of 3.5 mm to 10.0 mm, foil thickness in the range of 0.02 mm to 2.0 mm, core density in the range of 75 Kg/m3 to 100 Kg/m3 and bare compressive strength in the range of 3.5 MPa to 6.5 MPa.
15. The hybrid composite material for protection from severe impact (C1) as claimed in claim 14, wherein said aluminium alloy for said lightweight core material (C12) has below properties and specifications.
PROPERTY SPECIFICATION
Total thickness : 10 mm
Skin thickness : 1 mm
Cell size of honeycomb : 6.4 mm
Foil thickness : 0.07 mm
Core density : 85 kg/m3
Bare compressive strength : 4.69 MPa
Aluminium alloy : Al-3003
16. The hybrid composite material for protection from severe impact (C1) as claimed in claim 1, wherein said thermoplastic composite (C13C) of said back panel (C13) is fabricated using layers of films of said thermoplastic polymer (C13CP) and layers of fabric of said synthetic fiber (C13CF) stacked alternately in ratio ranging from 4:1 to 1:1, wherein the layers of films of said thermoplastic polymer (C13CP) ranges in number from 10 to 200 and layers of fabric of said synthetic fiber (C13CF) ranges in number from 10 to 50 to obtain said thermoplastic composite (C13C) with thickness in the range of 5 mm to 70 mm.
17. The hybrid composite material for protection from severe impact (C1) as claimed in claim 16, wherein said thermoplastic composite (C13C) of back panel (C13) has 21 layers of films of said thermoplastic polymer (C13CP) stacked alternately with 20 layers of fabric of said synthetic fiber (C13CF) to obtain said thermoplastic composite (C13C) with thickness in the range of 8 mm to 12 mm.
18. The hybrid composite material for protection from severe impact (C1) as claimed in claim 1, wherein said thermoplastic polymer (C13CP) for preparing said thermoplastic composite (C13C) of back panel (C13) is selected from group of high performance thermoplastic polymers comprising of polyether ketone ketone (PEKK), polyether ketone (PEK), polyether ether ketone (PEEK), polyether Imide (PEI).
19. The hybrid composite material for protection from severe impact (C1) as claimed in claim 18, wherein said thermoplastic polymer (C13CP) for preparing thermoplastic composite (C13C) of back panel (C13) is polyether ketone ketone (PEKK) polymer that has film thickness in the range of 0.05 mm to 0.5 mm, width in the range of 50 mm to 500 mm, density in the range of 0.75 g/cm3 to 2.5 g/cm3 , melting point in the range of 280°C to 372 °C, film tensile strength in the range of 70 MPa to 150 MPa and film elongation to break that is greater than 150%.
20. The hybrid composite material for protection from severe impact (C1) as claimed in claim 19, wherein said polyether ketone ketone (PEKK) polymer used to prepare said thermoplastic composite of said back panel (C13) has the following properties and specifications.
PROPERTY SPECIFICATION
Film thickness : 0.1 mm
Width : 100 mm
Density : 1.27 g/cm3
Melting point : 309 0C
Film tensile strength : 80 MPa
Film elongation to break : >150%
21. The hybrid composite material for protection from severe impact (C1) as claimed in claim 1, wherein said synthetic fiber (C13CF) for preparing said thermoplastic composite (C13C) of back panel (C13) is selected from group of high performance para aramid fiber, meta aramid fiber, preferably high performance para aramid fiber.
22. The hybrid composite material for protection from severe impact (C1) as claimed in claim 21, wherein said high performance para aramid fiber has weave pattern selected from group of plain, twill, satin and basket, has width as required for application, weight in the range of 220 gsm to 480 gsm, thickness in the range of 0.25 mm to 0.75 mm, yarn code selected from AF1000 to 3000D, threads per inch have warp in the range of 15 to 20, weft in the range of 10- 20 and density in the range of 1.34 g/cm3 to 1.5 g/cm3, yarn has breaking tenacity in the range of 2.00 GPa to 3. 45 GPa, modulus in the range of 60 GPa to 140 GPa, and elongation in the range of 3.3% to 4.5%.
23. The hybrid composite material for protection from severe impact (C1) as claimed in claim 22, wherein said high performance para aramid fiber has the following properties and specifications.
