Polymers in Aerospace Applications docx

Expert overviews covering the
science and technology of rubber
and plastics
ISSN: 0889-3144
Volume 16, Number 12
Joel R. Fried
Polymers in Aerospace
Applications
Report 192
16
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12
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Item 1
Macromolecules
33, No.6, 21st March 2000, p.2171-83
EFFECT OF THERMAL HISTORY ON THE RHEOLOGICAL
BEHAVIOR OF THERMOPLASTIC POLYURETHANES
Pil Joong Yoon; Chang Dae Han
Akron,University
The effect of thermal history on the rheological behaviour of ester- and ether-
based commercial thermoplastic PUs (Estane 5701, 5707 and 5714 from

B.F.Goodrich) was investigated. It was found that the injection moulding
temp. used for specimen preparation had a marked effect on the variations
of dynamic storage and loss moduli of specimens with time observed
during isothermal annealing. Analysis of FTIR spectra indicated that
variations in hydrogen bonding with time during isothermal annealing very
much resembled variations of dynamic storage modulus with time during
isothermal annealing. Isochronal dynamic temp. sweep experiments indicated
that the thermoplastic PUs exhibited a hysteresis effect in the heating and
cooling processes. It was concluded that the microphase separation transition
or order-disorder transition in thermoplastic PUs could not be determined
from the isochronal dynamic temp. sweep experiment. The plots of log
dynamic storage modulus versus log loss modulus varied with temp. over
the entire range of temps. (110-190C) investigated. 57 refs.
GOODRICH B.F.
USA
Accession no.771897
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Previous Titles Still Available
Volume 1
Report 1 Conductive Polymers, W.J. Feast
Report 2 Medical, Surgical and Pharmaceutical Applications of
Polymers, D.F. Williams
Report 3 Advanced Composites, D.K. Thomas, RAE,
Farnborough.
Report 4 Liquid Crystal Polymers, M.K. Cox, ICI, Wilton.
Report 5 CAD/CAM in the Polymer Industry, N.W. Sandland and
M.J. Sebborn, Cambridge Applied Technology.
Report 8 Engineering Thermoplastics, I.T. Barrie, Consultant.
Report 10 Reinforced Reaction Injection Moulding,

P.D. Armitage, P.D. Coates and A.F. Johnson
Report 11 Communications Applications of Polymers,
R. Spratling, British Telecom.
Report 12 Process Control in the Plastics Industry,
R.F. Evans, Engelmann & Buckham Ancillaries.
Volume 2
Report 13 Injection Moulding of Engineering Thermoplastics,
A.F. Whelan, London School of Polymer Technology.
Report 14 Polymers and Their Uses in the Sports and Leisure
Industries, A.L. Cox and R.P. Brown, Rapra Technology
Ltd.
Report 15 Polyurethane, Materials, Processing and Applications,
G. Woods, Consultant.
Report 16 Polyetheretherketone, D.J. Kemmish, ICI, Wilton.
Report 17 Extrusion, G.M. Gale, Rapra Technology Ltd.
Report 18 Agricultural and Horticultural Applications of
Polymers, J.C. Garnaud, International Committee for
Plastics in Agriculture.
Report 19 Recycling and Disposal of Plastics Packaging,
R.C. Fox, Plas/Tech Ltd.
Report 20 Pultrusion, L. Hollaway, University of Surrey.
Report 21 Materials Handling in the Polymer Industry,
H. Hardy, Chronos Richardson Ltd.
Report 22 Electronics Applications of Polymers, M.T.Goosey,
Plessey Research (Caswell) Ltd.
Report 23 Offshore Applications of Polymers, J.W.Brockbank,
Avon Industrial Polymers Ltd.
Report 24 Recent Developments in Materials for Food Packaging,
R.A. Roberts, Pira Packaging Division.
Volume 3

Report 25 Foams and Blowing Agents, J.M. Methven, Cellcom
Technology Associates.
Report 26 Polymers and Structural Composites in Civil
Engineering, L. Hollaway, University of Surrey.
Report 27 Injection Moulding of Rubber, M.A. Wheelans,
Consultant.
Report 28 Adhesives for Structural and Engineering Applications,
C. O’Reilly, Loctite (Ireland) Ltd.
Report 29 Polymers in Marine Applications, C.F.Britton, Corrosion
Monitoring Consultancy.
Report 30 Non-destructive Testing of Polymers, W.N. Reynolds,
National NDT Centre, Harwell.
Report 31 Silicone Rubbers, B.R. Trego and H.W.Winnan,
Dow Corning Ltd.
Report 32 Fluoroelastomers - Properties and Applications,
D. Cook and M. Lynn, 3M United Kingdom Plc and
3M Belgium SA.
Report 33 Polyamides, R.S. Williams and T. Daniels,
T & N Technology Ltd. and BIP Chemicals Ltd.
Report 34 Extrusion of Rubber, J.G.A. Lovegrove, Nova
Petrochemicals Inc.
Report 35 Polymers in Household Electrical Goods, D.Alvey,
Hotpoint Ltd.
Report 36 Developments in Additives to Meet Health and
Environmental Concerns, M.J. Forrest, Rapra
Technology Ltd.
Volume 4
Report 37 Polymers in Aerospace Applications, W.W. Wright,
University of Surrey.
Report 38 Epoxy Resins, K.A. Hodd

Report 39 Polymers in Chemically Resistant Applications,
D. Cattell, Cattell Consultancy Services.
Report 40 Internal Mixing of Rubber, J.C. Lupton
Report 41 Failure of Plastics, S. Turner, Queen Mary College.
Report 42 Polycarbonates, R. Pakull, U. Grigo, D. Freitag, Bayer AG.
Report 43 Polymeric Materials from Renewable Resources,
J.M. Methven, UMIST.
Report 44 Flammability and Flame Retardants in Plastics,
J. Green, FMC Corp.
Report 45 Composites - Tooling and Component Processing, N.G.
Brain, Tooltex.
Report 46 Quality Today in Polymer Processing, S.H. Coulson,
J.A. Cousans, Exxon Chemical International Marketing.
Report 47 Chemical Analysis of Polymers, G. Lawson, Leicester
Polytechnic.
Report 48 Plastics in Building, C.M.A. Johansson
Volume 5
Report 49 Blends and Alloys of Engineering Thermoplastics, H.T.
van de Grampel, General Electric Plastics BV.
Report 50 Automotive Applications of Polymers II,
A.N.A. Elliott, Consultant.
Report 51 Biomedical Applications of Polymers, C.G. Gebelein,
Youngstown State University / Florida Atlantic University.
Report 52 Polymer Supported Chemical Reactions, P. Hodge,
University of Manchester.
Report 53 Weathering of Polymers, S.M. Halliwell, Building
Research Establishment.
Report 54 Health and Safety in the Rubber Industry, A.R. Nutt,
Arnold Nutt & Co. and J. Wade.
Report 55 Computer Modelling of Polymer Processing,

E. Andreassen, Å. Larsen and E.L. Hinrichsen, Senter for
Industriforskning, Norway.
Report 56 Plastics in High Temperature Applications,
J. Maxwell, Consultant.
Report 57 Joining of Plastics, K.W. Allen, City University.
Report 58 Physical Testing of Rubber, R.P. Brown, Rapra
Technology Ltd.
Report 59 Polyimides - Materials, Processing and Applications,
A.J. Kirby, Du Pont (U.K.) Ltd.
Report 60 Physical Testing of Thermoplastics, S.W. Hawley, Rapra
Technology Ltd.
Volume 6
Report 61 Food Contact Polymeric Materials, J.A. Sidwell,
Rapra Technology Ltd.
Report 62 Coextrusion, D. Djordjevic, Klöckner ER-WE-PA GmbH.
Report 63 Conductive Polymers II, R.H. Friend, University of
Cambridge, Cavendish Laboratory.
Report 64 Designing with Plastics, P.R. Lewis, The Open University.
Report 65 Decorating and Coating of Plastics, P.J. Robinson,
International Automotive Design.
Report 66 Reinforced Thermoplastics - Composition, Processing
and Applications, P.G. Kelleher, New Jersey Polymer
Extension Center at Stevens Institute of Technology.
Report 67 Plastics in Thermal and Acoustic Building Insulation,
V.L. Kefford, MRM Engineering Consultancy.
Report 68 Cure Assessment by Physical and Chemical
Techniques, B.G. Willoughby, Rapra Technology Ltd.
Report 69 Toxicity of Plastics and Rubber in Fire, P.J. Fardell,
Building Research Establishment, Fire Research Station.
Report 70 Acrylonitrile-Butadiene-Styrene Polymers,

M.E. Adams, D.J. Buckley, R.E. Colborn, W.P. England
and D.N. Schissel, General Electric Corporate Research
and Development Center.
Report 71 Rotational Moulding, R.J. Crawford, The Queen’s
University of Belfast.
Report 72 Advances in Injection Moulding, C.A. Maier,
Econology Ltd.
Volume 7
Report 73 Reactive Processing of Polymers, M.W.R. Brown,
P.D. Coates and A.F. Johnson, IRC in Polymer Science
and Technology, University of Bradford.
Report 74 Speciality Rubbers, J.A. Brydson.
Report 75 Plastics and the Environment, I. Boustead, Boustead
Consulting Ltd.
Report 76 Polymeric Precursors for Ceramic Materials,
R.C.P. Cubbon.
Report 77 Advances in Tyre Mechanics, R.A. Ridha, M. Theves,
Goodyear Technical Center.
Report 78 PVC - Compounds, Processing and Applications,
J.Leadbitter, J.A. Day, J.L. Ryan, Hydro Polymers Ltd.
Report 79 Rubber Compounding Ingredients - Need, Theory
and Innovation, Part I: Vulcanising Systems,
Antidegradants and Particulate Fillers for General
Purpose Rubbers, C. Hepburn, University of Ulster.
Report 80 Anti-Corrosion Polymers: PEEK, PEKK and Other
Polyaryls, G. Pritchard, Kingston University.
Report 81 Thermoplastic Elastomers - Properties and
Applications, J.A. Brydson.
Report 82 Advances in Blow Moulding Process Optimization,
Andres Garcia-Rejon,Industrial Materials Institute,

