DESC:FIELD OF INVENTION
[0001] The application is based on and claims priority from Indian Provisional Application 202521002084 filed on 09th January 2025, the disclosure of which is hereby incorporated by reference herein. The present application relates to an optical fibre cable (OFC) and more specifically relates to an advanced liquid crystal polymer (LCP) based composite rod which acts as a superior strength element to the OFC application, the preparation and the unique mechanical properties of the composite rod thereof.
BACKGROUND
[0002] Optical Fibre Cables (OFCs) are an integral component in the modern communication infrastructure, facilitating the transmission of digital data in the form of light pulses across vast distances at high speeds. These cables, which consist of numerous optical fibres bundled together within a protective plastic coating, are essential for a range of applications including telecommunications, broadband, and data networking. Their ability to provide secure and cost-effective data transmission has led to their widespread adoption in both domestic and industrial sectors.
[0003] The deployment of OFCs, whether underground or aerially, necessitates that they possess high strength and flexibility to withstand various environmental conditions and physical stresses. The rapid advancement in data transmission technologies, particularly the development of 6th Generation (6G) networks, has further accentuated the need for innovative OFC designs with superior mechanical properties. To meet these demands, the industry has traditionally relied on the inclusion of fibre-reinforced plastic (FRP) rods within the cables to enhance their mechanical strength and durability. These rods improve the cables' resistance to bending, crushing, and other physical stresses.
[0004] Historically, Glass Fibre Reinforced Plastic (GFRP) and Aramid Fibre Reinforced Plastic (ARP) rods have been used as strength members in the OFCs. GFRP rods were initially employed to achieve the necessary mechanical properties for various cable designs, including central strength member (CSM) and sheath-embedded designs. The introduction of ARP rods marked a significant advancement, particularly for micro duct cables, due to their lightweight characteristics which facilitated easier installation and handling.
[0005] Despite these advancements, the industry continues to face challenges in meeting the growing demand for faster and more reliable data transmission, especially in the context of 6G networks. One of the primary issues is the need for OFCs with superior fatigue resistance and mechanical properties, which must be achieved within the constrained design possibilities imposed by highly urbanized areas. Manufacturers have attempted to address these challenges by reducing the size of the cabling to minimize bulk and facilitate easier installation. However, this approach often results in a compromise in signal quality, which is detrimental to the overall performance of the network.
[0006] Thus, it is desired to address the above-mentioned disadvantages or other shortcomings or at least provide a useful alternative.
OBJECT OF THE INVENTION
[0007] The principal object of the invention herein is to provide details of unique ingredients and formulations used for the fabrication of an aromatic polyester-based fiber having a liquid crystal polymer nature (AP-LC) reinforced composite rod.
[0008] Another object of the invention herein is to provide an OFC having the AP-LC reinforced composite rod.
[0009] Yet another object of the invention herein is to provide the basic polymeric structure of the AP-LC and the thermoset resin used for the fabrication of the AP-LC reinforced composite rod.
[0010] Yet another object of the invention herein is to provide unique mechanical properties of the AP-LC composite rod compared to the existing GFRP, ARP, and metals.
[0011] Yet another object of the invention herein is to provide that the combination of the proposed fiber and resin influences the mechanical property uniqueness of the product.
SUMMARY
[0012] In an aspect, the objects are achieved by providing a composite rod for protecting an OFC from external stresses. The composite rod includes a reinforcement phase, including an AP-LC fiber having a liquid crystal polymer nature, and a matrix phase, including a thermoset resin, where the liquid crystal fiber includes an aromatic polyester-based fiber having a liquid crystal polymer nature. The composite rod is positioned in the periphery of or embedded within an outer sheath of the OFC to protect the OFC from external stresses.
[0013] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF FIGURES
[0014] The invention is illustrated in the accompanying drawings, where like reference letters indicate corresponding parts. The embodiments will be better understood from the following description with reference to the drawings.
[0015] FIG. 1 is a schematic diagram that illustrates the constituents of the proposed AP-LC reinforced composite rod for the OFC according to the embodiments disclosed herein.
[0016] FIG. 2 is a schematic diagram that illustrates the typical OFC cross-section, including the AP-LC reinforced composite rod as a strength element positioned in different positions of the OFC according to the embodiments disclosed herein.
[0017] FIG. 3 is a schematic diagram that illustrates the basic molecular structure of the fiber used for the AP-LC reinforced composite rod according to the embodiments disclosed herein.
[0018] FIG. 4 is a schematic diagram that illustrates the basic molecular structure of the thermoset resin used for the AP-LC reinforced composite rod according to the embodiments disclosed herein.
[0019] FIG. 5 is a schematic diagram that illustrates the typical comparison between the AP-LC reinforced composite rod and the GFRP rods according to the embodiments disclosed herein.
[0020] FIG. 6 is a schematic diagram that illustrates the typical structural comparison of amorphous fiber reinforced composite and liquid crystal fiber reinforced composite according to the embodiments disclosed herein.
[0021] FIG. 7 is a schematic diagram that illustrates the typical appearance difference of the AP-LC reinforced composite rod, ARP & GFRP according to the embodiments disclosed herein.
[0022] FIG. 8 is a graph that illustrates the tensile properties of the AP-LC reinforced composite rod according to the embodiments disclosed herein.
