DESC:HYGROTHERMAL AGEING RESISTANT CARBON FIBER REINFORCED EPOXY BASED COMPOSITE MATERIALS AND METHOD FOR FABRICATING THEREOF

FIELD OF INVENTION

[0001] The present disclosure generally relates to fabrication of hygrothermal ageing resistant carbon fiber reinforced epoxy based composite materials, in particular relates to long carbon fiber reinforced epoxy based composite materials, and methods of fabricating thereof.

BACKGROUND
[0002] Rapid growth in manufacturing industries has led to the need for the betterment of materials in terms of strength, stiffness, density, and lower cost with improved sustainability. Composite materials have emerged as one of the materials possessing such betterment in properties serving their potential in a variety of applications. Carbon fibre reinforced laminates are the most promising modern-day structural materials with a wide range of applications in fields such as aerospace, construction, mechanical, automobile, biomedical and marine.

[0003] Composites reinforced with fibers provide the advantages of high strength, rigidity, lightweight, increased resistance to corrosion and are gaining more importance in the market. In spite of these advantages, the widespread use of carbon fiber reinforced composite materials has been limited due to the exposure to harsh environmental conditions during their service. Under high temperature and high moisture conditions, these composite materials absorb water/moisture that leads to an increase in weight of the composite material and accompanied by structural degradation and mechanical degradation.

[0004] In accordance with one of the prior art documents, carbon fibers and graphene nanoplatelets (GNP) reinforced hybrid composites were fabricated using the traditional hand layup method followed by compression molding. However, the traditional method is prone to lot of defects, results in textured finish and variable thickness of the laminates with non-uniform fiber volume and mechanical strength.

[0005] In accordance with another prior art document, carbon fiber reinforced plastic has been disclosed. For improving the mechanical and/or electrical properties of the composite structures formed by carbon fiber reinforced plastics, the prior arts focus on increasing the amount of carbon fiber in Carbon fiber reinforced plastics. But simply increasing the amount of carbon fiber reinforcement material in carbon fiber reinforced plastics does not meet the objective and is not economically feasible.

[0006] Thus, there remains a need in the art for a scalable method for fabricating long carbon-fiber reinforced composite materials that are hygrothermal aging resistant and further an efficient method for minimizing the moisture absorption during the service period of the carbon fiber reinforced composite materials for preventing the degradation of laminates.

OBJECT OF THE INVENTION

[0007] It is the primary object of the present disclosure to provide long carbon fibers reinforced epoxy based composite materials with improved hygrothermal ageing resistance.

[0008] It is further objective of the present disclosure to provide a method for fabricating long carbon fiber reinforced epoxy based composite materials with improved hygrothermal ageing resistance.

[0009] It is further objective of the present invention to reduce the water intake/ingress ability of long carbon fiber reinforced epoxy based composite materials by coating the carbon fiber fabrics with a layer comprising of graphene nanoplatelets.
SUMMARY OF THE INVENTION

[0010] In an aspect of the present disclosure, a composite material comprising of a plurality of unidirectional carbon fiber fabrics, a layer of nonfunctionalized graphene nanoplatelets coated onto each layer of carbon fiber fabrics and a matrix material has been disclosed. The layer of nonfunctionalized graphene nanoplatelets (GNPs) is in the range of 0.35% to 0.45% of the mass of the carbon fibers fabrics. Further the matrix material is composed of epoxy resins comprising of thermosetting polymers.

[0011] In another embodiment, a method for fabricating a composite material based on long carbon fiber reinforced epoxy resins with improved hygrothermal ageing resistance with each layer of carbon fiber fabric being coated with a layer of nonfunctionalized graphene nanoplatelets (GNPs) using Vacuum assisted resin transfer molding (VARTM) technique has been disclosed. The method comprises the steps of preparing a solution by dispersing graphene nanoplatelets in a volume of ethanol in the range of 200-600 milliliters, followed by a two-stage sonication process. Initially, direct probe sonication of the resultant solution for a time period in the range of fifteen minutes to one hour followed by indirect ultra-sonication for a time period in the range of fifteen minutes to one hour, coating the sonicated solution uniformly onto a plurality of layers of carbon fiber fabrics by using an air spray brush, further manufacturing laminates with 8 layers of carbon fiber fabrics using the Vacuum assisted resin transfer molding (VARTM) technique by infusing the layers of coated carbon fibers fabrics with a matrix material composed of epoxy resins, then curing the plurality of laminates at room temperature for a period of 24 hours and then at 100°C for a period ranging from 2hours to 3 hours, thereby generating long carbon fibers reinforced epoxy based composite materials.

