Effect of impact damage on the compressive response of composite laminates

At present, the compressive strength of composite laminates containing an open-hole can be predicted theoretically by using fracture mechanics based models such as the linear softening cohesive zone model. In this approach, the inelastic deformation associated with fibre microbuckling that develops near the hole edge is replaced with an equivalent crack loaded on its faces by a bridging traction which is linearly reduced with the crack closing displacement. By making use of this model, and by establishing an equivalent hole diameter from X-radiographs and/or ultrasonic C-scan images, the residual compressive strength after impact can be predicted. This paper outlines how the 'equivalent hole' is determined and gives tabulated results of experimental and theoretical data. It is also shown that these data are in good agreement with each other for plain compression, open-hole compression and compression after impact strengths. (C) 2001 Elsevier Science Ltd. All rights reserved.