Compressive fracture in undirectional glass-reinforced plastics

The shear mode of compressive failure in unidirectional fibre composites is discussed. A mechanism is described in which the shear deformation is restricted to a band of material inclined to the plane normal to the fibre axes. The relationship between the orientation of the failed band of material and the limiting shear deformation in the band is explained in terms of volumetric strains. Tests are described which demonstrate that, in GRP, this type of failure can propagate from a notch and this notch sensitivity is put forward as an explanation for the apparent inadequacy of the theoretical model. The sequence of events in the propagation of compressive failure is studied by examining serial sections of an arrested failure. It is found that fibre fracture at the boundaries and interlaminar failure within the band follow as a result of increasing shear deformation in the band.