Kutz M. Handbook of materials selection

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6 CANDIDATE MATERIALS 1249

natively, if the presence of acetic acid on a component is a problem and ethyl

alcohol may be tolerated, use of an RTV that does not exude acetic acid may

be used in the design.

Elastomers

are substances, such as natural rubber and polymers, that have ma-

terial properties that resemble rubber.

2,12

These substances have the ability to

return rapidly nearly to their original shape after sustaining substantial defor-

mation due to the application of mechanical stress and the release of that stress.

The properties of elastomers are employed as sealing gaskets and drive belts

and ﬁnd other uses that involve bending and recovery of shape.

Sometimes used for gaskets and powertrain or drive belts, elastomers are

much more vulnerable to aging and environmental degradation than other plastic

materials and must be selected with care. The designer is cautioned to consider

material properties such as compression set, creep, loss of elasticity, fatigue

failure due to repetitive load, loss of elasticity at low temperatures, strength at

elevated temperatures, tear resistance, and tensile strength that may be degraded

by exposure to ultraviolet and ionizing radiation, elevated temperatures, exposure

to some lubricants and chemicals, and continuous mechanical stress.

6.4 Ceramics and Glasses

Ceramics and glasses are used in similar ways in electronic packaging applica-

tions.

They have unique chemical, thermal, and mechanical properties. Both are

primarily used as electrical insulators; however, glasses ﬁnd a wider range of

use to include substrates, capacitor and resistor bonding components, equipment

and component enclosure seals, and similar uses.

Ceramics

Electronic ceramic materials include electrical porcelains, which have varied

properties based on the amount of aluminum oxide incorporated into the mate-

rial. Aluminum oxide is the additive of choice for ceramic materials for it im-

proves mechanical strength, greatly improves thermal conductivity, and improves

ﬂexure strength. A concern, however, is that the use of aluminum oxide sub-

stantially increases the material coefﬁcient of thermal expansion (about double

that of silicon) and elevation of the material dielectric constant. Ceramics are

often bonded to metal substrates to perform useful electronic functions.

Other oxides may be used such as beryllium (which is toxic) to achieve high

thermal conductivity, aluminum nitride (which also has a high thermal conduc-

tivity) with thermal expansion nearly that of silicon, and boron nitride (which

combines high thermal conductivity with machinability) in a softer yet durable

material.

Glass

Glass is an amorphous noncrystalline material that may be heated, even to a

liquid phase, and formed into useful shapes. Glass performs like a liquid that

has been sufﬁciently cooled to become substantially stiff and rigid. The inclu-

sions of additives can substantially alter glass melting point, thermal expansion,

1250 MATERIALS IN ELECTRONIC PACKAGING

and electrical properties. Glass may be optically clear, fused with other materials

to make resistors and capacitor elements, and is vulnerable to impact mechanical

loads and thermal shock loads that cause glass to exhibit brittle fracture.

Soda-lime glasses are used to seal hermetic packages and to form insulator

bushing for feed-through devices.

Borosilicate glasses have excellent resistance to chemicals, high electrical

resistance and low dielectric constants, and are used as binders for compounds

associated with component construction.

Lead alkali borosilicate glasses have a lower melting point and are used for

adhesive and sealing applications, including semiconductor processing.

Glass ceramics are machinable materials that may have strength twice that of

ordinary silicon dioxide glasses. They have a crystalline structure with temper-

ature stability lower than that of other glasses and may be shaped into a variety

of useful conﬁgurations.

6.5 Adhesives

Adhesives are materials that by adhesion, cohesion, or molecular bonding cling

to the surface of another material. Adhesive materials used for electronic appli-

cations are most often derived from elastomers and plastic polymers. Glasses

are used to perform adhesive functions when the properties of elastomers and

plastics have inadequate temperature range or are insufﬁciently inert to the prod-

uct environment. Lead–tin solders are used as conductive adhesives in the ap-

plication of surface-mounted parts to printed circuit boards.

Adhesives are utilized for structural bonding, to seal enclosures, to bond and

protect components from the environment, to seal mechanical joints and thus

prevent galvanic corrosion, to join parts for less cost than with mechanical

means, and to join materials where the temperatures developed by processes

such as brazing or soldering would degrade the bonded elements.

The success of an adhesive application is at least as dependent upon proper

joint design and application procedures as it is on the selection of a speciﬁc

adhesive material.

The primary requirements for achieving a successful adhesive joint include:

●

The area of the adhesive overlap must be adequate to withstand the me-

chanical loads imposed in service.

