REFRACTORY MATERIALS A SERIES OF MONOGRAPHS John L. Margrave, Editor DEPARTMENT OF CHEMISTRY RICE UNIVERSITY, HOUSTON, TEXAS VOLUME 1. L. R. MCCREIGHT, H. W. RAUCH, SR., and W. H. SUTTON Ceramic and Graphite Fibers and Whiskers A Survey of the Technology VOLUME 2. EDMUND K. STORMS The Refractory Carbides VOLUME 3. H. W. RAUCH, SR., W. H. SUTTON, and L. R. MCCREIGHT Ceramic Fibers and Fibrous Composite Materials CERAMIC FIBERS AND FIBROUS COMPOSITE MATERIALS H. W. Rauch, Sr., W. H. Sutton, and L. R. McCreight SPACE SCIENCES LABORATORY GENERAL ELECTRIC COMPANY KING OF PRUSSIA, PENNSYLVANIA 1968 ® Academic Press New York and London COPYRIGHT © 1968, BY GENERAL ELECTRIC COMPANY ALL RIGHTS RESERVED. NO PART OF THIS BOOK MAY BE REPRODUCED IN ANY FORM, BY PHOTOSTAT, MICROFILM, OR ANY OTHER MEANS, WITHOUT WRITTEN PERMISSION FROM THE PUBLISHERS. ACADEMIC PRESS, INC. Ill Fifth Avenue, New York, New York 10003 United Kingdom Edition published by ACADEMIC PRESS, INC. (LONDON) LTD. Berkeley Square House, London W.l LIBRARY OF CONGRESS CATALOG CARD NUMBER: 68-57514 PRINTED IN THE UNITED STATES OF AMERICA PREFACE The purpose of this book is two-fold. First, it supplements and updates the information on ceramic and graphite fibers and whiskers which was pre­ sented in Volume 1 of the Refractory Materials Monograph Series. Secondly it reviews the progress being made in fiber-reinforced materials which utilize these newer fibers as reinforcements. For this latter purpose, the properties of composites, the problems of fiber handling and alignment, the problems of fiber-matrix interaction, and the effects of fabrication processes on composite properties are discussed. In addition, a chapter on fiber and whisker testing is included. The extensive effort in fibers and fiber-reinforced materials for aerospace structural applications has generated vast amounts of published information. Recognizing the need for collecting this information and presenting it in a unified, comprehensive form, the Air Force Materials Laboratory, Wright- Patterson AFB, Ohio, engaged the General Electric Company's Space Sci­ ences Laboratory to perform this service.* This book is a result of that support and represents the assistance of many persons whom the authors gratefully acknowledge as follows: Messrs. B. R. Emrich and S .W. Bradstreet for their assistance in obtaining reports, samples, and contacts with many per­ sonnel engaged in fiber and composite technology. Capt. J. A. Snide, Messrs. R. M .Neff, and S. Schulman for critically reviewing the manuscript. Dr. Louis Navias, Consultant and retired "Dean of Ceramics" in the General Electric Company, for his patent abstracting and general consulting. Mr. R. L. Mehan for preparing Chapter IV on testing fine filaments and whiskers. Messrs. K. E. Paschall and J. H. Wood for editing the manu­ script. »Contract AF 33(615)-3278 v VI PREFACE Each of the many personnel in over ninety organizations who contributed information to the survey. H. W. Rauch, Sr. King of Prussia, Pennsylvania W. H. Sutton July 1968 L. R. McCreight LIST OF FIGURES 1. Interest in fiber and fiber-reinforced materials based upon the number of publications listed in the Bibliography and in Ref. 475 2 2. Potential specific strength and specific modulus of conven­ tional alloys and advanced fiber-reinforced composites at room temperature 7 3. Scope of fiber-composite technology 8 4. Role of the constituents in fiber-composite materials . . .. 10 5. Characterization of reinforcements according to morphology 13 6. Comparisört{of the cross-sectional dimensions for various fiber reinforcements (from Ref. 702) 14 7. Flow chart of rayon yarn production (Courtesy of Food Machinery Corp.) 17 8. Effect of forming process on the strength of various fibers . . 