Effect of Load Sequence on Fatigue Damage of FRP Reinforced Plain Woven Glass Fabric

Abstract

This paper presents the effect of load sequence on fatigue damage of FRP reinforced by plain woven glass fabric. Two stage pulse loading was applied to the specimen. The specimen was subjected to the first pulse load up to 1000 cycles, and then the second pulse load having a different wave profile from the previous pulse was applied to the specimen until it failed.
The following conclusions were obtained from this study.
(1) The fatigue life under the two stage loading can be roughly estimated by the Miner's rule although the experimental fatigue life is about 30% shorter than the predicted one.
(2) The inherent characteristics in stiffness reduction under the second pulse loading cannot be identified due to the large stiffness reduction caused by the first pulse, while the specimen shows the inherent stiffness reduction given only by the second pulse even at the second stage in the case that the pulse load at the first stage does not cause the large stiffness reduction. The similar result is obtainable on the AE records.
(3) It is found that the stiffness reduction is not the appropriate parameter for the degree of fatigue damage. Namely, it is hard to predict the fatigue life from the observation of the stiffness under pulse loadings.