Table Of ContentOFFICE OF NAVAL RESEARCH
STRUCTURAL MECHANICS SERIES
Already published in this series:
STRUCTURAL MECHANICS, Proceedings of the First Symposium on
Naval Structural Mechanics.
Edited by J. NORMAN GOODIER AND NICHOLAS J. HOFF, 1960
PLASTICITY, Proceedings of the Second Symposium on Naval Structural
Mechanics.
Edited by E. H. LEE AND P. S. SYMONDS, 1960
HIGH TEMPERATURE STRUCTURES AND MATERIALS, Proceedings
of the Third Symposium on Naval Structural Mechanics.
Edited by A. M. FREUDENTHAL, B. A. BOLEY AND H. LIEBOWITZ, 1964
MECHANICS AND CHEMISTRY OF SOLID PROPELLANTS, Proceedings
of the Fourth Symposium on Naval Structural Mechanics.
Edited by A. C. ERINGEN, H. LIEBOWITZ, S. L. KOH AND
J. M. CROWLEY, 1967
OFFICE OF NAVAL RESEARCH
STRUCTURAL MECHANICS SERIES
MECHANICS OF
COMPOSITE MATERIALS
PROCEEDINGS OF THE FIFTH SYMPOSIUM
ON NAVAL STRUCTURAL MECHANICS
Held at the Marriott Motor Hotel,
Philadelphia, Pennsylvania
May 8-10, 1967
SPONSORED BY THE OFFICE OF NAVAL RESEARCH
AND THE GENERAL ELECTRIC COMPANY, SPACE SCIENCES LABORATORY
Edited by
F. w. WENDT
H. LIEBOWITZ
N. PERRONE
PERGAMON PRESS
OXFORD · NEW YORK · TORONTO · SYDNEY · BRAUNSCHWEIG
Pergamon Press Ltd., Headington Hill Hall, Oxford
Pergamon Press Inc., Maxwell House, Fairview Park, Elmsford, New York, 10523
Pergamon of Canada Ltd., 207 Queen's Quay West, Toronto 1
Pergamon Press (Aust.) Pty. Ltd., 19a Boundary Street,
Rushcutters Bay, N.S.W. 2011, Australia
Vieweg&Sohn GmbH, Burgplatz 1, Braunschweig
Copyright © 1970 Pergamon Press Inc.
All Rights Reserved. No part of this publication may be
reproduced, stored in a retrieval system, or transmitted, in any
form or by any means, electronic, mechanical, photocopying,
recording or otherwise, without the prior permission of
Pergamon Press Inc.
Reproduction in whole or in part is permitted
for any purpose of the U.S. Government
First edition 1970
Library of Congress Catalog Card No. 78-96061
Made in Hungary
08 006421 3
PREFACE
A LOW-WEIGHT, high-strength, high-stiffness material which can be tailored
to meet the structural requirement—these are some of the virtues which
scientists and engineers in the field of materials and structures have perennially
been searching for in a structural material. The use of the multiphase—or
composite—material promises to fulfill these needs and open up broad, new
horizons whose ultimate consequences regarding any phase of structural
engineering cannot yet be fully imagined.
The fabrication of fibrous composites, together with the achievement of
high strength-to-weight and stiffness-to-weight ratios, is a task of utmost
significance—both with respect to small-scale specimens developed to de-
termine material properties experimentally, and to full-size structural ele-
ments.
Many valid questions arise, especially at a time when more and more
emphasis is being placed on specific applications of composites. For example:
What factors influence the achievement of these high ratios of strength-
and stiffness-to-weight?
How does concentration and orientation of the reinforcement affect
strength and stiffness under various loading conditions?
What needs to be done to tailor the material so that optimum performance
can be achieved for a given requirement in a given structure?
How can these materials best be utilized to meet the requirements of a
structural system?
Several hundred scientists and engineers from the United States and seven
foreign countries, who are particularly concerned with these aspects of com-
posite development, gathered in Philadelphia, Pennsylvania, from May 8 to
May 10, 1967, to attend the International Conference on the Mechanics of
Composite Materials, co-sponsored by the Office of Naval Research and the
General Electric Company's Space Sciences Laboratory. The international
gathering offered a rare and unique opportunity for people to exchange their
ideas concerning past, present, and future work in this field.
A highlight of the conference was the International Forum, in which ex-
perts in composites from six foreign nations presented summaries of research
and development work being done in their respective countries. These talks
VI PREFACE
were of extreme interest in that they illuminated the particular areas of re-
search and interest outside of this country.
