Fracture mechanisms and damage estimation of fatigue-loaded FRPA by means of acoustic emission technique

The fracture mechanisms and the damage rate of fatigue-damaged FRPA specimens are estimated by analyzing the AE signals detected during the tensile test. The loads Pi, Pb and Pc in change of the damage mechanisms are determined by applying the AE energy gradient method to the nondamaged and the damaged specimens. It is found by AE frequency analysis at the loads that the damage mechanisms for nondamaged specimen are dominated by the fiber breaking, but the damage mechanisms at the lower ratio of N/Nf for the damaged specimens are dominated by the fiber debonding, the damaged mechanisms at the higher ratio of N/Nf are dominated by the fiber breaking and the damage modes at more higher ratio of N/Nf are changed by stress amplitude, where N is the number of cycles and Nf is the number of cycles to failure. It is also found by the relation between the ratio of load P/P(N) and the ratio of number of cycles N/Nf that the damage rate 1-PiPi(N) is estimated higher than the damage rates 1-Pb/Pb(N) and 1-Pmax/Pmax(N), where P and P(N) are the loads in change of damage mechanisms of the damaged and the nondamaged specimens, respectively.