Fracture of Delaminated Unidirectional Composite Beams

Abstract

From optical microscopy and thermal deply characterizations, impact damage formation has been inferred as a process of delamination propagation initiated by transverse cracks. The delamination propagation is modelled by a cracked beam configura tion with the aim of identifying the governing fracture properties. Analysis of the energy release rate of a general beam geometry based on lamination theory is given. Mode II frac ture tests on T300/914C unidirectional composites were performed to support the theoretical prediction with fracture toughness result by ENF tests as a reference. Analysis and test results indicate that in a cracked unidirectional composite beam fracture is a mode II event irrespective of the position of the delamination in the beam thickness, and the energy release rate reaches a maximum when the crack is located at the mid-plane of the beam.