High-Performance Structural Fibers for Advanced Polymer Matrix Composites
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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 study was supported by Contract No. MDA972-01-D-001 between the National Academy of Sciences and the Department of Defense. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the organizations or agencies that provided support for the project.
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COMMITTEE ON HIGH-PERFORMANCE STRUCTURAL FIBERS FOR ADVANCED POLYMER MATRIX COMPOSITES
JOHN W. GILLESPIE, JR.,
University of Delaware,
JON B. DeVAULT,
DeVault & Associates, Pinehurst, North Carolina
DAN D. EDIE,
Clemson University, Clemson, South Carolina
E.I. du Pont de Nemours and Company, Richmond, Virginia
THOMAS J. HAULIK,
Cytec Carbon Fibers, Alpharetta, Georgia
JOHN L. KARDOS,
Washington University, St. Louis, Missouri
LINDA S. SCHADLER,
Rensselaer Polytechnic Institute, Troy, New York
ARUL MOZHI, Study Director
LAURA TOTH, Senior Project Assistant
NATIONAL MATERIALS ADVISORY BOARD
KATHARINE G. FRASE,
IBM, Hopewell Junction, Kentucky,
Ford Motor Company, Dearborn, Michigan
Oak Ridge National Laboratory, Oak Ridge, Tennessee
CHERYL R. BLANCHARD,
Zimmer, Inc., Warsaw, Indiana
BARBARA D. BOYAN,
Georgia Institute of Technology, Atlanta
L. CATHERINE BRINSON,
Northwestern University, Evanston, Illinois
The Boeing Company, St. Louis
University of California, Berkeley
HAMISH L. FRASER,
Ohio State University, Columbus
JOHN J. GASSNER,
U.S. Army Natick Soldier Center, Natick, Massachusetts
SOSSINA M. HAILE,
California Institute of Technology, Pasadena, California
THOMAS S. HARTWICK, Consultant,
ARTHUR H. HEUER,
Case Western Reserve University, Cleveland, Ohio
Sandia National Laboratories, Albuquerque, New Mexico
ANDREW T. HUNT,
nGimat Company, Atlanta, Georgia
FRANK E. KARASZ,
University of Massachusetts, Amherst
CONILEE G. KIRKPATRICK,
HRL Laboratories, Malibu, California
Los Alamos National Laboratory, New Mexico
HENRY J. RACK,
Clemson University, Clemson, South Carolina
Rensselaer Polytechnic Institute, Troy, New York
LYLE H. SCHWARTZ, Consultant,
Chevy Chase, Maryland
JAMES C. SEFERIS,
University of Washington, Seattle
SHARON L. SMITH,
Lockheed Martin Corporation, Bethesda, Maryland
Materials Modification, Inc., Fairfax, Virginia
GARY FISCHMAN, Director
A high-performance polymer matrix composite (PMC) consists of a thermoset or thermoplastic resin matrix reinforced by fibers that are much stronger and stiffer than the matrix.1 Structural fibers that may be used as the reinforcement phase include carbon, aramid, glass, and many others. PMCs are attractive because they are lighter, stronger, and stiffer than conventional materials, with the additional advantage that their properties and form can be tailored to meet the needs of a specific application. Depending on the characteristics of the resin matrix and fiber reinforcements, PMCs may also be tailored to exhibit such properties as high thermal or electrical conductivity, stealth characteristics, and sensor capabilities.
High-performance PMCs were initially developed in the 1960s and 1970s for use in military applications such as aerospace and missile systems. The results may be seen today in systems fielded by each of the military services. For example, the U.S. Navy’s F/A-18 E/F consists of 19 percent carbon-epoxy composites by weight, and the forthcoming Joint Strike Fighter could be between 25 and 30 percent composite by weight. The Army has used composites extensively in munitions, ground vehicles, and soldier protection systems. The Army’s M829A2 antitank weapon employs a composite sabot that accounts for 385,000 pounds of composite per year, making it the largest single user of carbon-epoxy in the Department of Defense (DoD).2
As the prices of high-performance fibers declined in the 1980s due to process improvements, composites began to find applications in commercial aircraft, in industrial applications such as pressure vessels, and in sports and leisure equipment. Today, these commercial markets have expanded to such an extent that DoD accounts for less than 10 percent of the domestic market and less than 5 percent of the world market.3 The relative decline in percentage of the DoD demand for composites compared with commercial market demand has important implications for future DoD access to affordable fibers having properties to meet its specifications.
