Plate Wave Propagation as Damage Indicator in FRP Composites Under Fatigue Loading

摘要

Dispersive behavior of plate waves in composite [±45]_s Gl/Ep specimens is studied through acousto-ultrasonic measurements. Aiming to associate material damage, in this case being matrix cracking, with the propagating wave mode characteristics, acousto-ultrasonic, AU, tests are conducted in the as-received state and repeated after imposing tensile constant-amplitude cyclic loading, interrupted well before failure. Propagating plate waves are captured at several distances from the source and then processed, using two spectral techniques, in order to reconstruct segments of the dispersion curves of the orthotropic medium. Although experimental dispersion curves are in good agreement with theoretical predictions, quantitative damage assessment cannot be achieved. Limitations of the experimental procedure, as well as of the respective data processing, are commented upon. Additional tests, conducted on an isotropic aluminum specimen, are presented to enhance understanding of the complicated phenomenon.