Effect of interface slip and diffusion on the creep strength of composite materials

The quantitative effect of diffusional relaxation and interface slip along the matrix-reinforcement interface on the creep resistance of metal and intermetallic matrix composites containing fibers or particulates is studied. The composite material modeled comprises of a power-law creeping matrix reinforced with rigid reinforcements. The transverse creep resistance of a continuous fiber composite and the axial creep strength of a discontinuous fiber composite are investigated in plane strain and axial symmetry respectively. The relevant unit cell boundary value problems are solved by the finite element method. Results indicate that slip at the interface alone can reduce the transverse creep strength of a continuous fiber composite to levels below that of the pure matrix material. On the contrary, analysis of the axial creep resistance of discontinuous fiber composites indicates that diffusion is necessary in addition to the free slip for the same result.