●

The mechanical loading generally should not provide peel or cleavage

stresses on the adhesive joint.

●

The adhesive must be able to wet and bond to the substrate material to

which it is applied.

●

The surfaces to be joined must be chemically clean and may require a

properly applied primer.

●

If the adhesive mixture consists of multiple components, these compo-

nents must be accurately measured and properly mixed.

●

Pressure, elevated temperatures, and positioning ﬁxtures may be needed

during cure of the adhesive.

REFERENCES 1251

Table 5 Adhesives Used in Electronic Packaging

Thermosetting Thermoplastic Elastomeric Hybrid

Cyanoacrylate Polyvinyl acetate Butyl Epoxy phenolic

Polyester Polyvinyl acetal Styrene butadiene Epoxy polysulﬁde

Epoxy Polyamide Phenolic Neoprene

Phenolic Acrylic Polysulﬁde Vinyl phenolic

Polyimide Silicone

Neoprene

●

The cure cycle may require several hours for the adhesive to gain full

strength.

●

The adhesive material must withstand processing and usage environmental

temperatures and chemicals.

There are three categories of adhesive materials:

1. Structural Adhesives intended to hold two or more parts together under

conditions where the adhesive joint is subjected to high mechanical loads

2. Holding Adhesives intended to permanently or on a temporary basis

hold lightweight items in place

3. Sealing Adhesives intended to ﬁll a space between two or more mate-

rials and provide a seal without the need to have high structural strength

There are a wide variety of materials utilized as adhesives that include at least

the adhesives identiﬁed by Table 5.

7 SUMMARY

The key to successful materials selection is the ability to identify the set of

materials most likely to offer a design solution and then to correctly select and

employ one or more materials from that set to provide the optimum result. This

involves the careful deﬁnition of the dominant technical functions that the ma-

terial must perform including compliance with an overriding set of considera-

tions. A review of the use of materials in successful design applications is also

a useful guide to materials selection. Within these constraints, the total cost of

use [basic materials cost, material preparation (machining, molding, forming,

joining, ﬁnishing, assembly, packaging, handling, protection, service limitations,

other) and customer support issues] may be determined or estimated. Each of

the remaining materials selection options may then be compared, thus leading

to identiﬁcation of the most economical and suitable choice of material for the

application.

REFERENCES

1. W. T. Shugg, Handbook of Electrical and Electronic Insulating Materials, Van Nostrand Rein-

hold, New York, 1986.

2. B. S. Matisoff, Handbook of Electronics Packaging, Van Nostrand Reinhold, New York, 1982.

3. Part 15, Federal Communications Rules and Regulations, www.fcc.gov.

1252 MATERIALS IN ELECTRONIC PACKAGING

4. M. Kutz, Mechanical Engineers Handbook, Wiley, New York, 1998.

5. D. G. Fink, Electronic Engineers’ Handbook, McGraw-Hill, New York, 1975.

6. Alloy Cross Index, Mechanical Properties Data Center, Battelle’s Columbus Laboratories, Colum-

bus, OH, 1981.

7. Metals Handbook, American Society for Metals, Metals Park, OH, 1998.

8. Stainless Steel Handbook, Allegheny Ludlum Steel Corporation, Pittsburgh, 1956.

9. Aluminum and Aluminum Alloys, American Society for Metals, Metals Park, OH.

10. www.Pb-Free.com, an interactive website dedicated to providing information regarding lead-free

soldering.

11. C. A. Harper, Handbook of Plastics and Elastomers, McGraw-Hill, New York, 81.

12. M. Morton, Rubber Technology, Van Nostrand Reinhold, New York, 1987.

1253

CHAPTER 40

ADVANCED MATERIALS IN SPORTS

EQUIPMENT

F. H. Froes

Institute for Materials and Advanced Processes (IMAP)

University of Idaho

Moscow, Idaho

1 INTRODUCTION 1253

2 CHARACTERISTICS OF

MATERIALS OF IMPORTANCE

IN SPORTS EQUIPMENT

DESIGN 1255

3 THE IMPACT OF ADVANCED

MATERIALS ON SPORTS

PERFORMANCE 1257

3.1 Running 1257

3.2 Pole Vaulting 1259

3.3 Bicycling 1260

3.4 Tennis and Squash 1263

3.5 Cricket 1264

3.6 Golf 1264

3.7 Baseball/ Softball 1266

3.8 Boats, Boards, and Wind-

Surﬁng Fins 1267

3.9 Javelin 1269

3.10 Skiing and Boards 1270

3.11 Hockey Equipment 1270

4 ETHICAL CONSIDERATIONS 1270

5 CONCLUDING REMARKS 1272

REFERENCES 1273

1 INTRODUCTION

Advanced materials can signiﬁcantly enhance sports performance and dramati-

cally tilt the playing ﬁeld. This paper discusses the use of advanced materials

in sports and suggests that there are ethical questions surrounding their use.

