The Micromechanical Analysis For Fiber Reinforced Metal Matrix Composites With Weak Interfacial Bonding

This thesis aims at the fiber reinforced composites with weak interfacial bonding, which seriously affects the mechanical behaviour. It is necessary to study the effect of weak interfacial bonding on the mechanical behaviour of metal matrix composites(MMCs),The micromechanical finite element method and the nonlinear spring element for the interface are employed to predict the effective behaviour of MMCs. The results indicate that weak interfacial bonding reduce the macromechanial performance of MMCs.By employing an efficient implementation of the generalized method of cells (GMC), this model supercedes it predecessor in terms of efficiency. The bilinear elastic-plastic constitutive model and the Bodner-Partom elastic-viscoplastic model are coupled with modified GMC. The calculated tension and shear stress-strain curves of MMCs using GMC are compare with that using FEM, The results are satisfactory.Three different models for interfacial debonding in composites have been incorporated into the modified GMC. A weak interfacial bonding reduces the elastic modulus of MMCs.The constant compliant interface(CCI) model included a finite interfacial strength for the interface. The response of MMCs has a turning point, associated with the initiation of interfacial debonding, which is decided by the interfacial strength.Unlike the two predecessors, the evolving complaint interface(ECI) model allows unloading of interfacial stresses. The stress-strain curve identified a three-stage deformation process with transverse loading. During stage I, the macro-stiffness of MMCs is reducing because of interfacial debonding. Stage II begins at a peak associated with the maximal interfacial stress. Then, the unloading of macro-stress occurs. In stage III, the interface is completely separate. The curve is characterized by the matrix deformation.