Crashworthy Design and Analysis of Aircraft Structures

286 Pages·2014·9.02 MB·English

by  Siromani, Deepak

Crashworthy Design and Analysis of Aircraft Structures

A Thesis

Submitted to the Faculty

of

Drexel University

by

Deepak Siromani

in partial fulfillment of the

requirements for the degree

of

Doctor of Philosophy

December 2013
ii

© Copyright 2013
Deepak Siromani. All Rights Reserved
iii

DEDICATIONS

To my parents, Sumi and Anton, and to my sister, Shalini,
for their endless love and support
iv

ACKNOWLEDGEMENTS

As expected, the accomplishment of a Ph.D. Dissertation requires the advice,
help, and support of many. First and foremost, I would like to express my sincere
gratitude to my two advisors, Professors Jonathan Awerbuch and Tein-Min Tan of the
Department of Mechanical Engineering and Mechanics. This dissertation would not have
been possible without their guidance, their constant support, and their encouragement
throughout my studies at Drexel.
The members of my thesis committee are Professors Caglan Kumbur, Leslie
Lamberson, Matthew McCarthy, and Frank Moon. I appreciate their willingness to serve
in that capacity and review my work.
I am deeply grateful to Dr. Alan Byar of The Boeing Co., Seattle, Washington,
who developed the original Boeing 737 model which was the basis for my extended
modeling of aircraft crashworthiness, and for offering valuable advice on important
computational matters throughout the course of this study.
For the experimental work on the composite stanchions, credit is due to the
several undergraduate senior students who were instrumental in the process of fabricating
the specimens and performing the experiments, as part of their senior design projects.
They are: Gary Henderson, Doug Mikita, Kevin Mirarchi, Ryan Park, John Smolko,
Benjamin Cheng, Michael DeLuca, Daniel Donegan, Patrick Giberson and Christopher
Mucerino. I also wish to acknowledge the help of Mr. Douglas Ludin of The Boeing Co.,
Ridley Park, Pennsylvania, for providing the test materials and facilitating the fabrication
of the composite specimens.
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This research was supported in part by the FAA-Drexel Fellowship program, by
providing travel funds to various conferences, and the National Science Foundation
through XSEDE resources provided by Pittsburgh Supercomputing Center. The support
provided by the College of Engineering through the Freshman Engineering Design
Fellowship, where I served as a teaching fellow throughout my years in graduate school,
is deeply appreciated. Specifically, I am very grateful to Dr. Eli Fromm for giving me the
opportunity to take a leadership role in this course sequence which undoubtedly enhanced
my communication and teaching skills.
I am thankful to the MEM Department and Drexel University for providing an
excellent undergraduate and graduate education. The partial support provided by the
MEM Department, through its teaching assistantship program, was also highly valuable. I
am grateful for my colleagues and friends in the MEM department and in our research
group, especially Chris Swin, Reewanshu Chadha and Andrew Bergan, for their help
with numerous issues, for the thoughtful discussions and suggestions along the way and
their committed friendship that developed throughout these years.
Most importantly of all, I would like to thank my family for always supporting
me, encouraging me, and believing in me through all the major decisions I have had to
make so far. Without them, I would not be the person I am today. Last, but not the least, I
would like to thank all my friends for their help and support over the years, that has
undoubtedly helped me complete this dissertation.
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TABLE OF CONTENTS

