Investigation of production parameters in fracture behavior of hot‐pressed Al ₂ O ₃ –SiC/graphite fibrous monolithic ceramics: Fibers orientation and cell boundary fraction

Abstract Fibrous monoliths ( FM s) exhibit graceful failure in flexure and have higher toughness values. In this research, a mixture of Al ₂ O ₃ and SiC as the core and graphite as the shell material of fibers were produced by extrusion‐molding technique and after aligning along intended directions (0°, 90°, and 0°/90°) were sintered using the hot‐pressing method at the temperature of 1500°C under pressure of 35 MP a for 1 hour. The significance of fibers orientation angle and the cell to cell boundary volume ratio in defining the fracture behavior of the FM s was detected. Because of the extensive crack interactions with graphite cell boundary such as crack deflection and delamination, with increasing cell boundary content from 25 to 30 vol%, the fracture toughness was enhanced. The highest flexural strength (184.8 ± 0.61 MP a) obtained from samples with 0° fibers orientation compared to 0°/90°. Since in the transverse plies (layers with 90° aligning), the properties of matrix phase are dominant, hence the strength in specimens with 0°/90° fibers orientation decreased considerably due to weak graphite matrix phase. In addition, the fracture toughness value increased up to 8.35 ± 0.74 MP a·m ^1/2 for the unidirectional architecture of (0°) in comparison with cross‐ply (0°/90°) architecture.