Abstract
Damage progression and final failure of plain woven glass-fabric-reinforced composites subjected to tension/tension (or compression/tension and tension/shear combined stresses) were studied. Normal stresses (a, and a2) were applied to tubular specimens parallel to the material axes as well as shear stress (T12). At tension/shear combined stress state, the S-S relation up to failure was strongly affected by the biaxial stress ratio, a (=/ra1T2). However, in the tension/tension combined stress state, the S-S relation was not strongly affected by the alternative biaxial stress ratio,fl (=u1/a2), although the stress combination at final failure changes with respect to/p. The S-S curve under tension/tension combined stress is represented by two straight lines that intersect each other at the knee point. The Tsai-Wu failure criterion fits well the experimental failure envelope under tension/shear combined stress. while the maximum stress theory fits better than the Tsai-Wu failure criterion under tension/tension (and compression/tension) combined stress. The initial yield stress condition under tension/tension combined stress was represented by a square that was based on the knee stresses at/? = 1/0 and 0/1. Internal damage and its accumulation do not affect the biaxial strength under tension/tension and tension/shear combined stresses.