Analysis of active cooling through nickel coated carbon fibers in the solidification processing of aluminum matrix composites

Solidification processing is widely used for synthesizing fiber reinforced aluminum matrix composites. Some recent studies have used cooling through reinforcing carbon fibers to obtain better control over the solidification microstructure of cast metal-matrix composites. The present study is focused on understanding the effect of active cooling and the role of nickel coating on the structure of the composite. Multiphysics analysis is conducted to simulate the composite system and obtain temperature distribution and stresses at various stages of cooling. The analysis is limited to cooling of the liquid melt and the solidification processes is not modeled. Results show that the direction of the heat flux along the fiber can reverse as the system is allowed to cool. The results show that the von-Mises stresses do not have a severe gradient in the nickel coating but the shear stress gradient is very steep. If the structure solidifies with steep heat flux gradient and high interfacial shear stresses then the nickel coating of the fibers can fail. The analysis shows that the failure of the nickel coating can occur under the effect of thermal stresses generated in the system as a result of temperature gradients. (C) 2011 Elsevier Ltd. All rights reserved.