DETAILED DESCRIPTION OF INVENTION
[0023] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments. The term “or” as used herein, refers to a non-exclusive or, unless otherwise indicated. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein can be practiced and to further enable those skilled in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0024] As is existing in the field, embodiments can be described and illustrated in terms of blocks which carry out a described function or functions. These blocks, which can be referred to herein as managers, units, modules, hardware components or the like, are physically implemented by analog and/or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits and the like, and can optionally be driven by firmware and software. The circuits may, for example, be embodied in one or more semiconductor chips, or on substrate supports such as printed circuit boards and the like. The circuits constituting a block can be implemented by dedicated hardware, or by a processor (e.g., one or more programmed microprocessors and associated circuitry), or by a combination of dedicated hardware to perform some functions of the block and a processor to perform other functions of the block. Each block of the embodiments can be physically separated into two or more interacting and discrete blocks without departing from the scope of the disclosure. Likewise, the blocks of the embodiments can be physically combined into more complex blocks without departing from the scope of the disclosure.
[0025] The accompanying drawings facilitate understanding of various technical features. The disclosed embodiments are not limited to these drawings and should be interpreted to include any alterations, equivalents, and substitutes. Terms like "first" and "second" are used for distinction and do not limit the elements.
[0026] Throughout the specification, the definitions of the various terms used in the embodiments are as follows:
[0027] Composites: A composite material includes two or more chemically different constituents with distinct interphases between them. They have different properties and are categorized into fiber-reinforced and particle-reinforced composites. The proposed solution uses fiber-reinforced composites (e.g., ARP, FRP, AP-LC reinforced composite rod).
[0028] Liquid Crystal Polymer (LCP) / Liquid Crystal Fibers: The LCPs are polymers with the property of liquid crystals, usually containing aromatic rings. The LC is a state of matter whose properties are between those of conventional liquids and those of solid crystals. The molecules align in an ordered layered fashion. The liquid crystal fibers are fibers made from liquid crystalline polymers or other materials that exhibit liquid crystalline phases. These fibers inherit the unique properties of liquid crystals, combining the mechanical strength of crystalline materials with the flexibility and processability of polymers. During fiber spinning or extrusion, the liquid crystalline molecules align along the fiber axis. This alignment enhances mechanical properties such as tensile strength and stiffness. They are lightweight yet extremely strong and durable and are often compared to materials like Kevlar, which is also derived from liquid crystalline polymers.
[0029] Thermoset Resin: It is a type of polymer that hardens irreversibly when exposed to heat, radiation, etc. The formation of polymer cross-linking during the reaction time makes the material an infusible, hard material. This material is used in composite production to improve the mechanical properties and structural stability.
[0030] Cross-Linking Agent: It is a process where a polymer chain on the shell material is linked to another polymer chain through a chemical bond. Cross-linking provides better mechanical strength to the shell materials. There are some catalysts that can improve or speed up the cross-linking process; such materials are called cross-linking agents.
[0031] Releasing Agent: It is added during the process for lubrication as well as the easy mold release of materials.
[0032] The OFC includes several to hundreds of optical fibres bundled together and encased in a protective plastic jacket. These cables transmit digital data as light pulses over long distances at high speeds. For this purpose, they need to be installed or deployed either underground or aerially. Standalone fibres cannot be buried or hanged, so fibres are bunched together as cables for the transmission of data. To improve the mechanical strength and durability of the cable, fibre-reinforced plastic (FRP) rods are embedded in the jacket. These rods enhance the cable's resistance to bending, crushing, and other physical stresses. The FRP rods are created by impregnating fibres with a thermoset resin matrix. The resin-impregnated fibres are then drawn through a heated die in a process called pultrusion, which shapes and cures the material to form uniform rods. Afterward, the pultruded rods are cooled to retain their final form. The FRP rods are non-corrosive, lightweight, and can be altered to specific strength and stiffness, making them ideal for manufacturing and customization to suit performance requirements.
[0033] High-strength FRP rods are dielectric composite cable-strength reinforcements placed within the OFCs, i.e., embedded in the jacket to improve the mechanical strength and durability of the OFC. They provide high tensile strength to the cables, ensuring they remain robust throughout their shelf lives, and also enhance the cable's resistance to bending, crushing, and other physical stresses. These rods are strategically positioned both at the center and periphery of the OFCs. During the OFC installation, the FRP rods reduce tension on signal-carrying conductors. Their splice-free dimensions simplify cable laying and enhance productivity. The FRP rods prevent sagging in aerial installations by absorbing load with inherent stiffness. Compared to steel and aluminum, the FRP rods are lightweight, with 75% less weight than steel and 30% less weight than aluminum. The result exhibits enhanced reliability, flexibility in design, increased productivity, and reduced downtime for FRP-strengthened OFCs. The FRP rods embedded in the OFCs exemplify strength reinforcement, cost-effectiveness, and improved performance in optical communication networks.
[0034] Micro duct/Micro-sized cables are next-generation OFCs that fit in smaller ducts than a flat ribbon cable and offer high fibre density with a capacity of up to 864 counts of optical fibre. IBR cable is ideal for use in micro ducts, especially useful in crowded urban areas such as the UK market. The usage of the IBR cables for data centres interconnect networks empowers data centres to quickly deploy fibre networks to efficiently address current and future capacity demands while reducing their storage and shipping expenses. The IBR cables (Micro-sized) are better equipped to support the unique capacity and scalability needs of these networks. They are flexible and can easily bend as per the available space inside a cable, ensuring a smaller diameter when compared to the existing loose tube or flat ribbon cables. The development of AP-LC reinforced composite rods for the OFCs accelerates this development as a breakthrough.
