Modelling fracture in an Al2O3 particle reinforced AA 6061 alloy using Weibull statistics

Fracture in an AA 6061 based metal matrix composite (MMC) containing 20 vol % Al2O3 particles is modelled using an axisymmetrical finite element model and a statistical approach for calculating the strength of reinforcing ceramic particles via the Weibull model. Within this model, variables such as the volume fraction, particle size and matrix alloy properties can be varied. When modelling the fracture behaviour of one particle, it is assumed that the survival probability of the ceramic particle is governed by a Weibull distribution. Fracture statistics of the MMC is examined by plotting the survival probability of an Al2O3 particle vs. the macroscopic axial stress applied on the whole MMC. Based on initial calculations it can be concluded that the relation between the macroscopic applied stress on the MMC and the survival probability of the ceramic particle can be described by the Weibull modulus m, as long as the stress distribution in the matrix surrounding the particle is proportional to the applied load and that triaxial loading of the MMC results in a lower survival probability compared to uniaxial loading. Fracture behaviour of MMCs can well be described and a 'mastercurve' can be made for various characteristic stresses and matrix yield stresses at a specific hardening exponent for the matrix material. (C) 1999 Kluwer Academic Publishers.