International research in the field of composite materials for rail transportation has been nearly half a century. Although China's rail transportation and high-speed rail are developing rapidly, and the application of high-performance composite materials in China is also changing rapidly, carbon fiber composite materials are widely used in China. It is different. In the international mainstream rail transit, a large number of composite materials are reinforced with glass fiber. As mentioned in this article, TPI Composites develops carbon fiber in the composite material used in the body for less than 10%. The rest is glass fiber, so it can balance the cost while ensuring light weight. The large-scale use of carbon fiber inevitably makes it difficult to control costs, so it can be used in some key structural parts such as bogies.
For more than 50 years, Norplex-Micarta, a manufacturer of thermoset composite materials, has been maintaining a stable business in the manufacture of materials for rail transportation applications, including trains, light rail braking systems, and electrical insulation of overhead rails. But today, the company's market is expanding from a relatively narrow market segment to other more applications, such as walls, roofs and floors.
Dustin Davis, director of business development at Norplex-Micarta, believes that in the next few years, the railway and other mass transportation markets will provide more opportunities for its companies and other composite manufacturers and suppliers. There are several reasons for this expected increase, one of which is the European fire protection standard EN 45545-2, which imposes stricter fire, smoke, and anti-virus (FST) requirements for public transportation through the use of phenolic resin systems , Composite material manufacturers can incorporate the necessary fire and smoke resistance into their products.
In addition, operators of buses, subways and trains are beginning to realize the advantages of composite materials in reducing noise, vibration and harshness. Davis said: "If you have heard metal plates rattling on the subway. If the panel is made of composite material, it will attenuate the sound and make the train quieter."
The lighter weight of the composite material also makes it attractive to bus operators interested in reducing fuel use and expanding their use. In a report in September 2018, market research company Lucintel predicted that between 2018 and 2023, the global market for composite materials used in mass transportation and off-road vehicles will grow at a rate of 4.6% per year, and is expected to be expected by 2023 Reached a value of 1 billion US dollars. Opportunities will come from a variety of applications, including exterior, interior, hood and powertrain parts, and electrical components.
The new parts now produced by Norplex-Micarta are currently being tested on the U.S. light rail line. In addition, the company continues to use continuous fiber materials to focus on electrification systems and combine them with faster curing resin systems. Davis explained: "You can reduce costs, increase production, and bring the full functionality of FST phenolic resin to the market." Although composite materials may be more expensive than similar metal parts, Davis said that cost is not the application decision they are studying factor.
Lightweight and flame retardant
The 66 ICE-3 express fleet of European railway operator Duetsche Bahn has been refurbished, which is one of the capabilities of composite materials to meet the specific needs of customers. The installation of air conditioning systems, passenger entertainment systems and new seats adds unnecessary weight to the ICE-3 rail car. In addition, the original plywood floor did not meet the new European fire standards. The company needed a flooring solution to help reduce weight and meet fire standards. Lightweight composite flooring is the answer.
Saertex, a composite fabric manufacturer based in Germany, provides LEO® material systems for its flooring. Saertex Group's global marketing director Daniel Stumpp said that LEO is a layered non-crimped fabric that has higher mechanical properties and greater light weight potential than woven fabrics. The four-component composite system includes special fire retardant coatings, fiberglass reinforced materials, SAERfoam® (the core material with integrated 3D-glass fiber bridge), and LEO vinyl ester resin.
Composite material manufacturer SMT (also located in Germany) used reusable silicon vacuum bags made by the British company Alan Harper to manufacture floors through a vacuum infusion process. "We saved about 50% of the weight from the previous plywood," Stumpp said. "The LEO system is based on a continuous fiber laminate with a non-filled resin system and has excellent mechanical properties… In addition, the composite material does not rot, which is a big advantage, especially in areas where it snows in winter and the floor is very wet ." Floors, carpets on the top and rubber materials all meet the new flame retardant standards.
SMT has produced more than 32,000 square feet of panels. To date, these panels have been installed in about one third of the eight ICE-3 trains. During the refurbishment process, the size of each panel is being optimized to suit a particular car. The OEM of the ICE-3 sedan is so impressed with the new composite floor that it has ordered a composite roof to partially replace the old metal roof structure in rail cars.
go further
Proterra, California is a designer and manufacturer of zero-emission electric buses and has been using composite materials in all of its bodywork since 2009. In 2017, the company's battery-charged Catalyst? E2 bus traveled 1100 miles one way, setting a world record. The bus is characterized by a lightweight body made by composite manufacturer TPI Composites.
Recently, TPI and Proterra have collaborated to produce integrated one-piece composite electric buses. Todd Altman, senior director of strategic marketing at TPI, explained: “In a typical bus or truck, there is a chassis with the body on top of the chassis. With the hard shell design of the bus, we integrate the chassis and the body together, similar to The design of the integrated car.” In terms of meeting performance requirements, a single structure is more effective than two independent structures.
The Proterra single-shell body is specially designed and designed as an electric car from scratch. Altman said this is an important difference because many car manufacturers and electric bus manufacturers have tried limited attempts to adapt their traditional designs for internal combustion engines to electric vehicles. "They use the existing platform and try to install the battery as much as possible. From various perspectives, this does not provide the best solution." Altman said.
For example, many electric bus batteries are installed at the rear or top of the vehicle. But for Proterra, TPI can install the battery under the bus. "If you want to add a lot of weight to the vehicle structure, you want the weight to be as light as possible, regardless of performance or safety," Altman said. He pointed out that many electric buses and car manufacturers are now returning to the drawings to develop more efficient and targeted designs for their vehicles.
