Low Level Charpy Impact Response of Graphite/Epoxy Hybrid Composites

Laminated graphite/epoxy composites, with and without the addition of plies of glass fabric/epoxy or unidirectional glass yarn/epoxy, were subjected to impact levels less than those necessary to cause total failure. These low level impact specimens, and undamaged control specimens as well, were then subjected to either static flexure or full impact loadings. Using an instrumented impact testing machine, the maximum impact forces and the impact moduli were determined, and compared to the corresponding values from the static tests. The maximum force was independent of loading rate, while the impact modulus was significantly less than the static flexural modulus. The various composites were found to be severely degraded by the low level impacts.