Study on fatigue damage and frequency attenuation characteristics of carbon fiber composite

Fatigue analysis and life prediction are the key and challenging issues in the mechanics research of composite material. In this paper, based on the progressive damage analysis method and fatigue cumulative damage theory, a three-dimensional fatigue cumulative damage numerical model is constructed by introducing the orthotropic constitutive equation, 3D-Hashin fatigue criterion, and material performance degradation scheme. Two loading conditions of tension–tension fatigue and compression–compression fatigue of Carbon Fiber composite laminates were investigated. In the tension–tension fatigue experiments, when the cycle is [Formula: see text] times, the experiment and the numerical simulation all not completely destroyed. However, progressive degradation of stiffness and strength was observed in certain elements, accompanied by some internal damage. On the other hand, the experimental and predicted values for compression–compression fatigue were within a triple error band. Then the cumulative damage evolution law of each laminate under fatigue load was analyzed. Compression–compression fatigue damage initiated from the center of the hole and expanded to both sides of the composite laminate, and its fatigue life increased with the increase of the compression–compression fatigue load. Considering the degradation of stiffness in composite materials under fatigue loading, which leads to frequency attenuation in the structure, this paper established a connection between the fatigue state and frequency to obtain the frequency attenuation curve under fatigue loading. The relationship between frequency and fatigue life was revealed, allowing for the prediction of remaining fatigue life in practical engineering based on the rate of inherent frequency reduction.