Failure Criteria for Glass-Fiber Reinforced Composites under Confining Pressure*

ABSTRACT An experimental study of glass-fiber mat laminates discloses the complexity of mechanical behavior of such composites, including pronounced anisotropy of the discontinuous type, very marked stress sign sensitivity, hydrostatic stress effects, and appearance of different failure modes. The Tsai and Wu criterion, which is widely used in engineering, is no longer adequate to predict properly the actual directional strengths of these materials. A new, more elaborate failure condition is proposed, which accounts for the different observed phenomena, predicts different failure modes, and proves to be reliable when compared with experimental data.