Abstract
During processing of some coated fiber-reinforced metal-matrix composites, a reaction zone develops between the matrix and the coating. Since this reaction zone is usually very thin compared to coating thickness, its presence is not accounted for while evaluating the residual stresses generated due to mismatch between the thermal expansion coefficients of the constituent phases, during cool down of the composites. Residual stress analyses of composites have been reported using at the most a four-phase model ignoring the effect of reaction zone layer. This paper presents a comparison of residual stresses predicted from a four-phase model (without considering reaction zone) and five-phase model (including reaction zone as a separate phase). As the magnitudes of the stresses obtained from the two models are observed to be significantly different, the results are quite suggestive of the need to use five-phase model for the residual stress analysis, incorporating the reaction zone as a distinct phase with its appropriate properties.
A sensitivity study of the residual stresses with respect to coating thickness, coating modulus and reaction zone modulus is also included, based on the regression analysis using least square fit. Results of the sensitivity analysis are consistent with the observations made on the basis of residual stress plots, and convey the need of including the reaction zone as a separate phase. The relative influence of reaction zone modulus, compared to the coating thickness and coating modulus, is observed to be very significant on all the stress components in the coating as well as in the matrix.
Get full access to this article
View all access options for this article.