ASSESSMENT OF CARBON-CARBON COMPOSITE RESEARCH IN THE FAR EAST Dr. Robert A. Meyer conducted this study for the Office of Naval Research between December 1990 and March 1991. His trip to the Far East included visits to six universities and seven research institutes in Japan, Taiwan, China, Korea, Australia, and India. He also attended a meeting of the China Association of Science and Technology in Beijing. This report summarizes Dr. Meyer's observations and assessments from his visits to these organizations and attendance at the meeting. INTRODUCTION The potential for utilizing carboncarbon composite (C/C) materials is large because of carbon's unique physical properties. For example, one form of carbon is graphite, which has high specific strength and stiffness values at temperatures in excess of 2,000 °C, zero or negative thermal expansion values between ±200 °C, and low outgassing characteristics. Thus, C/Cs, which contain large portions of graphite, are an excellent material for space applications. Another advantage of using C/Cs is the ability to change the material's physical properties by altering the type and distribution of yarns and to vary the microstructure of the matrix that exists within and between these yarns. This ability to fabricate composites with different types of characteristics enables the designer to select and obtain the proper type of material that will withstand specific adverse environments. The United States has been very successful in translating engineering requirements and process "know-how" into C/Cs with good operating characteristics. But this success is costly. In some cases, the improvements are accomplished by means of scaling up by Robert A. Meyer the processing and fabricating procedures in a step-by-step developmental manner from small laboratory size samples to very large and full-scale hardware. In other situations, previous manufacturing experience is used to modify an existing process by making small incremental changes over an extended period. With either approach, the large pieces of hardware are very costly because of the materials they contain and the months of time it takes to fabricate them. Obviously, failure to properly make one of these pieces or to have it "destruct" during its operation is unacceptable. Some of these failures have been attributed, in part, to a lack of knowledge. Either the material's true physical properties were not used for defining the design criteria or the most important parameters for the control of the process were not identified to insure the desired physical properties and high degree of reproducibility from piece to piece. Furthermore, the need for improved processing control is becoming more critical because the C/Cs are now required to function under more severe operating conditions. As these requirements become more extreme, it is necessary to have a better understanding of the influence of the composition of the C/C on its behavior. Such information is derived from more research activity so that further directions for research and development (R&D) and alternative processes can be defined for obtaining the desired properties in a more economical manner. Unfortunately, the financial support for C/C research efforts in the United States has been steadily declining for the past 8 or more years. This means the enhancement of C/C properties has and does occur in a limited way by gradually changing current processing conditions using one of the two approaches already described. Another impact of using these approaches is that of not having available sufficient research information to improve the possibilities that unique, original, and significantly large advances can be made. This also means the technology that is currently being used is derived from research data that were probably obtained 5 or more years ago. If this situation continues to exist, the lack of research information will eventually limit the ability of the United States to develop improved C/Cs, not only for our use but in competition with foreign countries. The questions that naturally arise are: What should be done? and Is the United States ahead, equal, or behind other countries in its research capabilities and knowledge for developing advanced C/Cs in a timely manner? This assessment study and interpretive report is being undertaken for the purpose of providing information to be used in answering these questions and to assist in formulating future program plans for research efforts in this field. OBJECTIVE The overall objective of this survey is to evaluate the current status and to estimate the future directions of foreign research efforts that are being conducted in the area pertaining to carbon-carbon composite materials and related technologies. Based on this evaluation, a general assessment will then be prepared concerning the expected impact that these foreign activities could have on the research and development capabilities of the United States for producing advanced C/Cs in the long term. APPROACH The major thrust in gathering information for this report was directed towards those areas of research that are considered to have the greatest potential impact for improving the performance of C/Cs. This means first priority was given to the areas of fibers, their architecture in woven forms, processing and densification