On Microcrack Growth and Arrest in Simulated Fibrous Composites.

Opening, shearing and combined mode fracture tests were conducted with long rectangular strips of plexiglas clamped on the long edges and containing centered and off-centered cracks. The critical stress intensity factors, crack initiation angles, and crack paths were evaluated. Fractured surfaces were then examined as to crack behavior. The maximum energy release rate criterion was extended to problems with a large degree of shearing mode present. This criterion was then used to predict successfully the initial and subsequent crack propagation behavior presented in the experimental work. Crack arrest was examined for this rigid grip configuration. Using in part information obtained from these studies, a flexible fiber model was investigated to determine the effect of fiber bending on crack behavior. Certain aspects of crack growth and arrest in these idealized fiber models were explored. Author