[0012] In an embodiment of the present invention, each layer of carbon fiber fabrics is coated with a layer of nonfunctionalized graphene nanoplatelets (GNPs) using the spray coating technique utilizing an air brush and an air pump.

[0013] In an embodiment of the present invention, the amount of nonfunctionalized graphene nanoplatelets are in a range of 0.35% to 0.45% of the mass of the carbon fiber fabrics.

[0014] In an embodiment of the present invention, the epoxy resins comprises of thermosetting polymers.

[0015] In an embodiment of the present invention, the composite materials coated with a layer of nonfunctionalized GNPs have decreased water intake/ingress at any given time step over a period of 30 days. The decrease in the water intake/ingress at the end of 30 days of hygrothermal ageing is ~ 5 % lower in laminates manufactured using GNP coated carbon fiber fabrics than laminates manufactured using untreated carbon fiber fabrics.

[0016] These and other objects, features, and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description.

BRIEF DESCRIPTION OF DRAWINGS

[0017] The exemplary embodiments of the present invention has been described with reference to the accompanying drawings below:

[0018] Figure 1 illustrates a flow chart for a method for fabricating long carbon fibers reinforced epoxy based composite materials coated with nonfunctionalized graphene nanoplatelets (GNPs) in accordance with an embodiment of the present invention.

[0019] Figure 2 illustrates the amount of water intake as a percentage of the weight of the composite materials for different durations of hygrothermal ageing time.

DETAILED DESCRIPTION OF THE INVENTION

[0020] The invention will be described in detail below with reference to the drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation procedures are given, but the scope of protection of the present invention is not limited to the following embodiments.

[0021] In the present invention, long carbon fibers reinforced epoxy based composite materials and a method of fabricating the same is disclosed. The present invention enhances the water-resistant properties of the composite materials. In particular, the present invention relates to a method for fabricating long carbon fibers reinforced epoxy based composite materials where the carbon fiber fabrics are coated with a layer of nonfunctionalized graphene nanoplatelets (GNPs) and finally long carbon fibers reinforced epoxy based composite materials are manufactured using Vacuum assisted resin transfer molding (VARTM) technique.

[0022] In Vacuum assisted resin transfer molding (VARTM) technique, the dry carbon fiber fabrics coated with a layer of nonfunctionalized graphene nanoplatelets (GNPs) are placed inside a mold and then vacuum is applied to assist in the infusion of the epoxy resin as a matrix material into the layers of carbon fiber fabrics followed by curing the plurality of laminates at room temperature for a period of 24 hours and then at 100°C for a period ranging from 2 hours to 3 hours

[0023] In an embodiment of the present invention, a composite material comprising plurality of unidirectional carbon fiber fabrics, a layer of nonfunctionalized graphene nanoplatelets coated onto each layer of carbon fiber based fabrics and a matrix material has been disclosed. The layer of nonfunctionalized graphene nanoplatelets (GNPs) is in the range of 0.35-0.45% of the mass of the carbon fibers fabrics. Further the matrix material is composed of epoxy resins comprising of thermosetting polymers.

[0024] In an embodiment of the present invention, a method for fabricating water-resistant long carbon fiber reinforced epoxy based composite materials has been disclosed.

[0025] In an embodiment of the present invention, the method for fabricating long carbon fiber reinforced epoxy based composite materials comprises the steps of dispersing a pre-defined amount of the graphene nanoplatelets in a pre-defined volume of ethanol in the range of 200-400ml followed by a two-stage sonication process. Initially, probe sonication of the resultant solution for a period in the range of fifteen minutes to one hour followed by ultra-sonication for a period in the range of fifteen minutes to one hour. The resultant sonicated solution is uniformly coated onto each of the eight layers of carbon fibers fabrics utilizing an air spray brush.

