Kutz M. Handbook of materials selection

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618 PROFESSIONAL AND TESTING ORGANIZATIONS

cational, and government institutions. NFPA conducts ﬁre safety education

programs for the general public and provides information on ﬁre protection and

prevention. Also provided by the association is the ﬁeld service by specialists

on ﬂammable liquids, electricity, gases, and marine problems.

Each year, statistics on causes and occupancies of ﬁres and deaths resulting

from ﬁre are compiled and published. NFPA sponsors seminars on the Life

Safety Codes, National Electrical Code, industrial ﬁre protection, hazardous ma-

terials, transportation emergencies, and other related topics. NFPA also conducts

research programs on delivery systems for public ﬁre protection, arson, residen-

tial ﬁre sprinkler systems, and other subjects. NFPA publications include Na-

tional Fire Codes Annual, Fire Protection Handbook, Fire Journal, and Fire

Technology.

7 NATIONAL SANITATION FOUNDATION (NSF)

The National Sanitation Foundation, more commonly known as NSF, is an in-

dependent, nonproﬁt environmental organization of scientists, engineers, tech-

nicians, educators, and analysts. NSF frequently serves as a trusted neutral

agency for government, industry, and consumers, helping them to resolve dif-

ferences and unite in achieving solutions to problems of the environment.

At NSF, a great deal of work is done on the development and implementation

of NSF standards and criteria for health-related equipment. Standard No. 1,

concerning soda fountain and luncheonette equipment, was adopted in 1952.

Since then, many new standards have been developed and successfully imple-

mented. The majority of NSF standards relate to water treatment and puriﬁcation

equipment, products for swimming pool applications, plastic pipe for potable

water as well as drain, waste, and vent (DWV) uses, plumbing components for

mobile homes and recreational vehicles, laboratory furniture, hospital cabinets,

polyethylene refuse bags and containers, aerobic waste treatment plants, and

other products related to environmental quality.

Manufacturers of equipment, materials, and products that conform to NSF

standards are included in ofﬁcial listings, and these producers are authorized to

place the NSF seal on their products. Representatives from NSF regularly visit

the plants of manufacturers to make certain that products bearing the NSF seal

do indeed fulﬁll applicable NSF standards.

8 SOCIETY OF PLASTICS ENGINEERS (SPE)

The Society of Plastics Engineers was founded in 1942 with the objective of

promoting scientiﬁc and engineering knowledge relating to plastics. SPE is a

professional society of plastics scientists, engineers, educators, students, and

others interested in the design, development, production, and utilization of plas-

tics materials, products, and equipment. SPE currently has over 37,000 members

scattered among its 91 sections. The individual sections as well as the SPE main

body arranges and conducts monthly meetings, conferences, educational semi-

nars, and plant tours throughout the year. SPE also publishes Plastics Engineer-

ing, Polymer Engineering and Science, Plastics Composites, and the Journal of

Vinyl Technology. The society presents a number of awards each year encom-

passing all levels of the organization, section, division, committee, and inter-

national. SPE divisions of interest are color and appearance, injection molding,

10 UNDERWRITERS LABORATORIES (UL) 619

extrusion, electrical and electronics, thermoforming, engineering properties and

structure, vinyl plastics, blow molding, medical plastics, plastics in building,

decorating, mold making, and mold design.

9 SOCIETY OF PLASTICS INDUSTRY (SPI)

The Society of Plastics Industry is a major society, whose membership consists

of manufacturers and processors of plastics materials and equipment. The society

has four major operating units consisting of the Eastern Section, the Midwest

Section, the New England Section, and the Western Section. SPI’s Public Affairs

Committee concentrates on coordinating and managing the response of the

plastics industry to issues such as toxicology, combustibility, solid waste, and

energy. The Plastic Pipe Institute is one of the most active divisions, promoting

the proper use of plastic pipes by establishing standards, test procedures, and

speciﬁcations. Epoxy Resin Formulators Division has published over 30 test

procedures and technical speciﬁcations. Risk management, safety standards, pro-

ductivity, and quality are a few of the major programs undertaken by the

machinery division. SPI’s other divisions include Expanded Polystyrene Divi-

sion, Fluoropolymers Division, Furniture Division, International Division, Plastic

Bottle Institute, Machinery Division, Molders Division, Mold Makers Division,

Plastic Beverage Container Division, Plastic Packaging Strategy Group, Poly-

meric Materials Producers Division, Polyurethane Division, Reinforced Plastic/

Composites Institute, Structural Foam Division, Vinyl Siding Institute, and Vinyl

Formulators Division.

