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Opportunities in Protection Materials Science
and Technology for Future Army Applications
Committee on Opportunities in Protection Materials Science
and Technology for Future Army Applications
National Materials Advisory Board
and
Board on Army Science and Technology
Division on Engineering and Physical Sciences
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THE NATIONAL ACADEMIES PRESS 500 Fifth Street, N.W. Washington, DC 20001
NOTICE: The project that is the subject of this report was approved by the Governing Board of the National
Research Council, whose members are drawn from the councils of the National Academy of Sciences, the
National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible
for the report were chosen for their special competences and with regard for appropriate balance.
This study was supported by Contract No. W911NF-09-C-0164 between the National Academy of Sciences
and the Department of Defense. Any opinions, findings, conclusions, or recommendations expressed in this
publication are those of the authors and do not necessarily reflect the views of the organizations or agencies
that provided support for the project.
International Standard Book Number-13: 978-0-309-21285-4
International Standard Book Number-10: 0-309-21285-5
This report is available in limited quantities from
National Materials and Manufacturing Board
500 Fifth Street, N.W.
Washington, DC 20001
nmab@nas.edu
http://www.nationalacademies.edu/nmab
Additional copies of this report are available from the National Academies Press, 500 Fifth Street, N.W.,
Lockbox 285, Washington, DC 20055; (800) 624-6242 or (202) 334-3313 (in the Washington metropolitan
area); Internet: http://www.nap.edu.
Cover: A soldier wearing protective equipment (left); up-armored high-mobility multipurpose wheeled vehicle
(HMMWV) (center); drawing showing penetration of target (right, upper) and interface defeat—the goal of
protective material (right, lower). The lower border serves as a reminder of the continued increase in threat
that drives the need for advances in protective materials.
Copyright 2011 by the National Academy of Sciences. All rights reserved.
Printed in the United States of America
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The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars
engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to
their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the
Academy has a mandate that requires it to advise the federal government on scientific and technical matters.
Dr. Ralph J. Cicerone is president of the National Academy of Sciences.
The National Academy of Engineering was established in 1964, under the charter of the National Academy
of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in
the selection of its members, sharing with the National Academy of Sciences the responsibility for advising
the federal government. The National Academy of Engineering also sponsors engineering programs aimed
at meeting national needs, encourages education and research, and recognizes the superior achievements of
engineers. Dr. Charles M. Vest is president of the National Academy of Engineering.
The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services
of eminent members of appropriate professions in the examination of policy matters pertaining to the health
of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its
congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues
of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine.
The National Research Council was organized by the National Academy of Sciences in 1916 to associate the
broad community of science and technology with the Academy’s purposes of furthering knowledge and advis -
ing the federal government. Functioning in accordance with general policies determined by the Academy, the
Council has become the principal operating agency of both the National Academy of Sciences and the National
Academy of Engineering in providing services to the government, the public, and the scientific and engineering
communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph
J. Cicerone and Dr. Charles M. Vest are chair and vice chair, respectively, of the National Research Council.
www.national-academies.org
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COMMITTEE ON OPPORTUNITIES IN PROTECTION MATERIALS SCIENCE
AND TECHNOLOGY FOR FUTURE ARMY APPLICATIONS
EDWIN L. THOMAS, Chair, Massachusetts Institute of Technology
MICHAEL F. McGRATH, Vice Chair, Analytic Services Inc. (ANSER)
RELVA C. BUCHANAN, University of Cincinnati
BHANUMATHI CHELLURI, IAP Research, Inc.