National Research Council Canada.
Report 83 Molecular Weight Characterisation of Synthetic
Polymers, S.R. Holding and E. Meehan, Rapra
Technology Ltd. and Polymer Laboratories Ltd.
Report 84 Rheology and its Role in Plastics Processing,
P. Prentice, The Nottingham Trent University.
Volume 8
Report 85 Ring Opening Polymerisation, N. Spassky, Université
Pierre et Marie Curie.
Report 86 High Performance Engineering Plastics,
D.J. Kemmish, Victrex Ltd.
Report 87 Rubber to Metal Bonding, B.G. Crowther, Rapra
Technology Ltd.
Report 88 Plasticisers - Selection, Applications and Implications,
A.S. Wilson.
Report 89 Polymer Membranes - Materials, Structures and
Separation Performance, T. deV. Naylor, The Smart
Chemical Company.
Report 90 Rubber Mixing, P.R. Wood.
Report 91 Recent Developments in Epoxy Resins, I. Hamerton,
University of Surrey.
Report 92 Continuous Vulcanisation of Elastomer Profi les,
A. Hill, Meteor Gummiwerke.
Report 93 Advances in Thermoforming, J.L. Throne, Sherwood
Technologies Inc.
Report 94 Compressive Behaviour of Composites, C. Soutis,
Imperial College of Science, Technology and Medicine.
Report 95 Thermal Analysis of Polymers, M. P. Sepe, Dickten &
Masch Manufacturing Co.
Report 96 Polymeric Seals and Sealing Technology, J.A. Hickman,

St Clair (Polymers) Ltd.
Volume 9
Report 97 Rubber Compounding Ingredients - Need, Theory
and Innovation, Part II: Processing, Bonding, Fire
Retardants, C. Hepburn, University of Ulster.
Report 98 Advances in Biodegradable Polymers, G.F. Moore &
S.M. Saunders, Rapra Technology Ltd.
Report 99 Recycling of Rubber, H.J. Manuel and W. Dierkes,
Vredestein Rubber Recycling B.V.
Report 100 Photoinitiated Polymerisation - Theory and
Applications, J.P. Fouassier, Ecole Nationale Supérieure
de Chimie, Mulhouse.
Report 101 Solvent-Free Adhesives, T.E. Rolando, H.B. Fuller
Company.
Report 102 Plastics in Pressure Pipes, T. Stafford, Rapra
Technology Ltd.
Report 103 Gas Assisted Moulding, T.C. Pearson, Gas Injection Ltd.
Report 104 Plastics Profi le Extrusion, R.J. Kent, Tangram
Technology Ltd.
Report 105 Rubber Extrusion Theory and Development,
B.G. Crowther.
Report 106 Properties and Applications of Elastomeric
Polysulfi des, T.C.P. Lee, Oxford Brookes University.
Report 107 High Performance Polymer Fibres, P.R. Lewis,
The Open University.
Report 108 Chemical Characterisation of Polyurethanes,
M.J. Forrest, Rapra Technology Ltd.
Volume 10
Report 109 Rubber Injection Moulding - A Practical Guide,
J.A. Lindsay.

Report 110 Long-Term and Accelerated Ageing Tests on Rubbers,
R.P. Brown, M.J. Forrest and G. Soulagnet,
Rapra Technology Ltd.
Report 111 Polymer Product Failure, P.R. Lewis,
The Open University.
Report 112 Polystyrene - Synthesis, Production and Applications,
J.R. Wünsch, BASF AG.
Report 113 Rubber-Modifi ed Thermoplastics, H. Keskkula,
University of Texas at Austin.
Report 114 Developments in Polyacetylene - Nanopolyacetylene,
V.M. Kobryanskii, Russian Academy of Sciences.
Report 115 Metallocene-Catalysed Polymerisation, W. Kaminsky,
University of Hamburg.
Report 116 Compounding in Co-rotating Twin-Screw Extruders, Y.
Wang, Tunghai University.
Report 117 Rapid Prototyping, Tooling and Manufacturing, R.J.M.
Hague and P.E. Reeves, Edward Mackenzie Consulting.
Report 118 Liquid Crystal Polymers - Synthesis, Properties and
Applications, D. Coates, CRL Ltd.
Report 119 Rubbers in Contact with Food, M.J. Forrest and
J.A. Sidwell, Rapra Technology Ltd.
Report 120 Electronics Applications of Polymers II, M.T. Goosey,
Shipley Ronal.
Volume 11
Report 121 Polyamides as Engineering Thermoplastic Materials,
I.B. Page, BIP Ltd.
Report 122 Flexible Packaging - Adhesives, Coatings and
Processes, T.E. Rolando, H.B. Fuller Company.
Report 123 Polymer Blends, L.A. Utracki, National Research Council
Canada.

Report 124 Sorting of Waste Plastics for Recycling, R.D. Pascoe,
University of Exeter.
Report 125 Structural Studies of Polymers by Solution NMR,
H.N. Cheng, Hercules Incorporated.
Report 126 Composites for Automotive Applications, C.D. Rudd,
University of Nottingham.
Report 127 Polymers in Medical Applications, B.J. Lambert and
F W. Tang, Guidant Corp., and W.J. Rogers, Consultant.
Report 128 Solid State NMR of Polymers, P.A. Mirau,
Lucent Technologies.
Report 129 Failure of Polymer Products Due to Photo-oxidation,
D.C. Wright.
Report 130 Failure of Polymer Products Due to Chemical Attack,
D.C. Wright.
Report 131 Failure of Polymer Products Due to Thermo-oxidation,
D.C. Wright.
Report 132 Stabilisers for Polyolefi ns, C. Kröhnke and F. Werner,
Clariant Huningue SA.
Volume 12
Report 133 Advances in Automation for Plastics Injection
Moulding, J. Mallon, Yushin Inc.
Report 134 Infrared and Raman Spectroscopy of Polymers,
J.L. Koenig, Case Western Reserve University.
Report 135 Polymers in Sport and Leisure, R.P. Brown.
Report 136 Radiation Curing, R.S. Davidson, DavRad Services.
Report 137 Silicone Elastomers, P. Jerschow, Wacker-Chemie GmbH.
Report 138 Health and Safety in the Rubber Industry, N. Chaiear,
Khon Kaen University.
Report 139 Rubber Analysis - Polymers, Compounds and
Products, M.J. Forrest, Rapra Technology Ltd.

Report 140 Tyre Compounding for Improved Performance,
M.S. Evans, Kumho European Technical Centre.
Report 141 Particulate Fillers for Polymers, Professor R.N. Rothon,
Rothon Consultants and Manchester Metropolitan
University.
Report 142 Blowing Agents for Polyurethane Foams, S.N. Singh,
Huntsman Polyurethanes.
Report 143 Adhesion and Bonding to Polyolefi ns, D.M. Brewis and
I. Mathieson, Institute of Surface Science & Technology,
Loughborough University.
Report 144 Rubber Curing Systems, R.N. Datta, Flexsys BV.
Volume 13
Report 145 Multi-Material Injection Moulding, V. Goodship and
J.C. Love, The University of Warwick.
Report 146 In-Mould Decoration of Plastics, J.C. Love and
V. Goodship, The University of Warwick.
Report 147 Rubber Product Failure, Roger P. Brown.
Report 148 Plastics Waste – Feedstock Recycling, Chemical
Recycling and Incineration, A. Tukker, TNO.
Report 149 Analysis of Plastics, Martin J. Forrest, Rapra Technology
Ltd.
Report 150 Mould Sticking, Fouling and Cleaning, D.E. Packham,
Materials Research Centre, University of Bath.
Report 151 Rigid Plastics Packaging - Materials, Processes and
Applications, F. Hannay, Nampak Group Research &
Development.
Report 152 Natural and Wood Fibre Reinforcement in Polymers,
A.K. Bledzki, V.E. Sperber and O. Faruk, University of
Kassel.
Report 153 Polymers in Telecommunication Devices, G.H. Cross,

University of Durham.
Report 154 Polymers in Building and Construction, S.M. Halliwell,
BRE.
Report 155 Styrenic Copolymers, Andreas Chrisochoou and
Daniel Dufour, Bayer AG.
Report 156 Life Cycle Assessment and Environmental Impact
of Polymeric Products, T.J. O’Neill, Polymeron
Consultancy Network.
Volume 14
Report 157 Developments in Colorants for Plastics,
Ian N. Christensen.
Report 158 Geosynthetics, David I. Cook.
Report 159 Biopolymers, R.M. Johnson, L.Y. Mwaikambo and
N. Tucker, Warwick Manufacturing Group.
Report 160 Emulsion Polymerisation and Applications of Latex,
Christopher D. Anderson and Eric S. Daniels, Emulsion
Polymers Institute.
Report 161 Emissions from Plastics, C. Henneuse-Boxus and
T. Pacary, Certech.
Report 162 Analysis of Thermoset Materials, Precursors and
Products, Martin J. Forrest, Rapra Technology Ltd.
Report 163 Polymer/Layered Silicate Nanocomposites, Masami
Okamoto, Toyota Technological Institute.
Report 164 Cure Monitoring for Composites and Adhesives, David
R. Mulligan, NPL.
Report 165 Polymer Enhancement of Technical Textiles,
Roy W. Buckley.
Report 166 Developments in Thermoplastic Elastomers,
K.E. Kear
Report 167 Polyolefi n Foams, N.J. Mills, Metallurgy and Materials,

