Abstract
In the present report a particular attention is given to the fact that the fatigue damage of cloth GRP is caused by the lowering of fiber strength. From such a viewpoint, measurements were made on the residual strength of the GRP specimens and the strength of the constituting fiber strands in order to clarify the change in fiber strength during fatigue. It was found that the crack length obtained from Griffith strength agreed well with the predicted value calculated from the damage. Fatigue tests were made on the altered specimens whose weft strands were covered with polymer sheets. The warp strands were found to be protected from suffering damage by wefts at woven intersections. The fatigue strength increased by 2.26 times of the original value (at the 107-th cycles.), and thus it was possible to prepare the cloth GRP of high fatigue strength.
