Abstract
The fracture mechanisms and residual strength for the non-fatigue and the fatigued specimens of FRPA made with the direct injection molding method are studied by means of Acoustic Emission (AE) technique during the tensile fracture process.
It is estimated from the AE frequency analysis that the fiber breaking occurs at the first and the last stages and the fiber debonding occurs at the second stage for the non-fatigue specimen, but that the fiber debonding and the fiber freaking occur at the first stage and the fiber breaking dominates the second and the last stages for the fatigued specimens.
The damaged (whitened) zone and the crack propagation at the notch tip are only observed at the last stage of the non-fatigue specimen, but the whitened zone becomes larger and the crack propagates at the all stages of the fatigued specimens.
As the correlation coefficient between the normalized loads Pb/Pb(N) and Pmax/Pmax(N) which the load of fatigued specimen is normalized by the load of non-fatigue specimenm is higher than the correlation coefficient between Pi/Pi(N) and Pmax/Pmax(N), the load ratio Pb/Pb(N) gives better estimation of the residual strength, where Pi is the load at first AE initiation, Pb is the load at the change in damage mechanisms, Pmax is the maximun load and the mark (N) is the value of the non-fatigue specimen.
