Space membrane structures are generally large, lightweight and flexible,
and there is the possibility that the vibration of these structures in space,
caused by the other systems of the spacecraft, can affect their stability
and performance. Therefore, the development and validation of analysis
methods for predicting their vibration behaviour have been at the forefront
of recent research activities. This dissertation attempts to develop
new analysis techniques and experimental investigations for the vibration
of space membrane structures.
First, finite element modelling techniques for predicting natural frequencies
and mode shapes of flat, unwrinkled membranes in vacuum and in air are developed,
and they are validated with closed-form analytical solutions and experimental
results. These modelling techniques are extended to a new type of curved-membrane
reflectors, to investigate their vibration behaviour in vacuum and in air
with different prestress levels, aperture diameters and number of rib dimensions
of the reflector.
Second, finite element analysis techniques for predicting the linear vibration
behaviour of corner-loaded wrinkled membranes in vacuum and in air are investigated,
to choose a suitable analysis technique and to identify the effect of wrinkles
on the vibration of the membrane. The wrinkled membrane analysis technique
is validated by comparing the in-air analysis results with an experiment performed
in air. The analysis results show that the linear vibration behaviour
of wrinkled membranes in vacuum changes drastically when the wrinkle pattern
changes from small amplitude corner wrinkles to large amplitude diagonal wrinkles.
On the other hand, the in-air vibration behaviour does not change noticeably
with the wrinkle pattern.
Finally, the nonlinear vibration behaviour of wrinkled membrnaes is investigated,
by performing experiments on a corner-loaded, square wrinkled membrane, to
identify the mechanism for the recently reported higher damping of wrinkled
membranes. Experimental results show that wrinkled membranes appear
to dissipate energy more quickly by vibrating simultaneously of the primary
resonance and of its corresponding harmonics, the amplitudes and orders of
which increase when the excitation amplitude increases. A simple analytical
model is developed to identify the geometrically nonlinear interaction behind
the nonlinear behaviour observed in the experiment.
[Cambridge University | CUED | Structures Group | Geotechnical Group]