Berlin 2015 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 37: Biomaterials and Biological Materials II
MM 37.1: Talk
Wednesday, March 18, 2015, 11:45–12:00, TC 006
Smart wooden actuators — •Markus Rüggeberg1,2, Mohammad M. Hassani1, Chiara Vailati1,2, Falk Wittel1, Hans J. Herrmann1, and Ingo Burgert1,2 — 1ETH Zürich, Institute for Building Materials, Zürich, Switzerland — 2Empa, Applied Wood Materials, Dübendorf, Switzerland
Wood swells and shrinks when exposed to fluctuating relative humidity. This property is a drawback for the use of wood as construction material. On the other hand the dimensional instability is the basis for creating smart, autonomously controlled actuators. Nature has developed numerous actuators responding to alternating relative humidity. In pine cones, wheat awns and orchid tree seedpods, the dimensional changes are transformed to bending and twisting movements by creating bi-layered structures with specific fibre orientations in the individual layers. Inspired by these plant model systems, we have developed convertible wooden elements. In outdoor applications, these elements respond to the daily alteration of relative humidity. Therefore, the movement of these elements is autonomous and solar driven. We compare experiments with numerical predictions using a rheological model of wood. A history dependent moisture-stress analysis using the developed material model under changing climatic condition is performed, to predict the true stress and deformation state. Possible applications are facades, or carriers of solar panels which autonomously track the sun. Upscaling of the actuators have already been demonstrated and a prototype of a carrier for solar panels has been successfully tested.