| Fiber reinforced resin matrix composites are popular in the engineering field due to their advantages of light weight,high strength and good fatigue resistance.However,the performance and service life of composite materials used in the fields of airplane wings and wind turbine blades are easily affected by external environmental factors.Therefore,how to improve the performance of composite material to increase its service life has very important theoretical and practical significance.Carbon fiber(CF)/thermoplastic polyurethane(TPU)/epoxy resin(EP)composites were prepared by Vacuum Assisted Resin Transfer molding(VARTM).CF has the advantages of high strength and high modulus,low specific gravity,and high specific performance.The three-dimensional network structure of TPU can not only improve the toughness of materials,but also play a role in transferring stress.This work studied the influence of the addition of TPU non-woven fabric on the mechanical properties,erosion resistance and interlayer fracture toughness of CF/EP composites.The results show that:(1)compared with CF/TPU/EP composites,the tensile load and tensile strength are increased by 28.6%and 11.8%respectively,and the bending load is increased by 45.3%.The reason is that the three-dimensional network structure of TPU non-woven fabric plays the role of transferring stress in the composite material,making the stress spread in the material,thus improving the mechanical properties of the material.(2)the maximum erosion Angle of CF/EP composites is 90°,which is a typical brittle material,while the maximum erosion Angle of CF/TPU/EP composites is 30°,indicating that the addition of TPU improves the surface toughness of composites.In addition,the erosion wear resistance of CF/TPU/EP increases by 58%,130%,185%,227%and 292%respectively at erosion angles of 30°,45°,60°,75°and 90°.The excellent erosion and wear resistance of CF/TPU/EP composites is related to the formation of a flexible three-dimensional network structure on the composite surface,which can effectively absorb impact energy.On the other hand,non-woven fiber plays the role of"bridging",which can effectively prevent the isolation block caused by cracks from being eroded away.(3)after joining TPU non-woven composite material typeⅠenergy release rate GⅠ_C increased by 14%,the energy release rate GⅡ_C typeПincreased by 58%,CF/EP composite section is smooth,is a typical brittle failure mode,the TPU non-woven interlaminar toughening of CF/TPU/EP composite materials,epoxy resin and TPU non-woven composite material layers formed a better overall,the fracture is relatively rough,is a typical ductile failure mode.In order to further improve the performance of the composites,the mixed solution of graphene nanosheets(GNPs)and carbon nanotubes(CNTs)of different concentrations was sprayed onto the TPU non-woven fabric,and then the non-woven fabric sprayed with nanoparticles was added to the composites to produce CF/T-(G/C)/EP composites.SEM showed that graphene and carbon nanotubes wrapped the TPU fiber.We compared the effects of different nanoparticle contents on the properties of composites,and found that:(1)compared with CF/EP composites,the tensile and bending properties of CF/T-(G/C)/EP composites were improved,of which the tensile properties were the best when the content of nanoparticles was 0.2%,and the bending properties were the best when the content of nanoparticles was 0.8%.Compared with CF/TPU/EP,the addition of nanoparticles is not conducive to the improvement of mechanical properties of composites.The reason may be that the binding force between the nanoparticles and between the nanoparticles and the fiber is weak.When the composite material is stretched or compressed,the substrate carrying the nanoparticles slides,which intensifies the crack expansion and extension,resulting in the reduction of the mechanical properties of the composite material.(2)The maximum erosion Angle of CF/TPU/EP composite material is 30°,and that of CF/T-(G/C)/EP composite material is 60°,indicating that the material has undergone tough-brittle transformation.At the same time,the erosion resistance of CF/T-(G/C)/EP composites was improved compared with that of CF/TPU/EP after the addition of nanoparticles.The reason is that GNP and CNTs have good thermal conductivity,which can effectively transmit the heat generated by the impact of graveand slow down the plasticization of materials caused by the heat generated on the material surface,thus improving the erosion resistance of composites.(3)After joining nanoparticles,theⅠenergy release rate GⅠ_Cof composite is reduced,when nanoparticles content is 0.8%,the relative to the CF/EP was reduced by 35%;And the addition of nanoparticles,effectively improve the composite typeⅡenergy release rate GⅡ_C,when nanoparticles content is 0.8%,the relative to the CF/EP increased by 119%.Nanoparticles can block the propagation path of the crack,deflect the crack,absorb and consume part of the energy,and improve the interlaminar toughness of the composite.However,when the content of nano-particles is high,the TPU non-woven fabric fiber is completely wrapped,unable to combine with the epoxy matrix,and the binding force between the nano-particles and the non-woven fabric fiber is poor,which is prone to crack due to the shear force,resulting in the deterioration of the interlaminar performance of the material. |
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