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Summary
This report responds to a request by the Assistant Sec- • Penetration mechanisms in metals and alloys, ceram-
retary of the Army (Acquisition, Logistics, and Technology) ics and glasses, and polymeric materials (Chapter 3).
to the National Research Council (NRC) to examine the cur- • Failure mechanisms in cellular-sandwich materials
rent theoretical and experimental understanding of the key due to blast (Chapter 3).
issues surrounding protection materials, identify the major • Current capabilities for modeling and simulation of
challenges and technical gaps for developing the future gen- protection materials and material systems on scales
eration of lightweight protection materials, and recommend ranging from the atomic to the macroscopic, includ-
a path forward for their development. While underscoring ing a discussion of state-of-the-art modeling and
the paramount need for lightweight materials, the charge simulation tools (Chapter 4).
included requirements to consider multiscale shockwave • The state of the art in experimental methods, includ-
energy transfer mechanisms and experimental approaches ing defining the length and timescales of interest,
for their characterization over short timescales, as well as evaluating material behavior at the relevant high-
multiscale modeling techniques to predict mechanisms for strain rates, and investigating shock physics, dy-
dissipating energy. namic failure processes, and impact phenomenology
Accordingly, two NRC boards—the National Materi- (Chapter 4).
als Advisory Board1 and the Board on Army Science and • Ceramic armor materials, including crystalline and
Technology—established the Committee on Opportunities amorphous ceramics, ceramic powders, processing
in Protection Materials Science and Technology for Future and fabrication techniques, and transparent crystal-
Army Applications to investigate opportunities in protection line ceramics (Chapter 5).
materials science and technology for the Army. What follows • Fibers, including the effect of fiber diameter on
is the evaluation developed by that committee. strength in high-performance fibers, microstruc-
The report considers exemplary threats and design phi- tural advances to approach the theoretical maximum
losophy for the three key applications of armor systems: (1) t ensile strength and modulus, and the need for
personnel protection, including body armor and helmets, (2) mechanical tests at high strain rates and pressures
vehicle armor, and (3) transparent armor. For each of these (Chapter 5).
applications, specific constraints drive the armor design and • Ballistic fabrics, including ballistic testing, failure
thus the ultimate choice of protection materials. mechanisms, and interactions among fibers and
In developing its recommendations, the committee among yarns during loading (Chapter 5).
assessed current knowledge and gaps in that knowledge • Metals and metal-matrix composites and their desir-
as it sought to prioritize the various types of lightweight able attributes, especially those of low-density metals
protective materials and armor systems for future research. such as magnesium alloys (Chapter 5).
Key areas and research challenges for protection materials • Fabrication and assembly of armor systems, with
discussed in these pages include the following: an emphasis on adhesives for armor and transparent
armor, including (1) general considerations for se-
lecting an adhesive interlayer and (2) testing, simula-
1In January 2011 the National Materials Advisory Board (NMAB) and
the Board on Manuacturing and Engineering Design combined to form tion, and modeling of adhesives and armor systems
the National Materials and Manufacturing Board. The move underscored (Chapter 5).
the importance of materials science to innovations in engineering and
manufacturing.
1
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2 OPPORTUNITIES IN PROTECTION MATERIALS SCIENCE AND TECHNOLOGY FOR FUTURE ARMY APPLICATIONS
NEW THREAT Material ..
Characteristics of Threat Material 2
Material 1
Armor Concept Select from Materials Research
(Geometry Available and Development/
Configuration) Materials Design
Fail
Characterization
Pass Make & Shoot
Ballistic Shoot or Canonical Microstructure
Evaluation Model Model Mechanisms
Make & Shoot Model
Fail
Rapid
Modeling and
Iterations
Select from
M&S
Pass Simulation
Available
Evaluation
Research and
Models/Codes
Development
Increased Fidelity
Characteristics of Armor Performance
NEW ARMOR
FIGURE S-1 New paradigm for armor development. The new design path for armor provides enhanced and closer coupling of the materials
research and development community and the modeling and simulation community, resulting in significantly reduced time for development
of new armor. This new approach connects the armor design process to the materials research and development community through canonical
models to deal with the restricted information problem. The elements of armor system design are not themselves new, but the emphasis shifts
from design-make-shoot-redesign to rapid simulation iterations, and from designing with off-the-shelf materials to designing that exploits
materials for their protective properties. The feedback loop between armor system design and material design contrasts with current practice,
in which a one-way flow puts new materials on the shelf to be tried in the make-shoot-look process.
is accomplished through canonical models that translate
Findings and recommendations pertaining to these areas
armor system requirements (often data with restricted ac-
and research challenges appear in Chapters 3 through 5.
cess) into characterizations, microstructures, behaviors, and
The single overarching recommendation is repeated here in
deformation mechanisms that an open research community
the summary, along with the four key recommendations in
can use in designing new lightweight protection materials.
the main text.
