Steady-state creep of a composite

The termination of composite creep, when no sliding or diffusion can occur on matrix/inclusion interfaces and plastic volume strain constancy is maintained at every point, is addressed. A Fourier analysis is presented which shows that for a non-uniform distribution of plastic strain the elastic energy increases with increasing macroscopic plastic strain. This indicates that steady-state creep is not possible in such a material. Hutchinson's analysis of polycrystalline plasticity is also adapted to reach the same conclusion, by giving some grains an infinitely large flow stress; namely, those grains equivalent to elastic inclusions, on whose interfaces with the matrix neither sliding nor diffusion occurs. The creep strain, at which creep in a composite terminates, is determined. If the above conditions are abandoned, creep can proceed. This is discussed with various examples. Structural changes such as interface debonding and inclusion fracture are discussed as possible causes of continued creep in a composite. It is also pointed out that sliding and diffusion on matrix inclusion interfaces is also a necessary condition for thermal cycle ratcheting. © 2001 Elsevier Science Ltd. All rights reserved.