Mechanical behaviour of carbon fibre reinforced TaC/SiC and ZrC/SiC composites up to 2100°C

The microstructure and elevated temperature mechanical properties of continuous carbon fibre reinforced ZrC and TaC composites were investigated. Silicon carbide was added to both compositions to aid sintering during hot pressing. Fibres were homogeneously distributed and no fibre degradation was observed at the interface with the ceramic matrix even after testing at 2100 degrees C. The flexural strength increased from 260 to 300 MPa at room temperature to similar to 450 MPa at 1500 degrees C, which was attributed to stress relaxation. At 1800 degrees C, the strength decreased to similar to 410 MPa for both samples. At 2100 degrees C plastic deformation resulted in lower strength at the proportional limit (210-320 MPa), but relatively high ultimate strength (370-440 MPa). The sample containing ZrC had a lower ultimate strength, but higher failure strain at 2100 degrees C due to the weak fibre/matrix interface that resulted in fibre-dominated composite behaviour.