In partnership with General Motors, researchers from Purdue University, West Lafayette, IN, have revealed that honeycomb “cellular” materials support a range of new applications, such as shock-absorbing football helmets and biomedical implants. Without any additional reprocessing, effective mechanical properties of the shape-memory polymer can be modified after fabrication.
“The idea is that you might mass produce the basic material, and it has many potential uses because you can change it later for application A or application B,” said Pablo Zavattieri, an associate professor in Purdue University’s Lyles School of Civil Engineering.
In new findings, the researchers showed that they could create programmable cellular materials by introducing deliberate defects to the unit cells. Heating allows the alteration of the shape-memory polymer's geometric “unit cells.”
Material properties depend on the shape of the unit cells, and the makeup and thickness of the walls separating each cell. The study revealed that compressing the materials by 5 percent results in a 55 percent increase in stiffness — an important characteristic for varying applications.