The Effects of Adding MWCNTs on Fatigue properties of Epoxy and Composites Reinforced with Pre-Stressed Fiber

The Failure due to fatigue is responsible of more than 85% materials failure, which occurs under ultimate strength. The fatigues properties of polymers can be improved by utilize reinforcement materials (fibers, particles, etc) to form composite materials with good properties. The improving in fatigue properties for composite can be done by subjecting the reinforcement fibers to preload and make them under prestressing that give extra stiffness to material. The Nanoparticles can be added to the resin to enhance the mechanical properties. In this research, the tensile prestress of (2.5, 5, 7.5, and 10MPa) was applied on fibers to make material under compression after curing. Nanoparticles of Multi Wall Carbon Nanotubes (MWCNTs) added to epoxy resin and composite (epoxy +carbon fiber) with various weight ratios (0.5, 1 and 2wt.%) . The fatigue test results showed the fatigue life for the epoxy enhanced by 350% at 1wt.% of MWCNTs, while it reach to 2850% for composite at 1wt.%MWCNTs and 10MPa of fibers prestressing . The amount of 2wt% MWCNTs will reduce the fatigue life for epoxy and composite due to agglomeration phenomena of MWCNTs inside the matrix and been as weakness zone inside the resin that may decrease the fatigue properties.