AN ANALYTICAL STUDY OF RESIDUAL-STRESS EFFECTS ON UNIAXIAL DEFORMATION OF WHISKER REINFORCED METAL-MATRIX COMPOSITES

Finite element modeling was utilized to simulate the stress strain response of discontinuous SiC whisker reinforced aluminum-matrix composites, accounting for the thermal residual stresses (TRS) generated during solution treatment. The contributions of various micro-mechanisms to overall composite strengthening and deformation, and the impact of TRS on each mechanism were explicitly evaluated. It was inferred that constrained matrix plastic flow and matrix-to-fiber load transfer are the predominant sources of strengthening, with enhanced matrix dislocation density playing a secondary role. Residual stresses were found to significantly affect each of the operative strengthening mechanisms and hence the composite properties. Comparison with experiments revealed that the trends predicted by the model are generally consistent with actual composite behavior, although the model overpredicts work hardening rate. A parametric study of the effects of whisker volume fraction, aspect ratio and spacing on tensile and compressive deformation was also conducted. The results showed that increasing volume fraction, close end-to-end spacing and large aspect ratios result in greater strength and stiffness.