Composite Use in Rail Transport Grows

Composite Use in Railways Composite materials can also be referred to as composite materials and are a combination of two or more materials with similar or different properties brought together at the macroscopic level. Composites are used in many sectors including automotive, transportation, aviation, space, etc., and these sectors benefit from the superior properties offered by composites. In particular, composite materials with high strength-to-weight ratios are frequently preferred in the design of complex and lightweight structures. Railways are among the preferred sectors. Composites created with reinforcements of various materials can be given the desired properties, and in this sense, the composite material used varies for each sector. In the railway sector, Fiber Reinforced Polymer (FRP) composites are frequently utilized. The areas where they are used are mostly; bogie frames, floor materials, sleepers, switches, crossings and other internal parts. Composites basically consist of two parts, these are reinforcement and matrix. The matrix phase exhibits an adhesive structure between two or more fibers and also serves as a load transfer medium. The reinforcement phase increases mechanical properties and overall performance. Depending on the matrix material, composites can be classified as metal matrix composites, polymer matrix composites and ceramic matrix composites. In the field of polymer matrix composites, fiber reinforced polymer composites are frequently used due to their superior properties.

Fiber Reinforced Polymer Composites

Fiber reinforced polymer composites consist of a polymer matrix and fiber components as reinforcement. For these composites to have the desired properties, appropriate fiber-matrix selection is required. The most commonly preferred fibers are aramid, glass and carbon. Glass fiber in particular is frequently used in the composites sector, and the reason for this is that it provides cost advantages. In addition, carbon fiber has higher strength and hardness, and thanks to these properties it can be used in high-performance products. Aramid fiber is used in conditions where both lightweight and high strength are required. When polymer is used as the matrix, thermoset and thermoplastic polymers are mostly preferred. Composite materials combined in this way provide various advantages for the railway sector and have a wide range of applications. Glass fiber reinforced polymer composites are frequently used due to their good formability, higher strength compared to concrete and metal materials, and being a lighter material. At the same time, the processing cost of glass fiber reinforced polymers is low and therefore provides economic benefits. The growing demand for corrosion-free materials in industries has also increased the use of glass fiber reinforced polymer composites instead of ferrous and non-ferrous materials.

Use of Composites in Railways

Glass fiber reinforced composites, due to their low weight, can be used in internal and external parts of railway vehicles. In this way, the weight of the vehicle on the rails is reduced and balanced. As a result, since the total weight is balanced, friction and wear on the rails decrease, and this contributes to an extended service life of the rails.

Bogie

Particularly in railway vehicles, the weight of the bogie frame is very important. The use of steel-based materials in bogie frames causes more weight and corrosion due to environmental effects. For this reason, instead of steel-based materials, lightweight and non-corrosive materials are needed for the production of railway bogie frames. In one of the studies conducted in this regard, glass fiber reinforced epoxy composites were developed for railway bogie frames and the performance of these composites was examined. As a result of the analyses performed, the resistance to the resulting stresses was found to be sufficient for bogie frame production. In another study, bogie upper and lower chassis were produced from FRP and the structural integrity of these chassis was evaluated. As a result of the evaluation; these composites were found to exhibit optimum performance and have good structural integrity. At the same time, the produced composites have a weight reduction feature of 30.9% compared to aluminum-based materials. The evaluated test results demonstrated that these materials can meet the basic load-bearing requirements for bogie frame applications in urban railways.

Sleepers

One of the areas where composites stand out is in sleepers used in railways. A sleeper is a rectangular support used to support railway rails. Sleepers are generally placed perpendicular beneath the railway rails. According to research conducted, approximately 3 million sleepers are used worldwide in railways, and mostly wooden materials are used. However, wooden materials can easily undergo mechanical, biological and thermal degradation under environmental impact. When fiber reinforced polymer composites are used, this deterioration is very difficult to experience, and when the performance of composites as sleepers is evaluated, they are found to have high strength and hardness values.

Fuel Efficiency

One of the contributions of composite use to railway vehicles is improving fuel efficiency and reducing carbon emissions. The reason for this is that they have low weight. Railway vehicles using composites are lighter and moreover have higher strength values. Thanks to this, the lightened railway vehicles require less energy and thus can use fuel more efficiently.

Nose Cone Structural Design

One of the studies in the literature involved the structural design of the nose cone of high-speed trains using a glass fiber composite-foam sandwich structure and testing it. The property needed in the shield section of trains is to absorb the maximum amount of energy in the event of a frontal impact. The use of foam-based sandwiches is increasing in the aviation and aerospace industries. Foam-based sandwich structures are expected to provide significant weight reduction while also providing improvement in total energy absorption, and in this sense have the potential to meet the required requirements. Research is being conducted on its use.

Conclusion

Fiber composite has many advantages over steel-based materials such as lightness, lower energy consumption, higher durability and hardness values. The use of glass fiber reinforced composites in the railway sector increases fuel efficiency, reduces total weight and improves the aerodynamic properties of the railway vehicle. Aerodynamic drag can be prevented especially in high-speed trains. Again, the use of wood in sleepers necessitates frequent replacement of this material. If composites are preferred instead of wood, the produced sleepers can be used for longer periods and their performance will increase. Longer use and increased durability will provide lower maintenance costs and extended service life. With technology, developments are taking place in every sector. The railway sector is also experiencing increasingly greater developments. With the increased use of transportation vehicles such as metros and high-speed trains, research is increasing to develop these vehicles technologically. In the busy lives of many communities, the most important issue is being able to travel faster. The railway sector is also working on this matter and is progressively developing high-speed trains. Composite materials, which are known to offer superior properties, especially because they are lightweight, are expected to be useful in faster transportation and to increase energy efficiency. In this sense, it is foreseen that the use of composites in the railway sector will increase over the years. Sources: Role of Polymer Composites in Railway Sector: An Overview - Praveenkumara Jagadeesh, Madhu Puttegowda, Sanjay Mavinkere Rangappa, Suchart Siengchin Material characterization of a composite–foam sandwich for the front structure of a high speed train - G. Belingardi, M.P. Cavatorta, R. Duella Compiled by: Nilsu Kotil