Mechanical Properties Assessments for Materials of High Porosity and Light Alloys with Predominant Embedded Phases

In the present contribution, upgrading the findings of previous works, [11], new models are proposed for evaluation of effective mechanical properties of light alloys regarded as multiphase composites. This study concerns three - phase composites with high volume fraction of non-matrix phases. The elastic properties assessments of such materials are calculated by analytical approach based on the variant of Differential Effective Medium (DEM) method. Here in the methodology from [10, 11] is further developed for two cases: composite type A and composite type B. The composite A consists of matrix and two inclusion phases. The matrix material is much softer than the inclusions material of the first kind and at it is much harder than the inclusions of second kind. The composite B is a closed cell porous material. It is assumed that the high porosity is induced by spherical pores of two sets very different by size: D_i≫ d_i. At high volume fraction of pore space the average diameter of small pores is comparable to the inter-pores distance (cell’s wall). For assessment of the elastic moduli of both composites A an B a two-step homogenization procedures are applied. New yield conditions for the composites A and B are derived to define the initial plastic state of composites. Hill’s strain energy equivalent condition and leading role of matrix are taken into account describing the transition point from elastic to plastic state.