The Effects Of Environmental Ageing On Mechanical Properties Of T700/HT280 Composites

In this study,T700/HT280 composites and HT280 resin were subjected to three kinds of environmental simulation experiments,including high temperature,hydrothermal and vacuum thermal cycling environments.The ageing mechanisms were analyzed by several analytic techniques,such as FTIR-ATR,DMA and C-scanning.The effects of three environments on static mechanical properties and fatigue resistance were studied 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.After the long-term exposure to high temperature,thermal-oxidative ageing can be seen in resin.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.After the long-term thermal ageing,the static mechanical properties and fatigue resistance significantly decrease.The mass loss rates of composite and resin increase firstly and then flatten with the increased hydrothermal ageing time.As a result of the interfacial debonding caused by the difference in coefficients of moisture expansion of fiber and resin,tan? curve peak moves to lower temperature.After hydrothermal ageing,interlaminar shear property became worse,but no evident changes in the fatigue resistance,tensile,and bending properties has been found.With the increasing vacuum thermal cycles,the mass loss rates of composite and resin increase firstly and then level off.The accumulation of thermal effect is responsible for the increased cross-link density of resin.The tan? curve peak of T700/HT280 composites moving to higher temperature is attributed to the post-curing and thermal ageing.After environment ageing,the interlaminar shear property marginally increases,but the tensile,bending properties and fatigue resistance decrease obviously.