RICHARD A. HABER, Rutgers University
JOHN WOODSIDE HUTCHINSON, Harvard University
GORDON R. JOHNSON, Southwest Research Institute
SATISH KUMAR, Georgia Institute of Technology
ROBERT M. McMEEKING, University of California, Santa Barbara
NINA A. ORLOVSKAYA, University of Central Florida
MICHAEL ORTIZ, California Institute of Technology
RAÚL A. RADOVITZKY, Massachusetts Institute of Technology
KALIAT T. RAMESH, Johns Hopkins University
DONALD A. SHOCKEY, SRI International
SAMUEL ROBERT SKAGGS, Los Alamos National Laboratory (retired), Consultant
STEVEN G. WAX, Defense Applied Research Projects Agency (retired), Consultant
Staff
ERIK SVEDBERG, NMAB Senior Program Officer
ROBERT LOVE, BAST Senior Program Officer
NANCY T. SCHULTE, BAST Senior Program Officer
HARRISON T. PANNELLA, BAST Senior Program Officer
JAMES C. MYSKA, BAST Senior Research Associate
NIA D. JOHNSON, BAST Senior Research Associate
LAURA TOTH, NMAB Senior Program Assistant
RICKY D. WASHINGTON, NMAB Administrative Coordinator
ANN F. LARROW, BAST Research Assistant
v
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NATIONAL MATERIALS ADVISORY BOARD
ROBERT H. LATIFF, Chair, R. Latiff Associates
LYLE H. SCHWARTZ, Vice Chair, University of Maryland
PETER R. BRIDENBAUGH, Alcoa, Inc. (retired)
L. CATHERINE BRINSON, Northwestern University
VALERIE BROWNING, ValTech Solutions, LLC
YET MING CHIANG, Massachusetts Institute of Technology
GEORGE T. GRAY III, Los Alamos National Laboratory
SOSSINA M. HAILE, California Institute of Technology
CAROL A. HANDWERKER, Purdue University
ELIZABETH HOLM, Sandia National Laboratories
DAVID W. JOHNSON, JR., Stevens Institute of Technology
TOM KING, Oak Ridge National Laboratory
KENNETH H. SANDHAGE, Georgia Institute of Technology
ROBERT E. SCHAFRIK, GE Aircraft Engines
STEVEN G. WAX, Strategic Analysis, Inc.
Staff
DENNIS CHAMOT, Acting Director
ERIK SVEDBERG, Senior Program Officer
RICKY D. WASHINGTON, Administrative Coordinator
HEATHER LOZOWSKI, Financial Associate
LAURA TOTH, Senior Program Assistant
NOTE: In January 2011 the National Materials Advisory Board (NMAB) and the Board on Manufacturing and Engineering
Design combined to form the National Materials and Manufacturing Board. Listed here are the members of the NMAB who
were involved in this study.
vi
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BOARD ON ARMY SCIENCE AND TECHNOLOGY
ALAN H. EPSTEIN, Chair, Pratt & Whitney, East Hartford, Connecticut
DAVID M. MADDOX, Vice Chair, Independent Consultant, Arlington, Virginia
DUANE ADAMS, Carnegie Mellon University (retired), Arlington, Virginia
ILESANMI ADESIDA, University of Illinois at Urbana-Champaign
RAJ AGGARWAL, University of Iowa, Coralville
EDWARD C. BRADY, Strategic Perspectives, Inc., Fort Lauderdale, Florida
L. REGINALD BROTHERS, BAE Systems, Arlington, Virginia
JAMES CARAFANO, The Heritage Foundation, Washington, D.C.
W. PETER CHERRY, Independent Consultant, Ann Arbor, Michigan
EARL H. DOWELL, Duke University, Durham, North Carolina
RONALD P. FUCHS, Independent Consultant, Seattle, Washington
W. HARVEY GRAY, Independent Consultant, Oak Ridge, Tennessee
CARL GUERRERI, Electronic Warfare Associates, Inc., Herndon, Virginia
JOHN J. HAMMOND, Lockheed Martin Corporation (retired), Fairfax, Virginia
RANDALL W. HILL, JR., University of Southern California Institute for Creative Technologies,
Marina del Rey
MARY JANE IRWIN, Pennsylvania State University, University Park
ROBIN L. KEESEE, Independent Consultant, Fairfax, Virginia
ELLIOT D. KIEFF, Channing Laboratory, Harvard University, Boston, Massachusetts
LARRY LEHOWICZ, Quantum Research International, Arlington, Virginia
WILLIAM L. MELVIN, Georgia Tech Research Institute, Smyrna
ROBIN MURPHY, Texas A&M University, College Station
SCOTT PARAZYNSKI, The Methodist Hospital Research Institute, Houston, Texas
RICHARD R. PAUL, Independent Consultant, Bellevue, Washington
JEAN D. REED, Independent Consultant, Arlington, Virginia
LEON E. SALOMON, Independent Consultant, Gulfport, Florida
JONATHAN M. SMITH, University of Pennsylvania, Philadelphia
MARK J.T. SMITH, Purdue University, West Lafayette, Indiana
MICHAEL A. STROSCIO, University of Illinois, Chicago
JOSEPH YAKOVAC, President, JVM LLC, Hampton, Virginia
Staff
BRUCE A. BRAUN, Director
CHRIS JONES, Financial Manager
DEANNA P. SPARGER, Program Administrative Coordinator
vii
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Preface
Armor materials are remarkable: Able to stop multiple Coincidentally, six weeks after the final committee
hits and save lives, they are essential to our military capa- meeting, the Army announced a draft program calling for
bility in the current conflicts. But as threats have increased, establishment of a collaborative research alliance for materi-
als in extreme dynamic environments.2 Since the committee
armor systems have become heavier, creating a huge burden
for the warfighter and even for combat vehicles. This study did not review the Army’s preliminary request for proposal,
of lightweight protection materials is the product of a com- it is not discussed in the study.