University of Birmingham.
Report 168 Plastic Flame Retardants: Technology and Current
Developments, J. Innes and A. Innes, Flame Retardants
Associates Inc.
Volume 15
Report 169 Engineering and Structural Adhesives, David J. Dunn,
FLD Enterprises Inc.
Report 170 Polymers in Agriculture and Horticulture,
Roger P. Brown.
Report 171 PVC Compounds and Processing, Stuart Patrick.
Report 172 Troubleshooting Injection Moulding, Vanessa Goodship,
Warwick Manufacturing Group.
Report 173 Regulation of Food Packaging in Europe and the USA,
Derek J. Knight and Lesley A. Creighton, Safepharm
Laboratories Ltd.
Report 174 Pharmaceutical Applications of Polymers for Drug
Delivery, David Jones, Queen's University, Belfast.
Report 175 Tyre Recycling, Valerie L. Shulman, European Tyre
Recycling Association (ETRA).
Report 176 Polymer Processing with Supercritical Fluids,
V. Goodship and E.O. Ogur.
Report 177 Bonding Elastomers: A Review of Adhesives &
Processes, G. Polaski, J. Means, B. Stull, P. Warren, K.
Allen, D. Mowrey and B. Carney.
Report 178 Mixing of Vulcanisable Rubbers and Thermoplastic
Elastomers, P.R. Wood.
Report 179 Polymers in Asphalt, H.L. Robinson, Tarmac Ltd, UK.
Report 180 Biocides in Plastics, D. Nichols, Thor Overseas Limited.
Volume 16
Report 181 New EU Regulation of Chemicals: REACH,

D.J. Knight, SafePharm Laboratories Ltd.
Report 182 Food Contact Rubbers 2 - Products, Migration and
Regulation, M.J. Forrest.
Report 183 Adhesion to Fluoropolymers, D.M. Brewis and R.H.
Dahm, IPTME, Loughborough University.
Report 184 Fluoroplastics, J.G. Drobny.
Report 185 Epoxy Composites: Impact Resistance and Flame
Retardancy, Debdatta Ratna.
Report 186 Coatings and Inks for Food Contact Materials,
Martin Forrest, Smithers Rapra.
Report 187 Nucleating Agents, Stuart Fairgrieve, SPF Polymer
Consultants.
Report 188 Silicone Products for Food Contact Applications,
Martin Forrest, Smithers Rapra.
Report 189 Degradation and Stabilisation of Polymers,
Stuart Fairgrieve, SPF Polymer Consultants
Report 190 Electrospinning
Jon Stanger, New Zealand Institute for Plant and
Food Research
Nick Tucker, New Zealand Institute for Plant and
Food Research
Mark Staiger, Univeristy of Canterbury, New Zeland
Report 191 Polyvinylalcohol: Materials, Processing and
Applications
Vannessa Goodship, Warwick Manufacturing Group,
University of Warwick
Daniel Jacobs, Warwick Manufacturing Group, University
of Warwick
ISBN: 978-1-84735-093-0
Polymers in Aerospace

Applications
Joel R. Fried
Polymers in Aerospace Applications
1
Contents
1. Introduction 3
2. Adhesives 3
3. Coatings 3
4. Fibres 3
4.1 Fibre Types 3
4.1.1 Carbon-Based Fibres 3
4.1.2 Inorganic Fibres 4
4.1.3 Polymeric Fibres 5
4.1.4 Hybrid Fibres 6
4.2 Fibre Forms 6
4.3 Interfacial Properties 6
4.3.1 Coupling Agents 6
4.3.2 Surface Treatment 7
5. Composites 7
5.1 Matrix Polymers 7
5.1.1 Thermosetting Matrices 8
5.1.2 TP Matrices 10
5.2 Fabrication Methods 12
5.3 Non-destructive Testing 12
6. Nanocomposites 13
6.1 Nano-Reinforcements 13
6.2 Processing 15
6.3 Properties of Nanocomposites 15
7. Foams 16
References 16

Abbreviations 16
Abstracts 19
Index 131
Polymers in Aerospace Applications
2
The views and opinions expressed by authors in Rapra Review Reports do not necessarily refl ect those
of Smithers Rapra Technology or the editor. The series is published on the basis that no responsibility
or liability of any nature shall attach to Smithers Rapra Technology arising out of or in connection with
any utilisation in any form of any material contained therein.
Author contact details: Joel R. Fried
Department of Chemical and Materials Engineering
University of Cincinnati
2600 Clifton Avenue, Cincinnati, Ohio 45221
USA
Polymers in Aerospace Applications
3
1. Introduction
The last RAPRA Report on Polymers in Aerospace
Applications (W.W. Wright, Report 37) was published in
1990. The present report strives to provide a contemporary
review of this area with an emphasis on the literature
appearing after 1990. It includes coverage of new materials
and technologies (particularly nanocomposites).
The principal use for polymers in aerospace applications
is as a matrix material and/or reinforcing ¿ bre for
composites. Other major applications include use in
adhesives, anti-misting additives, coatings, elastomers,
¿ bres, and foams.
2. Adhesives
Applications for adhesives include metal-to-metal

bonding for aluminium and titanium parts, composite-
to-metal bonding, and the bonding of elastomers to
metal parts. Structural adhesives are manufactured in
¿ lm and paste form (344). These are widely used in the
manufacture, assembly, and repair of interior and exterior
aircraft components. Examples include the reinforcement
of honeycomb structures such as luggage lockers and
À oor panels (190). Another use is the damping of engine
and noise vibration (190). For example, epoxy-based
syntactic paste has been used for engine vibration
damping. A À ame-retardant epoxy paste has been used
for high-strength reinforcement in honeycomb core parts
as well as in fasteners in overhead baggage lockers (190).
Adhesives with working temperatures in the range 315
°C to 400 °C have been reported for advanced thermal
protection systems bondlines. Ultra-high temperature-
resistant epoxy adhesives have been used to join together
polybenzimidazole (PBI) sheets (199) under high-energy
irradiation and low-pressure plasma treatment to provide
service temperatures in the range –260 °C to +370 °C for
potential aerospace and space applications (199).
3. Coatings
Coatings can provide protection against abrasion and
corrosion as well as reduce icing, provide shielding against
electromagnetic interference (EMI) or radio frequency
interference (RFI), and to protect insulation. Modi¿ ed
phosphate pigments contained in an epoxy/polyurethane
carrier have been used for primers for metal and plastic
substrates. These primers are resistant to hydraulic
À uids. Polysul¿ des and silicone resins have been used

for anti-icing applications. Nylon-6,6 reinforced with
nickel-coated carbon ¿ bres (CF) have been used for EMI/
RFI shielding. Thin ¿ lms of poly(vinylidene À uoride),
polyethylene, and polyimides (PI) have been used to cover
layers of insulation in aircraft and space vehicles.
4. Fibres
The most widely used ¿ bres for aerospace are glass,
carbon, aramid, and boron (470). Other ¿ bres used
for high-performance composites include ultra-high
molecular weight polyethylene (UHMWPE) and
poly(p-phenylene-2,6-benzobisoxazole) (PBO) (217).
A comparison of the modulus and strength of glass,
carbon, and aramid ¿ bres is given in Table 1. Principal
differences between ¿ bre groups include modulus as
well as thermal and chemical stability. As shown by
representative values in Table 1, the modulus can vary
by more than one order of magnitude. Most ¿ bres used
in aerospace applications serve as reinforcements in
composite materials; other uses are found for these
fibres in cabin furnishing, parachutes, and other
specialised applications. Properties and applications
of carbon-based, inorganic, and polymeric ¿ bres are
reviewed in depth within the following sub-sections.
Table 1 Mechanical Properties of Typical
Aerospace Fibres (472)
Fibre Modulus (GPa) Strength
(MPa)
E-glass 72.4 3450
S-glass 85.5 4600
Carbon

(PAN-based)
280–450 4140–5170
Aramid 830 4500
PAN: Polyacrylonitrile
4.1 Fibre Types
4.1.1 Carbon-Based Fibres
Carbon ¿ bres
Since the 1960s, CF have been the most widely used
reinforcing ¿ bres in advanced composites. They can be
produced from PAN, Rayon, or pitch (e.g., petroleum
Polymers in Aerospace Applications
4
or coal tar). Early CF were produced from the pyrolysis
of Rayon precursors. PAN precursors are now more
common because they can be produced without the high-
temperature graphitisation step required for Rayon-based
CF. In general, CF is less impact-resistant that aramid or
glass ¿ bre (398). There is a continuing need to produce
lower-cost CF ideally produced at low temperatures
from cheap, abundant precursors such as anthracitic
coal powder. Pitch-based CF have low-to-negative
coef¿ cients of thermal expansion that are attractive for
spacecraft applications (253). CF are stronger than glass
or aramid ¿ bres but are less impact-resistant and contact
with metal can result in galvanic corrosion (253). It is
estimated that 30% of CF consumption in 2009 will be
for the aircraft and aerospace sector, with about 54%
of the remaining production targeted for industrial use
and 15% for sporting goods (245). Global demand for
PAN-based CF is expected to grow at >10% per year

