Study On Aging Effect Of T700/HT280 Composites Under High Temperature Environment

T700/HT280 unidirectional composites and HT280 bismaleimide resins used in this research were subjected to the high temperature treatment by an environment simulating equipment.The aging mechanism of the mentioned above materials before and after high temperature was analyzed by using infrared spectroscopy(IR),Scanning electron microscope(SEM),dynamic mechanical analysis(DMA)testing methods.The Static mechanical properties and fatigue properties of T700/HT280 composites as well as the creep behaviors of HT280 resins were tested,respectively.It is shown that the mass loss rates of T700/HT280 composite and HT280 resin increase rapidly and then increase slowly with further ageing,and the mass loss rate of HT280 resins was greater than that of T700/HT280 composites.The mass loss was mainly attributed to the volatilization of water and low molecular weight substances in HT280 bismaleimide resin.High temperature treatment gave rise to the obvious Thermo-oxidative aging of HT280 bismaleimide resins.Lead to the surface of the material gradually darken.The higher temperature corresponding to the tan? curve peak is attributed to the synergistic effect of the post-curing,thermal ageing and interfacial debonding of the composites.The tensile,compressive,Inter-laminar shear strength a curves of T700/HT280 unidirectional composites,and the tensile,compressive,bending strength a curves of HT280 resin showed a tendency to increase first and then decrease,which was attributed to the comprehensive effects of post curing,interfacial debonding and thermal aging in the process of air thermal cycling.As the time high temperature increases,the bending strength of T700/HT280 unidirectional composites presents little change trend.After the high temperature treatment,the tensile-tensile fatigue curves of T700/HT280 composites basically conformed to the "fast-slow-fast" rule manifesting in the shorter fatigue life and the decreased fatigue resistance.The creep speed of HT280 resins showed a decay trend after high temperature treatment,which was ascribed to the combined interactions of evaporation of low molecular weight substances,post curing and thermal aging of resin matrix.The time hardening model can accurately describe the creep behavior of the samples before and after the high temperature treatment.