Large scale bridging in brittle matrix composites

Abstract

The influence of the bridging zone length on the resistance curve behavior of three brittle-matrix composites is examined. The experimental measurements are correlated with models of crack bridging (taking into account the finite specimen dimensions) and compared with the resistance curves expected when small-scale bridging conditions prevail. The results demonstrate that the resistance curves of composite materials strongly depend on both the absolute length of the bridging zone and the length of the bridging zone relative to the total crack length and the specimen width. The latter effects are due to large-scale bridging. The results suggest that the resistance curves of toughness measurements obtained from small test specimens may overestimate the true behavior and thus, caution must be exercised in interpreting some of the recently published data. The implications for future resistance curve measurements are discussed.