Enhancement of fatigue life of polyurethane composites containing carbon nanotubes

The effects of carbon nanotube (CNT) inclusion on cyclic fatigue behavior and the tensile properties of polyurethane (PU) composites have been studied. Tension–tension cyclic fatigue tests were conducted at various load levels (30–50 MPa) to establish the relationship between stress and the number of cycles to failure (S–N curves). The tensile energy to break PU composites was enhanced up to 38% by using a low amount of CNTs. In addition, the incorporation of CNTs increased the fatigue life of PU in the high-stress amplitude, low-cycle regime by up to 248%. Micrographs show highly dispersed CNTs and indicate the key mechanisms for enhancement in fatigue life such as CNT crack-bridging and pull-out. The tensile-tensile fatigue properties obtained in this work show that PU systems can outperform epoxy systems widely used in structural applications.