AMPTIAC is a DOD Information Analysis Center Administered 

by the Defense Technical Information Center 
As we have written numerous times within the pages of the

Quarterly, materials are the enablers of all technology: manned

space flight, supercomputers, automobiles, cellular phones, life-saving medical equipment, and even food storage and preservation are

all possible because of the development of one or more new material technologies.

One of the most frustrating things about being a material professional is constantly listening to engineers and managers repeat the

same old mantra, “we don’t have any materials problems.” Presuming

they don’t run away immediately after this admission, they eventually tell us about their problems in design, manufacturing, quality, reliability, and maintenance. What they fail to recognize is that a lot of

these are materials problems. In fact, many of the problems inherent

in the various stages of the product development cycle (the acquisition cycle in the DOD) are material-originated in nature.

More to the point, the vast majority of these assorted ‘problems’

are the direct result of design teams making poor material choices

during the pre-production phases of the product life cycle. Are these

poor choices the results of incompetence, negligence, or even malice?

Not at all – they are examples of the growing ‘understanding gap’

that has developed between the materials community (those with a

firm understanding of how materials work) and those who actually

make the decisions on what materials to use in applications. In short,

materials selection is an endangered practice: part art, part science; it

has traditionally represented a synergy of materials science and sound

design principles, drawing on an appreciation of the projected operating environment and a cognizance of how material choices impact

performance. When materials selection is performed properly, its

results are invisible to users. It’s only when some type of problem

arises (such as unexpected maintenance) do materials and their selection rationales get any attention (and unwelcome at that).

Both our lead article and the MaterialEASE feature discuss different aspects of materials selection, and the pitfalls of what happens

when improperly implemented. Whether the issue is corrosion,

hydraulic seals, or even thermal shielding, the problem is the same.

It seems that the emphasis placed on materials selection in the

design process is waning with each passing year.

This diminishing experience base is the result of several trends:

the military downsizing precipitated by the end of the Cold War

and its resultant “brain drain”; acquisition reform (relegating basic

material decisions to contractors, while concurrently eliminating a

large percentage of military specifications and standards), and a

steady decline in engineering enrollment at America’s universities.

What’s more, few engineering schools teach more than the rudiments of material selection (i.e. strength, stiffness, weight) in their

curricula, thus new engineers are ill-equipped to address the multitude of requirements incumbent in any design activity. Engineers

must discard the mindset of designing systems to perform the day

they leave the factory. Accounting for the time-dependent nature of

materials during design will do more to extend system service life

than any other post-production effort.

As our military systems are pressed into increasingly longer periods of service, the limitations of those materials selected decades ago

are becoming increasingly evident. They manifest themselves in

terms of maintenance, repairs, spare parts, and other types of

rework. A more disturbing thought yet: If current systems (designed

in the pre-reform era) are having problems attributable to materials

selection, what about future systems not yet designed or fielded?

However, the outlook is not all gloomy. Recent DOD initiatives

are reexamining the department’s role in providing guidance and

encouragement to contractors in critical enabling technologies,

materials among them. Simultaneously, there are task groups working to revive selected military specifications and standards; which

would provide program offices and contractors with needed guidance to make better design decisions. Lastly, there is a growing

assemblage of material principals (including AMPTIAC) calling for

accredited universities to revise their engineering curricula to make

the fundamentals of materials selection a required subject area in

applicable undergraduate degree programs. The objective is not to

make designers material experts; but rather to instill a basic competence, allowing them to recognize and “flag” materials issues for further scrutiny by specialists. If we as a technical specialty can incorporate that principle into the engineering paradigm, then the battle

will be more than half-won.

Ultimately, it will not be any sweeping reform or government initiative that will win the day: it will be the numerous individual

efforts made by each of us at opportune moments to “nudge” the

system. If in our own arenas, we can get designers to look beyond

basic requirements and their standard menu of ‘tried and true’ materials, then we will have done a great service for our profession, our

colleagues, and our nation.

Christian E. Grethlein

Editor-in-Chief

Editorial: It’s not easy 

being a “Materials Guy”

The AMPTIAC Quarterly is published by the Advanced Materials and Processes Technology Information Analysis

Center (AMPTIAC). AMPTIAC is a DOD-sponsored Information Analysis Center, administratively managed by

the Defense Technical Information Center (DTIC). Policy oversight is provided by the Office of the Secretary of

Defense, Director of Defense Research and Engineering (DDR&E). The AMPTIAC Quarterly is distributed to

more than 15,000 materials professionals around the world.

Inquiries about AMPTIAC capabilities, products and services may be addressed to 

David H. Rose

Director, AMPTIAC

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We welcome your input! To submit your related articles, photos, notices, or ideas for future issues, please contact:

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Editor-in-Chief

Christian E. Grethlein, P.E.

Creative Director 

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Product Sales

Gina Nash
The AMPTIAC Quarterly, Volume 8, Number 2 3

INTRODUCTION

Corrosion is a process that occurs when a material electrochemically reacts with compounds in its surrounding environment, in which the original material is chemically “consumed.”

As a material corrosively deteriorates, its material properties

likewise degrade. The results of corrosion manifest themselves

as weapon system or component failures in the worst cases, or

as unsightly blemishes in the best (Figure 1). It’s important to

realize that corrosion afflicts nearly all systems in all operating

environments. Moreover, it can significantly impact readiness

of DOD systems if excessive maintenance is required to ensure

continued safe operation. Corrosion costs can be extensive, and

for complex systems, combating its effects can take a great deal

of time and expertise to correct. Overall, the costs of combating corrosion are very high. A recent, federally funded study has

estimated the cost to the DOD at over $20B per year [1].

All too often, it is the case that corrosion begins on the drawing board, where critical design decisions will determine much

of a system’s future. In general, systems are designed to meet

performance goals where strength, weight, thermal, and electrical requirements are primary technical considerations. Other

important attributes, such as corrosion resistance and environmental compatibility, typically receive far less attention.

Without an upfront analysis to assess and address potential 

corrosion issues, problems often occur once the system has

been put into service. Correcting unanticipated corrosion 

problems during the operational phase of an asset’s lifecycle can

be very costly. In some cases it may be impossible to restore a

system to its original state without replacing problematic 

components or structures at great expense.

Developing new systems that are inherently corrosion resistant – either through selecting and using corrosion resistant

materials, or if appropriate, by employing corrosion 

preventative compounds and coatings – is one sure way to

reduce total ownership costs. To be effective though, these

considerations must be made early in the acquisition cycle.

Design and acquisition principals must recognize corrosion 

as a risk factor to be managed. 

When DOD and contractor personnel come to recognize

that corrosion is one acquisition risk factor among many

David H. Rose

AMPTIAC Director

Rome, New York

Addressing the problem of corrosion in weapons systems, support systems, and military infrastructure has historically been an 

ambitious undertaking. While most would agree that it is one of the more serious problems plaguing military systems, the unanimity

of opinion generally stops there. To various principals within the DOD, there are tremendously disparate perspectives on what 

corrosion even represents. To some, it is strictly a maintenance problem – an inevitable part of doing business. To others, corrosion is a

chemical phenomenon that occurs in most metals, but no connection is made to real-world impacts. In most cases, these views are

highly compartmentalized, lacking the ‘big picture’ of how corrosion affects the entire life cycle of DOD assets, from design through

retirement and disposal. Fortunately, the new DOD Corrosion Policy, recently instituted by Undersecretary Wynne has already started

to provide DOD personnel with a more global view of the subject. While much has already been written about what this policy 

means for reducing costs, and who is doing what to reduce corrosion (see Vol. 7, No. 4 of the AMPTIAC Quarterly), little has been

mentioned about how one goes about actually reducing corrosion in military systems. In response to this call, AMPTIAC is preparing

to publish a major, first-of-its-kind corrosion resource: A Program Management Guide for Selecting Materials. It will provide 

program managers and design engineers with guidance on how to actually select materials in the design process which will enhance 

corrosion prevention and control. As publication of this handbook may still be several months away, we offer the following teaser in 

the interim to whet your appetite. We hope you find it useful! - Editor

Figure 1. Corrosion of a Military Ground Vehicle.
4 The AMPTIAC Quarterly, Volume 8, Number 2

requiring active management, then the question will become:

what design practices are used to minimize the effects of corrosion?

The process by which designers choose materials to meet system performance requirements (typically defined by system

design specifications) is known in engineering circles as

Materials Selection. Sound material selection decisions can

greatly minimize the incidence and severity of corrosion, but

usually cannot eliminate it entirely. This is where maintenance

strategies should be formulated. However, systems with ‘corrosion-smart’ designs are far more maintainable, as corrosion

problems are more predictable and less frequent.

Due to various factors, including available time and training

deficiencies, designers often overlook steps needed to ensure

adequate corrosion resistance in their designs. To be totally

effective, designers must consider the inherent corrosion behavior of candidate materials in the prospective environment of an

application, as well as any potential interaction these materials

might have with adjacent materials, design details that could

exacerbate corrosion problems, and corrosion prevention technologies such as coatings and other compounds needed to minimize maintenance requirements. In addition, designers must

also consider other factors such as cost and appearance. If little

thought is given up-front to select the best combination of

structural materials and corrosion prevention technologies,

then a maintenance nightmare could be in the making! 

Ensuring that a system will age gracefully is the responsibility of all stakeholders in the development process including

the design activity, as well as DOD program managers and

their staff. Corrosion is a risk factor that, if mismanaged, can

result in systems far more expensive to maintain than planned

or desired. Mitigating corrosion-originated reliability and

maintenance problems certainly will affect readiness and 

operations and maintenance (O&M) budgets. If the DOD

acquisition program office and the prime contractor work

together and consider corrosion prevention and control early

in the development cycle, then total ownership costs can be

reduced from the onset. These principles apply equally well to

weapon systems (aircraft, land systems, ships, munitions, etc.),

support systems (trucks, cargo planes, supply ships, stationery

and mobile equipment, etc.) and infrastructure (buildings,

storage tanks, piping, water treatment plants, piers, etc.).

REDUCING ACQUISITION RISK AND 

TOTAL OWNERSHIP COST

As stated previously, the best way to prevent or minimize 

corrosion throughout a system’s lifecycle is to select corrosionresistant materials during the design process, followed by

employing an array of innovative corrosion prevention and

control (CPC) technologies to augment that protection. These

steps are essential to preserving systems in their original, corrosion-free state after entering service. Enhancing the materials

selection process to better highlight CPC issues offers numerous benefits; among them are improved reliability, reduced

maintenance, increased availability, improved performance and

efficiency, improved safety, increased service life, and reduced

life-cycle cost. Extending the service life of a fielded system 

is far easier and less costly to realize if excessive corrosion is 

prevented from occurring in the first place. While this undertaking may seem challenging (and more costly up-front), the

long-term benefits more than justify the investment. 

System Life Cycle

Figure 2 illustrates the life cycle of a system as it relates to component failure. Known as the ‘bath tub curve’, the figure

demonstrates the various rates at which components may fail

during their service life. Generally, this figure addresses the sum

total of all failures, including those induced by corrosion.

However, it’s reasonable to assume that a similar curve would

result from failures due to corrosion alone. 

As illustrated on the curve, the three phases of a system life

cycle consist of 1) introduction of the system into service, 2)

normal operational use, and 3) wear-out. During the introductory phase the manufacturing defects are identified and corrected, which results in a higher number of failures initially, followed by a steady decline. For systems designed with insufficient attention to corrosion, this initial phase corresponds to

the identification and mitigation of unexpected corrosion. The

bulk of the life cycle is spent as the system operates normally

(the second phase) with only routine maintenance and repairs.

It is very important to properly maintain the system during this

phase by employing corrosion preventative measures. If steps

are not taken, the system will corrode, thus accelerating the initiation of the third phase, where the number of failures and

associated maintenance actions, including component replacement, begin to increase steadily as the system reaches its maximum operational life. Proper materials selection during the

design phase, followed by the use of appropriate CPC practices

during service, will delay the onset of wear-out and enable the

affordable extension of a system’s life. 

There is a direct correlation between the number of failures

shown in Figure 2 and total ownership cost. As the amount of

failures (and resultant extraordinary corrosion preventative

measures) rise, so does the total cost. In systems designed without inherent corrosion resistance, it can be expected that 

the wear-out phase will be reached in a shorter period of time.

Consequently, an entirely new system would have to be 

purchased earlier than scheduled or alternatively, extensive

maintenance would be necessary to keep the existing system in

operation; both of which would carry significant costs. 

While it’s difficult to project a definitive return on investment resulting from increased attention to CPC issues during

system design, it is quite easy to understand intuitively that a

system designed with inherent corrosion resistance will last

Figure 2. Classic System Life Cycle.

Time Since Introduction

N

Normal Operations

umber of Failures

Standard

Wearout

Wearout with

enhanced corrosion

resistance

Introduction
longer than one without. Figure 2 addresses both situations,

with the dashed lines indicating a longer service life for the 

system designed with corrosion resistance in mind. Take for

example a hypothetical weapon system that, due to its inherent corrosion resistance, has a life span that is two years longer

than a similar (baseline) system. If the baseline life was ten

years and the total acquisition cost were $1B, the return on

investment due to delayed acquisition of a follow-on system

would be $200M. In reality, the cost savings would be even

higher than this projection, because this example totally

ignores O&M savings. 

Mitigating unexpected corrosion can be very expensive, both

in terms of direct cost and its impacts on readiness. If a system

were designed with corrosion resistance built-in, less maintenance would be required, thus reducing O&M expenditures

while increasing system availability at the same time. It easily

can be seen that extending the service life of a system before it

reaches the wear-out phase is extremely beneficial in terms of

cost avoidance and that the savings can be substantial, especially if the acquisition of a new system is delayed.

