Hard knocks, sweat, and sports drinks threaten bicycle safety. So Ron Kander and Brian Love, researchers in materials science and engineering at Virginia Tech, are working to improve bicycles and accessories in ways that could impact every adult or child itching for a new set of wheels.
Love is trying to solve a common limitation of bike helmets: their tendency to lose their blow-deflecting capacity through normal wear and tear.
A helmet protects against head knocks by redistributing the force of a blow throughout the surface of the helmet, much as a Kevlar® vest protects a soldier by redistributing the energy of a bullet's impact throughout the vest's surface. Trouble is, bike helmets are only guaranteed to absorb the shock of one fall; after that your head is on its own, because the helmet's capacity to dissipate additional blows has been compromised.
You may not get adequate protection for even a single fall if the helmet has suffered prior damage from, say, dropping it or knocking it off a table. Even minor impacts can degrade the helmet's ability to protect a rider when a serious fall comes. "Simply put, the energy you dissipate from dropping a helmet the first time is not going to be available for that second impact," Love explains. "We're looking for a coating to help helmets stand up better. If we can find it, we think we can help reduce injuries."
Love's students tackled the problem as a senior design project, experimenting with various thicknesses of rubber -- some porous, others solid -- attached with various sealants to polystyrene helmet lining, itself either porous or solid. Their biggest challenge came in finding a precise way to measure and compare the energy-absorption capacity of the composite material.
They solved it by hanging two sledgehammers from an overhead pivot so the hammer heads nearly touched, then placing a section of polystyrene between. They raised a hammer to a specified height and let it fall, afterwards measuring the height the opposite hammer raised after being struck. The first blow depleted the helmet section's energy-absorption capability; successive blows made it worse. During successive trials, the team placed various thicknesses of rubber-coated polystyrene between the hammers and measured the degree to which each helped or hindered the polystyrene's energy- absorption capabilities.
Love and his students discovered a coating that improved energy-absorption capacity by 30 percent; with more sophisticated equipment, Love hopes to create an improvement of 60 percent or more.
Bicycles also degrade with wear and tear. Today's bike frames are wrapped in the same composite graphite epoxy fiber developed in the 1970s and '80s to coat Air Force bombers. But Kander is looking for tougher, lighter, stronger materials that can absorb multiple falls without serious degradation.
Recently he experimented with a number of composite frame materials, looking for ways to protect them against two common chemical solvents: human sweat and sports drinks. No bicyclist, child or professional, can avoid drenching a bike with sweat; what's more, the popularity of sports drinks exposes bikes to regular dousings from them as well.
Kander took frame tubes made of a graphite reinforced epoxy composite, attached aluminum lugs, and sealed the bond with conventional adhesives and chemical surface treatments. He submerged some in a salt water solution; others got a sports drink bath. In successive trials he tried alternative surface treatments and adhesives to see if they held up better to the drenchings.
“We found that conventional adhesives and surface treatments work fine,” Kander says. “The problem lies in failing to apply them properly during manufacturing. If bike companies can keep quality control tight, these materials should perform well.”
He is also doing research to develop strong bicycle materials that are also recyclable and/or biodegradable, so as to keep from adding to the clutter of the nation's landfills.
Kander points out that the incremental research he and Love are doing contributes to major materials improvements. Much of early bicycle research, for example, led to developments later applied to automobiles. With renewed interest in bicycle research --a development of the last decade -- the work of Kander and Love could lead to new materials not only for bicycles but for automobiles and other applications that touch the daily lives of American families.