The papers presented at the conference served to intimately couple the
structural requirements of a system, whether it has naval, aerospace, or
reentry applications, to the studies that have been carried out and are currently
under way into the fundamental mechanical properties of composite materials
and structural elements made of composite materials, as well as into their
behavior under various environmental conditions.
Although the speakers represented a diversity of scientific and engineering
disciplines and their areas of interest ranged from outer space to inner space,
it was generally agreed that there are major shortcomings that remain to be
eliminated if composites are to achieve their full potential. The needs are
basically the following:
1. Reliable non-destructive testing techniques.
2. Improved methods for quality control in fabrication.
3. Better design data.
4. Improved test techniques to determine basic properties.
5. Joints and penetration procedures.
6. More research into the basic mechanisms of composite materials
(micromechanics).
7. Lower cost.
It was generally felt that the science of composites is still in its infancy and
that the problems cited will be solved.
In summary, the outstanding properties of composites, high strength and
stiffness, low density, ease of formability and the ability to tailor design, to
name a few, will have a dramatic, if not revolutionary, effect on structures in
the years to come.
Following is the complete program of the conference.
Monday, May 8
Opening Session
Welcoming Address :
Dr. Leo Steg, Manager, Space Sciences Laboratory, General Electric
Company.
Session I—Requirements
Chairman : Dr. Peter King, Chief Scientist, Office of Naval Research,
Department of the Navy
Dr. John P. Craven, Chief Scientist, Special Projects Office, Department
of the Navy, Missile and Aircraft Systems Constraints and Operational
Requirements.
PREFACE VÜ
Capt. Laurence L. Jackson, Jr., Commanding Officer, Atlantic Undersea
Test and Evaluation Center, Department of the Navy, Ship Systems
Constraints and Operational Requirements.
Mr. Norris F. Dow, Consulting Engineer, Space Sciences Laboratory,
General Electric Company, Materials, and Engineering Problems.
Session II—Applications
Chairman: Capt. Arthur M. Blamphin, Staff Member, Materials Advisory
Board, National Academy of Sciences
Prof. Albert G. H.Dietz, Department of Civil Engineering, Massachusetts
Institute of Technology, Structural Uses of Composites.
Capt. Samuel R. Heller, Jr., Director, Hull Systems and Weapons Support
Division, Naval Ship Engineering Center, Department of the Navy,
The Use of Composite Materials in Naval Ships.
Mr. Herbert S. Schwartz, Assistant to Chief, Nonmetallic Materials
Division, Air Force Materials Laboratory, Department of the Air
Force, Applications of Reinforced Plastics in Aircraft.
Dr. John D. Stewart,1" Manager, Research and Engineering, and Mr.
A. M. Garber, Manager, Structural Mechanics Laboratory Operation,
Re-entry and Environmental Systems Division, General Electric
Company, Applications of Composite Materials in Re-entry Vehicles.
Mr. Richard R. Heldenfels, Chief, Structures Research Division, Lang-
ley Research Center, National Aeronautics and Space Administration,
Applications of Composite Materials in Space Vehicle Structures.
International Forum
Mr. James E. Gordon, Explosives Research and Development Estab-
lishment, Ministry of Technology, United Kingdom, Composites Re-
search in England.
M. Jacques Duflos, Directeur Commercial, Pierre Genin & Cie, France,
French Developments in the Field of Thermal-resistant and Mechanical
Composites.
Prof. Ulrich Hütter, Institut für Flugzeugbau, Technische Hochschule
Stuttgart, Germany, Composites Research in Germany.
Tuesday, May 9
Session III—Micromechanics
Chairman : Prof. Daniel C. Drucker, Engineering Division, Brown University
Prof. Zvi Hashin, Division of Engineering Mechanics, University of
Pennsylvania, Theory of Composite Materials.
Prof. Mark J. Beran, Towne School of Civil and Mechanical Engineering,
University of Pennsylvania, Statistical Theory of Heterogeneous Media.
t Dr. Stewart was not able to present his paper at the conference; however, the full
text of his paper is included in these Proceedings.
viii PREFACE
Prof. Maurice A. Brull, Division of Engineering Mechanics, University
of Pennsylvania, Stress-Strain Relations for Composite Materials in
Shells of Arbitrary Geometry.
Prof. August J. Durelli,t Prof. V. J. Parks, Mr. H. C. Feng, Dr. F. P.
