NEW DEVELOPMENT OF THE J-BASED FRACTURE TESTING TECHNIQUE FOR CERAMIC-MATRIX COMPOSITES

The J-based fracture testing technique is newly extended to experimentally determine the tension-softening (sigma-delta) relations in ceramic-matrix composites. The J-based technique originally proposed for concrete has been well established for quasi-brittle materials where the fracture process is primarily dominated by the formation of a fracture process zone and the contribution of the crack tip toughness is negligibly small. In this study, the J-based technique is further developed to cover a more general case, i.e., a material in which the crack tip stress singularity coexists with the fracture process zone. This is the case, in particular, for modern fiber-reinforced ceramic composites and coarse-grained ceramics. The newly derived testing technique has been applied to foam glass composites reinforced with SiC and stainless steel short fibers. The validity of the deduced tension-softening relations has been examined by microscopy observations and by comparing with other conventional testing methods: the fracture energy method and the R-curve approach. It is suggested that the J-based fracture testing technique can provide reasonable tension-softening relationships and fracture parameters in modern ceramics and ceramic-matrix composites.