Advanced Composite Materials for Automotive Applications

Structural Integrity and Crashworthiness

Ahmed Elmarakbi

• Publisher: Wiley
• Year: 2013
• Print ISBN: 9781118423868
• eBook ISBN: 9781118535264
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Automotive Transportation & Engineering
• Index: Technology & Engineering

The automotive industry faces many challenges, including increased global competition, the need for higher-performance vehicles, a reduction in costs and tighter environmental and safety requirements. The materials used in automotive engineering play key roles in overcoming these issues: ultimately lighter materials mean lighter vehicles and lower emissions. Composites are being used increasingly in the automotive industry due to their strength, quality and light weight.

Advanced Composite Materials for Automotive Applications: Structural Integrity and Crashworthiness provides a comprehensive explanation of how advanced composite materials, including FRPs, reinforced thermoplastics, carbon-based composites and many others, are designed, processed and utilized in vehicles. It includes technical explanations of composite materials in vehicle design and analysis and covers all phases of composite design, modelling, testing and failure analysis. It also sheds light on the performance of existing materials including carbon composites and future developments in automotive material technology which work towards reducing the weight of the vehicle structure.

Key features:

• Chapters written by world-renowned authors and experts in their own fields
• Includes detailed case studies and examples covering all aspects of composite materials and their application in the automotive industries
• Unique topic integration between the impact, crash, failure, damage, analysis and modelling of composites
• Presents the state of the art in composite materials and their application in the automotive industry
• Integrates theory and practice in the fields of composite materials and automotive engineering
• Considers energy efficiency and environmental implications

Advanced Composite Materials for Automotive Applications: Structural Integrity and Crashworthiness is a comprehensive reference for those working with composite materials in both academia and industry, and is also a useful source of information for those considering using composites in automotive applications in the future.

Part One

Fundamental Background

1

Overview of Composite Materials and their Automotive Applications

Ali Hallal1 , Ahmed Elmarakbi2 , Ali Shaito1 and Hicham El-Hage1

1Department of Mechanical Engineering, LIU, Beirut, Lebanon

2Department of Computing, Engineering and Technology, University of Sunderland, Sunderland, SR6 0DD, UK

1.1 Introduction

This chapter presents an overview of recent automotive applications of advanced composites. A summary of available composites that could be used in automotive industries is presented. This work mainly deals with new research and studies done in order to investigate the present and potential use of composites for automotive structural components (e.g. tubes, plates, driveshafts, springs, brake discs, etc.). The important conclusions of these experimental and numerical simulation studies are shown in detail. It is important to note that most studies have an interest in enhancing the mechanical properties of automotive parts as well as providing better ecological and economical solutions. The influence of reinforcement types and architecture on the mechanical behaviour of automotive parts is investigated.

It is remarked that unidirectional composites and composite laminates are the most used composites, with a domination of glass fibres. However, carbon reinforced polymers and carbon ceramic composites along with nanocomposites could be considered as the most advanced composites currently in use for the automotive industry. Moreover, the emergence of natural fibre reinforced polymers, green composites, as a replacement of glass fibre reinforced polymers is discussed.

Recently, the use of composite materials has increased rapidly in automotive domains. As reported, according to [1], it is remarked that the total global consumption of lightweight materials used in transportation equipment will increase at a compound annual growth rate (CAGR) of 9.9% in tonnage terms and 5.7% in value terms between 2006 and 2011 (from 42.8 million tons/US$80.5 billion in 2006 to 68.5 million tons/US$106.4 billion in 2011) [2]. The use of composites consists of chassis parts, bumpers, driveshafts, brake discs, springs, fuel tanks, and so on.

From a historical point of view, it should be noticed that the first car body made from (glass fibre reinforced polymer, GFRP) composites was for the Chevrolet Corvette, which was introduced to the public at Motorama show at New York in 1953 [3]. For these days, the Corvette series still use composite materials in its design. In motor sports, the use of carbon fibre reinforced polymers has been shown in Formula 1, with the McLaren MP4 in 1981. The open wheel car benefits from lighter body, which leads to a well distributed weight in order to achieve more mechanical grip on the track which significantly increases the overall performance of the car. Nowadays, all Formula series cars and other racing touring cars use composites in huge amounts in almost all of their body parts.

Composites have many advantages over traditional materials, such as their relatively high strength and low weight, excellent corrosion resistance, thermal properties and dimensional stability and more resistance to impact, fatigue and other static and dynamic loads that car structures could be subjected. These advantages increase the performance of cars and lead to safer and lower energy consumption. It should be noticed that car performance is affected not only by the engine horsepower, but also by other important parameters such as the weight/horsepower ratio and the good distribution of the weight. Moreover, lighter vehicles lead to a reduction of fuel consumption. It has been estimated that the fuel economy improves by 7% for every 10% of weight reduction from a vehicle's total weight [1,2]. It is reported that using carbon fibre composites instead of traditional materials in body and chassis car parts could save 50% of weight [1,2]. In addition, it means for every kilogram of weight reduced in a vehicle, there is about 20 kg of carbon dioxide reduction [2].

