Effect of interfacial residual thermal stress on the fracture behavior of Cf/B4C composites prepared by spark plasma sintering

Carbon fiber reinforced boron carbide (Cf/B4C) composites were fabricated with different Cfs contents by spark plasma sintering (SPS). The interfacial residual thermal stress (RTS) distribution in the Cf/B4C composites and its effects on the fracture behavior of the composites was investigated based on Raman spectroscopy and finite-element (FE) calculation. The results show that the maximum RTS of Cf in as-produced composites were obtained at the edge of fibers. The B4C matrix among fibers suffered a high compressive and tensile RTS simultaneously in radial and tangential directions, which caused the formation of micro-cracks and became the origin of fracture failure of the Cf/B4C composites. The maximum relative density 98.7% and bending strength of 391.41 MPa were obtained when the Cf content was 2.5% while the maximum fracture toughness of 5.46 MPa·m1/2 at 5% Cf content of Cf/B4C sample. The sharp decreases of bending strength when increasing content of Cf cloth was mainly caused by high RTS in the composites.