The present study analyses the tensile properties of polycarbonate and of polycarbonate reinforced with 20 and 30 wt.% short glass fibre. The specimens were prepared under various injection moulding conditions, such as filling time, melting temperature and mould temperature. The fracture mechanism was examined by scanning electron microscopy. The results indicated that the polycarbonate reinforced with 30 wt.% short glass fibre shows the highest strength, together with the highest Young's modulus and yield strength. The ultimate strength of the 30 wt.% reinforced-material is approximately 20% higher than that of the 20 wt.% reinforced equivalent and about twice as high as that of unreinforced polycarbonate. Also, the ultimate strength measured in the direction of injection flow was about 10% higher than that measured normal to it. The optimum injection moulding conditions for ultimate strength are: filling time 5 s, melting temperature 290 degrees C and mould temperature 80 degrees C. The ranking of the ultimate strength is strongly related to the layer thickness in which the fibres align with the tensile direction. The higher the fibre content, the higher the strength. The striations, cleavage and tearing fracture mechanisms dominate in unreinforced polycarbonate when the tensile stress was parallel with the flow direction, while splits and secondary cracks were found when the tensile direction was perpendicular to the flow direction. The fibre pull-out, fibre breakage and striations are the major fracture mechanisms in short glass fibre reinforced polycarbonate.