Another way of considering the influence of CPC on total

ownership costs is displayed in Figure 3. It depicts acquisition

costs versus time for two hypothetical systems; one designed

with inherent corrosion resistance and the other without. As

shown in the figure, the acquisition costs for the system

designed with enhanced corrosion resistance will be higher (due

to increased engineering time and potentially more expensive

materials). However, over the system’s life these costs will be

more than recovered in O&M cost savings, such that the total

ownership costs of the corrosion resistant system will be lower

than the baseline system.

Managing the Risk Factor

If one accepts the premise that corrosion is a risk factor – that if

poorly managed it will increase total ownership costs – then one

might ask: how do you manage the risk? Developing a new system

with the lowest total ownership cost can only

be achieved if proper oversight and attention

are paid to material selection during the design

process. Currently, there are no available management tools that can calculate the return on

investment that would result from increased

attention to CPC issues during the design

phase. As previously stated, it is intuitively

obvious that controlling corrosion will

increase readiness through greater availability

and reliability coupled with less maintenance.

The challenge for program managers (and

their contractors) is accounting for the risk of

corrosion so that these benefits can be realized

while minimizing total ownership costs. 

Management tools (software) which can

quantify the total ownership cost savings due

to improved CPC strategies are not presently

available, nor are there any formal procurement processes accounting for CPC efforts.

Prior to the implementation of the

Acquisition Reform Initiative, military 

specifications and standards codified the lessons learned from

observations of failures and correctable problems on legacy systems. These documents included substantial CPC information.

When the majority of these documents were rescinded in the

early 1990’s, the increased risk of corrosion, and the associated

impact on readiness and total ownership cost, was not 

considered. Similar to other risk-related activities such as 

survivability, manufacturing, and reliability; CPC awareness

and planning would tremendously benefit if risk analyses were

conducted during the system engineering process. Accounting

for and managing the risk associated with corrosion prevention

and control will undoubtedly reduce ownership costs.

PROPER MATERIALS SELECTION 

ENSURES CORROSION RESISTANCE

A thorough and realistic consideration of corrosion prevention and control during the materials selection phase of the

design process is key to developing systems that will age in a

predictable and affordable fashion. The process of materials

selection is not used solely to choose the material to build a

structure or component. Rather, it is used to select a system of

materials that together provide the necessary properties to meet

performance requirements. Furthermore, a successful material

selection effort will help to ensure that a system will continue

to perform to specification over time, demonstrating its robustness against aging phenomena, such as wear, fatigue, and 

especially corrosion.

While materials selection is a crucial part of the design

process, it can lead to future problems, especially if the designer focuses upon meeting performance requirements with little

regard to maintenance needs. The use of CPC methods must

be planned, and not left as an afterthought, or else it is highly

likely that maintenance problems will plague the system

throughout its service life. CPC methods include an array of

technologies; such as chemical treatments, paints, platings, and

cathodic protection. 

The AMPTIAC Quarterly, Volume 8, Number 2 5

Figure 3. Total Ownership Cost Comparison.

Improved Corrosion

Resistance Design

Acquisition Operations & Maintenance (O&M)

Time

Life Cycle Costs

Baseline

O&M Savings

Realized from

Corrosion-Resistance

Design

Added Upfront

Investment for

Corrosion-Resistance

Design
6 The AMPTIAC Quarterly, Volume 8, Number 2

Impact of the Corrosive Environment

Planning for the graceful aging of a structure or system during

materials selection requires a firm understanding of its operating environment. The word environment as used here describes

the conditions a system may be exposed to while in service. For

example, a ship floating in the ocean is considered to be in a

marine environment, while turbine blades experience a high

temperature environment inside a jet engine during operation.

In reality though, things are not quite that simple, because 

systems experience a variety of simultaneous environmental

conditions. Systems often contain many fluids and chemicals

that are necessary for its components to operate, but some of

these can be very corrosive and cause a material to degrade. For

instance, designers must consider cleaning chemicals and

hydraulic fluids as sources of contamination that can cause

a material to corrode. There are many other materials and 

contaminants that exist within the operational environment that

can influence the rate at which a structure or component 

corrodes. Designers must take a step back and gain a firm understanding of all environmental factors that can influence corrosion

before selecting the construction materials. Again, it’s important

to note that an environment isn’t a single condition, but rather is

a combination of factors which work in concert, such as operating temperature and humidity, salinity, and mechanical loading.

Other contributing influences include chemicals, fuel, pollutants, solar radiation and biological organisms.

Having a firm understanding of the operational environment

is crucial to designing a corrosion resistant system. However

there are other environmental conditions that occur during

storage or transportation that must also be considered. As

Figure 4 attests, systems can experience corrosive environments

during transportation that are far more severe than their 

operational conditions, yet designers can easily overlook the

threat of transportation-induced corrosion, since systems 

experience only brief periods being transported from one part

of the globe to another. Storage conditions must also be 

analyzed to determine whether they may damage or degrade a

system. Some weapons, like air-launched missiles, are stored in

controlled-humidity containers, which help keep these systems

in their pristine, uncorroded state. Other weapons, like the

gravity bombs shown in Figure 5, may be exposed to extremely high humidity levels while in their protective shelters. As

shown in this figure, these weapons can experience severe 

corrosion, so much so that they may become useless and have

to be replaced at a significant cost.

The Importance of Corrosion Testing 

and Information Resources

One of the reasons why selecting corrosion-resistant materials

is a challenging process is that corrosion data aren’t usually

available in forms that are immediately and directly related to

the respective environment of the system or structure. Because

of the extremely large number of available materials, (including

variants subjected to different fabrication processes, and environmental conditions), it is too costly and nearly impossible to

test all the combinations of materials and environments. The

result is that it can be very difficult to find completely relevant

data to substantiate decisions. 

Materials scientists over the years have devoted significant

resources to corrosion testing and analysis. Accelerated testing

using salt spray or controlled humidity and temperature

chambers are often used to investigate a material’s potential to

corrode or how well a CPC technology will function.

Unfortunately, these tests don’t replicate true operational 

conditions, nor do they account for the synergistic effects of

other contributing factors such as atmospheric pollutants or

chemical exposure. This is what makes conducting realistic

corrosion analyses so challenging.

Perhaps the best source of information to address both the

expected operational environment and the potential for corrosion problems is to consult the existing literature. Such a review

can determine whether there is documented field service expeFigure 4. Various Army Systems Exposed to the Marine

Environment During Transportation.

Figure 5. Munitions Are Frequently Stored in High Humidity

Environments.
The AMPTIAC Quarterly, Volume 8, Number 2 7

rience on a legacy system similar to the one being designed.

Natural aging information for a system or structure operated

within the same (or similar) environment to one being

designed can provide some excellent insight as to what to

expect. In addition, if materials used on the older system have

shown the potential to corrode, then there are some lessons

learned that can be used to preclude incorporation of problematic materials in new systems.

It can be tempting to minimize predicted corrosion problems

by relying solely upon legacy technology. It is common practice

in industry to build new systems from the same materials as

their predecessors. In some situations, this may be an entirely

acceptable approach, but it is fraught with the risk of overlooking new materials and technologies, thus representing a lost

opportunity. New materials are often innovative in nature,

allowing a designer to exploit their improved properties to provide performance advantages over a legacy or competing 

system. For situations where no laboratory or in-service data are

available, designers shouldn’t be deterred from the use of new

materials. The known environmental conditions within an

existing system of similar nature can be used as a guide to 

project whether future corrosion problems can be expected 

for new materials. Such an assessment can lead engineers to

develop test protocols which will quantify the degree of corrosion resistance inherent in the new material. Additionally, it

may be possible to employ effective CPC strategies with a new

material to provide the necessary corrosion protection.

DESIGN APPROACHES TO ENSURE 

CORROSION RESISTANCE

There are other considerations in the design process beyond

selecting corrosion resistant materials and associated CPC

technologies. Even with proper materials selection, designers

can unintentionally exacerbate the likelihood of corrosion by

creating conditions that favor its occurrence. For example, by

not including drainage holes in a structure subjected to rain 

or wash water, liquid can become trapped and accelerate the

corrosion process in an entirely unanticipated location and

fashion. Other considerations include using materials that

won’t wick moisture. It’s important to avoid, if at all possible,

the use of wood, paper, cardboard, open cell foams, and sponge

rubbers in systems that operate in wet environments, or in

environments that have a high humidity. These materials tend

to retain water and consequently function as a reservoir for

adjacent materials that may be susceptible to corrosion.

Another significant design consideration involves junctions

where two adjacent components come together. Known as 

faying surfaces, these areas can see sufficient relative movement

between each other so that protective surface layers at the joint

may wear away, exposing the underlying material directly to 

a corrosive environment. To protect faying surfaces, proper

sealing materials (tapes, films, sealing compounds) and 

primers must be employed.

The intimate contact of two adjacent materials can be the

causative factor for another corrosion mechanism, galvanic 

corrosion. One of the eight main forms of corrosion, it results

when dissimilar metals come in contact with each other and are

exposed to corrosive conditions. One of the best ways to prevent these materials from corroding further is to electrically

insulate them through the use of coatings at the interface

between them. A nonconductive coating will prohibit electrons

from moving between the two materials, thus stopping the oxidation process.

Another important aspect is to design the system or structure

for maintenance access. It is vitally important that inaccessible

areas be minimized so that maintenance personnel can both

inspect the areas for corrosion and reapply CPC compounds 

or replace components if necessary. For those situations 

where inaccessible areas are unavoidable, then it is even more

important that an upfront analysis be conducted to ensure 

that proper corrosion resistance can be sustained to preclude

unanticipated and extremely costly damage after the system is

fielded. When analyzing maintenance access requirements,

designers should consider that nondestructive evaluation techniques will be needed to detect hidden corrosion at some 

point during the operational use of the system. The structure

must be designed to accommodate the necessary testing 

apparatus to preclude hidden corrosion from creating an

unsafe or unreliable system.

DESIGN PITFALLS 

As it relates to corrosion prevention and control, there are 

several pitfalls that can and do occur periodically.

Unfortunately, designers seldom have a strong background or

understanding of corrosion. Most view corrosion as a single

process; and thus are unaware that highly accelerated, localized

corrosion mechanisms even exist. It is also a mistake to assume

that two seemingly identical materials that may have the same

composition (relative amounts of elemental constituents) but

have been processed differently (different heat treatments 

for example), would exhibit the same corrosion rates. The

potential for a material to corrode is often strongly influenced

by the processes used to create it.

Another pitfall is that characteristic relationships used to 

predict corrosion rates are inappropriately applied. A designer

who lacks the necessary understanding of corrosion may 

consider all corrosion phenomena a single process, and thus

may be prone to misapplying an equation developed for a 

different corrosion form. For example, a well-understood 

and predictable process such as uniform corrosion has been

characterized by several constitutive equations which predict

degradation rates. Unfortunately, unsuspecting engineers

could mistakenly apply such equations to a highly accelerated

localized form of corrosion like pitting. Localized forms of corrosion, like pitting or crevice corrosion, experience extremely

high corrosion rates in very small and often hidden locations.

The rates of corrosion for these mechanisms vary widely from

one case to another; hence they don’t lend themselves at all 

to predictive methodologies. Engineers not understanding 

the differences in corrosion mechanisms can and often do 

misapply equations which results in a strong potential for

unexpected failures.

Although experimental data concerning corrosion abounds,

it is often in inconsistent formats. Combined with the fact 

that corrosion rates are highly dependent upon usage environments, material composition, and processing history, a
8 The AMPTIAC Quarterly, Volume 8, Number 2

common mistake is to utilize data inappropriately or incompletely. A designer with the right intentions can easily misuse

data to substantiate a design decision that may lead to entirely

wrong conclusions. Another contributing factor is that corrosion data, especially that relating to natural aging, is scattered

and available from many different sources. This type of data 

is seldom consulted, and consequently design decisions don’t

fully benefit from the lesson’s learned. The net result in both

cases is that a system, structure or component will possess 

far worse corrosion characteristics than initially believed or

desired.

FINDING THE RIGHT BALANCE

For the uninitiated, this discussion might give the impression

that corrosion cannot be prevented without conducting

painstaking and extraordinary measures. It is important to

point out that the goal of materials selection isn't to eliminate

corrosion in all circumstances, but to manage and minimize it.

The challenge to effective corrosion prevention and control 

is to strike a balance to ensure adequate inherent corrosion

resistance and ease of maintenance while at the same time 

balancing cost. Cost includes not only the design time required

to analyze and select the most appropriate material, but also 

the material cost itself. In general, materials that are inherently

corrosion-resistant are typically more expensive than those that

are not. During the design process, engineers must choose

materials that provide the best combination of performance,

including corrosion resistance, that will ensure that systems will

adequately perform their function over the intended lifespan

within fiscal constraints.

Reducing risk on new systems has to be an important concern for all stakeholders in the acquisition process. This risk can

take several forms, all of which can seriously impact readiness,

especially if unanticipated (but completely avoidable) corrosion

problems occur during service. Some of the biggest problems

experienced by Program Offices are unexpected maintenance,

reliability problems, and premature wearout. Having to replace

components or even entire systems because they experience

unexpected corrosion is clearly an unaffordable prospect that

significantly impacts total ownership costs as well as the ability

of our troops to effectively accomplish their military objectives.

Even more important is that hidden corrosion can and will

cause unexpected failures that can be catastrophic in nature.

Correcting these problems before they occur, by way of the

materials selection process, is the best strategy for the long run.