22 9. Room temperature specific strength and specific stiffness of several fibers 25 10. Elevated temperature strength of several fibers 25 11. Cross-section (unetched) and surface appearance of a fractured boron/tungsten filament (600X) 29 12. Photomicrographs of alumina whiskers showing complex cross sections and oblique fracture (Ref. 579) 30 13. Effect of gage length on the elastic modulus of steel and tungsten wire. Data obtained from an Instron machine using aluminum-lined air grips (80 psi), a rigid coupling system, and a "C" load cell 33 14. View of a boron filament held between Instron-type air grips during a tensile test 35 15. Marsh machine with Thornel-25 fiber mounted ready for test 38 ix LIST OF FIGURES 16. Schematic sketch of Air Force Materials Laboratory micro- tensile testing machine (Courtesy of Herzog, Ref. 311) . .. 39 17. Fiber tensile testing fixture (Courtesy of Kelsey and Krock, Ref. 380) 40 18A. Compilation of strength of Al 0 whiskers as a function 2 3 of cross-sectional area (Ref. 494) 42 18B. Strength of metal-coated A1 0 whiskers extracted from 2 3 an aluminum matrix (Ref. 494) 43 19. Deviation from simple theory for maximum bending deflection of high-strength, high-modulus fibers (Courtesy of Jour. American Ceramic Society. Ref. 492) 44 20. Photomicrographs of bent A1 0 whiskers used to evaluate 2 3 whisker stress 46 21. Relationship of composite tensile strength to fiber aspect ratio, and to fiber volume fraction 50 22. Strength of carefully selected alumina whiskers as a function of size (from Regester, Ref. 579) 54 23. Effect of fiber orientation on the uniaxial tensile strength of fiber-composite material (from Kelly and Davies, Ref. 374) 56 24. Interfacial shear stress and fiber tensile stress of an elastic fiber in an elastic matrix 61 25. Wetting of A1 0 substrates by molten aluminum. In A and 2 3 B, the A1 0 was uncoated; in C and D, the A1 0 was coated 2 3 2 3 with an adherent film of nickel (from Mehan, et al., Ref. 493) 62 26. Strength of silver composites containing Ni-coated and un­ coated A1 0 whiskers (from Sutton, Ref. 705) 63 2 3 27. Effect of fiber strength and fiber volume fraction on composite tensile strength 64 28. Tensile stress-strain relationships for the matrix, fiber, and composite material 66 29. Hollow ring-stiffened cylinder of boron-filament epoxy construction (from Saffire, Ref. 611) 72 30. Strength retention at various temperatures of pure aluminum and aluminum strengthened with A1 0 particles and with 2 3 fused silica fibers (from Sutton and Chorne, Ref. 708) . .. 81 31. Strength retention at various temperatures of pure silver strengthened with A1 0 particles and whiskers (from 2 3 Sutton and Chorne, Ref. 708) 82 LIST OF FIGURES XI 32. Effect of fiber volume fraction on the tensile strength of metal-matrix composites reinforced with continuous, parallel fibers (from Sutton, Ref. 702) 83 33. Effect of fiber volume fraction on the tensile strength of metal-matrix composites reinforced with discontinuous, parallel fibers (from Sutton, Ref. 702) 84 34. Effect of fiber volume fraction on the modulus of Ti-6A1-4V alloy at various temperatures (from Jech, et al., Courtesy of Interscience Pub., Ref. 356) 86 35. Creep strain of Inconel 600 reinforced with different volume fractions of tungsten fibers (from Ellison and Harris, Courtesy of Appl. Materials Res., Ref. 209) 87 36. Ultimate tensile strength of boron-filament aluminum composites as a function of filament volume fraction (Courtesy of United Aircraft Research Laboratories, AF Contract No. AF33(615)-3209, Contact Rept. No. 87). . 91 37. Strength-to-density ratio as a function of temperature for specimens of plasma-sprayed boron-filament reinforced aluminum and other alloys (Courtesy of United Aircraft Research Laboratories, Contact Rept. No. 87) 92 38. Photomicrograph of a transverse section of a composite of aluminum containing B C/tungsten core filaments. Specimen 4 was prepared by infiltrating molten aluminum into 84 v/o of BC filaments 93 4 39. Composite specimen of aluminum reinforced with 30 v/o of A1 0 whiskers. At one end, the aluminum was dissolved 2 3 to expose the whiskers 94 40. Transverse section of aluminum matrix composite specimen containing 27 v/o of A1 0 whiskers 95 2 3 41. Whisker-reinforced nickel sheet which was fabricated by electro-depositing nickel into a mat of Ni-coated A1 0 2 3 whiskers (Ref. 151) 97 42. Strength dependence on temperature for various metal- matrix