Modeling and analysis of creep in composite cylinders

Abstract

Composites are the materials, which are made by combining two or more materials to get properties that are not attainable in any of its constituents alone. Recently, a new class of composite materials known as functionally graded materials (FGMs) have led to the development of superior heat resistant materials and is the choice for many engineering applications such as automobile, aerospace, marine and oil industries. In most of these applications cylinder has to operate under severe mechanical and thermal loads causing significant creep, and thus reducing its service life. The present study investigates the steady state creep in a closed end thick-walled composite cylinders made up of aluminum/aluminum alloy matrix (Al/6061Al) and reinforced with silicon carbide particles/whiskers (SiCp,w). The distribution of SiCp,w is assumed to be either uniform or decreasing linearly from the inner to the outer radius of the cylinder. The creep behavior of the cylinder has been described by threshold stress based creep law with a stress exponent of 5. Regression analysis is used to obtain the creep parameters required in the study. The mathematical models have been developed to describe steady state creep in the composite cylinder. The basic equilibrium equation of the cylinder and other constitutive equations have been solved to obtain creep stresses and strain rates in the cylinder. The effect of varying particle size, particle content and temperature on the stresses and strain rates in the composite cylinder has been analyzed. The steady state creep in the FGM cylinder operating under thermal and particle gradients has also been investigated. In many whisker reinforced composites, anisotropy may result due to material flow during processes. Therefore, the effect of anisotropy has also been investigated on creep behavior of FGM cylinder made of 6061Al- SiCw.