Crack growth in composites Applicability of R-curves and bridging laws

Abstract

Problems arising during characterisation of fracture resistance due to fibre bridging are reviewed and discussed. A distinction is made between small scale bridging and large scale bridging. Simple criteria are used to distinguish between the two types of bridging. Under small scale bridging the crack growth resistance can be characterised by an R-curve. However, under large scale bridging the shape of the R-curve depends on specimen geometry. Therefore, it is preferable to characterise large scale bridging by a bridging law. Methods for determining bridging laws are discussed. Experimental results indicate that the bridging law is independent of specimen geometry, i.e. a material property. Finite element procedures for implementation of bridging laws in component design are outlined.