The National Plastics Exposition and Conference, held every 3 years by the

Society of Plastic Industry, is one of the largest plastic shows in the world. SPI

works very closely with other organizations such as ASTM and ANSI to develop

new test methods, standards, and speciﬁcations.

10 UNDERWRITERS LABORATORIES (UL)

Underwriters Laboratories, founded in 1894, is chartered as a not-for-proﬁt or-

ganization to establish, maintain, and operate laboratories for the investigation

of materials, devices, products, equipment, constructions, methods, and systems

with respect to hazards affecting life and property.

There are ﬁve testing facilities in the United States and over 200 inspection

centers. More than 700 engineers and 500 inspectors conduct tests and follow-

up investigations to ensure that potential hazards are evaluated and proper safe-

guards provided. UL has six basic services it offers to manufacturers, inspection

authorities, or government ofﬁcials. These are product listing service, classiﬁ-

cation service, component recognition service, certiﬁcate service, inspection ser-

vice, and fact ﬁnding and research.

UL’s Engineering Services Department is in charge of evaluating individual

plastics and other products using plastics as components. Engineering Services

evaluates consumer products such as TV sets, power tools, appliances, and in-

dustrial and commercial electrical equipment and components. For a plastic ma-

terial to be recognized by UL, it must pass a variety of UL tests including the

UL 94 ﬂammability test and the UL 746 series, short- and long-term property

evaluation tests. When a plastic material is granted recognized component status,

a yellow card is issued. The card contains precise identiﬁcation of the material

620 PROFESSIONAL AND TESTING ORGANIZATIONS

Table 1 Typical Costs for Testing Services

Type of Tests

Cost per Test

Analytical: FT-IR, DSC, TGA, TMA, GPC, Additives identiﬁcation,

ﬁller content, carbon content, moisture content, chromatography,

spectrometry, NMR

$100–$500

Mechanical / Physical: Tensile, ﬂexural, compressive, shear,

puncture, tear, Poisson’s ratio, creep, impact testing, hardness,

abrasion, speciﬁc gravity, chemical compatibility, density

$100–$400

Electrical: Dielectric constant, dissipation factor, volume resistivity,

surface resistivity, dielectric strength, EMI / RFI shielding

effectiveness, arc resistance

$100–$400

Thermal / Flammability: Coefﬁcient of thermal expansion, thermal

conductivity, TMA, DSC, heat deﬂection temperature, melting

point determination, ﬂammability tests, oxygen index, TGA

$100–$500

Rheological: Capillary rheometer tests, viscosity tests, melt ﬂow

index, intrinsic viscosity, brookﬁeld viscosity, die swell

measurements

$100–$300

Optical: Colorimeter, spectrophotometer, color measurement, UV

tests, light absorption and transmission, refractive index,

yellowness index, gloss

$100–$300

Source: Plastics Technology Laboratories, Inc. Pittsﬁeld, MA; www.ptli.com.

FTIR, Fourier Transform Infrared Spectrometry

DSC, Differential Scanning Calorimetry

TGA, Thermogravimetric Analysis

TMA, Thermomechanical Analysis

GPC, Gel Permeation Chromatography

NMR, Nuclear Magnetic Resonance

including supplier, product designation, color, and its UL 94 ﬂammability clas-

siﬁcation at one or more thicknesses. Also included are many of the property

values such as relative temperature index, hot wire ignition, high-current arc

ignition, and arc resistance. These data also appear in the Plastics Recognized

Component Directory.

UL publishes the names of the companies who have demonstrated the ability

to provide a product conforming to the established requirements, upon successful

completion of the investigation and after agreement of the terms and conditions

of the listing and follow-up service. Listing signiﬁes that production samples of

the product have been found to comply with the requirements, and that the

manufacturer is authorized to use the UL Listing Mark on the listed products

that comply with the requirements.

UL’s consumer advisory council was formed to advise UL in establishing

levels of safety for consumer products, to provide UL with additional user ﬁeld

experience and failure information in the ﬁeld of product safety, and to aid in

educating the general public in the limitations and safe use of speciﬁc consumer

products.

11 TYPICAL COSTS FOR TESTING SERVICES

Due to the complexity of the tests, varying requirements and other circum-

stances, it is very difﬁcult to estimate the cost for a particular analytical test.

However, an attempt is made to give reader a general idea of the typical costs

for testing services in Table 1.

12 INDEPENDENT TESTING LABORATORIES 621

12 INDEPENDENT TESTING LABORATORIES

Atlas Weathering Services Group

17301 Okeechobee Road

Miami, Florida 33015

(800) 255-3738

Battelle Memorial Institute

505 King Avenue

Columbus, Ohio 43201

(614) 424-6533

Broutman, L.J., Associates Ltd.