Chiang, Civil Engineering and Mechanics Department, The Catholic
University of America, and now Assistant Professor at the State
University of New York (Stonybrook), Strains and Stresses in Matrices
with Inserts. Prof. George Herrmannt and Prof. Jan D. Achenbach,
Department of Civil Engineering, Northwestern University, Wave
Propagation in Laminated and Fiber-reinforced Composites.
Prof. Rene B. Testat and Prof. Bruno A. Boley, Department of Civil
Engineering and Engineering Mechanics, Columbia University, Basic
Thermoelastic Problems in Fiber-reinforced Materials. Prof. Severino
L. Koh, School of Aeronautics, Astronautics and Engineering Sciences,
Purdue University, Continuum Theories for Composite Materials.
Session IV—Structural Mechanics
Chairman: Dr. Nicholas Perrone, Acting Head, Structural Mechanics
Branch, Office of Naval Research, Department of the Navy
Dr. John Hedgepeth,t Vice-President, Engineering, Astro Research
Corporation (formerly Assistant Director for Engineering, The Martin
Company), and Dr. Donald F. Haskell, Staff Consultant, Fairchild
Hiller, Space and Electronic Systems Division (formerly Staff Engineer,
Martin Marietta Corporation), Structural Mechanics of Fiber-reinforced
Composites.
Mr. Max E. Waddoupst and Mr. James R. Blacklock, Senior Structures
Engineers, General Dynamics Corporation, The Application of Finite
Element Stiffness Matrix Analysis for Composite Structures.
Mr. Kenneth Horn, Head, Structures Evaluation Branch, Submarine
Structures Division, Naval Ship Research and Development Center,
Fiber-reinforced Plastics for Hydrospace Applications.
Dr. Kenneth R. Berg, Chief, Structural and Mechanical Engineering,
Whittaker Research & Development Division, Problems in the Design
of Joints and Attachments.
Mr. Louis A. Riedinger,t Manager, Structures Division, Mr. Murât H.
Kural and Mr. George W. Reed, Jr., Structures Division, Lockheed
Missiles and Space Company, Evaluation of the Potential Structural
Performance of Composites.
Prof. Ulrich Hütter, Institut für Flugzeugbau, Technische Hochschule
Stuttgart, Germany, Optimization of Shell Structures Under Bending
and Torsion Loads.
f Indicates speaker.
PREFACE IX
Prof. Lucien A. Schmit, Jr., Professor-in-Charge, Solid Mechanics, Struc-
tures and Mechanical Design, Case Institute of Technology, The Struc-
tural Synthesis Concept and Its Potential Role in Design with Compos-
ites.
Dr. Hans Schuerch, President, Astro Research Corporation, Advanced
Concepts for Composites.
Wednesday, May 10
Session V—Failure Mechanics
Chairman: Dr. George R. Irwin, Supervisor, Mechanics Division, U.S.
Naval Research Laboratory, Department of the Navy
Dr. B. Walter Rosen, Consulting Engineer, Space Sciences Laboratory,
General Electric Company, Strength of Uniaxial Fibrous Composites.
Mr. Phillip W. Mast, Mechanics Division, U.S. Naval Research Labo-
ratory, Department of the Navy, Fracture Volume Changes in Laminat-
ed Orthotropic Materials.ΐ
Dr. George A. Coopert and Prof. Anthony Kelly, Department of Metal-
lurgy, University of Cambridge, England, The Contribution to the Work
of Fracture of a Composite Material of "Pull-out" of Fibers.
Prof. Sol R. BodnerÎ and Prof. J. M. Lifshitz, Department of Mechanical
Engineering, Technion — Israel Institute of Technology, Experimental
Investigations on the Dynamic Strength of Composites.
Dr. William J. Douglas,t Senior Analyst, Keystone Computer Associ-
ates, and Prof. Walter Jaunzemis, Department of Engineering Mechanics,
Pennsylvania State University, Stability of Prestrained Laminated Media.
Dr. Robert Heller, Professor of Engineering Mechanics, Virginia Poly-
technic Institute (formerly Deputy Director, Institute for the Study of
Fatigue and Reliability, Columbia University), Mechanical Properties
of Wire-reinforced Grains.
Dr. Larry S. Shu, Research Scientist, Space Sciences Laboratory, General
Electric Company, The Evaluation of the Strength of Fiber-reinforced
Composites.
