Composites in the Railway Industry

Chapter 3 Composites in Railway Vehicles

Fernando de Moraes, Seok Yong Cho, Victor Chan

Abstract

        In this chapter, the composite materials which can be applied to railway vehicle are discussed. Fibre reinforced polymers (FRP) with carbon and glass fibre are studied.  Also, composite sandwich panel which can be produced by FRP is characterized. With the implement of these composites on railway vehicles, properties and improved characteristics can be achieved. Weight reduction with these composite materials is studied with practical application. For the light weight composite materials, glass fibre reinforced polymer (GFRP) and carbon fibre reinforced polymer (CFRP) are chosen and applied to bogie frame and body structure. Furthermore, the weight reduction of composite sandwich panel with FRP is designed with mathematical model. The safety factors of these composite materials are also discussed with experimental data in terms of crushing stress and dynamic loads. Moreover, low density materials like honeycomb core, which make part of sandwich panels, have low thermal conductivity, as a result of this characteristic, in a fire occasion, the car body has the capacity to support and maintain the structure integrity. Although, these FRPs are expensive, specially CFRP, because of the high performance of them, in terms of repairing and high power efficiency due to weight reduction, life cycle cost is considerably better when compared to railway vehicles without composites. Also, because of reduced weight which means less fuel consumption and consequently CO2 emission decreases. Due to composite material's improved ´properties, the demand is increasing and the cost for these materials are forecast to decrease. Therefore, the future trend for composite application in railway vehicles is noticeable.  

Keywords: composites in railway vehicles, sandwich panels, carbon fibers, glass fibers, fibers reinforcement polymers.

3.1 Introduction

        Railway Industries has been changing the structure of railway vehicles for many decades, in order to decrease the weight, which is directly associated with velocity, fuels consumption and dynamics. However, due to the high cost of some composite materials, the weight of railway vehicles has actually increased considerably due to implementation of alloys steels. Moreover, with the increasing concern in CO2 emission and safety, new regulation has forced these companies increase interest in developments to avoid penalties [6, 12]. This chapter will explain how these companies has been implemented composites in railway vehicles in order to decrease weight and increase properties. It will focus on safety, economic and environmental factors.

3.2 Material Selection for Railway Vehicle

        There are various lightweight materials in use. However the application of them depends on its characteristics, such as malleability and stiffness. Glass Fibres are the most common reinforcement material for polymer matrix composites. Therefore, the glass fibers reinforced polymers are used widely for railway vehicle structure. The foremost advantages of GFRP are the compromise between low cost, high tensile strength and insulating properties.  Disadvantages are its low Young’s modulus, low fatigue resistance and high hardness. They have been a replacement material in traditional materials such as wood, aluminum and steel due to their comparative advantages of having high mechanical strength, light weight and the flexibility to improve designs. [5]

        Another composite material which can be used for railway vehicle is carbon fibre reinforced polymer (CFRP). CFRP is nowadays the most discussed in lightweight material purpose, as its high potential on weight reduction. Carbon Fibers has been used in several industries, such as sports equipment, aerospace, military, wind power plants and many others. The increase purpose of carbon fibers applications, usually is connected with the high stiffness and low density acquired with this composite. CFRP is manufactured in different shapes and sizing depending on the properties that are acquired for this composite in the application. For example, it can offer high performance when is manufactured long and continuous, but it can also be cut in short strand to facilitate the production, however decreasing its properties. Fiber reinforced polymers (FRP) are produced in the form of laminate, then build up of a lamina or plies and implemented together by a matrix material. The plies used in railway application are uni-directional, which means that all fibers are aligned in one specific direction. The stiffness and strength can be increased without altering the weight or shape of the structure when the laminate is in a specific direction, or when the fiber angles between individual plies is varied.

[pic 1]

Table 1. the differences values for Typical Young’s modulus (E), strength (σˆ) and density (ρ) for four composites and two metals [15]

        Moreover, the composite materials described above can be used for composite sandwich panels. Composite sandwich panels are structural materials which are consisted with thin strong face skins and light weight core materials. Fiber reinforced composites are normally used for skins which are thin, stiff and strong. Polymer foam is the most used materials for core but it can be made by aluminum honeycomb, balsa or woven glass fiber. As the face skins are made by high elastic materials, they can withstand bending and in-plane actions while the core sustain the transverse shear loads so the bending stiffness is larger than that of single solid plate of same materials as the face skins with same weight.  Therefore, composite sandwich panels are widely used for railway vehicle which requires high performance application with minimum weight. [2]

3.3 Application and Weight reduction for Each Composite Material

        There are many parts of the train that can be amenable to mass reduction, for example:

1. Bodyshell
2. Windows
3. Bogies
4. Seats
5. Driver Cab interior
6. External doors

Furthermore, there are also other components of the train which cannot be weight reduced such as the Auxiliary power supply, brake system and power (propulsion). For the components that can be weight reduced, GFRP can be utilized and substituted for the traditional steel material. For example, the Bogie of a railway vehicle can be substituted with GFRP to support the weight of the train body, control the wheel sets on straight and curved tracks and additionally, absorb vibration. [7]