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 maint ained at every point, is addressed. A Fourier analysis is presented which s hows that for a non-uniform distribution of plastic strain the elastic ener gy increases with increasing macroscopic plastic strain. This indicates tha t steady-state creep is not possible in such a material. Hutchinson's analy sis of polycrystalline plasticity is also adapted to reach the same conclus ion. by giving some grains an infinitely large flow stress. namely, those g rains 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 abandone d, creep can proceed. This is discussed with various examples. Structural c hanges such as interface debonding and inclusion fracture are discussed as possible causes of continued creep in a composite. It is also pointed out t hat sliding and diffusion on matrix inclusion interfaces is also a necessar y condition for thermal cycle ratcheting. (C) 2001 Elsevier Science Ltd. Al l rights reserved.