Abstract
Fatigue tests on FRP (SMC) were made on the tensile-tensile conditions under two-step loading and the effects of stress change on stiffness ratio were investigated. The results obtained were as follows:
(1) It was found that the degradation behavior of SMC due to cyclic loading is not able to estimate using Miner's law because the fatigue life is usually widely scatter on about a three-digit number. The new method of the estimation of degradation curve was proposed using the linear-properties of them recoggized from the statistical analysis.
(2) The experimental curves of the stiffness ratio before and after change of stress were good fit to the estimated curves except the specimen being relatively weak in the case of the stress increase. Remarkable degradation of stiffness ratio at first cycle after the stress increase is found on the weak specimen.
(3) It was found that the degradation phenomenon on the weak specimen depended on the crack growth phenomena observed on the surface of specimen.
