Soft Computing in the Design and Manufacturing of Composite Materials

Applications to Brake Friction and Thermoset Matrix Composites

Dragan Aleksendric, Pierpaolo Carlone

• Publisher: Woodhead Publishing
• Year: 2015
• Print ISBN: 9781782421795
• eBook ISBN: 9781782421801
• Topic: Technologie et ingénierie
• Subtopic: Science des matériaux

Due to problems associated with the design and manufacturing of composite materials, there is a need to introduce computational and intelligent systems engineering methodology in materials engineering. Soft Computing in the Design and Manufacturing of Composite Material offers an intelligent approach to advance material engineering, and significantly improves the process of designing and manufacturing a new material. This title includes chapters covering topics such as soft computing techniques, composite materials engineering, design and manufacturing of composite materials, numerical modeling, prediction, and optimization of the composite materials performance, development of the hybrid models, and control of the composite material performance. - Introduction of soft computing in the composite materials engineering - Includes accurate and detailed analysis of the current state of the art in the field - Development of the intelligent models for design and manufacturing of composite material - Details composite material performance prediction - Optimization of the manufacturing process of composite materials

1

Introduction to composite materials

Abstract

Composite materials engineering needs systematic and interactive approaches, which should allow the achievement of optimum material characteristics. This process requires the application of various methods and technologies aiming at (i) investigation of the physical and mechanical properties of each constituent, as well as of the composite material; (ii) optimization of the properties of the composite according to the specific working conditions; (iii) understanding the effects of manufacturing and composition on the properties of the composite material; and (iv) development of computational methods for characterization, analysis and prediction of the performance of materials under different working conditions. This appears especially important in the case of composite materials characterized by strongly inhomogeneous properties.

Key words

composite materials

classification

properties

1.1 Basics of composite materials

The ‘composite’ concept is not a human invention. Wood is a natural composite material consisting of one species of polymer – cellulose fibres with good strength and stiffness – in a resinous matrix of another polymer, the polysaccharide lignin [1]. The idea of combining different materials in order to take advantage of the peculiar positive properties of each single constituent has ancient historical roots. However, it is only in the last half century that the science and technology of composite materials have developed sufficiently to provide engineers with a novel class of materials and the necessary tools to enable them to use them advantageously [1]. A structural composite is a material system consisting of two or more phases on a macroscopic scale, whose mechanical performance and properties are designed to be superior to those of the constituent materials acting independently [2]. Generally, a composite material is composed of a reinforcement (fibres, particles and/or fillers) embedded in a matrix (a polymer, metal or ceramic). In general, the reinforcement is supposed to be the strongest of all of the components, and therefore, in structural composites, its main role is to enhance the overall mechanical properties of the resulting material.

The matrix is required to fulfil several functions, most of which are vital to the performance of the material. As a first approximation, it can be stated that the matrix holds the reinforcement in place to define the shape of the final product. The roles of the matrix in fibre-reinforced and particulate composites are quite different. The binder for a particulate aggregate simply serves to retain the composite mass in a solid form, but the matrix in a fibre composite performs a variety of other functions, which must be appreciated to understand the true composite action which determines the mechanical behaviour of a reinforced material. These functions should therefore be considered in some detail [1]. The matrix binds the fibres together, holding them aligned in the important stressed directions. Loads applied to the composite are then transferred into the fibres, the principal load-bearing component, through the matrix, enabling the composite to withstand compression, flexural and shear forces as well as tensile loads. The ability of composites reinforced with short fibres to support loads of any kind is dependent on the presence of the matrix as the load transfer medium, and the efficiency of this load transfer is directly related to the quality of the fibre/matrix bond. The matrix must also isolate the fibres from each other so that they can act as separate entities. Many reinforcing fibres are brittle solids with highly variable strengths. When such materials are used in the form of fine fibres, not only are the fibres stronger than the monolithic form of the same solid, but there is also the additional benefit that the fibre aggregate does not fail catastrophically. The matrix should protect the reinforcing filaments from mechanical damage (abrasion) and from environmental attack. Through the quality of its ‘grip’ on the fibres (the interfacial bond strength), the matrix can also be an important means of increasing the toughness of the composite [1].

Composites have unique advantages over monolithic materials, such as high strength, high stiffness, long fatigue life, low density and adaptability to the intended function of the structure. Additional improvements can be realized in terms of corrosion [2]. The simple term ‘composites’ gives little indication of the vast range of individual combinations that are included in this class of materials. Polymers are often two-phase composites, consisting of a matrix of one polymer with distributions of harder or softer particles contained within it; wood is a perfect example of this. Concrete (the direct descendant of straw and mud bricks) is a classic example of a ceramic/ceramic composite, with particles of sand and aggregate of graded sizes in a matrix of hydrated Portland cement. These materials have been well known for many years, and materials scientists have learned to control their properties by controlling their microstructures; that is to say, the quantity, the shape and the distribution of what we might refer to as the ‘reinforcing phase’. The idea of mixing components across materials class boundaries is a natural extension of this idea [1].

Composites are commonly classified at two distinct levels. The first level of classification is usually with respect to the matrix constituent. The major composite classes include organic-matrix composites (OMCs), metal-matrix composites (MMCs) and ceramic-matrix composites (CMCs). The term ‘organic-matrix composite’ is generally assumed to include two classes of composites: polymer-matrix composites (PMCs) and carbon-matrix composites (commonly referred to as carbon–carbon composites) [3]. The second level of classification refers to the form of the reinforcement: particulate reinforcements, whisker reinforcements, continuous-fibre laminated composites and woven composites [3]. Composites are used not only for their structural properties but also for electrical, thermal, tribological and environmental applications. These features rely strongly on the specific constituents combined in the composite, on the extent of their presence in the final material (weight or volume fraction), and on the shape and architecture of the reinforcing phase. Ideally, the properties of engineering materials should be reproducible and accurately known. Since satisfactory exploitation of the composite principle depends on the design flexibility that results from tailoring the properties of a combination of materials to suit a particular requirement, the accurate prediction of those properties is imperative. At the present time, some of the more important engineering properties of composites can be estimated well on the basis of mathematical models, but many cannot [1].