Advanced materials with mechanical and physical behavior characteristics

well in excess of those exhibited by conventional high-volume materials such

as steels and aluminum alloys have contributed signiﬁcantly to the increased

performance of transportation systems in aerospace, automobiles, and rolling

stock (trains). The important characteristics include strength, ductility, stiffness

(modulus), temperature capability, forgiveness (a collective term including frac-

ture toughness, fatigue crack growth rate, etc.), and low density. For many high-

performance applications high cost can be accepted, although the level of

acceptance depends upon the industry in question (Fig. 1).

In this chapter the role of advanced materials in a number of sporting events

will be addressed. At the highest professional level sports are a highly compet-

itive occupation with millions of dollars depending upon fractions of a second

or tenths of an inch. Even the dedicated amateur is willing to invest a great deal

of money to improve performance, even though this may occur as infrequently

HandbookofMaterialsSelection.EditedbyMyerKutz

1254 ADVANCED MATERIALS IN SPORTS EQUIPMENT

• Construction

• Automotive

• Commercial Aerospace

• Military Aerospace

• Biomedical

Emphasis on cost

Emphasis on performance

Fig. 1 Impact of cost in various industries.

Fig. 2 Graph showing how industries in advanced materials lead to

enhanced performance, and a $17-billion sporting equipment market in the

United States in 1997 says the buying public agrees.

as once a month. Thus, just as in the industries mentioned earlier, if advanced

materials lead to enhanced performance, their use can be justiﬁed; and a $17

billion sporting equipment market in the United States in 1997 says the buying

public agrees (Fig. 2). The characteristics of advanced materials that lend them-

selves to this enhanced sporting behavior parallel those listed for other industries

above.

Just as in the transportation industry the materials of choice for sports have

shown a major evolution over the last 100 years. From naturally occurring ma-

terials such as wood, twine, gut, and rubber we have progressed to high-

2 CHARACTERISTICS OF MATERIALS OF IMPORTANCE 1255

technology metals, polymers, ceramics, and synthetic hybrid materials, including

composites and cellular concepts.

In this chapter consideration is ﬁrst given to a broad discussion of the me-

chanical properties of materials that are signiﬁcant in sporting equipment. Then

there is a more detailed examination of how advanced materials have impacted

various speciﬁc sports. Here an attempt has been made to deﬁne how measurable

(absolute) records have been inﬂuenced by these advanced materials. I have

attempted to subtract the portion of these improvements that are a result of

improvements in the capability of the human body, whether this be a conse-

quence of enhanced body function derived from superior training, diet, or will

power. Advanced materials have led to substantial improvement in some sports,

much less in others. In addition, advanced materials have not only led to im-

provements in performance for the paraplegic athlete, but in some cases partic-

ipation would not have been even possible without them. Finally, there is a

discussion of the ethics of the use of advanced materials in the sporting arena.

The term technological momentum

—once technological choices are made

(or ‘‘allowed’’) and implemented, reversing the decision becomes difﬁcult—

exists for sporting equipment. This is particularly the case when athletes and

manufacturers have a great deal invested in the new technology. Once a sports

organization makes a technological choice, it is often a permanent decision.

2 CHARACTERISTICS OF MATERIALS OF IMPORTANCE IN SPORTS

EQUIPMENT DESIGN

The optimum design of sports equipment requires the application of a number

of disciplines not only for the enhanced performance already mentioned but also

to make the equipment as ‘‘user friendly’’ as possible from the standpoint of the

avoidance of injuries.

Clearly sports equipment design encompasses materials

science, mechanical engineering, and physics; however, it also necessitates a

knowledge of anatomy, physiology, and biomechanics. Biomechanics can be

simply deﬁned as the science of how the body reacts to internal and external

forces.

It is thus an attempt to apply the basic laws of physics and mechanics

to the joints, ligaments, and tissues of the body as they are subjected to loading

(Fig. 3).

