Compressive strength of three-dimensionally reinforced carbon/carbon composite

Compressive behavior of three-dimensionally reinforced carbon/carbon composite (3D-C/C) was examined from room temperature to elevated temperatures up to about 3000 K. Three-dimensionally reinforced C/C was found to have an inclination to induce kinks at the ends of specimens due to extremely low shear strength. In order to avoid this type of premature fracture and to conduct high-temperature tests, discussion was made on specimen geometry and testing procedure, and the combination of a dumbbell-shape specimen and test configuration without a supporting jig were found to be suitable for the present study. Using this set-up, the compressive strength of a 3D-C/C was evaluated as a function of temperature up to about 3000 K. The compressive strength of the 3D-C/C monotonically increased with the increase in temperature up to 2300 K, but decreased above this temperature. The strength enhancement was suggested to be caused by improvement in the fiber/matrix interfacial bonding, and the degradation over 2300 K was by softening of the matrix at high temperatures.