Novel CMCs based on B4C-TiB2 blends and carbon fibres

Abstract

Lightweight carbon fibre reinforced B₄C/TiB₂ composites with varying B₄C contents and fibre gradients were produced by slurry infiltration and sintering for the first time. Tuning the B₄C content allowed to adjust the fibre/matrix interfacial strength, leading to different fracture behaviours: for a B₄C content of 75 %, the fibre/matrix interface was relatively weak and the composite had significantly high fracture toughness, whereas higher TiB₂ contents led to a denser matrix, stronger interface and low degree of delamination. Even though the fracture toughness was considerably high, the addition of Carbon fibres lowered the hardness down to ≈ 4 GPa. Therefore, an additional composite with a fibre gradient was fabricated to demonstrate the feasibility of combining a high fibre content in the inner layer with a harder layer on the outside, reaching hardness values of ≈ 27 GPa.