MIXED-MODE DELAMINATION CRACKING IN BRITTLE MATRIX COMPOSITES

The growth of delamination cracks from holes and notches in laminated brittle matrix composites is addressed. It is demonstrated that the behavior is strongly influenced by tractions on the delamination crack faces, caused either by intact matrix ligaments or by bridging fibers. These tractions cause the phase angle of loading psi-associated with delamination to increase appreciably as the crack extends, causing mode I to be suppressed. This effect can lead to increased resistance to delamination as the crack extends, whenever the fracture mechanism along the delamination plane has a psi-dependent fracture energy. Trends in resistance curves are predicted.