Fracture Mechanics of Sublaminate Cracks in Composite Materials

Abstract

This paper presents an overview of a fracture-mechanics approach to some of the most frequently encountered matrix-dominated sublaminate cracks in epoxy-based composite laminates. By “sublaminate,” it is meant that the cracks are internal to the laminate, generally invisible macroscopically, but are much larger in size than those microcracks considered in the realm of micromechanics. The origin of sublaminate cracks is assumed to stem from the coalesence of natural material flaws (also microcracks), which occur under a certain favorable laminate stress condition. Thus, the modeling of the mechanisms of sublaminate crack initiation and propagation is essentially mechanistic and probabilistic in nature. Some specific results from several analytical/experimental investigations using graphite-epoxy laminates are presented and discussed in this paper.