(248). This is attributed to a resurgence of the aerospace
market and speci¿ cally to production demands for new
commercial aircraft such as the Boeing B787 and Airbus
A380, as well as increased demand in other market
sectors including use in the manufacture of windmill
blades. Global production ¿ gures for carbon ¿ bres
between 1999 and 2009 are shown in Figure 1.
Figure 1 Estimated global production of carbon
¿ bre (245)
Another carbon-based ¿ bre with interesting properties,
especially for nanocomposite applications (see Section
6.1) is vapour-grown carbon ¿ bre (VGCF) (310). VGCF
has some similarities to multiwall carbon nanotubes
(MWNT) but has larger outer (50–200 nm) and inner
(30–90 nm) diameters, with lengths in the range 50
ȝm to 100 ȝm and aspect ratios between 100 to 500.
VGCF has a typical tensile strength of 2.92 GPa and a
tensile modulus of 240 GPa, and has very high thermal
conductivity (e.g., 1950 W/(m·K)). VGCF also has lower
cost but defective microstructure can be a concern.
4.1.2 Inorganic Fibres
Inorganic ¿ bres include primarily glass ¿ bres but also
¿ bres fabricated from more specialised material such
as quartz and boron that ¿ nd use in high-performance
composite applications.
Glass Fibre
Compared with CF, glass ¿ bre has higher density but
offers superior impact resistance. Glass ¿ bres come in
several forms, including E-glass, S-glass, C-glass, and
quartz. The commonest is E-glass (i.e., electrical grade),

a calcium aluminoborosilicate glass. E-glass is a better
electrical insulator than other glass ¿ bres and represents
90% of all glass-¿ bre reinforcements (particularly
¿ berglass). About 50% of the composition of E-glass is
silica oxide. The remaining composition includes oxides
of aluminium, boron, calcium, and other compounds,
including limestone, À uorspar, boric acid, and clay (253).
High-strength glass, a magnesium aluminosilicate glass,
is known as S-glass in the USA (R-glass in Europe and
T-glass in Japan). Compared with E-glass ¿ bres, ¿ bres
made from S-glass have higher silica oxide content
and are about 40–70% stronger (253) and 20% stiffer
(398). Applications include aircraft panels, helicopter
rotor blades, and ¿ lament-wound rocket motor cases
(470). Corrosion-resistant glass (C-glass or E-CR glass)
provides greater resistance to acid environments than
does E-glass (253).
Quartz Fibre
Compared with glass ¿ bre, quartz ¿ bre provides superior
performance, including lower density, better mechanical
properties (e.g., about twice the elongation-to-break and
higher strength and stiffness), higher durability, better
electromagnetic properties (favourable for fabrication of
aircraft radomes), and a near zero coef¿ cient of thermal
expansion (CTE) (309, 398). These superior properties
come at a premium in cost. The use temperature of quartz
¿ bre is as high as 1050 °C for continuous exposure and
up to 1250 °C for short exposures (309).
Boron Fibre
Boron ¿ bres were developed in the early 1960s and were

the ¿ rst high-performance reinforcements for advanced
Polymers in Aerospace Applications
5
composites. Boron ¿ bres can be made by the vapour-
deposition of boron vapours on tungsten or carbon
¿ laments. They have very high strength and modulus,
and offer excellent compressive properties and buckling
resistance. Although boron ¿ bres are expensive, their
superior mechanical properties have led to applications as
structural components on some high-performance military
aircraft (470). Examples of aerospace applications include
aircraft empennage skins, space shuttle truss members,
and prefabricated aircraft repair patches (253, 309).
4.1.3 Polymeric Fibres
Most polymeric ¿ bres used for composite applications
are highly aromatic, rigid-chain polymers. These
include aromatic polyamides, known as aramids.
Nomex
TM
and Kevlar
TM
are aramids. These have
high use-temperatures and provide high modulus and
excellent ballistic properties. Specialty polymeric ¿ bres
include PBO and polybenzothiozole. Quite distinct
from these high-performance polymers that have highly
aromatic main chains is UHMWPE. UHMWPE is a
highly crystalline aliphatic polymer that is extruded
as a gel under high pressure at low temperatures to
achieve highly extended single chains offering very

high modulus in the tensile direction.
Aramid Fibre
Aramids include poly(p-phenylene terephthalamide)
(Kevlar
TM
)
H
N
H
N
O
C
O
C
Figure 2 Structure of Kevlar
and poly(m-phenylene isophthalamide) (Nomex
TM
)
N
H
OO
N
H
Figure 3 Structure of Nomex
Nomex is prepared by the condensation polymerisation of
1,3-phenylene diamine and isophthallic acid (254). The most
widely used aramid ¿ bre for high-performance composites
is Kevlar. Kevlar is prepared by the polycondensation
of 1,4-phenylene diamine and terephthalic acid. Aramid
fibres have lower compressive strength than CF or

inorganic ¿ bres. Other disadvantages include high water
absorption and poor matrix adhesion in some cases. The
high tensile strength (Table 1) of aramid ¿ bres offers
important opportunities for composite applications such as
¿ lament-wound rocket motor cases, gas pressure vessels,
and lightly loaded structures on aircraft (470). Aramid
¿ bres provide exceptional impact resistance and tensile
strength (253). Typical high-performance aramid ¿ bres
have moduli of about 138 GPa and tensile strength in the
range of 3,447 MPa. The properties of aramid ¿ bres can
be modi¿ ed by surface oxidation or plasma etching that
can improve off-axis strength of the composite (254).
Bonding of the ¿ bre to the matrix can be improved through
chemical modi¿ cation, plasma treatment, or by the use of
a coupling agent (254).
PBO
PBO ¿ bres (Zylon
®
) [a.1] have higher strength than CF.
PBO also offers excellent heat and À ame resistance (469)
and has about twice the modulus and tensile strength of
that of an aramid ¿ bre. The decomposition temperature
of PBO is about 100 °C higher than Kevlar (253, 309,
398). Comparison of the properties of aramid and PBO
¿ bres is made in Table 2.
O
O
N
N
Figure 4 Structure of PBO

Polybenzothiazole (PBZT)
Another rigid-rod polymer similar in structure to PBO
is PBZT [a.2]. Like PBO, PBZT has high modulus,
high temperature resistance, and excellent resistance
to organic solvents.
N
S
N
S
Figure 5 Structure of PBZT
Polymers in Aerospace Applications
6
UHMWPE
The attractive properties of these lightweight ¿ bres
made from UHMWPE include high impact resistance,
extremely high speci¿ c strength, excellent chemical,
ultraviolet (UV), and moisture resistance, outstanding
impact resistance, abrasion resistance, low dielectric
constant, and anti-ballistic properties (253). Conversely,
UHMWPE ¿ bres have low resistance to elongation
under sustained load and a comparatively low use-
temperature (398) with a melting point of 150 °C.
UHMWPE fibre is produced by gel spinning of
UHMWPE dissolved in a suitable solvent (254).
Fibre drawing increases strength and modulus (254).
Functional groups can be introduced on the surface of
UHMWPE ¿ bres by means of corona discharge and
plasma treatment (254). The aerospace applications
for UHMWPE ¿ bre composites are limited, but their
antiballistic properties are suitable for applications such

as the bulletproof insert in forti¿ ed cockpit doors in
Boeing single-aisle aircraft (253, 398).
Poly(aryl ether ether ketone) (PEEK)
PEEK, is a semicrystalline engineering thermoplastic (TP)
with a heat distortion temperature (HDT) of 148 °C.
O
CO
O
Figure 6 Structure of PEEK
PEEK can be spun into high-modulus yarn for aerospace
applications by drawing at 200 °C (1). These yarns can
be used under long-term exposure to 250 °C and short-
term exposure at 500 °C.
4.1.4 Hybrid Fibres
CF can be woven with aramid and glass ¿ bres to produce
hybrid cloths for composite application. Carbon/aramid
and carbon/glass ¿ bre hybrids have been used in some
aircraft applications such as ribbed aircraft engine thrust
reversers (254, 398).
4.2 Fibre Forms
Fibre reinforcements come in various forms, including
continuous spools of tow (carbon) or roving (glass),
woven fabrics, stitched multaxials, non-woven mats, and
chopped ¿ bre. Tows are bundles of continuous ¿ bres.
The number of individual ¿ bres in a tow is designated by
a number followed by ‘K’, indicating a multiplication by
1000. CF tows consist of thousands of ¿ bre. Typical sizes
of aerospace-grade tows range 1 K to 12 K (253). Tows
may be used directly in ¿ lament winding or pultrusion,
or fabricated in a unidirectional tape.

