New 3D-printed materials could soon be used to make stress-bearing objects from aircraft to bridges to electronic devices much stronger and resistant to breakage.
These materials do not follow the rules of the standard theory used by engineers to predict the behavior of objects that must withstand heavy strain. While the standard theory works well for predicting the behavior of substances such as steel, aluminum and concrete, it falls short when it comes to calculating how other more flexible materials will react under pressure.
Engineering physics professor Rod Lakes and graduate student Zachariah Rueger at the University of Wisconsin–Madison have created a new material that behaves in a way that is consistent with the Cosserat theory of elasticity, also known as micropolar elasticity. The Cosserat theory factors in the underlying substructure of a substance when analyzing its performance in a high-stress environment.
Using the Cosserat theory to inform their design, Lakes and Rueger created a polymer lattice that is about 30 times stiffer when bent than would be predicted by the standard theory. The lattice features polymer strips arranged in a repeating crisscross design—a pattern that can increase strength and durability. Similar behaviors are exhibited by bone and some types of foams.
“When you have a material with substructure in it, such as some foams, lattices and fiber-reinforced materials, there’s more freedom in it than classical elasticity theory can handle,” Lakes explained. “So we’re studying the freedom of materials to behave in ways not anticipated by the standard theory.”
Using 3D printing, Lakes and Rueger can manipulate the lattice structure by using precise control, which has allowed them to fine-tune the material to be exceptionally resilient to bending and twisting.
This substance could be used in a wide variety of applications—for example, in an aircraft wing. When a wing cracks, stress is concentrated around the crack, leaving the entire structure weaker because a cracked wing will break more easily than an intact one. A wing made of the polymer lattice would, in theory, be far less likely to crack in the first place, making it safer and more durable.
Materials that exceed the predictions of standard elasticity theory—created with 3D printing technology—have the potential to make many of the products we use stronger, more resistant to damage, and safer when we need them most.
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