A micromechanical approach is used to study the damage initiation and nonlinear behavior of SiC/Ti composites subjected to a general complicated off-axis loading at elevated service temperatures. The effects of stress relaxation, interface damage together with fiber coating are considered. A cohesive zone model is applied to define the imperfect interface between the fiber and matrix. Introducing a unique failure criterion for all loading angles at different elevated service temperatures may be considered as the main contribution of this study. In order to simultaneously apply a combination of mechanical loadings and thermal residual stresses, appropriate periodic boundary conditions are imposed on the model. Predictions of the presented model show acceptable correlation with the reported experimental data at elevated temperatures. Results reveal that by increasing the service temperature, the strength of the composite is linearly degraded at fast rate especially at loading angles of 20° and 30°.@en

A finite element, micromechanical model is developed to predict the inelastic behavior of SiC/Ti composites subjected to off-axis loading using a three-dimensional representative volume element (RVE). The model includes the effects of manufacturing process thermal residual stresses together with interface damage and fiber coating. The cohesive zone model is used to consider the imperfect interface between the fiber and matrix. Introducing a unique failure criterion for various off-axis angles is the main novelty of this study. Apart from interface damage, plastic deformation of the matrix is also considered as another source of nonlinearity. Appropriate boundary conditions are imposed on the RVE to allow simultaneous application of a combined normal axial and transverse and axial shear loading plus thermal residual stresses. Results of the presented finite element model are compared with experimental data for stress-strain response, initiation of nonlinearity, and ultimate strength in various off-axis angles which show good agreement. Moreover, parametric studies are conducted to examine the effects of thermal residual stress and fiber volume fraction (FVF) on the mechanical response of the material.@en