VIBRATION ANALYSIS OF FLEXIBLE MEMBRANE STRUCTURE FOR SPACE APPLICATION

Abstract

Membrane structures are used for a lot of applications in the field of architecture and civil engineering, bio-medical sciences, space technology etc. In space, the membrane structures are used for parachutes, inflatable structures such as inflatable antenna, solar panel, sails, telescopes, human habitats in planets, rovers for space exploration etc. Membrane structures has a broad field of the space applications due to its inherent characteristics like ultra-light weight, ability to be stowed in small volume demanding small space requirement, large area coverage per unit weight, high flexibility to change its shape and configuration and easily compliance to curved surfaces. These membrane structures are very thin, can be represented as a plate or shell elements and usually made of polymer films of low modulus. Due to its thinness, these structures do not possess the significant bending and compressive stiffness. The restoring abilities of these structures are only derived from in-plane axial stresses. Due to their extreme flexibility of these membrane structures and also the hazards and unpredictable conditions in space, these structures are subjected to shape distortions and vibration problems. These shape distortions may be due to wrinkling and combinations of tension forces applied to it. The membrane structures are subjected to vibration due to large thermal gradients and micrometeoroids present in space. It is quite costly to test the large membrane structure into vacuum. It necessitates analyzing the vibration behavior using PEA tool. So there arises a need to study the vibration behavior and the shape control of these structures using smart materials such as piezo patches. 1-lence there is a need for membrane structures to adapt themselves as per performance requirement. These structures are, often, called "adaptive membrane structures". This desseratation presents the free vibration analysis of flat membranes of general shapes using ANSYS 14. This modal analysis is based on the assumptions of the membrane theory. The analytical approach is shown to compute the modes of vibration. The behavior of this continuum is also simulated using PEA tool (ANSYS). The results of this simulation are found in good agreement with the analytical ones for the both shapes of flat membrane. The effect of variation in material, prestress and initial conditions such as displacement is shown. A case study is performed by considering multilayer membrane structure. Nonlinear modeling for an adaptive membrane structure is done. MATLAB coding is performed to observe the effect of piezo-actuation, external disturbances, prestress and materials on the deformation of the membrane structure.The above study is helpful in deciding the limiting value of pre-tension required to keep the membrane within specific range of deformation for designing the membrane structure.