Strength prediction in short fibre reinforced thermoplastics

Quantitative measurements of local fibre orientation distribution in injection moulded plaques of short glass fibre reinforced polypropylene have been used in a rule of mixtures model to predict local tensile strength. The model calculated iterative damage accumulation in a specimen cross-section and predicted the final failure stress. Predictions were compared directly with tests on mini tensile test specimens taken from the same positions as the orientation measurements. Good results (<4% error) were obtained in regions of low-medium fibre orientation; however the accuracy of the model was limited where the fibres are more highly aligned. It was concluded that the main source of error arises in these regions from the simplified orientation function used in the model and that further work is required on the development of a more rigorous model of stress transfer and strength for these systems. (C) 1998 The Institute of Materials.