September 28, 2021 8 min read
Hard Head Veterans is proud to announce our new microlattice helmet pads for tactical and ballistic helmets! These pads leverage advances in 3D printing to absorb and dissipate far more energy from impacts than traditional pads, and the benefits don’t end there.
The crucial specs:
Hard Head Veterans developed these pads in partnership with the 3D printing company Carbon®, using their proprietary Carbon Digital Light Synthesis™ process. Carbon DLS™ is a breakthrough resin-based 3D printing process that uses digital light projection, oxygen-permeable optics, and engineering-grade materials to produce polymeric parts with exceptional mechanical properties.
3D printing has revolutionized manufacturing. With costs falling and precision rising, these new techniques have paved the way for materials that are exceptionally lightweight, excellent at absorbing impacts, and less wasteful to produce.
And as manufacturing techniques have improved, effective and practical helmet padding is now possible. Microlattice pads, which feature carefully designed microscopic structures with unusual properties, have moved from imagination to production in helmet technology. These pads make impacts to the head far less intense—and possible injuries less severe.
The microlattice—an engineering feat on a molecular scale—is at the heart of new high-performance materials
Let's start with the basics: Overwhelmingly, a “microlattice” is largely made of air. In fact, some such materials consist of as little as 0.01% solid material. Each microlattice consists of an interconnected network of microscopic tubes or struts surrounded by empty space.
These materials tend to be very, very light. Their struts may consist of metals, elastic polymers, or other substances. But regardless of the material, because there's simply so little there, overall weights remain low. In fact, a microlattice recently developed by the aerospace firm Boeing now holds the record for the lightest structural material ever made. Hard Head Veterans’ new microlattice pads are made of polymers to get them as light as practically possible.
But microlattices offer far more than low weights. Diverse geometries—often inspired by the structure of naturally-forming crystals—make them ideal for use in:
It's perhaps easiest to think of microlattices as architecture on an incredibly tiny scale. These carefully designed materials gain strength and other characteristics through the principles of physics. Like a bridge, the "beams" of a microlattice are arranged to withstand different types of stress. If that bridge has only one beam, the structure will readily bend (and eventually break) when weight is placed on the center. But when that same structure is reinforced—with trusses designed to spread out the stress—it takes far more effort to deform it.
The materials of the past have similar properties. For example, foams and perforated metals feature organized, cell-like structures that reduce weight while keeping other characteristics (like impact absorption or strength) intact. But the complex and varied three-dimensional shapes found in microlattices take these traits to new levels.
Recent innovations have put advanced helmet padding and other microlattice applications within reach
Today's microlattices are made through additive manufacturing, where materials are added (typically layer by layer) to gradually create a three-dimensional form. These 3D-printed shapes may then be refined by other processes, like sintering (compression through heat).
3D printing machines have beenaround for decades. And some of the engineering principles at play have been understood for far longer. So why are microlattice products like helmet padding now becoming attainable?
In short, the expense has historically been a significant roadblock for manufacturers. Most have relied on cheaper "subtractive" technologies, which carve shapes out of a block (or "blank") of material. There's a great deal of waste, particularly when making lightweight products where most of the blank is carved away. And the process isn't quite precise enough to produce many micro-scale materials.
This milling machine carves shapes from a metal block, exemplifying the limits of subtractive manufacturing technology: waste, microscopic imprecision, and restrictive design possibilities. Image source:Wikimedia (CC BY-SA 4.0)
Manufacturers who embrace “additive” manufacturing have faced challenges, too. Many 3D printers lack sufficient resolution, meaning that they can't make the tiny, precise movements needed to produce microlattices. And even with the right equipment, production can be slow or problematic.
It can take hours to construct an object only a few centimeters high. In addition, unwanted oxygen may prevent the printer's "ink" (often, a liquid resin) from fully drying. And finished parts typically have at least one section that sticks to—and requires careful peeling from—the machine making them.
But new takes on additive manufacturing are solving the problems of 3D printing, making the mass production of microlattice helmet padding and other materials commercially viable.