[0026] In another embodiment of the present invention, the method further comprising the step of manufacturing laminates with 8 layers of carbon fiber fabrics using the Vacuum assisted resin transfer molding (VARTM) technique by infusing the layers of coated carbon fiber fabrics with a matrix material composed of epoxy resins comprising of thermosetting polymers then curing the plurality of laminates at room temperature for a period of 24 hours and then at 100°C for a period ranging from 2hours to 3 hours, thereby generating water/moisture resistant long carbon fibers reinforced epoxy based composite materials/laminates.

[0027] In an embodiment of the present invention, the plurality of layers of carbon fiber fabrics are coated with a layer of nonfunctionalized graphene nanoplatelets using a method of spray coating.

[0028] In an embodiment of the present invention, the composite materials coated with a layer of nonfunctionalized GNPs in a concentration in the range of 0.35% to 0.45% of the mass of the carbon fiber fabrics demonstrates decreased water intake/ingress at any given time step over a period of 30 days. The decrease in the water intake/ingress at the end of 30 days of hygrothermal ageing is ~ 5 % lower in laminates manufactured using GNP coated carbon fiber fabrics in a concentration in the range of 0.35% to 0.45% of the mass of the carbon fiber fabrics than laminates manufactured using untreated carbon fiber fabrics.

[0029] Referring to figure 1, illustrates flowchart depicting a method (100) of fabricating long carbon fiber reinforced epoxy based composite materials. The method comprises the steps of preparing a solution by dispersing a pre-defined amount of the nonfunctionalized graphene nanoplatelates in a pre-defined volume of ethanol (105), subjecting the solution to probe sonication for a time-period in the range of 15 minutes to 1 hour and followed by ultra-sonication for a time period in the range of 15 minutes to 1 hour (110), coating the ultra-sonicated solution uniformly onto a carbon fiber fabric with an air spray gun (115), and producing laminates with multiple layers of coated carbon fiber fabrics using the Vacuum assisted resin transfer molding (VARTM) technique by infusing the layers of carbon fiber fabrics with epoxy resin as a matrix material (120), and finally curing the laminates at room temperature for 24 hours and then at 100 degree Celsius for 2 hours (125).

[0030] Referring to figure 2, illustrates the amount of water intake as a percentage of the weight of the composite materials. In particular, illustrates the increased hygrothermal ageing resistance of the composite materials-based laminates in accordance with an embodiment of the present invention.

[0031] Further, the present disclosure is advantages over the existing prior arts as the present invention discloses a sustainable method for the fabrication of the hygrothermal ageing resistant carbon fiber composite materials.

[0032] Furthermore, the present invention enables the fabrication of water-resistant long carbon fiber reinforced epoxy based composite materials industrially applicable in aerospace, civil constructions, automobile industry, marine (naval ships and vessels), wind turbine blades, solar cells, flexible electronics (IC trays and casings (housings) of notebook computers).

[0033] The present invention may be better understood by reference to the following non-limiting examples, which are presented in order to completely illustrate the preferred embodiments of the invention. They should in no way be construed to limit the broad scope of the invention.

Working Example:

[0034] The present invention is now further described by the following non-limiting example.

[0035] Fabrication of long carbon fiber reinforced epoxy based composite materials:

[0036] The long carbon fiber reinforced epoxy based composite materials are manufactured using the vacuum assisted resin transfer molding (VARTM) technique. Two sets of laminates are prepared. In the first set, the laminates are manufactured from the raw carbon fibers. In the second set, the carbon fibers is coated with graphene nano-platelets (GNPs). Initially, a solution is prepared by dispersing GNPs in 300 ml ethanol followed by two-stage sonication process. Firstly, direct probe sonication of the resultant solution for 30 minutes followed by indirect ultra-sonication 30 minutes. The sonicated solution is poured into an air-spray gun and uniformly coated onto a plurality of layers of carbon fiber fabrics. Each laminate is manufactured with 8 layers of carbon fiber fabrics using the Vacuum assisted resin transfer molding (VARTM) technique by infusing the layers of coated carbon fibers fabrics with a matrix material composed of epoxy resins then curing the plurality of laminates at room temperature for a period of 24 hours and then at 100°C for 2.5 hours, thereby generating long carbon fibers reinforced epoxy based composite materials.

