The physical and mechanical properties of GFRP at cryogenic temperatures have been studied for designing a large-sized GFRP dewar. As mechanical properties, the impact strength and the tensile strength have been investigated. From the results, it is shown that GFRP is not brittle at cryogenic temperatures, and the tensile strength increases with decreasing temperature. Therefore, it is adequate as a structural material at cryogenic temperatures. Anisotropy of tensile strength of the GFRP is so large that it has to be taken into account when GFRP is used as a structural material of the large-sized dewar. As thermal property, the thermal contraction has been investigated. The results show that the thermal contraction depends on the glass content and fiber direction. This anisotropy has to be taken into account for designing the dewar.