The principal objective of this new paradigm is to enable
the design of superior protection materials and to accelerate
OVERARCHING RECOMMENDATION
their implementation in armor systems. This new paradigm
will build upon the multidisciplinary collaboration concepts
The conclusion of this study is that the ability to design
and lessons from other applications documented in the report
and optimize protection material systems can be acceler-
Integrated Computational Materials Engineering.2 It can be
ated and made more cost effective by operating in a new
focused on the most promising opportunities in lightweight
paradigm of lightweight protection material development
protection materials, bringing such current products as ce-
(Figure S-1). In this new paradigm, the current armor
ramic plates and polymer fiber materials well beyond their
system design practice, which relies heavily on a design-
make-shoot iterative process, is replaced by rapid iterations
of modeling and simulation, with ballistic evaluation used
2NRC. 2008. Integrated Computational Systems Engineering: A Trans -
selectively to verify satisfactory designs. Strong coupling
formational Discipline for Improved Competitiveness and National Secu-
with the materials research and development community rity. Washington, D.C.: The National Academies Press.
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3
SUMMARY
present state of performance and opening the possibility for • Relating material performance to deformation and
radically new armor system solutions to be explored and failure mechanisms. Developing models and data for
optimized in tens of months rather than tens of years. choosing materials based on their ability to inhibit
or avoid failure mechanisms as opposed to choosing
Overarching Recommendation. Given the long-term im- them based on bulk properties as measured in quasi-
portance of lightweight protection materials to the Depart- static and dynamic tests.
ment of Defense (DoD) mission, DoD should establish a • Developing superior armor materials by identifying
defense initiative for protection materials by design (PMD), compositions, crystalline structures, and microstruc-
with associated funding lines for basic and applied research. tures that counteract observed failure mechanisms
Responsibility for this new initiative should be assigned to and by establishing processing routes to the synthesis
one of the Services, with participation by other DoD com- of these materials.
ponents whose missions also require advances in protection • Reducing the cost of production of protection mate-
materials. The PMD initiative should include a combination rials by improving the processes and yields and by
of computational, experimental, and materials testing, char- enhancing the ability to manufacture small lots.
acterization, and processing research conducted by govern-
ment, industry, and academia. The program director of the
Element 2—Advanced Computational and Experimental
initiative should be given the authority and resources to col-
Methods
laborate with the national laboratories and other institutions
in the use of unique facilities and capabilities and to invest The second element of the PMD initiative would be to
in DoD infrastructure where needed. advance and exploit the capabilities of the emerging compu-
This overarching recommendation requires actions in tational and experimental methods discussed in Chapter 4.
four important elements of the PMD initiative. The first objective is to predict the ballistic and blast per-
formance of candidate materials and materials systems as a
prelude to the armor design process. The second objective is
RECOMMENDATIONS
to define requirements that will guide the synthesis, process-
ing, fabrication, and evaluation of protection materials. The
Element 1—Fundamental Understanding of Mechanisms
PMD initiative would develop the next generation of
of Deformation and Failure Due to Ballistic and Blast
Threats
• DoD advanced protection codes that incorporate
The first element of the PMD initiative would be to de- experimentally validated, high-fidelity, physics-
velop better fundamental understanding of the mechanisms based models of material deformation and failure, as
of high-rate3 material deformation and failure in various well as the necessary high-performance computing
protection materials, discussed in Chapter 3. As part of the infrastructure;
new paradigm, armor development should be considered not • Experimental facilities and capabilities to assess and
from the viewpoint of conventional bulk material properties certify the performance of new protection materials
but from the viewpoint of mechanisms. The deeper funda- and system designs, as well as provide insight into
mental understanding could lead to the development of more fundamental material behaviors under relevant con-
failure-resistant material compositions, crystal structures, ditions with unprecedented simultaneous high spatial
and microstructures and to protective materials with better and temporal resolution; and
performance. Moreover, by identifying the operative mecha- • Collaborative infrastructure for encouraging direct
nisms and quantifying their activity, mathematical damage communication and improved cooperation between
models can be written that may allow computational armor modelers and experimenters, through both (1) the
design. Chapter 3 discusses failure mechanisms for the sev- establishment of collaborative environments and (2)
eral classes of materials. requirements in proposals when the specific research
topic is well served by such collaboration.