REFERENCE

[1] G. Koch, M. Broyers, N. Thompson, Y.P. Virmani, J. Payer,

Corrosion Costs and Preventative Strategies in the United States

(FHWA-RD-01-156) 

NIST recently announced the introduction of a new Standard

Reference Material (SRM) for Vickers Hardness of Ceramics

and Hard Metals: SRM 2831. Vickers hardness is an important

property for ceramics,

carbides, and hard 

metals. It is increasingly

being incorporated into

materials specifications

for cutting tools, silicon

nitride ball bearings,

and ceramic implant

materials. Although

Vickers hardness reference blocks made of

steels and softer metals

have been readily available for many years,

there have been none

available for harder

materials. The SRM is a

disk of a commercial

tungsten carbide with

12% cobalt binder phase. Each disk has five 9.8 N indentations

made in the center of a polished face. The disks have highly

polished surface and excellent hardness uniformity. Indentations are sharp and well-defined in this fine-grained material.

The disks are individually certified for the average diagonal

length (nominally 35.0 mm) and the average hardness 

(nominally 15.0 GPa or 1,530 N/mm2). Two international

round robin studies used prototype SRM 2831 disks to good

advantage and verified

the suitability of the

tungsten carbide. SRM

2831 supports ASTM

standards C 1327, E

384, and E 92, as well as

ISO standards 14705

and 3878, CEN ENV

843-5, and JIS R 1610.

For additional information, contact George

Quinn, the technical

point of contact at (301)

975- 5765 (george.quinn

@nist.gov) or the NIST

SRM Customer Service

at (301) 975 6776

(srmorder@nist.gov), 

or visit the SRM Home

page http://ts.nist.gov/ts/htdocs/230/232/232.htm and enter

2831. The new SRM 2831 will complement the companion

silicon nitride SRM 2830, Knoop Hardness of Ceramics,

which is also available off the shelf. 

Standard Reference Material 2831: Vickers Hardness of Ceramics and Hard Metals
The AMPTIAC Quarterly, Volume 8, Number 2 9

SSPC MISSION

Founded in 1950, SSPC is a non-profit association whose mission is to advance the technology and promote the use of protective coatings for the preservation of industrial, marine, and

commercial structures, components, and substrates. SSPC

strives to achieve its mission through various products, services,

and information resources, including standards development,

publications, training courses, certification programs, conferences, and an expanding range of online services.

SSPC STANDARDS 

Since its inception, SSPC has been a leading source of standards,

guides, specifications and other consensus documents on surface preparation, coating selection

and performance, coating

application, and

other materials,

technologies and

practices. Foremost

among these are:

SSPC-SP 5 Surface Preparation Standards 

For White-Metal

SSPC-SP 10 Surface Preparation Standards 

For Near-White Metal

SSPC-SP 7 Brush-Off Standard

SSPC-SP 6 Commercial Blast Cleaning Standard

SSPC-PA 2 Measurement Of Dry Coating Thickness 

With Magnetic Gages

SSPC-Guide 6 Guide For Containing Debris Generated

During Paint Removal Operations

SSPC-SP 12 Surface Preparation And Cleaning Of Metals

By Waterjetting Prior To Recoating

(also NACE No. 5)

SSPC PUBLICATIONS

SSPC’s offers a wide variety of publications, many of which are

now industry standards. Most notably, SSPC’s two-volume

painting manual has become one of the protective coatings

industry’s most well know and most widely used reference

books. SSPC publications address a panorama of topics – painting procedures, materials, and equipment; surface preparation

and coating work on steel and concrete; corrosion basics for

coatings personnel, cleaning and coating concrete, and spray

application standards and practices.

SSPC VISUAL STANDARDS 

AND REFERENCE PHOTOGRAPHS

In addition to the written surface preparation standards, SSPC

has also developed a series of supplemental visual standards and

reference photographs. Examples include:

SSPC-VIS 1 Dry Abrasive Blast Cleaned Steel

SSPC-VIS 2 Visual Rust Standard

SSPC-VIS 3 Power- And Hand-Tool Cleaned Steel

As a follow-up to our recent special issue on Corrosion (Vol. 7, No. 4), we wanted to bring to the attention of our readers another leader in

the corrosion prevention and control field: SSPC – The Society for Protective Coatings. SSPC enjoys a long heritage of achievement and service in protecting the nation’s durable assets from the effects of corrosion. - Editor
10 The AMPTIAC Quarterly, Volume 8, Number 2

SSPC-VIS 4/ Steel Surfaces Cleaned By Waterjetting

NACE VIS 7

SSPC-VIS 5/ Steel Surfaces Cleaned By Wet Abrasive 

NACE VIS 9 Blast Cleaning

Each of these contains a set of bound full-color reference 

photographs of painted and/or unpainted rusted steel before

and after cleaning in accordance with certain SSPC surface

preparation specification.

SSPC TRAINING COURSES

SSPC offers a wide variety of training courses ranging from

comprehensive overviews to in-depth technical training. Some

examples are:

SSPC-C1 Fundamentals of Protective Coatings for Industrial 

Structures (in-class or online e-course)

SSPC-C2 Specifying and Managing Protective Coatings 

Projects

SSPC-C7 Fundamentals of Dry Abrasive Blast Cleaning

SSPC CERTIFICATION PROGRAMS

SSPC offers several nationally recognized independent painting

contractor certification programs. Each program is based on

consensus standards developed by a diverse committee of

industry professionals. 

SSPC-QP 1 Certifies contractors who perform surface

preparation and industrial

coating application on

steel structures in

the field

SSPC-QP 3 Certifies a contracting company’s

ability to perform

surface preparation

and protective coating

application in a fixed shop

facility

SSPC CONFERENCES

SSPC’s next major conference will be The Paint and Coatings

Exposition 2005 (PACE 2005) will be held in January 2005 at

the MGM Grand Hotel and Conference Center in Las Vegas,

Nevada; featuring a series of technical events, committee meetings, seminars, and workshops, as well as a trade show of over

300 exhibits.

SSPC ONLINE

Since 1997, SSPC Online has provided information on SSPC

products and services to SSPC’s internet users. The site features

a wide variety of coatings-related information resources, useful

tools, an archive of papers and technical presentations, an interactive members’ directory, an e-commerce site, online registration and enrollment forms, regulatory and coatings industry

news, and more. For more information, visit SSPC online at

http://www.sspc.org.
THE BASICS

Elastomers vs. Rubbers

Elastomers are a class of materials with properties quite distinct from all

other solid materials. They are highly elastic; capable of being stretched

many times their original length, and upon release, quickly revert to

their original state. Their ability to deform significantly, and hence conform to the geometries of adjacent surfaces, makes them ideal for use in

seals, sealants, gaskets, and shock absorbing applications. As the roots of

the word imply, the term elastomer, a contraction of elastic polymer,

refers to any polymeric material exhibiting highly elastic behavior.

International industry usually regards elastomer as an American term,

but even in the US, rubber remains the predominant lay term both in

standards and in factory practice[1].

Elastomers may be obtained from nature or via synthesis. Natural

rubber is any elastomeric material formed from a natural source of

latex†. The most common source is the Hevea tree (Hevea Brasiliensis),

found primarily in tropical regions[2]. Once the latex is extracted from

the “rubber tree,” it is coagulated and further processed to fabricate the

desired rubber product. Synthetic elastomers may be formulated from

either organic or inorganic sources. The organic elastomers, generally

referred to as synthetic rubbers, are typically derived from petroleum byproducts. The inorganic synthetics are based on silicone chemistry.

Elastomer Chemistry

Polymers and Elastomers The term polymer is Greek in origin,

meaning “many units.” Elastomers are a subclass of polymers – their

main distinction from other polymers is their remarkable elasticity and

deformability; upwards of 400 to 600%, as opposed to 2-5% for other

polymers. Polymers (and elastomers) may either be thermoplastic or

thermosetting in nature. Thermoplastic polymers are composed of 

serpentine, high-molecular-weight strands, with individual units

linked by covalent bonds (Figure 1). Consequently, thermoplastics tend

to be soft and ductile, and with sufficient heat, they will become softer

The AMPTIAC Quarterly, Volume 8, Number 2 11

Material EASE

ELASTOMERIC SEALS 101 – A BRIEF TUTORIAL

This underrated group of materials is far more important than you might think

Christian E. Grethlein, P.E.

Benjamin D. Craig

Richard A. Lane

AMPTIAC

Rome, New York

26AMPTIAC

In material circles, it doesn’t take much prodding to get a vigorous discussion going about high-performance materials, or one

of the many emerging material technologies. However, bring up the subject of ‘rubber’, and it tends to produce more eye-rolling

than genuine interest. Elastomers (as they’re more properly known) are one of the most critical non-structural 

material in vehicles, systems, and some structures, yet are also one of the least considered during design. Unfortunately, 

such oversights can have catastrophic or even fatal consequences when elastomeric seals fail in service; bringing unwanted 

levels of attention to previously ignored problems. This issue of MaterialEASE provides an overview of elastomer basics, and will

give the reader a better appreciation of the importance of these materials. For readers who would like to learn more about 

elastomers, AMPTIAC has published a State of the Art Report, Elastomeric Materials for Static and Dynamic Seal Applications

(AMPT-30), which is available for sale by phone or through our website, http://amptiac.alionscience.com. - Editor

Figure 1. Morphology of a Thermoplastic Polymer.

Figure 2. Morphology of a Thermosetting Polymer.

Some thermoplastics have cyrstalline

regions where chains fold over and

bond to themselves.

Thermoset polymers are

complex, heavily

crosslinked lattices,

assuming a number of

different forms.

Van der Waal forces create light

secondary bonds between strands.

‘Crystalline Regions’
12 The AMPTIAC Quarterly, Volume 8, Number 2

Material EASE

and may be processed more than once. Most physical, mechanical, and

electrical properties of a polymer are highly dependent on its average

molecular weight.

Thermosetting monomers are typically multibranched molecules,

meaning that when the polymerization reaction begins, the individual

monomers (low weight molecules) link together, but not in a 1-dimensional manner like thermoplastic strands, but in a 2- or 3-dimensional manner, forming a lattice of covalently bonded chains. Each lattice

is a molecule unto itself and adjacent lattices may crosslink to form an

even larger molecule (Figure 2). Long-term exposure to high temperatures will continue the polymerization reaction, making the polymer

denser, tougher, and stronger. Thermosets do not melt, but if heated to

a sufficiently high temperature, they will start to decompose.

Chemistry of Natural Rubber The extracted latex product from 

Hevea rubber plants is 2-methyl-1,4-butadiene, more commonly

known as Isoprene (Figure 3). The elastomer is formed when isoprene

polymerizes into a chain molecule. The most common configuration 

of isoprene elastomer is cis-isoprene, and is the one referred to as 

natural rubber.

Effects of Vulcanization Charles Goodyear’s inadvertent discovery of

the vulcanization process changed the future of rubber overnight.

Heating raw isoprene with trace amounts of sulfur (plus an accelerator) causes the sulfur to form short linear sulfide chains, which in turn

bond to various sites along the polyisoprene chains. The sulfur crosslinks are primarily responsible for the highly elastic nature of refined

natural rubber. Thus, vulcanization converts it from a dimensionally

unstable, viscoelastic material to an extremely stable elastic material.

Synthetic Rubbers Global conflicts and periodic supply shortages 

catalyzed the development of the first synthetic analogs to natural 

rubber. Since the 1920s, a number of “synthetic rubbers” have been

introduced, each a variant of the basic isoprene elastomer. Beyond

establishing more reliable supplies, many of the synthetics were 

developed to enhance one or more elastomer properties – usually

expanding operating temperature range, or improving chemical resistance. Carbon-based synthetics differ from isoprene by the addition or

substitution of different atoms or functional groups along the polymer

chain’s backbone. Table 1 provides definitions of the various types of

synthetic elastomers. The first inorganic elastomers were synthesized

near the start of World War II. These organo-silicon compounds, or

Silicones, represent a whole new branch of synthetics, and feature several qualities that make them superior to their organic counterparts.

Chemistry of Silicones Silicone polymers are fundamentally structured the same as organic polymers but employ silicon (Si) instead 

of carbon as the backbone of the chain. More precisely, 

silicone’s backbone is comprised of alternating Si and O atoms (polysiloxane). The oxygen bonds between the Si atoms provide 

molecular stability by spacing the Si atoms (which are much larger

than C atoms) beyond the range of their mutual repulsion.

Polydimethylsiloxane is the most common silicone monomer used 

to create silicone elastomers (Figure 4).

Elastomer Thermodynamics

The thermodynamics of elastomers are rather unique compared to

other solid materials. Typically, most solids expand when heated, but

elastomers under tension actually contract when heated. This behavior

is known as the Gough-Joule effect, and is due to their internal structure. In a relaxed state, the molecules of an elastomer are ‘tangled’

around themselves and adjacent molecules. When stretched, they

untangle, becoming more ordered[3]. In effect, their relative state of

entropy decreases as they are extended (Figure 5). The thermodynamic

Figure 4. Polydimethylsiloxane (Silicone) Elastomer.

Figure 3. Polymerization of Polyisoprene (Natural Rubber).

Isoprene Monomer Polyisoprene Elastomer

Repeated Monomer Unit 

(n is typically greater than 300)

Silanol Groups terminate

elastomer chains
behavior of all materials dictates that the relative state of entropy

increases upon heating and decreases upon cooling. Therefore, when

an already-extended elastomer (in a low entropy state) is heated, it

must contract in response to the relative increase in entropy. Similarly,

an elastomer in a relaxed state (high state of entropy) will expand

when cooled.

ELASTOMERS FOR SEAL APPLICATIONS

Elastomers are available in both natural, and synthetic forms; typically composed of polymers with a macromolecular structure. All

elastomers are organic (carbon-based) polymers with the exception of

silicones and fluorosilicones. Seal materials have been classified in

ASTM Standard D1418 according to their chemical composition with

letter designations[2], and are presented in Table 1.

Material Comparisons

The following tables summarize and compare the important properties

of the various elastomers. Table 2 provides operating temperatures and

recommended uses of the materials. Table 3 lists the relative costs of

elastomeric materials. Table 4 contains relative performance in

response to environmental factors. 

