INTERLAMINAR FRACTURE-TOUGHNESS DEGRADATION OF RADIATION-DAMAGED GFRPAND CFRP COMPOSITES

Degradation properties of epoxy matrix GFRP and CFRP composites irradi ated by high-energy electrons were evaluated by interlaminar fracture toughness measurements in Mode I (G(Ic)) and in mixed mode (mode I+II, G(mc)). The results were then compared with microscopic observations of fracture surfaces and dynamic viscoelastic properties to explain th e radiation-induced degradation mechanisms. The sensitivity of radiati on-induced degradation was much more pronounced in G(Ic) than in G(mc) , or in the interlaminar shear strength. Interlaminar fracture toughne ss measurements were found necessary for proper evaluation of the radi ation-induced degradation of FRP composites. For GFRP, a significant d ecrease in G(Ic) was found. Debonding of glass fibers and epoxy matrix (or degradation of silane coupling agents) plays an important role in degradation, in addition to resin degradation. Thus, the improvement of the radiation resistance of fiber-resin interfaces as well the matr ix itself is of supreme importance in order to increase the radiation resistance of GFRP. For CFRP, on the other hand, no degradation in fib er-resin interfaces was found in irradiated specimens, and the slight decrease in G(Ic) seems to be due to resin degradation.