抄録
Columnar specimens were made of resin composites by light curing. The specimens were subjected to static compressive stress. The compressive stress was unloaded when the stress attained to the specified value. Then loading and unloading were repeated with the specified stress increased gradually. Young's modulus was evaluated by gradient of stress-strain curve just after starting unloading. Moreover, apparent density was also measured by the Archimedes' method. Then variation in Young's modulus and apparent density with maximum applied stress increased was clarified. On the other hand, change in residual strain after unloading was clarified in two cases. One is the case in which loading and unloading were repeated in a specimen with the maximum stress increased, and the other is the case in which a set of loading and unloading was made in a specimen once. In the latter case, the maximum stress was changed when a specimen was changed. Finally, a scalar damage variable was evaluated by the variation in Young's modulus from the initial value, and the features of damage development were discussed.