In designing sports equipment, various characteristics of materials must be

considered

4,5

●

Strength

●

Density

●

Ductility

●

Fatigue resistance

●

Toughness

●

Modulus (damping)

●

Cost

To meet the requirements of sports equipment, the materials of choice often

consist of a mixture of material types, metals, ceramics, polymers, and composite

concepts. They are fabricated into the desired equipment making use of creative

1256 ADVANCED MATERIALS IN SPORTS EQUIPMENT

Fig. 3 Biomechanics of sports addresses the analysis of forces and stresses

which act on the body in various sports. (From Ref. 2.)

Table 1 Typical Mechanical Properties of Material Classes

Materials Classes

Young’s Modulus

E (MPa) ⫻ 10

Density

␳

(mg m

⫺3

) E /

␳

⫻ 10

Metals 40–210 2–8 24–30

Glass 73

⬃2.5 ⬃30

Ceramics 400–700

⬃3.5 100–230

Fibers (B,C)

⬃400 ⬃2.4 ⬃170

Carbon ﬁber composite 200 2.0 100

Wood 14 0.5 28

design concepts with due attention being given to biomechanical requirements.

By comparing speciﬁc properties (i.e., taking the difference in density of com-

peting materials into account), the attributes of different materials can be better

evaluated (Table 1). If we want a material that features the highest possible

stiffness for the least possible weight, we would select the materials with the

3 THE IMPACT OF ADVANCED MATERIALS ON SPORTS PERFORMANCE 1257

Fig. 4 Parts of a running shoe. (From Ref. 2.)

highest speciﬁc stiffness. Cellular concepts win out compared to monolithic ma-

terials in this regard because the density of cellular materials are less than those

of solid articles. In the actual design of complex sports equipment, a speciﬁc

design criterion needs to be deﬁned to allow the optimum materials selection to

be made.

3 THE IMPACT OF ADVANCED MATERIALS ON SPORTS

PERFORMANCE

To illustrate how advanced materials have impacted sports performance a num-

ber of sporting events will be considered in which a contribution to the improved

performance can be attributed to the materials used to construct equipment.

Wherever possible, measurable quantities (distance, time) of improvements in

performance will be given.

3.1 Running

Shoes have provided substantial improvements in the running events. The human

feet are very complex biomechanical structures that are highly prone to stress

and injury.

Thus, a running shoe needs to be complex and consists of a variety

of different materials (Fig. 4),

which are selected according to their resilience,

strength, elasticity (stretchability), compression, durability, and wear resistance.

About 80% of runners hit the ground on the center heel, roll onto the midfoot,

and ﬁnally push off with the ball of the foot.

The midsole is key in providing

cushioning during impact with the ground. Usually, it is made from a plastic

foam that in some concepts includes ‘‘air pockets’’ (Air Max) ﬁlled with pres-

surized gas. However, these cushioning effects break down with use (even after

only 100 km of running) with reduced cushioning efﬁciency. For the future,

better cushioning systems are likely with increased tailoring to the individual (if

you can afford it).

1258 ADVANCED MATERIALS IN SPORTS EQUIPMENT

0.5

1.5

2.5

3.5

1880 1900 1920 1940 1960 1980 2000 2020

Years

Marathon Record Time (hrs)

Fig. 5 Improvement in Olympic records for the men’s marathon in the past 100 years.

9.5

10.0

10.5

11.0

11.5

12.0

12.5

Winning time in 100m sprint (s)

1896

1900

1904

1908

1912

1916

1920

1924

1928

1932

1936

1940

1944

1948

1952

1956

1960

1964

1968

1972

1976

1980

1984

1988

1992

1996

Fig. 6 Winning times for the 100-m sprint at the Olympic Games since 1896.

This author contends that the improvements summarized above have been

much more in the comfort/avoidance of injury arena than in absolute perform-

ance enhancement. In 1896 in the ﬁrst modern-day Olympics when Spiridon

Loues won the marathon (which was actually somewhat shorter in distance than

it is today), for all of Greece to celebrate with him, he barely broke 3 h (Fig.

5). Almost 100 years later the Olympic marathon record is a little over 2 h,

about a 30% improvement. The majority of this improvement can be attributed

to an improvement in human performance. The same can be said for the 100-

m event (Fig. 6).

If we turn our attention to the paralympics, a totally different situation exists.

There were no Olympic Games in 1896 for those requiring prosthetic limbs.

The paraplegic could hardly move, never mind compete in athletic competition.

But by 1992 the paraplegic could not only compete, but he could also outperform

the majority of us who have use of all our limbs.

Paraplegic Joe Gaetani broke world records in both the 100-m and 200-m

sprint events in Barcelona (Table 2). He made use of the amazing Springlite II