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

Problems arising during characterisation of fracture resistance due to fibr e bridging are reviewed and discussed. A distinction is made between small scale bridging and large scale bridging. Simple criteria are used to distin guish between the two types of bridging. Under small scale bridging the cra ck growth resistance can be characterised by an R-curve. However. under lar ge scale bridging the shape of the R-curve depends on specimen geometry. Th erefore, it is preferable to characterise large scale bridging by a bridgin g law. Methods for determining bridging laws are discussed. Experimental re sults indicate that the bridging law is independent of specimen geometry, i .e. a material property. Finite element procedures for implementation of br idging laws in component design are outlined. PRC/1540.