Thermal Stress in Functionally Graded Plates with a Gradation of the Coefficient of Thermal Expansion Only

Background: Experimental thermal stress analyzes of functionally graded materials should be performed accurately to validate existing numerical and analytical analyzes. The variation of stress concentration at the tip of a surface cavity should be investigated for long-term structural design. Objective: In this study, an experimental and numerical model is developed to understand the thermal stress distribution in a functionally graded plate where only the coefficient of thermal expansion is graded. Methods: Three-dimensional photoelasticity was used for experimental work with mechanical modelling of thermal expansion. An analytical solution for the thermal stress in a free plate was derived to validate the experimental and numerical analysis using finite element software. Results: The stress concentration at the tip of the cavity changes with variation in tip radius and tip-to-interface distance, as shown experimentally. The stress at the tip of the cavity decreased when a mid-layer was added to a two-layered composite plate. An analysis of a particular substrate coated with a material whose coefficient of thermal expansion is graded with respect to two different functions shows that the optimum gradation should lie between the parabolic and linear functions. Conclusions: The developed experimental and numerical models are very practical for the objective of thermal stress analysis in functionally graded plates. The stress concentration is reduced by coating the plate with a functionally graded material.