Water exposure, tensile and fatigue properties of treated hemp reinforced vinyl ester composites

Recently, due to the safety issue, the incorporation of fire retardant in natural fibre composites is becoming necessary. Nevertheless, since it is potentially utilised as low load bearing material, less work has been done on the fatigue properties and the effect of water to its mechanical properties. In this work, untreated and fire retardant treated (FR) composites made of woven hemp fabric (WHF) were investigated for their tensile and fatigue properties. Tensile properties of fabricated composites were studied with an addition of water absorption factors. Both composites were immersed in the water for up to 2688 hrs and tensile properties were analysed periodically. Based on the results, tensile properties of both fabricated composites are reduced after being immersed in the water for 2688 hrs. Comparing both samples, the FR treated composites exhibited lower tensile properties than the untreated. In terms of fatigue test, each sample was tested at 50, 60, 70 and 80% stress levels in tension-tension mode for both composites. It was observed that, as the number of fatigue cycles increased, the fatigue strengths of both composites gradually decreased. Their fatigue strength coefficient was also similar (0.12) indicates that the treatment did not affect the fatigue strength of composites. The safety limits for these fabricated composites to be utilised for any application is about 24 to 30 MPa.