shape memory materials
For this research project I investigated the realization of a reversible immediate shape deformation by use of smart materials. This deformation is based on a two-dimensional bending deformation from flat into a 90° bending angle. One important aspect is that the deformation should be fixated without continuous energy input. After a material selection of shape morphing smart materials, a Smart Composite of Shape Memory Alloy (SMA) actuators embedded in a Shape Memory Polymer (SMP) matrix met the design conditions. Both materials are thermo-electric activated, whereby electrical heating wires were embedded in the polymer matrix. The SMP is rigid at room temperature and will become rubbery upon thermal activation above a threshold temperature. By applying external forces, the SMP can easily be deformed. Cooling the SMP will fixate the deformation. The SMP will recover to its original configuration after subsequent unconstrained heating. Antagonist shaped SMA actuators are embedded in the SMP matrix in order to realize the reversible shape deformation.
A small scale prototype proved the reversible performance of the Smart Composite. Optimization of the prototype even showed the possibility to create multiple bending performance.
One main consequence of the thermal activation of the individual materials is that simultaneous heating of all individual material lead to uncontrolled deformation. Either the SMA taking care of the deformation should be activated or the SMA that helps the recovery of the composite. Additionally, the SMP should be fully rubbery before the SMA actuators can be activated. Optimization in terms of thermo-electric activation has been executed by numerical simulation method. This model was validated by thermal imaging experiments.
The performance and control of the Smart Composite shows promising application possibilities. The, for smart materials, large application scale did not lead to unsolved problems and is realistic at this stage.
References
Lelieveld, C. M. J. L. (2013). Smart Materials For The Realization Of An Adaptive Building Component. Ph.D. doctoral Thesis, Delft University of Technology.
Lelieveld, C. M. J. L. and Jansen, K. M. B. (2013). Design and Thermal Testing of Smart Composite Structure for Architecture Applications 6th ECCOMAS Conference on Smart Structures and Materials. Carrera, E., Miglioretti, F. and Petrolo, M. Torino, Italy.
Lelieveld, C. M. J. L. and Voorbij, A. I. M. (2008) “Dynamic Material Application for Architectural Purposes.” Advances in Science and Technology 56, 595-600.
