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4
Lightweighting Land-Based Vehicles
4.1 CURRENT STATE OF LIGHTWEIGHTING IMPLEMENTATION AND METRICS
4.1.1 Drivers of Lightweighting
Lightweighting of land-based vehicles has been a strategic focus of the U.S. military for decades. The principal
drivers for lightweighting are as follows:1,2
• Increased protection and survivability of personnel and vehicles, enabled by a re-allocation of material
weight in non-protective functions into enhanced armor systems;
• Reduced costs of operation, extended vehicle range, and reduced needs for in-theater transportation of
fuels resulting from improved fuel efficiency of lighter vehicles;
• Increased vehicle mobility, agility, payload and speed as well as greater flexibility of operations over a
wider range of terrains; and
• Improved transportability and speed of force deployment enabled by reduced vehicle weight.
4.1.2 Historical and Current Lightweighting
Lightweighting in land-based vehicles has been achieved principally by replacing steels with high-strength
aluminum alloys and, more recently, titanium. Numerous examples of successful, economical vehicles of aluminum
construction are found over the past half-century. Tracked combat vehicles offer more opportunity and greater
performance benefits—particularly where protection is concerned—than the naturally lighter support vehicles.
Hence, despite the far greater number of the latter, the chapter focuses on heavy combat vehicles.
Use of aluminum alloys in tactical land-based vehicles has not been restricted to the United States. These
alloys have also been employed on the hull and turret of the BMP-3 (nicknamed Troyka) one of the most heavily
1 D. Gorsich, Chief Scientist, Tank Automotive Research, Development & Engineering Center (TARDEC), “Overview: Military Ground
System Material Needs,” presentation to the committee, 2010.
2 NRC. 2003. Use of Lightweight Materials in 21st Century Army Trucks. Washington, D.C.: The National Academies Press. Available at
http://www.nap.edu/catalog.php?record_id=10662.
85
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86 APPLICATION OF LIGHTWEIGHTING TECHNOLOGY TO MILITARY AIRCRAFT, VESSELS, AND VEHICLES
FIGURE 4-1 A warrior vehicle with added reactive appliqué and bar-armor. SOURCE: BAE Systems, U.S. Combat Systems,
“Lightweighting in Military Vehicles,” presentation Figure 4-1.eps
to the committee, December 8, 2010.
bitmap
armed infantry combat vehicles of the Soviets.3 They have also been used on the FV 510 Warrior Infantry Section
Vehicle, built in the United Kingdom. The latter was constructed of an aluminum alloy hull and equipped with
additional appliqué armor as well as explosive-reactive armor and bar armor (Figure 4-1). The efficacy of the
protection system against small arms, missiles, rocket propelled grenades, and anti-tank mines was proven during
the United Nations operations in Bosnia.4
Despite the performance enhancements obtained from the use of aluminum alloys in structural components
of ground vehicles, their use in armor systems for tactical vehicles has met with mixed success.5 The difficulty of
using aluminum alloys in armor can be attributed at least in part to an inadequate understanding of the ballistic
and blast properties of these alloys over the pertinent threat range. The ballistic properties are better understood
than blast properties; however, the modeling of both types of threats is insufficient for the predictive modeling
and systems-level design for performance across the full spectrum of current threats from improvised explosive
devices (IEDs), explosively formed projectiles (EFPs), and other sources.
Recent aluminum-alloy developments have led to further improvements in ballistic resistance and durability.
For instance, Al 2519-T87 (MIL-DTL-46192) exhibits better performance against fragmentation threats than Al
5083, with nearly the same performance against ball and armor piercing threats as Al 7039, coupled with good
corrosion resistance. The first production utilization of this alloy will be the Marine Corps Expeditionary Fighting
Vehicle.6
3 For information on BMP-3 specifications, see http://www.army-technology.com/projects/bmp-3/specs.html and http://www.army-
technology.com/projects/bmp-3/, last accessed October 19, 2011.
4 Christopher Foss and Peter Sarson. 1994. Warrior Tank Specifications: Warrior Mechanised Combat Vehicle 1987-1994 . New Vanguard
Series No. 10. London: Osprey. Available at http://www.army-technology.com/projects/warrior/.
5 Much of the information on lightweighting armor systems for land vehicles using materials other than aluminum is either restricted or
classified and therefore is not included in this report.
6 “Army Materials Research: Transforming Land Combat Through New Technologies.” AMPTIAC [Advanced Materials and Process Technol-
ogy Information Analysis Center] Quarterly, Vol. 8, No. 4, 2004. Available at http://ammtiac.alionscience.com/pdf/AMPQ8_4.pdf.
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LIGHTWEIGHTING LAND-BASED VEHICLES
Present Status
The Army has not fielded any new major combat platforms for over 20 years. Some of its early lightweight -
ing successes still see combat. Section 4.5, which describes examples of lightweighting vehicle systems, begins
with three such successes: the M113 Armored Personnel Carrier, the M551 Sheridan Light Tank, and the Bradley
Fighting Vehicle.
That does not mean that the Army no longer has interest in lightweighting. On the contrary, over the past two
decades it has launched five separate programs that prominently featured lightweight designs—none of which has
reached production and integration into the battlefield. The difficulties facing these programs offer lessons for
future lightweighting efforts. Two of these canceled programs are described in Section 4.5: the XM2001 Crusader
155mm Self-Propelled Howitzer and the Future Combat System.
4.1.3 Current State of Metrics
Unlike the aircraft industry, where the metrics for lightweighting are well established and feature prominently
in the earliest stages of the design process, a comparable set of quantitative metrics appears not to exist in the
ground vehicle community. Designs are usually constrained by overall vehicle weight, typically set to meet air
transportability requirements. Weight savings that may be achieved through use of low-density materials or clever
lightweighting designs are parlayed into weight additions elsewhere in the vehicle, to enhance functionality, e.g.,
increased protection against evolving threats, such as those encountered in Iraq and Afghanistan. Hence there does
not appear to be a well-defined or overarching metric that characterizes “the value of a pound saved.”
