Abstract
In order to identify ruling mechanisms of tensile fracture of Carbon/Carbon composites (C/Cs), tensile tests were carried out for various C/Cs as a function of the density, heat treatment temperature, and interfacial strength between fiber and matrix. Three processing routes of preformed yarn, resin char, and HIP processes were adopted to densify between fiber and matrix was varied by the selection of processing routes and their conditions. As a result, two ruling failure mechanisms were identified. At low density lower than 1.6g/(cm)^3,the tensile fracture was controlled by stress transfer capability from the matrix to reinforcing fibers. However, at higher density than 1.6g/(cm)^3,tensile strength was primary shown to be governed by the interfacial strength between the matrix and fibers. Thus this mechanism is nearly same as ceramic matrix composites, i.e., strong fiber/matrix interface resulted in low ultimate elongation of C/Cs.
