On the Application of the Maximum Stress Failure Criterion to Off-Axis and Angle-Ply Laminates

Abstract

It has been commonly reported that the maximum stress failure theory predicts that the tensile stress (applied at 0°) needed to produce fiber failure in low angle off-axis (α) and angle-ply (±α) tensile specimens exceeds the unidirectional tensile strength. We point out that for small angles the usual strength analysis of the off-axis tensile specimen does not employ the stress state found in the region where fracture is ex pected to initiate. Consequently, the customary analysis is suspect. We also show, con trary to previously published results, that classical plate theory used in conjunction with the maximum stress failure criterion does indeed predict that the strength of an angle-ply laminate decreases with increasing angle when fiber failure dominates.