Characterization of impact fatigue damage in CFRP composites using nonlinear acoustic resonance method

Accidental impacts may induce impact fatigue damage in carbon fiber reinforced plastic (CFRP) composite and the progressive fatigue damage is difficult to detect by traditional non-destructive techniques. In this work, a nonlinear acoustic resonance method was proposed for characterizing the impact fatigue damage in CFRP composites. Based on the hysteretic nonlinearity of heterogeneous materials, a fatigue model was constructed to evaluate the impact fatigue damage and predict the residual service life of the composite material. Thereafter, experiments of pendulum impact were conducted on the CFRP composites and nonlinear acoustic resonant were measured to evaluate the impact fatigue damage. Additionally, the impact fatigue damage in the CFRP composites was inspected by an infrared thermography and an optical microscopy. The results indicate that the shift of resonance frequency occurs due to the stiffness degradation and the relative frequency shift has a good linear relation with excitation voltage and strain change. In addition, the damage index rises slowly at the beginning of the impact cycle and rapidly increases when the impact fatigue life exceeds 70%. The experimental results demonstrate that characterizing the impact fatigue damage in CFRP composites using nonlinear acoustic resonance method is an effective and reliable approach.