List of Tables .................................................................................................................... xii
List of Figures .................................................................................................................. xiv
Abstract .......................................................................................................................... xxvi
Chapter 1: Introduction ........................................................................................................1
1.1. Aircraft Crashworthiness ...................................................................................1
1.2. Energy Absorbing Structures .............................................................................4
1.3. Summary of Research Program .........................................................................9
1.4. Dissertation Format ..........................................................................................11
Chapter 2: Crashworthiness Analysis of a Boeing 737 Fuselage Section: A Parametric
Study on the Effects of Friction and Angle of Impact .......................................................13
2.1. Abstract ............................................................................................................13
2.2. Introduction ......................................................................................................13
2.3. Drop Test of a B737 Fuselage Section ............................................................17
2.4. Finite Element Models of the B737 Fuselage Section .....................................20
2.5. Parametric Study ..............................................................................................24
2.5.1. Effect of Coefficient of Friction .............................................................25
2.5.2. Effect of Under Floor Luggage ...............................................................31
2.5.3. Effect of Angle of Impact .......................................................................32
2.6. Concluding Remarks ........................................................................................38
Chapter 3: Multi-terrain Crashworthiness Simulations of the Fuselage of a Narrow-body
Transport Aircraft ..............................................................................................................41
3.1. Abstract ............................................................................................................41
3.2. Introduction ......................................................................................................41
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3.3. Development of the Full-Length Fuselage Model ...........................................44
3.3.1. Development of the Modified Section Model ........................................46
3.3.2. Validation of the Modified Section Model .............................................47
3.3.3. Expansion of the Modified Section Model to a Full-length Fuselage
Model .................................................................................................................54
3.4. Full-length Model Simulations ........................................................................56
3.4.1. Crash Landing Simulation Results .........................................................58
3.4.2. Vertical Impact Simulation Results ........................................................68
3.4.3. Effect of Luggage on Fuselage Deformation, Energy Dissipation, and
Acceleration-Time Histories ..................................................................................73
3.5. Concluding Remarks ........................................................................................77
Chapter 4: Application of an Energy Absorbing Device to the Boeing 737 Fuselage
Section ..............................................................................................................................79
4.1. Introduction ......................................................................................................79
4.2. Model Setup .....................................................................................................80
4.3. Simulation Results ...........................................................................................82
4.4. Concluding Remarks ........................................................................................85
Chapter 5: An Experimental Study on the Effect of Failure Trigger Mechanisms on the
Energy Absorption Capability of CFRP Tubes under Axial Compression .......................87
5.1. Abstract ............................................................................................................87
5.2. Introduction ......................................................................................................88
5.3. Experimental Setup ..........................................................................................92
5.3.1. Specimen Fabrication..............................................................................92
5.3.2. Failure Trigger Mechanisms ...................................................................92
5.3.3. Test Setup and Testing Procedure...........................................................93
5.3.4. Specific Energy Absorption ....................................................................95
5.4. Experimental Results .......................................................................................96
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5.4.1. Load-Displacement Behavior of Group A Specimens............................96
5.4.2. Load-Displacement Behavior of Group B Specimens ..........................102
5.4.3. Failure Process ......................................................................................105
5.4.4. Strain Fields ..........................................................................................111
5.5. Conclusions ....................................................................................................114
Chapter 6: Experimental Investigation on the Energy Absorption Capacity During
Crushing of Axially Loaded Thin-Walled Gr/Ep Members ............................................116
6.1. Abstract ..........................................................................................................116
6.2. Introduction ....................................................................................................116
6.3. Experimental Procedure .................................................................................120
6.3.1. Specimen Fabrication............................................................................120
6.3.2. Failure Triggering Mechanisms ............................................................120
6.3.3. Test Setup and Testing Procedure.........................................................121
6.3.4. Specific Energy Absorption ..................................................................122
6.4. Experimental Results .....................................................................................123
6.4.1. Load-Crosshead Displacement .............................................................123
6.4.2. The Failure Process ...............................................................................125
6.5. Effect of Cross-Sectional Geometry on SEA.................................................138
6.6. Conclusion .....................................................................................................141
Chapter 7: Modeling Methodologies for Simulating the Axial Crushing Behavior of
CFRP Members ................................................................................................................143
7.1. Abstract ..........................................................................................................143
7.2. Introduction ....................................................................................................143
7.3. Specimen Configuration and Test Procedure ................................................147
7.4. Single-layer modeling approach ....................................................................149
7.4.1. Laminate Representation and Element Selection .................................149
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7.4.2. Material Model......................................................................................150
7.4.3. Boundary Conditions and Contact Definitions .....................................151
7.4.4. Simulation Results ................................................................................153
7.5. Multi-Layer Modeling Approach ...................................................................159
7.5.1. Laminate Representation ......................................................................159
7.5.2. Element Size and Formulation ..............................................................160
7.5.3. Boundary Conditions and Contact Definitions .....................................161
7.5.4. Time Step ..............................................................................................162
7.5.5. Delamination Interface..........................................................................164
7.5.6. Material Model......................................................................................169
7.5.7. Discussion of Results ............................................................................172
7.6. Concluding Remarks ......................................................................................177
Chapter 8: Finite Element Modeling of the Crushing Behavior of Thin-Walled CFRP
Tubes under Axial Compression ......................................................................................180
8.1. Abstract ..........................................................................................................180
8.2. Introduction ....................................................................................................180
8.3. Summary of Experimental Work ...................................................................184
8.3.1. Test Setup and Procedure ......................................................................184
8.3.2. Experimental Results ............................................................................184
8.4. Numerical Simulations...................................................................................186
8.4.1. Model Setup ..........................................................................................186
8.4.2. Delamination Interface..........................................................................187
8.4.3. Boundary Conditions and Contact Definitions .....................................190
8.4.4. Material Model......................................................................................191
8.5. Simulation Results .........................................................................................192
8.5.1. Deformation ..........................................................................................192
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8.5.2. Load-Crosshead Displacement Behavior ..............................................195
8.5.3. Strain Fields ..........................................................................................198
8.6. Concluding Remarks ......................................................................................199
Chapter 9: Finite Element Modeling of the Crushing Behavior of Thin-Walled Open
Cross-Section CFRP Members under Axial Compression ..............................................201
9.1. Abstract ..........................................................................................................201
9.2. Introduction ....................................................................................................201
9.3. Summary of Experimental Work ...................................................................205
9.3.1. Test Setup and Procedure ......................................................................205
9.3.2. Experimental Results ............................................................................207
9.4. Numerical Simulations...................................................................................208
9.4.1. Model Setup ..........................................................................................209
9.4.2. Delamination Interface..........................................................................210
9.4.3. Boundary Conditions and Contact Definitions .....................................213
9.4.4. Material Model......................................................................................214
9.5. Simulation Results .........................................................................................215
9.5.1. Deformation ..........................................................................................215
9.5.2. Load-Crosshead Displacement Behavior ..............................................220
9.5.3. Strain Fields ..........................................................................................225
9.6. Concluding Remarks ......................................................................................227
Chapter 10: Summary, Conclusions and Recommendations ...........................................229
10.1. Crashworthiness Study...................................................................................229
10.1.1. Key Conclusions ...................................................................................230
10.1.2. Scientific Contributions ........................................................................232
10.2. Energy Absorbing Structures: Experimental Study .......................................232
10.2.1. Key Conclusions ...................................................................................233