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High-Performance Synthetic Fibers for Composites
HIGH-PERFORMANCE SYNTHETIC FIBERS FOR COMPOSITES
Report of the
Committee on High-Performance Synthetic Fibers for Composites
NATIONAL MATERIALS ADVISORY BOARD
Commission on Engineering and Technical Systems
National Research Council
Publication NMAB-458
National Academy Press
Washington, D.C.
1992
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High-Performance Synthetic Fibers for Composites
NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.
This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine.
The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Frank Press is president of the National Academy of Sciences.
The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsiblity for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Robert M. White is president of the National Academy of Engineering.
The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth I. Shine is president of the Institute of Medicine.
The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Frank Press and Dr. Robert M. White are chairman and vice chairman, respectively, of the National Research Council.
This study by the National Materials Advisory Board was conducted under Contracts No. MDA903-89-K-0078 and MDA 972-92-C-0028 with the U.S. Department of Defense and the National Aeronautics and Space Administration.
Library of Congress Catalog Card Number 90-62815
International Standard Book Number 0-309-04337-9
This report is available from the
National Academy Press,
2101 Constitution Avenue, NW, Washington, DC 20418. It is also available from the Defense Technical Information Center, Cameron Station, Alexandria, VA 22304-6145.
S220
Printed in the United States of America
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High-Performance Synthetic Fibers for Composites
ABSTRACT
This report describes the properties of the principal classes of high-performance synthetic fibers, as well as several current and potential methods of synthesis and processing to attain desirable properties. Various promising classes of materials and methods of fiber synthesis are suggested for further investigation.
Successful fiber reinforcement of a matrix is heavily dependent on the interface between the two components. The report emphasizes our relatively poor fundamental understanding of fiber-matrix reactions and this "interphase" region. Research directed at improving our understanding of the properties and behavior of the boundary region is identified as a prime need if advances are to be made in fiber and composite performance.
The report emphasizes the complex interdisciplinary nature of fiber science and makes strong policy recommendations for long-range continuity of fiber research and for increased support of education in fiber science.
Because of the highly international scope of the commercial fiber and composites industries and the critical importance of fibers for military and space applications, the report considers the consequences of government policy affecting these industries. Attention is called to the need for improving procedures leading to governmental decisions affecting the fiber industry.
The need for a policy to provide support for development and production of small quantities of specialty fibers for strategic military applications is also emphasized.
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High-Performance Synthetic Fibers for Composites
COMMITTEE ON HIGH-PERFORMANCE SYNTHETIC FIBERS
Chairman
RUSSELL J. DIEFENDORF,
Clemson University, Clemson, South Carolina
Members
CHARLES P. BEETZ, JR.,
Advanced Technology Materials, Inc., New Melford, Connecticut
GENE P. DAUMIT,
BASF Structural Materials, Inc., Charlotte, North Carolina
DANNY P. EDIE,
Clemson University, Clemson, South Carolina
MICHAEL JAFFE,
Hoechst Celanese Corporation, Summit, New Jersey
ARTHUR JAMES,
Lockheed Aerospace Systems Co., Burbank, California
RUEY LIN,
Howmedica, Rutherford, New Jersey
MANUEL PANAR,
E. I. duPont de Nemours & Co., Wilmington, Delaware
KARL M. PREWO,
United Technologies Research Center, East Hartford, Connecticut
THEODORE SCHOENBERG,
TEXTRON, Lowell, Massachusetts
JAMES SORENSON,
3M Company, St. Paul, Minnesota
HAROLD G. SOW-MAN,
3M Company (Retired), St. Paul, Minnesota
CARL H. ZWEBEN,
General Electric Company, Philadelphia, Pennsylvania
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High-Performance Synthetic Fibers for Composites
Liaison Representatives
BEN WILCOX,
Defense Advanced Research Projects Agency, Arlington, Virginia
WILLIAM MESSICK,
Naval Surface Warfare Center, Silver Spring, Maryland
JAMES DICARLO,
National Aeronautics and Space Administration-Lewis, Cleveland, Ohio
DANIEL R. MULVILLE,
National Aeronautics and Space Administration, Washington, D.C.
RICHARD DESPER,
Army Materials Technology Laboratory, Watertown, Massachusetts
MERRILL L. MINGES,
Wright Laboratory, Wright Patterson AFB, Ohio
JIM MANION,
Industrial Trade Administration, Department of Commerce, Washington, D.C.
NMAB Staff
JAMES H. SCHULMAN, Project Staff Officer
JANICE M. PRISCO, Administrative Assistant/Senior Project Assistant
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High-Performance Synthetic Fibers for Composites
PREFACE
High-performance synthetic fibers are key components of composite materials, a class of materials vital for U.S. military technology and for the civilian economy. The compositions of the fibers cover a wide range of chemical substances, including elementary carbon and boron, refractories such as inorganic carbides and oxides, and organic polymers. Fibrous forms of these materials are used to reinforce a similar range of matrix materials, and metals, producing composites with physical properties superior to those of unreinforced matrices. The emphasis in fiber research has been on the attainment of high-performance mechanical and thermal properties for structural applications, particularly for aerospace vehicles and aircraft.
