Martin Ageing of Composites

1. Auflage 2008
ISBN: 978-1-84569-493-7
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 544 Seiten

Reihe: Woodhead Publishing Series in Composites Science and Engineering

Ageing of composites is a highly topical subject given the increasing use of composites in structural applications in many industries. Ageing of composites addresses many of the uncertainties about the long-term performance of composites and how they age under conditions encountered in service.The first part of the book reviews processes and modelling of composite ageing including physical and chemical ageing of polymeric composites, ageing of glass-ceramic matrix composites, chemical ageing mechanisms, stress corrosion cracking, thermo-oxidative ageing, spectroscopy of ageing composites, modelling physical and accelerated ageing and ageing of silicon carbide composites. Part two examines ageing of composites in transport applications including aircraft, vehicles and ships. Part three reviews ageing of composites in non-transport applications such as implants in medical devices, oil and gas refining, construction, chemical processing and underwater applications.With its distinguished editor and international team of contributors, Ageing of composites is a valuable reference guide for composite manufacturers and developers. It also serves as a source of information for material scientists, designers and engineers in industries that use composites, including transport, chemical processing and medical engineering. - Addresses many of the uncertainties about the long-term performance of composites and how they age under conditions encountered in service - Reviews processes and modelling of composite ageing including chemical ageing mechanisms and stress corrosion cracking - Discusses ageing of composites in both transport and non-transport applications ranging from aircraft to implants in medical devices

Autoren/Hrsg.

