Preface
Downloaded by NEW YORK UNIV on April 17, 2015 | http://pubs.acs.org Publication Date: May 1, 1990 | doi: 10.1021/bk-1990-0424.pr001
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SIGNIFICANT DICHOTOMY EXISTS in the damping field: There are those scientists concerned primarily with viscoelastic relationships and material properties that surround the glass transition; then there are the acoustical engineers who design better damped structures in a very practical world. This dichotomy has led to a situation in which polymer scientists are surprisingly unfamiliar with the physical mechanisms by which material properties affect damping efficiency in engineering structures, and in which engineers do not fully use the ability of polymer science to control features of glass transition, loss and storage modulus.
The symposium on which this book is based was held for the specific purpose of bringing these two specialties together. Each group has aggressively presented background material it felt the other was lacking, and each presented its views on what is needed to produce more effective damping materials and structures in the future. We invite you to read this book, whatever your technical background, and to consider it a first step toward the integration of this interdisciplinary field. To this end, the book contains many introductory tutorials and review chapters grouped within several sections, each section addressing (sometimes only broadly) a given topic. We caution those already involved with polymers or damping that reading only those sections of interest to your specialty reinforces the dichotomy this book is attempting to remedy. We encourage you to read the book as a whole, with particular emphasis on those subjects outside your specialty. We want to thank the many people and organizations who made possible both the symposium and the book. The ACS Division of Polymeric Materials: Science and Engineering provided significant financial support for several overseas speakers and contributed to the cost of organizing the symposium. Lehigh University's Office of Research provided Sperling with a special grant to defer publication costs. We wish to thank all the contributors for their time and effort;
ix In Sound and Vibration Damping with Polymers; Corsaro, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.
special thanks go to Bruce Hartmann for his technical assistance and to Virginia Newhard, secretary to Lehigh University's Polymer Laboratory, for her support in computer work and organizational activities. ROBERT D . CORSARO
Naval Research Laboratory Washington,DC20375-5000 L. H. SPERLING
Downloaded by NEW YORK UNIV on April 17, 2015 | http://pubs.acs.org Publication Date: May 1, 1990 | doi: 10.1021/bk-1990-0424.pr001
Lehigh University Bethlehem,PA18015 January 24, 1990
In Sound and Vibration Damping with Polymers; Corsaro, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.
Downloaded by NEW YORK UNIV on April 17, 2015 | http://pubs.acs.org Publication Date: May 1, 1990 | doi: 10.1021/bk-1990-0424.pr001
Introduction
Damping for suppression of sound and vibration has become dramatically topical, and justifiably so. There are an increasing number of high-payoff applications, both military and civilian. The trend is toward energy conservation and the attendant lighter weight and higher speeds. It follows that acoustic and vibratory disturbances are greater and structural response is both potentially larger and less desirable. The population has been conditioned to expect quiet. We don't want to hear aircraft taking off. We don't want to hear the dishwasher. We don't want to hear road noise from the car. Damping technology has quieted all of these and more. Successful damping applications require high levels of expertise. First, the basic problem must be investigated (i.e., the disturbance, the response, and the problem mode mechanics must be understood). The operational conditions, especially operating and survival temperatures, are extremely important. With the problem mode and operational temperature known, accurate and efficient design methods may be used to develop possible solutions. Damping polymers must be selected both for function at the operating temperature range and for adequate environmental resistance and stability. Experimental and verification testing are essential to establishing design practicality. Fabrication processes must be technically satisfactory and economical. Damping performance is related to structure and molecular weights of moieties; optimized polymeric compositions may be specified for specific applications. Techniques for reducing sound include scattering by inhomogeneities, mode conversion at boundaries, redirection, and intrinsic absorption. The temperature of peak damping depends on chemical composition variables: backbone flexibility, steric effects, polarity, plasticizers, crystallinity, pendant groups, and cross-link density. Inclusions and voids have a significant effect on reflection, absorption, and velocity of sound; theories may predict effects of microscopic or macroscopic inhomogeneity. Mode conversion scattering can be very effective. Further work is needed not only in the dynamic mechanical properties of polymers and reduced sensitivity to temperature, but also in properties such as toxicity,flammability,outgassing, resistance to heat, moisture, hydraulic fluid, air, atomic oxygen, and radiation. The development of successful applications depends on continued advancement of scientific understanding of basic principles. Clearly, greater understanding of this subject area will point the way to materials and design concepts that underlie a wide range of damping applications. The chapters in this volume contribute significantly. Dr. Lynn Rogers Flight Dynamics Laboratory Wright-Patterson Air Force Base, Ohio 45433 November 1989
1 In Sound and Vibration Damping with Polymers; Corsaro, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.
