Effect of Loading Path on the Stress-Strain Relation and Progressive Damage of a Polymer-Matrix Composite under Tension/Torsion Biaxial Loading

Abstract

Strength and stress-strain properties of plain woven glass-fabric composites were measured under three different loading paths which gave the same final stress state. Thin-walled tubular specimens were used. The present study focused on progressive damage. In all tests, acoustic emissions (AE) were measured to distinguish damage accumulation such as debonding, matrix cracking and fiber breakage. Failed specimens were observed using an optical microscope. Based on the experimental results, a new yield criterion for glass-fabric composites was proposed. Damage accumulation and its sequence were both affected by loading path. The S-S relations up to failure were affected by the biaxial stress ratio a (the ratio between normal and shear stresses) and loading path. However, the strength did not depend on the loading path. The material failure was governed by the final stress condition regardless of the difference of loading path.