FIBER FRACTURE DURING PROCESSING OF CONTINUOUS FIBER, METAL-MATRIX COMPOSITES USING THE FOIL FIBER/FOIL TECHNIQUE/

The fracture of continuous fibers during processing of foil/fiber/foil (F/F/F) metal-matrix composites (MMCs) has been investigated both exp erimentally and theoretically. Experimental observations revealed that fiber fracture occurs during the heat-up portion of the consolidation cycle primarily in a bending mode in regions where cross-weave wires are present. Based on these observations, a general model that describ es fiber fracture as a function of the processing stress and fiber mat geometry was developed. Model results showed that fiber stresses and, hence, the propensity for fracture are very sensitive to the distance between cross-weave wires in adjacent fiber mats; analytical expressi ons that allow the definition of a critical distance between such cros s-weave wires were derived. The model relations demonstrated that fibe r fracture is more likely in areas of a composite in which the fibers are arranged in a rectangular, rather than a triangular, pattern. The experimental and theoretical results were used to develop guidelines f or the design of F/F/F layups to avoid fiber fracture during processin g.