[0035] In an embodiment to address the existing issues, an AP-LC reinforced composite rod made with LCP fibres and pultrusion resin is proposed, which offers enhanced strength and flexibility. It has 40% higher tensile strength than ARP and 70% higher than FRP, making it ideal for micro-sized IBR cables.
[0036] Embodiments disclosed herein provide a novel composite rod, the AP-LC Fibre reinforced composite rod, designed specifically for OFCs. It is manufactured using an advanced aromatic polyester-based fibre having a liquid crystal polymer (AP-LC) skeleton as the reinforcement phase and the thermoset resin with the chemistry of polyol and diisocyanate as the matrix phase through a proprietary manufacturing process. The fibre and resin undergo a temperature treatment that aligns the LCP fibres and cross-links the resin, creating a structurally superior rod with enhanced strength and flexibility within its smaller dimension. The attributes of the aromatic polyester fibre, such as excellent mechanical properties, property retention over a wide range of temperatures, improved resistance to fibre-to-fibre abrasion and wear from bending, excellent chemical resistance, and low moisture pickup, carry over to the fibre. By investigating these unique properties, the AP-LC Fibre reinforced composite rod is invented and manufactured for the telecommunication industry. The AP-LC composite rod demonstrates a tensile strength 40% higher than ARP and 70% higher than FRP, making it a highly effective replacement for GFRP and ARP rods in telecommunication applications. The novel mechanical properties of the proposed composite rod make it suitable for micro-sized cables where strength-to-weight ratio and size plays a key role in performance.
[0037] Referring now to the drawings, and more particularly to FIGS. 1 through 8, where similar reference characters denote corresponding features throughout the figures, there are shown preferred embodiments.
[0038] FIG.1 is a schematic diagram that illustrates the constituents of the proposed AP-LC reinforced composite rod (100) for the OFC according to the embodiments disclosed herein. The reinforcement phase of the AP-LC reinforced composite rod (100) is an AP-LC fibre (101) which is the aromatic polyester-based fibre having liquid crystal nature. The matrix phase is a thermoset resin (102) derived from diisocyanate and polyol components. The AP-LC reinforced composite rod (100) is made by the combination of the above fibre and resin. The AP-LC reinforced composite rod (100) is made by a pultrusion process which produces a composite rod having continuous cross section. The ingredients used for the AP-LC reinforced composite rod (100) are aromatic polyester reinforced fibre (101) which is a liquid crystal polymer, Thermoset resin (102) made of diisocyanate and polyol and cross linking agents. The pultrusion process includes pulling the AP-LC fibres through a resin bath containing the thermoset resin, followed by shaping and curing the composite in a heated die. This ensures uniform distribution of the resin and optimal alignment of the fibres, resulting in enhanced mechanical properties such as tensile strength and stiffness. The liquid crystal nature of the AP-LC fibre contributes to the high thermal stability and chemical resistance of the composite rod.
[0039] In an embodiment, Table I illustrates the content quantity of the AP-LC fibre (101) and thermoset resin (102) used in the preparation of the AP-LC reinforced composite rod (100). The table specifies the weight percentage of each component, ensuring the optimal balance between the reinforcement and matrix phases. For instance, the AP-LC fibre (101) content may range from 60% to 70% by weight, while the thermoset resin content may range from 30% to 40% by weight. This ratio is archives the desired mechanical properties and ensuring the composite rod's performance in various applications. Additionally, the table may include details on the fibre diameter and resin viscosity, which are important parameters for the pultrusion process.
Constituent Content quantity
Aromatic Polyester reinforced Liquid Crystal Fibre (AP-LC fibre) (101)
(Reinforcement phase) 60-70%
Thermoset Resin (102) (Matrix Phase) 30-40%
Table I
[0040] In an embodiment, Table II illustrates the matrix composition used in the preparation of the AP-LC reinforced composite rod (100).
Matrix Composition
Thermoset resin 96%
Cross linking agent 01 & 02 0.8-1%
Cross linking agent 03 1.8-2%
Releasing agent 0.8-1.2%
Table II
[0041] In an embodiment, polyurethane acrylate resins are cured using thermal methods, where the acrylate groups undergo radical polymerization. This is the primary reaction that hardens the resin and forms a crosslinked network. The isocyanate reacts with the polyol to form a polyurethane backbone. The terminal groups of the polyurethane react with acrylic monomers (such as hydroxyethyl acrylate) to create acrylate-functionalized polyurethane. The radical polymerization is initiated by heat, which activates the initiators present in the resin formulation. This process results in a highly crosslinked polymer network that provides excellent mechanical properties and chemical resistance. The curing process can be controlled by adjusting the temperature and duration, ensuring complete polymerization and optimal performance of the composite rod.
