Revisiting a senior thesis: smart structures

Imagine having a lazy Sunday and laying out in the sun, but never having to get up and move your shade umbrella to a more optimal place throughout the day. This kind of technology is possible when structures and technology combine to make “smart” structures. Your umbrella could be a structure that senses the location of the sun through the solar panels on its covering, and depending on the amount of sunlight available, create optimal umbrella structure shapes for you.

How can this be done?

“Smart structures” are in fact highly possible. For my senior thesis at Princeton, I studied these adaptive sun shading structures, and my built model was composed of a pre-stretched dielectric elastomer adhered to an inextensible compliant frame. At a small scale, these built flexible models could furl and unfurl predictably. However, these built models were very small and labor intensive. What if there was a way to numerically compute possible “smart” structure shapes to more quickly iterate through different designs? In addition to verifying the built flexible models, I strove to understand if a computational method called dynamic relaxation could be employed for the analysis of dielectric elastomer minimum energy structures (DEMES).

Photos of the DEMES structure studied

So can dynamic relaxation be employed for the analysis of DEMES?

The short answer is yes, it seems like it can.

Dynamic relaxation, a common structural form finding method, was chosen as a numerical simulation technique to simulate the curling action the DEMES. Dynamic Relaxation introduces a fictitious inertia and damping terms into the equations of motion, formulating a static system as the equilibrium state for a group of damped vibrations.

DEMES equilibrium shape obtained with the dynamic relaxation model

Comparing computed shapes to the physically modeled stretched elastomer structures, there was a noted correlation between equilibrium angle and applied voltage for a biaxial stretch when using a modified Dynamic Relaxation algorithm with bending and clustered elements. Overall, while I found that a numerically modified structure is influenced by material uncertainties approximated input values, the Dynamic Relaxation technique was found capable of predicting the shapes and elastic energy of DEMES.

Much experimental work has been conducted on the potential of DEMES, and with the possibility of an easier computational method – Dynamic Relaxation – for numerically simulating its shapes and elastic energies, huge progress has been made for the reality of a “smart” sun shading structure. However, there are still many aspects of DEMES to be explored before its commercial reality, such as the differences in material strength of elastomer films versus sun shading umbrella material, or the effect of repetitive unfurling motion on DEMES material. Using Dynamic Relaxation techniques will allow us to iterate more quickly on different DEMES designs, and allow us to explore the potential of DEMES.

Author: Sabrina Siu

Sabrina Siu graduated Princeton in 2013 with a CEE senior thesis, ‘The Potential of Electroactive Polymers for Shape Shifting Structures,’ jointly advised by Professor Adriaenssens and Professor Sigurd Wagner (ELE). After Princeton, she worked for ExxonMobil Environmental Services Company as a Project Manager for 2 years, spending two years overseeing environmental clean up projects in the Midwest and the Northeast. After two years of Project Managing, Sabrina decided to change the trajectory of her career to refocus on the intersection of research and creativity, leading to her current position as a Digital Product Designer at a Media start up in New York. She is still fascinated in the relationship between the form and efficiency of built urban structures, and it’s her goal to one day contribute toward “smart” built structures.

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