Ply thickness and fibre orientation effects in multidirectional composite laminates subjected to combined tension/compression and shear

The effects of laminate lay-up and multiaxial loading on the failure of multidirectional laminates can be significant. Thus, ply thickness and fibre orientation effects in quasi-isotropic carbon/epoxy laminates subjected to combined tension-shear and compression-shear loading are investigated. Three laminate lay-ups with equivalent thickness and homogenised elastic properties, but with different ply thicknesses and ply orientation angles are studied using open-hole specimens. Combined tension/compression-shear loading is applied using a new Modified Arcan Fixture (MAF). A methodology for identifying the failure behaviour based on stereo Digital Image Correlation (DIC) is devised. The results show that ply thickness has a strong effect on the failure behaviour in combined tension-shear, whereas the effect is small in compression-shear loading. No significant effect of the relative fibre orientation angles is observed under either loading regime. The experimental approach provides a new tool to investigate composite laminates under the full tension/compression-shear loading regime.