Nicolas Carrère

The influence of the interphase and associated interfaces on the deflection of matrix cracks in ceramic matrix composites

A model is proposed to determine the influence of an interphase on the deflection of a matrix crack in ceramic matrix composites. Then, a finite element analysis is performed for a microcomposite geometry with an annular crack which initiates in the matrix and propagates in the interphase. It is applied to a SiC/C/SiC microcomposite with a pyrocarbon interphase. Criteria for penetration and deflection of the matrix crack are expressed in terms of toughness of the interphase and of the various interfaces (matrix/interphase and interphase/fibre interfaces). The predictions are found to agree with crack deflections observed in practical SiC/SiC composites and with the available interphase toughness data. Results also suggest that the real crack deflection mechanism involves debonding ahead of the propagating matrix crack.

Development of a Macroscopic Damage Model for Woven Ceramic Matrix Composites

The aim of this article is to propose a macroscopic damage model, which describes the nonlinear behavior observed on woven composites with ceramic matrix. The model is built within a thermodynamic framework with internal variables. First of all, the efficiency of the model to describe the mechanical behavior of carbon fiber-reinforced ceramic matrix composites is outlined. Then, the predictive capability of the model is evaluated with the help of an alternate torsion test.

Initiation of edge debonding: coupled criterion versus cohesive zone model

Cohesive zone models and criteria based on finite fracture mechanics are two alternatives to analyze edge debonding. A comparison between the two approaches is presented in this paper. The coupled criterion which combines a stress and an energy conditions to estimate crack initiation is used and compared with a bilinear cohesive law. Predictions of the debonding onset are in good agreement provided the characteristic fracture length of the interface remains smaller than the characteristic dimension of the specimen.

Creep behaviour of a unidirectional SM1140+/Ti-6242 composite

Abstract The creep behaviour of a unidirectionally reinforced SM1140+/Ti-6242 composite at 500 °C in a vacuum atmosphere is investigated. Results are presented for creep tests performed in longitudinal and transverse direction, respectively. Microstructural observations show that the main damage mechanisms are filament fracture in the longitudinal direction and interface debonding in the transverse direction. In both cases, creep life can be estimated with the help of models taking into account the damage mechanisms.