Mechanical properties of injection moulded styrene maleic anhydride (SMA) - Part II - Influence of short glass fibres and weldlines

The dependence of the various mechanical and fracture properties on the vol ume fraction of short glass fibres in the styrene maleic anhydride (SMA) po lymer was investigated. Special attention has been given to describing the dependence of various mechanical properties on the volume fraction of the g lass fibres, phi(f) by way of the ru le of mixtures. It was found that, str ength, elastic modulus and fracture toughness, all follow a simple rule-of- mixtures of the form Q(c) = lambda Q(f)phi(f) + Q(m)(1 - phi(f)), where Q(c ) is the measured quantity for the composite, Q(m) and Q(f) are the corresp onding values for the matrix and the fibre, respectively, and lambda is the overall efficiency of the fibres, taking into account the orientation and the length of the fibres in the composite. It was a Iso found that, while t he presence of the weldline had no significant effect upon elastic modulus, its presence significantly reduced tensile strength and the fracture tough ness of SMA and its composites. (C) 1998 Kluwer Academic Publishers.