Effect of strain rate on the fracture process in interlaminar shear specimens of carbon fibre-reinforced laminates

Crack detection gauges have been used to determine the start of catastrophic shear failure and to follow its propagation on the interlaminar plane in single-lap shear specimens of unidirectional carbon/epoxy and carbon/PEEK laminates loaded at both quasi-static and impact rates. The interlaminar failure surfaces have been examined using optical and scanning electron microscopy. For carbon/epoxy specimens shear cusps characteristic of mode II shear failure were observed, while for carbon/PEEK specimens a small degree of plastic matrix deformation, typical of fast fracture, was obtained. These results are used to interpret those obtained from the single-lap shear specimen and to discuss the signifcance of previously published results on the rate dependence of the interlaminar shear strength for carbon/epoxy and carbon/PEEK laminates. Copyright (C) 1996 Published by Elsevier Science Limited.