[0042] In an embodiment, in thermal curing, the presence of a heat-activated catalyst can initiate the process. In the proposed composition, 3 such catalysts are being used called cross linking agents. The examples of the cross linking agent 01 can include but not limited to Peroxide-1 (Tertiary Butyl Peroctoate). The examples of the cross linking agent 02 can include but not limited to Peroxide-2 (Tertiary Butyl Peroxy Neodecanoate). The examples of the cross linking agent 03 can include but not limited to Peroxide-3 (11-di-(t-Butyl-Peroxy) Cyclo Hexane). The examples of the releasing agent can include but not limited to PAT (blend of organic fatty acids esters & amine). These catalysts are selected based on their decomposition temperature and efficiency in generating free radicals, which are essential for initiating the polymerization process. The use of multiple cross linking agents ensures a robust and uniform curing process, enhancing the mechanical properties and thermal stability of the composite rod. The releasing agent, PAT, facilitates the removal of the cured composite from the mold, preventing adhesion and ensuring a smooth surface finish.
[0043] In an embodiment, the reaction mechanism can be summarized as follows:
[0044] Initiation: The photo initiator absorbs UV light and generates free radicals. These free radicals are highly reactive species that initiate the polymerization process by attacking the double bonds present in the acrylate groups. The absorption of UV light by the photo initiator typically occurs at specific wavelengths, which are chosen based on the absorption spectrum of the initiator to maximize efficiency. The generation of free radicals sets off the chain reaction necessary for polymer formation.
[0045] Propagation: These free radicals attack the double bonds of the acrylate groups, leading to the formation of a polymer chain. The free radicals add to the double bonds, creating new radical sites that continue to react with other acrylate monomers, thus propagating the chain reaction. This step includes the continuous addition of monomer units to the growing polymer chain, resulting in a significant increase in molecular weight. The rate of propagation is influenced by factors such as the concentration of monomers and the presence of any inhibitors or retarders.
[0046] Termination: The polymer chains either combine or react with other free radicals, thus stopping the polymerization process and solidifying the resin into a thermoset material. Termination can occur through various mechanisms, including combination, where two growing polymer chains join together, or disproportionation, where a hydrogen atom is transferred from one chain to another. The termination step determines the final molecular weight and the properties of the polymer. The solidification of the resin into a thermoset material results in a network structure that provides mechanical strength and thermal stability.
[0047] The following reaction illustrates the formation of urethane:
[0048] Diisocyanate + Polyol ? Urethane Linkage (NHCOO). The reaction between diisocyanate and polyol includes the nucleophilic attack of the hydroxyl groups of the polyol on the isocyanate groups of the diisocyanate, forming urethane linkages. This reaction is typically exothermic and can be catalyzed to increase the reaction rate. The resulting urethane linkage is characterized by its strong covalent bonds, which contribute to the durability and flexibility of the final polymer.
[0049] The following reaction illustrates the formation of acrylation:
[0050] Urethane + Acrylic Monomer ? Urethane Acrylate Resin. In this reaction, the urethane groups react with acrylic monomers to form urethane acrylate resins, which combine the properties of both urethanes and acrylates. The acrylation process includes the addition of acrylic monomers to the urethane backbone, enhancing the resin's ability to undergo radical polymerization. The urethane acrylate resin formed is known for its excellent adhesion, chemical resistance, and mechanical properties, making it suitable for various applications.
[0051] The following reaction illustrates the radical polymerization (in the presence of thermal initiators):
[0052] RCH=CH2 + Initiator Radical ? RCHCH2 [polymerized]. The thermal initiators decompose upon heating to generate free radicals, which then initiate the polymerization of the monomer RCH=CH2. The polymerization process includes the successive addition of monomer units to the growing polymer chain, resulting in a high molecular weight polymer. The choice of thermal initiator and the polymerization conditions, such as temperature and concentration, play a significant role in determining the kinetics and the final properties of the polymer.
[0053] In an embodiment, during curing, the resin (102) interacts with the reinforcement (101), and the resulting crosslinked structure ensures that the composite material has a strong cohesive bond between the resin (102) and the AP-LC Fiber reinforcement (101), improving the overall mechanical properties. The interaction between the resin and the reinforcement is facilitated by the chemical compatibility and the surface treatment of the fibers, which enhances adhesion. The curing temperature of composites directly affects the mechanical properties, performance, and processing efficiency of the final composite material. The curing refers to the process where the resin or matrix material undergoes chemical changes, typically through crosslinking, to form a hardened structure. The curing temperature plays a significant role in various aspects of this process, including reaction kinetics, the degree of cure, and the final material properties. The processing temperature range for the AP-LC reinforced composite rod (100) is between 80-250°C (The temperature changes with different processing zones) in the thermal pultrusion process. The temperature profile is carefully controlled to ensure optimal curing and to prevent thermal degradation of the resin and fibers.
