Materials Science and Engineering: A ( IF 4.652 ) Pub Date : 2020-01-08 , DOI: 10.1016/j.msea.2020.138935 Vahideh Shahedifar; Mahdi Ghassemi Kakroudi; Naser Pourmohammadi Vafa
In this paper, TaC-based/graphite fibrous monolithic ceramics made of fibers with three core/shell volume ratios (75/25, 70/30, and 65/35) and two orientations of 0° and 0°/90° were prepared. Then, the effects of fiber core/shell volume ratio and fiber orientation on the microstructure and room temperature mechanical properties were investigated. Hot pressing at 1800 °C for 60 min under 40 MPa resulted in the maximum relative density for [0°] specimens with the minimum shell thickness. The work of fracture and fracture toughness of FM specimens with 0°/90° fibers orientations were calculated lower than samples with 0° fibers orientations at the same core/shell volume ratio. SEM observations of fracture surfaces and side surfaces of specimens approved these data. So that delamination and fiber pullout occurred in a minimized extent for the specimens with the bi-directional architecture of [0°/90°] compared to the unidirectional architecture of [0°]. The results disclosed that the fracture toughness of 6.6 ± 0.4 MPa m1/2 and work of fracture of 2145 ± 56 J/m2, as the highest values, were obtained for C70/S30-[0°] specimens.