methods, the influence of matrix microstructure to physical properties, bonding phenomena, and characterization methods. Other interesting areas of research activity were also included when it was possible. This survey is organized into two major categories: (1) the country where the research organization is located and (2) whether each organization is directly supported by a university, the government, or industry. This categorization permits comparisons to be readily made of the research efforts as be included that are concerned with oxidation resistance efforts as they are applied to C/Cs. The process used for selecting the REPORTING FORMAT The type of information that was Some information is also included est relative to the objectives of this A specific format is used for presenting the information that is obtained from each organization to provide as uniform and complete information as possible so that comparisons can be made between them. The format is divided into three sections: Background, Program Status, and Assessment. The Background section is to acquaint the reader with the past and current thrusts of the organization and who the primary research leaders are in the organization. It is hoped this information will enable the reader to understand some of the reasons for the existence of the various types of research programs that are being conducted at each site. The Program Status section contains information about the current activities of each organization. In particular, unique results or experimental approaches will be cited as well as a synthesis of the relevant discussions. The technical depth of the discussions with the individual investigators will depend on the availability of the investigators' time as well as the number of activities that are to be discussed in the allotted time for each site visit. The third part is the Assessment section. In it the research capabilities of each organization will be discussed in terms of its current and possible future contributions to the field of C/Cs and related technology. The possible impact of these capabilities on the Department of Defense's (DOD) C/C and technology research programs will also be included as well as the possibilities and advantages of using the visited organizations' strong points to augment the DOD's own technical capabilities through international cooperation programs. MUSASHI INSTITUTE OF TECHNOLOGY Carbon Research Laboratory 1-28-1 Tamazutsumi Background The host for this site visit was Prof. Yoshihiro Hishiyama, who is in charge of the Carbon Research Laboratory in the Physics Department at this institute. Hishiyama has been here for more than 26 years and is a senior staff member. The institute was started as an engineering school about 40 years ago when the Japanese Government expanded its educational program beyond the national university system that had been in existence before World War II. The institute is privately funded and has more than 4,000 students, of which 200 are graduate students. Hishiyama's primary area of research is in the solid state physics of carbon and, in particular, the electrical characteristics of carbon as determined by its structure from <1.2 K to >2,600 K. His group consists of an associate professor, four graduate students, and six part-time undergraduate students. Hishiyama is considered to be Japan's best researcher in the field of magnetoresistance and in the definition of the crystalline structure of carbonaceous systems through the use of electron microscopic techniques. He also uses other electrical characterization techniques such as measuring the Hall coefficient, resistance, and thermoelectric power to help define the structure. Hishiyama was a postdoctoral fellow at the University of Buffalo for over a year in the mid-1960s under the direction of Prof. S. Mrozowski. It was here that Hishiyama started his studies in magnetoresistivity and was the first in Japan to conduct such research. Program Status A current area of research interest is the electrical properties of pure carbonaceous systems. The samples are rather unique in that they are derived by the pyrolysis of scotch tape where the heating rate is 400 °C per hour to a maximum temperature of 1,000 °C. This method produces a very thin film of pure carbon upon which four very thin electrical leads are fastened to it by a gold film derived from a suspension of gold particles in a solvent that is evaporated, at room temperature, after it is applied at the junction of the wire and the sample. Another area of research is the characterization of the crystalline structure by advanced scanning electron microscopy (SEM) methods where low voltages of ́1 kV are used with a new method of electron detection using a lens field emission electron gun that has a resolution capability down to 3 nm rather than the current value of 10 nm that is attained at 10 kV with today's technology. The use of the lower voltage has the added advantage that the incident electrons do not penetrate as much into the sample and therefore provide a more accurate representation of the sample's topography. Between the better resolution power and the fidelity of depicting the surfaces, there is a great deal more information available about the microstructure and its changes with processing conditions. This type of processing conditions. This