In some respects, lightweighting may appear to be antithetical to the goal of warfighter protection. Histori -
cally, the level at which vehicle requirements—protection and otherwise—have been met correlates strongly with
overall vehicle weight. That is, heavier classes of combat vehicles generally meet more requirements and to a
higher degree than those in the lower weight classes (Figure 4-2). But these improvements invariably come at the
FIGURE 4-2 Tradeoffs between combat vehicle weight and achievement of performance requirements. SOURCE: Adapted
Figure 4-2.eps
from BAE Systems, U.S. Combat Systems, “Lightweighting in Military Vehicles,” presentation to the committee, December
bitmap
8, 2010.
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88 APPLICATION OF LIGHTWEIGHTING TECHNOLOGY TO MILITARY AIRCRAFT, VESSELS, AND VEHICLES
expense of reduced fuel economy, mobility, and speed. The broad trend (especially with respect to survivability)
reflects to some extent the additional armor afforded to heavier vehicles. In principle, lightweighting could have
beneficial effects on these attributes without necessarily compromising protection. As noted in Chapter 1, light -
weighting can help to balance the “iron triangle” of performance, protection, and payload.
The challenge stems from the fact that, for a prescribed dynamic load (from a buried mine explosion, for
example), the acceleration of the vehicle scales inversely with its mass. This, in turn, has important implications
in the potential threat to the vehicle occupants. Clearly, this is a feature that does not derive benefit from light -
weighting. Thus, lightweighting might in some circumstances be viewed as a strategy for reducing weight in one
component in order to increase survivability by adding weight to a different component.
4.2 BARRIERS AND KEYS TO SUCCESS
4.2.1 Technological Challenges
Materials
Achieving protection goals while holding down costs is a continual challenge. In armor systems, significant
weight reductions can be achieved through the replacement of armor steels with advanced aluminum alloys, com -
posites, ceramics, and expanded steel. But the weight reductions come at the expense of higher cost (for examples,
see Figure 4-3). In principle, even greater reductions could be achieved through the use of detection avoidance
technologies and active protection systems.
FIGURE 4-3 Tradeoffs between weight reduction and cost for some candidate materials systems used in armor systems.
Figure 4-3.eps
SOURCE: Adapted from BAE Systems, U.S. Combat Systems, “Lightweighting in Military Vehicles,” presentation to the
bitmap
committee, December 8, 2010.
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LIGHTWEIGHTING LAND-BASED VEHICLES
Other structural materials, notably magnesium and titanium alloys, offer large potential advantages over steels,
including higher specific strength, absence of low-temperature embrittlement, and greater structural rigidity result -
ing from thicker sections. Titanium also exhibits superior corrosion resistance in most service environments, yet
the utilization of these materials remains rare. Numerous barriers exist to their exploitation. Chief among them
are cost and domestic availability:
• The cost of extraction of raw titanium is inherently high. The current price of titanium in ingot form is
approximately $20/lb. Steels, in contrast, cost between $0.50 and $3.00/lb depending on alloy and product
form. Magnesium is significantly cheaper than titanium, with a current price of approximately $2/lb. For
land structures, most applications of titanium and magnesium would be in the form of sheet and plate.
The complexity of forming titanium and magnesium alloys into useful engineering shapes coupled with
their low production volumes exacerbate the price differentials with the baseline steels. 7
• Domestic availability and sheet/plate manufacturing capacity of magnesium and titanium alloys are far
below the large-tonnage requirements of targeted land-based military vehicle applications.
Additional (secondary) considerations include the following:
• Welding is the most economical way to join materials in producing large structures with good mechani-
cal integrity. It is also the principal route for producing water-tight structures (e.g. amphibious vehicles).
The weldability of titanium and magnesium alloys remains problematic in routine industrial practice in
land-based vehicles.
Monolithic aluminum, magnesium, and titanium alloys exhibit inferior spall resistance relative to steels.8
•
They may also exhibit inferior service lives due to lower fatigue resistance as well as susceptibility to
corrosion in marine environments.
• There is an understandable reluctance within the DOD and its suppliers to transition to new materials that
are not supported by comparable levels of experience in manufacturing, assessment of battlefield damage,
and in-field repair.
New Designs
Some intriguing new designs for vehicles are emerging that offer promise for greater protection without
adding more armor weight. One approach for military trucks is to “vent” the dynamic load (explosive force) up
through a channel in the vehicle as if through a chimney to reduce the coupling of the blast loading to the vehicle. 9
As reported in the New York Times, “if the final tests go well, the invention could save billions in new vehicle
costs and restore much of the maneuverability that the Army and the Marines have lacked in the rugged terrain in
Afghanistan, military officials say.”10
Another approach is to adapt the V-hull design used in mine-resistant trucks into a double V-hull for the
Army’s Stryker Brigade Combat Vehicle. The recent award of a contract to build 450 double V-hull Stryker vehicles
comes in response to the need to counter the increasingly deadly threats experienced in Afghanistan from roadside
7 For more information on forming titanium and magnesium alloys, see http://www.metalprices.com/FreeSite/metals/ti/ti.asp and http://www.
metalprices.com/freesite/metals/Steel/Steel.asp. Last accessed October 19, 2011.
8 BAE Systems, U.S. Combat Systems, “Lightweighting in Military Vehicles,” presentation to the committee, 2010; and “Army Materials
Research: Transforming Land Combat Through New Technologies,” AMPTIAC [Advanced Materials and Process Technology Information
Analysis Center] Quarterly, Vol. 8, No. 4, 2004, available at http://ammtiac.alionscience.com/pdf/AMPQ8_4.pdf.
9 Grace V. Jean. 2011. “Double V-Hulls, Chimneys, Seen as Viable Alternatives to Armor.” National Defense. March. Available at http://www.
nationaldefensemagazine.org/archive/2011/March/Pages/ DoubleVHullsChimneysSeenAsViableAlternativestoArmor.aspx.
10 Christopher Drew. 2011. “Revamped Humvee Draws Military’s Eye.” New York Times. July 22. P. B1. Available at http://www.nytimes.
com/2011/07/23/business/humvee-with-chimney-for-safety-draws-militarys-interest.html. Last accessed October 19, 2011.
