Mechanical behaviour of the constituents inside carbon-fibre/carbon-silicon carbide composites characterised by nano-indentation

The Young's modulus, hardness, fracture toughness and ductility of the key constituents were characterised using nano-indentation for three types of carbon-fibre/carbon silicon carbide composite manufactured through different routes and/or using different carbonaceous raw materials. Under indentation, all of the carbon constituents demonstrated much less ductile deformation than the silicon carbide and silicon did in these composites. Between two types of PAN-based carbon fibre, as well as of pyrolytic carbon, a difference of around a factor of two was evident in the Young's modulus and hardness. For the silicon carbide, a difference of around 100 GPa and 5 GPa was recorded for the mean Young's modulus and hardness respectively; for silicon, only a small variation was evident. The estimated mean fracture toughness of the silicon carbide ranged between 0.7 and 1.2 MPa.m1/2, whilst the silicon was approximately 0.6 MPa.m1/2. Results for the constituents were discussed in terms of their elastic/plastic behaviour.