HOLE HOLE INTERACTION IN CARBON-FIBER EPOXY LAMINATES UNDER UNIAXIAL COMPRESSION

This paper describes the static compressive response of T800/924C carbon fibre/epoxy [(+/- 45/0(2))3]s laminates containing a single or two circular holes. Penetrant-enhanced X-ray radiography, laminate deply and scanning electron microscopy are employed to observe damage initiation and propagation. Failure is due to 0-degrees fibre microbuckling surrounded by delamination. For all geometries investigated, the microbuckled region initiates at the hole boundary at approximately 80% of the failure strength. The microbuckle band extends stably under increasing load before becoming unstable at a critical microbuckle length of 2-3 mm. The final fracture surface is almost perpendicular to the loading direction. A two-dimensional finite element analysis is used to study the interaction effect between a pair of 5 mm diameter holes as a function of hole spacing; for no interaction the hole centres should be placed at least four hole diameters apart.