Shear stiffness of a glass-reinforced thermoplastic

Abstract

Inclusion of glass fibres in plastics has been thought to produce little improvement in their stiffness in shear compared with that in tension but results obtained with polypropylene filled with fibres show that they increase in shear stiffness to a significant extent and in some directions more than its tensile stiffness. The filling of polypropylene with glass spheres instead of fibres results in smaller but still significant increases In shear stiffness, which are comparable to the relative increases in tensile stiffness. In both cases the experimentally determined values of shear stiffness fall within the bounds derived from energy considerations and correlate closely with the results obtained from a simple model of a composite material