[0037] Hygrothermal Test

[0038] Composite specimens were exposed to a specific environmental condition to study the effect of coating a layer of nonfunctionalized graphene nanoplatelets (GNP) on to carbon fiber fabrics prior to fabricating laminate on the water absorption behaviour of long carbon fiber reinforced epoxy based composite materials. The long carbon fiber reinforced epoxy based composite materials coated with a layer of nonfunctionalized GNPs are fragmented to coupon specimens and subjected to hygrothermal ageing in deionized (DI) water maintained at 75 degrees Celsius for a duration in the range of 0-30 days. The water absorption was observed by weighing each specimen to the milligram and taking the average. The percentage of weight change during moisture absorption was determined by calculating the difference between the weight of the laminate specimen during ageing and the initial weight of the laminate specimen before ageing.

[0039] Observations: It was observed that the carbon fibers reinforced epoxy based composite materials coated with a layer of nonfunctionalized GNPs in a concentration in the range of 0.35% to 0.45% of the mass of the carbon fiber fabrics demonstrated decreased water intake/ingress at any given time step over a period of 30 days.

[0040] Results: The carbon fibers reinforced epoxy based composite materials coated with a layer of 0.4% nonfunctionalized graphene nanoplatelets of the present invention demonstrated a reduction of 5.15% of water uptake.

[0041] While the present invention has been described above in terms of specific embodiments, it is to be understood that the invention is not intended to be confined or limited to the embodiment disclosed herein.
,CLAIMS:We claim:

1. A method of fabricating a composite material based on long carbon fiber reinforced epoxy resins with improved hygrothermal ageing resistance, comprising:
preparing a solution by dispersing graphene nanoplatelets in a volume of ethanol in the range of 200-600 millilitres;
sonicating the dispersed solution for a first period ranging from 15 minutes to 1 hour by a direct probe sonication process;
sonicating the resultant solution for a second period ranging from 15 minutes to 1 hour by an indirect ultra-sonication process;
coating the resultant sonicated solution uniformly onto a plurality of layers of carbon fiber fabrics by using an air spray brush/gun;
manufacturing a plurality of laminates with a plurality of layers of carbon fiber fabrics using a Vacuum assisted resin transfer molding (VARTM) technique by infusing the layers of coated carbon fibers fabrics with a matrix material composed of epoxy resins; and
curing the plurality of laminates at room temperature for a period of 24 hours and then at 100 ? for a period ranging from 2 hour to 3 hours.

2. The method as claimed in claim 1, wherein each of carbon fiber fabrics is coated with a layer of nonfunctionalized graphene nanoplatelets (GNPs) using a spray coating process.

3. The method as claimed in claim 2, wherein the amount of nonfunctionalized graphene nanoplatelates are in the range of 0.35% to 0.45% of the mass of the carbon fiber fabrics.

4. The method as claimed in claim 1, wherein the epoxy resins comprise of thermosetting polymers.

5. The method as claimed in claim 1, wherein the plurality of layers of carbon fiber fabrics for the manufacturing of plurality of laminates is 8 layers of carbon fiber fabrics.

6. The method as claimed in claim 1, wherein the composite materials coated with a layer of nonfunctionalized GNPs decrease water intake/ingress at any given time step over a period of 30 days.

7. The method as claimed in claim 7, wherein the decrease in the water intake/ingress at the end of 30 days of hygrothermal ageing is ~ 5 % lower in laminates manufactured with the method as claimed in claim 1.

8. A composite material, comprising:
a plurality of layers of uni-directional carbon fiber fabrics;
at least one layer of nonfunctionalized graphene nanoplatelets (GNPs) coated onto each layer of carbon fiber based fabrics; and
at least one matrix material composed of epoxy resins infused into the plurality of layers of coated carbon fibers fabrics thereby forming a plurality of laminates;
wherein the amount of nonfunctionalized graphene nanoplatelates are in the range of 0.35% to 0.45% of the mass of the carbon fiber fabrics; and
wherein the epoxy resins comprise of thermosetting polymers.

Dated this 27th day of September 2023

MAHUA ROY CHOWDHURY
IN/PA-496
(Authorized agent for the application)