Composites companies are continuing to test their materials for new mass transit applications. In the United Kingdom, ELG Carbon Fibre, which specializes in technologies to recycle and reuse carbon fibers, is leading a consortium of companies in the development of a lightweight composite rail bogie frame for a passenger train car. (A bogie is known as a railroad truck or truck in North America.) Rail bogies support the car’s body, guide the wheelset and maintain its stability. They help increase ride comfort by absorbing vibrations from the track and minimizing the effect of centrifugal forces as the trains round curves.
One objective of the project is to produce a bogie that’s 50 percent lighter than a comparable metal bogie. “If the bogie is lighter, it will do less damage to the tracks, and that will reduce the time and cost of maintenance because the load on the track will be lower,” says Camille Seurat, product development engineer at ELG. Additional objectives are to reduce lateral wheel-rail forces by 40 percent and also provide through-life condition monitoring. The British non-profit Rail Safety and Standards Board (RSSB) is funding the project with the goal of producing a commercially-viable product.
Magma Structures is responsible for the design and build of the bogie and has carried out extensive manufacturing trials, building numerous test panels using press molding, conventional wet lay-up, infusion and autoclave cured prepreg. As the bogie will be a limited production run, the company has selected epoxy prepreg materials cured in the autoclave as the most cost-effective build method.
The full-size bogie prototype will be 8.8 feet long, 6.7 feet wide and 2.8 feet high. It will be manufactured from a combination of recycled carbon fiber (a non-woven mat supplied by ELG) and virgin carbon fiber fabric. Unidirectional fiber will be utilized for the main strength elements, and this will be laid in the molds using robotic technology. The epoxy resin, chosen for its good mechanical properties, will be a newly-formulated, fire-retardant epoxy resin that has been qualified under EN45545-2 for use on the railways.
Unlike a steel bogie, which is made from a transom beam welded to two side beams, the composite bogie will be manufactured as distinct top and bottom sections and then bonded together. In order to replace an existing metal bogie, the composite version will have to incorporate, in the same location, suspension and brake attachment brackets and other fittings.