Bouvet - Mechanics of Aeronautical Composite Materials

1. 1 Presentation of an Aeronautical Unidirectional Composite
2. 14 Exercises
3. 15 Solutions to the Exercises

1. Introduction
2. 1 Presentation of an Aeronautical Unidirectional Composite
3. 2 Characteristics of UD Ply
4. 3 Characteristics of a UD Ply in a Given Direction
5. 4 Fracture of a Laminated Composite
6. 5 Fracture Criteria of a UD Ply
7. 6 Membrane Behavior of a Laminated Composite Plate
8. 7 Bending Behavior of a Laminated Composite Plate
9. 8 The Fracture Criterion of a Laminate
10. 9 Damage Tolerance
11. 10 Interlaminar and Out-of-Plane Shear Stress
12. 11 Holed and Bolted Plates
13. 12 Buckling
14. 14 Exercises
15. 15 Solutions to the Exercises

Christophe Bouvet

First published 2017 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.

Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:

ISTE Ltd

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www.iste.co.uk

John Wiley & Sons, Inc.

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USA

www.wiley.com

ISTE Ltd 2017

The rights of Christophe Bouvet to be identified as the author of this work have been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.

Library of Congress Control Number: 2017941155

British Library Cataloguing-in-Publication Data
A CIP record for this book is available from the British Library
ISBN 978-1-78630-114-7

When my young colleague gave me his manuscript to proofread and asked me to write a few words for a foreword, it is with great pleasure that I accepted, even though the preamble and title were quite sufficient to present this book.

Many books have been written on composite materials. The originality of this one comes in part from the objective, which is targeted towards aircraft structures made of composite materials. To this end, the calculation of holed structures, and their subsequent multi-bolt joints, and the theme of damage tolerance are presented alongside the problems that they carry with them, as well as the calculation methods that are currently in use. These two axes are rarely presented in the literature, yet they are essential to perform an accurate and realistic sizing since they often govern the resistance of a given structure and thus its sizing.

This book covers all classic notions surrounding composite structures. Theoretical formulae are presented concisely and without unnecessary developments allowing the focus to remain on the essentials. When studying criteria, another crucial point, the differences between first damage and final fracture are made abundantly clear, something that is essential for achieving optimal structures and performing realistic calculations. This is another essential aspect of composite calculations that is nonetheless quite absent from the literature.

Lastly, a number of exercises surrounding all studied themes are proposed with complete and detailed corrections. They will allow the readers to assimilate the presented themes more easily. This is without doubt one of this books strongest assets as there are few other titles that carry quite this many examples.

I recommend reading this book as it uses concision and precision to provide essential bases for designing and sizing composite structures.

Jean-Jacques BARRAU
Former Professor at the University Paul Sabatier
Toulouse, France

The objective of this lesson on composite structure sizing is to present the principles that allow the sizing of composite laminates widely used in composite structures. After a brief presentation of the primary material used in aircraft structures, the basic theory of laminated plates under membrane and bending loading as well as their associated fracture criteria is touched on. The fracture of a UD ply is then explained in detail, in order to demonstrate its inherent complexity and the limits of the criteria in use. Next, these criteria of the base ply are used to size a complete composite laminate. Lastly, two fundamental cases of structure calculations are presented: sizing holes and multi-bolt joints, as well as the study of buckling.

The criteria that are specific to aviation, in particular the notion of limit loads and ultimate loads, are addressed. The notion of damage tolerance specific to aviation is then presented, and in particular the notion of impact damage tolerance. These notions are fundamental to understanding the specificities of sizing aircraft composite structures.

Corrected exercises then allow curious readers to test their understanding of the different subjects. These corrected exercises are typical for sizing aircraft composite structures. Engineers will also find exercises that resemble their case studies. Lastly, an Excel spreadsheet allows the presentation of the calculations in the book in detail for review (available to download at www.iste.co.uk/bouvet/aeronautical2.zip).

The originality of this particular title is that it places itself very clearly in the field of aviation, where the sizing criteria are very specific. Take the calculation of holed plates and multi-bolt joints that are typical for composite aircraft structures and yet are not often touched on in the literature. Nonetheless, the notions in this book remain valid for most industrial purposes.

Another originality of this book is that it shows a number of typical calculations for aeronautics. These examples illustrate the many complexities of sizing for composite laminates. Readers can also easily perform these calculations using the Excel spreadsheet provided.

Lastly, this book groups many of the notions required to understand sizing for aircraft composite structures, and it should interest engineers who work in that field.

We will also note that the field of aeronautics is not the only one interested in using composite structures, and other areas, such as automotive, railway or civil engineering (bridges, etc.) increasingly use composite structures. While the field of aviation has precedence when it comes to composite structure sizing, it should be noted that these methods will be widely used in other fields in the years to come.

Christophe BOUVET
June 2017

Composite materials are increasingly used within industry, thanks to their high performance to mass ratio. This is, of course, particularly true in aviation and airspace due to the crucial importance of the mass of such structures (). This high performance to mass ratio is due to the use of materials with specific mechanical characteristics such as carbon, glass or Kevlar. This type of material nonetheless presents the major drawback of being brittle, and therefore needs to be used in combination with a less brittle material such as resin. This is the basic concept of composites, which join a brittle resistant material (typically fibers of varying length depending on the application) with a less effective but more resistant matrix (typically resin). Dont forget that there is then an interface that appears between the two materials which also plays an important role in the behavior of the composite.