Study On Preparation And Performance Of Recycled Carbon Fiber Reinforced Resin Matrix Composites

Carbon fiber composite material(CFRP)has been widely used in aerospace,offshore wind power,automobile manufacturing and other fields due to its advantages of light weight,high strength,fatigue resistance,corrosion resistance,and easy forming and processing.However,the high cost of CFRP preparation,complex production process,unstable mechanical properties and other defects have restricted the development of CFRP in the automotive industry and hindered the advancement of automobile lightweight.Carbon fiber composite materials currently used in the automotive field mainly use two-dimensional woven carbon fiber cloth as the reinforcing phase and thermosetting resin as the matrix phase.The tensile strength of the two-dimensional woven carbon fiber cloth in the fiber radial direction is excellent,but the tensile strength in the non-fiber radial direction is greatly reduced.The in-plane mechanical properties are anisotropic and have obvious short plate effect;During the curing and molding process,the polymer chemically reacts to form a three-dimensional interlinked network structure,which has the performance characteristics of insoluble and infusible.Therefore,the composite material under the thermosetting resin system is damaged or reaches the service life of the composite material to increase the difficulty of repairing and recycling the composite material.It is not conducive to reducing the production cost of CFRP.In order to solve the anisotropy of the in-plane mechanical properties of two-dimensional woven carbon fiber cloth or unidirectional carbon fiber reinforced resin matrix composites and evaluate the application prospects of recycled fibers in the automotive manufacturing field,this paper selects Toray commercial T700 carbon fiber with uniform fiber distribution characteristics.Woven fabrics and recycled carbon fiber non-woven fabrics are used as reinforcement,which reduces the cost of carbon fiber weaving,simplifies the forming process of carbon fiber felt,and provides better design and performance predictability for composite materials.This paper also prepared resin matrix composites with different fiber mixing ratios under thermosetting resin and thermoplastic resin systems and explored the effect of different recycled fiber ratios on the mechanical properties of composites under the same resin system,as well as in different resins.Under the system,the effect of the same percentage of recycled fibers on the mechanical properties of the composite material,and the microscopic morphology of the tensile fracture specimen section was observed.The fracture failure model and resin-fiber interface bonding force of commercial carbon fiber and recycled carbon fiber composite materials under different resin types are explored.The mechanical test results of the mixed carbon fiber/vinyl resin composite material show that the addition of carbon fiber can significantly improve the tensile and flexural strength of the vinyl resin matrix.In the thermosetting resin system,as the proportion of recycled fibers increases,the mechanical properties of composite materials show a gradual upward trend.When the proportion of recycled fibers reaches 90%,the tensile strength increases by 44.2% compared to RG0.The amount increased by 31.5%;the tensile strength and modulus of the pure recycled carbon fiber reinforced vinyl composite material reached the maximum,299.6MPa and21.4GPa,respectively.Through the comparative analysis of the cross section of the tensile sample,it is found that in the thermosetting resin system,the interface bonding force between T700 commercial carbon fiber and the resin is weak,and there are obvious exposed fibers at the section,while the resin-interface bonding force of the recycled fiber is stronger.There are fewer exposed fibers at the section and the length is lower.The fracture failure models of composite materials are all brittle fracture,the tensile strain is about 1.2%,and the failure modes are matrix cracking,fiber debonding,fiber pull-out and fracture.The mechanical test results of the mixed carbon fiber/thermoplastic resin composite material show that the tensile strength of the carbon fiber non-woven fabric reinforced PC resin composite material at different mixing ratios increases with the increase in the proportion of recycled carbon fiber non-woven fabric;compared with pure PC resin board,The fiber reinforcement effect is remarkable;the performance of the mixed fiber reinforced thermoplastic resin matrix composites in all mixing ratios is better than that of the thermosetting resin matrix composites in tensile strength and tensile modulus,and the tensile strength is increased by100 MPa and above.It can be seen from the cross-sectional micro-topography that,compared with the thermosetting resin system,the bonding force of the commercial T700 carbon fiber in the PC resin is greatly improved,and its microscopic performance is that the length of the exposed fiber at the tensile section of the composite material is shorter;The surface of the exposed carbon fiber separated from the resin interface is relatively clean and smooth,with less resin residue and longer length,while the surface of the exposed carbon fiber separated from the resin interface under the thermoplastic resin system is relatively rough,the residual traces of PC are obvious,and the length is shorter,indicating that the carbon fiber and The interface bonding force of PC is relatively better,which further explains that the tensile strength of the composite material under the thermoplastic resin system is significantly better than the tensile strength of the composite material under the thermosetting resin system.The main failure models of composite materials are matrix cracking,fiber pull-out and fracture,and interface debonding.