Non-Destructive Evaluation of the Bending- Fatigue Damage in Carbon-Fiber-Composite Laminates Based on Ultrasonic Wave Propagation

摘要

An ultrasonic technique was employed to evaluate the three-point bending-fatigue damage of carbon-fiber-composite laminates. Ultrasonic testing experiments and fracture-failure tests were performed on fatigue specimens who were damaged at fatigue loading stress levels of 75 %, 80 %, and 85 % of ultimate bending stress. The ultrasonic velocities, attenuation coefficients, and the residual stiffness were determined for specimens with different degrees of fatigue damage, and the relationships between the ultrasonic velocity and attenuation coefficient and the degree of fatigue damage were investigated. The results show that the ultrasonic velocity decreases and the attenuation coefficient increases with accumulating fatigue damage. The degree of fatigue damage can be modeled as an exponential function of the ultrasonic velocity or the attenuation coefficient. The bending-fatigue damage was found to rapidly increase once the change rate of the ultrasonic velocity or the change rate of the attenuation coefficient had reached 6.2 % or 351.25 %, respectively, and these values can be used as critical values for evaluating the bending-fatigue damage. The proposed method provides a potential way for the non-destructive evaluation of the fatigue damage in composite components in service by the ultrasonic velocity and attenuation coefficient.