PROPERTY SPECIFICATION
Weave pattern : Plain
Width : 1000 mm
Weight : 460 gsm
Thickness : 0.5 mm
Yarn Code : AF1000 – 3000D
Threads per inch - Warp : 17
Weft : 16
Density : 1.44 g/cm3
Yarn Properties - Breaking tenacity : 2.9 GPa
Modulus : 65 GPa
Elongation : 4.2%
24. The hybrid composite material for protection from severe impact (C1) as claimed in claim 1, wherein said adhesive (A) is selected from group of high temperature epoxy adhesive, polyimide adhesive, preferably a two–component epoxy adhesive consisting of two components, a resin and a hardener, which are mixed together in proportions with ratio ranging from 4:1 to 1:1 preferably 2:1 , to form a strong and durable bond in a period of time lesser than 36 hrs, preferably lesser than 24 hrs and is designed to cure at room temperature, without the need for additional heat or curing agents.
25. The hybrid composite material for protection from severe impact (C1) as claimed in claim 24, wherein said adhesive (A) has density in the range of 1.0 g/cm3 to 2.0 g/cm3, mixing ratio of said two components in the ratio of 4:1 to 1:1, pot life after mixing in the range of 10 minutes to 15 minutes, lap shear strength in the range of 10 MPa to 25 MPa, flexural strength in the range of 35 MPa to 60 MPa, tensile strength in the range of 15 MPa to 35 MPa, compressive strength in the range of 30 MPa to 50 MPa, hardness in the range of 65 shore D to 85 shore D and water absorption (24 hours) in the range of 0.2% to 0.4%.
26. The hybrid composite material for protection from severe impact (C1) as claimed in claim 25, wherein said adhesive (A) has the following properties and specifications.
PROPERTY SPECIFICATION
Density : 1.55 g/cm3
Mixing ratio : 2:1
Pot life after mixing : 10 - 15 minutes
Lap shear strength : 15 MPa
Flexural strength : 43 MPa
Tensile strength : 25 MPa
Compressive strength : 40 MPa
Hardness : 75 shore D
Water absorption (24 hours) : 0.3%
27. A method for fabrication of hybrid composite material with high impact resistance for protection from severe impact (C1) wherein said method comprises of steps of:
- preparing one of the two surfaces of thermoplastic composite (C13C) by cleaning with cleaning solvents to include acetone, roughening of said surface with roughening tools to include fine grain sandpaper and further cleaning with solvents to include ethanol;
- preparing both surfaces of honeycomb panel ( C12H) by roughening with the help of roughening tools to include metallic brushes, fine grain sandpaper, sand blasting and cleaning with cleaning solvents to include acetone;
- preparing of two - component epoxy adhesive by mixing first component and second component of said adhesive (A) in desired ratio in the range of 4:1 to 1:1, preferably 2:1;
- applying a thin layer of said prepared adhesive (A) over said prepared surface of thermoplastic composite (C13C) and on one of said prepared surfaces of honeycomb panel (C12H) and thereafter bonding the two together to form a single unit;
- placing of weights on the exposed surface of honeycomb panel (C12H) that is part of the single unit obtained, to allow for bonding and curing;
- applying a thin layer of the prepared adhesive (A) over the surface of the said prepared and exposed surface of honeycomb panel (C12H) of said single unit;
- placing of ceramic tiles of lightweight ceramic composite (C11C), aligned laterally to each other and using bonding processes preferably adhesive bonding above the said exposed surface of honeycomb panel (C12H) of said single unit using adhesive (A), preferably a two-component epoxy adhesive, to obtain one layer of lightweight ceramic composites (C11CL) bonded to the honeycomb panel (C12H) of said single unit;
- placing of weights on said layer of lightweight ceramic composite (C11CL) bonded to said thermoplastic composite (C13C), to allow for bonding and curing;
- repeating said steps of applying thin coat of prepared adhesive (A) on the top surface of the previous layer of lightweight ceramic composites (C11CL), placing ceramic tiles over the surface of previous layer and curing using weights to obtain another layer of the lightweight ceramic composites (C11CL), while maintaining the placing on previous layer of lightweight ceramic composites (C11CL) in a staggered manner and
- layering further of the ceramic tiles to obtain the desired number of layers of the lightweight ceramic composite (C11CL) for the front panel (C11) to obtain the desired configuration of the hybrid composite material for protection from severe impact (C1).