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90 APPLICATION OF LIGHTWEIGHTING TECHNOLOGY TO MILITARY AIRCRAFT, VESSELS, AND VEHICLES
FIGURE 4-4 Three joint light tactical vehicle prototypes. SOURCE: S. Magnuson. 2010. “New Truck to Show the Way for
Acquisition Reforms.” National Defense Magazine. Figure 4-4.eps
August.
bitmap
bombs.11 Improved vehicle survivability in this evolving production and upgrading of vehicles will be accomplished
by added armor and alterations in design approaches.12
4.2.2 Reducing the Acquisition Cycle
The technological challenges are exacerbated by a protracted acquisition process during which the vehicle
requirements often “creep.” That is, various DoD agents sequentially add requirements from the time of initial
design to that of vehicle production and delivery. Without knowledge of the full spectrum of expected requirements
of the vehicles at the outset, defense contractors are naturally disinclined to replace existing materials with new
ones. The risk is that deficiencies in material performance may not emerge until late in the design and manufactur -
ing stages, wherein the full spectrum of requirements becomes known.
Attempts at accelerating the process through competitive prototyping—a process in which two or more defense
contractors produce competing prototypes—have met with mixed success. 13 Its underlying rationale is that forcing
the manufacturers to use proven technologies will discourage the later introduction of new and untested compo -
nents; as a result, competitive prototyping is expected to reduce the risk of cost overruns and failure for military
hardware development programs. It has been adopted as a mandatory requirement in DOD Instruction 5000.2,
updated in December 2008.
In a recent example of competitive prototyping, three vendors—BAE Systems, Lockheed Martin, and a con -
sortium of AM General and General Dynamics Land Systems—produced a total of 21 prototypes (Figure 4-4) for
the Joint Light Tactical Vehicle (JLTV) program, which is intended to replace some Humvees (HMMWVs—High-
Mobility Multipurpose Wheeled Vehicles). Testing of these prototypes began in August 2010. The initial promise
of this endeavor faded, as Mark McCoy, the Army’s JLTV product manager, reported in February 2011 that every
prototype design was between a few hundred and 1,000 lb too heavy to be airlifted by a CH-47 Chinook helicopter.14
The JLTV was intended to meet the needs of the Army, which placed greater emphasis on protection, and
the Marine Corps, which gave higher priority to lightweighting. Attempting to satisfy both sets of requirements
simultaneously is likely the reason that the 21 JLTV prototypes failed to meet weight specifications, resulting in
11 Grace V. Jean. 2011. “Double V-Hulls, Chimneys, Seen as Viable Alternatives to Armor.” National Defense. March. Available at http://
www.nationaldefensemagazine.org/archive/2011/March/Pages/ DoubleVHullsChimneysSeenAsViableAlternativestoArmor.aspx.
12 Christopher Drew. 2011. “Revamped Humvee Draws Military’s Eye.” New York Times. July 22. P. B1. Available at http://www.nytimes.
com/2011/07/23/business/humvee-with-chimney-for-safety-draws-militarys-interest.html. Last accessed October 19, 2011.
13 This section draws on S. Magnuson, 2010, “New Truck to Show the Way for Acquisition Reforms,” National Defense Magazine, August,
available at http://www.fas.org/sgp/crs/natsec/RL34026.pdf; and E. Beidel, 2011, “Challenges Remain as JLTV Competition Heats Up,” Na-
tional Defense Magazine, May.
14 Reported at the National Defense Industrial Association’s Tactical Wheeled Vehicle conference, February 2011, and reported in E. Beidel,
2011, “Challenges Remain as JLTV Competition Heats Up,” National Defense Magazine, May.
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LIGHTWEIGHTING LAND-BASED VEHICLES
a delay in finding a satisfactory “trade” between protection and weight-related performance characteristics for
light tactical wheeled vehicles.
The JLTV prototype experience suggests the desirability of finding ways to increase the probability that pro -
totypes will meet requirements. For example, instead of discovering during prototyping how new materials and
new designs for lightweighting affect other attributes, it would improve the chances of detecting and addressing
problems to test new technologies earlier in the acquisition process. For example, perhaps a precursor demonstra -
tion step could try out new materials and new designs for lightweighting in terms of their effects on other attributes
before a prototype is developed.
The Weapons System Acquisition Reform Act of 2009 requires that competitive prototypes be produced
for major weapons acquisition programs prior to Milestone B, which is when independent review boards decide
whether the program can proceed to the engineering and manufacturing development (EMD) phase. 15 Under some
circumstances competitive prototyping may be waived, in which case only one prototype is required. Nonetheless,
it appears that the Army has been able to waive even the single prototype requirement prior to EMD as evidenced
by JLTV program. Specifically, a recent JLTV vehicle update stated:
The Government has made a determination to NOT require the delivery of a demonstrator vehicle during the EMD
RFP proposal phase. Due to evolving EMD requirements, it is assumed that any demonstrator vehicle built to cur-
rently available draft RFP requirements will not be reflective of the final RFP requirements for EMD. 16
The Army’s decision is based on the expectation that the requirements will change, but it has the added benefit
of providing more time to validate the technology before building a prototype. 17
4.3 LIGHTWEIGHTING OPPORTUNITIES FOR LAND-BASED VEHICLES
Lightweighting of land-based vehicles remains a clear strategic focus of the DoD. 18 Indeed, with the escala-
tion in “scope growth and requirements creep”—that is, the expansion of the requirements of a single vehicle in
order to meet a multitude of mission types and increased operational performance, such as increased warfighter
protection, increased vehicle range, and reduced energy utilization, while minimizing development and production
costs of multiple vehicle variants—the need for lightweighting is arguably more acute than ever.
Numerous opportunities exist to improve tactical utility of future military vehicles through lightweighting.
Bringing them to fruition will require long-term commitments and coordinated multi-agency strategies. Specific
opportunities and strategies for their successful implementation follow.
4.3.1 Systems Engineering
As described in Chapter 2 (Air), systems engineering is a strategy for considering the many elements of a
complex system early in the design and acquisition of that system. Bringing together experts knowledgeable about
diverse aspects of the system—components, design, manufacturing, performance, cost, etc.—the risk of discovering
15 Weapon Systems Acquisition Reform Act of 2009, 111 th Congress, S. 454, Sec. 203, available at http://www.gpo.gov/fdsys/pkg/BILLS-
111s454enr/pdf/BILLS-111s454enr.pdf.
16 For more information on the Joint Light Tactical Vehicle (JLTV) EMD Phase, see http://contracting.tacom.army.mil/majorsys/jltv_emd/
jltv_emd.htm, last accessed September 28, 2011.
