抄録
In the present study, the mechanical property degradation due to fatigue damage in glassfiber reinforced plastics (GFRP) has been evaluated by acoustic emission (AR) techniques. Degradation of strength and stiffness of GFRP laminates subjected to cyclic bending loads was evaluated by measurement of the AE behaviors under the static bending loads. In the ex-periments, three levels of amplitude of applied stress and two kinds of load cycles whose ratios to the fatigue life were 0.6 and 0.8 were adopted for giving the specimens fatigue damage. Under six kinds of cyclic loading conditions the relationship between the AR parameters and the degradation of strength and stiffness was obtained. From the results the followings were made clear. The total AE ringdown counts increased with the degradation of strength and stiffness. The relationship between the total AE ringdown counts and the residual strength suggested that the fatigue damage could be different in spite of the same residual strength. Many AR event counts above 80 dB in amplitude were observed in specimens subjected to the cyclic loadings. The ratio of the AE event counts above 80 dB amplitude to the total AR event counts well indicated the degradation of strength and stiffness due to fatigue damage.