mittee created jointly by two boards of the National Research The committee was composed of a wide range of experts
Council, the National Materials Advisory Board (NMAB)1 whose backgrounds in processing and characterization of ce-
and the Board on Army Science and Technology (BAST), ramics, metals, polymers, and composites, as well as theory
in response to a joint request from the Assistant Secretary and modeling and high-rate testing of protection materials,
of the Army for Acquisition, Logistics, and Technology and combined wonderfully to make this report possible. I want
the Army Research Laboratory. The committee examined to thank each and every one of the committee members for
the fundamental nature of material deformation behavior at their hard work, camaraderie, and dedicated efforts over the
the very high rates characteristic of ballistic and blast events. past year and in particular, Mike McGrath, the vice chair,
Our goal was to uncover opportunities for development of and chapter leads Richard Haber, John Hutchinson, Nina
advanced materials that are custom designed for use in armor Orlovskaya, Don Shockey, Bob Skaggs, Raúl Radovitzky,
systems, which in turn are designed to make optimal use of and Steve Wax. Staff of the NMAB and the BAST did a great
the new materials. Such advances could shorten the time job supporting the study and in bringing the report to fruition.
for material development and qualification, greatly speed
engineering implementation, drive down the areal density Edwin L. Thomas, NAE, Chair
of armor, and thereby offer significant advantages for the Committee on Opportunities in
U.S. military. We hope this report will have a revolutionary Protection Materials
effect on the materials and armor systems of the future—an Science and Technology for
effect that will meet mission needs and save even more lives. Future Army Applications
2U.S. Army. 2010. A Collaborative Research Alliance (CRA) for Ma -
1In January 2011 the National Materials Advisory Board (NMAB) and
terials in Extreme Dynamic Environments (MEDE), Solicitation Number
the Board on Manufacturing and Engineering Design combined to form
W911NF-11-R-0001, October 28. Available online at https://www.fbo.gov/
the National Materials and Manufacturing Board. The move underscored
index?s=opportunity&mode=form&id=48a13a80653b1fabe3f83ede9ddc64
the importance of materials science to innovations in engineering and
1b&tab=core&tabmode=list&=. Last accessed March 31, 2011.
manufacturing.
ix
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Acknowledgment of Reviewers
This report has been reviewed in draft form by indi- Wayne E. Marsh, DuPont Central Research and
viduals chosen for their diverse perspectives and technical Development,
expertise, in accordance with procedures approved by the R. Byron Pipes, Purdue University,
National Research Council’s (NRC’s) Report Review Com- Bhakta B. Rath, Naval Research Laboratory,
mittee. The purpose of this independent review is to provide Susan Sinnott, University of Florida, and
candid and critical comments that will assist the institution Edgar Arlin Starke, Jr., University of Virginia
in making its published report as sound as possible and to
ensure that the report meets institutional standards for objec- Although the reviewers listed above have provided
tivity, evidence, and responsiveness to the study charge. The many constructive comments and suggestions, they were not
review comments and draft manuscript remain confidential asked to endorse the conclusions or recommendations nor
to protect the integrity of the deliberative process. We wish to did they see the final draft of the report before its release. The
thank the following individuals for their review of this report: review of this report was overseen by Elisabeth M. Drake,
NAE, Massachusetts Institute of Technology Laboratory of
Charles E. Anderson, Jr., Southwest Research Energy and the Environment. Appointed by the National Re-
Institute, search Council, she was responsible for making certain that
Diran Apelian, Worcester Polytechnic Institute, an independent examination of this report was carried out in
Morris E. Fine, Technological Institute Professor accordance with institutional procedures and that all review
Emeritus, Northwestern University comments were carefully considered. Responsibility for the
Peter F. Green, University of Michigan, final content of this report rests entirely with the authoring
Julia R. Greer, California Institute of Technology, committee and the institution.
