Effect of Different Stress Levels on Fatigue Residual Stiffness of Carbon Fiber Reinforced Composite

Abstract

In order to study the fatigue behavior of carbon fiber reinforced composite and the effect of stress level on its fatigue residual stiffness, monotonic tension tests and fatigue tests were conducted and the fracture morphology of carbon fiber composite was observed by using scanning electron microscope (SEM). The results show that the fatigue performance of carbon fiber reinforced composite is good at room temperature, and the cycle time is more than 106 under 48% ultimate tensile strength. The decline rate of its residual stiffness is different under different stress levels. In the early stage of the fatigue, the decline rate of residual stiffness is relatively lower under high stress level, while it is higher under low stress level. In addition, the boundary characteristics of residual stiffness is also different under different stress levels. The boundaries under low stress are significant, while the boundaries under high stress are obscure. The results of fracture analysis show that with the decrease of stress level, the fatigue failure mode is complicated. Under high stress, the fracture of the fiber cluster is the main feature, while at low stress level the fatigue failure mode includes fiber and matrix fracture, interfacial debonding and fiber pull-out, etc.

Keywords

• carbon fiber reinforced composite
• fatigue behavior
• stress level
• residual stiffness
• fracture