[0054] In an embodiment, the AP-LC reinforced composite rod (100) is made by the above disclosed ingredients and formulation through the pultrusion process. The thermal pultrusion process for manufacturing the composite rods is a continuous process that includes pulling raw materials through a heated die to form a composite material with a constant cross-section. The same process is incorporated to produce AP-LC reinforced composite rod (100). The AP-LC fiber (101) passes through the heated barrels to remove the oil content/volatile content that mitigate the interface nature compatibility with matrix & property of the final product. This preheating incorporates a temperature range of 190-250°C. The preheating step removes any contaminants that could affect the bonding between the fibers and the resin. After removing the volatile oil contents, the fibers then pass through the resin bath containing the thermoset resin (102) made by the diisocyanate & polyol-based acrylate resin. This ensures that the fibers are fully coated and bonded with the resin. The impregnated AP-LC fiber (101) with the thermoset resin (102) then undergoes a partial curing stage, then directly passes through the main temperature zone provided a temperature of 120-140°C where the polymer cross-linking and hardening of thermoset resin (102) happens. The partial curing stage allows for initial cross-linking, which helps in maintaining the fiber alignment and distribution within the resin matrix. Pultrusion Die: The preformed fibers are pulled through a heated die where the resin undergoes a curing process. The heat from the die initiates a chemical reaction that hardens the resin, bonding the fibers together to form a solid composite material. The cured rigid AP-LC fiber reinforced composite rod (100) then passes through the final stage heating zone of temperature 140-170°C to ensure the complete curing of thermoset resin (102) with the AP-LC fiber (101). The final heating zone ensures that any remaining uncured resin is fully cross-linked, resulting in a composite rod with optimal mechanical properties and thermal stability.
[0055] FIG. 2 is a schematic diagram that illustrates the typical OFC cross section including the AP-LC reinforced composite rod (100) as strength element positioned in different positions of the OFC according to the embodiments disclosed herein. In an embodiment, the components in the FIG. 2 are illustrated using the following reference numerals: High Density Polyethylene (HDPE) jacket (201), AP-LC reinforced composite rod (100), Rip cord (202), Optical fibres (203), Water blocking tape (204). The OFC includes a plurality of one or more optical fibres (203) and a buffer tube enclosing the one or more of optical fibres (203). The buffer tube is typically made of a polymer material that provides additional protection and isolation for the optical fibers (203). The OFC also includes one or more of the AP-LC reinforced composite rods (100) positioned in the periphery/embedded between High Density Polyethylene (HDPE) jacket (201) of the OFC. The HDPE jacket serves as an outer protective layer that shields the internal components from environmental factors such as moisture, UV radiation, and mechanical impacts. As illustrated in the FIG. 2, the typical OFC cross section includes the AP-LC reinforced composite rod (100) as strength element having diameter range (0.4-1mm) in its peripheral region. This diameter range is optimized to balance the mechanical strength and flexibility required for various installation scenarios.
[0056] In an embodiment, the AP-LC reinforced composite rod (100) in the peripheral participating in the OFC protection along with PE sheathing material (HDPE) (201). The composite rod is strategically positioned to enhance the overall durability of the cable, ensuring it can withstand harsh environmental conditions. It protects the OFC from external stresses and bending failures and resists the longitudinal higher load applications. The high tensile strength of the AP-LC reinforced composite rod (100) allows it to absorb and distribute mechanical loads effectively, preventing damage to the optical fibers. The AP-LC reinforced composite rod (100) in the center provides the overall structural stability & strength to OFCs. This central positioning ensures that the cable maintains its integrity and performance even under significant mechanical stress. The AP-LC reinforced composite rod (100) acts as the versatile protecting element having high strength with less weight & dimension. It replaces all other existing composite rods with superior strength in lesser surface area for OFCs because it is providing an extra high tensile strength & flexibility. This innovation allows for more compact cable designs without compromising on performance.
[0057] FIG. 3 is a schematic diagram that illustrates the molecular structure of the fibre (101) used for the AP-LC reinforced composite rod (100) according to the embodiments disclosed herein. The molecular structure of the fiber is characterized by a highly ordered arrangement of polymer chains, which contributes to its exceptional mechanical properties. FIG. 4 is a schematic diagram that illustrates the basic molecular structure of the thermoset resin (102) used for the AP-LC reinforced composite rod (100) according to the embodiments disclosed herein. The thermoset resin is formulated to provide a robust matrix that binds the fibers together, enhancing the overall composite strength. In an embodiment, the FIG. 3 depicts the molecular structure of liquid crystal polymer and the FIG. 4 depicts the structure of polyurethane polymer. The aromatic polyester fibers are known for their high thermal stability and resistance to chemical degradation, making them suitable for demanding applications. The thermoset resin, once cured, forms a rigid and durable matrix that supports the fibers and maintains the structural integrity of the composite rod.
[0058] FIG. 5 is a schematic diagram that illustrates the typical comparison between the AP-LC reinforced composite rod (100) and the GFRP rods (500) according to the embodiments disclosed herein. The FIG. 5 illustrates the basic structure of a composite rod providing the comparison between glass fibre and the liquid crystal fibre and the composite rod made of these 2 fibres. The comparison highlights the differences in mechanical properties, such as tensile strength, modulus of elasticity, and weight, between the two types of fibers. In an embodiment, the comparison of the features in the FIG. 5 are illustrated using the following reference numerals: Chain arrangements in Amorphous Fibre filament (Glass) (501), Chain arrangements in Crystalline Fibre Filaments (AP-LC) (502), Reinforcement phase in GFRP- Glass Fibre (503), Reinforcement phase in AP-LC reinforced composite rod - AP-LC Fibre (101), Thermoset resin matrix (102), GFRP Rod (500), AP-LC reinforced composite rod (100). The amorphous structure of glass fibers results in lower tensile strength and higher brittleness compared to the crystalline structure of AP-LC fibers. The embodiment of Table III illustrates the typical structural comparison of the AP-LC reinforced composite rod (100) and the GFRP rods (500). This table provides quantitative data on the mechanical properties, such as tensile strength, elongation at break, and modulus of elasticity, demonstrating the superior performance of the AP-LC reinforced composite rod (100).