x
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Contents
SUMMARY 1
1 OVERVIEW 7
Introduction, 7
The Challenge, 7
Scope of the Study, 9
Statement of Task, 9
Study Methodology, 9
Report Organization, 9
Other Issues, 10
Overarching Recommendation, 10
2 FUNDAMENTALS OF LIGHTWEIGHT ARMOR SYSTEMS 12
Armor System Performance and Testing in General, 12
Definition of Armor Performance, 12
Testing of Armor Systems, 13
Exemplary Threats and Armor Designs, 14
Personnel Protection, 14
Threat, 14
Design Considerations for Fielded Systems, 15
Vehicle Armor, 18
Threat, 18
Design Considerations for Fielded Systems, 18
Transparent Armor, 20
Threat, 20
Design Considerations for Fielded Systems, 21
From Armor Systems to Protection Materials, 21
Existing Paradigm, 21
Security and Export Controls, 23
3 MECHANISMS OF PENETRATION IN PROTECTIVE MATERIALS 24
Penetration Mechanisms in Metals and Alloys, 25
Penetration Mechanisms in Ceramics and Glasses, 26
Penetration Mechanisms in Polymeric Materials, 28
Failure Mechanisms in Cellular-Sandwich Materials Due to Blasts, 29
Conclusions, 32
xi
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xii CONTENTS
4 INTEGRATED COMPUTATIONAL AND EXPERIMENTAL METHODS FOR THE 35
DESIGN OF PROTECTION MATERIAL AND PROTECTION SYSTEMS:
CURRENT STATUS AND FUTURE OPPORTUNITIES
Three Examples of Current Capabilities for Modeling and Testing, 36
Projectile Penetration of High-Strength Aluminum Plates, 36
Projectile Penetration of Bilayer Ceramic-Metal Plates, 38
All-Steel Sandwich Plates for Enhanced Blast Protection: Design, Simulation,
and Testing, 40
The State of the Art in Experimental Methods, 43
Definition of the Length Scales and Timescales of Interest, 43
Evaluating Material Behavior at High Strain Rates, 45
Investigating Shock Physics, 47
Investigating Dynamic Failure Processes, 49
Investigating Impact Phenomenology, 50
Modeling and Simulation Tools, 51
Background and State of the Art, 52
New Protection Materials and Material Systems: Opportunities and Challenges, 65
Computational Materials Methods, 65
Overall Recommendations, 68
5 LIGHTWEIGHT PROTECTIVE MATERIALS: CERAMICS, 69
POLYMERS, AND METALS
Overview and Introduction, 69
Ceramic Armor Materials, 70
Crystalline Ceramics: Phase Behavior, Grain Size or Morphology, and Grain Boundary
Phases, 72
Crystalline Structure of Silicon Carbide, 75
Availability of Ceramic Powders, 77
Processing and Fabrication Techniques for Armor Ceramics, 78
“Green” Compaction, 78
Sintering, 79
Transparent Armor, 80
Transparent Crystalline Ceramics, 81
Fibers, 82
Effect of Fiber Diameter on Strength in High-Performance Fibers, 84
Relating Tensile Properties to Ballistic Performance, 84
Approaching the Theoretical Tensile Strength and Theoretical Tensile Modulus, 84
The Need for Mechanical Tests at High Strain Rates, 85
Ballistic Fabrics, 86
Ballistic Testing and Experimental Work on Fabrics, 86
Failure Mechanisms of Fabrics, 87
Important Issues for Ballistic Performance of Fabrics, 87
Metals and Metal-Matrix Composites, 89
Desirable Attributes of Metals as Protective Materials, 90
Nonferrous Metal Alternatives, 91
Adhesives for Armor and for Transparent Armor, 92
General Considerations for the Selection of an Adhesive Interlayer, 92
Important Issues Surrounding Adhesives for Lightweight Armor Applications, 92
Types of Adhesive Interlayers, 94
Testing, Simulation, and Modeling of Adhesives, 94
Joining, 95
Other Issues in Lightweight Materials, 96
Nondestructive Evaluation Techniques, 96
Fiber-Reinforced Polymer Matrix Composites, 97
Overall Findings, 97
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xiii
CONTENTS
6 THE PATH FORWARD 99
A New Paradigm, 99
Recommendations for Protection Materials by Design, 102
Element 1—Fundamental Understanding of Mechanisms of Deformation and
Failure Due to Ballistic and Blast Threats, 102
Element 2—Advanced Computational and Experimental Methods, 102
Element 3—Development of New Materials and Material Systems, 103
