Compressive fracture of brittle materials

Abstract

Pre-cracked rectangular blocks of two different glassy brittle polymers were compressed under a flat steel platen until failure occurred. Three distinct failure modes, gross yielding under platen, axial splitting and plastic instability (buckling) were observed, depending on the pre-crack length and platen width. The axial splitting failure mode is explained by invoking the energy balance concept of fracture with a two-strut elastic model. In this mode, the elastic fracture surface energy or, equivalently, the stress intensity factor and not the compressive strength, is found to be the fundamental material property dictating compression failure. The role played by the pre-crack length and platen width in controlling the failure mode transition from gross yielding to compression splitting and to buckling is highlighted. Finite element and boundary element calculations support the proposed two-strut model for compression splitting.