28. The method for fabrication as claimed in claim 27, wherein said thermoplastic composite (C13C) of back panel (C13) of hybrid composite material with high impact resistance for protection from severe impact (C1) is fabricated by a process the steps of which comprise of:
- preparing of films of thermoplastic polymer (C13CP) by cutting it into strips of desired width preferably 100 to 500 mm and desired length;
- preparing of fabric of synthetic fiber (C13CF) by cutting said fabric into desired shape and size for application purpose;
- preparing a layer of thermoplastic polymer (C13CP) film by placing said strips of said thermoplastic polymer (C13CP) side by side laterally until to obtain a layer of said thermoplastic polymer (C13CP) of desired size for application purpose;
- stacking of said layers of fabrics of synthetic fiber (C13CF) and said layers of thermoplastic polymer (C13CP) film alternately to obtain stacked layers (V7);
- placing said stacked layers (V7) of said two materials in a vacuum bag and vacuum bagging or vacuuming said stacked layers (V7) by drawing out the air to compress said layers together to remove any trapped air;
- loading the vacuumed layers of the said two materials in the vacuum bag into an autoclave for the curing cycle;
- heating and pressurizing the autoclave to desired temperature ranging between
250 0C to 400 0C and pressure conditions of 4 bar to 10 bar;
- curing under said desired high temperature and pressure conditions for a specified period of time in the range of 4 hrs to 8 hrs while keeping the desired temperature and pressure conditions controlled and monitored throughout the process to ensure the proper autoclaving and curing of the vacuumed layers of the two materials to obtain a single autoclaved product;
- cooling the autoclave to room temperature after completion of curing process to prevent any damage to said autoclaved product and
- removing said autoclaved product from the autoclave and trimming any excess material by waterjet cutting.
29. The method for fabrication as claimed in claim 28, wherein said method of vacuum bagging of said layers of the two material components of thermoplastic composite (C13C) of back panel (C13) has steps comprising of:
- embedding of thermocouple (V2) within the stacked layers (V7) of said two material components of thermoplastic composite (C13C) in vacuum bag (V) for monitoring the temperature;
- pulling bagging material of said vacuum bag (V) tightly against said stacked layers (V7) of said two material components of thermoplastic composite (C13C) to ensure good contact and removal of any wrinkles or folds in said layers of the two materials;
- removing air from the material of said stacked layers (V7) of components of thermoplastic composite (C13C) placed inside said vacuum bag (V) by using a vacuum pump thus creating a pressure differential between the inside of said bag (V) and the outside, which compresses said layers of the two materials together and removes any trapped air and
- sealing of said vacuum bag (V) after the vacuum is established by using sealing tapes to include GS Tape and Kapton Tape to prevent any air from leaking back into said bag (V).
30. The method for fabrication as claimed in claim 28, wherein the autoclaving is performed with conditions of holding temperature ranging from 250°C to 400°C, heating rate is in the range of 1°C to 5°C, holding time is in the range of 30 minutes to 120 minutes, cooling rate is in the range of 2°C to 8 °C and pressure is maintained in the range of 4 bars to 10 bars.
31. The method for fabrication as claimed in claim 30, wherein the autoclaving is performed with conditions as mentioned below:
CONDITION VALUE
Holding temperature : 310 °C
Heating rate : 3 °C
Holding time : 60 minutes
Cooling rate : 5 °C
Pressure : 8 bars
32. The hybrid composite material for protection from severe impact (C1) as claimed in claim 1, wherein said material (C1) has practical applications in various fields to include mining industry, aviation, space, civil infrastructures, oil and gas industry etc.