3424 South State St.

Chicago, Illinois 60616

(312) 842-4100

Chemir/Polytech Laboratories, Inc.

2672 Metro Boulevard

St. Louis, Missouri 63043

(314) 291-6620

CRT Labs Inc., (Calif. Resin Testing)

2812 Walnut, Suite A

Tustin, California 92680

(800) 597-5227

Delsen Testing Laboratories, Inc.

1024 Grand Central Avenue

Glendale, California 91201

(213) 245-8517

Detroit Testing Laboratory, Inc.

7111 E. Eleven Mile Road

Warren, Michigan 48092-2709

(810) 754-9000

Dynepco Inc.

84 N. Main Street

Wharton, New Jersey 07885

(201) 361-8900

Engineered Polymers

P.O. Box 360, 42 Sears Way, West

Springﬁeld, Massachusetts 01090

(413) 787-0780

Gaynes Testing Laboratories, Ltd.

1642 W. Fulton Street

Chicago, Illinois 60612

(312) 421-5257

Ghesquire Plastic Testing, Inc.

20450 Harper Avenue

Harper Woods, Michigan 48225

(313) 885-3535

Hunter Associates Laboratory, Inc.

11491 Sunset Hills Road

Reston, Virginia 22090

(703) 471-6870

Integrated Design, Inc.

10 River Road, Suite 101

Uxbridge, Massachusetts 01569-2245

(800) 399-8457

Measurement Technology Corp.

(Measure Tech)

4396 Round Lake Road West

St. Paul, Minnesota 55112-3923

(612) 633-7651

Measurement Technology Inc.

4240 Lock Highland Parkway

Roswell, Georgia 30075

(770) 587-2222

Monarch Analytical Laboratories, Inc.

349 Tomahawk Drive

Maumee, Ohio 43537

(419) 897-9000

Plastics Technology Laboratories, Inc.

50 Pearl Street

Pittsﬁeld, Massachusetts 01201

(413) 499-0983

Polyhedron Laboratories, Inc.

10626 Kinghurst Street

Houston, Texas 77099

(713) 879-8600

622 PROFESSIONAL AND TESTING ORGANIZATIONS

Polymer Solutions Inc.

1872 Pratt Drive

Blacksburg, Virginia 24060-6363

(540) 231-3058

Q-Panel Lab Products

26200 First Street

Cleveland, Ohio 44145

(216) 835-8700

Rutherford Research Corp.

P.O. Box 249

Rutherford, New Jersey 07070

(201) 933-2091

Scientiﬁc Process and Research, Inc.

67 Veronica Avenue

Somerset, New Jersey 08873

(908) 846-3477

SGS U.S. Testing Co., Inc.

291 Fairﬁeld Avenue

Fairﬁeld, New Jersey 07004

(800) 777-8378

Skeist Inc.

375 Route 10

Whippany, New Jersey 07891

(201) 512-2020

Specialty Testing and Equipment, Inc.

42 Dutch Mill Road

Ithaca, New York 14850

(607) 257-1532

Springborn Laboratories, Inc.

10 Springborne Center

Enﬁeld, Connecticut 06082

(860) 749-8371

Underwriters Laboratories

333 Pﬁngsten Road

Northbrook, Illinois 60062

(847) 272-8800

University of Massachusetts Lowell,

Inst. Plastics Innov.

333 Aiken Street

Lowell, Massachusetts 01854-2881

(508) 934-3445

VTEC Laboratories, Inc.

212 Manida Street

Bronx, New York 10474

(718) 542-8248

X-Rite, Inc.