17 While considering next steps for the JLTV, the Army is also pursuing the Humvee Recap, intended to add protection to the Humvee while
maintaining or reducing weight. See Grace V. Jean, “Humvee Recap Competition Heating Up,” National Defense, October 2011, available at
http://www.nationaldefensemagazine.org/archive/2011/October/Pages/HumveeRecapCompetitionHeatingUp.aspx. It was beyond the commit -
tee’s scope to address the choices among lightweight tactical land vehicles; the JLTV is described to illustrate competitive prototyping and the
difficulty of meeting different needs simultaneously.
18 NRC. 2003. Use of Lightweight Materials in 21st Century Army Trucks . Washington, D.C.: The National Academies Press. Available at
http://www.nap.edu/catalog.php?record_id=10662. Last accessed October 19, 2011.
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92 APPLICATION OF LIGHTWEIGHTING TECHNOLOGY TO MILITARY AIRCRAFT, VESSELS, AND VEHICLES
deficiencies later in the process is reduced. Within the Army, TARDEC takes the lead on systems engineering for
ground vehicles.19 The last example in Section 4.5 is the successful use of systems engineering in the Ford F-150.
4.3.2 Virtual Prototyping
The computing power available to the DOD is tremendous. It should enable increased use of virtual prototyp -
ing and increased emphasis on system design, in part to allow early assessment of the tradeoffs in lightweighting
strategies. This goal will require integration of shared models of materials, processes and performance between
vendors and original equipment manufacturers (OEMs). Virtual prototyping would also have the desirable effect
of compressing the acquisition cycle.
As suggested under “Competitive Prototyping,” ways of increasing the probability that prototypes will meet
requirements may be available. Virtual prototyping could play an important role in assessing new materials and
new designs for lightweighting in terms of their effects on other attributes. The design solutions that look the most
favorable could then progress to the physical prototyping stage.
4.3.3 New Computational Tools
The success of virtual prototyping and system design is predicated on the availability and use of high-fidelity
computational tools for describing the loads imparted by specific enemy threats, e.g., kinetic energy penetrators,
shaped charges, EFPs, and IEDs, as well as the response of materials and structures under those loads. Although
significant progress has been made on this front over the past decade, striking deficiencies are evident and require
remediation. Specifically, there is a need to develop a better understanding of the physics and mechanics of plas -
tic flow, damage evolution and material rupture under extreme dynamic environments. Effects of microstructural
heterogeneities in single- and multiphase systems, processing history and probabilistics need to be considered as
well. Additionally, codes that integrate multi-physics phenomena and multiple length scales are required. There are
also deficiencies in commercial finite element codes in accurately capturing the coupling between dynamic loads
and structural response. The opportunities for potentially fruitful research areas include extended finite element
codes, particle-based numerical methods, and adaptive physics models.
4.3.4 Lightweight Materials
A number of relatively lightweight materials such as titanium, magnesium, and structural composites show out-
standing potential for lightweighting and for expanding the capabilities of military vehicles. But in many instances
the implementation of these materials is hampered by their high costs, low technology or manufacturing readiness
levels, and limited domestic availability. Capitalization of these opportunities will require a federal investment
strategy to identify the materials that are of greatest strategic value to the DOD, seek lower-cost production routes,
and increase the domestic processing capacity and manufacturing readiness levels.
One way to facilitate the introduction of lightweight materials is through increased utilization of the same
materials in industrial sectors such as transportation, aerospace, energy security, and power generation. For
example, the materials requirements for heavy wheeled equipment and trucks have many potential parallels with
land-based military vehicles. In this context, it is important to note that the National Automotive Center (NAC)
at TARDEC has the mission to identify and develop dual-use technologies for land-based vehicles between DOD
and the automotive industry.
Recent advances in the synthesis of titanium alloy powders by direct reduction methods (meltless titanium)
have led to new opportunities to produce titanium alloys with enhanced capabilities at lower cost. 20
19 John Wray.2010. “‘Insight, Not Just Oversight’—Following DOD Lead, Embedded Systems Engineering Provides the Framework for Solid
Decision.” Accelerate magazine, Summer, p. 10. Available at http://tardec.army.mil/Documents/TARDEC_0910_accelerate_Summer_2010.pdf.
20 A. Woodfield, E. Ott, J. Blank, M. Peretti, D. Linger, and L. Duke. 2009. “Meltless Titanium—A New Light Metals Industry.” Materials
Science Forum, Vols. 618-619, pp. 135-138.
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LIGHTWEIGHTING LAND-BASED VEHICLES
4.3.5 Standardization in Vehicle Design
The success of military vehicles is predicated on the alignment of their capabilities with mission require -
ments. The recent historical experience has been that enemy threats and the associated mission requirements
have evolved more rapidly than the corresponding capabilities, especially with regard to protection systems. This
disparity requires not only close scrutiny of the threats that are likely to be faced in the future (a challenging task
that is undoubtedly being tackled by the DOD) but also emphasis on the adaptability of fielded systems to meet
the evolving threats. Commonality and standardization in vehicle design may help to improve in-theater upgrading,
facilitate repair, and reduce costs and acquisition times.
4.3.6 Other Emerging Technologies
Among the emerging structural concepts for lightweighting, high-strength “expanded steel” for use in armor
systems shows promise. Concepts that enable multi-functionality, e.g., by combining structural functionality with
personnel and cargo protection, are also worth pursuing.
It would appear that there are also opportunities for very significant reductions in the weight of protection
systems through emerging detection avoidance and active protection technologies. Identifying revolutionary or
game-changing strategies to protection could reduce the needed armor, with major lightweighting benefits..experi -
ence of the Future Combat System (see Section 4.5.5) might offer some lessons.
Development and use of materials and design tools for lightweighting of land-based military vehicles will
be a source of information and tools for the automotive industry, which has been striving to reduce the weight of
vehicles without compromising other attributes that consumers value.
4.4 LONG-TERM CONCERNS IN LIGHTWEIGHTING LAND-BASED VEHICLES
A National Research Council report,21 written and released in 2003, concluded that cost was the principal factor
driving the design of Army vehicles. Almost immediately thereafter, the start of the U.S. conflicts in Afghanistan
and Iraq meant that U.S. troops were actively engaged in combat. The current view from all levels within the
DoD appears to be that, with troops presently in combat and considering the heavy casualties incurred over the
past 8 years, protection is the preeminent driver of vehicle design. It would not be unexpected, however, to see the
pendulum swing back—wherein greater focus is directed at cost rather than principally protection—once active
conflicts have ended and the immediate risks to warfighters have seemingly dissipated. Balancing these competing
drivers of design in a changing environment is a never-ending issue.
