FRACTURE-TOUGHNESS OF 2-D WOVEN SIC SIC CVI-COMPOSITES WITH MULTILAYERED INTERPHASES/

Relations between fracture toughness and fiber/matrix interphases were examined on various SiC/SiC composites made by chemical vapor infiltr ation (CVI) and reinforced with woven fiber bundles. Strong and weak f iber/matrix bondings were obtained using multilayered interphases cons isting of various combinations of carbon and SiC layers of different t hickness and using fibers which had been previously treated, Fracture toughness was estimated using the J-integral and using strain energy r elease rate computed with a model taking into account the presence of a process zone of matrix microcracks. Both approaches evidenced simila r trends. It appeared that higher toughness was obtained with those co mposites possessing strong interphases and subject to dense matrix mic rocracking.