The distribution of plastic deformation in a metal matrix composite caused by straining transverse to the fibre direction

Distributions of equivalent plastic strains in an A16061/SiC fibre composite measured using the electron back scatter pattern (EBSP) technique were compared to plastic strain and stress distributions calculated using a continuum mechanics model solved by finite element analysis (FEA). Close to the interface EBSP measurements indicated higher dislocation densities than expected for strains calculated in such a region using the FEA model, the excess dislocations presumably being necessary to preserve the continuity of the interface. EBSP measurements also indicated considerable dislocation density in matrix regions where the FEA model calculated small plastic strains due to the production of a nearly hydrostatic tensile stress state. Inhomogeneities in the microstructure of the real matrix material can generate local shear stresses and so lead to production of dislocations even though the far field stress state has no shear component. Thus the dislocation density was controlled by the magnitude of the hydrostatic tension rather than the deviatoric stress components.