33. A hybrid composite material with high impact resistance for protection from projectiles (C2) on a structure or living thing wherein said hybrid composite material comprises of:
- at least one front panel (C2101, C2102, .., C21n), prepared from layer(s) (C21CL01, C21CL02, …, C21CLn) of lightweight ceramic composites (C21C), that is deployed on the exterior (E) and
- at least one back panel (C2201, C2202, .., C22n), made of thermoplastic composite (C22C), that is deployed on the interior (I)
wherein
• said layers (C21CL01, C21CL02, …, C21CLn) of said lightweight ceramic composites (C21C) of said front panel (C21) of said hybrid composite material (C2) are stacked and bonded with each other using adhesive (A),
• said adhesive (A), utilized to bond the various panels of said hybrid composite for protection from projectiles (C2), is capable of being cured at room temperature,
• said back panel (C22) made of thermoplastic composite (C22C), said thermoplastic composite (C22C) comprising of:
o thermoplastic polymer (C22CP) from the family of polyaryl ether ketones (PAEK) that are high performance thermoplastic polymers having high strength, toughness, stiffness, fatigue resistance, thermal stability and impact resistance and capable of being formed into films and
o synthetic fiber (C22CF) having high strength, durability, thermal stability, high resistance to abrasion, chemicals, and UV radiation and low elongation-to-break ratio to function as reinforcing phase for said thermoplastic polymer (C22CP) capable of being knitted or woven in the form of fabrics
in a manner that a plurality of layers of films of said thermoplastic polymer (C22CP) are stacked alternately with a plurality of fabric of synthetic fiber (C22CF) and fabricated using process of vacuum bagging followed by autoclaving to obtain said thermoplastic composite (C22C),
• said panels of hybrid composite for protection from projectiles (C2) are assembled in a way that said front panel (C21) and said back panel (C22) are bonded together using said adhesive (A), to form said hybrid composite (C2),
• said lightweight ceramic composite (C21C) of said front panel (C21) is assembled in a manner that said layers of lightweight ceramic composite (C21CL) are confined by providing a confining sheet (C25) selected from group comprising of polycarbonate covering , polymethyl methacrylate covering over the exposed surface of front panel (C21) and providing lightweight material frame (C24) along with packing material to include elastomer sheet for packing purpose (C26) to include silicone rubber sheet and packaging foam material (C27) to include extended polyethylene foam for tight packing around the perimeter of said hybrid composite for protection from projectiles (C2) to ensure tight packing
thereby providing impact resistance and protection to living and non-living objects to include vehicles, equipment, critical infrastructures and other such high value assets from the impact of projectiles said material (C2) being lightweight, easy to fabricate, portable and effective at affordable cost.
34. The hybrid composite material for protection from projectiles (C2) as claimed in claim 33, said front panel (C21) is prepared from said lightweight ceramic composites (C21C) that has high resistance to penetration, exceptional hardness, ability to withstand high-velocity impacts, high strength to weight ratio and high resistance to abrasion, corrosion, and extreme temperatures.
35. The hybrid composite material for protection from projectiles (C2) as claimed in claim 34, wherein said lightweight ceramic composite (C21C) is selected from group of silicon carbides including sintered silicon carbides, reaction bonded silicon carbide.
36. The hybrid composite material for protection from projectiles (C2) as claimed in claim 35, wherein said lightweight ceramic composite (C21C) is reaction bonded silicon carbide that has bulk density in the range of 2.95 g/cm3 to 3.25 g/cm3, Rockwell hardness in the range of 70 HRA to 100 HRA, modulus of rupture in the range of 350 MPa to 450 MPa and sonic velocity in the range of 11300 m/s to 11600 m/s .
37. The hybrid composite material for protection from projectiles (C2) as claimed in claim 36, wherein said lightweight ceramic composite (C21C) that is reaction bonded silicon carbide has properties and specifications as below:
PROPERTY SPECIFICATION
Bulk Density : 3.05 g/cm3
Rockwell Hardness : 90 HRA
Modulus of Rupture : 371 MPa
Sonic Velocity : 11486 m/s
38. The hybrid composite material for protection from projectiles (C2) as claimed in claim 33, wherein said lightweight ceramic composite (C21C) are in the form of flat tiles whose shape is selected from group of square, hexagonal and any other shape capable of being assembled into layers in a compact manner.
39. The hybrid composite material for protection from projectiles (C2) as claimed in claim 38, wherein said flat tiles of lightweight ceramic composite (C21C) are of hexagonal shape.
40. The hybrid composite material for protection from projectiles (C2) as claimed in claim 39, wherein said flat tiles have lateral dimensions in the range of 30 mm to 100 mm and thickness in the range of 2 mm to 20 mm preferably 6 mm.
41. The hybrid composite material for protection from projectiles (C2) as claimed in claim 33, wherein said lightweight ceramic composite (C21C) is layered, with number of layers ranging from one to ten preferably four.