Element 4—Organizational Approach, 104
Critical Success Factors for the Recommended New Organizations, 105
DoD Center for the PMD Initiative, 105
Open PMD Collaboration Center, 106
Time Frame for Anticipated Advances, 107
APPENDIXES
A Background and Statement of Task 111
B Biographical Sketches of Committee Members 113
C Committee Meetings 119
D Improving Powder Production 121
E Processing Techniques and Available Classes of Armor Ceramics 125
F High-Performance Fibers 136
G Failure Mechanisms of Ballistic Fabrics and Concepts for Improvement 139
H Metals as Lightweight Protection Materials 142
I Nondestructive Evaluation for Armor 148
J Fiber-Reinforced Polymer Matrix Composites 150
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Tables, Figures, and Boxes
TABLES
2-1 National Institute of Justice (NIJ) Ballistic Threat Standards, 14
2-2 Metallic Armor Materials, 19
4-1 Mode or Method, Required Input, Expected Output, and Typical Software Used in
Materials Science and Engineering, 67
5-1 Manufacturing Processes for Opaque Ceramic Armor Materials, 80
5-2 Typical Properties of Selected Fibers, 83
E-1 Summary of Properties of Various Ceramics for Personnel Armor Application, 126
E-2 Tensile Mechanical Properties of Spider Silks and Other Materials, 132
FIGURES
S-1 New paradigm for armor development, 3
S-2 PMD initiative organizational structure involving academic researchers, government
laboratories, and industry, 5
1-1 A soldier wearing protective equipment, 7
1-2 Up-armored high-mobility multipurpose wheeled vehicle (HMMWV, or Humvee), 8
1-3 Areal density of armor versus time, demonstrating that new lightweight materials such as
titanium, aluminum, and ceramics have provided increased protection at a lower weight
per unit area over time, 8
2-1 Partial and complete ballistic penetration, 13
2-2 Indoor firing ranges, 15
2-3 Examples of 7.62 mm (.30 cal) small arms projectiles, 15
2-4 Increase in ballistic performance as a function of improved fibers, 16
2-5 Interceptor body armor, 17
2-6 Effect of a ballistic threat on performance, 17
2-7 Examples of Army combat vehicles, 19
2-8 Examples of vehicle protection, 20
2-9 Schematic of vehicle armor protection system, 21
2-10 Example of transparent armor for a vehicle window, 22
2-11 Current paradigm for armor design, 22
xv
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xvi TABLES, FIGURES, AND BOXES
3-1 Impact on steel plate, 25
3-2 Polished and etched cross section through the crater in a steel plate that was impacted at
6 km/s by a 12.7-mm-diameter polycarbonate sphere, 26
3-3 Polished cross sections through the shot line of a SiC and a TiB2 target, showing typical
microdamage immediately below the impact site after a no-penetration experiment with a
long rod tungsten projectile, 26
3-4 Damage mechanisms observed in several ceramics, 27
A 200 × 200 × 75 mm3 monolithic soda lime glass target (confined on all sides with
3-5
polymethyl methacrylate plates) partially penetrated by a 31.75 × 6.35-mm-diameter
heminosed steel rod impacting at 300 m/s and a surface of section through the shot line
showing damage around the projectile cavity, 28
3-6 Three material processing zones and three stress states experienced by a material element
in the path of an advancing penetrator, 29
3-7 Post-test observation of fabric damage from a platelike projectile showing yarn breakage
characteristics; projectile size is shown with the fabric flap in its original position, 30
3-8 SEM micrograph revealing fibrillar microstructure in an as-spun PBZT fiber, 30
3-9 SEM side views and end-on views of matching fracture ends of a tensile-fractured PBZT
fiber, 31
3-10 Sequence of computerized axial tomography scan images showing macro deformation
bands in quasi-static compression-loaded ductile aluminum foam, 32
3-11 Sequential mechanisms responsible for cell collapse in ductile aluminum foam under
quasi-static load, 32