Features AP-LC reinforced composite rod (100) GFRP rod (500)
Structural alignment of the fibre molecules Chain arrangements in Crystalline manner- Perfectly aligned (502) Chain arrangements in amorphous manner (501)
Reinforcement phase AP-LC Fibre (101) Glass Fibre (503)
Matrix phase Thermoset resin matrix (102) Thermoset resin matrix (102)
Table III
[0059] In an embodiment, the mechanical properties of composite rods are highly dependent on the fibre resin compatibility and the orientation of fibres. If the orientation of fibres is unidirectional with uniform alignment, it provides higher mechanical properties to the final product. The perfectly aligned crystalline structure (502) of the LCP fibre (101) provides high mechanical performance to the AP-LC reinforced composite rod (100). The alignment ensures that the load is distributed evenly across the fibres, minimizing weak points and enhancing the overall strength. Additionally, the uniform alignment reduces the likelihood of micro-cracks forming under stress, which can significantly improve the durability and lifespan of the composite rod. The fibre-resin interface is used, as a strong bond between the two materials ensures efficient load transfer and prevents delamination.
[0060] In an embodiment, numerous high-performance fibres are available on the market today. Performance and price necessitate trade-offs in choosing between these fibres for specific applications. The AP-LCP fibre (101) is a strong candidate for composite applications in which a combination of properties is required. High strength to weight ratio, flexibility & creep resistance, low coefficient of thermal expansion, abrasion resistance & heat stress bending resistance are some of its key attributes. For the optic fibre cable application, a reinforcement element should have these mentioned properties. As FRPs are versatile materials, the AP-LC reinforced composite rod (100) introduces a new avenue in the strength element research & development. The fibre's low thermal expansion ensures dimensional stability under varying temperatures, which is used for maintaining the integrity of optic fibre cables. Furthermore, its abrasion resistance makes it suitable for harsh environments where mechanical wear is a concern.
[0061] FIG. 6 is a schematic diagram that illustrates the typical structural comparison of amorphous fibre reinforced composite and liquid crystal fibre reinforced composite according to the embodiments disclosed herein. The diagram highlights the differences in molecular alignment and the resulting mechanical properties. Amorphous fibres tend to have a random molecular arrangement, leading to lower strength and stiffness compared to liquid crystal fibres. The liquid crystal fibres exhibit a highly ordered structure, which translates to superior mechanical performance. This comparison underscores the advantages of using liquid crystal fibres in applications requiring high strength and durability.
[0062] In an embodiment, the AP-LC fibers (101) are a type of material derived from special polymers which exhibit unique properties due to their perfectly aligned molecular structure, i.e., they are semicrystalline materials (having both crystalline & amorphous regions). Materials with a mix of crystalline and amorphous regions tend to be more flexible. The crystalline regions provide strength while the amorphous regions allow for flexibility. Proper alignment of molecules can enhance this balance. The mechanical properties of the composites are highly dependent on the molecular arrangements of constituents & their compatibility. The thermoset polymers themselves are highly strong & stiff due to their unique cross-linking capacity. The perfectly aligned liquid crystal structure of the fibre also gives comparatively high modulus & strength to the composites. The perfectly packed arrangements give unique structural properties to the composite rod compared to other existing mechanisms. These oriented domains lead to anisotropic behavior, meaning the material exhibits different properties in different directions, which can be advantageous in specific applications.
[0063] In an embodiment, as illustrated in FIG. 6, the crystalline alignments provide uniform space occupancy for the matrix. This uniformity provides uniform distribution when under stress conditions and avoids unwanted stress points. It is stronger and more durable than Aramid fibers. It ensures stable performance in demanding long-term or extreme environments. When molecules are perfectly aligned, the intermolecular forces (like van der Waals forces) are optimized. This optimization allows the material to deform under stress and return to its original shape, contributing to its flexibility. The uniform stress distribution also minimizes the risk of catastrophic failure.
[0064] In an embodiment, the mechanical properties of composite rods are highly dependent on the fibre resin compatibility and the orientation of fibres. If the orientation of fibres is unidirectional with uniform alignment, it provides higher mechanical properties to the final product. The perfectly aligned crystalline structure of these fibres provides high mechanical performance to the composite rod. The perfectly aligned structure at the molecular level contributes to its unique performance. Its unique performance is attributed to the strong composite structure featuring a robust crystalline backbone and highly efficient cross-links in the thermoset resin, setting it apart from others. This combination results in a material that is not only strong but also resistant to environmental degradation, such as UV exposure and chemical attack.
[0065] FIG. 7 is a schematic diagram that illustrates the typical appearance difference of AP-LC reinforced composite rod (100), ARP (700), and GFRP (500) according to the embodiments disclosed herein. The following is the color description: AP-LC reinforced composite rod (100) (Light Cream color in appearance), ARP rod (700) (Yellow color in appearance), and GFRP rod (500) (Greenish white/White color in appearance). The color difference depends on the fibre resin formulation and the overall process conditions provided for the production. The appearance can also be indicative of the material's properties, with certain colors reflecting specific additives or treatments used during manufacturing.