One such approach has been pioneered by our partners at Carbon®, a California-based company specializing in 3D printing technology. Carbon Digital Light Synthesis™ (Carbon DLS™) combines various technologies—including digital light projection and specialized resins—to make microscale manufacturing more precise, consistent, and cost-effective.
At the heart of Carbon DLS is a process called continuous liquid interface production (CLIP). CLIP reduces the expense of 3D printing significantly, making it possible for more companies to create microlattice-based materials. Here's how it works:
But the magic of CLIP happens before the light hits the resin. Each projected image first passes through a "dead zone"—a resin-oxygen mixture that prevents UV curing. In essence, it serves as a membrane that keeps the printed part from sticking to the machine. While it's not even as wide as a human hair, the dead zone creates just the barrier needed to skip slow, potentially damaging peeling processes, as shown in the video below:
Traditional 3D printing is a slow, stepwise process. Light exposure, adding new resin, and repositioning must each happen separately and be repeated thousands of times for each component produced. But with DLS, these processes happen seamlessly. And by embracing an approach that isn't so start-and-stop, it's possible to precisely build hundreds of millimeters of material each hour rather than only a few.
During a collision, helmets protect users in at least two primary ways:
To accomplish the second objective, most helmets are lined with impact-absorbing pads. And for some time, foam has been the material of choice. Foam has made helmet padding inexpensive and relatively effective. Moreover, the offerings have evolved dramatically over the years: Ingenious combinations of materials (such as those seen in our own military helmet technology) effectively and comfortably resist impacts.
But challenges remain. Many pads are designed too stiffly—a problem that can make impacts that affect the brain far worse. Concussions remain difficult to prevent (and to detect). And on the battlefield, shockwaves from improvised explosive devices can still cause lasting injuries even through state-of-the-art headgear.
In the past few years, however, scientists have developed an alternative made with elastic microlattice materials that work better. And the technology is only getting started: microlattices have the potential to be as much as ten times more effective than foams at absorbing energy.
Hard Head Veterans’ first generation of microlattice pads underwent a series of tests at National technical Systems labs to assess their performance:
These elastic microlattices are a big improvement in ballistic helmet technology, and they also show great promise for headgear used in sports, motorcycling, and other applications.
A report recently produced under a Department of Defense contract recommends exploring microlattice use in advanced combat helmets (ACHs). The researchers’ preliminary tests confirmed that the material outperforms state-of-the-art foams currently found in ACHs, reducing collision forces transmitted to the wearer by as much as 20%—similar to the performance of Hard Head Veterans’ new microlattice pads.
Microlattice head padding offers better results than leading foam alternatives. Image source:US Army
And the benefits aren't limited to impact reduction. Microlattice padding stays durable through multiple impacts and performs better in temperature extremes. Better still, these microlattices provide greater airflow and comfort—a big plus for anyone who has worn a helmet for an extended period.
Pads that are too hot or too hard have been reported as problems with prior ACH designs and may contribute to headgear being worn less often than it should be. But because microlattices consist largely of air, they can be designed with comfort in mind, resulting in head protection that is far easier to wear. Hard Head Veterans’ microlattice pads are light, conform to the wearer’s head, and enable airflow that keeps helmets an average of 14° (F) cooler.
The microlattice pads developed by Hard Head Veterans and Carbon are a tremendous innovation that can reduce head injuries and keep wearers cooler and more comfortable. But the future of this technology is even more exciting.
There are possible design avenues for reducing backface deformation and increasing blunt impact protection even more. And some researchers believe that the "architectural degrees of freedom" offered by microlattice pad technology may one day provide a way to definitively address other issues in brain injury prevention—notably, the tricky problem of concussions.
Hard Head Veterans is already working on more improvements to our first generation of microlattice helmet pads. And we expect to see even better results soon as we further adapt the design and implement material advances with Carbon!
To get the best pads for head protection on the market, shop HHV’s selection of microlattice pads now!Looking to stay up to date on these and other developments in new military helmet technology?Read more from the Hard Head Veterans blog, where we explore the science of brain injury, helmet padding and shell design, and other things related to ballistic and tactical helmets.