Mechanical characterization of thin injection-moulded polypropylene specimens under large in-plane shear deformations

Abstract The methodology to extract in-plane shear properties has been standardised for polymer-based composite materials. However, no standards have been designed to extract reliable test data that can be used to calibrate material models in numerical simulations for non-fibre reinforced polymers. The quality of the results from three widely used experimental techniques was examined in this study for mineral-filled polypropylene in terms of shear strain distribution, out-of-plane deformations and shear stress-strain curves with the aid of the digital image correlation method. The V-Notched Rail test (ASTM D7078 ) exhibited ultimate fracture of the specimen, but valid shear strain was only obtained for small deformations. For relatively large strains, more reliable shear test data were obtained from a modified version of ASTM B831 : a standard test designed for aluminium but modified and implemented for polymers. Although out-of-plane deformations were avoided using aluminium holders, large variability was found in the strain distribution along the shear path. In contrast, the modified Wyoming Iosipescu test (ASTM D5379 ) exhibited the most robust shear stress-strain results due to consistent shear strain uniformity and low variability during the entire duration of the test.