For more information, AMPTIAC’s State of the Art Report,

Elastomeric Materials for Static and Dynamic Seal Applications,

presents comprehensive tables of chemical resistance for all major

elastomer classes evaluated for a variety of chemicals.

A DVANCED M A TERIALS AND P ROCESSES T ECHNOLOGY

The AMPTIAC Quarterly, Volume 8, Number 2 13

AMPTIAC

Table 1. Elastomer Seal Classifications[2].

M Class: Elastomers having a saturated chain of the polymethylene type

ACM Copolymers of ethyl or other acrylate and a small amount of monomer which facilitates vulcanization.

EPDM Terpolymer of ethylene, propylene, and a diene with the residual unsaturated portion of the diene in the side chain.

CFM Polychloro-trifluoroethylene

FKM Fluoro rubber of the polymethylene type having substituent fluoro and perfluoroalkyl or perfluoroalkoxy groups 

on the polymer chain.

FFKM Perfluoro rubbers of the polymethylene type; having all substituent groups on the polymer chain - either fluoro, perfluoroalkyl, 

or perfluoroalkoxy groups.

FEPM Copolymer of tetrafluoroethylene and propylene.

O Class: Elastomers having oxygen in the polymer chain

ECO Ethylene oxide (oxirane) and chloromethyl oxirane (epichlorohydrin copolymer)

R Class: Elastomers having an unsaturated carbon chain

BIIR Bromo-isobutene-isoprene rubbers

CIIR Chloro-isobutene-isoprene rubbers

CR Chloroprene rubbers

IIR Isobutene-isoprene rubbers

NBR Isoprene rubber, natural

SBR Styrene-butadiene rubbers

Q Class: Elastomers having silicon in the polymer chain

FVMQ Silicone elastomer having fluorine, vinyl, and methyl substituent groups.

PMQ Silicone elastomers having methyl and phenyl substituent groups.

PVMQ Silicone elastomers having methyl, phenyl, and vinyl substituent groups.

MQ Silicone elastomers having only methyl substituent groups, such as dimethyl polysiloxane.

T Class: Elastomers having sulfur in the polymer chain

EOT A rubber having either a -CH2-CH2-O-CH2-O-CH2-CH2- group or -CH2-CH2- group or occasionally an -R- group, 

where R is an aliphatic hydrocarbon between the polysulfide linkages in the polymer chain.

U Class: Elastomers having carbon, oxygen, and nitrogen in the polymer chain

AU Polyester urethane.

EU Polyether urethane.

Not shown:

Z Class: Elastomers having phosphorous and nitrogen in the polymer chain.

N Class: Elastomers having nitrogen in the polymer chain.

Elastomer in a Relaxed State:

• Less Ordered Molecules

• Expands When Cooled

Elastomer in an Expanded State:

• More Ordered Molecules

• Shrinks When Heated

Figure 5. Typical Structure of an Elastomer.
Table 2. Common Trade Names and Uses for Basic Types of Elastomers[4].

Elastomer Trade Names and Manufacturers* Temperature Range Compatible Fluids and Lubricants

Nitrile or Buna N

(NBR) 

Chemigum

Paracril

Hycar

Krynac

Ny Syn

Goodyear Tire & Rubber

Uniroyal Chemical Co.

Goodrich Chemical Co.

Bayer Chemical Corp.

DSM Copolymer, Inc.

-54 to 135°C

(-65 to 275°F)

Synthetic hydrocarbons MIL-H-83282, MIL-H-46170

Petroleum oils MIL-H-5606, MIL-H-6083

Water

Silicone greases and oils

Di-ester-base lubricants (MIL-L-7808)

Ethylene-glycol-base fluids

SBR

(Buna S or GRS) (Too numerous to list)

-54 to 107°C

(-65 to 225°F)

Automotive brake fluid

Alcohols (low molecular wt.)

Water

Butyl Rubber

(IIR)

Polysar Butyl

Bucar Butyl

Exxon Butyl

Bayer AG Chem/Rubber

Columbia Carbon Co.

Exxon Chemical Co. USA

-54 to 107°C

(-65 to 225°F)

Phosphate-ester type hydraulic fluids (Skydrol, Fyrquel 

[Cellulube], Pydraul)

Ketones (MEK, acetone)

Silicone fluids and greases

Polyacrylate 

Rubber (ACM)

Cyanoacryl

Hycar

Krynac

Thiacril

American Cyanamid Co.

B. F. Goodrich Co.

Polysar Ltd.

Thiokol Chemical Corp.

-18 to 177°C

(0 to 350°F)

Chloroprene

Rubber

(Neoprene, CR)

Neoprene

Butaclor

PeroTexneoprene

E. I. duPont de Nemours

Enichem/Petrochem.

Petro-Tex Chemical Co.

-54 to 149°C

(-65 to 300°F)

Refrigerants (Freon, NH3)

High-aniline-point petroleum oils

Mild acid resistance

Silicate ester lubricants

Ethylene Propylene

Rubber (EPM) and

Ethylene Propylene

Diene Rubber

(EPDM)

Nordel

Royalene

Vistalon

Epcar

Epsyn

E. I. duPont de Nemours

Uniroyal

Exxon Chemical Co. USA

B. F. Goodrich Co.

Copolymer Rubber & 

Chemical Corp.

-54 to 149°C

(-65 to 300°F)

Phosphate-ester-base hydraulic fluids (Skydrol, 

Fyrquel [Cellulube], Pydraul)

Ketones (MEK, acetone)

Alcohols

Automotive brake fluids

Silicone (SI) Silastic

(various)

(various)

Dow Corning Corp.

General Electric

Union Carbide & Carbon

-115 to 121°C

(-175 to 250°F)

High-aniline-point oils

Dry heat

Chlorinated diphenyls

Military aircraft fuels JP-4, JP-5, JP-8

Polyol ester-type hydraulic fluids

Sulfur-bearing chemicals

Hypoid gear lubricants

Aliphatic solvents

Mineral oils

Aliphatic solvents

Aromatic fuels

Motor oils

Fluorosilicone (FSI) Silastic L.S.

Sylon

Dow Corning Corp.

3M

-62 to 177°C

(-80 to 350°F)

Military aircraft fuels JP-4, JP-5, JP-8

Epichlorohydrin

Rubber (CO, ECO)

Herclor

Hydrin

Hercules, Inc.

B. F. Goodrich

-54 to 135°C

(-65 to 275°F)

* Many of these trade names are registered trademarks of their manufacturer

Polyurethane

Rubber (AU, EU)

Adiprene

Cyanaprene

Disogrin

Elastothan

Formez

Pallathane

Vibrathane

Uniroyal Chemical

American Cyanamid Co.

Freudenberg-NOK

E. I. duPont de Nemours

Uniroyal

Thiokol Chemical Corp.

Uniroyal 

-54 to 93°C

(-65 to 200°F)

Fluorocarbon

Rubber (FKM) and

Perfluorocarbon

Rubber

Viton

Fluorel

Kalrez

Kel-F

E. I. duPont de Nemours

Minnesota Mining & 

Mfg. Co. (3M)

29 to 204°C

(-20 to 400°F)

Synthetic hydrocarbons MIL-H-83282, MIL-H-46170

Petroleum oils MIL-H-5606, MIL-H-6083

Di-ester-base lubricants MLO 8200, MLO 8515, OS-45

Silicone fluids and greases

Halogenated hydrocarbons (carbon tetrachloride, 

trichloroethylene)

Selected phosphate ester fluids

Acids

Chlorotrifluoroethylene (CTFE)

14 The AMPTIAC Quarterly, Volume 8, Number 2

Material EASE
A DVANCED M ATER IALS AND P ROCESSES T ECHNOLOGY

The AMPTIAC Quarterly, Volume 8, Number 2 15

AMPTIAC

SEAL TYPES 

Seal Designs

Seals can be categorized into two groups, depending upon their 

application. Static, or gasket materials are in stationary systems; while

dynamic, or packing seals are in moving systems, such as pistons.

Systems are designed so that the seal material is put in compression

when assembled (Figure 6). The stiffness of the seal in shear and the

pressure applied on the adjacent walls, prevent fluids from leaking past

the seal. The higher the compression, the higher fluid pressures that

can be contained by the seal.

Static Seals Static seals can be produced in two different ways. They can

be molded into specific shapes prior to assembling the system, or they

can be formed in place. The formed-in-place seals have the advantage

of filling in the total surface area of the surrounding walls. This reduces

the number of small gaps between surfaces, limiting potential leakage.

The disadvantage is that excessive motion in the system can break the

seal, resulting in leakage. Gaskets manufactured into sheets and cut to

size are the typical seals used in automotive applications. Pre-molded

O-rings used in static applications are mounted in a groove called a

“gland” and are placed in compression upon assembly. 

Dynamic Seals A dynamic seal is always mounted in a gland. It 

may be in motion itself for “inside” packings, or may be stationary 

for “outside” packings, as seen in Figure 7. O-rings are the most 

widely used design, although additional seal geometries used include 

T, U, and V-shaped rings. The O-ring design is usually the first design

considered due to a number of factors. Their advantages include[6]:

• Simplicity • Ruggedness

• Low cost • Ease of installation

• Ease of maintenance • No adjustment required

• Low distortion of structure • No critical torque in clamping 

• Small space requirement • Reliability

• Effectiveness over wide pressure and temperature ranges.

V-shaped rings are used in systems where any leakage is critical.

They are also favored where the seal material is to be replaced without

complete disassembly of the system[6]. A number of V-rings are 

normally used in a stacked configuration with an adaptor on both 

ends of the stack and possibly a spacer as seen in Figure 7. Adjustment

of the stack, with the spacers, is required to obtain the proper compression on the seal material.

Table 3. Relative Costs of Elastomers[5].

Elastomer Relative Cost

Styrene butadiene 1.00

Natural rubber 1.14

Butyl rubber 1.25

Ethylene propylene diene 1.00

Neoprene 1.25

Acrylonitrile butadiene 1.40

Polyacrylate 3.50

Polysulfide 2.50

Fluorocarbon 45.00

Fluorosilicone 50.00

Silicone 12.00

Polyester urethane, polyether urethane 4.00 - 10.00

Epichlorohydrin 3.00

Table 4. Relative Property Comparisons of Commonly Used Elastomers[4].

Nitrile SBR Butyl Neoprene Ethylene Fluoro- Fluoro- Poly- Poly- Silicone EpichloroPropylene carbon silicone acrylate urethane hydrin

Ozone resistance P P GE GE E E E E E E E

Weather resistance F F GE E E E E E E E E

Heat resistance G FG GE G E E E E F E FG

Chemical resistance FG FG E FG E E E P F GE G

Oil resistance E P P FG P E G E G FG E

Impermeability G F E G G G P E G P GE

Cold resistance G G G FG GE FP GE P G E GE

Tear resistance FG FG G FG GE F P FG GE P G

Abrasion resistance G G FG G GE G P G E P G

Compression set resistance GE F FG G GE G P G E P GE

Dynamic properties GE G F F GE GE P F E P G

Acid resistance F E G FG G E FG P P FG FG

Tensile strength GE GE G G GE GE F F E P G

Electrical properties F G G F G F E F FG E F

Water/steam resistance FG FG G F E FG F P P F F

Flame resistance P P P G P E FP P P F FG

E = Excellent, G = Good, F = Fair, P = Poor.

Figure 6. Example of a Static Seal (O-Ring).

O-Ring Fits into

Groove (Gland)

O-Ring

Provides 

Seal Via

Compression
16 The AMPTIAC Quarterly, Volume 8, Number 2

Material EASE

Hydraulic Seals

Selecting materials for any hydraulic seals is both critical and daunting. Seal materials must not only be able to function and endure in 

the extremes of the service environment, but must also be compatible

with the selected hydraulic fluid. The combination of chemical resistance, high and/or low temperature performance, and wear resistance

for packing seals can make the selection of seal materials for hydraulic

systems a difficult choice. In an ideal concurrent engineering setting,

all design factors – hydraulic fluid, service requirements, seal

design/geometry, and seal materials – are considered together; resulting in the synthesis of a highly robust hydraulic system. More typically

though, hydraulic systems are designed in advance, leaving it to 

the materials engineer to find a seal material which meets preset

requirements.

Ground vehicles and equipment do not generally reach the elevated temperatures of military aircraft, so that more materials are available for consideration. An extensive chemical compatibility rating of

elastomers with several hydraulic fluids is available in AMPTIAC’s State

of the Art Report (referenced on page 11).

Fuel Tank Seals

Several parameters are critical when selecting candidate elastomers for

use in fuel tank applications; the most obvious being fuel compatibility. The seal must be capable of operating in the presence of fuel for

extended periods of time without severe property degradation or complete failure. One example of fuel compatibility is shown in Table 5. It

is also important to consider whether the elastomer could contaminate

the fuel. Elastomeric seals that can function continuously under the

normal conditions experienced in fuel tank operation have great value

simply for maintenance reasons. Continuous operation with limited

maintenance is very desirable, but must be balanced against the concerns of safety, since fuel leaks can cause serious functional problems,

and are clearly dangerous.

HOW TO SELECT AN ELASTOMER

The Importance of Materials Selection

Historically, elastomeric seals are rarely given sufficient consideration

in most material selection activities or system design efforts. Seals in

general, elastomeric or otherwise, fail to garner the attention paid to

the other “marquis” subsystems. Primary structural or mission-critical

components, such as airframes, propulsion systems, drive trains,

stealth, or electronic/avionic systems seemingly tend to receive top

billing. Recent history is all-too-replete with reminders of the criticality of seal materials. Eighteen years after the Challenger disaster, most

persons old enough to remember the event, technical and layperson

Table 5. Fuel Compatibility of Elastomers for Seals and O-Rings at Low Temperatures[7].