Implementation of lightweighting strategies will require a multi-pronged approach involving not only scientific
discovery and technology development but also coordinated federal strategies and policies. Perhaps the largest
barrier stems from the broad perception that the fields of structural materials and manufacturing are sufficiently
mature so as to warrant only minimal research support and development. Indeed, the past two decades have seen a
dramatic decline in funding in these areas. It seems likely that further progress in lightweight structural materials
and their associated manufacturing processes will be incremental and slow.
21 NRC. 2003. Use of Lightweight Materials in 21st Century Army Trucks. Washington, D.C.: The National Academies Press. Available at
http://www.nap.edu/catalog.php?record_id=10662.
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94 APPLICATION OF LIGHTWEIGHTING TECHNOLOGY TO MILITARY AIRCRAFT, VESSELS, AND VEHICLES
4.5 EXAMPLES OF LIGHTWEIGHTING IN LAND-BASED VEHICLES
4.5.1 M113 Armored Personnel Carrier
The M113 Armored Personnel Carrier (APC)22 was introduced in 1960 to transport infantry forces across
a hostile battlefield. Lightweighting helped the M113 APC revolutionize mobile military operations; it was air-
transportable, air-droppable, and capable of amphibious operation in lakes and streams, cross-country travel over
rough terrain, and high-speed travel on pavement. These features allowed the M113 to be deployed in a wide range
of combat situations and rapid-deployment scenarios.
The U.S. Army was the first service to use alumi-
num as an armor material in armored transport vehicles
M113: Lightweighting When
and offensive weapon vehicles. The original M113 was
Survivability Is Primary
built of aircraft-quality23 Aluminum 5083—an alloy
that possesses strength approaching those of some
The many variants in the M113 family of vehicles
steels at only about one-third the weight. The hull
illustrate that effective lightweighting can be
armor was also made from Aluminum 5083.
used to retain performance characteristics while
The M113 has been remarkably successful; about
improving survivability.
80,000 M113-based systems have entered service in
more than 50 countries. It became the basis for a
family of vehicles produced in about 40 variants, with many times that number of minor field modifications. With
updating and reconfiguring, M113s are still being produced and fielded today.
The M113 was conceived as a “battle taxi” that would carry infantry to the battlefield, where they would
fight on foot. Early in the Vietnam War, this approach resulted in high casualties for the Army of the Republic of
Vietnam (ARVN), as they dismounted into knee-deep water where they were vulnerable to enemy fire. Thereafter,
the ARVN ignored U.S. doctrine and remained inside the M113. While the Aluminum 5083 armor in the M113
stopped small arms bullets and shell fragments, it did not stop rocket-propelled grenades or provide adequate
protection against mine blasts detonated under the vehicle. In 1965, the ARVN modified the M113 by expanding
from one exposed machine gun to three machine guns, all protected by armor; this version was the first armored
cavalry assault vehicle (ACAV). Starting in 1966, an improved version of the ACAV was deployed in Vietnam by
U.S. troops, with further upgrades during the war (Figure 4-5).
A major redesign came in 1987, with the introduction of the A3 version. Spall suppression liners throughout
the interior of these vehicles offer greater troop protection by restricting the spread of spall when a round pen -
etrates the hull. A new powertrain provides greater mobility and survivability, while improving fuel efficiency,
acceleration, speed, and braking.
The upgrades have increased the weight—the combat weight of the 1960 M113 was 23,520 lb, compared
with 27,200 lb for the A3. As a result, the A3 was given a more powerful engine, which offered the ability to add
hardened steel side armor, a “slat armor” cage, and additional anti-mine armor on the vehicle underbelly. Although
the armor increases the weight to 31,000 lb, the use of lightweighting techniques has made it possible for the A3
to have the desired performance and survivability attributes.
While the U.S. Army returned to the single machine gun M113 after the Vietnam War, the Israeli Defense Force
(IDF) embraced the idea of the ACAV and still uses it today. Its version is protected by a “skirt” of lightweight
sheets of perforated steel, which reduces damage by detonating rocket-propelled grenades before they come into
contact with the hull. The IDF tried a variant with explosive reactive armor, but the added weight strained the
22 The description of the M113 draws on D. Starry, 1978, “Mounted Combat in Vietnam,” Vietnam Studies, CMH Pub 90-17, Department
of the Army; S. Dunstan, 1983, The M113 Series, London: Osprey; S. Crist, 2004, “M113 APC: Four Decades of Service and Still Showing
Potential,” Infantry Magazine, July-August, available at http://findarticles.com/p/articles/mi_m0IAV/is_4_93/ai_n6362165/; http://www.fas.
org/man/dod-101/sys/land/m113.htm; and http://www.army.mil/factfiles/equipment/tracked/m113.html, accessed June 10, 2011.
23 The development and qualification of aluminum alloys did not progress as quickly for use in land vehicles as for use in aerospace
applications.
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LIGHTWEIGHTING LAND-BASED VEHICLES
FIGURE 4-5 M113 armored cavalry assault vehicle in Vietnam. SOURCE: Available at http://en.wikipedia.org/wiki/
Figure 4-5.eps
File:Armored_cavalry_assault_vehicle.jpg.
bitmap
engine and reduced speed and handling; this variant was discontinued. The IDF is now working on a lightweight
but stronger armor made of layers of steel, rubber, ceramics, and explosive reactive armor.
4.5.2 M551 Sheridan Light Tank
The M551 Sheridan Light Tank,24 shown in Figure 4-6, was an assault vehicle designed in the early 1960s to
have both air-drop and swimming capabilities. It saw extensive combat in Vietnam and limited service in Opera -
tion Just Cause (in Panama) and Operation Desert Storm (in Kuwait).
