| Thermal residual stresses developed during casting of SiC/Al fiber-reinforced and particulate-reinforced composites were studied as a function of cooling rate and volume fraction of SiC reinforcement. Thermo-elastoplastic finite element analysis was used in the investigation. The model accounts for the phase change of the matrix and the temperature-dependent material properties as the composite is cooled from the liquidus temperature to room temperature. Solidification time of composites with different volume fraction of reinforcement was compared to that of unreinforced aluminum. Further, the effects of thermal residual stresses and fiber cross-sectional geometry on the mechanical behavior of composites were also studied. Based on the study, it was found that the matrix undergoes significant plastic deformation during cool down and has higher residual stresses as the cooling rate increases. The model which does not include the phase change of the matrix tends to overestimate the residual stresses in the matrix and underestimate the apparent tensile modulus of elasticity of the composites. The presence of thermally induced residual stresses tends to decrease the apparent modulus of elasticity and increase the yield strength of composites compared to those without residual stresses. In addition, the solidification rate of composites is lower as compared to that of unreinforced aluminum, and the fiber cross-sectional geometry affects the constitutive response of the composites in orientations transverse to the fiber axes. |