type of information is most valuable in furthering the understanding about the microfracturing behavior of these crystallites. Another investigation is concerned with the effects of heat treatment temperatures on the electrical properties of neutron irradiated graphite crystals. The sample sizes are about 2 x 4 x 20 mm and these samples contain grain sizes between 10 and 1,000 Å. In these studies it is assumed that the grain size distributions are similar among all the samples that were measured. These studies are being conducted using annealing temperatures between 700 and 1,000 °C. The current data indicate that the changes to the electrical characteristics of the samples are due to the scattering of electrons by interstitial carbon atoms that have been displaced from their normal positions in the crystal structure by the reactor neutrons. Apparently, the electrical resistance and magnetic resistance measurement techniques are sufficiently sensitive to detect 20% changes in values with only a small amount of reactor exposure on the order of 1 million neutrons per square centimeter. The laboratory capabilities at this institute are very adequate to support the carbon research that is being conducted. Most of the high precision and sophisticated electrical characterization equipment is in Hishiyama's laboratory. This includes two pieces of magnetic resistance equipment that operate between 1.2 and 300 K in a field of 1 T (11 kg/cm2). This magnetic field strength can be increased by more than sixfold using superconducting magnets. In addition to the measuring equipment, there is a capability to heat treat samples to more than 2,900 °C in a graphitization furnace that is now in the process of being reactivated. To better understand the physics of these carbonaceous materials, some samples are prepared and measured with the intent of having the highest degree of perfection of the graphite crystal structure within them. Consequently, these samples can be as small as 2 x 3 x 0.5 mm because the grain size is small even with some of the largest crystals of graphite that are available. These have been derived from a special supply of Kische metal that Hishiyama obtained many years ago. In spite of the very small sizes, the samples are cut and shaped with dental tools so that they have uniform cross sections and thicknesses as well as four tabs so that wires can be fastened to them with which to make voltage and current measurements. Obviously, great care must be taken in shaping each sample, not only because of its small size but because of the very limited supply of the raw material. Therefore, Hishiyama is the only person that prepares these types of samples. result, companies will acquire equipment A centralized laboratory facility also exists at this institute that provides special types of analytical equipment that are very costly and would be difficult to obtain and fully utilize, on a cost effective basis, by any single department. In this manner, individual investigators have available to them special capabilities when they are needed and pay only for the amount of service that is rendered. In addition, this facility is staffed with specially trained operators who operate the equipment, prepare samples, and analyze the data. These persons are usually undergraduate or graduate students. Apparently, this method of operation is effective because Assessment in the 8 years of its operation, this central facility laboratory has never had an accident or lost a piece of equipment due to faulty operating methods. The whole spectrum of equipment includes a 60-kV, 18-kWxray; numerous SEMS, including one with the most recently available new high resolution features; infrared (IR) spectrometers; ultraviolet (UV) spectrometers; transmission electron spectrometers (TEMs); along with other analytical tools and the appropriate data processing capabilities. This approach of having a central facility for first rate equipment is a partial answer by the university to the competition that exists between the universities and the big industrial corporations that have available the most up-to-date facilities. In discussions with Hishiyama, some further insight was obtained about the limited amount of communication that can exist between universities and industrial organizations in Japan. This seems to be the result of fierce competition within the industrial community. As a Physics and Chemistry of Carbons, which is edited by Prof. Thrower of Pennsylvania State University. To my knowledge there is no one in the United States who is now conducting the type and depth of research that is being performed by Hishiyama. Therefore, it is considered important that continued awareness be maintained of his work. If possible, it is recommended that some sort of cooperative research be initiated with this group which, according to Hishiyama, would be welcomed. One suggestion of a possible area might be to investigate the potential of using electrical measurements to characterize the microstructures of graphites and carboncarbon composites for the purpose of developing their optimum properties as is being done in Russia. The U.S. contribution could be to evaluate the applicability of this fundamental information for R&D purposes. TOHO RAYON Mishima Plant 234 Kamitogari, Nagaizumi-cho Prof. Hishiyama is clearly