Impact behavior of glass/aramid hybrid composites

The influence of compositional variations on the impact performance of epoxy-based woven fabric E-glass/aramid hybrids is studied. The penetration resistance, as measured by dart impact tests, proved to be relatively independent of hybrid compn. However, the addn of a random glass mat at each ply interface led to a synergistic effect due to a higher delamination energy at these interfaces. The damage tolerance of basic 8-ply glass/epoxy laminates in falling-wt. impact tests was not significantly altered by the addn. of aramid plies. In fact, at low impact energies, the addn. of aramid plies (and glass mats) resulted in an increase in glass delaminated area and a decrease in residual compressive strength. This was attributed to an increase in bending stiffness with increasing laminate thickness, which may cause a shift in impact damage mechanism from flexural failure mode to contact failure mode. In the case of stiff (hybrid) laminates and contact failure, damage may be located more at the impact side of the laminate, i.e., the glass part of the hybrid, whereas in the case of compliant (nonhybrid) laminates damage is more controlled by flexural failure