Finite Element Analysis of Functionally Graded Shell Panels Under Thermal Loading

Abstract

Functionally Graded Materials (FGM) have continuous variation of material properties from one surface to another unlike a composite which has stepped (or discontinuous) material properties. The gradation of properties in an FGM reduces the thermal stresses, residual stresses, and stress concentrations found in traditional composites. An FGM’s gradation in material properties allows the designer to tailor material response to meet design criteria. For example, the Space Shuttle utilizes ceramic tiles as thermal protection from heat generated during re-entry into the Earth’s atmosphere. However, these tiles are prone to cracking at the tile / superstructure interface due to differences in thermal expansion coefficients. An FGM made of ceramic and metal can provide the thermal protection and load carrying capability in one material thus eliminating the problem of cracked tiles found on the Space Shuttle. This paper will explore analysis of shell panels under thermal loading and compare performance of traditional homogeneous materials to FGMs using ABAQUS [1] finite element software. First, theoretical development of FGMs is presented. Second, finite element modeling technique for FGMs is discussed for a thermal stress analysis. Third, homogeneous curved panels made of ceramic and metal are analyzed under thermal loading. Finally, FGM curved panels created from a mixture of ceramic and metal are analyzed. FGM performance is compared to the homogeneous materials in order to explore the effect continuously grading material properties has on structural performance.