composites 98 43. Turbine blade configuration cast directly by unidirectional solidification of A1-A1 Ni eutectic alloy (Courtesy of United 3 Aircraft Research Lab., Contact Rept. No. 87) 100 44A. Hot-formed carbon-fabric aluminum composite (Courtesy of Aeronutronic Division, Ford Motor Co.) 118 xii LIST OF FIGURES 44B. Cross-section of Thornel 25 fibers in 2024 aluminum matrix (Courtesy of Aeronutronic Division, Ford Motor Co .118 45. Specimens fabricated using 3-D weave process (Courtesy of AVCO Corp.) 128 46. Structure of boron-fiber reinforced titanium formed by gas pressure bonding (Courtesy of Battelle Memorial Institute) . 135 47. Boron-fiber reinforced titanium formed by explosive com­ paction (Courtesy of Battelle Memorial Institute) 135 48. Nickel - 60 v/o WDF graphite felt (Courtesy of Battelle Memorial Institute) 136 49. Nickel - 77 v/o Thornel graphite yarn (Courtesy of Battelle Memorial Institute) 136 50. Effect of growth direction on A10 whisker strength 2 3 (Courtesy of CFTH) 150 51. Hollow, hexagonal cross-sections of glass microtape reinforced resin (Courtesy of DeBell & Richardson, Inc.) . . 153 52. Various composites made with hollow, hexagonal cross-section microtapes (Courtesy of DeBell & Richardson, Inc.) . . .. 154 53. Boron-fiber reinforced F-l 11 tail section (Courtesy of General Dynamics Corp.) 161 54. Microstructure of epoxy reinforced by A103 whiskers . .. 167 2 55A. Nickel - 10 v/o quartz fiber; tapes and wires (Courtesy of Hittman Associates, Inc.) 185 55B. Cobalt -10 v/o quartz fiber; cone and nozzle (Courtesy of Hittman Associates, Inc.) 185 56. Cobalt-quartz fiber composite (64X) (Courtesy of Hittman Associates, Inc.) 186 57. Deformation pattern in a silver matrix containing a single 5-mil diameter, 20-mil long tungsten fiber (Courtesy of IITRI) 190 58. Strain hardening in the silver matrix along a 60-mil long tungsten fiber (Courtesy of IITRI) . . . . , 191 59. Length distribution of A1 0 whiskers (Courtesy of 2 3 P. R. Mallory & Co., Inc.) 196 60. Strength of A1 0 whiskers as a function of cross-sectional 2 3 area (Courtesy of P. R. Mallory & Co., Inc.) 197 LIST OF FIGURES Xlll 61. Microstructure of experimental aluminum-copper alloy as cast in machined graphite molds. Note appearance of 10-30 micron diameter aluminum oxide fibers at the grain bound­ aries (680X) (Courtesy of Mitron R & D Corp.) 201 62. Schematic of Rolls-Royce process for simultaneous drawing and metallizing Si0 fiber (Courtesy of Rolls-Royce, Ltd.). . 221 2 63. Comparison of ultimate tensile strength of silica fiber-rein­ forced aluminum with various other aluminum alloys (Courtesy of Rolls-Royce, Ltd.) 222 64. Comparison of bending fatigue strength of silica fiber-rein­ forced aluminum and a widely used aluminum alloy (Courtesy of Rolls-Royce, Ltd.) 223 65. Stress-rupture properties at various temperatures for silica fiber-reinforced aluminum (courtesy of Rolls-Royce, Ltd.). . 224 66. Anisotropy of Al-Al Ni composite demonstrated by tensile 3 strength measurements parallel to and at various angles to whisker alignment (Courtesy of United Aircraft Corp.) . . . 239 67. Creep behavior of Al-Al Ni at 250°C, 15,000 psi (Courtesy 3 of United Aircraft Corp.) 240 68. Effect of temperature on the tensile strength and ductility of unidirectionally solidified Al-Al Ni and Al-CuAl 3 2 (Courtesy of United Aircraft Corp.) 241 69. Microstructure of Ta-Ta C alloy (A65-067) unidirectionally 2 solidified two times (Courtesy of United Aircraft Corp.) . . 242 70. Effect of temperature on the tensile properties of Ta-10W and unidirectionally solidified Ta-Ta C (Courtesy of 2 United Aircraft Corp.) 243 71. Effect of reinforcement shape on mechanical properties of unidirectionally solidified composites (Courtesy of United Aircraft Corp.) 245 72. Whiskers of j3-rhombohedral boron (4X) (Courtesy of Watervliet Arsenal) 254 73A. Iron whiskers grown in magnetic field (3 kilo-oersteds) on a nonmagnetic spiral placed in a boat (Courtesy of Watervliet Arsenal) 255 73B. Close-up view of iron whiskers in the boat, showing alignment and absence of over-growth (Courtesy of Watervliet Arsenal) 256