Decohesion at the Interface of a Spherical, Fibre, or Disc Inclusion

Abstract

Criteria Jor decohesion q{ the illtelJace between the inclusion and the matrix were Jormulated in a relation between a critical plastic strain and all inclusion si ze ill the cases oj a sphere. a fibre , and a disc, the laller two being aligned I)arallel to the tensile axis, by comparing the energies oj the sj)ecimen before and after decohesion. Plastic deformation was always required to produce Jracture at the interface oj the inclusions oj smaller than one micron, and the necessQ/y strain would be inversely proportional to the square root oj the inclusion size, that is, the diameter Jar a sphere and a fibre and Ihe Ihickness Jar a disc . The hardness oj Ihe inclusion was shown. to influence more strongly the critical strain Jar fibre and disc than Jar sphere. The applied stress was Jound to Javor the decohesion. I t could lead to fracture at the interface in the case of lalger inclusions in the absence oj the j)lastic deJormation. The effect oj the Jriction Jorce at the intelJace opposing the pull-out oj the inclusions was also discussed. Cavitation at the interface qf a disc lying normal to the tensile axis was Jound to be a difficult process . since the internal stress did not have a com-I)onent oj a tensile stress along the ten sile direction.