Study On The Effects Of Interfacial Layer And Resin Matrix On High Temperature Resistance Of Carbon Fiber/bismaleimide Composites

The temperature resistance level and interfacial thermal stability of carbon fiber/bismaleimide composites have limited their application as structural parts with high temperature resistance,and the poor processability of the bismaleimide resin for prepreg can hardly meet the manufacturing requirements of complex components.Therefore,based on the modification of surface of carbon fiber and resin matrix,the effects of interface layer and resin matrix on the high temperature resistance of carbon fiber/bismaleimide composites were studied.A interfacial layer of composites with high temperature resistance was constructed by sizing of waterborne polyamic acid,and the rheological property of bismaleimide resin with high temperature resistance was regulated by thermoplastic polyimide through pre-in-situ polymerization.Then carbon fiber/bismaleimide prepreg and composites were prepared through pre-in-situ self-strengthening technology,and the uniformity of the heat resistance and processability of bismaleimide resin matrix and composites was achieved.1.A waterborne polyamic acid was molecularly designed,and used as sizing agent to modify the surface of carbon fiber,and the T800H-modified/BD composites was prepared.The roughness of the surface of carbon fiber was lowered and the chemical activity of the surface was enhanced.Compared to unmodified composites,the transverse fiber bundle tensile(TFBT)strength and interlaminar shear strength(ILSS)of T800H-modified/BD composites were increased,and the retention ratio of these two properties at 280? were increased by 40.3%and 41.2%,respectively.The failure mode of composites was changed from interface debonding to matrix cracking,which indicated the construction of interface layer with high temperature resistance in carbon fiber/bismaleimide composites.2.A thermoplastic polyimide(pis-PI)with twisted and non-coplanar structure was prepared through pre-in-situ polymerization,and applied to fabricate bismaleimide resin(BD-PI)with high temperature resistance.Compared to commercial matrix(BD),the minimum viscosity of BD-PI matrix was improved from 0.03Pa·s to 2.9Pa s,which met the processing requirements of prepreg.The glass transition temperature and thermal decomposition temperature were enhanced from 3560C,403? to 367?,452?.T800H/BD-PI prepreg and composites with high temperature resistance were prepared through pre-in-situ self-strengthening technology,and SEM image indicated that BMI microparticles were uniformly dispersed on the surface of prepreg.Compared to unmodified composites,the TFBT strength and ILSS of T800H/BD-PI composites were increased,and the retention ratio of these two properties at 280? was increased by 14.9%and 10.5%,respectively.3.Based on T800H-modified carbon fiber and BD-PI matrix,the thermal stability and failure mode of carbon fiber/bismaleimide composites were studied after thermo-oxidative aging at 280?.A relatively stable surface morphology of T800H-modified carbon fiber was maintained after 280?/4h thermo-oxidative aging and relatively stable chemical structure and heat resistance of BD-PI matrix were maintained after 280?/8h thermal-oxygen aging.The failure mode of T800H-modified/BD composites after thermo-oxidative aging was mainly dependent on matrix cracking,however,the failure mode of T800H/BD-PI composites after thermal thermo-oxidative aging was mainly dependent on interface debonding.