3-12 Stress-strain curve for a brittle aluminum foam subjected to quasi-static compression;
bands of fractured cells after imposed quasi-static engineering compressive strains of 0,
5.6 percent, 11.7 percent, 33.3 percent, and 60 percent, respectively, 32
3-13 SEM images of failed cells in brittle aluminum foam showing failure modes under
compression, tension and shear, face cracking, and friction and shear between fractured
cells, 33
4-1 Blunt-nosed and ogive-nosed projectiles exiting a 20-mm-thick aluminum plate, 37
4-2 Experimental results for final exit (residual) velocity as a function of initial velocity for
blunt-nosed and ogive-nosed projectiles, 37
4-3 Numerical finite-element simulations of the ballistic behavior shown in Figure 4.2
depicting effects of mesh refinement and the contrast between three-dimensional and two-
dimensional (axisymmetric) meshing, 37
4-4 Simulations of penetration of a plate of AA7057-T651 showing finite-element mesh for a
blunt-nosed and an ogive-nosed hard steel projectile, 38
4-5 Ceramic strength versus applied pressure for the JHB constitutive model, 39
4-6 Schematic depicting the response of a clamped sandwich plate to blast loading, 43
4-7 Half-sectional square honeycomb core test panels, 43
4-8 Comparison of experimental test specimens deformed at the three levels of air blast, with
simulations carried out for the same plates and level of blasts, 43
4-9 Length scales and timescales associated with typical threats to Army fielded materials and
structures, 44
4-10 Experimental techniques used for the development of controlled high-strain-rate
deformations in materials, 45
4-11 High-strain-rate behavior of 6061-T6 aluminum determined through servohydraulic
testing, compression and torsional Kolsky bars, and high-strain-rate, pressure-shear plate
impact, 46
4-12 Schematic of the high-strain-rate, pressure-shear plate impact experiment, 47
4-13 Photographs taken by a high-speed camera (interframe times of 1 μs and exposure times
of 100 ns) of the dynamic failure process in uncoated transparent AlON, 50
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xvii
TABLES, FIGURES, AND BOXES
4-14 Line VISAR figure showing spallation in polycrystalline tantalum, 51
4-15 Optimal transportation mesh-free simulation of a steel plate perforated by a steel
projectile striking at various angles, 55
4-16 Example of a Lagrangian finite-element simulation that uses adaptive re-meshing and
refinement to eliminate element distortion and to optimize the mesh, 56
4-17 A comparison of results from five computational approaches for a tungsten projectile
impacting a steel target at 1,615 m/s, 56
4-18 Prediction of conical, radial, and lateral crack patterns in ceramic plate impact by the
recent cohesive zone/discontinuous Galerkin method, 58
4-19 Multiscale hierarchy for metal plasticity, 61
4-20 V&V process, 63
4-21 Growth in supercomputer powers as a function of year, 64
5-1 Schematic presentation of the cross section of an armor tile typically used for armored
vehicles showing the complexity of the armor architecture, 69
5-2 Rhombohedral unit cell structure of B4C showing B11C icosahedra and the diagonal chain
of C-B-C atoms, 72
5-3 The boron-carbon phase diagram over the range 0-36 at % carbon, 73
5-4 A boron carbide ballistic target that comminuted during impact and a high-resolution
TEM image of a fragment produced by a ballistic test at impact pressure of 23.3 GPa, 74
5-5 Schematics of the stacking sequence of layers of Si–C tetrahedra in various SiC
polytypes, 76
5-6 Scanning TEM micrograph of the microstructure of spinel glass ceramic, 80
5-7 Photo showing the transparency and multi-hit performance of spinel, 82
5-8 Strength and stiffness of the strongest fiber sample and of fibers typical of the high-
strength and low-strength peaks in the 1-mm gauge length distribution versus the
properties of other commercially available, high-performance fibers, 83
