The most detailed study of the human skull is currently underway at Argonne National Laboratory in Illinois. The ongoing scientific research, which began in June 2019, may lead to the development of safer ballistic helmets for U.S. armed forces.

In partnership with the Army Research Laboratory (ARL), the helmet safety research project is being led by a research group based at the Advanced Photon Source (APS), a U.S. Department of Energy Office of Science User Facility at Argonne.

"The appearance of U.S. Department of Defense (DoD) visual information does not imply or constitute DoD endorsement.""The appearance of U.S. Department of Defense (DoD) visual information does not imply or constitute DoD endorsement."

High-powered X-rays make new skull insights possible

The sensitive, highly powered beams available at APS are central to better understanding the microstructure of the human skull.

"By putting these [X-ray beams] on the bone, we can then see things about the bone in the skull that we couldn't with other techniques," beamline scientist and group leader Jonathan Almer, Ph.D., said in a National Defense Magazine interview. "That allows us to do things with time and space scales that you couldn't do with laboratory X-rays."

More specifically, APS' X-ray analysis is helping researchers understand the directionality of the skull bones' crystalline collagen structure. With this information, they can better understand what happens to these microscopic components following a blunt force impact. Knowing precisely how the energy disperses and how it modifies the bones themselves can enable helmet designers to develop more effective protections.

Researchers strive for more accurate models of bone behavior

The researchers have been working with cadavers and preserved skull samples that were fractured in previous ARL studies. These samples exhibit the effects of a bullet as well as a helmet on the skull.

"Bullet to helmet to skin to skull to brain," ARL team lead Karin Rafaels explained in an Argonne press announcement. "We have to get the models right all the way through — for our Army mission and for our understanding of bone in general."

The models in question are computer models used to inform helmet design. The bones in the skull are constructed differently from load-bearing bones like the femur, which tend to fracture in predictable ways. And yet, it is these bone behavioral models that helmet design has relied upon. The researchers are eager to develop new, more accurate models representative of the skull itself based on their X-ray imaging experiments.

This level of detail has already proven to be enlightening. "Even in quick reconstructions of the data, we could already see differences between the structures of the femur compared to the skull," Rafaels added.

Implications for military helmet design

According to Rafaels, with the assistance of APS' powerful imaging technology, the researchers "can see if there are preferable loading pathways, or ways to distribute or direct the force of the impact, so that we can design our helmets to take advantage of the skull's crystal structure."

Popular Mechanics compared the skull's collagen structure and likely behavior to that of woodgrain and gemstones: These materials will split easily along the grain but are more resilient when approached across the grain. The helmet of the future may be able to distribute the energy of an impact in a way that takes advantage of these characteristics.

As Almer noted, "By better understanding the mechanics of the skull, we can then design helmets that would generally be better" for use in the U.S. military, which requires hundreds of thousands of helmets to keep its servicemembers safe. The ideal product is a stronger but more lightweight helmet that can be reliably and economically mass-produced.

This study's findings may also be helpful to the sporting world, Almer added, where enhanced sports helmet safety also remains an important yet elusive objective.