Micromechanisms of interlaminar fracture and fatigue

The interlaminar fracture and fatigue properties of AS/3501-;6 graphite/epoxy are discussed from a mechanistic point of view. Particular emphasis is placed on the interaction between the loading mode and the local geometry of the interlaminar zone and on how this affects the stresses close to the crack tip and the resulting failure path. Delamination growth under Mode I loading is shown to depend on the likelihood of fiber bridging occurring and on how effective these bridged fibers are at diverting strain energy away from the crack tip. The Mode II behavior is controlled by both the work required to shear the fibers from the matrix and the ease with which tensile failure of the matrix between the fibers can occur.