Lightweight Composite Structures in Transport

Design, Manufacturing, Analysis and Performance

James Njuguna

• Publisher: Woodhead Publishing
• Year: 2016
• Print ISBN: 9781782423256
• eBook ISBN: 9781782423430
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

Lightweight Composite Structures in Transport: Design, Manufacturing, Analysis and Performance provides a detailed review of lightweight composite materials and structures and discusses their use in the transport industry, specifically surface and air transport. The book covers materials selection, the properties and performance of materials, and structures, design solutions, and manufacturing techniques.A broad range of different material classes is reviewed with emphasis on advanced materials. Chapters in the first two parts of the book consider the lightweight philosophy and current developments in manufacturing techniques for lightweight composite structures in the transport industry, with subsequent chapters in parts three to five discussing structural optimization and analysis, properties, and performance of lightweight composite structures, durability, damage tolerance and structural integrity. Final chapters present case studies on lightweight composite design for transport structures.- Comprehensively covers materials selection, design solutions, manufacturing techniques, structural analysis, and performance of lightweight composite structures in the transport industry- Includes commentary from leading industrial and academic experts in the field who present cutting-edge research on advanced lightweight materials for the transport industry- Includes case studies on lightweight composite design for transport structures

Part One

The lightweight philosophy: materials selection, principles and design solutions

Outline

1. An introduction to lightweight composite materials and their use in transport structures

2. Challenges, opportunities, and perspectives on lightweight composite structures: aerospace versus automotive

3. Opportunities in the design stage of composite components to reduce weight during assembly operations

4. The automotive body lightweighting design philosophy

1

An introduction to lightweight composite materials and their use in transport structures

J. Fan SKF Engineering & Research Center, Nieuwegein, Netherlands

J. Njuguna Robert Gordon University, Aberdeen, United Kingdom

Abstract

The use of lightweight materials has become more prevalent as transport vehicle manufacturers strive to reduce vehicle weight to improve performance, to lower fuel and oil consumption, and to reduce emissions. Mass reduction, manufacturing process, and recycling are paramount in the transport sector in achieving CO₂ (and pollutant gasses) emission reduction. This is due to the fact that fuel is burned to produce force. The lighter the mass, the lower the acceleration, thanks to Newton's second law of motion. The weight reduction is an effective way of reducing CO₂ for any source of energy whether oil (petrol, diesel, etc.), electric, biofuels, or fuel cells. The new generation of polymer composite materials is ideal for use in the transport industry. This chapter provides an overall introduction into lightweight composite materials and their use in transport structures, mainly thermoplastic, thermosets, elastomers, and core materials.

Keywords

Composites; Lightweight materials; Polymers; Recycling; Thermoplastic; Thermoset; Transport structures

1.1. Background

The aim of lightweight construction is to preserve or even expand a product's functionality while the overall weight of the product decreases. Existing approaches for reducing mass include the use of less dense materials, eg, metal foams and composite materials, or a decrease in the material volume by reducing wall thicknesses in key structural components. In both cases, less energy is needed for transportation of the ready-made product, so that the ecologically friendly aspect of lightweight construction is supported. For example, reducing a car mass by 100 kg saves about 0.7l fuel each 100 km (directly and indirectly).

Technologies based on fiber-reinforced thermoplastic materials can be integrated into the manufacturing process for lightweight composite structures. The main motivators for the lightweight materials applications are weight savings and possible cost savings. Significant weight reductions with improved performance will mean less fuel consumption and CO₂ emissions. The transport industry is customer sensitive and currently the customers are pushing for cost-effectiveness and more environmental friendly transport systems. By using low cost, ecofriendly, and reliable materials the economic burden would be reduced for both the customer and the automotive industry.

In addition to the reduction of mass, composite materials offer consistent potential advantages in terms of noise and vibration reduction, impact resistance, and energy absorption capability. They also offer advantages in the manufacturing process, such as cost reduction for producing low volume pieces and the possibility of integration, ie, structures which can be made with fewer subcomponents. Composites also possess a unique capability: to be tailored to meet design requirements which are ill-matched for conventional materials, by properly choosing the constituent materials and the orientation of the reinforcement fibers. This is of primary importance for performance optimization, the target objective being a minimization of the mass and/or of stress concentrations, guaranteeing the required performance.

