Pads made of the ‘architected elastomeric material’ from HRL Laboratories in California showed up to 27% more energy absorption efficiency than the current best-performing expanded polystyrene (EPS) foam when sustaining single impacts.
The pads also showed up 48% improved absorption efficiency over state-of-the-art vinyl nitrile foam when hit repeatedly, HRL said. The company claimed the microlattice could replace currently-used foams in applications such as protective packaging, shock isolators for electronics, vehicle interiors and padding in American football, military or bicycle helmets.
The material is manufactured by a process called light casting, which shines a UV light through a patterned template onto a tray of specially formulated liquid resin. The areas of resin exposed to the light cure and quickly grow into solid polymer struts, which then grow together to form the lattice pad. The formulation of the resin can be adjusted to make microlattices that are stiffer, softer or more compliant.
The process could produce pads for a helmet in less than two minutes – quicker than stereolithography 3D printing, said Eric Clough, HRL researcher and lead author of a new paper. “Microlattice is composed of solid polymer struts and air. Unlike foam, it has an ordered architecture that enables improved performance in airflow, energy absorption, stiffness, and strength. Under high impact, microlattice stiffens to absorb energy and significantly reduces acceleration and force transmitted to the wearer.”
The best competing ‘architected’ pads have maximum energy absorption efficiencies up to 44% for a single impact, Clough said. “Our best performing microlattice pads had maximum energy absorption efficiencies of nearly 58%. Also, the competitor lattice-based pads are irreversibly smashed after sustaining a single impact, whereas our elastomeric microlattice pads continue to efficiently absorb the shock of multiple repeated impacts.”
While the material has a rich variety of potential uses, it has so far been licensed by sports technology company VICIS. The company intends to further develop microlattice impact attenuators and commercialise them in new products to minimise sports-related head injuries. The microlattice also offers improved air flow compared to foams, potentially making helmets much cooler to wear.
The research was published in Matter.
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