A degraded GFRP stack was investigated and the degradation behavior was discussed. The fracture aspect were precisely observed not only mechanically,but also microscopically and chemically. Severe damages were found in the middle part of stack, and it is considered that the dew with high concentration acid was produced there and it attacked the GFRP. The lower part would be exposed both high temperature and low temperature environment, and thermal shock might be applied. Hence, the degradation behaviors varied with the position of the stack, because the each position is expected to different environment.
