The compression behaviour of unidirectional carbon fibre/epoxy composites is significantly related to the material instability which leads to the formation of fibre kinkbands. At high fibre volume fractions, this instability results from the polymer matrix which is sheared due to the misalignment of the compressed fibres, culminating in yielding or fracture of the matrix or failure at the matrix-fibre
interface. The combined compression-shear test has been proposed to characterise the shear response of the matrix. However, it was found that non-uniform compressive strain was developed and thus the specimens were yielded at lower shear stress. In this study, the shear response of an epoxy polymer matrix under uniform compression deformation was investigated with the modified endcap design. Hollow, thin-walled Prime 37 epoxy specimens were manufactured by machining from cured cylinders.
Experimental results showed that the specimens exhibited uniform compressive strain and shear strain in the gauge section. The average yield stress (48.2 MPa) and the shear modulus (1.3 GPa) of the compressive-shear specimens with the modified endcap design were measured. The data collected in these tests will be used in finite element (FE) modelling to explore how the compression behaviour of
unidirectional composites can be improved.