Open Collections

Abstract

A series of tests was performed to determine the increase in the crack length or fatigue damage of graphite/epoxy composites under tension-tension fatigue using traveling microscope, tetrabromoethane enhanced radiography and compliance techniques. Hercules As/3501-6 graphite fibre/epoxy prepreg was used to produce laminates which were subsequently cut into compact tension sample geometry. [90/0] ply configuration was used in the preparation of the laminates. Fatigue damage was observed to be in the form of a 'damage zone' rather than a single crack, which increased in size in both the 0° and 90° directions during fatigue. The damage followed three stages, during the whole fatigue life. The first stage was the acceleration; the intermediate stage was the deceleration and the final stage was the reacceleration of the damage. As a result of this behaviour the Paris approach was found to be non-valid for this material. Change in the compliance was observed during fatigue and this change revealed the same three stages as the development of the damage zone.