In an embodiment, the AP-LC fibre (101) of linear density between 1100-2000 dtex is used as the fibre backbone, and the thermoset resin (102), which is derived from polyol & diisocyanate, is used as the matrix material. The AP-LC reinforced composite rod (100) is prepared by referring to the specific resin formulation & fibre combination. The impregnated fibre in the thermoset resin (102) is then pulled through a heated die at a specific temperature & line speed. The pultruded rods then undergo various tests such as mechanical & thermal. The ARP (700) made of this same process and the GFRP (500) made of the ultraviolet (UV) pultrusion process are also subjected to such tests for the comparison study as disclosed in the following embodiments. The specific temperature and line speed influences the final properties of the composite rod, ensuring optimal curing and alignment of the fibres.
[0066] In an embodiment, the prepared AP-LC reinforced composite rod (100), the GFRP (500), and the ARP (700) of the same dimensions undergo the following tests: tensile strength & modulus, elongation at break, minimum bend test, heat stress bending, and coefficient of thermal expansion. These tests are designed to evaluate the performance of the composite rods under various conditions, ensuring they meet the required standards for their intended applications. The results from these tests provide valuable data for comparing the performance of different composite materials and optimizing their formulations for specific uses.
[0067] FIG. 8 is a graph that illustrates the tensile properties of the AP-LC reinforced composite rod (100) according to the embodiments disclosed herein. The tensile strength of the prepared samples is measured using a Universal tensile machine, following the test method ASTM D3916. The tensile modulus & the elongation at break are also measured using the same method. The graph provides a visual representation of the material's performance, highlighting its superior tensile properties compared to other composite materials.

Rod Type Diameter Average Tensile strength Average Tensile modulus Elongation at break
mm Kgf/mm2 Kgf/mm2 %
GFRP Rod (500) 0.5 140-160 5000-7000 2.5-4
ARP Rod (700) 0.5 160-180 6500-8000 2.5-3
AP-LC reinforced composite rod (100)
0.5
210-240
8500-10000
2.5-3
Table IV
[0068] In an embodiment, Table IV illustrates the tensile strength and modulus comparison of the GFRP rod (500), the ARP Rod (700) and the AP-LC reinforced composite rod (100). It further illustrates that the maximum amount of tensile stress, a rod can withstand before it fails is high for the AP-LC reinforced composite rod (100) compared to the other FRPs, showing an excellent stiffness as well. Its unique performance is attributed to the strong composite structure, featuring a robust LCP backbone and highly efficient cross-links in the thermoset resin, setting it apart from the others.
[0069] The primary purpose of the flexibility/ minimum bend test is to verify that the material can withstand the desired curvature without compromising its mechanical properties (Prevent damage to the composite rod due to excessive bending stresses).
AP-LC reinforced composite rod (100) ARP Rod (700) GFRP Rod (500)
6.0 8.0 11
5.5 7.0 12
= 13D = 16D = 25D

Table V
[0070] In an embodiment, Table V illustrates the minimum bend diameter of AP-LC reinforced composite rod (100) is < 13D at 25? (D is the diameter of the rod). The AP-LC reinforced composite rod (100) samples shows high flexibility compared to the ARP (700) and the GFRP (500).
[0071] The heat stress bending (HSB) test measures the rod’s resistance to deformation and cracking under a specified higher temperature condition & bending. The HSB test is essential for assessing the durability and reliability of FRP rods in OFC application particularly in applications exposed to high temperatures. This test keeps the material at higher temperature 24 hours by providing a bending of 50 x D, D is the diameter of composite rod.
[0072] In an embodiment, the HSB test is conducted by keeping the ARP (700), FRP (500), AP-LC reinforced composite rod (100) samples by providing 40XD & 25XD at 100 degrees as well for the clear comparison.
Heat stress bending performance @ at different testing conditions.
Bending Dia @ 80oC for 1hour Bending Dia @ 100oC for 1hour Bending Dia @ 100oC for 24hours
50XD 40XD 25XD 50XD 40XD 25XD 40XD 25XD
GFRP GFRP GFRP
ARP ARP ARP ARP ARP ARP
AP-LC reinforced composite rod AP-LC reinforced composite rod AP-LC reinforced composite rod AP-LC reinforced composite rod AP-LC reinforced composite rod AP-LC reinforced composite rod AP-LC reinforced composite rod AP-LC reinforced composite rod
Table VI
[0073] In an embodiment, Table VI illustrates the delamination occurs in ARP (700) and GFRP (500) when it undergoes a high temperature & maximum bending dimension of – 25xD & 40XD respectively. Compared to the ARP (700), the AP-LC reinforced composite rod (100) shows a better bending property even at 100 degrees for 24 hours and passed the 5 days heat stress test at 100o C with 25XD bending. This indicates the AP-LC reinforced composite rod (100) is very suitable for OFCs & other higher temperature applications.
Product Test Test Method Unit Results
AP-LC reinforced Composite rod (100) Co-efficient of Thermal Expansion ASTM D696 1/°C 1.22x10-06
Table VII
[0074] The embodiment of Table VII illustrates the results of the co-efficient of thermal expansion (CTE) done on the AP-LC reinforced composite rod (100) by following the test method ASTM D696.
