Limit stress conditions for weakly bonded fiber composites subject to transverse biaxial tensile loading

This paper focuses on the limit stress conditions of metal matrix composites reinforced with weakly-bonded continuous fibers subject to general biaxial tensile loading normal to the fiber direction. The study is performed using unit cell models, with the fibers being treated as either perfectly rigid or perfectly compliant. The cells are first analyzed using finite element methods (FEM) and the results used to construct yield surfaces in stress space. A simpler analytical model based on net-section yielding is also developed and the results compared with the ones obtained by FEM. Though the latter approach provides a reasonable first order estimate of the limited stress, it generally underestimates the values obtained from the FEM calculations : a result of stress gradients acting along the failure plane. The effects of stress gradients are incorporated into the net-section yielding model through an analytical solution based upon the slip line field around a circular hole. This approach yields analytical predictions which are generally in very good agreement with the FEM results. (C) 1998 Elsevier Science Ltd. All rights reserved.