Crack face interaction and mixed mode fracture of wood composites during mode III loading

A new testing setup to perform and measure mode I, mode III and mixed mode experiments is applied to wood composites with varying particle size. Specimens of particleboard, MDF (medium density fiberboard) and INTRALLAM LSL" are tested under mode I and mode III loading conditions. As testing procedure and specimen geometry allow steady state crack propagation, full load displacement curves can be recorded until complete separation of the specimen takes place. Using a special specimen geometry, large crack lengths may be obtained. The testing method is sensitive enough to investigate the mode I crack opening induced by fracture surface asperities during mode III loading, without external mode I loading and therefore the amount of arising intrinsic mode mixity. (C) 1998 Elsevier Science Ltd. All rights reserved.