The Sheridan Tank was armed with a technically advanced gun that fired conventional ammunition and
guided anti-tank missiles. With an aluminum hull and
the first use of spaced aluminum armor, it was at the
M551: Improved Performance,
time a unique approach to lightweighting. Equipped
Decreased Survivability
with a relatively powerful 300 hp diesel engine, the
M551 was exceptionally fast. It was airdrop-capable
The M551 illustrates the mixed success experi-
and fully amphibious, but these advantages of light
enced in replacing steels with aluminum alloys
weight came at a cost.
in military vehicles for which survivability and
In its first combat mission, the Sheridan drove
performance are both important. The specific
over a mine, which ruptured its hull and then ignited
approaches to lightweighting the M551 created
the ammunition of the main gun, causing an explosion vulnerabilities.
that destroyed the tank. The aluminum armor could be
pierced not just by under-belly mines but also by heavy
24 The description of the M113 is based on D. Starry, 1978, “Mounted Combat in Vietnam,” CMH Pub 90-17, Vietnam Studies, Department
of the Army; R.P. Hunnicutt, 1995, Sheridan: A History of the American Light Tank, Vol. 2, Presidio Press; and http://www.army-guide.com/
eng/product3393.html.
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96 APPLICATION OF LIGHTWEIGHTING TECHNOLOGY TO MILITARY AIRCRAFT, VESSELS, AND VEHICLES
FIGURE 4-6 M551 Sheridan tank. SOURCE: BAE Systems, U.S. Combat Systems, “Lightweighting in Military Vehicles,”
presentation to the committee, December 8, 2010. Figure 4-6.eps
bitmap
machine-gun rounds as well. Its 152mm gun was too big for the lightweight chassis, causing the entire vehicle to
recoil with great force when the gun was fired. Field commanders commonly added a large steel shield around the
gun for protection while firing it. The Sheridan was good at opening bamboo thickets, but not at breaking through
dense jungle. Thus, although the Sheridan had greater mobility, firepower, range, and night-fighting ability than
its predecessor, its deficiencies led to heavy Sheridan losses in Vietnam and Cambodia.
The Army began to phase out the Sheridan in 1978; however, the 82nd Airborne Division retained its until
1996 because the Sheridan was the only air-deployable tank in its inventory. The Sheridan tanks were upgraded
with a thermal sighting system and were used successfully in Operation Just Cause and Desert Storm.
4.5.3 Bradley Fighting Vehicle
The Bradley Fighting Vehicle25 was originally designed as an APC and a tank-killer. Its main task was trans -
porting infantry with armor protection while providing covering fire to pin down enemy troops. The new Bradley
was designed to keep up in formation with M1 Abrams battle tank. This allowed the two vehicles to maintain for-
mations while moving, something that the older M113
could not do as it had been designed to complement
Bradley: Benefits of Various the M60 Patton.
Aluminum Alloys The Bradley, shown in Figure 4-7, had a hull
base made from Al 5083-H131 (MIL-DTL-46027),
Experience with different aluminum alloys on the and the upper half of the vehicle employed Al 7039-
Bradley Fighting Vehicle has provided knowledge T64 (MIL-DTL-46063). In service, the 7039 alloy has
that can be applied to future vehicles. been found to exhibit better performance against ball
and armor piercing (AP) threats than 5083 but with
25 Thiscase study is based on W.B. Haworth, 1999, The Bradley and How It Got That Way: Technology, Institutions, and the Problem of
Mechanized Infantry in the United States Army, Westport, Conn.: Greenwood Press; “Army Materials Research: Transforming Land Combat
Through New Technologies,” AMPTIAC [Advanced Materials and Process Technology Information Analysis Center] Quarterly, Vol. 8, No. 4,
2004, available at http://ammtiac.alionscience.com/pdf/AMPQ8_4.pdf; and NRI, http://www.army-technology.com/projects/bradley.
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LIGHTWEIGHTING LAND-BASED VEHICLES
FIGURE 4-7 Bradley Fighting Vehicle. SOURCE: Available at http://osd.dtic.mil/photos/Nov2004/041030-F-2034C-040.html.
Figure 4-7.eps
bitmap
some loss in performance against fragmentation threats. However, 7039 has been found to be more susceptible to
stress-corrosion cracking, especially in the short-transverse direction.
Combat survivability concerns were raised about the Bradley because it used aluminum armor, and ammunition
is stored in the middle of the vehicle, but the Bradley has not experienced many losses. To improve survivability
and armor protection designers added spaced laminate belts and high-hardness steel skirts to later versions. These
additions increased overall weight by about 10 percent, to 33 tons, while decreasing the Bradley’s mobility. Later
versions of the Bradley and Abrams were designed to carry reactive armor26 to protect against RPGs. This armor
was employed in Iraq and proved effective in increasing survivability. In 2009, the Army awarded a contract to add
armor to protect against improvised explosive devices (IEDs), as well as other enhancements of warrior protection.
Crusader 155mm Self-Propelled Howitzer27
4.5.4
The Crusader 155mm artillery system (shown in Figure 4-8) was intended to be the Army’s next- generation
self-propelled (SP) howitzer, replacing the M109A6 Paladin SP Howitzer and the M992 Field Artillery Ammunition
Support Vehicle. It was initiated in 1994 to provide enhanced survivability, lethality, and mobility and therefore
be more readily deployable than the platforms it replaced. In 2000, after a 60-ton developmental platform was
produced, the Army restructured the program to meet the new weight requirement of 40 tons. This lower weight
would allow two vehicles to be transported into theater on a C-5 or C-17 aircraft, reflecting the Army’s planned
transformation to a lighter, more deployable future force. The schedule called for DoD to decide in April 2003
whether the Crusader should enter development and demonstration; assuming they continued the program, produc -
tion of an anticipated 1,100+ vehicles (later reduced to 480) was to begin in 2008.
26 From Jargon Database.com: “Reactive armor involves explosive devices attached to armored vehicles that explode before an incoming
projectile strikes the vehicle. The ensuing outward explosion deflects or minimizes the inward momentum of the oncoming projectile.” Avail -
able at http://www.jargondatabase.com/Category/Military/Army-Jargon/Reactive-Armor.
27 This section draws on Government Accountability Office, 2002, “Defense Acquisitions: Steps to Improve the Crusader Program’s Invest -
ment Decisions, February, available at http://www.gao.gov/new.items/d02201.pdf; and GAO, 2001, “Defense Acquisitions: Army Transforma -
tion Faces Weapon Systems Challenges, May, available at http://www.gao.gov/new.items/d01311.pdf.
