A novel fixture for determining the tension/compression-shear failure envelope of multidirectional composite laminates

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.