CRANFIELD UNIVERSITY Leigh Dunn Investigating accidents involving aircraft manufactured from ...

382 Pages·2014·42.45 MB·English

CRANFIELD UNIVERSITY

Leigh Dunn

Investigating accidents involving aircraft manufactured from polymer
composite materials

School of Engineering

PhD
Academic Year: 2009 - 2013

Supervisors: Prof. Graham Braithwaite & Dr. Matthew Greaves
March 2013

CRANFIELD UNIVERSITY

School of Engineering

PhD

Academic Year 2009 - 2013

Leigh Dunn

Investigating accidents involving aircraft manufactured from polymer
composite materials

Supervisors: Prof. Graham Braithwaite & Dr. Matthew Greaves
March 2013

© Cranfield University 2013. All rights reserved. No part of this
publication may be reproduced without the written permission of the
copyright owner.

ABSTRACT
This thesis looks into the examination of polymer composite wreckage from the
perspective of the aircraft accident investigator. It develops an understanding of
the process of wreckage examination as well as identifying the potential for
visual and macroscopic interpretation of polymer composite aircraft wreckage.
The in-field examination of aircraft wreckage, and subsequent interpretations of
material failures, can be a significant part of an aircraft accident investigation.
As the use of composite materials in aircraft construction increases, the
understanding of how macroscopic failure characteristics of composite materials
may aid the field investigator is becoming of increasing importance.
The first phase of this research project was to explore how investigation
practitioners conduct wreckage examinations. Four accident investigation case
studies were examined. The analysis of the case studies provided a framework
of the wreckage examination process.
Subsequently, a literature survey was conducted to establish the current level of
knowledge on the visual and macroscopic interpretation of polymer composite
failures. Relevant literature was identified and a compendium of visual and
macroscopic characteristics was created.
Two full-scale polymer composite wing structures were loaded statically, in an
upward bending direction, until each wing structure fractured and separated.
The wing structures were subsequently examined for the existence of failure
characteristics. The examination revealed that whilst characteristics were
present, the fragmentation of the structure destroyed valuable evidence.
A hypothetical accident scenario utilising the fractured wing structures was
developed, which UK government accident investigators subsequently
investigated. This provided refinement to the investigative framework and
suggested further guidance on the interpretation of polymer composite failures
by accident investigators.
Keywords: Fractography, Reconstruction, Failure Analysis, Fracture, Mishap
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ACKNOWLEDGEMENTS
I would like to express my sincere thanks and acknowledgement to the following
for their contribution and generosity:
To Professor Graham Braithwaite and Dr Matthew Greaves for their patience,
advice, support, encouragement, and for providing me with the opportunity to
conduct doctoral research. My time at Cranfield University has been an
amazing experience and for this I am truly grateful.
To the investigation community and specifically to those who offered their time
through participating in my research or sharing their knowledge and experience.
This research would not be possible without their assistance.
My research touched many parts within Cranfield University. I would like to
express my appreciation to the staff and students in the Department of Air
Transport, both past and present, for their support and encouragement. I would
like to acknowledge the support from the School of Applied Science, specifically
to Ben Hopper, Dr Giuseppe Dell'Anno, and Dr Isidro Durazo-Cardenas.
To my wife Sarah Jane for her love, patience, understanding and support which
was provided always and without question. Also, to my daughter Sophie Lauren
who, without realising it, gave me strength and happiness. The journey would
not have been possible without them.
To my friend and colleague Marie Langer whose friendship, support and advice,
enlightened the journey. It was a pleasure to walk the path of doctoral research
with you.
To my parents for their support and encouragement, and to Roger Newman for
his enthusiasm, encouragement and proof reading skills.
And finally, to all of those whose work has taught or inspired me, for:
“If I have seen further it is by standing on the shoulders of giants” – Isaac
Newton, 1676
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TABLE OF CONTENTS
ABSTRACT .......................................................................................................... i!
ACKNOWLEDGEMENTS ................................................................................... iii!
LIST OF FIGURES .............................................................................................. x!
LIST OF TABLES ............................................................................................. xvii!
LIST OF ABBREVIATIONS .............................................................................. xix!
1 INTRODUCTION .............................................................................................. 1!
1.1 Introduction to research ............................................................................. 1!
1.2 Research Aims & Objectives ..................................................................... 7!
1.2.1 Overall aim .......................................................................................... 7!
1.2.2 Objectives ............................................................................................ 7!
1.3 Research programme ................................................................................ 7!
1.3.1 Objective 1 .......................................................................................... 7!
1.3.2 Objective 2 .......................................................................................... 8!
1.3.3 Objective 3 .......................................................................................... 8!
1.3.4 Objective 4 .......................................................................................... 8!
1.4 Contribution to knowledge ......................................................................... 9!
1.5 Thesis structure ....................................................................................... 11!
