Microlattice material outperforms EPS in helmets
Corporate R&D laboratory HRL Laboratories developed an architected elastomeric microlattice material that has 27% more energy absorption than the current best-performing expanded polystyrene (EPS) foam.
Most helmets combine a hard shell with closed-cell foam padding, commonly EPS. This material has two distinctive downsides. One, because of the closed-cell nature of the material, it traps heat and sweat against the wearer’s head, and two, after shock-absorption, the material is irreversibly smashed and therefore useless after one impact.
The new lattice material is manufactured by a process called light casting. The process casts UV light through a patterned template onto a tray of specially formulated liquid resin. The areas exposed to the light cure and turns into solid polymer struts that grow together to form a lattice pad. The process takes only a few minutes, while methods such as stereolithography 3D printing would take much longer. The liquid can be adjusted for a stiffer or softer result.
The architected lattice has several advantages over traditional materials. According to HRL, the competing architected pads have a maximum energy absorption efficiencies of up to 44% for a single impact. Under high impact, microlattice stiffens to absorb energy and significantly reduces acceleration and force transmitted to the wearer, absorbing 58% of the impact.
Secondly, the open-celled structure of the material allows air to flow freely through the entire pad, meaning it is much cooler (in the literal sense) to wear.
Finally, the elastomeric material continues to absorb the shock of multiple repeated impacts.
A few years ago, HRL developed the lightest material, which also consisted of a microlattice structure. Read more about it here.
Photos: HRL Laboratories