Tokyo — Carbon fiber that is lighter yet stronger than aluminum, needs improvements in mechanical property and scalability before becoming a replacement metal to aluminum for bicycles, industry sources said Tuesday.
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Japan produces 60,000-80,000 units of bicycles each month, and aluminum consumption from that sector is negligible, at around a few tens of tons to a few hundred tons each month out of total aluminum demand of 200,000 mt/month, according to sources' estimates.
Some sources however, said changes in the bicycle sector will have implications for the larger four-wheeled passenger vehicles.
"Japanese aluminum diecasters are evolving. Bicycle components makers went from commodity-grade alloy to high-strength proprietary alloy and now they are coping with carbon fiber," said one Tokyo-based trader of aluminum-silicon-magnesium alloy products, known as 6000 series. Alloy is shaped into pipes and frames through extrusion processing.
Other aluminum alloys used include ADC12 used for 1 kg-motor box of electric bicycles. This component however, is still made of aluminum, one diecaster said.
The substitution accelerated around five years ago with the advent of a technology to control the fiber strength and shape during the fiber weaving process, said an official from The Japan Bicycle Promotion Institute.
"This technique reduced production cost and along came scalability, and the spread of its application, as carbon fiber composite shapes could be more flexible," an official with The Japan Bicycle Promotion Institute said.
Usage is still slow for bicycles, as carbon fiber is not able to absorb shock as efficiently as metal, the official added. When impacted by collision, the material breaks apart into pieces while aluminum dents.
One aluminum rolling mill official estimated it would take 10 years for carbon fiber collision resistance to improve before being able to be a replacement, while one automotive supplier source said five years.
"Carbon fiber replacement of aluminum pipe in the main structure started around five years ago with Tour de France-type of road race bike models. Lightweight was vital for faster pedaling," he said. Around 10 kg of carbon was used for one bike model, the official estimated.
The use of carbon fiber has been extended to electric mountain bikes too.
"But mountain bikes often trip over. Bicycle makers are still cautious. Carbon fiber components could break rather than dent or bend, and cause safety issues," the institute official warned.
He added carbon fiber components are currently limited to luxury bikes that cost several thousand dollars. "My guess is over 50% of luxury bikes have carbon fiber. Carbon fiber per bike costs more than $1,000," he said.
A 10 kg aluminum alloy costs less than $20/kg.
"Shimano remains a metal processing company," said Shinpei Kasima, the spokesman for the Japanese bicycle manufacturer Shimano.
"We use carbon fiber, but it is very limited," he added.
Long production process is one of the reasons for the carbon material to be costly, and process improvements are needed to achieve scalability, industry sources said.
Toyota Motor uses carbon fiber for the fuel cell stack of hydrogen fuel cell vehicle Mirai.
Toyota sold 1,070 units of Mirai in the first half of 2018, a decline of 8% year on year, and marginal compared with Toyota's monthly total domestic sales of 100,000 vehicles.
Sales of Mirai, as well as production, have been slow to take off as process improvement is still ongoing for carbon fiber, several company sources said.
"Fuel cell stacks use carbon fiber materials that need to be coated and dried. While these parts will remain relatively expensive as it takes considerable energy to manufacture the carbon fiber, the processes can be scaled up. Coating a 1 meter-wide, 1,200 meter-long roll of carbon fiber at 3 meters per minute would allow a daily shift to produce 30,000 fuel cell vehicles' worth of material per year, and coating speeds can be increased as the technology matures," said fuel cell and electric vehicle analyst Matthew Klippenstein from Electron Communications.
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