4.3 Interfacial Properties
Good interfacial strength between the ¿ ller and the
matrix polymer is critical to achieving high modulus
and particularly strength [a.3]. This is often achieved
by using a coupling agent that shares the chemical
characteristics of the ¿ bre and the matrix, as discussed
in Section 4.3.1. For high-temperature aerospace
applications, special ¿ bre treatments may be used in
place of coupling agents that may degrade at elevated
temperatures.
4.3.1 Coupling Agents
In general, the interfacial strength of composites can
be improved by the use of low-molecular-weight
organofunctional silanes or titanates. For example, the
interfacial strength of a glass ¿ bre-reinforced composite
Table 2 Mechanical Properties of PBO and Aramid Fibres (469)
Fibre Denier Tensile Strength
(g/den)
Elongation at Break
(%)
Tensile Modulus
(g/den)
PBO 500 44.1 4.0 1320
PBO high modulus 490 42.1 2.6 1790
Aramid 1450 23.1 3.5 610
Aramid high modulus 1440 21.6 2.4 910
den: Denier, a measure of the ¿ bre weight reported in the number of grams per 9000 m.
Polymers in Aerospace Applications
7
can be improved by the use of silicon-containing

coupling agents: these are the most common. Titanate
coupling agents are also used in some cases. Examples
of commonly used coupling agents are given in
Table 3. The effect of two different silane coupling agents
(Table 3) on the À exural properties of an unsaturated
polyester composite is illustrated in Table 4. Comparison
shows that vinyl silane and particularly methacrylate
silane improve À exural strength under dry exposure and
at 2-hour exposure in boiling water.
4.3.2 Surface Treatment
The interfacial properties of ¿ bres can be improved
without the use of traditional coupling agents. For
example, the interfacial adhesion of UHMWPE ¿ bre can
be improved by plasma treatment in pure oxygen. The
surface life of ¿ bre-reinforced polyimide composites
in a high-temperature oxidative environment can be
extended by coating a polyimide precursor solution
followed by curing at elevated temperature in a nitrogen
environment (468).
5. Composites
Compared with metals, composites offer high strength
and low weight. Other attractive properties for aerospace
applications include good vibrational damping, low
CTE, and good fatigue resistance. Conversely, the
low thermal and thermo-oxidative stability of some
polymeric composites can be a concern for many high-
temperature aerospace applications. Although carbon
fibre-reinforced plastics (CFRP) represent a small
portion of the total composite market (i.e., compared
with glass-reinforced plastics such as ¿ breglass), the

market growth of CFRP is signi¿ cantly greater than
for other composite materials.
5.1 Matrix Polymers
Polymeric matrices for composites include traditional
thermosets (e.g., epoxies) and TP resins (475), including
some PI and aromatic ketone polymers (e.g., PEEK
and poly(aryl ether ketone ketone) PEKK). TP are
semicrystalline or amorphous. Some TP polymers such as
Table 3 Common Coupling Agents [a.3]
Type Representative Structure
Epoxy silane

H
2
C C H CH
2
O C H
2
C H
2
C H
2
CH
2
S i( OC H
3
)
O
Methacrylate
H

2
C
C C O CH
2
CH
2
CH
2
Si(OCH
3
)
3
C H
3
O
Primary amine silane
NH
2
CH
2
C H
2
CH
2
Si(OCH
3
)
3
Vinyl silane
H

2
C

CH
Si (OCH
3
)
3
Titanate
3
H
2
C

C
C O
TiOCH(CH
3
)
2()
C H
3
O
Table 4 Flexural Strength of a Glass-Reinforced Polyester [a.3]
Flexural Strength (GPa)
Coupling Agent Dry Two-Hour Boil
None 0.38 0.23
Vinyl silane 0.46 0.41
Methacrylate silane 0.62 0.59
Polymers in Aerospace Applications

8
PI can be crosslinked though the use of end-functioning
low-molecular weight resin. In general, thermosetting
resins provide greater resistance to aggressive À uids
such as acetone and hydraulic À uids, but lower-impact
properties and the shelf-life of pre-cure resins is limited.
Composites prepared from TP resins can be fabricated by
a wide variety of methods and provide higher toughness
and increased fatigue and wear resistance, but generally
have poor solvent resistance.
The ability to withstand high temperatures can be a
critical consideration in many aerospace applications.
For example, skin temperatures of Mach 1 aircraft
reach 110 °C, but temperatures can reach 300 °C (327)
for Mach 3 military aircraft. Guided weapons, re-entry
vessels, and space shuttle service can require even higher
use-temperature. PI prepared from the condensation
polymerisation of an aromatic tetracarboxylic acid
and an aromatic diamine, were developed in the
1960s to provide such high service temperatures. PBI,
polybenzoxazoles, and polyquinolines provide even
higher temperature stability but at higher costs.
5.1.1 Thermosetting Matrices
The commonest thermosets for advanced composites
include epoxies, phenolics, cyanate esters (CE),
bismaleimides (BMI), and PI. Typical properties of
epoxy, phenolic, BMI, and CE resins are compared in
Table 5. Although most properties are similar among
the four thermosets, the highest temperature stability
(based upon thermogravimetric analysis (TGA) data)

is achieved by the BMI and CE resins. Other polymers
belonging to this category and reviewed in this section
are benzoxazines and phthalonitrile resins.
Benzoxazines are formed from the reaction of phenol
with an aldehyde and aromatic amine (253). Maleimide-
and norbornene-functionalised benzoxazines provide
improved thermal properties, including char yields
of >55% and high glass transition temperature
(T
g
) (250 °C) (277).
Bismalemides
BMI thermosetting resin has similar properties to those
of epoxies but offers better temperature performance,
especially hot/wet service temperatures up to 232 °C (462),
and high performance-to-cost ratio. They have been used
for high-temperature structural applications on military
aircraft (290). Like epoxies, the brittleness of BMI resins
is high, but toughened versions (see Table 5) are available
(470). Toughening methods include copolymerisation with
styrene and hydroxyl methacrylate (254). Crosslinked BMI
thermosets such as 4,4-bismaleimide diphenyl methane/o-
o´-diallyl alcohol of bisphenol A (Matrimid 5292, Ciba
Geigy) provide excellent high-temperature performance
(464). A study of the effect of storage ageing on BMI
prepregs have suggested that ageing for >30 days may
reduce the curing rate (16).
Cyanoacrylate Esters
CE provide excellent strength and toughness, low
moisture absorption, and superior electrical properties

with a hot/wet service temperature around 149 °C (253,
398, 462). CE resins provide low dielectric loss, good
adhesive properties, high glass-transition temperature
(i.e., 220 °C to 290 °C), high solubility in ketones, and
low moisture absorption (198). CE are more easily
processed than BMI. Brittleness of cured CE resin
can be a concern, and CE is often toughened (198)
by including TP polymers or rubber. Applications for
CE include ablatives and radomes due to excellent
Table 5 Properties of High-Performance Thermosets (462)
Property Epoxy Phenolic Toughened BMI Cyanate Ester
Density (kg/m
3
×10
-3
) 1.2-1.25 1.24 1.2-1.3 1.1-1.35
Use temperature (°C) RT to 180 200–250 ~200 ~200
Tensile modulus (MPa) ×10
-3
3.1-3.8 3-5 3.4-4.1 3.1-3.4
Dielectric constant (1 MHz) 3.8-4.5 4.3-5.4 3.4-3.7 2.7-3.2
Cure temperature (°C) RT to 180 150-190 220-300 180-250
Mould Shrinkage (mm/mm) 0.0006 0.002 0.007 0.004
TGA onset (°C) 260-340 300-360 360-400 400-420
RT: Room temperature
Polymers in Aerospace Applications
9
dielectric properties of CE. CE also can be blended with
epoxies and BMI (462). Epoxy-modi¿ ed bisphenol-A
dicyanate resin reinforced with high-modulus CF for

potential applications in a space environment has shown
good resistance to thermal cycling, UV-irradiation, and
exposure to boiling water (198). CE can be used for
the formation of interpenetrating networks by blending
with TP and thermosets (462). CE composites are
used in primary and secondary structures in military
aircraft as well as in satellite applications (462). These
can be processed by conventional methods including
pre-preging, resin transfer moulding (RTM), ¿ lament
winding, and sheet moulding techniques (462).
Epoxy
Epoxy resins are the most commonly used matrix material
for composites, but their use in high-performance
applications is limited by low service temperature that
is adversely affected by moisture content, loading, and
by the use of toughening agents. For example, an upper
temperature limit of about 177 °C for dry structural use
and only 149 °C for wet exposure has been suggested
(198). Heavy loading of epoxy composites can lower
use temperature to 120 °C. In general, the upper use
temperature for advanced epoxies is limited to 150 °C
to 180 °C (462). Epoxy resins provide many attractive
features, including good handling properties, processibility,
and low cost (470). Epoxies are commonly used in
structural applications. Disadvantages include brittleness
and moisture absorption that can lower use temperature
as mentioned above. Toughened epoxies have found
applications in aircraft structural composites (290) but
toughening can also signi¿ cantly lower use temperature
as indicated. Resin À ow characteristics and mechanical

properties of tetraglycidyldiaminodiphenylmethane
(TGDM) based epoxy resins can be modi¿ ed by reactive
blending with an acrylonitrile–butadiene–methacrylic
acid rubber (456).
Oxidative degradation of epoxy resins is also an important
concern. The mechanism of oxidative degradation of
an aerospace epoxy resin based upon TGDM and
triglycidylaminophenol and diaminodiphenylsulfone
has been investigated by Fourier transform infrared
analysis (237). Results show that very different
mechanisms are operative at 120 °C (close to actual use
temperatures) compared with 170 °C (representative
of accelerated ageing) where general oxidative
changes occur in all areas of the matrix. At the lower
temperature, the major reaction is probably oxidation of
a methylene group adjacent to the nitrogen atom of the
TGDM unit, whereas 170 °C ageing resulted in broader,
general changes throughout the matrix.
Phenolic Resins
Phenolics such as phenol–formaldehyde resin are
low-cost, flame-resistant, and low-smoke resins.
Applications include À ame-resistant aircraft interior
panels as well as ablative and rocket nozzle applications
(398). Phenolics provide good heat and À ame resistance,
ablative characteristics, and low cost (462). Major
shortcomings include brittleness, poor shelf-life, and
the need for high-pressure curing.
Phthalonitrile Resins
Oligomeric phthalonitrile resins have several attractive
properties for high-performance composite applications,

