Compression after impact of thin composite laminates

Abstract

The damage tolerance of various lay-ups of thin carbon/epoxy laminates (1.6–2.2 mm thick) is examined by compression after impact (CAI) tests, using a new testing device which adapts to the thicknesses of the specimens and does not require tabs nor any modification of the specimen geometry. The compression stress state was not modified by the presence of the device, as was verified by numerical simulation. With this device, CAI tests were done of different carbon/epoxy laminate lay-ups (quasi-isotropic, cross-ply and woven) and the values of the residual strength and the normalized residual strength of the laminates were obtained as a function of the impact energy. The woven laminate was found to offer the highest residual strength under all the impact energies, and the quasi-isotropic laminate the least loss of normalized strength as the impact energy was raised.