Measurement of the fiber/matrix interfacial strength of carbon carbon composites by nanoindentation

The interfacial shear strength of the Carbon Carbon (C/C) composites was evaluated by conducting single fiber push-out tests by using a Nano Indenter. Two types of C/C composites were used; a non-heat treated (NHT) (later subjected to heat treatment temperatures at 1800°C, 2100°C and 2400°C) PAN-fiber-reinforced-CVI matrix C/C composites and as-received pitch-fiber-reinforced-charred-resin matrix composites. However, this test was found to be limited to the PAN-fiber-reinforced composite only. A statistical study of the data showed that the interfacial shear strength of PAN-fiber-reinforced-CVI matrix composites decreased with an increase in the heat treatment temperature, although the C/C composite heat treated at 2100°C was found to have statistically similar interfacial shear strength (IFSS) to that of the C/C composite heat treated at 2400°C.; The microstructure at the region of the fiber/matrix interface of C/C composite, especially the interphase was found to have a direct relationship with the interfacial shear strength of the C/C composite. However, a direct connection between the interfacial shear strength (IFSS) and the friction and wear of the C/C composites was not found.