The objective of this study is to survey major research and development opportunities for high-performance fibers needed for present and future structural composite applications and to identify steps that the federal government could take to accelerate the commercialization of this critical fiber technology in the United States. The report begins with background information on the fibers currently available for composite applications, their major uses, current and projected demands, costs, and sources of supply. New fibers and improvements in fiber properties that are needed for the various types of structural composites are discussed. The report then evaluates various approaches to fiber synthesis and processing that have the potential to either fulfill these needs or significantly reduce the cost of structural composites. The report also reviews ongoing research and development in areas that are of general importance to fiber science and technology (surface properties and treatments, fiber-matrix bonding, and fiber coatings and coating processes). Recommendations are made for future research that will be necessary to improve existing high-performance fibers and develop new ones. Included are specific steps that should be taken to ensure a domestic supply of existing and new high-performance fibers.
The report is concerned primarily with the reinforcing fibers needed in structural applications over the wide range of temperatures encompassed by organics, metals, and glass/ceramics. However, recognition is made of applications in which other useful physical properties of a fiber, such as electrical conductivity, thermal conductivity, magnetic or piezoelectric properties, allow the engineered structure to be dual or multipurpose.
Since high-performance fibers represent a new technology, in many cases only limited information exists. Thus, the length of the various sections in the report is not necessarily indicative of the importance of the topic covered.
Russel J. Diefendorf
Chairman
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High-Performance Synthetic Fibers for Composites
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High-Performance Synthetic Fibers for Composites
ACKNOWLEDGMENTS
The committee is especially grateful to the individuals who made formal presentations to the committee. At the first meeting, Joseph C. Jackson, executive director of SACMA, described SACMA's activities and offered the assistance of his organization to the committee members.
Speakers at the second meeting included William B. Hillig, General Electric Corporate Research and Development, who discussed potential composite systems and fibers; George F. Hurley, Los Alamos National Laboratory, who briefed the committee on whisker reinforcements; and Roger Bacon, AMOCO Performance Products, Inc., who talked about carbon fibers. Penny Azerdo, Pratt & Whitney Corporation, presented a paper on interactions in intermetallic systems; George Reynolds, MSNE, Inc., discussed interactions in ceramic systems; and committee member James Sorensen talked about interactions in high-temperature aircraft composites. Committee member Karl Prewo's presentation covered Japanese developments in fibers and committee member Ruey Y. Lin discussed chemical conversion of precursor fiber.
Presentations at the third meeting were made by Stanley Channon, consultant, who discussed a survey of world fiber production and technological capabilities; Joseph C. Jackson, SACMA, who described the comprehensive review his organization was preparing for a government presentation covering virtually all aspects of the fiber and composites industries; Greg Corman, General Electric (R&D), who talked about creep in single-crystal oxides; Ed Courtright, Battelle Pacific Northwest, who discussed oxygen permeability studies; Robert S. Feigelson, Stanford University, who discussed single-crystal preparation and properties, emphasizing the laser-heated pedestal growth technique; and Gary Tibbetts, General Motors Technology Center, who talked about carbon whiskers. These presentations proved to be valuable contributions to the technical contents of this report.
Special thanks also go to Donald E. Ellison, Donald E. Ellison & Associates, who supplied valuable input for the section on technology export and export control.
The chairman thanks the committee members for their dedication and for the patience shown during the numerous iterations and revisions of the report drafts. The liaison members are thanked for their active participation in committee discussions and for providing valuable support documents and data.
Finally, special thanks go to James H. Schulman, NMAB program officer, and Janice Prisco, project assistant, whose dedicated efforts made possible the production of this report.