Martin, Rod

Leseproben

Introduction
R. Martin, Materials Engineering Research Laboratory Ltd, UK Composite materials offer many advantages over conventional structural materials. This includes their high strength and stiffness to weight ratios, their resistance to chemical attack and their tailorability. Much of this publication covers composite materials that are fibre reinforced polymers, but also included are the higher end composite materials in which the matrix is metallic or the fibres are those such as silicon carbide. The use of these materials has seen considerable growth in many industry sectors in the latter part of the twentieth century and this growth has continued into the twenty-first century. The interest in composite materials is driven both by performance factors and environmental factors. The material’s higher strength and stiffness has catapulted the use of these materials into the civilian aerospace market. These same properties along with energy absorption have made vast improvements to performances in many sports, including Grand Prix racing, skiing, golf and tennis. Composite materials are perhaps the only material of choice in certain highly corrosive environments such as those experienced in the petrochemical industry. These materials are also now being selected for environmental reasons because their low specific weight leads to fuel savings in the transport industry, allows for the design of large wind-turbine blades and can be used in construction projects for longer product lives. However, despite this growth in the demand for and use of composite materials, their long-term properties when exposed to a combination of in-service loads and environments are still not well characterised. The effect of exposure to heat, moisture, solvents, acids, ozone, hydrocarbons, loads, etc., and more importantly a combination of these parameters, may degrade the material’s stiffness and strength leading to cracks and ultimately the material failing to meet its purpose. The lack of long-term data or of an accelerated ageing methodology that will predict the effect such degradation might have on the residual properties and future life are two of the major issues still hindering the wider use of composites and leads to over design. The generic term ‘ageing’ can range from the more benign physical ageing effects – such as swelling from moisture absorption – that are largely reversible, to the more serious chemical ageing, which is irreversible. Additionally, ageing from mechanical loading, such as creep, needs to be considered in isolation (or in addition) to that associated with the environment. Environmental ageing of composite materials occurs from the surface or edge inwards and requires time to penetrate into the material’s centre. This is analogous to fluid diffusion and can be anisotropic, and the rate can be dependent on temperature and load. This makes predicting ageing around detailed geometries such as stress concentrations, non-trivial. Representing the true service history for long-term structural life prediction is a vital step to validate any short-term, coupon-based methodology. The coupon tests must reflect the effect of ageing on the polymer (i.e. matrix-dominated properties) because the fibres may mask any property loss in the resin. However, fibres can sometimes degrade quicker than the polymer in certain environments and, additionally, the fibre–matrix interface can be attacked. The above description of the complexity of ageing of composite materials was the main reason for the publication of this book. The aim was to gather as much knowledge from a materials perspective and an end-use perspective in one place so that the different aspects of ageing can be understood. While this publication does not claim to be an all-inclusive encyclopaedia on the subject of ageing of composite materials, it brings many aspects of the subject together in one volume with international contributions. The scope of this publication is to cover the aspects of ageing of composite materials from a fundamental level for different materials systems and from an industrial view point covering a wide variety of different industry sectors. Part I of the publication addresses the fundamental aspects. Dr Gates of NASA Langley Research Center addresses polymeric-based composites and brings together the time–temperature dependency of physical, chemical and mechanical ageing. The chapter addresses early viscoelasticity work by Professor Richard Schapery in the 1970s right up to the ageing of composite materials in modern supersonic aircraft concepts. Dr Plucknett focuses on the ageing of ceramic reinforced composites and particularly fibre reinforced glass ceramics. The degradation of these materials needs to be investigated at the micro-mechanics level. The chapter describes how knowledge of interfacial behaviour is essential to understand how this material class performs at the very high temperatures in which they operate. The ageing of glass fibre reinforced concrete is the subject of Chapter 3 headed by Dr Cuypers. This material has an unusual type of ageing in that the fibres are aged by the matrix material itself. This chapter focuses on chemical attack of glass fibres in the absence of mechanical load (stress corrosion cracking is covered in Chapter 4) and discusses the modelling and experimental methods for characterising and predicting fibre degradation. While ‘corrosion’ is a word that should be avoided in discussion of the ageing of composite materials, the term ‘stress corrosion cracking’ is well established. This is the topic of Chapter 4 by Dr Chateauminois who describes this phenomena in glass reinforced polymeric composites in static and cyclic loading conditions, in acidic and alkaline environments. Chapter 5 written by Dr Tsotsis addresses thermo-oxidative ageing of polymeric composites. The general focus of this work is composite materials operating in air, at high temperatures for long periods of time. The ageing characteristics of a range of materials and some of the methods used to characterise this form of ageing are presented. It is important to understand the mechanisms of ageing in polymeric composites and to do this, detailed investigation of the degradation at the polymer level is required. The use of Fourier transform infrared photo-acoustic spectroscopy is the topic of the chapter headed by Dr Jones. The modelling and understanding of physical ageing is the topic of the chapter written by Professor Hu. This work thoroughly explains the phenomenon of physical ageing, particularly creep and relaxation; it starts from the well-regarded work by Struik and supplements the work described in Chapter 1 of this publication. The ageing of silicon carbide (SiC) composites is discussed in Chapter 8 by Professor Skolianos. These materials are used in very high temperature, load-bearing applications in the transport and propulsion industry. This chapter describes the change of properties with time in SiC reinforced composites and also describes other degradation phenomena such as wear and corrosion. Much of this needs to be investigated at the micro-structural level to understand the effects of grain size, porosity and matrix composition. Part I of this publication concludes with a chapter authored by Professor Mensitieri. This is an in-depth review of the many aspects of the modelling and ageing of composite materials. The chapter overlaps, complements and adds to information in other chapters reinforcing this overall topic and the fundamental understanding of the physical, chemical and mechanical ageing of composite materials. The publication then switches to transport applications in Part II. The specific topic of aerospace as a transport mechanism is not covered because it is inherently discussed in several of the above chapters where the fundamental work was done for the aerospace industry. Part II opens with a chapter on composite materials in the rail industry written by Professor Shin. This industry is seeing a growth in the use of composite materials primarily to reduce rolling stock weight. The main environmental ageing parameters are moisture, ultraviolet light and temperature, and this chapter discusses the evaluation of materials at the coupon and structural level in order to understand the effect of environment on the structure. Captain Dragan then describes the issues of ageing of composites in the rotorcraft industry; much of the focus is on the effect of moisture degradation in the blades and the need to address the more mechanical degradation modes of impact and fatigue. Chapter 12, led by Dr Davies, investigates the ageing of composite materials in marine vessels from leisure craft to underwater vessels. Clearly the main environmental degradation is that of sea water and this chapter gives a thorough review on the subject and discusses methods to characterize degradation – such as property changes, osmosis and blistering. The publication then moves to non-transport applications in Part III. The first chapter, authored by Dr Affatato describes the background and use of polyethylene composites in medical devices. Two of the main ageing issues are oxidation and the generation of wear debris that can lead to osteolysis. The chapter describes some of the methods used to characterise these ageing mechanisms in an accelerated fashion. The oil and gas industry is very demanding on materials in terms of the hostile environments worked in and the hostile conditions and fluids that are involved. Dr Frost’s chapter...