The major problems still facing the large use of composites in automotive domains are: the high cost in comparison with traditional materials (steel, alloy, aluminium), the complex and expensive manufacturing process for a large number of parts, the unknown physical (mechanical, thermal) behaviour of some kind of composites. Thus, many studies and research are conducted to solve these problems in order to extend the use of composites in large mass. Ford, with a collaboration with materials experts through the Hightech NRW research project, leads the search for a solution of a cost efficient manufacturing of carbon fibre composite components [4]. As estimated by Ford, the use of carbon fibre composites in addition to other advanced materials in the manufacturing of many automotive parts will reduce the weight of their cars by 340 kg at the end of the decade [4]. Another example is the consortium, led by Umeco and partnered by Aston Martin Lagonda, Delta Motorsport Ltd, ABB Robotics and Pentangle Engineering Services Ltd, that has been created to look into the potential for using high-performance composites. The project aims to reduce the cost of composite body in white vehicle structures for the mainstream automotive sector [5].

Many types of composites exist, which give the opportunity to select the optimum material design for any structure. However, this leads to many studies that deal with the mechanical behaviour of composites. The most used composites are composite laminates which consist of several plies with unidirectional long fibres. More developed kinds of composites known as textile composites (woven, braided and knitted fabrics) has emerged recently to be adopted in automotive applications. Moreover, nanocomposites have been used in order to enhance the performance of car structures. Hybrid composites also have been adopted especially in designing tubes and beams. Hybrids consist of several layers of composites and other types of materials, such as aluminium. The aluminium layer is reinforced by laminated or unidirectional (UD) composites composites. These kinds of lightweight materials are used to resist impact loading, as will be shown in the section below.

In this chapter, a brief general introduction of composites type is presented in the second section, while the automotive applications of advanced composites are discussed in the third section. In the fourth section, the potential of analytical and numerical analysis is presented.

1.2 Polymer Composite Materials

In general, composite materials are composed from at least two materials, where one is the reinforcing phase and the other is the matrix. Many combinations can be shown, with different kinds of materials and architectures.

There are two classification systems of composite materials. One is based on the matrix material (metal matrix composites, MMC; ceramic matrix composites, CMC; polymer matrix composites, PMC) and the second is based on the material structure: particulate (random orientation of particles; preferred orientation of particles), fibrous (short-fibre reinforced composites; long-fibre reinforced composites) and laminate composites.

The various PMC are classified as thermoplastic and thermosets and can be reinforced with various types of fibres depending upon the applications. The PMC are used in various automotive applications like crashworthiness, body panels, bumpers and so on. The CMC are used in elevated temperatures of various engine components and braking systems. The MMC use magnesium, copper and aluminium as their matrix with fibres to be used in various engine and crash absorbing components. Moreover, MMC with aluminium matrix and ceramic based composites find some automotive applications with supercar brake discs.

The PMC have heavily been used in the automotive industry. Polymers used in automotive applications are divided into thermoplastics and thermosets. Thermoplastics are high molecular weight materials that soften or melt on the application of heat. Thermoset processing requires the non-reversible conversion of a low molecular weight base resin to a polymerised structure. The resultant material cannot be re-melted or re-formed.

In automotive applications, reinforced plastics are the major composite material. For polymer composites, common fillers used include calcium carbonate (CaCO3), talc, wollastonite, glass and carbon fibre. Some of the common processing techniques for polymer composites are: injection moulding, sheet moulding compound (SMC), glass-mat thermoplastic (GMT) compression moulding, resin transfer moulding (RTM) and reaction injection moulding (RIM).

Some of the factors affecting the processing and manufacture of polymer composites are fibre distribution in the matrix, compatibility between the matrix and fibres, fibre orientation and thermal stability of the fibre.

A common processing technique for the production of polymer composites is thermoforming. Thermoforming is commonly used to produce fibre-mat thermoplastic composites. The fibre and the polymer are inserted into a heated mould. The thermoplastic then flows into the fibre component. The hybrid material is then combined into a composite in a cold press. Compression moulding using thermoset polymer matrices is another major processing technique used to manufacture large parts for the automotive industry.

The main categories of polymer composites used in automotive applications are as follows [6]:

• Non-structural composites, composites composed of short glass fibre-reinforced plastics with the reinforcement in the range of 10–50% by weight used in pedal systems, mirror housing and so on.
• Semi-structural composites, composites composed of several layers of the reinforcement, which is in the form of a mat in a matrix. The mat could be a chopped strand mat, a random continuous strand mat, or a unidirectional mat. The matrix could be a thermoplastic or a thermoset. These composites are used in body panels, front end structures, seat backs and so on.
• Structural composites, structural thermoplastic composites (TPC), structural reaction injection moulded core parts, bumper systems and so on.

1.2.1 Non-Structural Composites

The use of composite materials has been limited to automotive structural components, however recently there has been a wide use of composites in non-structural functional components. Schouwenaars et al. [7] studied the fracture during assembly of a radiator head produced from a nylon/33% short glass fibre composite. The study focused on finding the elastic constants and fracture stresses and on resolving some of the manufacturing problems such as distortion a...

Table of contents

• Cover
• Title Page
• Copyright
• About the Editor
• List of Contributors
• Series Preface
• Preface
• Part One: Fundamental Background
• Part Two: Impact and Crash Analysis
• Part Three: Damage and Failure
• Part Four: Case Studies and Designs
• Index