Dr. Frederick W. SchmiedeshofT, Director of Research, Benet Research
& Engineering Laboratories, Watervliet Arsenal, U.S. Army Weapons
Command, Elastic Interface.
Session VI—Environmental Interaction
Chairman: Mr. James E. Gordon, Explosives Research and Development
Establishment, Ministry of Technology, United Kingdom
Dr. Stephen W. Tsai, Professor and Director of Materials Research
t This paper is not available for publication in these Proceedings.
} Indicates speaker.
X PREFACE
Laboratory, Washington University, Environmental Factors in the
Design of Composite Materials.
Dr. Frederick L. Schuyler,t Principal Scientist, Theoretical Fluid Phys-
ics, Space Sciences Laboratory, and Dr. Edward Friedman, Solid
Mechanics Laboratory Operation, Re-entry Systems, General Electric
Company, High-temperature Ablation Interaction.
Dr. Sam Brelant,î RESEP Project Engineer, Aerospace Corporation,
and Mr. Ira Petker, Senior Engineer, Composites Technology Section,
Aerojet-General Corporation, Fabrication and Environmental Inter-
action Effects of Filament-wound Composites.
Mr. Nathan Fried, Head, High Strength Plastics Program, U.S. Naval
Applied Science Laboratory, Department of the Navy, Degradation of
Composite Materials : The Effect of Water on Glass-reinforced Plastics.
International Forum
Mr. Tadashi Tao, Chief Chemical Scientist, Nagoya Aircraft Factory,
Mitsubishi Heavy Industries, Ltd., Japan, Composites Research in Japan.
Mr.Karl-Axel Olsson, Research Engineer, Division of Aircraft Structure,
Royal Institute of Technology, Sweden, Composites Applications and
Research in Sweden.
The editors wish to express their sincere appreciation for the splendid co-
operation received from the authors and session chairmen, not only in prep-
aration of the presentations, but also in subsequent revisions and editorial
polishing of the proceedings. A special note of thanks to the participants
from abroad who helped to make the conference a memorable event with
fresh viewpoints and highlights of composite material application in their
respective countries.
Few words can express the dedication to minute detail and tireless follow-up
that was so evident in the smooth handling of conference correspondence
and other secretarial work by Mrs. Barbara Walker and Mrs. Dolores Novak
—all the way from the planning stage to documentation of the proceedings.
A special word of thanks also belongs to Mr. Ted Ryan and his capable
staff of the Laboratory Publications and Information office within the Space
Sciences Laboratory, among them Mr. Charles De Julius for behind-the-
scene organizational efforts and certainly the editorial support from Mr. Jack
Wood, Mr. Paul Klatt, Miss Betty Keeley and Mr. Abner Harrison.
FREDERICK W. WENDT
HAROLD LIEBOWITZ
NICHOLAS PERRONE
f Dr. Schuyler was not able to present his paper at the conference; however, the full
text of his paper is included in these Proceedings.
t Indicates speaker.
WELCOMING ADDRESS
DR. LEO STEG
Space Sciences Laboratory, General Electric Company,
Philadelphia, Pennsylvania
IT is my pleasure to greet you in the name of the General Electric Company.
I feel particularly close to this meeting because the topic of structures is
within my own professional interests. I see a number of colleagues in the
audience. The Structural Mechanics Group of the Office of Naval Research
seems to have remarkable insight in electing very promising topics for its
international conferences. I doubt that the structures community could
discuss a more consequential topic than the present one. The idea that an
almost arbitrarily anisotropic material can be put together and used for
structure design permits removal of the age-old constraint of materials prop-
erties; one can now truly achieve optimization. If any of you have ever
tried optimization without this constraint, you will find it stimulating. The
impact on structures, whether they be aircraft or naval structures, is very
impressive. There is an F-lllB flying about with a significant amount of
boron filaments in load-bearing structures. It is doing very well—with a
substantial weight saving—and I just wonder how much structural design
has gone into this aircraft, particularly with respect to the boron filaments.
When I have talked with the people who build these airplanes they say that
they look for major contributions from the structural community furnishing
the design criteria. In fact, I think that before the year is out, composite ma-
terials will be in rather wide supply at much lower cost. It is very appropriate
that the limelight and the pressure now shift from the materials community
onto the structures community and that the question as to how to design
with these materials be thoroughly explored. So I don't think I could open
this meeting with a better thought than that I think we are due for a renais-
sance in the structures field. I'm pleased to be here and have G.E. join the
Navy in welcoming you to this meeting.
Thank you very much.
