Análise termomecânica de materiais com gradação funcional

Abstract

Functionally Graded Materials (FGM) were initially developed to solve problems related to thermal barriers for aerospace structures and fusion reactors and are currently used in structures subjected to high temperatures and thermal gradients. The main characteristic of this class of material is the continuous and smooth variation of its components along a given direction which avoids major discontinuities. Other advantages are the better distribution of residual stresses and greater fracture toughness. This work deals with thermomechanical analysis of structures with functional gradation. Aspects, such as, temperature distribution, stress distribution, critical load and post-critical path of functionally graded plates and shells were evaluated. Heat transfer problems were solved considering a steady state regime. From the thermomechanical standpoint, the structures were evaluated according to the partially coupled methodology. In this approach the thermal analysis is carried out independently from mechanical terms and then the mechanical analysis follows suit, considering the temperature distribution from the thermal analysis. The modeling of structures with functional gradation was performed using the Finite Element Method through the ABAQUS software. For this purpose, user subroutines were developed to account for the gradation in the properties, since this type of material is not available in the software library. Solid elements were employed for both thermal and mechanical analysis. The verification of the adopted methodology was carried out by comparison with examples from the literature. An excellent convergence was found for the aspects evaluated in this work, such as, temperature distribution, stress distribution, critical load, and non-linear equilibrium path. The results showed that the effective material properties are highly dependent on the materials used and homogenization models adopted. Besides that, simplified solutions for obtaining temperature distribution should be used advisedly to avoid errors in the final solution. Regarding stability aspects, it was observed that the boundary conditions, variation of the volume fraction and temperature distribution have a great influence on the thermal buckling and post-buckling behavior of functionally graded plates and shells.