Spinning Membrane Structures
Stefan Haegeli Lohaus
Thin membranes provide large area, light structures that can be packaged tightly for launch, for applications that include space-based antennas and solar sails. A key requirement is being able to apply a state of prestress to stabilize the deployed shape of these structures. Frequently, prestressing is done by applying corner forces through a set of deployable booms, but there is an increasing interest in lighter and potentially simpler solutions, through the use of centrifugal force. In this research we work on characterizing the stability and dynamic behavior of large membrane structures spinning in space, through numerical simulations and laboratory experiments.
We have designed and built an experimental setup in which the hub of the membrane has two controlled degrees of freedom: rotation around the vertical axis and vertical translation. We can can spin and shake a thin membrane disk in vacuum while recording its full field of displacements using stereo Digital Image Correlation.
We started by studying the shapes of the membrane when it is spun up under the action of gravity. This is an experimentally necessary step to set up a “flat” spinning membrane and it exhibits some interesting shape instabilities. The membrane hub is rotated around a vertical axis, with a linearly increasing angular velocity, when the required angular velocity is reached, it is kept constant. The dynamic behavior of the membrane is characterized by a succession of shape instabilities, as the membrane surface takes up a wavy shape with an increasing number of rotationally symmetric waves. Eventually, a smooth axisymmetric shape is reached.
Results of nonlinear dynamic implicit integrations performed with the Abaqus/Standard finite element software, to simulate the large deflection and the instabilities of the membrane during spin up can be summarized in a Wave Number/Speed diagram.
We have studied this problem both experimentally and numerically and found quite good agreement between the two approaches. We are currently studying the vibrations of spinning membranes.
- Delapierre, M. and Pellegrino, S. (2016). Membrane spin up in a normal gravity field: experiments and simulations. SciTech 2016, San Diego, AIAA-2016-1216
- Delapierre, M. and Pellegrino, S. (2015). Spin-stabilized membrane antenna structures, 2nd AIAA Spacecraft Structures Conference, 5-8 January 2015, Kissimmee, FL