Composites are expected to play an even greater role in military systems of the future. The Army’s Objective Force, part of DoD’s Future Combat System, exemplifies an ongoing transformation to an entirely new future combat system incorporating advanced materials and design concepts for munitions, armament, and hull structures that will be light enough to be deployed rapidly on C-130 aircraft.4 Ground vehicles will be needed in the 10- to 20-ton range with superior mobility, transportability, survivability, and lethality for a variety of missions. In the Army, a 100-fold increase in composites usage is projected to
satisfy weight and performance requirements.5 Although a 100-fold increase in the Army's currently small usage may not revolutionize the industry, even more extensive use is expected in Navy and Air Force systems. For example, the deckhouse structure for the Navy's new DD(X)6 is constructed of a carbon-fiber-reinforced vinyl ester with a balsa core. The total weight for one ship deckhouse is 500 tons of structure. The Navy currently plans on producing one to two per year with the composite deckhouse for a total of 20 to 32 ships.7
As future military systems rely more heavily on composite materials in their transformation to become lighter, faster, and more lethal, the military will continue to require access to reliable sources of affordable, high-performance fibers and, where possible, will seek to take greater advantage of commercial off-the-shelf materials and manufacturing processes. Although specialty fibers are available that appear to meet DoD’s current performance requirements, fiber costs over the next 10 years for defense applications could be significantly reduced if DoD accepts commercially available fibers. If strict specification and qualification requirements can be reduced or modified, commercially available fibers and composites may meet many DoD needs. It is also likely that applications 10 to 20 years in the future for armor and spacecraft, for example, will require improved fibers and composites.
As a result of this general speculation, in 1998 the Office of Defense Research and Engineering in the Department of Defense requested that the National Research Council (NRC) undertake a study of the challenges and opportunities associated with advanced composite materials, with emphasis on high-performance fibers. The appointed committee undertook the following tasks:
Identify technological trends in the fiber industry including improved mechanical properties, low-cost process technology, and manufacturing controls.
Identify market and business trends in the carbon and high-performance organic fiber industries, including consumption volume, production capacity, and historical and projected prices as a function of product form (e.g., tow count or the number of parallel and uncut filaments in a fiber bundle) and properties.
Characterize the current state of the carbon and high-performance organic fiber manufacturing industries, both domestic and worldwide, and assess the capabilities and application priorities of fiber suppliers.
Identify probable future DoD applications of organic-matrix composites, considering performance, availability, composite processing and component design, and cost drivers. Particular attention will be placed on the relationships between cost and availability and cost and performance.
Suggest opportunities for DoD-sponsored research to advance structural fiber technologies, including those involving manufacturing process and control technologies. Means to reduce product costs of fibers and composites will be emphasized.
Suggest mechanisms for DoD to take advantage of low-cost processing and composite manufacturing innovations associated with lower-cost, higher-volume commercial applications while maintaining fiber performance, product consistency, and traceability.
The Committee on High-Performance Structural Fibers for Advanced Polymer Matrix Composites conducted an extended study of the topic, and the duration of the effort spanned a number of important changes in the fiber industry. The main focus of this document is on carbon fibers and high-performance organic fibers. Because commodity fibers—those with lower specific properties, such as glass fibers—
are not as relevant to future military systems, they are not discussed here. However, these lower-performance fibers dominate the commercial PMC market volume. For example, in 2003 the world market for carbon fiber was approximately 38 million pounds, whereas the world market for glass fiber was more than 100 times greater, approximately 5 billion pounds.8
Although the main emphasis of this study is on high-performance fibers, the committee felt it impossible to discuss the cost and performance of advanced PMCs by focusing on fibers alone; polymer matrix materials must also be considered, as well as the interface connecting the fibers to the matrix and the processing path. The characteristics of the matrix and fiber-matrix interface strongly influence the available manufacturing processes and the final properties of the PMC; therefore, these topics are also discussed here, albeit in somewhat less detail than fibers.
The committee was tasked with suggesting opportunities for DoD-sponsored research to advance structural fiber technologies. Historical experience shows that the time required for development of a new fiber, its associated manufacturing processes, testing, and incorporation into a functional composite structure is generally measured in decades. Thus, new fibers developed today are not likely to find practical application in the production of DoD systems in the next 5 to 10 years. The committee therefore divided its discussion of research and development opportunities discussion into two parts: opportunities to take advantage of existing fibers (next 5 to 10 years) and opportunities to develop new fibers and applications (beyond the next 10 years).
This report has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the National Research Council’s Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making its published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their review of this report: D. Bruce Chase, E.I. du Pont de Nemours & Company; D.J. DeLong, DeLong and Associates; Gail Hahn, The Boeing Company; James B. O'Dwyer, PPG Industries; R. Byron Pipes, Purdue University; Steve Russell, Aldila Carbon Fiber Technology LLC; and James Seferis, University of Washington.
Although the reviewers listed above have provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations, nor did they see the final draft of the report before its release. The review of this report was overseen by Eli M. Pearce, Polytechnic University. Appointed by the National Research Council, he was responsible for making certain that an independent examination of this report was carried out in accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of this report rests entirely with the authoring committee and the institution.
The committee acknowledges speakers from government and from industry who took the time to share their ideas and experiences. The following former committee members also greatly assisted the work of the current committee through their participation in many of its activities: John C. Adelmann, Sikorsky Aircraft Corporation; Lynn W. Jelinski, Sunshine Consultants, Inc.; James E. McGrath, Virginia Polytechnic Institute and State University; Paul D. Palmer, Thermo Fibergen; and George S. Springer, Stanford University. Finally, the committee acknowledges the contributions to the completion of this report from the staff of the National Academies, including Charles T. Hach, Julius C. Chang, Greg Eyring, and Bonnie Scarborough.
John W. Gillespie, Jr., Chair
Committee on High-Performance Structural Fibers for Advanced Polymer Matrix Composites