Foam-like material that uses high energy-absorbing liquid crystal elastomersScientists at Johns Hopkins University have developed a shock-absorbing material for safety helmets and vehicles that protects just as well as a metal, but is lighter, reusable and also increases its protection capability at higher impact speed. The new foam-like material, which uses high energy-absorbing liquid crystal elastomers, a material used in the research of soft actuators and robotics, could find applications in helmets and body armor, as well as automobile and aerospace parts.
The researchers had observed that the standard materials for such protective devices were not able to perform well from high-speed impacts and tend not to be reusable, so they looked to improve their energy absorption while also reducing weight. As described in the journal Advanced Materials [Jeon et al. Adv. Mater. (2022) DOI: 10.1002/adma.202200272], this new material offers extreme energy absorption capability and greater protection from a wide range of impacts. That it is lighter than most materials used in car bumpers and helmet padding means it would reduce fuel consumption and improve the environmental impact of vehicles. In addition, the material can recover after impacts, and can be repeatedly used many times, which is beneficial for applications where multiple impacts are expected.
To enhance the materials’ ability to withstand impact, the team used a foam-like geometry with high energy-absorbing liquid crystal elastomers. On testing its ability to withstand impact, it was found to successfully withstand being hit by objects weighing between four and to 15 pounds at speeds of up to about 22 mph, the maximum achievable with the drop tester machine used. However, the foam-like material should be able to safely absorb even greater impacts, and has the added advantage of making protective gear more comfortable to wear.
As senior author Sung Hoon Kang told Materials Today, “The new foam-like material not only offers enhanced protection from higher-speed impacts, but also because it is lighter than metal, it could reduce fuel consumption and the environmental impact of vehicles”. The material has a range of possible applications where lightweight, high-impact absorption, reusability and comfortableness are key, and it is hoped this research will help in the development of lightweight and extreme energy-absorbing metamaterials.
The study contributes to an understanding of the synergistic energy absorption mechanism through the interplay between material and geometry. Computer simulations based on material property measurement data were used to systematically examine the underlying mechanisms to help provide information on how best to meet the challenges of such energy-absorbing materials. The team are also assessing other possible mechanisms to help further improve the material’s strength and energy absorption capability, and exploring collaboration with a helmet company to design, fabricate and test next-generation helmets for sporting use and the military.
“The new foam-like material not only offers enhanced protection from higher-speed impacts, but also because it is lighter than metal, it could reduce fuel consumption and the environmental impact of vehicles”Sung Hoon Kang