Research On Interfacial Damage And Failure Mechanisms For The SiC Fiber-Reinforced Composites

The damage and failure of the interface is a crucial mechanical problem for exploring the toughening effect in fiber-reinforced composites. For the SiC/Ti-Al composite and ceramic matrix composite, the primary research of this paper concentrates mainly on the matrix crack deflection along the interface and the fiber-bridging toughening mechanism. The fiber pull-out for exploring the interfacial fracture properties, the tensile stress-strain properties of the multi-fiber/matrix composites and the tensile strength, the stress concentration on the intact fibers near a broken fiber as well as the stochastic fiber bridging fatigue lifetime and reliability are investigated. The detailed research results are expressed as:(1) The finite element model of matrix crack deflection/penetration is established and the effects on the relative energy release rate of the relative crack growth length, material parameters and fiber volume fraction are analyzed. The reason why the elastic parameters in the widely used SiC/Ti-Al composite and ceramic matrix composite favor the matrix crack deflection is given. The advantage and disadvantage of the fiber carbon coating are commonly pointed out. The interfacial fracture toughness is effectively evaluated based on the finite element results and the energy-based deflection criterion.(2) The presented bridging constitutive function reflects an infinite-order non-linear relationship between the bridging stress and the matrix crack opening displacement, and interpretes the increasing and decreasing parts as well as their respective fractions. A stable matrix crack growth stage appearing in fiber bridging is confirmed by calculating the bridging resistance curve. The fact that the fiber bridging effect is a dominating toughening mechanism in fiber-reinforced composites is confirmed by calculating the distributions of bridging loads with the matrix crack length. The transformation process from fiber bridging, fiber failure to fiber pull-out is interpreted by calculating the load-displacement curve.(3) The interfacial debonding energy decreases with increasing interface debond length. With increasing friction stress at the debonded interface, the abilities for the shear effects in the...