Fatigue crack growth acceleration due to intermittent overstressing in adhesively bonded CFRP joints

Double cantilever beam joints were used to investigate cohesive and interlaminar crack growth in bonded composite joints under constant and variable amplitude (VA) loading. Numerical crack growth integration was used to predict the VA fatigue life using constant amplitude data. This underestimated the fatigue crack growth rate for interlaminar cracks, indicating crack growth acceleration due to load interactions. This was also the case for cohesive cracks subjected to a moderate initial strain energy release rate (G(max)). An unstable crack growth regime was also identified for the case of high initial G(max) cohesive crack propagation. This behaviour is attributed to the development of a damage zone ahead of the crack tip. (C) 2004 Elsevier Ltd. All rights reserved.