Fatigue behavior of sisal fiber reinforced cement composites

The tensile fatigue behavior of long aligned sisal fiber reinforced cement composites was investigated. The fatigue behavior was examined in terms of the stress versus cycles and stress-strain hysteresis behavior of the composites. Composites were tested at stress levels ranging between 4 and 9.8MPa which represent approximately 30-80% of the monotonic ultimate tensile strength. The composites did not fail in fatigue below a maximum fatigue level of 6MPa up to 10⁶ cycles. Monotonic tensile testing was performed for composites that survived 10⁶ tests to determine the residual strength. Crack spacing was measured by image analysis technique. There was no observed loss in strength, but a decrease in Young's modulus and an increase in first crack strength was observed with increasing fatigue stress. Fluorescent optical microscopy was used to investigate the micro-crack formation in composites subject to fatigue loading.