TPI has signed a five-year agreement with Proterra to produce up to 3,350 composite bus bodies at TPI's plants in Iowa and Rhode Island.
needs customization
Designing the main body of the Catalyst bus requires TPI and Proterra to constantly balance the advantages and disadvantages of all different materials so that they can achieve cost goals while achieving optimal performance. Altman pointed out that TPI's experience in producing large wind blades about 200 feet long and weighing up to 25,000 pounds makes it relatively easy for them to produce 40-foot bus bodies weighing between 6,000 and 10,000 pounds.
TPI can selectively use carbon fiber to obtain the required structural strength, and retain it to strengthen the area under maximum load. "We use carbon fiber where we can basically buy cars," Altman said. Overall, carbon fiber accounts for less than 10% of body composite reinforcements, and the rest is glass fiber.
TPI chose vinyl ester resin for similar reasons. "When we look at epoxy resins, they are great, but when you cure them, the temperature must be raised, so the mold must be heated. This is an additional cost," he continued.
The company uses Vacuum Assisted Resin Transfer Molding (VARTM) to produce composite sandwich structures to provide the necessary rigidity for the monocoque. During the manufacturing process, some metal fittings (such as threaded fittings and tapping plates) are incorporated into the body. The bus bar is divided into upper and lower parts, and then glued together. Workers must later add some small composite decorative pieces such as fairings, but the number of parts is only a fraction of the metal bus.
After sending the finished body to the Proterra bus production plant, the flow of the production line will be faster because there is less work to be done. "They don't have to perform all welding, grinding and manufacturing processes, and their interface is very simple, they can connect the car body to the transmission system," Altman added. Proterra saves time and reduces overhead, because the monolithic housing requires less manufacturing space.
Altman believes that as cities switch to electric buses to reduce pollution and cut costs, the demand for composite bus bodies will continue to grow. According to Proterra, battery electric vehicles have the lowest operating life cycle cost (12 years) compared to diesel, CNG or diesel hybrid buses. This may be one of the reasons why Proterra said that the sales of battery-powered electric buses now account for 10% of the entire transportation market.
There are still some obstacles to the wide application of composite materials in the body of electric buses. One is the specialization of different bus customer needs. "Each transportation authority likes to obtain bus-seat configurations and hatch opening methods in different ways. For bus manufacturers, this is a huge challenge, and many of the configuration items may flow to us." Altman Say. "Integrated body builders want to have a standard build, but if every customer wants a high degree of customization, it will be difficult to do." TPI continues to work with Proterra to enhance bus design to better manage end customers The flexibility required.
Explore possibilities
Composites companies are continuing to test whether their materials are suitable for new mass transportation applications. In the UK, ELG Carbon Fibre, which specializes in technology for recycling and reusing carbon fiber, has led an enterprise alliance to develop lightweight composite materials for passenger car bogies. The bogie supports the body of the car, guides the wheelset and maintains its stability. They help improve ride comfort by absorbing the vibration of the rails and minimizing the effect of centrifugal force when the train turns.
One goal of the project is to produce 50% lighter bogies than similar metal bogies. Camille Seurat, ELG product development engineer, said: "If the bogie is lighter, it will reduce the damage caused to the track, and because the load on the track will be reduced, it can reduce maintenance time and maintenance costs." The additional goal is to turn the wheel sideways The wheel-rail force is reduced by 40% and provides life-long state monitoring. The British Non-Profit Railway Safety and Standards Board (RSSB) funded the project with the aim of producing commercially viable products.
Extensive manufacturing trials have been conducted, and many test panels have been made using prepregs from compression molds, conventional wet layup, infusion, and autoclaves. Since the production of bogies will be limited, the company chose epoxy prepreg cured in an autoclave as the most cost-effective construction method.
The full-size bogie prototype is 8.8 feet long, 6.7 feet wide, and 2.8 feet high. It is made of a combination of recycled carbon fiber (nonwoven mat provided by ELG) and original carbon fiber fabric. Unidirectional fibers will be used for the main strength elements and will be placed in the mold using robotic technology. Choosing an epoxy resin with good mechanical properties will be a newly formulated flame-retardant epoxy resin that has passed EN45545-2 certification and can be used on railways.
Unlike steel bogies that are welded from steering beams to the two side beams, composite bogies will be manufactured with different tops and bottoms and then joined together. In order to replace existing metal bogies, the composite version will have to combine suspension and brake connection brackets and other accessories at the same location. "At the moment, we choose to keep the steel parts, but for further projects, it may be interesting to replace the steel parts with composite parts so that we can further reduce the final weight," Seurat said.
A consortium member of the sensor and composite materials group at the University of Birmingham is in charge of monitoring sensor development, which will be integrated into the composite bogie during the manufacturing phase. "Most sensors will focus on monitoring strain at discrete points on the bogie, while other sensors will be used for temperature sensing," Seurat said. The sensor will allow real-time monitoring of the composite material structure, so that life load data can be collected. This will provide valuable information about peak loads and long-term fatigue.
Preliminary research indicates that the composite bogie should be able to achieve the required weight reduction of 50%. The project team hopes to prepare a large bogie for testing in mid-2019. If the prototypes perform as expected, they will produce more bogies to test the trams produced by Alstom Rail Transport.
According to Seurat, although there is still much work to be done, preliminary indications are that it is possible to manufacture a commercially viable composite bogie that can compete with metal bogies in terms of cost and strength. She added: "After that I think composite materials can be used in the railway industry with many options and potential applications."