Material Diesel Fuel JP-8 JP-5 JP-4 Gasoline Water Low-temperature bound (°C)

Nitriles ✓ ✓✓✓✓✓ –40 to –54

Fluorosilicones ✓ ✓✓✗ ✗✓ –50 to –73

Fluorocarbons ✓ ✓✓✓✓ ✗ –40 and below

✓– Compatible, ✗ – Not typically used

Figure 7. Outside Packed V-Ring Installation[6].

Spacer

V-Rings

Adaptors

answers materials engineering questions

CALL : 315-339-7090

EMAIL : amptiac_inquiries@alionscience.com

O R

VISIT : http ://amptiac.alionscience.com/Help/inquiry.html

AMPTIAC
The AMPTIAC Quarterly, Volume 8, Number 2 17

Elastomeric History: A Brief Timeline

Since the time of Columbus, the course of elastomers has been driven by geopolitics, war, and economics; with the occasional dash of chemistry and engineering sprinkled along the way.

Pre- Having learned to extract rubber from no less than eight differ1400s: ent species of latex-yielding trees, the Indian tribes of Central 

and South America employ rubber for numerous uses.

1492: Columbus “discovers” rubber and brings samples back to

Europe. The Spaniards named this substance caucho, a corruption of the Indian word for rubber, cachuchu (Inca for “weeping tree”).

1766: English scientist Joseph Priestley noticed that this substance

could be used to “rub” out, or erase the writing of pencils, thus

coined the word rubber.

1800 Industrialists in Scotland develop a solvent process to rubberize 

(ca.): textiles, producing waterproof fabrics on an industrial scale.

1803: English scientist John Gough observes that rubber warms when

stretched, contrary to the behavior of other solids.

1820: Thomas Hancock develops the process of mastication.

1826: Michael Faraday determines the hydrocarbon nature of rubber

(C10H16).

1830s- Calendaring and extrusion processes are developed, allowing 

1840s: sheets of uniform thickness and parts of uniform cross-section 

to be manufactured.

1839: Charles Goodyear discovers the process of vulcanization, which

produces stable forms of rubber. Demand rises rapidly, hailing

the start of the modern rubber industry.

1845: Scottish engineer Robert W. Thomson patents the first air-filled

rubber tire. 

1857 While synthesizing molecules of oxygenated silicon, German

Chemist Friedrich Wohler coins the term Silicone to label this

new group of compounds.

1859: James Prescott Joule, one the fathers of modern thermodynamics, revisits Gough’s earlier observations about rubber warming

when stretched. Using thermodynamic principals, he explains

the basis for this phenomenon, which is now called the GoughJoule Effect.

1876: Hevea seeds collected by British industrial concerns in the

Amazon Basin are sent back to Britain to be germinated.

Successfully germinated plants are subsequently shipped to

Ceylon (now Sri Lanka), Singapore, and Malaysia, where the

first rubber plantations are established.

1888: Scotsman John Boyd Dunlop invents the first pneumatic bicycle

tire, and with it, founds the Dunlop Tire Company, and a whole

new industry.

1890s: Rubber plantations are prospering in Southeast Asia, as a result

of the transplant of Amazon Hevea seeds. The timing was fortuitous, as blight wipes out most of the known reserves in the

Amazon during this same time period.

1892: The United States Rubber Company (now part of Continental) is

founded.

1895: The Michelin brothers begin producing pneumatic tires for early

racing cars.

1896: B.F. Goodrich Tire Company is founded.

1898: Goodyear Tire & Rubber Company is founded.

1899: Firestone Tire & Rubber Company is founded.

1899- English Chemist Frederick Kipping publishes 54 papers on the 

1937: subject of organo-silicon compounds, the precursors to modern

silicones. Purely interested in the science and chemistry of these 

compounds, Kipping fails to grasp their potential commercial 

value.

1908- Ford’s introduction of the Model T car made the automobile. 

1927: affordable to average people, spurring rapid improvements in

tire and rubber technology. By 1920, the cost of tires had come

down from $100 to $30 and service life had been extended from 

500 miles to over 12,000 miles.

1914- The first push to develop synthetic rubbers begins in Germany 

1918: (and other countries) to avert cutoff of rubber supply and to 

establish domestic sources during war.

1920s- American and British efforts to develop their own synthetics shift 

1930s: into high gear.

1929: Polysulfide rubber is invented.

1930 I.G. Farbenindustrie introduces Styrene Butadiene Rubber.

(ca.): (SBR), the world’s first mass-produced synthetic elastomer.

Marketed under the name Buna-S, it remains in production to

the present day.

1931: Polychloroprene is invented.

1936: Nitrile rubber is invented.

1938: J. Franklin Hyde (of Corning Glassworks) synthesizes ethyl

phenyl silicone, the world’s first true silicone elastomer.

1939: The term elastomer first appears in the technical literature. The

term was invented as a way to distinguish synthetic rubbers from

their natural counterparts. Its usage in this respect has diminished, but it has left a mild controversy over terminology as a

lasting legacy.

1940: Corning Glassworks sets up first ethyl phenyl silicone pilot plant,

with Dow Chemical Corporation as its major supplier.

1943: Corning and Dow both recognize tremendous commercial

potential of silicone and form Dow-Corning, a separate but

jointly-owned company.

1939: Eugene Rochow synthesizes methyl silicone for the Hotpoint

Company (a subsidiary of General Electric). GE’s management

is slow to share Rochow’s optimism about silicone’s potential.

1941: Eugene Rochow is awarded a patent for his direct synthesis

process in the manufacture of methyl silicones. This milestone

leads to the founding of GE Silicones. 

1950s: The first organic fluoroelastomers are introduced, with superior

chemical properties.

1960s: The first fluorosilicones are introduced to the market.

1986: The explosion of the Space Shuttle Challenger brings dubious

attention to o-rings and elastomers, and highlights the criticality of these under-recognized materials.

A DVANCED M A T ERIALS AND P ROCESSES T ECHNOLOGY AMPTIAC
Table 6. Seal Service Profiles for Different Applications.

Aircraft • Accrued service life of systems/components measured in flight hours.

• Highly maintenance-intensive: frequent service intervals, unscheduled repairs.

• Hydraulic seals, other critical seals replaced with similar regularity. 

Missiles • Vast majority of a missile’s life is spent in storage (up to 20 years)

• Storage followed by a single brief flight (seconds➝minutes➝hours)

• Elastomers mainly used as environmental seals (protects internal components of the missile during long-term storage).

• Seals expected to last for the duration of the missile’s service life.

Land Systems • Performance requirements vary greatly among land systems (e.g. tanks, personnel carriers, trucks, Humvees).

• Common seal applications– internal combustion engines, drive trains, hydraulics, lubrication, environmental seals, etc.

• Service intervals for these vehicles are regularly spaced (months to years).

• Most seals are replaced periodically per the vehicle’s maintenance protocol 

Sea Systems • Hull and superstructure seals must withstand long-term corrosion/degradation effects of seawater, salt fog, and biological organisms.

• Hull seals must also perform long-term while submerged.

• Seals in systems near reactors must resist low-level radiation effects.

• Seals in mechanical and power systems replaced per maintenance schedules.

Space Systems • Seals must last for the duration of the vehicle’s projected service life.

(unmanned) • Seals must be highly resistant to thermal extremes and outgassing

• Elastomers used as passive vibration dampers, reducing the vibrations caused by the propulsion system during orbital maneuvers.

• Mitigate the effects of thermal expansion mismatch between components.

Space Systems • For reusable manned space vehicles (i.e. the Space Shuttle), seals may be replaced after every mission, after several missions, 

(manned) or during major upgrades; depending on the seal’s function and criticality.

• For single-flight vehicles (i.e. Soyuz or Shenzhou), seals need last for single flight only (mostly used to maintain the integrity of the

cabin environment).

Space Systems • Launch vehicle o-ring seals and gaskets must be able to withstand and dampen the shock and vibration loads placed on 

(launch vehicles) assemblies by the rigors of transport to the launch site.

• The service life of launch vehicle seals is short, but critical. They must perform as specified for the several minutes of powered ascent,

until they are jettisoned along with their booster.

18 The AMPTIAC Quarterly, Volume 8, Number 2

Material EASE

alike, can recall that failure of an o-ring on one of the solid rocket

boosters started a chain reaction of catastrophic failures, culminating in

the loss of the orbiter and its crew.

While not all seals are used in life-critical applications, they are

nonetheless, critical to the full and nominal operation of the systems

that they serve. They are used in a whole host of different applications,

performing under a seemingly infinite number of operating and 

environmental conditions. Seals perform a function like no other component: they serve as protective barriers for critical components and 

subsystems – in essence, isolating them from surrounding hazards.

Beyond serving as effective barriers, they are also excellent shock

absorbers, acoustic barriers, vibration dampers; and are extremely capable of compensating for minor dimensional mismatches between mated

surfaces. However, not every elastomer is suitable for every application. 

As an integral part of any design activity, the material selection

process is application-driven. That is, materials most likely to meet 

specified performance requirements are employed. Understanding the

operating conditions within the seal environment, and consequently its

performance requirements, will direct the engineer’s focus as to which

material properties are the most telling about a candidate elastomer’s

probability of success.

Managing Environmental Effects

If selecting an elastomer for a seal application were strictly a matter of

mechanical performance, the evaluation and selection process would be

more straightforward. The majority of synthetic elastomers, both organic and inorganic, were each specifically developed to address the limited

thermal or chemical performance of their immediate predecessors.

Making the Right Selection

One of the greatest truisms of materials selection (for any material class

or application), is that there is rarely a single best choice. The results 

of a material downselect activity are usually much more complex, 

frequently rendering the final choice dependent on a series of trade-offs

and intangible factors. It has been said that experience is the best teacher

of all - no place is this truer than in the material selection process.

Engineers and designers naturally tend to become loyal to certain 

materials – accruing hands-on experience through successive projects,

ultimately developing a comfort level with them. This can be both a 
The AMPTIAC Quarterly, Volume 8, Number 2 19

A DVANCED M A TERIALS AND P ROCESSES T ECHNOLOGY AMPTIAC

Recent US Patents

The following is a list of recent patents issued by the United States Patent and Trademark Office in the area of materials. Interested

readers can obtain further information by accessing the Patent Office’s website: http://www.uspto.gov.

6,760,606 Auxiliary material for superconductive material

6,760,523 Tape based high fiber count cable

6,760,515 All optical display with storage and IR-quenchable

phosphors

6,760,245 Molecular wire crossbar flash memory

6,760,215 Capacitor with high voltage breakdown threshold

6,760,208 Distributive capacitor for high density applications

6,760,198 Magnetic multilayered films with reduced 

magnetostriction

6,760,194 Head gimbal assembly with piezoelectric 

microactuator

6,760,189 Soft magnetic film having high corrosion resistance,

magnetic head including the same, and method for

making the soft magnetic film

6,760,165 System and method for manufacturing an assembly

including a housing and a window member therein

6,760,092 Method for fabricating an array substrate for a liquid

crystal display with an insulating stack made from 

TFT layers between crossed conductors

6,760,021 Multi-dimensional image system for digital image 

input and output

6,759,990 Compact antenna with circular polarization

6,759,965 Light indicator

6,759,945 Variable transmittance birefringent device

6,759,935 Coil-embedded dust core production process, and 

coil-embedded dust core formed by the production

process

6,759,919 Low intermodulation film microwave termination

6,759,841 Hall-effect current detector

6,759,803 LED light source with lens and corresponding 

production method

6,759,800 Diamond supported photocathodes for electron sources

6,759,799 Oxide-coated cathode and method for making same

6,759,751 Constructions comprising solder bumps

6,759,750 Method for integrating low-K materials in 

semiconductor fabrication

6,759,748 Wiring structure of semiconductor device

benefit and a detriment to good design principles and to the end product.

What happens all too often when a material is expedited through 

the selection process, favoring familiarity and expedience over sound

material selection principles, is that some of its shortcomings and limitations are overlooked. The temptation to take such shortcuts is great –

especially when a company has used the material in question for many

years on a number of projects without incident. The risk of such neglect

is choosing a substandard material, ultimately posing a threat to the 

performance or safety of the system. A less obvious impact is the lost

opportunity from overlooking a superior material choice. On balance,

past experience is still, by far, the best source of information when 

selecting a material; but it is a part of and not a replacement for good

materials selection practices.

Service Life

The ultimate measure of a material’s effectiveness is how long it will be

able to function in its application (at the specified level of performance)

before its eventual degradation hampers overall system performance.

Service life or more specifically, service life requirements are application-dependent. These requirementsare mission-driven, specifying seal

service lives ranging from hours to years, or even for the entire life of the

vehicle or system. Service life requirements are in large part dictated by

a system’s mission or operating profile, as illustrated in Table 6.

Shelf Life

What is easy to overlook is that not all of the eventual degradation experienced by an elastomeric seal occurs during its time in service. From the

moment they are first produced, all elastomers start to degrade.

Obviously, degradation proceeds more slowly when these materials are

sitting on a shelf in a factory or depot than in service, but the fraction of

total useful service life expended during that time on the shelf is not

insignificant (and does subtract from remaining useful service life).

The length of time that an elastomeric material can be kept on the

shelf before it is unusable is known as shelf life. While elastomer service

life data are not readily available, the opposite is true for shelf life data.

Manufacturers (and others) freely publish this information.

Elastomeric seal materials are sold either as discrete parts or as bulk

materials (typically in the form of a viscous caulk or paste). The definitions of shelf life for the two are somewhat different. For discrete parts,

shelf life is the length of time before these parts are no longer acceptable

for use, and are thus discarded. The longer these parts sit in storage, the

shorter the remaining service life when installed. Shelf life for a bulk

material is defined as the maximum allowable time a material can be

stored before it must be applied or discarded. This is even more critical

for two-part sealants, which are mixed just before application and subsequently undergo a curing reaction. Expired two-part sealants will not

cure properly, thereby invalidating their use.

