With heat, flat polymer folds into satellite ‘dish’

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Researchers have used the principles of origami to create a parabolic structure from a flat surface using a shape-memory polymer.

As humankind steps into new frontiers in space exploration, satellites and space vehicles will need to pack more cargo for the long haul. However, certain items, like dish antennas for wireless communication, pose a challenge since they cannot be very densely packed for flight because of their signature bowl shape.

The researchers show that, when heated, the shape-memory polymer changes its shape in a systematic way that mimics folds. This reshaping lifts the material into the shape of a dish. Further, they also show that their origami-engineered dish antennas performed as efficiently as conventional smooth dish antennas.

“Initially, we were largely focused on self-folding origami structures: how would you make them, how would you design them into different shapes, what material would you use?” says Darren Hartl, assistant professor in Texas A&M University’s department of aerospace engineering.

“Having answered some of these questions, we turned to some real-world applications of origami engineering, like adaptive antennas, for which there has been very little work done. In this study, we combine folding behavior and antenna performance and address that gap.”

The researchers describe their antenna design in the journal Smart Materials and Structures.

“Conventional origami design entails folding thin sheets of material at sharp creases. Engineering structures, on the other hand, have a thickness, and the choice of material can make it hard to get these sharp creases,” he says. “Consequently, we need to create folds that exhibit smooth bending.”

To facilitate paper-like folding at the creases, the researchers turned to shape-memory composites that change their shape when heated. In addition, these materials are inexpensive, lightweight, flexible, and capable of being stretched multiple times without being damaged.

First, they built a flat 2D surface using strips of shape-memory composites and cardstock. Simply put, pieces of stiff cardstock, which formed flat facets, were held together by the shape-memory composites, similar to how the ribs of an umbrella hold the fabric in place. Further, at the vertices where the composites meet, they cut out tiny holes to serve as corner creases when the assembly folds into a 3D parabola.

The researchers showed that, when heated, the composites changed their shape by bending systematically, eventually lifting the cardstock pieces into a parabolic bowl-like shape. They also tested if their multifaceted parabolic reflector worked as efficiently as a smooth parabolic antenna and found that the two antennas performed comparably.

Hartl says this research is an important step toward using the principles of origami to make highly functional engineering structures that can be stowed compactly and easily deployed when needed.

“In addition to other applications, future advances based on this research will likely result in morphing reflector antennas for military and space telecommunication applications,” he says.

Additional researchers contributed to the work from Texas A&M; Penn State; and the University of California, Irvine. Funding is from the National Science Foundation and the Air Force Office of Scientific Research.

Source: Texas A&M University