Effect of hygrothermal ageing behaviour on flexural properties of injection moulded short carbon fibre reinforced polycarbonate composites

Abstract

The demand for carbon fibre reinforced polymer (CFRP) is increasing due to its excellence in specific strength and modulus. Polycarbonate (PC) was chosen as the matrix for the composite due to a good combination of strength and toughness. This research explored the effect of hygrothermal ageing of short carbon fibre reinforced polycarbonate (SCF/PC) composites (with SCF loadings ranging from 5 to 15 wt. %) via immersion of samples in water at room temperature and 60 °C. Kinetics of moisture absorption study revealed that neat PC and its SCF/PC composites exhibit Fickian behaviour. The incorporation of SCF into a PC matrix has resulted in the reduction of both maximum moisture content and diffusion coefficient. Flexural testing was conducted for dry, wet and re-dry conditions. Hygrothermal ageing has reduced the flexural properties of both neat PC and SCF/PC composites. The combined action of moisture-induced plasticization of the PC matrix and interfacial degradation was observed to play a significant role in controlling the flexural properties of the SCF/PC composites. The residual flexural properties of both neat PC and SCF/PC composites are fully recovered after re-drying. Failure mechanisms of both matrix and the composites, assessed by fractographic studies using Field Emission Scanning Electron Microscope (FESEM) are discussed.