5-9 Schematic of transverse sections of fibers, 84
5-10 Stress-strain curve for RHA steel deformed in compression at a high strain rate, 90
5-11 Composite stack of transparent layers: a ceramic strike face, adhesive interlayers, glass,
polyurethane, and polycarbonate, 93
6-1 Current paradigm for armor design, 99
6-2 New paradigm for armor development, 100
6-3 PMD initiative organizational structure involving academic researchers, government
laboratories, and industry, 104
E-1 Silicon carbide sample microstructures showing grains in hot-pressing, dynamic magnetic
compaction followed by pressureless sintering, and uniaxial pressing followed by
pressureless sintering, 128
H-1 Specific stiffness versus specific strength of various materials, including metals and
ceramics, 143
H-2 High-strain-rate compressive response of a trimodal aluminum alloy, in comparison with
that of rolled homogeneous armor at similar strain rates (103 s–1), 144
H-3 Optical micrograph of Al-SiC cermet, 145
J-1 Cone formation during ballistic impact on the back face of the composite target, 151
J-2 Schematic shape of delaminated regions observed in impact experiments, 152
J-3 Schematic showing plug formation, 152
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xviii TABLES, FIGURES, AND BOXES
BOXES
2-1 Composition of Rolled Homogeneous Armor [L] (MIL-DTL-12560), 12
2-2 Construction of the Advanced Combat Helmet, 18
2-3 Shaped Charge Characteristics, 19
3-1 Microstructural Options for Influencing Failure Mechanisms in Metals, Ceramics, and
Polymers, 24
5-1 Processing of Ceramic Powders, 78
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Acronyms and Abbreviations
AlON aluminum oxynitride ICME Integrated Computational Materials
ARL Army Research Laboratory Engineering (an NRC report)
ARO Army Research Office ITAR International Traffic in Arms Regulations
ATC Aberdeen Test Center (Maryland)
ATH aluminum trihydroxide JHB Johnson, Holmquist, and Beissel
ATPD Army Tank Purchase Description
M&S modeling and simulation
BAST Board on Army Science and Technology MMC metal matrix composites
MPa megapascal
CIP cold isostatic pressing MZ Mescall zone
CNT carbon nanotubes
CTE coefficient of thermal expansion NDE nondestructive evaluation
CZM cohesive zone models NIJ National Institute of Justice
NMAB National Materials Advisory Board
DARPA Defense Advanced Projects Research NRC National Research Council
Agency NSF National Science Foundation
DMC dynamic magnetic compaction NVI normal velocity interferometer
DoD Department of Defense
DoE Department of Energy OHPC Omnipresent High-Performance Computing
program
ERDC Engineer Research and Development Center
(U.S. Army) PAN polyacrylonitrile
ESAPI enhanced small arms protective insert PBO polybenzoxazole
PBZT poly(benzobisthiazole)
FGAC functionally graded armor composites PC polycarbonate
FGM functionally gradient material PE polyethylene
FSP fragment simulating projectiles PMC polymer matrix composite
PMD protection materials-by-design
GHz gigahertz PMMA polymethyl methacrylate
GPa gigapascals PPTA polyparaphenylene terephthalamide
PU polyurethane
HEL Hugoniot elastic limit PVB polyvinyl butyral
HMMWV high-mobility multipurpose wheeled vehicle
(Humvee) QMU quantification of margins and uncertainties
HP hot pressing
RHA rolled homogeneous armor
IBA Interceptor body armor
xix
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xx ACRONYMS AND ABBREVIATIONS
SAN poly(styrene-co-acrylonitrile) TPU thermoplastic polyurethanes
SAPI small arms protective insert
SCS shear compression (test) UHMWPE ultrahigh molecular weight polyethylene
SEM scanning electron microscope UQ uncertainty quantification
SiC silicon carbide UV ultraviolet
SiSiC siliconized silicon carbide
SPS spark plasma sintering VISAR velocity interferometry system for any reflector
V&V verification and validation
TDI transverse displacement interferometer
TEM transmission electron microscopy XCT x-ray computed tomography