Metal Coefficient of Thermal Expansion (CTE) Unit
Aluminum 22 × 10?6 /°C 1/°C
Steel 11 × 10?6 /°C 1/°C
Copper 16.5 × 10?6 /°C 1/°C
Titanium 8.6 × 10?6 /°C 1/°C
Brass 18 × 10?6 /°C 1/°C
Stainless Steel 16 × 10?6 /°C 1/°C
Table VIII
[0075] In an embodiment, Table VIII illustrates that the AP-LC reinforced composite rod (100) has a significantly lower coefficient of thermal expansion (1.22 × 10?6 /°C) compared to metals like aluminum, steel, copper, brass, and stainless steel, which generally have CTE values ranging from 10 to 22 × 10?6 /°C. This makes the composite material better suited for applications requiring thermal stability and minimal expansion with temperature fluctuations.
[0076] In an embodiment, the CTE of the AP-LC reinforced composite rod (100) (1.22 × 10?6 /°C) is significantly lower than most common metals, which typically have CTEs in the range of 10 × 10?6 /°C to 22 × 10?6 /°C. The composite rod has less expansion or contraction with temperature changes compared to metals, making it more thermally stable. The low CTE of the AP-LC reinforced composite rod (100) makes it more stable when subjected to temperature changes compared to metals.
[0077] In an embodiment from the test results, the mechanical property flexibility and heat stress bending of the AP-LC reinforced composite rod (100) show superiority compared to the other existing composite rods for the OFCs. As a versatile alternative to the GFRP (500) and the ARP (700), the AP-LC reinforced composite rod (100) delivers high tensile strength and stiffness, excellent flexibility, and a high finish after the process. The AP-LC reinforced composite rod (100) demonstrates a tensile strength 40% higher than ARP (700) and 70% higher than FRP, making it a highly effective replacement for GFRP (500) and ARP rods (700) in telecommunication applications. There’s proper compatibility of the Aromatic Polyester-based Liquid crystal fibre (101) and the thermoset resin (102), which are derived from polyol and diisocyanate. So, the properly aligned/bonded interfaces provide the best mechanical property to the final composite products. The perfectly oriented structure of the LCP structure of the Aromatic polyester liquid crystal fibre (101) offers a balance of properties compared to other performance alternatives.
[0078] In an embodiment, major test results which are done during the invention show the proofs of the unique characteristics/properties of the AP-LC reinforced composite rod (100) made of Aromatic Polyester-based fibre having a liquid crystal polymer fibre (101) as the reinforcement phase and the thermoset resin (102), which is derived from polyol and diisocyanate as the matrix phase made by specific formulation and combination compared to the composite rods existing in the telecommunication industry as a strength element. It has superior strength, modulus, flexibility, and heat resistance compared to the existing strength elements.
[0079] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. While the preferred embodiments have been described, those skilled in the art will recognize that modifications can be made within the scope of the described embodiments. ,CLAIMS:CLAIMS
We claim:
1. A composite rod (100) for protecting an optical fiber cable from external stresses, comprising:
a reinforcement phase comprising an aromatic polyester-based liquid crystal (AP-LC) fiber (101) having a liquid crystal polymer nature; and
a matrix phase comprising a thermoset resin (102), wherein the liquid crystal fiber comprises an aromatic polyester-based fiber having a liquid crystal polymer nature,
wherein the composite rod (100) is positioned in a periphery of or embedded within an outer sheath of the optical fiber cable to protect the optical fiber cable from external stresses.
2. The composite rod (100) as claimed in claim 1, wherein the liquid crystal fiber is characterized by a repeating unit comprising aromatic rings connected by ester linkages, wherein the aromatic rings comprise benzene rings each substituted with a carbonyl group (C=O) directly attached to the aromatic ring, and wherein the ester linkages are formed by carbonyl groups connected to oxygen atoms.
3. The composite rod (100) as claimed in claim 2, wherein a polymer chain comprising the repeating units denoted by "X" and "Y" represented by a molecular structure:

4. The composite rod (100) as claimed in claim 1, wherein the thermoset resin (101) is derived from diisocyanate segment and polyol segment.
5. The composite rod (100) as claimed in claim 4, wherein the polyol segment includes hydroxyl groups (-OH) that react with isocyanate groups (-NCO) to form urethane linkages, and wherein the diisocyanate segment includes isocyanate groups that react with hydroxyl groups to form urethane linkages.
6. The composite rod (100) as claimed in claim 4, wherein a polymer chain comprising repeating units denoted by "n" represented by a molecular structure:

7. The composite rod (100) as claimed in claim 1, wherein a content quantity of the liquid crystal fibers (101) in the reinforcement phase is between 60-70% by weight, and wherein a content quality of the thermoset resin (102) in the matrix phase is between 30-40% by weight.
8. The composite rod (100) as claimed in claim 1, wherein the matrix phase comprises:
96% by weight of the thermoset resin (102);
0.8-1% by weight of cross-linking agents 01 and 02;
approximately 1.8-2% by weight of cross-linking agent 03; and
0.8-1.2% by weight of a releasing agent.
9. The composite rod (100) as claimed in claim 1, wherein the composite rod (100) is manufactured through a pultrusion process to produce the composite rod (100) having a continuous cross-section.
10. The optical fiber cable of claim 1, wherein the at least one composite rod (100) has a diameter in a range of 0.4 mm to 1 mm.