AN INVESTIGATION OF GLASS-FIBER POLYPROPYLENE INTERFACE STRENGTH AND ITS EFFECT ON COMPOSITE PROPERTIES

The structure and properties of the fibre/matrix interface region play a major role in determining the performance of structural composites. One of the main factors which influences the interface region is the fibre surface coating applied by the manufacturer. The influence of th ese coatings on the interfacial strength of glass fibre/polypropylene composites has been evaluated using the single fibre pull-out test. Re sults indicate that silane coupling agent alone has little effect on t he interfacial strength. However, in combination with some other compo nent of the coating, significant effects were found. The level of glas s fibre/polypropylene interfacial strength varied by an order of magni tude depending on the nature of the fibre coating. Furthermore, the fl exural strength of a unidirectional glass-reinforced polypropylene lam inate varied by a factor of two depending on the type of glass fibre c oating. The flexural strength results correlated well with the level o f interfacial shear strength as measured by the single fibre pull-out test. The interfacial shear strength could also be correlated with the level of fibre surface coverage given by the fibre coating as measure d using X-ray photoelectron spectroscopy.