Recommendation S-1/6-1. The Department of Defense
should establish a program of sustained investment in basic The high-priority opportunities identified in Chapter
and applied research that would facilitate a fundamental 4 will need sustained investment and program direction to
understanding of the mechanisms of deformation and failure advance computational and experimental capabilities. The
due to ballistic and blast events. This program should be es- envisioned computational capabilities must be developed
tablished under a director for protection materials by design, in partnership with a strong experimental effort that identi-
with particular emphasis on the following: fies the dynamic mechanisms of material behavior. These
mechanisms must be understood and modeled for the activity
to be successful, the material characteristics and properties
must be known for the simulations to be carried out, and the
3Ballistic velocities typically range from several hundred to several
outcomes of the computational modeling must be validated.
thousand meters per second and can lead to strain rates of up to 105 s–1.
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4 OPPORTUNITIES IN PROTECTION MATERIALS SCIENCE AND TECHNOLOGY FOR FUTURE ARMY APPLICATIONS
Recommendation S-2/6-2. The Department of Defense should designate a custodian for this database and
should establish a program of sustained investment in basic arrange for experimental results of the PMD program
and applied research in advanced computational and experi- to be provided to the database and shared with the
mental methods under the director of the protection materials research community. The database should include
by design (PMD) initiative, with particular emphasis on the ceramics, polymers, metals, glasses, and composite
following: materials in use today and should be expanded as new
materials are developed.
• Dynamic mechanism characterization. Identify and —Opaque and transparent ceramics and ceramic
characterize (1) the failure mechanisms underlying powders. The intrinsic properties of opaque and
damage to a material caused by projectiles from transparent ceramics and ceramic powders are
weapons and detonations and (2) the compositional not yet fully realized in armor systems. There is
and microstructural features of each constituent of need for understanding at the atomic, nano-, and
the material, as well as the material’s overall struc- micron levels of how powders and processing
ture. An enhanced experimental infrastructure will can be designed and manipulated to maximize
be needed to make progress in high-resolution (time the intrinsic benefits of dense ceramic armor and
and space) experiments on material deformation and reduce production costs.
failure characterization. —Polymeric, carbon, glass, and ceramic fibers.
• Code validation and verification. Focus on mul- There is an opportunity to develop finer diameter
tiscale, multiphysics material models, integrated and more ideally microstructured polymeric and
simulation/experimental protocols, prediction with carbon fibers with potentially a two- to fivefold
quantified uncertainties, and simulation-based quali- improvement in specific tensile strength over the
fication to help advance the predictive science for current state of the art. Such improvements would
protection systems. significantly reduce the weight of body armor.
• Challenges and canonical models. Periodically pro- —Polymers. In addition to polymer fibers, ther-
pose open challenges comprising design, simulation, moplastic and thermoset polymers are used as
and experimental validation that will convincingly monolithic components and also serve as matrixes
demonstrate the PMD. Each challenge problem must in various composites. Improved measurements of
address the corresponding canonical model and must and models for the deformation mechanisms and
result in quantifiable improvements in performance failure processes are needed for thermoplastic-
within that framework. and thermoset-based protection materials.
—Magnesium alloys. The very low density of
magnesium provides potential for the develop-
Element 3—Development of New Materials and Material
ment of very lightweight alternatives to tradi-
Systems
tional metallic materials in protection material
The third element of the PMD initiative is the develop- systems. The basic understanding of strengthening
ment and production of new materials and material systems mechanisms in magnesium should be advanced,
whose characteristics and performance can achieve the especially the development of ultra-fine-grained
behavior validated in modeling and simulation of the new magnesium alloys through severe plastic deforma-
armor system. The recommendations in this element target tion. Magnesium-based fibers are also worthy of
the most promising opportunities identified in Chapter 5. exploration.