42. The hybrid composite material for protection from projectiles (C2) as claimed in claim 38, wherein said flat tiles of said lightweight ceramic composite (C21C) are arranged and bonded laterally by the side using adhesive (A) in a compact and economic way to form each layer of said lightweight ceramic composite (C21CL) .
43. The hybrid composite material for protection from projectiles (C2) as claimed in claim 42, wherein said layers of lightweight ceramic composite (C21CL) are assembled in two configurations, configuration C21C1 for odd numbered layers and configuration C21C2 for even numbered layers, in a staggered approach so as to ensure that the joining interface of preceding layer is completely covered by the following layer.
44. The hybrid composite material for protection from projectiles (C2) as claimed in claim 33, wherein said thermoplastic composite (C22C) of back panel (C22) is fabricated using layers of films of said thermoplastic polymer (C22CP) and layers of fabric of synthetic fiber (C22CF) stacked alternately in ratio ranging from 4:1 to 1:1, wherein the layers of films of said thermoplastic polymer (C22CP) ranges in number from 50-600 and layers of fabric of synthetic fiber (C22CF) ranges in number from 50 to 150 to obtain said thermoplastic composite (C22C) with thickness in the range of 30 mm to 400 mm.
45. The hybrid composite material for protection from projectiles (C2) as claimed in claim 44, wherein said thermoplastic composite (C22C) of back panel (C22) has 91 layers of films of said thermoplastic polymer (C22CP) stacked alternately with 90 layers of fabric of said synthetic fiber (C22CF) to obtain said thermoplastic composite (C22C) with thickness in the range of 30 mm to 55 mm.
46. The hybrid composite material for protection from projectiles (C2) as claimed in claim 44, wherein said thermoplastic composite (C22C) of back panel (C22) has 116 layers of films of said thermoplastic polymer (C22CP) stacked alternately with 115 layers of fabric of said synthetic fiber (C22CF) to obtain said thermoplastic composite (C22C) with thickness in the range of 40 mm to 65 mm.
47. The hybrid composite material for protection from projectiles (C2) as claimed in claim 33, wherein said thermoplastic polymer (C22CP) for preparing said thermoplastic composite (C22C) of back panel (C22) is selected from group of high performance thermoplastic polymers comprising of polyether ketone ketone (PEKK), polyether ketone (PEK) , polyether ether ketone (PEEK), poly ether imide (PEI).
48. The hybrid composite material for protection from projectiles (C2) as claimed in claim 47, wherein said thermoplastic polymer (C22CP) for preparing said thermoplastic composite (C22C) of said back panel (C22) is polyether ketone ketone (PEKK) that has film thickness in the range of 0.05 mm to 0.5 mm, width in the range of 50 mm to 500 mm, density in the range of 0.75 g/cm3 to 2.5 g/cm3 , melting point in the range of 280°C to 372°C, film tensile strength in the range of 70 MPa to 150 MPa and film elongation to break that is greater than 150%.
49. The hybrid composite material for protection from severe impact (C2) as claimed in claim 48, wherein said polyether ketone ketone (PEKK) polymer used to prepare said thermoplastic composite (C22C) of said back panel (C22) has the following properties and specifications.
PROPERTY SPECIFICATION
Film thickness : 0.1 mm
Width : 100 mm
Density : 1.27 g/cm3
Melting point : 309 0C
Film tensile strength : 80 MPa
Film elongation to break : >150%
50. The hybrid composite material for protection from projectiles (C2) as claimed in claim 33, wherein said synthetic fiber (C22CF) for preparing said thermoplastic composite (C22C) of back panel (C22) is selected from group of high performance para aramid fiber , meta aramid fiber preferably high performance para aramid fiber.
51. The hybrid composite material for protection from projectiles (C2) as claimed in claim 50, wherein said high performance para aramid fiber has weave pattern selected from group of plain, twill, satin and basket, has width as required for application, weight in the range of 220 gsm to 480 gsm, thickness in the range of 0.25 mm to 0.75 mm, yarn code selected from AF1000 to 3000D, threads per inch have warp in the range of 15 to 20, weft in the range of 10 to 20, density in the range of 1.34 g/cm3 to 1.5 g/cm3, yarn has breaking tenacity in the range of 2.00 GPa to 3. 45 GPa, modulus in the range of 60 GPa to 140 GPa, and elongation in the range of 3.3% to 4.5%.
