Study On Performance And Mechanism Of CFRP Laminates Interleaved By Nanophase/Thermoplastic Films

Carbon fiber reinforced polymer（CFRP）composite has been widely used in the aerospace industry due to its excellent characteristics.Thermosetting epoxy exhibits many advantages such as good mechanical properties and high heat resistance,and is widely used as matrices for CFRP composites.However,epoxy matrix is inherently brittle due to the highly crosslinked network structure,which results in the bad fracture toughness and delamination damage.Therefore,realizing the toughening and the maintenance of other excellent properties simultaneously for the composite materials is of great significance for the future research and wide application.The carbon fibre reinforced epoxy matrix composite laminates were interleaved by thermoplastic Polyetherketone-cardo（PEK-C）films and prepared by hot pressure process to improve the fracture toughness.The effect of curing time（i.e.0.5h,1h,2h,3h）on the phase morphology spectrum and fracture toughness was investigated in terms of Mode I interlaminar fracture toughness(G_IC)tests and scanning electronic microscope（SEM）.The process-mircostructure-property correlation was explored and the optimum curing process was obtained.In order to achieve the improvement of toughness and maintenance of the inherent excellent proprieties of CFRP composite laminates,nano-SiO₂ and CNTs were introduced to prepare nanophase/PEK-C films to interleave CFRP composite.The fracture toughness and mechanical performances in plane were investigated by mode-I interlaminar fracture toughness test,three-point bending test,and interlaminar shear tests.The results showed that PEK-C film interlayer was efficient for improving the toughness of composites.And the G_IC value of 0.5h,1h,2h,3h specimen was enhanced by 61.77%,90.65%,50.58%and 9.37%after the introduce of PEK-C film.However,increasing curing time would weaken the toughening effect of PEK-C interlayer.According to SEM analysis,the layered phase morphology,consisting of“scaly”homogeneous PEK-C resin,nodular co-continuous structure and sea-island dualphase was observed in the interlaminar region,which were proved contributing to the improvement of toughness.The results show that nano-SiO₂ with content of 0.5wt%and CNTs with content of 0.1wt%had the optimum effect on the performance of modified laminates.According to SEM analysis,after the addition of nanophase materials,three remained the layered characteristic phase structures of“scaly”homogeneous structure,nodular co-continuous structure and“sea-island”dualphase in the interlaminar region.But nanophase material made the homogeneous PEK-C structure more discrete and no obvious difference of nodular co-continuous structure and“island”dualphase was found.Nano-SiO₂ made PEK-C film produce more plastic deformation and absorb more fracture energy through the good interface binding force of nanophase particles and PEK-C film.Besides,nano-SiO₂ has enhanced the interfacial force of TP/TS resin.CNTs suppressed the cracks propagation by CNTs extraction and fracture,which improved the interlaminar fracture toughness of composites.