AsianScientist (Sep. 3, 2021) – On the road to safer cycling, helmets are getting a tough reinforcement, forged with a new thermoplastic material to shield against head injuries. The Singapore-France team published the study in Composites Part B: Engineering.
As more and more cyclists take to the streets, ensuring safety is paramount. Despite wearing protective gear, head injuries have historically accounted for more than 60 percent of all cyclist-related deaths and long-term disabilities.
During a collision, individuals sustain more severe injuries the stronger the impact suffered by the head. In the anatomy of a typical bicycle helmet, an outer shell made of polycarbonate plastic is designed to crack and disperse energy across the material’s surface, while an inner foam absorbs the bulk of the impact to minimize the amount of energy transferred to the head.
However, a whopping 75 percent of the impact energy still reaches the foam in standard helmets, found scientists led by Associate Professor Leong Kah Fai from Nanyang Technological University, Singapore (NTU). To remedy this, they developed a stronger outer shell to absorb more of the energy, reducing the amount of force pounding the foam and even less felt by the head.
Instead of polycarbonate, the team’s new helmet was made using a proprietary thermoplastic resin named Elium®, manufactured by France-based industry partner Arkema, and further bolstered with carbon fibers. These materials not only created a stiffer and less brittle outer shell, but also enabled the helmet to bear the impact for a longer time.
By dissipating energy evenly throughout the helmet, the Elium®-based outer shell endured over 50 percent of the impact. Only 35 percent of the energy was leftover for the foam, showcasing a remarkable improvement over the conventional helmets.
In a battery of safety tests, the new helmet surpassed polycarbonate ones on various international standards, such as reducing the force sustained at high speeds along rounded and curbstone road conditions. According to the researchers, their helmet could potentially slash fatal and critical injury incidence to three percent and 16.7 percent, respectively—about half of the injury rates for the conventional helmets on flat roads.
Moreover, the production process is relatively cost-effective. Since Elium® is liquid at room temperature, developers can easily mold and manufacture the material in these ambient conditions, rather than the high heat required for other thermoplastics.
Eyeing commercialization, the team is now testing the material with another thermoplastic fabric, hoping to create lighter helmets while still providing increased safety to cyclists.
“Helmets have been proven time and time again to play a critical role in reducing the severity of injuries and number of fatalities,” said Leong. “Our prototype helmet has been subjected to a barrage of internationally benchmarked tests and has demonstrated the ability to provide greater protection for cyclists compared to conventional helmets.”
Source: Nanyang Technological University. Photo: Nanyang Technological University.
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