Interlaminar Fatigue Crack Growth in Random Short-Fiber SMC Composite

Abstract

The interlaminar fatigue crack growth behavior in a random short-fiber SMC-R50 com posite is studied. Experiments were conducted on double-cantilever-beam (DCB) composite specimens under displacement-controlled cyclic loading. Owing to large defor mation experienced in the specimen, a geometrically nonlinear fracture mechanics analy sis is employed to evaluate the associated cyclic strain energy release rate during crack propagation. The effect of mean nominal stress on interlaminar fatigue crack growth is studied. The fatigue crack growth behavior in the composite with different thicknesses and orientations is also examined. For the SMC composite studied, the interlaminar fatigue crack growth rate is found to follow a power-law relationship with the cyclic strain energy release rate. The value of the exponent in the power-law expression is much higher than those obtained for in-plane fatigue crack growth in the same composite and for the homog eneous neat resin. The significant effect of mean nominal stress on the interlaminar fatigue crack growth rate is appreciable and can be accounted for by proper modification of the power-law crack-growth expression. The influence of composite thickness on the inter laminar fatigue crack growth rate is noted, but the specimen orientation effect is negligi ble.