Tech Briefs
New seatbelt fiber increases safety

Three steps to safety: Securus fiber's smart response.

Over the past ten years as airbags have become standard equipment in vehicles, designers have been searching for a seatbelt that would better correspond to the deceleration action of airbags in a vehicle crash.

AlliedSignal Inc. has developed a new automotive seatbelt fiber called Securus that they claim can increase occupant safety and help reduce seatbelt-system costs while enabling car makers to achieve a five star safety performance score. Woven as a seatbelt strap, the fiber is tailored to work in conjunction with an airbag to slow and lessen a passenger's impact with an airbag during collision.

Securus fiber belongs to a new category in synthetic fibers, PELCO • the first patented polyester-caprolactone block co-polymer specifically engineered for safety restraints and other managed-energy applications. Seatbelts made with the patented Securus fiber deliver a three-step restraint reaction during a crash. First, they hold occupants in position at impact. Then, the fibers relax or stretch as needed to limit the force imposed on the occupant, complementing the deflating action of the airbag and allowing the occupants' bodies to decelerate. Finally, their strength comes back into play, helping to prevent impact with the dashboard, steering wheel, or windshield. "We call Securus the "smart response' fiber," says Greg Rogowski, Marketing Manager for Automotive Safety at AlliedSignal Performance Fibers. "Securus fiber responds to the forces of extreme deceleration in a collision by elongating just enough to limit the forces exerted on the upper torso." While current seatbelt systems are designed for the 50th percentile average occupant, a 79-kg (175-lb) male, the company states that another benefit of their new seatbelt fiber's resiliency is that it works for a broad range of body types • children and smaller women as well as larger people.

The company intends to use Securus fiber in seatbelt webbing as a direct replacement for the mechanical force limiter found in the constant force retractors (CFRs) installed in half the new cars in North America and almost 70% of the new cars produced in Europe. While a retractor is the device found in all seatbelt assemblies that holds and stores seatbelt webbing, a CFR has an additional mechanical device designed to distribute the force of a seatbelt according to the load or force being exerted on it. Fred Festa, Vice President and General Manager of AlliedSignal Performance Fibers, explains, "While CFRs provide the same three-step restraint action, they add to the cost of the restraint systems and the weight of the car, and are more complicated to design and manufacture." Securus fiber seatbelts will probably be installed with lower-cost standard retractors, which Festa estimates will reduce the cost of a car's restraint system by 25% per occupant position compared with the use of mechanical CFRs.