MATERIAL SELECTION AND GRADE OPTIMIZATION APPLIED TO ALUMINUM-MATRIX COMPOSITES

A general model for the optimal use of materials based on structural o ptimization is derived, The competitiveness of materials is assessed w ith merit parameters. The competition between materials (material sele ction optimization) and the role of the composition and microstructure for a given material (grade optimization) are analyzed. The model is applied to aluminum matrix composites. The influence of matrix materia l, amount of reinforcement, and value of weight savings is studied. Me chanical properties are analyzed with the aid of published experimenta l data and available models. The Tsai-Halpin model is used to represen t the variation of the elastic modulus with the amount of reinforcemen t. For yield strength the modified shear lag model is applied. It can satisfactorily describe experimental data and the variation with reinf orcement for high-strength matrix alloys. For aluminum alloys of mediu m and lower strength, the observed increase is larger than the predict ed one. This can be explained with the help of more recently developed micromechanical models that take into account the changes in microstr ucture in the matrix. For structural parts, large values of weight sav ings are usually necessary to make the particulate-reinforced composit es competitive with carbon steel or their parent aluminum alloys. In o ther applications, combinations of properties are important to make th e composites competitive.