Processing and mechanical properties of short carbon fibers toughened zirconium diboride-based ceramics

The major problems associated with zirconium diboride-based ceramics are lack of damage tolerance as structure components, so ZrB₂/20 vol% SiC based ceramics toughened by 20 vol% short carbon fibers were produced by hot pressing at 2000 °C under 30 MPa for 1 h. SEM results showed that short carbon fibers could disperse uniformly in powder mixtures and sintered sample through milling. Three-point bend strength and fracture toughness were measured. The decrease in strength from 448 MPa to 397 MPa as the addition of short fibers was attributed to the chemical reaction between fiber and matrix. The fracture toughness increased from 4.25 MPa m^1/2 for ZrB₂/SiC to 6.35 MPa m^1/2 for short fibers toughened ZrB₂/SiC, which was led by the crack deflection and fiber fracture.