Influence of specimen size on the tension–tension fatigue behaviour of fibre-reinforced plastics at room temperature and at 77 K Original Research Article

Fibre-reinforced plastics are considered as insulating materials for the windings of the superconducting magnets in the ITER device. Because of the pulsed operation, the fatigue behaviour of these materials has to be assessed under conditions including the appropriate radiation environment at the magnet location. Since the established standards, e.g. for tension–tension fatigue measurements, involve sample sizes, which are far too large for irradiation experiments, scaling experiments were made in order to investigate the influence of the sample geometry on the fatigue behaviour of tension–tension fatigue specimens. Various sample sizes, including the standard geometry, were chosen for the experiments at room temperature (RT) and at 77 K. The data show that the sample width does not affect the fatigue behaviour at both temperatures, while the sample thickness leads to an increase of the fatigue lifetime, if the recommended sample thickness is exceeded.