The aging of carbon fiber/ epoxy resin composite(T300/ BHEP) in thermo oxidative, hygrothermal
and hot water aging conditions are studied,the changes of weight and glass transition temperature(Tg) with aging con ditions are tested and analyzed the aging mechanisms. Results show that the Tg of T300/ BHEP composite increases in
thermo oxidative aging conditions because of post curing and free volume shrinkage, and the plasticization of water
causes decrease of Tg in hygrothermal and hot water aging conditions. In these three aging conditions, Tg is linear with
the weight change ratio. Through contrasting the results of 80益thermal oxidative aging, 80益/ RH75%hygrothermal
aging and 80益hot water aging,the plasticization of water have more impact on Tg than post curing, and Tg decreases
more significantly when the humidity is higher.