52. The hybrid composite material for protection from severe impact (C2) as claimed in claim 51, wherein said synthetic fiber (C22CF) for preparing thermoplastic composite (C22C) of back panel (C22) that is high performance para aramid fiber has the following properties and specifications.
PROPERTY SPECIFICATION
Weave pattern : Plain
Width : 1000 mm
Weight : 460 gsm
Thickness : 0.5 mm
Yarn Code : AF1000 – 3000D
Threads per inch- Warp : 17
Weft : 16
Density : 1.44 g/cm3
Yarn Properties- Breaking tenacity : 2.9 GPa
Modulus : 65 GPa
Elongation : 4.2%
53. The hybrid composite material for protection from projectiles (C2) as claimed in claim 33, wherein said adhesive (A) is selected from group of high temperature epoxy adhesive, polyimide adhesive, preferably a two - component epoxy adhesive (A) consisting of two components, a resin and a hardener, which are mixed together in proportions ranging from 4:1 to 1:1 preferably of 2:1 , to form a strong and durable bond in a period of time lesser than 36 hrs, preferably lesser than 24 hrs and is designed to cure at room temperature, without the need for additional heat or curing agents.
54. The hybrid composite material for protection from projectiles (C2) as claimed in claim 53, wherein said adhesive (A) has density in the range of 1.0 g/cm3 to 2.0 g/cm3, mixing ratio of said two components in the ratio of 4:1 to 1:1, pot life after mixing in the range of 10minutes to 15 minutes, lap shear strength in the range of 10 MPa to 25 MPa, flexural strength in the range of 35 MPa to 60 MPa, tensile strength in the range of 15 MPa to 35 MPa, compressive strength in the range of 30 MPa to 50 MPa, hardness in the range of 65 shore D to 85 shore D and water absorption (24 hours) in the range of 0.2% to 0.4%.
55. The hybrid composite material for protection from projectiles (C2) as claimed in claim 54, wherein said adhesive (A) has the following properties and specifications:

PROPERTY SPECIFICATION
Density : 1.55 g/cm3
Mixing ratio : 2:1
Pot life after mixing : 10-15 minutes
Lap shear strength : 15 MPa
Flexural strength : 43 MPa
Tensile strength : 25 MPa
Compressive strength : 40 MPa
Hardness : 75 shore D
Water absorption (24 hours) : 0.3%
56. The hybrid composite material for protection from projectiles (C2) as claimed in claim 33, wherein said lightweight material frame (C26) is made of aluminium.
57. A method for fabrication of hybrid composite material with high impact resistance for protection from projectiles (C2) wherein said method comprises of steps of:
- preparing one of the two surfaces of thermoplastic composite (C22C) by cleaning with cleaning solvents to include acetone , roughening of said surface with roughening tools to include fine grain sandpaper and further cleaning with solvents to include ethanol;
- preparing two - component epoxy adhesive by mixing first component and second component of said adhesive (A) in desired ratio in the range of 4:1 to 1:1, preferably 2:1;
- applying a thin layer of the prepared adhesive (A) over said prepared surface of thermoplastic composite (C22C);
- placing of ceramic tiles of lightweight ceramic composite ( C21C) aligned laterally to each other, using bonding processes preferably by adhesive bonding using adhesive (A), preferably the two-component epoxy adhesive, above said prepared surface of thermoplastic composite (C22C) to obtain one layer of lightweight ceramic composites (C21CL) bonded to said thermoplastic composite (C22C);
- placing of weights on said layer of lightweight ceramic composite (C21Cl) bonded to said thermoplastic composite (C22C), to allow curing;
- repeating said steps of applying thin coat of prepared adhesive (A) on the top surface of the previous layer of lightweight ceramic composites (C11CL), placing ceramic tiles over the surface of previous layer and curing using weights to obtain another layer of the lightweight ceramic composites (C21CL), while maintaining the placing on previous layer of ceramic composites (C21CL) in a staggered manner ;
- layering further of the ceramic tiles to obtain the desired number of layers of the lightweight ceramic composite (C21CL) for the front panel (C21) to obtain the desired configuration of the hybrid composite material for protection from projectiles (C2) and
- confining the layers of lightweight ceramic composite (C21CL) of front panel (C21) of the hybrid composite material obtained as above by providing a confining sheet (C25) selected from group comprising of polycarbonate covering , polymethyl methacrylate covering to include polycarbonate covering over the exposed surface of front panel (C21) and providing lightweight material frame (C24) along with packing material to include elastomer sheet for packing purpose (C26) such as silicone rubber sheet and packaging foam material (C27) such as extended polyethylene foam for tight packing around the perimeter of the hybrid composite for protection from projectiles (C2) to ensure tight packing.
