STATIC ANALYSIS OF INFLATABLE TORUS USING PIEZOELECTRIC ACTUATORS

Abstract

Inflatable structures have been a subject of renewed interest in recent years for space applications such as communication antennas, solar thermal propulsion, and entry/landing systems. This is because inflatable structures are very lightweight and on-orbit deployable. In addition, they have high strength-to-mass ratio and require minimal stowage volume, which makes them especially suitable for cost-effective large space structures. An inflated toroidal structure (torus) is often used there in order to provide structural support. For these structures to be effective, their shape must be controlled while keeping the weight low. Piezoelectric materials have become strong candidates for actuator and sensor applications in the shape control of such structures due to their lightweight, conformability to the host structure, and distributed nature. In this study, main focus is to understand the static characteristics of an inflatable torus and to control its shape using piezoelectric actuators and sensors. Several papers on static structural analysis of inflated cylinders and toroidal structures have been written, describing different techniques such as linear shell theory, and nonlinear and variational methods, but very little work had been done in static analysis of torus. It is well known from the theory of shells that classical solutions of shells subjected to different types of loads involves tedious calculations and is extremely difficult especially for shells of arbitrary shapes. The finite element method is very much suitable for the analysis of shells of general shape. In these modem days, number of software are available for finite element analysis, ANSYS is one such software. The present work is aimed to analyze static behaviour of inflated torus, and finding the effect of various parameters on maximum deformation and maximum stress. In this work a model of torus is prepared using ANSYS 7. The inflatable torus of interest to this project is made from Kapton, a thin, light polyimide film. In static analysis pressure is applied on torus and the point of maximum & minimum stress are found out. The deformed shape of torus due to application of pressure is plotted. The change in shape of torus is shown. Then a piezopolymer patch is attached on torus and the effects of piezopolymer devices on the shape control of inflatable torus, is studied for various iii patch positions and thicknesses. The objective of this research is to understand how piezoelectric patches alter the shape of thin, lightweight polyimide films and to assess the ability of the patches to act as sensors and actuator. ry