What is more, modern composite materials are usually optimized (with respect to the aforementioned aspects) to achieve a particular balance of properties for a given range of applications [3]. However, as a common practical definition, the term ‘composite materials’ may be restricted to emphasize those materials that contain a continuous matrix constituent that binds together and provides form to an array of a stronger, stiffer reinforcement constituent. When designed properly, the new combined material exhibits better strength than would each individual material. The main advantages of composite materials are their high strength and stiffness, combined with low density, when compared with bulk materials, allowing weight reduction in the finished part [4]. In composites, materials are combined in such a way as to enable us to make better use of their virtues while minimizing to some extent the effects of their deficiencies. This process of optimization can release a designer from the constraints associated with the selection and manufacture of conventional materials. The designer can make use of tougher and lighter materials, with properties that can be tailored to suit particular design requirements [1].

The obtainment of tailored and desired properties cannot preclude specific manufacturing considerations. Indeed, the need to combine different materials appropriately and realize a well-defined product has a remarkable impact on the manufacturing processes that are suitable. Limiting these considerations to the most widely used composite materials, i.e. PMCs, the aforementioned combination can be realized offline or online: in the former case, two different processing steps, given by the combination of the constituents and the shaping and solidification of the product, can be identified, whereas, in the latter case, the two operations are performed more or less simultaneously. As generally happens for all engineering materials, the early choice of the manufacturing process is based on the dominant shape of the product and cost considerations; however, in the case of fibrous composites, the architecture of the reinforcement can also be a key issue to consider. What is more, great attention should be given to the planning of the process, i.e. the definition of suitable process parameters. Indeed, even assuming that constituent materials and their volume fractions are correctly defined, the use of erroneous (or at least non-optimized) process set-ups could drastically increase the content of voids or negatively affect the fibre–matrix interface, inducing a global worsening of performance.

1.2 Conclusions

Further technological development depends strongly on advances in the field of materials. Composite materials represent a new approach in the process of materials development. Combining two or more materials to obtain a new material with enhanced properties offers wide possibilities for improvements. Optimization of a composite material, regarding not only its matrix and reinforcement materials but also the manufacturing process, could provide a new material that meets previously defined requirements for a specific application. Additionally, composites provide intriguing advantages in terms of design flexibility, because many of them can be manufactured into complex shapes. A strong impulse in this direction could be given by the application of appropriate techniques for modelling, prediction and optimization of the properties of composite materials, as well as of the inherent manufacturing processes.

1.3 References

[1] Harris B. Engineering Composite Materials. London: The Institute of Materials; 1999.

[2] Isaac MD, Ori I. Engineering Mechanics of Composite Material. Oxford University Press; 1994.

[3] Miracle DB, Donaldson S, eds. ASM Handbook, Volume 21: Composites. ASM International; 2001.

[4] Campbell FC. Introduction to Composite Materials. ASM International; 2010.

2

Soft computing and composite materials engineering

Abstract

Engineers and researchers have to develop and use sophisticated tools, methods and technologies in order to enable advanced technical systems to provide customer satisfaction and to become successful in the marketplace. Soft computing can be considered as a new tool of systems engineering. The systems approach to problem solving in engineering needs advanced ‘top-downy’ methods, particularly at the design stage. Since a systems approach is needed in the case of composite materials engineering, soft computing techniques could be used in different phases of the engineering of a composite material. It is especially related to functional analysis, design, testing, prediction and optimization. The integrated process of modelling, calculation, prediction and/or optimization of the properties of a composite material against different influencing factors is the most important part of materials engineering. That is why soft computing techniques, integrated with different numerical methods, could support that process.

Key words

soft computing

composite materials

systems engineering

2.1 Introduction

Industry today, especially the automotive industry, demands products characterized by excellent quality with shorter time to market. That is why engineers have to use advanced technologies. In order to enable advanced technical systems to provide customer satisfaction and to become successful in the marketplace, it is necessary to apply updated technologies or technical skills and methods in all phases of concept analysis, design, development, simulation, testing, manufacturing, verification, certification, marketing and service. This is a result of the designer's intention, which asserts that quality should be ‘inbuilt’ in a system, not merely ‘added’ to it. New technologies should enable engineers to fulfil all of the requirements imposed on technical systems by their users and by governmental or supra-governmental authorities. This means that tuning of mutually opposing, and often contradictory, requirements is necessary. That is why advanced techniques of systems approaches are needed. Composite materials engineering also needs a systems approach which can integrate different tools, including soft computing techniques.

It is known that systems engineering is not a single engineering discipline. It comprises the efforts necessary to integrate different product characteristics into the total engineering effort, and it applies updated computer- and model-based engineering tools to assist in the optimization of the product design, reducing development time. There is an emerging awareness among professionals about systems engineering and systems thinking. It also integrates related technical parameters and assures compatibility of all physical, functional and program interfaces in a...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright page
• List of figures
• List of tables
• Preface
• About the authors
• 1: Introduction to composite materials
• 2: Soft computing and composite materials engineering
• 3: Composite materials manufacturing
• 4: Soft computing techniques
• 5: Composite materials – modelling, prediction and optimization
• Index