THE CRACK TIP ZONE SHIELDING EFFECT FOR DUCTILE PARTICLE REINFORCED BRITTLE MATERIALS

The crack tip zone shielding effect for the ductile particle reinforced brittle materials is analyzed byusing a micromechanics constitutive theory.The theory is developed here to determine the elastoplasticconstitutive behavior of the composite.The elastoplastic particles, with isotropic or kinematical hardening,are uniformly dispersed in the brittle elastic matrix.The method proposed is based on the Mori-Tanaka’sconcept of average stress in the composite.The macroscopic yielding condition and the incremental stressstrain relation of the composite during plastic deformation are explicitly given in terms of the macroscopic ap-plied stress and the microstructural parameters of the composite such as the volume fraction and yield stress ofductile particles,elastic constants of the two phases,etc.Finally,the contribution of the plastic deformationin the particles near a crack tip to the toughening of the composite is evaluated.