3100 44

Street

S.W. Grandville, Michigan 49418

(800) 545-0694

623

CHAPTER 23

CERAMICS TESTING

Shawn K. McGuire

Stanford University

Stanford, California

Michael G. Jenkins

University of Washington

Seattle, Washington

1 INTRODUCTION 623

2 MECHANICAL TESTING 624

2.1 Strength 624

2.2 Creep 628

2.3 Hardness 630

2.4 Fracture Toughness 632

2.5 High Strain Rate 633

2.6 Fatigue 634

3 THERMAL TESTING 637

3.1 Thermal Expansion 637

3.2 Thermal Conductivity 640

3.3 Heat Capacity 643

4 NONDESTRUCTIVE

EVALUATION TESTING 644

4.1 Ultrasonography 644

4.2 Radiography 646

5 ELECTRICAL TESTING 646

5.1 Electrical Resistance at Elevated

Temperatures 647

5.2 Flexural Strength of

Electronic-Grade Ceramics 647

6 SUMMARY 647

REFERENCES 648

1 INTRODUCTION

Ceramics are being used in an ever-increasing capacity in numerous industrial

and scientiﬁc applications. Advanced ceramics, in particular, have great future

possibilities for use in a wide variety of applications where their unique com-

bination of properties can achieve better results than other materials such as

metals and polymers. Advanced ceramics are typically wear and corrosion re-

sistant, lightweight, and thermodynamically stable. In addition, many advanced

ceramics have electrical properties that make them advantageous for use in elec-

tronic applications such as electronic packaging. Ceramics are ﬁnding increasing

use in such areas as biomaterials, electronics, MEMS (microelectromechanical

systems), and heat transfer applications such as gas turbines in the aerospace

industry. The market value of advanced ceramics in the United States is esti-

mated to increase to $11 billion by the year 2003 from a value of $7.5 billion

in 1998.

Similarly, the world demand for advanced ceramics has increased from

an estimated $16.7 billion in 1994 to $25.3 billion in the year 2000.

HandbookofMaterialsSelection.EditedbyMyerKutz

624 CERAMICS TESTING

With the steadily increasing use of ceramics in industry, there exists an in-

creasing demand to characterize and quantify the properties of ceramics. This

leads to higher demand for improved testing techniques to yield more exact data

used for endeavors such as design, safety analysis, quality control, and scientiﬁc

understanding. In particular, the brittle nature of ceramics makes their fracture

characteristics especially important for the engineer that needs to design ceramic

components with life-cycle and safety considerations. In addition to the predom-

inant mechanical testing being performed, there is demand for improved testing

of thermal, electrical, and environmental properties as well as others.

Of equal importance to the driving forces behind ceramic testing is the value

of the data being obtained from these tests. Do the potential beneﬁts of the data

outweigh the cost of performing the tests? What are the predictive abilities of

the quantiﬁed test results?

To aid the engineer or scientist who is starting his or her research into po-

tential ceramic test methods, this chapter gives a brief overview of the major

test methods currently being employed, relative advantages and disadvantages

to each other, and some common sources of error. In addition, a listing of stan-

dards that are both relevant and directly applicable to ceramics is given for

various testing methods. These standards can be further investigated by the

reader who wants a more in-depth look into the exact setup and requirements

of a given test. Standardization is an important process in the evolution of ce-

ramic testing to improve accuracy and precision of measured results. New stan-

dards are continuously being developed and while not all the standards listed

for each test are speciﬁcally targeted for ceramics, they still have relevance in

terms of improving the exactness of the test setup and results.

2 MECHANICAL TESTING

With the increasing role of ceramics in technology, further understanding of

mechanical properties has become increasingly more important. This has resulted

in the use and standardization of various test methods to better understand and

quantify mechanical properties. Test methods reveal such properties as strength,

fatigue, fracture resistance, creep, and slow crack growth, which contribute to

design, scientiﬁc understanding, and estimations of service life among others.

2.1 Strength

One of the most important properties for characterizing a material is strength.

Strength (yield, ultimate, etc.) is often used as a measure of success in materials

development.

The characterization of the fracture strength (approximately equal

to ultimate strength for brittle materials) distribution is needed when ceramic

design for structural applications involves failure probability as a criteria.

Var-

ious test methods are employed to determine the fracture strength of a given

ceramic material. Usually, the fracture strength is equated to the maximum stress

at the point of fracture, which requires that the stress distribution in the test

specimen be known. A common source of error in tests measuring fracture

strength is that the strength of ceramic materials is strongly inﬂuenced by the

test specimen’s size, geometry, and surface ﬁnish. The more common methods

for measuring fracture strength include uniform uniaxial stress loading, nonun-

iform uniaxial stress loading, and biaxial stress loading.

2 MECHANICAL TESTING 625

Fig. 1 Schematic of tensile, ﬂexure, and compressive setups. (From Ref. 3 by

courtesy of Marcel Dekker Inc.)

Uniform uniaxial stress load testing is performed by putting a given test

specimen into a state of tension or compression (Fig. 1). Testing in a uniform,

uniaxial stress ﬁeld controls the stress-state variable that allows determination

of the mechanical behavior at given loads. Tension and compression tests are

not as common as the nonuniform ﬂexure test because the brittle nature of many

ceramics results in the need for specialized testing equipment, extensive prepa-

ration of test specimen, and an adequately uniform stress state, which can be

difﬁcult to achieve.

