The compressive failure of polymeric composites under hydrostatic confinement

Abstract

In order to better establish the fundamental mechanisms responsible for the onset of microstructural instability during compressive loading, several fibre-reinforced polymeric matrix composites were tested under conditions involving hydrostatic confinement. It was found that the dependence of strength upon pressure was mild, indicating that the overwhelming factor in the compressive failure of these materials, irrespective of fibre type, matrix, composition and composite architecture, is resistance to shear loading; dilatational mechanisms, certainly ones associated with microfracture, are relatively insignificant. Specific strength levels do appear to be controlled by both inelastic and plastic flow properties of the matrix, and reflect the degree to which the matrix can restrain either the flexure of locally misaligned fibres, or the shear displacement of non-axial cross-plied fibres in more complex composite lay-ups.