A new approach for biaxial loading of fibre reinforced composites is presented, based on the use of a Modified Arcan Fixture (MAF). In addition to combined tension-shear loading which can be achieved using a conventional Arcan fixture, the MAF allows the application of pure compression and compression-shear loading. Digital Image Correlation is used to obtain the full-field deformations of the specimens to establish the load response and failure behaviour for a range of multiaxial stress-strain states. The approach is demonstrated on glass/epoxy prepreg laminates. For unidirectional matrix dominated laminate it is shown that the failure envelope is described accurately by Puck's inter-fibre failure theory. For the multidirectional matrix-dominated laminate it is shown that the in-situ strength is much greater than that predicted using the unidirectional properties. The potential of the MAF for characterisation over the entire combined tension-shear and compression-shear domains using a single fixture is demonstrated.

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 were studied using open-hole specimens. Combined tension/compression-shear loading was 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 showed 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 was observed under either loading regime. The experimental approach provides a new tool to investigate composite laminates under the full tension/compression-shear loading regime.

A simple nonlinear constitutive model based on non-associative plasticity for UD composites: development and calibration using a Modified Arcan Fixture,

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