1.1.1. Lightweighting benefits—automotive example

The need for high performance and the capability of designing material characteristics to meet specific requirements has made polymeric materials a first choice for many aerospace applications. Such materials can be tailored to give high strength coupled with relatively low weight and corrosion resistance to most chemicals and offer long-term durability under most environmentally severe conditions. Polymer materials have key advantages over other conventional metallic materials due to their specific strength properties with weight saving of 20–40%, potential for rapid process cycles, ability to meet stringent dimensional stability, lower thermal expansion properties, and excellent fatigue and fracture resistance. On application of polymer composite materials, for instance, 30% weight savings have been achieved on military fighter aircraft.

In the automotive industry, for example, there is a constant need to upgrade cheap, easily available, and easy to process materials such as polypropylenes, polyethylene, polyamides, etc. to engineering polymers. Vehicle appearance will be an added advantage. In this case, material recyclability is improved with a high percentage of return-to-use products. There is also a need for processing optimization for specific structural and semistructural applications. Use of lightweight materials also aligns with most recent energy conservation regulations and policies, eg, the European Commission with the End of Life Vehicles (ELV) European Union directive requiring vehicles to be constructed of 95% recyclable materials, with 85% recoverable through reuse or mechanical recycling and 10% through energy recovery or thermal recycling.

Unfortunately, vehicle weights have increased over the years especially in the automotive industry. For instance, while a Volkswagen Golf MK1 in 1974 weighed just ∼780 kg its relative Volkswagen Golf MK5 (2004) weighed 1300 kg. This trend in increase in vehicle weight can be seen in many car types and models. This is mainly due to added electronics systems, front impact, and general crash requirements among other modern car utilities. It is possible to achieve a 10% further weight savings from a typical compact car (eg, Volkswagen Golf) with total vehicle mass of 1160 kg and whose car body weight (body in white, BIW) is 296 kg. In particular, a 30% mass reduction on its BIW structure is feasible. For a lifetime road performance of 150,000 km, fuel consumption reduction in this lifetime is around ∼398 L (∼998 kg CO₂ savings) or approximately 0.3 L/100 km fuel savings for each car. In the United Kingdom, for instance, with about 2.3 million/year new vehicles cars entering the UK roads, the total CO₂ savings for the 150,000 km amounts to 2.3 million tons or at least 915 million liters fuel savings and the total CO₂ savings is significant.

Further, reduction in the mass of engines is a key factor for improving the fuel efficiency. Currently, most manufacturers in automotive sector, for example, have replaced cast iron (density = 7.8 g/cm³) engine blocks with lightweight and low cost aluminum–silicon (density = 2.79 g/cm³) crankcases. Several Al-based alloys and metal–matrix composites, such as A319Al, A356Al, A390Al, and A360Al, are in use. To continue using Al alloy engine blocks (due to lighter weight) and to improve wear resistance of the engine bore surface several techniques for forming new composite and/or monolithic protective layers on the bore surface must be explored. By obviating the need for liners on automotive engines, the engine dimension can be significantly reduced. It is estimated that a direct weight savings of about 1 kg per engine can be easily achieved. Every kilogram reduction of payload is important for improvement in fuel efficiency. Reduction of about 110 kg in a typical automobile of weight 1100 kg will improve fuel economy by 7%. In the lifetime of a car this reduction of engine weight is significant.

Weight reduction, manufacturing process, and recycling are paramount in the transport sector for CO₂ reduction especially for aircraft, marine vessels, cars, trucks, and vans. The importance of weight reduction is demonstrated by the fact that almost 85% of the total life-cycle energy consumption occurs during functional operations. This is due to the fact that fuel is burned to produce force. The lighter the mass, the better the acceleration, thanks to Newton's second law of motion. The weight reduction is an effective way of reducing CO₂ for any source of energy whether oil (petrol, diesel, etc.), electric, biofuels, or fuel cells.

1.1.2. Historical overview on composites

Composites can be defined as materials that consist...

Table of contents

• Cover image
• Title page
• Table of Contents
• Related titles
• Copyright
• List of contributors
• Woodhead Publishing Series in Composites Science and Engineering
• Preface
• Part One. The lightweight philosophy: materials selection, principles and design solutions
• Part Two. Current developments in manufacturing techniques for lightweight composite structures in the transport industry
• Part Three. Structural optimization and structural analysis: modelling and simulation
• Part Four. Durability, damage tolerance and structural integrity of lightweight composite structures in transport
• Part Five. Case studies on lightweight composite design for transport structures
• Index