Table Of ContentFractography in Failure Analysis
of Polymers
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Fractography in Failure Analysis
of Polymers
Michael D. Hayes
Engineering Systems Inc. (ESI), Atlanta,GA, USA
Dale B. Edwards
Engineering Systems Inc. (ESI), Aurora, IL, USA
Anand R. Shah
Engineering Systems Inc. (ESI), Aurora, IL, USA
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Foreword
This book is a welcome and needed addition to the technical litera-
ture. It has the advantage of being coauthored as opposed to being a
collection of symposium papers or an edited volume. This provides a
book which can be better used as an educational tool. The years of
experience of the authors in the field of failure analysis of polymers
lends credibility to their approach for understanding and investigating
the failure of polymer products. This book not only provides chapters
dealing with fundamentals of failure analysis and characterization meth-
ods, but also includes a significant number of case studies based on the
personal experiences of the authors. The case studies cover a very wide
range of polymers, product types, and failure modes and greatly add to
the value of the book.
I began studying polymer fracture, fracture toughness, and fracture
surfaces as part of my doctoral thesis at MIT from 1961 to 1963. At
that time, I could find only one other scientist characterizing fracture
toughness of polymers and, fortunately, I had the opportunity to meet
with him during my own research. In 1961, studying fracture surfaces
was done with optical microscopes, and images were typically recorded
on Polaroid film. Scanning electron microscopes were still a few years
away, and once they became available, great advances were made in
characterizing microscopic details of polymer fracture surfaces.
L. J. Broutman & Associates, which I founded in 1982, became the
leading consulting company in North America conducting failure analy-
ses on polymer and polymer composite products. Clients included
municipalities, private corporations, government agencies, and law
firms. For a major failure analysis involving systemic failures, we
would use chemists, mechanical engineers, materials scientists, and
microscopy experts working together to understand and alleviate the
problem. Dale Edwards and Andy Shah were key staff members and
had the opportunity to work on some of the most major polymer prod-
uct failures in North America in the 1980s and 1990s. Consulting on
failures in products ranging from silicone breast implants to large diam-
eter reinforced plastic irrigation piping was common.
All three authors in their current employment continue to do failure
analyses on a variety of polymeric products. It should be clear that this
xi
xii FOREWORD
book is based on years of experience determining causes of failure and
is an authoritative source of information for students, engineers, and
scientists interested in learning the methodologies required for effective
failure analysis.
Larry Broutman
Preface
The book, “Fractography in Failure Analysis of Polymers, is the cul-
mination of many years of practical experience in studying the behavior
of polymer materials and the performance of plastic products in service.
The professional careers of all three authors have involved examining,
testing, and evaluating plastic products and materials to determine the
root cause of product failure on a routine basis.
The subject of product failure is a sensitive and often a controversial
issue. A general response to a product failure is to initiate an investiga-
tion to determine how and why the product failed. However, the results
of these investigations are generally not publicized, because, by doing
so, someone or some entity must take accountability for the cause of
the product failure. The authors have observed that, because of the lack
of literature detailing product failures, errors in the decision making
processes in product design, material selection, and material processing
often do not get corrected, and the same mistakes are repeated. As a
result, the feedback loop between failure analysis and failure prevention
is often missing.
Only a few books are available as a reference to the current genera-
tion of engineers to help in understanding how and why plastic products
fail. The literature is particularly sparse when it comes to details con-
cerning the use of fractography in plastic product failures. Typically,
the subject of fractography in books is explored in the context of
describing the fracture surface of samples tested under laboratory condi-
tions. Many textbooks discuss the fracture process of polymers by eval-
uating the fracture surface features of samples that were failed in a
controlled manner in which the temperature, strain rate, or chemical
exposure was varied. Although it is useful to study the fracture charac-
teristics of laboratory-tested specimens, the translation of this knowl-
edge to an understanding of the fracture process in a plastic part with a
complex geometry, loading, and environmental exposure history
requires substantial experience. Moreover, most books discuss fracto-
graphy of polymers by showing fracture surface features at relatively
high magnifications that were obtained using a scanning electron micro-
scope (SEM). What is not discussed in these books is the amount of
information that can be obtained by visual observation and optical
microscopy with only 10x to 50x magnification.
xiii
xiv PREFACE
This book is intended to give the reader information on how to uti-
lize fractography effectively in the course of a root cause failure analy-
sis of a plastic product. In Chapter 6, numerous plastic product failure
case studies are provided as examples to illustrate the use of fractogra-
phy and other aspects of failure analysis. Our aim in providing this
information is to provide real-world examples of these tools in action
for the benefit of engineers and material scientists but also to assist
manufacturers in preventing future plastic product failures.
