Anisotropic behaviour of knitted glass fibre/epoxy composites under compressive and shear loading

Te authors have investigated the anisotropic properties of plain weft knitt ed glass fibre fabric reinforced epoxy composites oriented at different off -axial angles and subjected to compressive and shear loads. The compression test results in the off-axial angles of 0 degrees, 30 degrees, 45 degrees, 60 degrees and 90 degrees indicated that the ultimate compressive strength and compressive modulus were greatest at 0 degrees but decreased at other off-axial angles. The compressive strength was higher than the tensile stre ngth for the knitted fabric composite at any off-axial angle. On the other hand, the shear test results for the same off-axial angles showed that the ultimate shear strength and shear modulus were greatest at the off-axial an gle of 60 degrees. A simple analytical model was applied to calculate the c ompressive strength at any off-axial angle, by using three critical strengt h parameters, i.e. the compressive strengths of 0 degrees and 90 degrees an d the shear strength of 0 degrees. The theoretical strength data agree favo urably with our experiments.