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High-Performance Synthetic Fibers for Composites
CONTENTS
EXECUTIVE SUMMARY, Conclusions, and Recommendations
1
1
High-Performance Synthetic Fibers for Composites
9
Introduction
9
Present Materials: An Overview
11
Characteristics of Materials in Fiber Form
12
Advances in Fiber Technology
13
Types of High Performance Fibers
16
Fiber-Reinforced Composites
16
References
19
2
High-Performance Fiber Materials: Applications, Needs, and Opportunities
21
Introduction
21
High-Performance Fibers for Polymeric Matrix Composites
21
High-Performance Fibers for Metal Matrix Composites
29
High-Performance Fibers for Ceramic Matrix Composites
34
High-Performance Fibers for Carbon-Carbon Composites
41
High-Performance Fibers for Nonstructural Applications
43
References
47
3
Fiber-Forming Processes: Current and Potential Methods
49
Introduction
49
Processes to Form Polymeric Organic Fibers
51
Fiber Formation by Pyrolytic` Conversion of Precursor Fibers
54
Silicon Carbide and Silicon Nitride Fibers
65
Oxide Fibers
70
Chemical Conversion of a Precursor Fiber (CCPF)
75
Chemical Vapor Deposition
79
Technical Future
84
Alternative Processes
88
Fiber Coatings
90
Observations and Conclusions about Fiber Fabrication and Processing
98
References
98
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4
Important Issues in Fiber Science/Technology
103
Introduction: Overview of Needed Research and Development
103
Summary of Technical Issues
106
References
108
5
Important Policy Issues
109
Introduction
109
Education in Fiber Science and Technology
110
Domestic Sourcing Considerations
111
Technology Export/Export Control
113
Production of Small Quantities of Specialty Fibers
114
Foreign Competition
115
Continuity of Support
116
Glossary of Terms
119
Appendix
127
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High-Performance Synthetic Fibers for Composites
TABLES AND FIGURES
Table 1.1
High Performance Fibers
10
Table 1.2
Properties of polyamid in various forms
12
Table 2.1
Advantages of PMCs
22
Table 2.2
Advantage of PMCs
29
Table 2.3
Low-cost (aluminum-matrix) MMCs for Industrial and aerospace applications
31
Table 2.4
Some higher-cost MMC aerospace applications
31
Table 2.5
Some current high-performance-fiber reinforced MMC systems under development
33
Table 2.6
Commercially available fibers for the reinforcement of CMCs
35
Table 2.7
Manufacturing process for CMCs
38
Table 2.8
Some applications of CMCs
39
Table 2.9
Some current sources of CMCs
40
Table 2.10
Major uses of C-C composites
42
Table 3.1
Carbon fiber classification
58
Table 3.2
Oxide fibers
71
Table 3.3
Refractory fibers prepared by chemical conversion of a precursor fiber
76
Table 3.4
Comparative properties of reinforcing fibers
81
Table 3.5
Materials produced by CVD processes
94
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High-Performance Synthetic Fibers for Composites
Figure 1.1
Maximum-use temperatures of various structural materials
11
Figure 1.2
Strength of typical commercial organic fibers
14
Figure 1.3
Fiber price versus bundle size and fiber physical properties
15
Figure 1.4
Specific strength and modulus of high-performance fibers and other materials ''specific property'' means the property divided by the density
16
Figure 2.1
U.S. carbon fibers consumption by major market segment
24
Figure 2.2
U.S. carbon fiber consumption aerospace market
24
Figure 2.3
Comparison of bend tests for unreinforced cement and cement-matrix composites containing 2 percent chopped carbon fiber
36
Figure 2.4
Densities and use temperatures of potential composite matrices
37
Figure 2.5
Specific strength comparison of high-temperature metal alloys and advanced composites (two-dimentional fiber-matrix)
39
Figure 3.1
General processing steps for converting high bulk materials to fibers
50
Figure 3.2
Simplified flowsheet for precursor pyrloysis processes
55
Figure 3.3
PAN Based Process
57
Figure 3.4
Pitch based process
62
Figure 3.5
Production of Si ceramic fibers from polymetric precursors
67
Figure 3.6
Variation of tensile strength with flaw size
68
Figure 3.7
Scanning electron micrograph of fracture surface of mullite fiber
74
Figure 3.8
Transmission electron micrograph of ion milled section of mullite fiber
74
Figure 3.9
SEM of fiber FP surface
74
Figure 3.10
SEM of PRD-166 surface
74
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Figure 3.11
Boron filiment reactor
82
Figure 3.12
Photomicrographics of boron fiber
82
Figure 3.13
Histogram of boron fiber tensile strength
82
Figure 3.14
Histogram of CVD SiC fiber tensil strength
82
Figure 3.15
Schematic drawing of the µ-/cz technique
87
Figure 3.16
Description of the production of vapour-grown fibres
87
Figure 3.17
Illustration of the VLS process for SiC whisker growth
89
Figure 3.18
A schemati diagram of the pedestal growth method
89
Figure 3.19
Schematic view of a continuous fiber electroplating process
91
Figure 3.20
Schematic diagram of the CVE process
93
Figure 3.21
Schematic of a continuous CVD fiber-coating line
94
Figure 3.22
Metallorganic deposition process
95
Figure 4.1
Structure and composition of SiC fiber produced by chemical vapor deposition
107
Figure 4.2
Interphase region produced during fabrication of Nicalon fiber reinforced glass-ceramics
107
Figure 4.3
Fracture surface of boron reinforced 6061 aluminum with prenotched region also shown
107
Figure 4.4
Fracture surface of Borsic reinforced titanium with prenotched region also shown
107
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