including very low moisture absorption and good thermal
stability (2). These resins have been used to prepare void-
free composites. Phthalonitrile end-capped oligomers
are prepared by reacting pyromellitic dianhydride, an
aromatic diamine, and 4-(aminophenoxy) phthalonitrile
(APPH). Networks can be formed by reacting the end-
capped oligomers with 4,4´-diaminodiphenyl sulfone
at elevated temperatures.
CN
CNO
H
2
N
Figure 7 Structure for APPH
Polyimides
PI are produced by a two-stage process in which a
poly(amic acid) is ¿ rst produced. This is followed by a
¿ nal imidisation step. This intermediate is very corrosive
and requires special consideration in mould design.
The high values of T
g
of PI make processing dif¿ cult.
Elimination of water from the polycondensation reaction
results in void formation that needs to be carefully
controlled. As a class, PI have good adhesion and heat
and chemical resistance as well as superior mechanical
properties. Fire retardancy can be improved by the
addition of phosphorus substituents. Use of a polyimide
oligomer can promote better ¿ bre wettability. Crosslinking
by the use a functionally terminated oligomer as in the

case of PMR-15 (in situ polymerisation of monomer
reactants and the designation ‘-15’ in PMR-15 indicated
the molecular weight of the first formed oligomer
(i.e., 1500)) can lead to high-temperature and void-free
Polymers in Aerospace Applications
10
composites. PI composite can be fabricated using quartz,
glass, boron, and graphite ¿ bres reinforcement and are
favoured as engineering laminates in supersonic aircraft
(327). The use temperature for PI is typically 200 °C to
280 °C (463), although working temperatures as high as
315 °C have been reported.
PI resins can be thermosetting and TP. For composite
applications, thermosetting PI are the primary choice.
Thermosetting polyimides can provide hot/wet use
temperature 260 °C to 320 °C. These PI are formed
by a polycondensation reaction, but the release
of volatiles may cause problems in terms of void
formation during cure. Cost is typically high for
these resins.
PMR polyimides such as PMR-15 use a two-stage curing
process. The ¿ rst-stage consists of solvent evaporation
and an imidisation reaction to form short-chain imide
oligomers with the release of condensation water. The
second stage involves a ring-opening addition-type
crosslinking reaction at nadic end groups to form the
¿ nal crosslinked polyimide matrix. The absence of
volatile release in the second stage is an advantage in
forming void-free composites. Disadvantages include
the need for a multi-stage cure process and the toxicity of

the monomer 4,4´-methylenedianiline (301, 314). Over
the past 20 years, PMR-15 has been the most widely
used PI in the aerospace industry due to its high T
g
(~340
°C) and good thermo-oxidative stability. Oxidation of
the neat resin is diffusion-controlled, resulting in the
formation of a surface oxidation layer (11). Ageing of
PMR-15 neat resin in air at 288 °C has shown a small
increase in T
g
(330 °C to 336 °C) attributed to an
increase in crosslink density (7). Ageing for 1000 hours
resulted in a visibly damaged surface layer of ~0.16
mm thickness. This layer results in a decrease in tensile
strength by acting as a crack initiation site, promoting
premature failure. Tandon and co-workers (228)
developed a model for thermo-oxidative ageing with a
diffusion-reaction model whereby temperature, oxygen
concentration, and weight-loss effects are considered.
Extensive studies of the effect of ageing on the nano-
indentation strain rate sensitivity have shown that the
average strain rate sensitivity in the oxidised surface
layer is much higher than that of the non-oxidised
interior, indicating that the oxidised surface layer has
limited ductility and, thereby, is more susceptible to
fracture [a.4]. A second-generation material is PMR
II (in situ polymerisation). LARC™-ITPI, based upon
the polycondensation of 4,4´-isophthaloyldiphthalic
anhydride (IDPA) and 1,3-phenylenediamine, is

another high-temperature PI matrix for aerospace
applications (473).
5.1.2 TP Matrices
Composites made using a TP matrix represent a small
but fast-growing market (253, 255, 290, 475). TP can be
amorphous or semicrystalline. Some of the most widely
used TP for composite applications include PEEK,
polyetherimide (PEI), and poly(p-phenylene sul¿ de)
(PPS). Representative properties are shown in Table
6. Continuous ¿ bre-reinforced TP composites (471)
provide cost-effective manufacturing achieved by a high
degree of automation. Applications include use in aircraft
interiors, wing ribs and panels, buckhead À oor panels,
and landing gear doors. Compared with thermosets, TP
composites provide the advantage of signi¿ cantly higher
impact strength. On the negative side, use temperatures
and resistance to solvents such as methyl ether ketone
and hydraulic À uids of TP composites are lower than
obtained using thermosetting composites. Such À uids
act as stress cracking agents that can lead to mechanical
failure. The properties of non-halogen ¿ re-resistant TP
have been reviewed by Lyon and Emrick (40).
Polyarylates
Aromatic polyester carbonates (polyarylates) having
the general structure:
OC
CO
OCO
O
O

CH
3
O
C
OCO
CH
3
O
Figure 8 Structure of Polyarylate
Table 6 Representative Properties of Thermoplastic Resins (474)
Polymer Morphology T
g
(ºC) Processing
Temperature
(ºC)
Yield Strength
(MPa)
Modulus (GPa)
PEEK semicrystalline 143 380–400 100 3.7
PEI amorphous 210 315–360 103 3.6
PPS semicrystalline 88 330–345 79 3.3
Polymers in Aerospace Applications
11
are available in clear/transparent and pigmented
versions that meet heat and smoke requirements for
aircraft interior applications (40).
Poly(ether ether ketone)
PEEK or poly(ether ether ketone) (Victrex
®
) is used for

the matrix of TP prepregs containing carbon, glass, and
aramid ¿ bres. PEEK has been reported to be capable
of withstanding continuous operating temperature
up to 260 °C in low-stress operations and 120 °C in
aerospace structural applications (191). PEEK has
good resistance to hydrolysis, corrosion, chemical, and
radiation exposure. It provides high thermal stability,
low coef¿ cient of expansion, good abrasion resistance,
low smoke and toxic gas emission, and excellent
stiffness (191).
O
O
O
C
Figure 9 Structure of PEEK
Poly(arylether ketone ketone)
Developed in the 1980s, PEKK is a semicrystalline
TP with low À ammability, a T
g
of 156 °C, and melting
temperatures in the range 300 °C to 310 °C (378). PEKK
is the preferred TP resin matrix at temperatures >90
°C (378). PEKK composites have been prepared from
short and continuous (i.e., tape and fabric, respectively)
glass and CF composites (378). PEKK has high hot/
wet retentions (up to 130 °C) due to low resin moisture
pick-up (378). All high-temperature glass ¿ bre sizings
are suitable with PEKK and its processing temperature
(335-345 °C) (378). Choice of sizing, however, can
signi¿ cantly affect performance.

Polyetherimide
The commercial PEI Ultem
®
has the general structure
O
O
N
CH
3
C
O
O
O
N
CH
3
O
Figure 10 Structure of PEI
PEI is an amorphous polymer, developed in the 1980s,
that offers high heat resistance, strength, and modulus.
The mechanical performance of PEI degrades with
exposure to aggressive À uids such as Skydrol hydraulic
À uid (255). The effect of moisture on the interlaminar
resistance of woven fabric PEI composite has been
reported (187). Properties of composite structures
formed by reactive heating a phenylethynyl-terminated
PEI (Reactive Ultem
®
) coating on PAN-based CF
have been reported (189). A suggested application

is the rigidisation of inÀ atable composite structures
in space.
Polyimides
PI composites have been used at temperatures >300
°C for electronics and aerospace applications (466).
High-temperature coupling agents for S-glass and
quartz fabric-reinforced PI are required at these
temperatures to maintain high flexural strength
(466). Thermoplastic polyimides (TPI) include
LARCTM-TPI based on benzophenone dicarboxylic
dianhydride and 3,3´-diamino benzophenone
(254), LARCTM-ITPI based upon IDPA and
1,3-phenylenediamine (473), NR-10 B2 prepared
by reacting hexaÀ uoro isopropylidene dianhydride
with a 95/5 molar ratio of p/m-phenylene diamine,
and polyimide 2080 produced by the reaction of
benzophenone dicarboxylic acid dianhydride with a
mixture of 80/20-toluene diisocyanate and methylene
4,4´-diisocyanate (254).
O
O
O
N
N
O
O
O
Figure 11 Structure of LARC-ITPI
Matrimid® is a high T
g

(approximately 313 °C)
amorphous TPI made from diaminophenylindane and
3,3´-4,4´-benzophenone tetracarboxylic dianhydride
(BTDA).
N
N
O
O
O
C
O
O
Figure 12 Structure of Matrimid
Polymers in Aerospace Applications
12
Polyamideimides such as Torlon
TM
, prepared by reacting
trimellitoyl acid chloride with a mixture of 70/30 4,4´-
diamino diphenyl oxide and phenylene diamine, has
some of the properties of polyamides such as toughness
and ductility, and the high heat resistance of PI.
O
O
O
NO
NH
Figure 13 Structure of Polyamideimides
PPS
Current grades of PPS (e.g., Forton

