Nonlinear Stress-Strain Response and Damage Accumulation of GFRP under Tension-Torsion Biaxial Loading

Abstract

Stress-strain (S-S) relations of a plain woven glass fabric composite were studied under tension-torsion biaxial loadings. Acoustic emissions (AE) were observed. Internal damage of failed specimens was also examined using an optical microscope. Yielding occurred either when the tensile stress component reached the debonding stress of transverse fibers, or when the shear stress component reached the critical stress for initiation of plastic deformation of matrix. A new rectangular yield criterion for initiation of the nonlinear S-S relation of woven fabric composites was proposed based on the experiment. Beyond the yielding point, internal damage affected the S-S relation under shear stress greater than that in normal stress. In the case that the shear stress component was larger than the tensile stress component, fewer AE events occurred. Once AE events were observed, visible internal damage occurred simultaneously and the material soon failed. © 1995, The Japan Society of Mechanical Engineers. All rights reserved.