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98 APPLICATION OF LIGHTWEIGHTING TECHNOLOGY TO MILITARY AIRCRAFT, VESSELS, AND VEHICLES
FIGURE 4-8 Crusader 155mm self-propelled howitzer. SOURCE: Available at http://www.pica.army.mil/voice2002/020517/
4_11_00%20Zone%206-1.jpg.
In May 2002, Secretary Rumsfeld cancelled the
Crusader: Importance of a Broad $11 billion dollar Crusader program because it was
Set of Goals for Lightweighting deemed neither mobile enough nor precise enough. A
GAO report determined that the improvement in trans-
portability was not significant—two complete systems
Lightweighting primarily for transportability proved
not to be a compelling reason to continue build- with supporting equipment would need four flights
ing a new system that was not sufficiently more instead of five. More importantly, that report found
capable than its upgraded predecessor—nor suf- that the majority of critical technologies were not suf-
ficiently ahead of its planned successor. Changing
ficiently mature and that the Crusader’s schedule had
requirements, as a result of the end of the Cold
considerable overlap with the Future Combat System
War, added to costs and schedule.
(see Section 4.5.5), which was intended to replace it.
With upgrades, the existing fielded Paladin possessed
sufficiently advanced performance characteristics to
make it still an effective weapon in the land-based vehicle category to meet Army needs.
In the context of the lightweighting focus of this report, the desired C-17 transportability featured significantly
in the design requirements central to the 155mm Crusader but did not take into account the transport of the sup -
porting equipment. A 20 percent reduction in C-17 flights was not sufficient to make up for the immaturity of
critical technologies and the rising costs.
Future Combat System (FCS) Combat Vehicles28
4.5.5
The Future Combat Systems (FCS) program was remarkably ambitious: a family of 14 high-tech manned and
unmanned combat vehicles, encompassing robots and an array of sensors, connected in a single battle command-
28 This
section is based on Andrew Feickert and Nathan Jacob Lucas, 2009, Army Future Combat System (FCS) “SpinOuts” and Ground
Combat Vehicle (GCV): Background and Issues for Congress, Congressional Research Service, November, available at http://www.fas.org/
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LIGHTWEIGHTING LAND-BASED VEHICLES
and-control network, at a cost of $92 billion (later increased to $164 billion). The Manned Ground Vehicle com -
ponent was planned to provide eight FCS variants: an infantry carrier, a command-and-control vehicle, a mounted
combat system, a reconnaissance and surveillance version, a non-line-of-sight cannon, a non-line-of-sight mortar,
a recovery and maintenance vehicle, and a medical treatment variant.
The FCS was introduced in 1999 as the major
research, development, and acquisition program
FCS: Too Ambitious for
intended to lead to the Army’s transformation. Key
Available Technology
requirements were C-130 transportability and an asso-
ciated fully loaded weight of 30 tons. It was to be as
The Future Combat System was a complex pro-
durable and to offer as much protection as an Abrams
gram with ambitious goals, including a lightweight-
Battle Tank, at only 25 percent of the weight. The ing goal of building a combat vehicle with only
weight requirement to allow C-130 transportability one- quarter of the weight of the Abrams tank
was considered crucial for landing in remote areas but similar speed and survivability. These goals
with, at best, primitive runways. depended on several technologies that required
The drive to lightweighting of the FCS concepts much additional development before they could be
inserted in the combat vehicles. When develop-
included an effort to significantly lower fuel costs,
ment did not occur quickly enough for the FCS
which entailed a radical change in technology. Instead
schedules, there were cost increases and delays.
of a gas-diesel powered engines, as used in the Prius,
the FCS called for development of the much less
mature technology for diesel-electric hybrid engines.
Another of the lightweighting strategies was to use new technologies for “active” defensive systems that have the
capability to shoot down incoming threats such as RPGs, thus needing less heavy armor than the Abrams, which
focuses on frontal attack survivability.
The Army treated its weight requirements as firm throughout much of the early tenure of the FCS program.
Thus, when the concepts submitted by the two prime contractors for the main vehicle were overweight, the Army
considered stripping some components to transport on a second aircraft, requiring additional logistical support to
reassemble the vehicle in theater. However, in 2005 the Army removed the C-130 transportability requirement and
substituted the stipulation that three FCS vehicles must fit in a C-17 heavy lift transport aircraft, thereby allowing
the FCS vehicle weight to increase from 18 to 25 tons.29
During 2003-2009, the program underwent several rounds of restructuring. In April 2009, Secretary Gates
recommended cancellation of the FCS Manned Ground Vehicle program. Secretary Gates and other critics gave
several reasons for the demise of the FCS program, included its high cost and declining relevance for expected
future defense needs. A chief listed cause is the reliance of FCS on technologies not yet mature; i.e., the technol -
ogy readiness levels (TRLs) were too low, particularly for the high-tech “active” protection systems. In 2006, the
GAO found that “none of FCS’s 49 critical technologies was at a level of maturity recommended by DoD policy
at the start of a program.”30 In 2008, GAO described the FCS as “about halfway through its development phase,
yet it is, in many respects, a program closer to the beginning of development.”31 It was the need to bring a large
number of needed technologies to maturity that led to cost increases, delays, and ultimately cancellation.
sgp/crs/weapons/RL32888.pdf; Sandra I. Erwin, 2009, “Uphill Battle: Army’s Next Combat Vehicle: New Beginning or FCS Sequel?,” Na-
tional Defense, August 1, available at http://www.highbeam.com/doc/1G1-205905726.html; Sandra I. Erwin, 2005, “Army Struggles with
Weight of Future Combat Systems,” National Defense, April, available at http://www.nationaldefensemagazine.org/archive/2005/April/Pages/
UF-Army_Struggles5799.aspx; Sandra I. Irwin, 2005, “For Army’s Future Combat Vehicles, Flying by C-130 No Longer Required,” National
Defense, November, available at http://www.nationaldefensemagazine.org/archive/2005/November/Pages/UF-For_Army5525.aspx.; and http://
www.globalsecurity.org/military/systems/ground/fcs.htm.
29 Sandra Erwin. 2005. “For Army’s Future Combat Vehicles, Flying by C-130 No Longer Required.” National Defense. November.
30 GAO. 2006. “Defense Acquisitions: Improved Business Case Is Needed for Future Combat System’s Successful Outcome.” GAO-06-367.
Available at http://www.gao.gov/new.items/d06367.pdf.
