Thermal stress effects in composite materials and engineering components

Thermal stresses can be induced either by temperature gradients in mechanical components and engineering materials or by heating or cooling mechanical components and composite materials which contain at least two different materials or phases with different coefficients of thermal expansion. In this study, processing induced thermal residual stresses due to the mismatch of coefficients of thermal expansion of matrix and reinforcement and their effects on mechanical behavior of composite materials are investigated. The effects of thermal stresses induced by temperature gradients on the service life of an anti pollution combustion chamber are studied.; The first part of the dissertation is a numerical study of processing induced thermal residual stresses in SiC/Al composites and their effects on subsequent mechanical behavior of SiC/Al composites. Processing induced thermal residual stresses and thermal deformation in spherically reinforced SiC/Al composite was simulated using one dimensional nonlinear finite element analysis. The computer aided design package I-DEAS and the finite element analysis package ABAQUS were employed for studying the reinforcement shape effects on processing induced thermal residual stresses and their effects on subsequent mechanical behavior of SiC/Al composite. The overall thermal contraction of SiC/Al composite is shown to be highly cooling rate independent. This numerical result is confirmed by published experimental results. Processing induced thermal residual stresses, on the other hand, are highly cooling rate dependent. As the aspect ratio of inclusion increases, the effective residual stress in the inclusion increases with high stresses in the matrix localized at the tip of the inclusion. In aligned SiC{dollar}sb{lcub}rm w{rcub}{dollar}/Al composite, a tension/compression asymmetry due to elastic unloading effect along the lateral boundaries of whisker is observed.; The second part of the dissertation is material selection of an Antipollution Combustion Chamber for Environmental Engineering Corporation. In this study, the distribution of thermal stresses and strains induced by temperature gradients were numerically simulated using nonlinear time-dependent (creep) finite element method. Based on the service life prediction using fatigue-creep interaction method and corrosion and oxidation resistance, types 310 and 316 are recommended for consideration in future combustion chamber designs.