Effect of Sea-water Environment on the Tensile and Fatigue Properties of Carbon Fiber Tows

摘要

Carbon fiber reinforced plastics (CFRP) are increasingly used in the marine industry in view of the high strength to weight ratio and corrosion resistance offered by them, apart from the cost-effectiveness. Continuous carbon fiber tows form the basis for built-up composite panels. When CFRP composites are subjected to sea water environment, moisture diffusion into the matrix takes place, which reduces the mechanical properties; this necessitates the need to study the effect of sea water environment on the tensile, fatigue properties of carbon fiber. This paper presents the results of tensile and fatigue experiments carried out on carbon tows in pristine form and after exposure to simulated sea water for several weeks. The effect of twisting of carbon tows on the mechanical properties is investigated. Stress vs. number of cycles to failure graphs were plotted to compare the fatigue performance in dry and wet conditions. The results indicate that, sea water exposure degrades the tensile strength of carbon tows. The reduction in strength is due to the presence of minute salt crystals deposited on the filaments and not due to any chemical degradation or hygro-thermal effect. Fatigue tests conducted in dry and continuously wetted condition show that carbon tow performance is similar in dry and wet conditions. SEM images reveal that the failure of filaments is by normal brittle fracture without any fibrillar splitting.