NOTES

† Latex is the sap drained from rubber trees, which when coagulated,

forms rubber.

REFERENCES 

[1] Industrial Engineering Chemistry, 1939, 31(3), 941

[2] Military Standardization Handbook: Rubber, MIL-HDBK-149, 1984

[3] J.L. Romeu and C.E. Grethlein, A Practical Guide to Statistical

Analysis of Materials Property Data (AMPT-14); AMPTIAC; 2000

[4] O-Ring Handbook, ORD-5700, Parker Hannifin Corporation, ORing Division, Lexington, Kentucky, 1991

[5] C.A. Harper, Handbook of Plastics, Elastomers, and Composites, 3rd

Ed., McGraw-Hill Publishing Company, 1996; DTIC Doc. AD-D450 964

[6] Navy Ships Technical Manual, Chapter 78, Volume 1, Seals, 1998

[7] Debra Diemond, Automotive Fuels at Low Temperatures, Cold

Regions Research and Engineering Laboratories; March 1991; DTIC Doc.

AD-D443 939
20 The AMPTIAC Quarterly, Volume 8, Number 2

National Thermal Protection Systems

(TPS) Workshop VII

08/31/04 - 09/02/04

Dayton, OH

Contact: Dan Cleyrat

Phone: 937.656.6482

Email: Daniel.Cleyrat@wpafb.af.mil

Web Link: www.usasymposium.com/tps/

EUROCORR 2004

09/12/04 - 09/16/04

Contact: Societe de Chimie Industrielle

28, Rue Saint-Dominique

Paris F75007 France 

Phone: 33 (0)1 53 59 02 10

Fax: 33 (0)1 45 55 40 33

Email: eurocorr2004@scifrance.org

Web Link: http://www.scifrance.org

The Fourth International Conference

on Advances in Corrosion Protection 

by Organic Coatings

09/13/04 - 09/17/04

Cambridge, England

Contact: Dr David Scantlebury; UMIST

Manchester United Kingdom

Phone: (44) 161-200 4841

Fax: (44) 161-200 4865

Email: Scantlebury@umist.ac.uk

Web Link: www2.umist.ac.uk/corrosion/CPC/

Conference/Organic%20Coatings/About_Scan

tlebury@umist.ac.uk

Advancements in Heatshield

Technology

09/14/04 - 09/17/04

Redstone Arsenal, AL

Contact: Carrie Hawes

University of Alabama in Huntsville

Huntsville, AL 35899

Phone: 256.876.2628

Email: Carrie.Hawes@rdec.redstone.army.mil

Web Link: http://smapcenter.uah.edu/AHT04

10th Intl. Symposium on Superalloys

09/19/04 - 09/23/04

Champion, PA

Contact: TMS Meeting Services

184 Thorn Hill Rd

Warrendale, PA 15086

Phone: 724.776.9000 ext 253

Fax: 724.776.3770

Email: mtgserv@tms.org

Web Link: http://doc.tms.org

MS&T ‘04 (Matls. Science & Tech. 2004)

09/26/04 - 09/30/04

New Orleans, LA

Contact: TMS Meeting Services

184 Thorn Hill Rd

Warrendale, PA 15086

Phone: 724.776.9000 ext 243

Fax: 724.776.3770

Email: mtgserv@tms.org

Web Link: cms.tms.org

SPACE 2004

09/28/04 - 09/30/04

San Diego, CA

Contact: Customer Service, AIAA

1801 Alexander Bell Dr

Reston, VA 20191

Phone: 703.264.7500

Fax: 703.264.7657

Web Link: www.aiaa.org

206th Meeting 

of The Electrochemical Society

10/03/04 - 10/08/04

Honolulu, HI

Contact: The Electrochemical Society

10 S Main St

Pennington, NJ 08534-2896 

Phone: 609.737.1902

Fax: 609.737.2743

Email: ecs@electrochem.org

Web Link: www.electrochem.org

FABTECH Int’l Forming & Fabricating -

Stamping - Tube & Pipe - Welding

10/26/04 - 10/28/04

Cleveland, OH

Contact: Society of Manufacturing Engineers

One SME Dr, PO Box 930

Dearborn, MI 48121-0930 

Phone: 800.733.3976

Fax: 313.425.3407

Web Link: www.sme.com

CANEUS 2004–Conference 

on Micro-Nano Technologies

11/05/04 - 11/05/04

Monterey, CA

Contact: Customer Service, AIAA

1801 Alexander Bell Dr

Reston, VA 20191

Phone: 703.264.7500

Fax: 703.264.7657

Web Link: www.aiaa.org

IMAPS 2004 Conference

11/14/04 - 11/18/04

Long Beach, CA

Contact: Intl. Microelectronics Pkg. Soc.

611 2nd St, NE

Washington, DC 20002

Phone: 202.548.4001

Fax: 202.548.6115

Email: imaps@imaps.org

Web Link: www.imaps.org/imaps2004

2004 Insensitive Munitions &

Energetic Materials Tech. Symposium

11/15/04 - 11/17/04

San Francisco, CA

Contact: Christina Buck, NDIA

2111 Wilson Blvd, Ste 400

Arlington, VA 22201

Phone: 703.247.2587

Fax: 703.522.1885

Email: cbuck@ndia.org

2004 AIAA Missile Sciences Conference

11/16/04 - 11/18/04

Monterey, CA

Contact: Customer Service, AIAA

1801 Alexander Bell Dr

Reston, VA 20191

Phone: 703.264.7500

Fax: 703.264.7657

Web Link: www.aiaa.org

ASIP 2004 USAF Structural 

Integrity Program

11/30/04 - 12/02/04

Memphis, TN

Contact: J. Jennewine

Universal Technology Corp.

1270 North Fairfield Rd

Dayton, OH 45432-2600 

Phone: 937.426.2808

Fax: 937.426.8755

Email: jjennewine@utcdayton.com

Web Link: http://www.asipcon.com

Aging Aircraft 2005

01/31/05 - 02/03/05

Palm Springs, CA

Contact: R. Loeslein

NAVAIR, Aging Aircraft Program

Bldg 2185, Ste 2100 C4

22347 Cedar Point Rd Unit 6

Patuxent River, MD 20670-1161

Phone: 301.342.2179

Fax: 301.342.2248

Email: loesleinGF@navair.navy.mil

Web Link: www.agingaircraft.utcdayton.com

Commercialization of Military and

Space Electronics Conference &

Exhibition

02/07/05 - 02/10/05

Los Angeles, CA

Contact: Dale Stamp, CTI, Inc.

904 Bob Wallace Ave

Huntsville, AL 35801 

Phone: 256.536.1304

Fax: 256.539.8477

Email: dstamps2173@cti-us.com

Web Link: www.cti-us.com

2005 TMS Annual Meeting &

Exhibition

02/13/05 - 02/17/05

San Francisco, CA

Contact: TMS Meeting Services

184 Thorn Hill Rd

Warrendale, PA 15086

Phone: 724.776.9000 ext 243

Fax: 724.776.3770

Email: mtgserv@tms.org

Web Link: http://doc.tms.org

Mark Your Calendar
The AMPTIAC Quarterly, Volume 8, Number 2 21

INTRODUCTION

The Air Force Research Laboratory (AFRL) has been involved

with numerous projects in nanotechnology, researching and

developing new technologies to advance the military’s aerospace capabilities. This article contains an overview of their

recent nanotechnology research intended to support aerospace

applications; it is broken up into sections covering four technology areas including fabrication methods, materials, functional devices, and modeling and simulation.

Nanostructures refer to some element of a material or 

material system that is 1 – 100 nm in size. This includes grain

size, particle diameter, fiber diameter, or layer thickness.

Nanostructured materials and devices have the ability to

enhance and/or produce novel material properties in most

areas, such as mechanical, chemical, thermal, optical, electrical,

and magnetic. Advances in nanostructure fabrication as well as

the ability to analyze such small structures are improving our

understanding of the relationship between nanostructure and

material properties. These advances will subsequently result in

better nanostructured designs with enhanced performance.

(Refer to the MaterialEASE article in the AMPTIAC Quarterly,

Vol. 6 No. 1, for a more in depth discussion of nanostructureproperty relationships, as well as nanofabrication and analysis

methods.)

FABRICATION AND MACHINING TECHNOLOGIES

The fabrication of precise stable nanostructures along with the

ability to transition such methods to marketable large-scale

processes is truly the key to success for nanotechnology. Numerous nanofabrication methods have been studied, including

powder synthesis and deposition, solution and gas phase deposition, and mechanical deformation processes. Nanomachining

techniques using an atomic force microscope (AFM) have also

been used to produce nano-sized patterns for electronic and

photonic devices.

Fabrication of Large-Scale Nanophase 

Aluminum Alloy Structures

Nanophase aluminum alloys have the ability to provide high

strength lightweight structures and components for aerospace

applications. It has been established that nanophase metals

offer increased strength and toughness over conventionally 

fabricated metals. Such aluminum structures have the potential

to replace high cost, heavier metals such as titanium. There is a

need to develop fabrication methods which can be scaled-up to

produce bulk nanophase materials.

Success has been demonstrated using both a cryomill powder

synthesis and equal channel angular extrusion (a mechanical

deformation process) to produce large scale aluminum alloys.

Benjamin D. Craig

Richard A. Lane

AMPTIAC

Rome, New York

History has witnessed innumerable advances in aeronautics and space technology since that first powered flight in December of 1903. 

A fair percentage of the major technological innovations of the twentieth century were in support of, or applicable to aerospace systems 

in some way. At the outset of this new century, several nascent technologies hold great promise to advance America’s leading edge to 

ever-higher levels. Arguably, this is nowhere more true than in the field of nanotechnology. Having evolved beyond a technical curiosity,

nanotechnology is getting a fresh look from the scientific and engineering circles of the aerospace community, as they seek ways to harness

its potential benefits for aircraft applications; as well as for launch vehicles and spacecraft.

Material Yield Strength Elongation Reduction in 

(MPa) (%) Cross-Section (%)

7075-T6 505 11 10

Nanophase Al 1st Generation 550 10 20

Nanophase Al 2nd Generation 830 5 10

Figure 1. Structure and Property Enhancement of Nanophase Al Alloys.
22 The AMPTIAC Quarterly, Volume 8, Number 2

The nanosized grain structure and subsequent increase in

mechanical properties produced in the study are shown in

Figure 1. Such bulk structures will reduce the overall weight,

and ultimately the cost of spacecraft. Nanophase aluminum

alloys are deemed applicable for several structures and components including an LH2 rocket engine fuel pump.

Polymeric Fabrication Techniques

There are two primary fabrication methodologies used to 

produce polymeric-based nanostructured systems. One is a

controlled dispersion of preformed nanoparticles, while the

second involves in-situ chemical formation of nano-sized structures. Spatial control of nanostructures during fabrication is

crucial in the development of functional

materials, such as electronic and photonic

devices. Research has

been conducted into

the fabrication of

polymeric structures,

using both an electrostatic self-assembly method, and a dielectrophoresis method.

The controlled deposition of silver into a polymeric template*

to produce conductive fibers has also been under investigation.

There is a great interest in fabricating thin film photovoltaic

devices from electroactive polymers, due in large part to its

potential to create lightweight, low cost, flexible solar cells and

photodetectors. An electrostatic self-assembly technique has

been utilized to produce such devices. In this process, layers of

oppositely charged species are sequentially deposited onto a

substrate from water-based solutions, via the electrostatic

attraction between layers. This behavior is depicted in Figure 2.

The advantage of this method is the control of film thicknesses, architecture, and composition at the nanoscale. This in turn,

affords the creation of efficient photovoltaic devices. One such

fabricated device, included an indium tin oxide (ITO) substrate, followed by an electron donating layer of polyphenylene

vinylene/sulfonated polystyrene (PPV/SPS), an electron accepting layer of polyallylamine hydrochloride/carbon (PAH/C60),

and a top electrode layer of aluminum. Figure 3 shows the 

measured current (I) of this fabricated structure as a function of

voltage potential (V).

The use of dielectrophoresis (non-uniform electric fields) is

under evaluation for the fabrication of well-defined two- and

three-dimensional structures with controlled dimensions and

compositions. This method can be readily automated to allow

manufacturing of functional devices for use in photonics, high

density data recording, and for elements to build more complex

systems. A prototype optical switch is represented in Figure 4.

Challenges anticipated in the development of this method

include the construction of electrodes required for the efficient

organization of the nanostructures, and mitigating the electrical forces developed during the organization process which

could, in fact, nullify the dielectrophoresis effect.

In-Situ Deposition of Conductive Fibers

Nanostructured conducting fibers hold the potential for

numerous applications. They are lightweight, and may be used

as signal fibers for embedded sensors, electromagnetic shielding, and smart structures. Such fibers have been fabricated by

depositing silver nanoparticles in-situ into a polymer template

structure; creating an interpenetrating silver network parallel to

the fiber axis. Spatial control is achieved through precise fiber

swelling and infiltration of the silver precursor and reduction

agents. Silver infiltrated polyphenylene-benzobisthiazole

(PBZT) fibers have been produced with conductivities exceeding 104 S/cm. The Ag/PBZT composite fiber also maintains

the high strength of the polymer. Tests have revealed approximately a 200 times increase in strength and a 50% reduction in

weight compared to the current aerospace signal wire cores (see

Figure 5).

Figure 4. Prototype Optical Switch Structure.

Figure 3. Current-Voltage Characteristics of a Solar Cell

Fabricated Using the Self-assembly Method.

Figure 5. Structure and Property Enhancement of an Ag/PBZT

Conductive Fiber.

Figure 2. Self-assembly of Polymeric

Layered Structures.