Acknowledgments
The concept for this book developed from material originally
included in the Fracture and Failure Analysis Seminar series presented
by L. J. Broutman & Associates (LJBA) in cooperation with the Society
of Plastics Engineers (SPE). In particular, the authors were inspired by
conversations with and the writings and teachings of Dr. Lawrence
J. Broutman, Dr. Paul K. So, Dr. Eric Baer, Dr. Anne Hiltner, and
Dr. Lee Nylander. This book would not have been possible without the
knowledge gained from years of working with these individuals.
It has been a privilege for the authors to work at various companies
that have provided failure analysis services. This work has allowed the
three of us to gain widespread experience in conducting fractographic
examinations of plastic failures and to conduct in-depth failure analyses
on a wide variety of materials and applications. This work has continued
at our current employer, Engineering Systems Inc. (ESI). The authors
would like to acknowledge our colleaguesat ESI for their support of this
project. In particular we would like to thank Dr. Donald Duvall, Ronald
Parrington, Will Pinkston, and Dr. Pierce Umberger, who reviewed por-
tions of the manuscript and provided valuable feedback. Many others
helped with laboratory work, information gathering, and preparation of
figures and photographs, all of which were important additions to the
book: Dr. Michael Hanks, Jeff McDougall, Dustin Turnquist, Dr. Garth
Freeman,StanSangdahl,ScottKarlins,andLissaMaratea.
We would also like to thank our families for their support, as this
book would not have been possible without it.
Michael D. Hayes
Dale B. Edwards
Anand R. Shah
December, 2014
xv
1 Introduction
1.1 Motivations
It should come as no surprise to an individual interested in reading
Fractography in Failure Analysis of Polymers that plastic products do
occasionally fail. This possibility exists partly because of the sizeable
number of factors that influence product performance, including mate-
rial formulation, processing, design, and implementation. Small changes
in these variables can have a dramatic effect on the performance of the
product. Although plastics, when used properly, are not any more prone
to failure than other materials, the number of failures has undoubtedly
increased over the last few decades as the volume of plastic production
has increased by 300% in the United States alone (as measured by US
dollars) [1,2]. Today, plastics are one of the most utilized materials
in the world, and their use in demanding engineering applications
continues to increase. Thus, the increase in failures can be attributed
not only to an increase in sheer volume of plastic parts in service
but also to their use in new innovative applications, which push the
boundaries of design, material performance, and processing.
When a plastic product does fail, it may lead to property damage,
environmental damage, personal injury, or death. Failures can also be
damaging to the manufacturer, impacting its brand credibility, financial
strength, and ability to function without a loss in employee productivity.
A high profile or catastrophic product failure can also be a distraction to
the company, requiring a shift of resources from research and develop-
ment and manufacturing to warranty claim work, failure analysis,
customer relations, and possibly even litigation. In addition, a proper fix
must be developed and deployed to eliminate the failures. Hopefully,
one positive outcome will be an increase in the collective awareness of
the potential causes of failure and an improvement in quality control
processes,sothatsimilarfailurescanbeavoidedinthefuture.
The determination of how and why a plastic part fails is important for
all parties involved in bringing the product to market—not just the manu-
facturer. This includes raw material suppliers, compounders, designers,
and distributors. It has been reported that in the United States alone,
approximately 900,000 individuals are directly employed in the plastic
FractographyinFailureAnalysisofPolymers.
DOI:http://dx.doi.org/10.1016/B978-0-323-24272-1.00001-5
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