31 GAO. 2008. “Defense Acquisitions: 2009 Review of Future Combat System Is Critical to Program’s Direction, Statement of Paul L.
Francis, Director Acquisition and Sourcing Management.” GAO-08-638T. April. Available at http://www.gao.gov/new.items/d08638t.pdf.
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100 APPLICATION OF LIGHTWEIGHTING TECHNOLOGY TO MILITARY AIRCRAFT, VESSELS, AND VEHICLES
FIGURE 4-9 Impact of weight on fuel economy for personal vehicles. SOURCE: Bruno Barthelemy, Ford Motor Company,
“Lightweight Technologies,” presentation to the committee, October 2010.
Figure 4-9.eps
bitmap
4.5.6 Application of Systems Engineering to Lightweighting—Ford F-150 Example
Ford’s customers rarely care about the weight of their vehicles per se, but they do care about the vehicle’s
purchase price, operating costs, gas mileage, durability, and performance. Lightweighting improves performance
and gas mileage (Figure 4-9); the challenge is to obtain these benefits without sacrificing durability or crash -
worthiness. To achieve the best trade among performance, weight, cost, and gas mileage for the F-150 pickup,
Ford uses a sophisticated systems engineering approach that involves a gated technology readiness assessment, a
conceptual design that matches load lines to topology,
and maximizes unitization to meet crashworthiness
Ford: Systems Engineering and durability requirements.32
Supports Lightweightimg The systems engineering process brings together
all elements that affect the design of the system—
It takes more than materials to achieve lightweight design, engineering, manufacturing, assembly, and
products. Systems engineering involves a broad materials specialists to define a concept to reduce
group of experts so that materials, manufacturing, weight without reducing crashworthiness or durability
and assembly are all considered in the design of the truck. The process is collaborative. Manufactur-
of a system. A gated process makes sure that
ing brings its latest knowledge, experience, and scale-
technologies are of sufficient maturity before they
up demonstrations of hydroforming high-strength
are used.
steels. Assembly brings its latest capabilities for laser
welding and bonding. Together they bring their latest
32 Bruno Barthelemy, Ford Motor Company, “Lightweight Technologies,” presentation to the committee, October 2010.
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LIGHTWEIGHTING LAND-BASED VEHICLES
FIGURE 4-10 Improved topology offered by hydroformed substructures. SOURCE: Bruno Barthelemy, Ford Motor Company,
Figure 4-10.eps
“Lightweight Technologies,” presentation to the committee, October 2010.
bitmap
demonstrations of combining hydroforming with simple laser welds to form parts with complex shapes. Materi -
als specialists bring their most mature developments in high-strength steels since these offer thinner gauges for
removing weight. The gated development process ensures that the technologies brought to the design trades have
demonstrated scale-up and maturity required for application to the potential design. 33
With these technologies on the table, the design team (including representatives from each technology area)
can consider the forward cab section of the truck and reduce part count and simplify the design, as shown in
Figure 4-10, while still meeting requirements for crashworthiness and durability. The simpler unitized design
reduces welds significantly, thereby reducing cost and improving durability and stiffness. Moreover, the welds
that are retained are designed to be easily applied with good access for the weld machines. In addition, the turns
and twists permitted with the hydroformed substructures offer greater energy absorption for crash protection in
the lighter weight structure.
All of the improvements noted above could have been achieved without significant advances in materials
technology—assuming the steels were all hydroformable in the gauges required. The advanced high-strength steels
offer smaller gauges to achieve higher-strengths and allow greater hydroformability as well. Consequently, the
F-150 has seen a continuous improvement in weight reduction through advanced materials (Figure 4-11).
The topological design, afforded by the forming capability of the steels, provides a more modular assembly
with fewer attach points, reducing assembly time and cost. The benefits to the customer are real, measurable, and
result in a continuously improving product that is one of the most successful in its market.
33 Roy Williamson and Jon Beasley. 2011. “Automotive Technology and Manufacturing Readiness Levels.” Automotive Council of the
UK, February. Available at http://www.automotivecouncil.co.uk/wp-content/uploads/2011/02/Automotive-Technology-and-Manufacturing-
Readiness-Levels.pdf.
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102 APPLICATION OF LIGHTWEIGHTING TECHNOLOGY TO MILITARY AIRCRAFT, VESSELS, AND VEHICLES
FIGURE 4-11 Continuous improvement in materials for the Ford F-150. MS, martensitic steel; HSS, high-strength steel;
AHSS, advanced high-strength steel; UHSS, ultra high-strength steel. SOURCE: Bruno Barthelemy, Ford Motor Company,
Figure 4-11.eps
“Lightweight Technologies,” presentation to the committee, October 2010.
bitmap
4.6 CONCLUSIONS
• Lightweighting of land-based vehicles has been pursued as a means to facilitate air transport capability for
rapid deployment, improve fuel economy, more readily cross open-water barriers, and enhance battlefield
mobility and speed.
• Using aluminum alloys as primary hull materials for protection in tactical vehicles has proven effective in
meeting many vehicle requirements, including speed, maneuverability, and survivability against some threats.
• Aluminum alloy hulls have not been able to provide the desired protection against the most lethal threats.
The ever-increasing level of threat from RPGs, EFPs, shaped charges, mines, and IEDs has forced “up-
armoring” across the various classes of land-based combat vehicles, with a concomitant increase in weight.
• Titanium and magnesium have properties that could greatly advance lightweighting, but there are many
barriers to their utilization. Titanium is very expensive to extract. Magnesium is in short supply domesti -
cally and is also more expensive to form into useful product shapes than is aluminum or steel. Before either
material can be widely used in lightweighting, new manufacturing technologies are needed to improve
weldability, formability, spall resistance, fatigue resistance, and (particularly for titanium) susceptibility
to corrosion in marine environments.
• The requirement for competitive prototyping (or, with a waiver, for a single prototype) prior to the engi-
neering and manufacturing development phase can, in some instances, inhibit the use of new materials
and new designs by not allowing adequate time for testing and validation.
• Because of the great emphasis on soldier protection as well as the pressures to control costs, lightweighting
of land-based combat vehicles has proven to be more challenging than that of air and sea vehicles. Thus,
it is not surprising that, apart from aluminum-based alloys, few new materials have found their way into
extensive implementation in land-based vehicles.
