Fiber erosion of carbon fiber composite exposed to simulated ITER-relevant thermal impact by high-intensity pulsed ion beam

A carbon fiber composite (CFC) was thermally tested with high heat flux on a high-intensity pulsed ion beam (HIPIB) apparatus, simulating the ITER specific thermal impacts in divertor region during normal operation or on first wall during off-normal events. The HIPIB shot is capable of delivering an extremely high heat flux onto the target materials at a heat flux parameter of up to 300 MW/m2 s1/2 covering most of the ITER heat loads. The surface morphology of CFC samples after the HIPIB exposure and the resultant weight losses were investigated using scanning electron microscope (SEM) and microelectronic balance, respectively. Moreover, Raman spectroscopy was used to study the microstructural changes of the exposed samples. Comparative tests were also carried out on pure graphite samples. It is found that the CFC samples underwent a severer net weight loss in comparison with the graphite under multi-shot exposure, where the material removal from the CFC proceeded in the form of carbon fibre exfoliation and/or fracture along with matrix spallation as the high heat flux exposure prolonged up to 10 shots. The fibre erosion process is attributable to the anisotropic thermophysical properties of carbon fibre and its interface bonding strength with graphite matrix though the reinforcing carbon fibre ensures excellent high-temperature strength of the CFC over the graphite.