WEIGHT-CHANGE ANALYSIS OF THE INTERPHASE IN HYGROTHERMALLY AGED FRP -CONSIDERATION OF DEBONDING

This study deals with the experimental and analytical evaluation of we ight changes in the interphase in hygrothermally aged fiber-reinforced plastics (FRP). The influence of debonding on the weight change is ma inly discussed. The weight change of the interphase was evaluated by c omparing the weight change of FRP with that of the plain resin. This m ethod showed that both weight gain and weight loss occurred in the int erphase, and these changes were closely related to each other. The vol ume of debonding at the interphase was evaluated quantitatively by mic roscopic observation of the aged FRP. Weight gain in the interphase wa s calculated from the volume of debonding, and the calculated results showed good agreement with experimental data. This result clarified th at the weight gain in the interphase was caused by water penetration i nto debonds at the interphase. The results obtained suggested that imp rovement in the water resistance of the binder at the interphase is im portant to enhance the water resistance of glass-fiber-mat reinforced plastics. (C) 1997 Elsevier Science Limited.