Large deployable space structures include requirements for reflecting
surfaces for antennae, reflectors and solar arrays. Their efficiency
depends not only on surface accuracy but also on the vibration characteristics
of these reflecting surfaces. This dissertation presents a study of
the vibration behaviour of various prestressed membrane structures.
A preliminary vibration analysis of arbitrary shape flat membranes is
done using a finite element package, ABAQUS, and compared with analytical
solutions. The preliminary analysis shows good agreement between finite
element and analytical solutions. This gave confidence to use ABAQUS
simulations for vibration analysis of other membrane structures as well.
The natural frequencies and mode shapes of a deployable membrane reflector
currently under development by the European Space Agency are obtained using
ABAQUS for various reflector diameters, hub dimensions, number of ribs and
prestress. The analysis results indicate that the fundamental nature
frequency of the reflector decreases with the increase of diameter of the
reflector and does not change greatly with the increase of hub radius. Furthermore,
the fundamental natural frequency increases with the increase of membrane
prestress. A periodic nature of variation in the results is observed.
An experimental study of the vibration of a flat membrane is done. The
experimental results indicate the effect of the surrounding air on the membrane
vibration. A similar experimental study carried out at various atmospheric
pressures in a vacuum chamber, published in 1983, is used to study the effect
of the surrounding medium on the membrane vibration. A new prediction
method is presented to determine the natural frequencies and mode shapes
of flat membranes of any shape vibrating in a fluid medium at any pressure.
[Cambridge University | CUED | Structures Group | Geotechnical Group]