®
) exhibit good
resistance to temperatures up to 240 °C (melting point
between 280 °C and 290 °C) and are resistant to oils,
fuels, solvents, anti-icing agents, and to acids/bases
in the pH range 2 to 12. Other attractive properties
include excellent hardness, dimensional stability,
and excellent ¿ re resistance. Water absorption is near
0.04%, signi¿ cantly lower than for other TP (including
PEI and PEEK) used in aerospace applications.
PPS can be processed by various TP composite
technologies, including pultrusion, compression
moulding, thermoforming, automated tape laying/¿ bre
placement, and bladder moulding. Use of PPS matrix
has been reported for structural applications on the
Airbus A340 and A380 (290).
S
Figure 14 Structure of PPS
Polysulfones
Polysulfones that have been used in aerospace
applications for aircraft interiors, and TP composite
applications include bisphenol A polysulfone (PSF,
UDEL
TM
) and polyphenylsulfone (PPSU, Radel
TM
).
OCO
O
O

S
CH
3
CH
3
Figure 15 Structure of PSF
OO
O
S
O
Figure 16 Structure of PPSU
5.2 Fabrication Methods
Fibre reinforcement and matrix resin may be combined
in a single step by various processes such as wet lay-
up, ¿ lament winding, pultrusion, and RTM. For some
applications, resin-impregnated ¿ bres (prepregs) are
used. Prepregs can be made by using solvent, holt-
melt, or powder impregnation techniques. A ¿ bre-to-
matrix ratio is typically 60:40 or higher for advanced
composite materials (398). Resistive heating has been
proposed as a route for the rigidisation of inÀ atable
composite structures in space (189). The properties of
a CF-reinforced heat-crosslinkable PEI (Ultem
®
) have
been reported. Forming processes for TP composites
include thermoforming, press-forming, compression
moulding, matched-die moulding, welding, and
diaphragm forming (448). Compression moulding
is a high-volume, high-pressure method suitable for

complex, high-strength glass-mat reinforced TP.
Resin Transfer Moulding
In the RTM process, a resin including high-temperature
PI is injected into a closed cavity mould ¿ lled with ¿ bre
reinforcement (314). RTM offers low fabrication cost
compared with other alternatives such as autoclaving.
High-temperature composite parts prepared by RTM
have been incorporated in many high-performance
military aircraft including the F-22 Raptor (314) where
a RTM-processed bismaleimide prepreg has been
used (467). The mould may be evacuated to assist the
moulding process (vacuum-assisted RTM) (253).
5.3 Non-destructive Testing
Ultrasound techniques were used to monitor the cure of
¿ breglass in 1966. Combined with other non-destructive
evaluation techniques such as thermography and
radiography techniques, composite properties such as
density, modulus, and strength can be determined (280).
Polymers in Aerospace Applications
13
6. Nanocomposites
Several excellent review articles on the properties and
processing of nanocomposites are available (3, 41,
180, 206, 250, 312, 331, 358, 450 [a.5]). In general,
the distinguishing characteristic of nanocomposites
compared with more traditional composite materials is
the dimensions of the reinforcing ¿ ller. Nancomposites
contain inorganic reinforcements with high aspect ratio
and dimensions of 1–100 nm. The small size results in
properties often superior to traditional composites. Some

of the attractive properties of nanocomposites important
for aerospace application include improved electrical
and mechanical properties, reduced oxygen and water
permeability, increased thermal stability, better À ame
resistance, improved resistance to wear, elevated heat-
distortion temperature, potential for surface and interface
modi¿ cation, and easier processibility. Applications
include fire-retardant coatings, rocket propulsion
insulation, rocket nozzle ablative materials, aerospace
structural panels, ultra-light space structures, and space
mirror substrates (310, 298). Other potential aerospace
applications include devices such as light-emitting
diodes, photovoltaic cells, and gas sensors [a.6].
One of the ¿ rst nanocomposites was fabricated from
Nylon-6 by researchers at Toyota in the late 1980s.
Typical properties of nylon nanocomposites are given
in Table 7. As shown, tensile modulus and strength
are signi¿ cantly improved without sacri¿ cing impact
strength. Particularly noteworthy is the improvement
in heat-distortion temperature due to the reinforcement.
The use of nanocomposite material has been increasing
very rapidly since the 1980s. The US market for
nanocomposites is expected to reach 11 billion pounds
by the year 2020.
Table 7 Representative Properties of a Nylon-6
Nanocomposite [a.3]
Property Nylon-6 Nancomposite
Coef¿ cient of thermal
expansion (×10
5

)
13 6.3
Heat-distortion
temperature (°C)
65 145
Tensile modulus (GPa) 1.1 2.1
Tensile Strength (MPa) 69 107
Impact strength (kJ/m
2
) 2.3 2.8
Water absorption (%) 0.87 0.51
Property improvement can be signi¿ cant at small loading.
For example, the modulus of polydimethylsiloxane
reinforced by 1% clay can be increased by approximately
100%. For a polysulfone organoclay nanocomposite,
modulus and strength reach a maximum at about 3 wt%
organoclay content with little sacri¿ ce in elongation at
break (461). At higher loading, exfoliation decreases
and mechanical properties decline.
Nanocomposites have been prepared from nearly all
commodity and engineering-grade plastics, including
thermosetting resins. Examples of TP include
polysiloxanes, Nylon 11, poly(vinyl acetate)–acrylic
copolymer, poly(ethylene oxide), PEI, PI, and some TP
elastomers such as polyamide silicone copolymer (298).
Thermosets include phenolic, cyanate ester, and epoxies.
Nanocomposite can be made using various ¿ llers having
at least one dimension in the nanometer range (95).
Fillers include nanoclays, nanotubes, nano¿ bres, or silica
and various metal oxides. Nano¿ bres are electrospun

whiskers with diameters in the range 10–100 nm and
length-to-diameter ratios >1000.
6.1 Nano-Reinforcements
Fillers used for nanocomposites include organic-
modi¿ ed montmorillonite (MMT) nanoclays, nanosilica,
carbon nano¿ bre (CNF), carbon nanotubes (CNT),
polyhedral oliogomeric silsesquioxane (POSS), and
various nanoparticles such as silica and more exotic
¿ llers such indium tin oxide (ITO) (298).
MMT
The commonest form of nano-reinforcement is organoclay,
MMT. MMT is a naturally occurring 2:1 phylloslicate with
the same structure as talc and mica, but a different layer
charge. Modi¿ cation of the inorganic surface of MMT
by organic treatment is used to increase dispersion in the
polymer matrix. The crystal structure of MMT consists of
1 nm thin layers with a central octahedral sheet of alumina
fused between two external silica tetrahedral sheets. These
platelets have thicknesses of ~1 nm with aspect ratios (i.e.,
diameter:thickness) of 10:1 to 1000:1 and are arranged
in stacks that can be separated (or exfoliated) during
composite fabrication. Isomorphoic substitution within
the layers (e.g., replacing Al
3+
by Mg
2+
) can be used to
modify the charge exchange capacity. The silicate sheets
in MMT are separated by cations, typically sodium, as
illustrated in Figure 17. These cations balance the overall

charge. The sodium cation in the gallery can be exchanged
with other cations such as lithium, potassium, and calcium.
In water-swollen layered silicates, organic cations, such
as an alkyl ammonium cation, can also be used to
replace Na
+
. The speci¿ c alkyl selection can be used
to improve miscibility with the nanocomposite matrix.
Polymers in Aerospace Applications
14
Some examples include dimethyl distearyl ammonium
chloride and dimethyl stearyl benzyl ammonium chloride.
Silicone rubber nanocomposites can be fabricated by ion-
exchanging Na
+
/MMT with dimethyl ditallow ammonium
bromide or hexadecyltrimethylammonium bromide. This
type of organophilic modi¿ cation improves the polymer
miscibility of MMT. The ion-exchange process also
increases the gallery height in relation to the molecular
size of the organic cation.
Figure 17 Structure of sodium montmorillonite.
Reproduced with permission from Southern Clay
Product, Incorporated
Nanosilica
Nanosilicas such as Aerosil
®
are very pure amorphous
silica produced by high-temperature hydrolysis of
silicon tetrachloride in an oxy-hydrogen gas À ame

to produce particles in the range 7–40 nm (298).
Hydrophilic and hydrophobic grades of nanosilicas are
commercially available. Alkoxysilyl functional groups
can improve matrix–silica binding (197).
Polyhedral Oligomeric Silsesquioxanes
Polyhedral oligomeric silsesquioxanes (POSS is a
trademark of Hybrid Plastics (www.hybridplastics.
com)) can serve as multifunctional additives providing
molecular-level reinforcement as well as serving as
processing aids and flame retardants (298). Other
advantages of POSS-filled nanocomposites include
increased service temperature, low density, low thermal
conductivity, thermo-oxidative resistance, and ageing
resistance. The chemical composition of POSS (RSiO
1.5
),
is intermediate between that of silica (SiO
2
) and silicones
(R
2
SiO). The commonest POSS has eight silicon atoms,
each carrying an organic group (Figure 18). The typical
dimensions of POSS particles are 1–3 nm.
Figure 18 Representation of a typical POSS structure.
Possible organic substituents, R, are indicated.
Reproduced with permission from D.R. Paul and L.M.
Robeson, Polymer, 2008, 49, 15, 3187.
© 2008, Elsevier
Carbon Nano¿ bres