2 CONTEXT TO RESEARCH ........................................................................... 14!
2.1 The need to investigate accidents ........................................................... 15!
2.2 A change in technology ............................................................................ 16!
2.3 Composite materials ................................................................................ 22!
2.3.1 Reinforcements ................................................................................. 23!
2.3.2 Matrices ............................................................................................. 26!
2.4 The growth in polymer composite materials in aircraft construction ........ 27!
2.5 Summary .................................................................................................. 31!
3 LITERATURE REVIEW .................................................................................. 32!
3.1 Introduction .............................................................................................. 33!
3.2 Investigation of wreckage ........................................................................ 33!
3.2.1 The knowledge and skills to conduct a wreckage examination ......... 38!
3.2.2 The examination of material failures within aircraft accident
investigation ............................................................................................... 40!
3.2.3 The visual and macroscopic failure characteristics of polymer
composite materials ................................................................................... 44!
3.3 Investigation process ............................................................................... 50!
3.3.1 Data, facts, information and evidence ............................................... 50!
3.3.2 Investigation framework .................................................................... 54!
3.4 Research conducted to assist the field investigator in examining
polymer composite materials ......................................................................... 65!
3.4.1 NIAR .................................................................................................. 65!
3.4.2 ATSB - “Fibre composite aircraft – capability and safety” ................. 68!
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3.4.3 Exponent: Failure analysis of composites – a manual for aircraft
accident investigators ................................................................................. 70!
3.4.4 American Airlines flight 587 ............................................................... 72!
3.4.5 The failure examination of composite structures using visual and
macroscopic examination ........................................................................... 73!
3.5 Summary .................................................................................................. 74!
4 EXPLORATORY STUDY ON THE INVESTIGATION OF COMPOSITE
AIRCRAFT ACCIDENTS ................................................................................... 76!
4.1 Research Design and Methodology ......................................................... 77!
4.2 Data collection protocol ............................................................................ 80!
4.2.1 Establishing case study questions on the “science” of
investigation ............................................................................................... 80!
4.2.2 Establishing case study questions on the “art and craft” of
investigation ............................................................................................... 84!
4.3 Ethical considerations .............................................................................. 87!
4.3.1 Psychological harm ........................................................................... 87!
4.3.2 Harm to career .................................................................................. 88!
4.3.3 Freedom of participation .................................................................... 88!
4.3.4 Confidentiality, anonymity and data security ..................................... 89!
4.3.5 Ethics approval .................................................................................. 89!
4.4 Ensuring academic rigour ........................................................................ 89!
4.5 Number of cases to be studied ................................................................ 90!
4.6 Case selection criteria .............................................................................. 91!
4.6.1 Wreckage pattern as a means to suspect in-flight structural failure .. 92!
4.6.2 Basic types of in-flight structural failure ............................................. 93!
4.6.3 Variation in case selection ................................................................. 94!
4.6.4 Common features of the cases ......................................................... 94!
4.7 Case screening and engagement ............................................................ 96!
4.8 The use of anonymous case identities ..................................................... 97!
4.9 Case study pilot test ................................................................................. 98!
4.10 Case descriptions .................................................................................. 99!
4.10.1 Case 1 – Structural damage due to flight into terrain ...................... 99!
4.10.2 Case 2 – Premature in-flight failure of a flight critical composite
structure ................................................................................................... 100!
4.10.3 Case 3 – In-flight breakup initiated by a premature structural
failure ........................................................................................................ 101!
4.10.4 Case 4 – Structural failure due to aeroelastic overload ................. 102!
4.11 Data analysis methods ......................................................................... 103!
4.12 Analysis ................................................................................................ 105!
4.12.1 Finding 1 ........................................................................................ 106!
4.12.2 Finding 2 ........................................................................................ 111!
4.12.3 Finding 3 ........................................................................................ 112!
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