Effects of Electron Beam Irradiation on Charpy Impact Value of Short Glass Fiber (GFRP) Samples with Random Distribution of Solidification Texture Angles from Zero to 90 Degrees

Compression-molded short-fiber GFRP-BMC panels have random distribution of solidification texture angles from zero to 90 degrees in the center of the mother panels. Hence, there is significantly lower impact strength in the panel center than in the outside. However, experimental results showed homogeneous low voltage electron beam irradiation (HLEBI) applied to the center region apparently enhances the Charpy impact values (a(uc)) 5 to 25%. Fracture mechanism was observed to convert at a(uc) > similar to 5.4-6.7 k.J.m(-2) from clean to secondary microcrack proliferation and/or bends near the main crack, with increasing fracture surface area as a(uc) increased. SEM observation revealed 0.86 MGy HLEBI treated GFRP had much more polymer adhering to fibers than the untreated. This increased matrix adhesion can be explained by electron spin resonance (ESR) peaks indicating dangling bonds are generated creating repulsive forces between outer shell electrons in the polymer matrix, apparently exhibiting increased compressive stress on the fibers increasing adhesion force. Moreover, the lone pair electrons generated in the matrix may have bonded with the fibers more efficiently. For these reasons, increased fiber-matrix adhesion seen in the 0.86 MGy samples appears to assist for more internal cracking, increasing resilience to impact of the GFRP-BMC, raising the a(uc). [doi:10.2320/matertrans.M2012145]