CNF are discontinuous graphic ¿ laments produced in
the gas phase by the pyrolysis of hydrocarbons. Typical
diameters of CNF range 50 nm to 200 nm with lengths
in the range 50 ȝm to 100 ȝm.
Carbon Nanotubes
CNT provide attractive combinations of high
À exibility and strength combined with high stiffness
and low density. Carbon nanotubes can be single-
walled (SWNT) or MWNT. SWNT have diameters
as small as 0.4 nm compared with MWNT that have
diameters in the range 2–25 nm. The typical tensile
strength of CNT is 100–600 GPa. This range is about
two orders of magnitude higher than that of typical CF.
Densities of CNT are about 1.3 g/cm
3
compared with
1.8–1.9 g/cm
3
for CF (310). Compressive strengths
of CNT are about two orders of magnitude higher
than that of any other ¿ bre. CNT also have extremely
high stiffness, with Young’s modulus in the range
1–5 TPa, compared with 750 GPa for CF. CNT can
also carry large current densities (>100 MA/cm
2
for
MWNT). Experimental thermal conductivities are
about 200 W/(m·K). A problem with the use of CNT
is the need for chemical modi¿ cation for favourable
interaction with polymeric matrices. Their use

requires high dispersion. Techniques used to achieve
good dispersion include in situ polymerisation of
the matrix, shear mixing, the use of surfactants, and
solution processing (310).
Graphite Nanoplatelets
An alternative to CNT is the use of graphite
nanoplatelets, especially for conducting nanocomposite
applications. Several forms of nanographite include
Polymers in Aerospace Applications
15
expanded graphite, exfoliated graphite, and graphene.
Functionalised graphene sheets can be prepared by
controlled thermal expansion of graphite oxide.
6.2 Processing
Methods to disperse nanoparticles include high-shear
mixing for liquid resins and three-roll milling for
liquid resins, Brabender-type mixing for high-viscosity
resins, and twin-screw extrusion for solid polymers
(298). The process of exfoliation of surface-treated
nanoclays under high-shear mixing is illustrated in
Figure 19. Exfoliation results in improved mechanical
properties, barrier performance, and application
processing. Exchange of natural Na
+
counter-
ions with long-chain quaternary ammonium cations
results in improved dispersion into hydrophobic
polymers (298).
Figure 19 Mechanism of organoclay dispersion
and exfoliation during melt processing. Reproduced

with permission from D.R. Paul and L.M. Robeson,
Polymer, 2008, 49, 15, 3187. © 2008, Elsevier
6.3 Properties of Nanocomposites
One of the most signi¿ cant effects of nano¿ llers on the
properties of the matrix polymer is the signi¿ cant increase
in modulus compared with the neat resin. The addition of
nano-sized ¿ llers (especially organoclays) can increase
modulus and tensile strength at signi¿ cantly smaller
¿ ller content compared with more traditional reinforcing
agents such as glass ¿ bre. Modelling of the mechanical
properties of nanocomposite materials has been given
(183, 227, 315, 424). The effect of wt% ¿ ller on relative
modulus (i.e., the ratio of composite modulus to matrix
polymer modulus) is compared for MMT and glass ¿ bre-
¿ lled Nylon 6 in Figure 20. As shown, approximately 20
wt% of glass ¿ bre is necessary to increase the modulus
of Nylon 6 to the same level achieved by addition of 7
wt% of MMT.
Figure 20 Comparison of relative modulus (i.e., the
ratio of the modulus of the nancomposite to that of the
matrix polymer) at different concentrations of glass
¿ bre and MMT concentration in Nylon 6. Reproduced
with permission from T.D. Fornes and D.R. Paul,
Polymer, 2003, 44, 17, 4993. © 2003, Elsevier
Advantages of nanocomposites include improved barrier
to fuel and dimensional stability (i.e., lower CTE)
(301). Higher oxygen barrier performance can increase
thermo-oxidative stability (301). For example, the oxygen
permeability coef¿ cients of polyimide nanocomposites
have been reported to drop by two-thirds and the thermal

expansion coefficient to drop by 20% (301). Water
resistivity also can be improved by adding reactive
inorganic ¿ llers. Nanocomposite ¿ lms of CNT and ITO
in polysiloxane have the capability for thermal control in
satellite applications (197). Such nanocomposites provide
anti-static properties. POSS and CNT can signi¿ cantly
reduce the heat release rate and, thereby, improve À ame
retardancy (235). Whereas nano¿ llers have small effects
on the T
g
, the effect on the HDT is signi¿ cant due to the
large reinforcement effect of the nano¿ ller, as illustrated in
Figure 21. As shown, the storage modulus, qualitatively
related to the tensile modulus, is increased in the glassy
region as well as the rubbery plateau. The result is a
signi¿ cant increase in the heat distortion temperature.
Figure 21 Dynamic mechanical storage modulus of
Nylon 6 as a function of temperature and wt% MMT
content. The horizontal line illustrates how HDT at an
applied stress of 1.82 MPa changes with MMT loading.
Reproduced with permission from T.D. Fornes and D.R.
Paul, Polymer, 2003, 44, 17, 4993. © 2003, Elsevier
Polymers in Aerospace Applications
16
The effect of oxydianiline (ODA)-modi¿ ed clay on the
tensile properties of a BTDA-ODA polyimide is illustrated
in Figure 22. Values represent relative modulus, relative
maximum stress at break, and relative elongation at
break (compared with the neat polyimide). As shown,
the modulus is increased by more than threefold at only 7

wt% ODA-modi¿ ed organoclay. This increase in stiffness
is accompanied by smaller improvements in stress and
elongation at break. A similar improvement in tensile
modulus and stress with a maximum at 3 wt% MMT has
been reported for polysulfone nanocomposites (461).
Figure 22 Relative tensile properties (property of
nanocomposite to that of the matrix polymer) reported
for a polyimide (BTDA–ODA) nanocomposite
prepared using ODA-modi¿ ed organoclay. Data taken
from H-L. Tyan, K-H. Wei and T-E. Hsieh, Journal
of Polymer Science Part B: Polymer Physics Edition,
2000, 38, 22, 2873. © 2000, Elsevier
7. Foams
In use since 1971, polymethacrylimide (PMI) has
been fabricated into foam cores offering high strength,
stiffness, and fatigue life. Thermoformed PMI foam
has been used in many aerospace applications (252) as
an alternative to Nomex
®
and aluminium honeycomb
structures. Applications include helicopter rotor blades
and structural sandwich cores of fuselage panels, as well
as stringer pro¿ les in pressure bulkheads.
References
a.1. V. Kholodovych and W.J. Welsh in Polymer
Data Handbook, Ed., J.E. Mark, Oxford
University Press Inc., New York, NY, USA,
2009, p.386.
a.2. V. Kholodovych and W.J. Welsh in Polymer
Data Handbook, Ed., J.E. Mark, 2009, Oxford

University Press Inc., New York, NY, USA,
2009, p.394.
a.3. J.R. Fried, Polymer Science & Technology, 2nd
Edition, Prentice Hall Upper Saddle River,
Prentice Hall, NJ, USA, 2003.
a.4. Y.C. Lu, G.P. Tandon, S. Putthanarat and G.A.
Schoeppner, Journal of Materials Science, 2009,
44, 8, 2119.
a.5. R.A. Vaia and E.P. Giannelis, MRS Bulletin,
2001, 26, 5, 394.
a.6. D.Y. Godovsky in Biopolymers, PVA Hydrogels,
Anionic Polymerisation, Nanocomposites,
Advances in Polymer Science No. 153,
Springer, Berlin, Germany, 2000, p.163.
Abbreviations for Polymers in
Aerospace Applications
APPH 4-(Aminophenoxy) phthalonitrile
BMI Bismaleimides
BTDA 3,3´-4,4´-Benzophenone tetracarboxylic
dianhydride
CE Cyanate esters
CF Carbon ¿ bre(s)
CFRP Carbon ¿ bre reinforced plastics
CNF Carbon nano¿ bre
CNT Carbon nanotubes
CTE Coef¿ cient of thermal expansion
EMI Electromagnetic interference
HDT Heat distortion temperature
IDPA 4,4´-Benzophenone isophthaloyldiphthalic
anhydride

ITO Indium tin oxide
Polymers in Aerospace Applications
17
MMT Montmorillonite
MWNT Multiwall carbon nanotubes
ODA Oxydianiline
PAN Polyacrylonitrile
PBI Polybenzimidazole
PBO Poly(p-phenylene-2,6-benzobisoxazole)
PBZT Polybenzothiazole
PEEK Poly(aryl ether ether ketone)
PEI Polyetherimide
PEKK Poly(ether ketone ketone)
PI Polyimide(s)
PMI Polymethacrylimide
PMR In situ polymerisation of monomer
reactants.
POSS Polyhedral oligomeric silsesquioxanes
PPS Poly(p-phenylene sul¿ de)
PPSU Polyphenylsulfone
PSF Polysulfone
RFI Radio frequency interference
RTM Resin transfer moulding
SWNT Single wall carbon nanotubes
T
g
Glass transition temperature
TGA Thermogravimetric analysis
TGDM Tetraglycidyldiaminodiphenylmethane
TP Thermoplastic

TPI Thermoplastic polyimides
UHMWPE Ultra-high molecular weight
polyethylene
UV Ultraviolet
VGCF Vapour-grown carbon ¿ bre