Investigation of mode III fracture toughness using an anti-clastic plate bending method

In this paper, results of a mode III (tearing mode) fracture toughness investigation with the method of anti-clastic plate bending (ACPB) or equivalently the plate twist method are reported. A testing device using the ACPB phenomenon was constructed and was used to determine the shear modulus of a number of foams and polymeric materials. In this work, potential applications of this method and the associated testing device were extended to the study of the mode III fracture toughness of various materials. The materials investigated included polymethylmethacrylate (PMMA), polycarbonate (PC), and foams consisting of polyvinylchloride (PVC), polyetherimide (PEI) and polymethacrylimide (PMI), polystyrene (PS-X) and laminated composites including carbon fiber reinforced plastic (CFRP), and glass fiber reinforced plastic (GFRP). Values for the compliance, energy release rate, and fracture toughness of these materials were obtained and the functional dependency of these quantities on the crack length was determined. This work shows that the ACPB method can provide a reliable and yet simple testing method not only for the determination of the shear properties of polymeric and laminated materials, but also for mode III fracture toughness investigations.