Starting from a ZrB2 matrix, composites containing 10, 20 vol% of SiC whiskers and 20 vol% of SiC-chopped fibers were sintered by spark plasma sintering at 1500°C. The addition of whiskers allowed both strengthening (740–770 MPa) and toughening (5.1–5.7 MPa·m1/2) compared with the reference material. In the fiber-reinforced composite, the increase in fracture toughness (5.5 MPa·m1/2) was accompanied by a decrease of strength (370 MPa). Toughening mechanisms were explored through the analysis of crack propagation. Crack deflection, crack pinning, and thermal residual stresses were the most important mechanisms identified. The experimental toughness increase was successfully compared with the values predicted by theoretical models. Compared with the baseline material, the reinforced composites showed an increased strength at 1200°C in air. The highest value, 450 MPa, was for the fiber-reinforced composite.
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Document Type: Research Article
CNR-ISTEC, Institute of Science and Technology for Ceramics, Via Granarolo 64, I-48018 Faenza, Italy
Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-10691 Stockholm, Sweden
Publication date: August 1, 2010