Torsional fatigue in bamboo fibers reinforced epoxy resin composites

Natural fibers are low-priced, abundant and renewable. The application of natural fiber to reinforced polymers materials can reduce cost, decrease weight and increase the mechanical properties of the composites. Many studies were carried out in natural fibers reinforced polymer composites using different natural fibers, one of those is bamboo fibers. Nevertheless, torsional fatigue tests have not been applied to predict the mechanical behavior of the bamboo fibers reinforced polymer composites. In this study, bamboo fiber reinforced epoxy resin composites were molded by compression in a rectangular mold. These specimens were machined according to the schematic of thin-walled tubular specimen suggested by ASTM-2207-15 and tested in torsional fatigue loading with R = -1. A mechanical torsion fatigue testing machine was constructed to perform torsion test with constant amplitude of the twist angle. An angle measuring device was constructed to measure the angular displacement in the useful region of the specimens (gage length). Torsional fatigue life curves were plotted for pure epoxy resin, unidirectional and discontinuous bamboo fibers reinforced epoxy resin composites. Pure epoxy resin specimens presented the longest torsional fatigue life and the poorest results were found in discontinuous bamboo fibers composites. The experimental results suggest that the epoxy resin is strongly related to the torsional fatigue behavior of the composite materials. The fracture surface of test specimens often showed that cracks occurred in the interfacial region of the composites.