Material Modulus Strength Strain Conductivity 

(GPa) (MPa) (%) (S/cm)

PBZT fiber 95.2 900 1.98 10-12–10-14

Ag/PBZT fiber 51.8 1050 3.29 2.5x104

Ag fiber 76 55 60 6.3x105 Voltage (V)

3D Structure

Current (10-7 mA)

Aluminum

(PAH/fC60)

14

(PPV/PAA)15

ITO

-2 -1 0 1 2

6

3

0

-3

-6

-9

30 Å
The AMPTIAC Quarterly, Volume 8, Number 2 23

Fabrication of Patterned Structures via in-situ 

Deposition and Nanomachining

Methods to construct nano-sized patterns in materials include

in-situ deposition (bottom-up) and machining (top-down) 

of structures. Research has produced nanostructures using a

laser-assisted metal-organic chemical vapor deposition

(MOCVD) method and also a specialized AFM apparatus as a

lithographic tool. The AFM apparatus may be used on a number of different materials while the laser-assisted MOCVD

method is specifically used for III-V (columns of the periodic

table) compounds. The laser-assisted approach uses an ultraviolet excimer laser on a holographic optical element for 

patterning two dimensional structures deposited by MOCVD.

The next-generation, laser-assisted MOCVD is expected to

extend the technology to three dimensional patterns using a

Stranski-Krastanov† growth technique to preferentially seed

quantum dots.‡ The AFM nanomachining method has the

capability to design and fabricate three dimensional nanometer

size patterns with excellent uniformity. Figure 6 includes 

structures developed using the two techniques.

NANOMATERIALS

What distinguishes nanomaterials from conventional materials,

aside from their nanoscale structure, is that they tend to exhibit significantly better properties. This section discusses some of

the efforts that are being pursued by AFRL to develop novel

nanomaterials, optimize their properties, and harness the

advantages they offer.

Nano-Engineered Magnetic Materials

In support of the More Electric Aircraft (MEA) initiative,

AFRL has developed magnetic materials with improved properties, relative to conventional magnetic materials. The MEA

concept focuses on developing an electrical power system that

can handle primary actuation loads (e.g. flight control, landing

gear actuation, etc.) to replace the main hydraulic systems, as

well as the pneumatic, electric and mechanical power transfer

systems. This would lead to a reduction in weight, an improvement in aircraft reliability, maintainability, and supportability;

and would also reduce the amount of time required for ground

support and maintenance.

The main MEA components include aircraft integrated

power units (IPU - see Figure 7), magnetic bearings, and

internal starter/generators (IS/G), which eliminates the need

for a gearbox and reduces the A/C frontal area. These MEA

systems require magnetic materials with higher strength and

higher temperature capability. For example, the soft magnetic

Figure 6. Fabrication of Nano-Sized Patterned Elements.

Figure 7. Conceptual Design of an Integrated Power Unit (IPU).

Laser-Assisted MOCAD AFM Nanomachining

25nm Lines

Any Shape

70nm Boxes
24 The AMPTIAC Quarterly, Volume 8, Number 2

materials will be used in 450°C to 600°C environments, and

in rotors that are subjected to hoop stresses of approximately

90 ksi. To meet these requirements, nanoscale magnetic powders were produced and consolidated to create entirely new

nanocrystalline magnetic materials. (Figure 8 shows a TEM of

an iron-cobalt alloy nanopowder.) The microstructure of the

new magnetic materials was controlled by using nanoscale

powders and appropriate compaction methods to consolidate

the material. Ultimately, the mechanical and magnetic properties of the new materials were optimized for use under conditions of high temperature and stress.

Nanofilled Polymers and Composites

Unlike conventional polymer composites, which employ reinforcing materials that are typically sized no less than a micron

in any one dimension, polymer nanocomposites utilize organic

and inorganic reinforcement schemes that are sized on the

nanoscale. As a result, polymer nanocomposites display unique

properties that are fundamentally different from their conventional counterparts. A primary disadvantage of traditional

composites is that some of the favorable characteristics of the

base polymer, such as the processability and certain mechanical

properties, are sacrificed to some extent when the reinforcement scheme is applied. In the case of polymer nanocomposites, however, the base polymer retains its inherent properties to

a much greater degree, provided the distribution of the

nanoscale reinforcements is relatively uniform. Additionally,

the properties of the base polymer can be improved through

strict control of the distribution and arrangement of nanoparticles, all while maintaining the processability and low-cost

characteristics of the polymer.

AFRL has also been investigating the development, processing, and applications of polymer-layered silicate nanocomposites. These rigid, particulate-toughened matrix resins for

advanced, fiber-reinforced polymeric composites show improvements in impact resistance, coefficient of thermal expansion

(CTE) control, and suppression of microcracking, as well as

increased modulus, and ultra-low permeability. The unique

properties are especially remarkable since they have been

observed upon incremental additions of the layered silicate (1-5

vol. %) compared to their conventional counterpart which has

greater than 20 vol. % loading.[1] These nanocomposites also

exhibit great thermal stability, better ablation properties, and

improved barrier properties in gaseous environments.

AFRL is developing polymer nanocomposites with selfpassivating, self-healing, and ablative capabilities. Nanolayered

silicates form a ceramic passivation layer on the surface of 

the polymer when they are exposed to certain aggressive 

environments. These ablative nanocomposites can survive temperatures in excess of 2000°C with less than 2 vol. % nanofiller.

These materials also exhibit enhanced barrier properties and can

withstand the harsh environments of space, including atomic

oxygen, UV radiation, and electron/proton bombardment.

The nanofilled polymers and composites currently under

development are potentially suitable for a number of applications including lightweight tanks and ducting, space-durable

membranes, EMI shielding, smart fabrics, photonic crystals,

embedded antennas, multifunctional materials, and sensor 

protection.

Nanostructured Inorganic Clusters

AFRL has successfully developed a new group of polymeric

materials, as part of their effort to develop lighter weight, 

higher performance materials for space applications. This new

group of nanostructured inorganic cluster materials, called

polyhedral oligomeric silsesquioxanes (POSS), can be fabricated into hybrid organic/inorganic polymer materials. The POSS

monomers are essentially silica molecules with covalently bonded, reactive functional groups. These functional groups can be

polymerized or the monomers can be grafted on to existing

polymers. Nonreactive, organic functional groups are also 

contained on the POSS monomers to achieve solubility and

compatibility with other polymeric systems. Figure 9 shows the

chemical structure of the POSS monomer and the physical

structure of POSS containing polymers.

Up to 50 wt. % POSS can be incorporated into conventional plastics (thermoplastics and thermosets) by copolymerization

or blending without affecting the processability of the material. As a result, this can improve the thermal, physical, and

mechanical properties of most plastics. Since the size of POSS

clusters are on the nanoscale, the improvements made by incorporating them in a plastic can be achieved without negatively

affecting the desirable properties of the base polymer. Some of

the property enhancements for POSS containing polymers

include:

• Atomic oxygen & UV resistance

• Increased operating temperature

• Lower density

• Increased strength

• Increased modulus

• Reduced thermal conductivity

• Reduced flammability

The new POSS polymeric materials are suitable for use in

satellites and other space systems, since they have relatively low

densities and high moduli, and have also exhibited resistance to

space environments, such as atomic oxygen, UV radiation, etc.

The POSS polymeric materials can also be used in lubricants,

and have elevated decomposition temperatures (590°F) – much

higher than current conventional lubricants (400°F). These

novel POSS materials can also be used for numerous other

applications, such as nanostructured pulsed plasma fuel

additives, solid rocket motor ablatives, and jet canopies.

Figure 8. TEM of an FeCo Alloy Nanopowder Prepared Using a

Chemical Decomposition Process.
Highly Organized Carbon Nanotube Arrays

The carbon nanotube has become the quintessential symbol of

materials nanotechnology, primarily because of its extraordinary photogenic qualities and intriguing properties. AFRL has

actively been exploring the wide-ranging potential benefits that

carbon nanotubes have to offer, including their unique electrical, thermal, and mechanical properties. Carbon nanotubes

have been used to create novel materials with specific properties

and as reinforcements for composite materials.

POSS enabled materials can be used in conjunction with

other materials or by themselves to impart very unique properties to systems. One such unique combination is an array 

of carbon nanotubes anchored on an aluminum base, as shown

in Figure 10. The objective of this effort was to explore 

the unique physics of carbon nanotube arrays and test the

potential of the nanotube band gap for infrared detection

capability. It was determined that the optical band gap was

related to the nanotube diameter, as shown in Figure 11. This

demonstrates that carbon nanotube arrays are suitable for use

as infrared imaging detectors, since they are capable of high

resolution and are wavelength tunable. These arrays also show

potential for field emission displays since they are lightweight

and require little power. They may also find application in data

storage devices due to their high density and low power 

capability. Ultimately, the arrays may be used to form ultradense nanoelectronic networks.

Another AFRL investigation looked at metal-filled nanotubes for room temperature superconductivity. These metalfilled nanotubes take advantage of basic nanotube properties,

such as high current, low weight, and high strength, and now

have the added advantage of improved magnetic properties.

The room temperature current versus voltage characteristics of

the metal-filled nanotubes seem to mimic the behavior of low

temperature metallic superconductors. Figure 12 shows the

“staircase-like” increase in current with increasing voltage.

Although the search for a room temperature superconductor

continues, metal-filled nanotubes offer another path for further

research.

Carbon Nanotube Reinforcement

AFRL has an ongoing project to improve the structural, thermal, and electrical properties of polymer matrix composites

(PMCs) by employing carbon nanotubes as a reinforcing 

material (Figure 13). In order to realize these property improvements, there are several obstacles to overcome involving the

alignment of the nanotubes, surface modification methods,

material characterization methods, and composite fabrication

methods. Expected property enhancements include increased

strength, modulus, fracture toughness, thermal conductivity

and electrical conductivity, as well as multifunctional capability.

The potential of this technology is to enable space systems

The AMPTIAC Quarterly, Volume 8, Number 2 25

Figure 9. POSS Containing Polymers.

Figure 10. Carbon Nanotube Array on Aluminum.

Figure 11. Optical Band Gap Vs. Nanotube Diameter.

POSS - Polyoligomeric 

Silsesquioxane Monomer

Organic/Inorganic 

Polymer Coil

POSS

Monomer

1 nm

R

R

R R

R

R

R

O

O

O

O

O

O

O O

O

O

O

O

Si Si

Si Si

Si

Si

Si

Si

Polymerizable 

Organic/Inorganic 

Monomers

• Urethane

• Acrylic

• Styryl

• Norbornyl

• Siloxanes

0 2 4 6 8 10 12

100/D (Å-1)

Room Temperature

Staircase I-V

2

1.5

1

0.5

0

Eg (eV)

0 0.5 1 1.5 2 2.5 3

Voltage (V)

15

10

5

0

Current (ma)

Figure 12. Current-Voltage Characteristic of a Metal-filled Carbon

Nanotube.
26 The AMPTIAC Quarterly, Volume 8, Number 2

designs to have small and/or highly efficient thermostructural

materials. Possible applications include satellites and mirrors,

microsatellites, reinforcements for space sails, and space tethers.

Nanostructured Coatings

Nanostructured coatings are novel new materials that have

unique properties not normally available from conventional

coatings. With nanostructured coatings, for example, typically

mutually exclusive properties can be blended, such as hardness,

toughness, and low friction capability. An example of a nanostructured coating that provides unique properties is shown in

Figure 14. Solid lubricant nanoparticles and hard crystalline

nanoparticles are embedded in an amorphous metal matrix to

transform high friction, hard materials into hard and lubricious

coatings. This results in a tough, hard (wear resistant) coating

with an improved resistance to brittle failure. Another benefit

of these nanostructured coatings is that they can be developed

to maintain their properties over variable and extreme environments.

With further development, nanostructured coatings could

have a significant impact on space and satellite systems. For

example, they could easily triple the lifetime of control moment

gyros, reduce energy consumption and torque noise of mechanical components, enable high speed flywheels, and could also

tailor surface chemistry for oils/additives. For pins, latches and

gears, nanostructured coatings could prevent failure caused by

storage and launch loads, and could potentially increase the

lubricant lifetime by an order of magnitude.

Nanostructured Coatings for Improved 

Nanotribology of MEMS

MicroElectroMechanical Systems (MEMS) have shown continued success in development and application, but are not

without their own obstacles (a MEMS device is shown in

Figure 15). Friction, stiction (which is the unintentional adhesion between two surfaces), and wear, for example, have prohibited some MEMS devices from operating as intended while

limiting the performance and design of others. AFRL

researchers have been looking into nanostructured coatings for

a suitable solution to these problems. As a result, AFRL has

developed monolayered lubricants that have both bound and

mobile phases. These low friction, wear resistant nanostructured coatings are self-assembled monolayers (SAMS) capable

of self-healing due to their replenishable gas phase. MEMS

devices can now handle extreme environments, (e.g. space,

humidity, and high temperature) more easily because these

new nanostructured coatings have modified the surface forces

and chemistry to

reduce or eliminate

friction, stiction,

and wear. As an

added benefit, the

new coatings can

prevent electrical

contact degradation

in general. The

lubricant system

has been observed

to remain effective

at high temperatures, in a vacuum,

and in high humidity environments.

The surface treatments required to

apply these nanostructured coatings

is compatible with

other MEMS processing methods.

These nanostructured coatings can have a

major impact on

MEMS device development and application, because they

enable MEMS operation in space and other extreme environments and also extend the operational life of these devices.

Overall, MEMS are extremely important, as they can increase

capability of satellite and other space systems by integrating

and miniaturizing sensing and actuation systems. This results

in a reduction in weight (consequently reducing the cost) and

an improvement in the reliability of these systems.

Nanostructured Polymeric Electrolyte Membranes 

for Fuel Cells

Proton exchange membranes (PEMs) provide a transport

media for protons to migrate between the cathode and anode

Figure 13. Pictures of Nanotube Bundles and a Close-Up of

Nanotubes.

