Fatigue analysis of a composite ring: Experimental and theoretical investigations

The behavior of composite rings against fatigue loading is analyzed. Experimental study is performed to evaluate the ultimate hoop strength of the composite ring as a requirement before fatigue testing. Then, fatigue tests are performed at three different load levels. Afterward, progressive damage modeling in the context of continuum damage mechanics is utilized to theoretically estimate fatigue lifetimes of the investigated rings. The modeling consists of three parts as stress analysis, damage estimation and degradation of mechanical properties. It is mainly aimed to reduce the required runtime for the accomplishment of fatigue analysis while the accuracy is at least compromised. Therefore, a manual technique is adapted for extracting stress components on the ring. Degradation of mechanical properties takes place either through gradual procedure or sets of sudden laws. The gradual degradation of mechanical properties is performed based on the damage progression as a function of cycle numbers and stress state. Sudden degradation is done after occurrence of failure. After reduction of mechanical properties, the model is updated and whole procedure repeats till the whole layers fail. Finally, the results of fatigue modeling are compared with performed experimental study and a very good agreement is observed.