58. The method for fabrication as claimed in claim 57, wherein said thermoplastic composite (C22C) of back panel (C22) of hybrid composite material with high impact resistance for protection from projectiles (C2) is fabricated by a process the steps of which comprise of:
- preparing of films of thermoplastic polymer (C22CP) by cutting it into strips of desired width preferably 100 to 500 mm and desired length;
- preparing of fabric of synthetic fiber (C22CF) by cutting said fabric into desired shape and size for application purpose;
- preparing a layer of thermoplastic polymer (C22CP) film by placing said strips of said thermoplastic polymer (C22CP) side by side laterally to obtain a layer of said thermoplastic polymer (C22CP) of a desired size for application purpose;
- stacking of said layers of fabrics of synthetic fiber (C22CF) and said layers of thermoplastic polymer (C22CP) film alternately to obtain stacked layers (V7);
- placing said stacked layers (V7) of said two materials in a vacuum bag and vacuum bagging or vacuuming said stacked layers (V7) by drawing out the air to compress said layers together to remove any trapped air;
- loading the vacuumed layers of the said two materials in the vacuum bag into an autoclave for the curing cycle;
- heating and pressurizing the autoclave to desired temperature ranging between 250 0C to 400 0C and pressure conditions 4 bar to 10 bar;
- curing under said desired high temperature and pressure conditions for a period of time in the range of 4hrs to 8 hrs while keeping the desired temperature and pressure conditions controlled and monitored throughout the process to ensure the proper autoclaving and curing of the vacuumed layers of the two materials to obtain a single autoclaved product;
- cooling said autoclave to room temperature after completion of curing process to prevent any damage to said autoclaved product and
- removing said autoclaved product from said autoclave and trimming any excess material by waterjet cutting.
59. The method for fabrication as claimed in claim 58, wherein said method of vacuum bagging of the layers of the two material components of thermoplastic composite (C22C) of back panel (C22) has steps comprising of:
- embedding of thermocouple (V2) within said stacked layers (V7) of said two material components of thermoplastic composite (C22C) in vacuum bag (V) for monitoring the temperature;
- pulling bagging material of the vacuum bag (V) tightly against said stacked layers (V7) of said two material components of thermoplastic composite (C22C) to ensure good contact and removal of any wrinkles or folds in said layers of the two materials;
- removing air from the material of said stacked layers (V7) of components of thermoplastic composite (C22C) placed inside said vacuum bag (V) by using a vacuum pump thus creating a pressure differential between the inside of the bag (V) and the outside, which compresses the layers of the two materials together and removes any trapped air and
- sealing of said vacuum bag (V) after the vacuum is established by using sealing tapes to include GS Tape and Kapton Tape to prevent any air from leaking back into said bag (V).
60. The method for fabrication as claimed in claim 58, wherein the conditions for autoclaving is performed with conditions of holding temperature ranging from 250°C to 400°C, heating rate is in the range of 1°C to 5°C, holding time is in the range of 30 minutes to 120 minutes, cooling rate is in the range of 2°C to 8 °C and pressure is maintained in the range of 4 bars to 10 bars.
61. The method for fabrication as claimed in claim 60, wherein the autoclaving is performed with conditions as mentioned below:
CONDITION VALUE
Holding temperature : 310 °C
Heating rate : 3°C
Holding time : 60 minutes
Cooling rate : 5°C
Pressure : 8 bars
62. The hybrid composite material for protection from projectiles (C2) as claimed in claim 33, wherein said hybrid composite material (C2) has practical applications in various fields to include mining industry, aviation, space and civil infrastructures, oil and gas industry etc.

Dated this the 28th day of March 2024
________________________
Sunita K. Sreedharan
IN/PA-310
of SKS Law Associates
Attorney for the Applicant

To
The Controller of Patents,
The Patent Office, Chennai