Fatigue damage progress in alumina FRP tubes at cryogenic temperature

Alumina FRP is anticipated to be a good thermal insulating support system under cryogenic conditions, because of its outstanding thermal conductivity, and high specific stiffness and strength. In this paper, the internal fatigue damage progress in Alumina FRP tubes subjected to cyclic compressive loading at room temperature and 77 K were studied. In order to evaluate the fatigue properties at a macroscopic level, the complex modulus and the damping from the hysteresis of the stress-strain curves, were examined. It was found that the complex modulus at room temperature decreased gradually due to internal fatigue damage during stage II. On the other hand, there was no distinct change in the complex modulus at 77 K, with damage occurring just before breaking. The relationship between the fatigue properties at a macroscopic level and the internal fatigue damage was subsequently analyzed. It was found that the density of the matrix cracks influenced the energy loss by the static friction. It is proposed that the energy loss by the static friction is a useful parameter for predicting the fatigue life.