Evaluation of the matrix crack number in carbon fiber reinforced plastics using linear and nonlinear acousto-ultrasonic detections

The evaluation of matrix cracks in carbon fiber reinforced plastics that influence the performance of the composite structure is important. This study evaluated the number of matrix cracks generated from a three-point bending test using linear and nonlinear acousto-ultrasonic detections and subsequently conducted a comparative investigation. Matrix cracks with typical width of approximately 2 m were generated with an increase in the applied load, as confirmed by the acoustic emission detection. Three repetitions of the experiment demonstrated that the ultrasonic amplitude linearly decreased, and the second- and third-order relative nonlinearity increased in proportion to the number of matrix cracks. Subsequently, the effects of cycle number and center frequency on the ultrasonic sensitivities were discussed. The results indicated that linear detection is preferable because of its reliability and simplicity although both linear and nonlinear ultrasonic detections can be used to evaluate the matrix cracks.

Automated summary

This study evaluated the number of matrix cracks in carbon fiber reinforced plastics using linear and nonlinear acousto-ultrasonic detections. The results showed that matrix cracks increased with applied load, as confirmed by acoustic emission detection. Additionally, the study discussed the effects of cycle number and center frequency on ultrasonic sensitivities.