Figure 14. Example of a Nanostructured Coating.

Figure 15. MEMS Electrostatic Lateral

Output Motor.

Solid Lubricant

Particles

Amorphous Metal Matrix

Hard Crystalline

Particles

3-10 nm

1-3 nm
The AMPTIAC Quarterly, Volume 8, Number 2 27

in a fuel cell, as depicted in Figure 16. The membrane is nanostructured to provide hydrophilic regions that conduct protons,

and fluorinated hydrophobic regions to provide stability.

Nanostructured films of polyphenylene-benzobis-oxazole

(PBO) have been produced for membrane applications having

the capability to surpass currently used fluoropolymer type

membranes. The PBO membranes have been shown to have

good performance at 80°C and only 10-20% relative humidity.

Optimization of the PBO membrane and research on PBO

nanocomposite membranes are also expected to increase the

temperature range of operation, beyond the current capability

of fluoropolymer membranes.

ELECTRONIC AND PHOTONIC DEVICES

With the development of fabrication tools able to produce

structures as small as 0.1 nm, research is now ongoing to develop electronic and photonic components that are smaller, faster,

and more efficient. Studies have been underway at AFRL to produce semiconductor devices using self-organized quantum dots

and nanostructured photonic devices for optical data links, data

management, and electronic displays.

Self-Organized Quantum Dot Semiconductors

Quantum dot semiconductor devices have a strong potential

for being transitioned into numerous applications including

room temperature lasers and infrared detectors, single electron

transistors, and terabyte quantum memory storage devices.

Success has been achieved in controlling the size, composition,

and arrangement of quantum dots in

semiconductor heterostructures.

Self-organized quantum dots can 

be fabricated using the StranskiKrastanov mode whereby growth of

lattice mismatched materials occurs

by a strain-induced coherent relaxation creating dislocation-free

islands, or quantum dots, as seen in

Figure 17. By controlling the

arrangement, size, and composition

of these quantum dots, electrooptical devices with enhanced performance may be designed.

Nanolayered and Nanotemplated

Photonic Devices

Photonic devices are made from

materials in which the dielectric

constant is modulated on a length

scale comparable to the preferred

wavelength of the electromagnetic

radiation. As the size of photonic

structures approach the wavelength

of light (< 1 micron), it becomes 

difficult to confine photons in the

dielectric structure. A possible solution to this problem is to create 

periodic or quasi-periodic dielectric

structures which control the transmission, reflection, and dispersion of the photons. Two such

devices are under research, each using a different fabrication

approach to produce nanostructures that enhance the device’s

performance. One method is to deposit nanometer-thick 

layers of materials to enhance properties for optical data 

links and management applications. The device shown in

Figure 18 has produced an increase (~3.2 times) in the electrooptic coefficient over current devices.

High-speed switchable gratings have been produced by spatial

control of phase separation§ on the nanoscale. Templates are

used to fabricate phase-separated structures for developing holoFigure 16. Polymer Electrolyte Membrane Fuel Cell Structure[2].

Figure 17. Self-Organized Quantum Dots.

Nanoscale

Ionically

Conducting

Channels

Chemically, Thermally and

Mechanically Robust

PBO Membrane

10 nm

100

200

300

400 nm

100,000 nm

1) Hydrogen fuel is channeled through field

flow plates to the anode on one side of the fuel

cell, while oxygen from the air is channeled to

the cathode on the other side of the cell.

Oxygen

Flow Field

Backing

Layers

Hydrogen

Gas

Unused

Hydrogen

Gas

Water

Anode Cathode

PEM

Hydrogen

Flow Field

Air (oxygen)

2) At the anode, a platinum catalyst causes the

hydrogen to split into

positive hydrogen ions

(protons) and negatively

charges electrons.

3) The Polymer Electrolyte

Membrane(PEM) allows only

the positively charged ions to

pass through it to the cathode.

The negatively charged electrons must circuit to the cathode,

creating an electrical current.

4) At the cathode, the electrons and

positively charged hydrogen ions

combine with oxygen to form water,

which flows out of the cell.
graphic optical elements switchable by an induced electric field

(Figure 19). These devices can be used to produce optical 

displays for many applications, including cockpit avionics and

helmet-mounted displays, as shown in Figure 20.

MODELING AND SIMULATION 

OF NANOMATERIALS

Fabrication and testing of nanomaterials is not always a simple

task. In fact, testing the mechanical properties of some nanostructured materials has proven to be nearly impossible. For

example, using existing tools it is not

possible to grasp the ends of a single

nanotube to perform a tensile test.

Therefore, the modeling and simulation

of nanomaterials is extremely important

in advancing the understanding of how

these materials behave under specified

conditions. The following discusses

some of AFRL’s efforts to explore nanomaterials in the theoretical realm.

Theory of Nanocrystalline and

Multilayer Metals

A fairly well-observed anomaly that

could be considered the primary advantage of nanomaterials is the improvement in mechanical properties as the

material’s structure shifts from a

microscale size to a nanoscale size. For example, a material with

a grain size less than 100 nm shows markedly better mechanical properties compared to materials with conventional grain

sizes, which are on the microscale. Multilayered materials also

exhibit a similar quality, where the mechanical properties are

better if the layers are less than 100 nm thick, as compared to

multilayered materials with thicker layers.

AFRL has investigated this critical length scale through modeling and simulation for mechanical properties in metallic

alloys. (“Critical” denotes an unusual change in properties

based on the size scale of the material’s crystallographic structure.) Furthermore, they have developed a theoretical model

that accurately predicts the anomalous increase in strength with

decreasing thickness and strength limits in metallic multilayer

systems. AFRL has demonstrated nanostructured Cu/Nb 

multilayered materials that can be artificially grown by vapor

deposition and naturally-occurring multilayer microstructures

in lamellar TiAl (shown in Figure 21). These unique materials

show promise for advanced turbine blade shells.

Multi-Scale Simulations: Nanostructured Materials

Modeling and simulation are often used to advance the

understanding and enable better development of fabrication

techniques. AFRL has applied modeling techniques, ranging

28 The AMPTIAC Quarterly, Volume 8, Number 2

Figure 18. Nano-Layered Photonic Device.

Figure 20. Potential Applications of High-Speed Switchable

Gratings.

Figure 21. Vapor Deposited Cu/Nb Multilayer Material (Left)

and Lamellar TiAl (Right).

Figure 19. Nanophase Separated Structure for High-Speed

Switchable Gratings.

Phase Separated Liquid

Crystal and Cured Polymer

Gold Electrode

BaTiO3

AF-30/

Polycarbonate

ITO

Polarizer

Photodiode Detector

Diode Laser

(1.37 um) Lock-in Amplifier

Glass Substrate

dc Voltmeter

Signal Generator

Ω = 1kHz

150 nm V

1 μm

0.2 μm
from the molecular scale to mesoscale**,

to examine the development of nanostructured materials. This research has

provided a basis for understanding and

tailoring nanostructures to enable

advancements in fabrication, processing,

and characterization of polymeric

nanocomposites, nano-inorganic clusters, polymer dispersed liquid crystals,

and nanotribology. Among other benefits, the result of the research will lead to

improved fabrication of nanocomposites

(Figure 22) and the understanding of

nanoscale reinforcement (Figure 23).

AFRL has also been using modeling

and simulation to study the structureproperty relationship in polymerdispersed liquid crystals. The research has

focused on attempting to understand the

nanoscale structure development of polymer-dispersed liquid crystals, which are

fabricated via holography from nanoscopic liquid crystal droplets that are

aligned in polymeric resins. Specifically,

their objective is to determine the influence of the nanostructure of agile 

diffractive filters on switching voltage.

These material systems show potential for

use in applications such as display and

telecommunications technology.

Other research has focused on the 

nanotribology of self-assembled multilayers

for MEMS applications

(Figure 24). Specifically,

AFRL has looked at reducing

stiction†† by elucidating

molecular aspects, cooperative mechanisms and interfacial interactions associated

with the flow of chains in a

nanoscopic slit.

In addition to the computer modeling and simulation of materials, another

aspect of computational material science

is the design of materials. AFRL initiated

an effort to develop and apply mathematical and computational methods to

design materials at the nanoscale. The

program includes projects focused on the

integration of materials properties across

length- and time-scales for macromolecular systems, biologically inspired

materials design (biomimetics), complex

materials (e.g. liquid crystals), and

advanced scientific computing/simulation algorithms. A general success of the

program is that it has demonstrated the

design of nanomaterials for Air Force

applications with newly developed multiscale approaches, and thus has had a

wide-spread impact on the fundamental

design of nanomaterials. Specifically,

large-scale and long-time molecular

dynamics using fast multipole and multigrid methods have enabled simulations 

of liquid crystals at the nano-level.

Furthermore, an effective fragment

potential method has enabled the study

of nano-optical materials in the condensed phase. Finally, newly developed

optimization techniques have enabled

large-scale biomolecular structure determination.

Microscale analysis of a material’s

structure can provide valuable information, but analysis of a material’s structure

on the nano- or even the atomic-level

can yield extremely valuable information

about the material’s characteristics.

AFRL has attempted to extract atomiclevel structural and quantitative compositional information from high resolution transmission electron micrographs

(HRTEM) with success (Figure 25).

This has enabled the analysis of nanostructure interfaces for many different

material systems. The nano-interfaces

are characterized through the analysis of

a series of HRTEM images by a series

reconstruction method.

This capability is essential

to the development of

novel materials by nanostructural engineering,

and enables studies on the

relationship between processing, nanostructure

composition and materials

properties. Furthermore, 

it is critical to the understanding of the properties

of interfacial layers or other aperiodic

structures (irregularly occurring structures) on the nanoscale.

SUMMARY

Nanotechnology has the ability to

impact every component used in aerospace systems. The research into fabrication methods, materials, functional

devices, and modeling will lay the path

for future aerospace technologies.

Higher strength metallic and polymer

composite structures can improve flight

performance through lighter weight airThe AMPTIAC Quarterly, Volume 8, Number 2 29

Figure 22. An Example of Simulating the

Formation of Polymer-Silicate

Nanocomposites.

Figure 23. The Effects of POSS Inclusions

on the Mechanical Properties of

Polynorbornene.

Figure 25. Computer Simulations Allow

for Molecular Modeling.

Figure 24. Nanotribology of Self-Assembled Multilayers for MEMS.

SAM: –Si(CH3)2–C6H5

surface coverage: 25%

wall: silica

wall velocity: 2 m/s

wall T: 300 K
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30 The AMPTIAC Quarterly, Volume 8, Number 2

craft and spacecraft. Nanostructured coatings can provide

better protection against the harsh space environment, and

wear resistant properties for moving components. A higher

operating temperature ability of materials can push the levels

of engine performance and airspeed. Electronic and photonic materials hold the capability to improve flight controls,

communications and radar, radiation shielding, and selfdiagnostics. Nanostructured polymers also provide membranes in fuel cells for power systems. Although nanotechnology is still very much in its infancy, where the high

majority of work is in the research phase, it has the potential

to push levels of performance on all fronts, and enable 

the development of more efficient and reliable aircraft and

spacecraft.

ACKNOWLEDGMENTS

The authors would like to thank the Air Force Research

Laboratory and its scientists and engineers for contributing

much of the information and figures that were included in 

this article.

NOTES & REFERENCES

* A template is a pattern or mold for the deposition of a 

material into a precise geometrical configuration.

† Stranski-Krastanov (S-K) is one of three documented forms

of heteroepitaxial growth. In its simplest form; S-K growth is

characterized by the growth of one or more two-dimensional

layers; followed by the growth of three-dimensional islands on

top of the previous layers.

‡ Quantum dots are three-dimensional growths, or islands,

resident on the substrates of semiconducting materials. Grown

at the nanoscale, quantum dots are able to harness the quantum

effects of their constituent materials, allowing them to perform

operations in a fraction of the time of conventional electronic

components.

§ Phase separation is the process of selectively removing constituents of a material.

**While not rigidly defined, Mesoscale is generally a level of

scale that encompasses more than a few thousand atoms, but

less than billions or trillions of atoms (AMPTIAC Newsletter,

v.5, n.2).

†† Stiction is friction that inhibits the relative motion between

two components in a mechanical system.

[1] R.A. Vaia, Polymer Nanocomposites Open a New Dimension

for Plastics and Composites, AMPTIAC Quarterly, Vol. 6 No. 1,

Spring 2002

[2] www.fueleconomy.gov/ feg/fcv_PEM.shtml
The AMPTIAC Quarterly, Volume 8, Number 2 31

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Colorado, was presented the 2003 John W. Lincoln Award. It was given in recognition of his outstanding work over many years in advancing technology associated

with the concept of aircraft structural integrity. He was specifically recognized for his

outstanding work and leadership in the area of nondestructive evaluation, including

advancement of the area of quantitatively characterizing the ability of a nondestructive evaluation/inspection system to detect damage by defining the Probability of

Detection (POD) of the inspection method. The Award was presented at the 2003

USAF Aircraft Structural Integrity Program (ASIP) Conference in Savannah,

Georgia on 2 December 2003. The Award, which consists of a gold medal and a certificate of recognition, was named in honor of the late Dr. John W. (Jack) Lincoln of

the Aeronautical Systems Center, Wright-Patterson Air Force Base, Ohio. Dr.

Lincoln was a pioneer and major contributor to the development and application of

durability and damage tolerance design to insure the safety and longevity of both

military and commercial aircraft. The Award has been presented previously to Dr.

Lincoln (1996), to Mr. Charles Tiffany (1997), to Mr. Thomas Swift (1998), to

Professor Jaap Schijve (1999), to Professor Alten Grandt, Jr. (2000), to Dr. James

Newman (2001) and to Mr. Royce Forman (2002). A plaque with the names of the

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