Friction stress for carbon composite and carbon yarn during high temperature creep

Friction stress σ₀ was measured on specially prepared, uniaxial. carbon yarn and carbon-carbon composite specimens up to a temperature of 2310°C. Relations between the friction stress, applied stress and other parameters are derived. The amount of work needed to activate the apparent activation volume V₀ is V₀(σ − σ₀) = 4 kTn'. The friction stress and the applied stress relation is $\text{σ}{}_0\text{= [}\text{(n − n ')}\text{n}\text{]σ}$, and the friction stress and the test temperature relations can be expressed as σ₀ ∝ exp ($\text{l}\text{T}$). These relations are consistent with test results.