Drop-weight impact damage tolerance of CFRP with rubber-modified epoxy matrix

The residual mechanical properties and damage tolerance of carbon fibre-reinforced composites containing unmodified and rubber-modified epoxy resins were evaluated after drop-weight impact damage. It is shown that the residual flexural strength and modulus (normalized to those without prior damage) are slightly higher for the modified matrix system than for the unmodified control, which is consistent with a smaller stiffness reduction for the modified matrix system evaluated from the compliance analysis against instantaneous crack length. Furthermore, the residual Mode I interlaminar fracture toughness (as determined by the potential energy release rates and the stress intensity factors) is significantly higher (by up to 80%, depending on the crack length) for the modified matrix system. The impact energy threshold is also evaluated based on a simple residual strength model to support the observed results.