An experimental investigation of the fatigue behavior of sisal fibers

The tensile fatigue behavior of individual sisal fibers was investigated. The fatigue behavior was examined in terms of the stress versus cycles and stress-strain hysteresis behavior of the fibers. Fibers were tested at stress levels ranging between 80 and 400 MPa. The sisal fibers did not fatigue below a maximum fatigue level of 320. The stress versus cycles curve was normalized by dividing the maximum fatigue stress over the ultimate tensile strength of each individual tested fiber and it was found that below a ratio of 0.5 there was no fiber failure below 10⁶ cycles. Monotonic tensile testing was performed for fibers that survived 10⁶ tests to determine its residual strength. There was no observed loss in strength, but an increase in Young's modulus was observed with increasing fatigue stress. The mechanisms for increase in modulus as well as microstructural degradation mechanisms after fatigue were investigated and are discussed.