Tensile fatigue response of sisal fiber reinforced cement composites

Tensile fatigue behavior of composite materials are of significant interest since in structural applications they are often subjected to cyclic loading. However, very few results for fiber reinforced concrete under cyclic load have been reported. In the present research sustainable cement composites were produced by partially replacing 50% of Portland cement with calcined clays and using natural sisal fibers as reinforcement. These composites presented ultimate monotonic tensile stress of 12 MPa and strain at failure of up to 1.5%. Tension-tension fatigue tests were performed with maximum stress levels ranging from 4 to 9.6 MPa at a frequency of 2 Hz. These tests were carried out up to 10⁶ cycles or until the composite failure, whichever occurred first. It was found that up to 6 MPa the composites were able to survive 10⁶ cycles. Composites that survived 10⁶ cycles were re-tested under monotonic load to establish its residual strength. Optical fluorescent microscopy was used to observe the cracking mechanisms after fatigue tests.