• Adhesives and active brazing/soldering materi -
Recommendation S-3/6-3. The Department of Defense als. Development of adhesives and active brazing/
should establish a program of sustained investment in basic soldering materials and their processing methods
and applied research in advanced materials and processing, to match the elastic impedance of current materials
under the director of the PMD initiative program, with par- while minimizing the thermal stresses will improve
ticular emphasis on the following: the ballistic and blast performance of panels made of
bonded armor, including transparent armor.
• Test methods. Advances are needed in test methods
• A sustained effort to develop a database of high-
for determining the high strain rates (103 to 106 s–1)
strain-rate materials for armor. Material behavior
and dynamic properties must be measured and char- and dynamic failure processes of (especially) fibers,
acterized over the range of strains, strain rates, and polymers, and ceramics. Results should be passed
stress states in the context of penetration and blast on to the designated database of materials with high-
events. Develop a comprehensive database of materi- strain-rate behavior.
als that exhibit high-strain-rate behavior and consider • Material characterization. The characterization of,
them as materials of interest. The PMD director composition, crystalline structure, and microstruc-
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5
SUMMARY
the authority to direct funding and set PMD priorities. The
ture at appropriate length scales is a key task that
program will require committed funding to ensure long-term
will need more attention to take advantage of the
success and should be subject to periodic external reviews
improved experimental tools for quantifying initial
to ensure that high standards of achievement are established
and deformed microstructures.
and maintained. To meet these requirements, the commit-
• Cost reduction. Advances are needed to reduce the
tee recommends the notional DoD organizational approach
cost of producing protection materials by improving
depicted in Figure S-2.
their processing and yield and by improving small-lot
manufacturing capability.
Recommendation S-4/6-4. In order to make the major ad-
• Processing science and intelligent manufacturing.
vances needed for the development of protection materials,
Advances are needed in basic understanding of and
the Department of Defense should appoint a PMD program
ability to model the consequences of material pro-
director, with authority and resources to accomplish the
cessing for performance and other characteristics
following:
of interest. Intelligent manufacturing sensing and
control capabilities are needed that can maintain low
• Plan and execute the PMD initiative and coordinate
variance and produce affordable protection materials,
PMD activities across the DoD.
even in relatively low volumes.
• Select an existing facility to be the DoD center for
PMD and fund a research director and the staff,
Element 4—Organizational Approach
e quipment, and programs needed by the PMD
initiative;
The fourth element of the PMD initiative is an organi-
• Award a competitive contract for an open access
zational construct for multidisciplinary collaboration among
PMD center whose mission would be to host and
academic researchers, government laboratories, and indus-
foster open collaboration in research and develop-
try, in both restricted-access and open settings. The PMD
ment of protection materials;
initiative will need strong top-level leadership with insight
into both the open and restricted research environments and
Program
Review Board
Director
$ $
Visiting
Researchers
Open PMD Restricted DoD PMD
Canonical
Collaboration Collaboration
Models
Center Center
Test Services and
Models / Codes
Universities
Other Government Labs
#...
Industry #2
Industry #1
Industry
FIGURE S-2 PMD initiative organizational structure involving academic researchers, government laboratories, and industry.
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6 OPPORTUNITIES IN PROTECTION MATERIALS SCIENCE AND TECHNOLOGY FOR FUTURE ARMY APPLICATIONS
research collaborations.4 Such limitations are prudent and
• Establish an external review board to conduct peri-
odic reviews of programs in both centers; and necessary but require periodic review to ensure they are
• Provide liaison with the Department of Energy, the consistent with the current state of open knowledge and do
National Institute of Standards and Technology, and not unnecessarily restrict the exchange of information with
other government laboratories on matters related to an open research community when such an exchange would
PMD. be beneficial to national security.
The chapters that follow develop the rationale and
The sponsor asked that the committee suggest an or- conclusions that underpin the detailed recommendations in
ganizational structure for the path forward and a teaming Chapter 6 and identify needed actions in the four elements
approach for it. In considering the sponsor’s request that the of the initiative.
study report not include restricted material, which would
4A detailed discussion of the effects on research of classification guide -
have precluded wide dissemination to the research and devel-
lines, security, and export control is beyond the scope of this study.
opment communities, the committee recognized the broader
issue of the role restricted information plays in impeding
