The Numerical Analysis of Mechanical Behavior and Crack Evaluation through the Two-scales Modeling in Functionally Graded Materials

Abstract

Functionally graded material (FGM) is one of the modern material and a new type of advanced composite material that can be designed for thermal barrier coatings and heat shield applications due to good service performance in high mechanical and thermal properties. FGM is an inhomogeneous material composed of various compositions and structures gradually over volume and their mechanical properties vary smoothly from one surface to the other surface. The purposes of this study are to evaluate the mechanical behavior and the crack of FGM through the effective two-scales modeling carried out by finite element method (FEM). Aluminum as the matrix and silicon carbide as the particle inclusion with different volume fraction were gradually modeled and geometry with three point bending test was assumed. In order to evaluate the mechanical behavior, the fully model as a macroscale and the representative volume element (RVE) model as a microscale were considered. Then comparisons between both scales show satisfactory results. This two-scales modeling is reliable and useful to reduce some enormous numerical computations. In order to investigate FGM as safe application, crack evaluation is necessary. Cracks were modeled through the thickness direction at each layer of FGM modeling, such as passing pure ceramic part, pure metal part, and gradation part with different ceramic inclusions which show the presence of continuous material composition. From the various cracks modeling, the stress intensity factors as failure behavior criteria were obtained and analyzed. According to the continuous FGM structure composition, the calculation of exponential of elastic modulus variation also was considered analytically to validate the stress intensity factors. Then the both stress intensity factors were compared and discussed.