Tong-Yi Zhang 教授 特別講演会

A formula is derived to calculate the phase angle of interfacial mixed mode fracture in the indentation delamination test, in which the delaminated film buckles. Interfacial fracture toughness depends on the phase angle and calculating the phase angle is necessary for the determination of mode I interfacial fracture toughness.

ZnO films with different thicknesses were deposited on 525 μm-thick (100) Si substrates. Then, Vickers indentation tests were carried out on the ZnO/Si systems at room temperature. For the systems with film thicknesses being equal to and thicker than 0.832 μm, only indentation-induced delamination occurred when indentation loads were low. Under high indentation loads, radial cracking concurrently occurred with delamination. The radial cracks were invisible at the film surfaces because the crack length was smaller than the delamination size. Combining the composite hardness models with the indentation-induced delamination model, we developed a method to determine the interfacial fracture energy between a film and its substrate. The novel method is particularly useful for indentation equipment without any displacement measurement devices. Using the new method, we extracted the interfacial fracture energy to be about 12.2 J m-2 and from 9.2 to 11.7 J m-2 for the cases without and with buckling of delaminated films, respectively. Consequently, the pure mode I interfacial fracture energy was calculated to be 10.4 J m-2 for the ZnO/Si systems.