A strength and failure mechanism study of E-glass/epoxy laminates sub jected to uniaxial and in-plane biaxial compression loadings is presented. Specimen con figuration was found to have a large influence on the damage mechanism and resulting strength of the laminates. Standard compression test specimens with a gage section of 12.5 mm (0.5 in.) fail in a shear damage or a kink band mode. In large 125 mm (5 in.) square biaxial specimens, significant delamination not observed in the small specimens reduces the failure strength by 20-35%. The biaxial compressive failure envelope for E-glass/ epoxy is adequately described by a maximum stress or a maximum strain criteria that con siders the different failure modes. Estimates of the failure envelope based on small com pression test specimens where the failure mode is a shear or a kink band overestimates the strength of the large square biaxial test specimens that delaminate at a lower stress.
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