Mechanical properties of N440/SiO₂ composites with fugitive carbon interphases

Mechanical properties of NextelTM 440 fiber-reinforced SiO2 composites containing fugitive carbon (FC) interphases were investigated. The three-point bending (TPB) test at room temperature indicated that FC interphases were crucial to the strength improvement. After employing FC interphases, the fiber/matrix bonding strength was weak enough for crack propagation, thus leading to the increase of flexural strength by about 2.1 times. The TPB test at high-temperature showed that the flexural strength decreased firstly and then increased as temperature increased, and the fracture mode changed from ductile to brittle. The lowest value of 92.3 ± 13.5 (MPa) was obtained at 1000°C. With the aid of the single edge notched beam test combined with the digital image correlation technique, cracks propagation process during fracture was well clarified.