Tension

The tensile test equipment consists of two main parts, the test specimen grip

holding the actual test specimen and the interface attachment that connects the

test specimen grip to the test machine. The grip should be designed to reduce

any eccentricity in order to maintain a uniaxial stress state. Ceramics, in partic-

ular, are not able to use a threaded head as an interface because of the difﬁcult

nature of machining such a brittle material. The tapered head test specimen is

also difﬁcult to machine to proper tolerances. The button head test specimen has

emerged as the most reliable interface method.

The attachment interfacing be-

tween the test specimen grip and the test machine is usually one of two designs:

ﬂexible, self-aligning and ﬁxed, alignable.

Ideally, the stress state will be characterized by the simple equation:

␴

⫽

where

␴

is the normal stress, P is the applied force, and A is the cross sectional

area. However, the actual stress state in the gauge section,

␴

, will include error

from eccentricity in the testing equipment and/or the test specimen and can be

characterized as:

␴

⫽

␴

⫹

␴

gs ab

where

PPer

axial stress,

␴

⫽ and bending stress,

␴

⫽

626 CERAMICS TESTING

with e being the eccentricity distance, r being the distance from the point in the

gauge section at which the stress is being measured to the centroid, and I being

the moment of inertia in the gauge section cross section.

Some of the tensile testing standards that apply directly to ceramics are:

Japanese Industrial Standards Committee (JISC),* ‘‘Testing Methods for Ten-

sile Strength of Monolithic Advanced Ceramics at Room and Elevated

Temperature,’’ JIS R1606-1995

American Society for Testing and Materials (ASTM),† ‘‘Standard Test

Method for Tensile Strenth of Monolithic Advanced Ceramics at Ambient

Temperatures,’’ C1273-95

ASTM, ‘‘Standard Test Method for Tensile Strength of Monolithic Advanced

Ceramics at Elevated Temperatures,’’ C1366-97

The following standards are directly applicable to metals but can have applica-

bility to ceramics:

ASTM, ‘‘Standard Test Methods for Tension Testing of Metallic Materials,’’

E8-96a

ASTM, ‘‘Standard Test Methods for Elevated Temperature Tension Testing

of Metallic Materials,’’ E21-92

ASTM,’’ Standard Practice for Veriﬁcation of Specimen Alignment under

Tensile Loading,’’ E1012-93A

Compression

The compression strength of ceramic materials is usually much greater than that

in tension. Consequently, tensile strength is usually the critical factor in terms

of design. The compression test usually consists of two load blocks exerting a

compressive force on a cylindrical test specimen. The test specimen should be

uniform to avoid buckling of individual layers aligned with the applied load.

Common sources of error are size mismatches between the load block and

specimen, surface irregularities, and eccentric loading as explained in the tensile

testing section.

The ﬁrst three errors bring about excessive stresses in the ends

of the test specimen, which can cause failures in the nongauge section of the

test specimen. Eccentricity, as in tensile testing, reduces uniformity in the gauge

section stress state.

The following standards are directly applicable to compressive testing of ce-

ramics:

JISC, ‘‘Testing Method for Compressive Strength of High Performance

Ceramics,’’ R1608-1990

ASTM, ‘‘Standard Test Method for Compressive (Crushing) Strength of Fired

Whiteware Materials,’’ C773-88

* Japan Standards Association, Tokyo, Japan.

† ASTM International, West Conshohocken, Pennsylvania, USA.

2 MECHANICAL TESTING 627

Fig. 2 Three- and four-point ﬂexure testing and resulting stress state. (From Ref. 3 by courtesy

of Marcel Dekker Inc.)

Flexure

Testing in ﬂexure typically involves a three- or four-point loading of a test

specimen as shown in Fig. 2. Compared to tension and compression tests, ﬂexure

tests are less expensive, simpler in setup, and easier to adapt to elevated tem-

perature testing.

The applied moment, M, yields the equation for uniaxial nor-

mal stress,

␴

⫽

where the moment of inertia I is (bh

)/12 (b ⫽ width and h ⫽ height) and C is

the distance from the neutral axis to the outer surface of the test specimen. Given

that the moment M

⫽ P(L

⫺ L

)/4 (L

⫽ outer span, L

⫽ inner span) and y ⫽

h/2 we can substitute into the equation to ﬁnd the fracture strength, S

, which

is the maximum tensile stress obtained at the fracture force, P

1.5P (L

⫺ L )

ƒo i

S ⫽

Various sources of internal and external errors in the testing process can affect

the measured results of ﬂexure tests. Errors classiﬁed as ‘‘internal’’ involve de-

viations from simple beam theory and involve test specimen geometry and prop-

erties.

A test specimen with an initial curvature resulting from residual stresses