devoted Hishiyama's research work is known My host was Kozo Tanaka, who is the director and general manager of the entire Mishima Plant. Toho was started in 1934 as a producer of acrylic fibers for textile manufacturers, and today they are still the major customer. However, Toho has enlarged its product line. In 1968 the rayon base fiber development program was initiated; in 1971 the pilot plant was started, and these fibers with high strength and strain properties were available as a commercial product in 1975. Now prepregs are available for Japan are limited because of the fierce competition between corporations and the laws that exist as to how financial support is to be given to the university system. Toho appears to have very limited interactions with the carbon brakes, because of its desire to enter this field and because the Japanese feel the United States is the leader in engineering and producing C/Cs on a large scale. organic and carbon matrix composites and for the densification and production of composites, including C/Cs. The production rates are 4,000 tons/mo for acrylic and rayon fibers, 170 tons/mo for carbon fibers, and 4,000 tons last year for all the fibers that were pro- community. The only organization of Program Status duced. It was also stated that Toho is the largest producer of fibers in Japan, with a total capacity of 10,000 tons/yr. Toho weaves about 5,000 m2/mo and prepregs 200,000 m2/mo of unidirectional, roving, and fabric materials. The company has about 2,000 2,000 employees, of which 25% percent are at this Mishima site. In this plant all portions of the fabrication process are performed, from manufacturing of the fibers and precursors for densification, to weaving of the preforms, to impregnation and final heat treatment steps. General business objectives are to market the company's products world wide. To do this, Toho licenses and has cooperative agreements with organizations in different parts of the world, such as NARMCO in the United States, which buys Toho's prepreg, and BASF in Germany, where there is a joint venture concerning fibers and prepreg. Toho is continually trying to expand its worldwide market and considers Hercules and Amoco to be its main competitors outside of Japan and Toray to be the major one in Japan. Some of the areas that utilize carbon fibers include low inertia rollers, high speed spinning pots, bicycles, prestressed concrete for buildings and bridges, nickel-coated fibers for electrical magnetic shielding for laboratories and testing rooms and, of course, sportswear. The primary market that is now being targeted is the aerospace and aeronautical industry, especially in the United States, where Boeing is considered the largest user of carbon fibers. Toho is actively preparing for the future needs of the automotive industry. Communication and interactions between industrial organizations in which it is an active member is the New Carbon Forum. This forum is supported by over 30 of the largest industrial organizations in Japan. Its purpose is to determine applications of carbon systems in all areas of technology, i.e., systems in all areas of technology, i.e., aerospace and aeronautics, biology, construction, medicine, power, etc. This is a very active and costly operation that conducts studies and seminars, reports on new possible areas, provides translations, etc. The forum is divided into many committees and subcommittees that meet in some form or other on a monthly basis in a particular area. There is no equivalent organization in the United States where information is exchanged so frequently and in such a broad and in-depth basis. Government financial support is not actively sought by Toho because the acquisition of this type of money is unpredictable and is of a short term nature of only a few years. Also, it means a lot of the technology that was obtained with corporate funds must be revealed if support is received from the Government. Cooperative programs between companies rarely occur; if they do, they are usually between subsidiaries within the same corporation or as part of a consortium that has been formed to obtain government funds. This same attitude also exists relative to cooperative programs with organizations from other countries. At this time, there is no real interest in cooperative programs with organizations in the United States in the area of carbon fibers because Toho believes it has more information in this area than anyone else so there is nothing to exchange. Its attitude is different with respect to C/Cs, especially concerning aircraft Toho's overall approach toward research is to develop new products or to increase the reliability and production capability of existing products. There are two laboratory organizations in the company. The Mishima Plant consists of about 60 members, of which 20 have Ph.D. or master's degrees, 20 have bachelor degrees, and the rest are technicians and support people. The general method that is used for the development of a new area, such as a fiber or an impregnant, is the "Edisonian" approach. This means very small changes are very carefully made to the particular process being studied and its effects are observed in the smallest detail. In this manner, the variations or "causes" due to any changes to the process are understood as an "effect" on the product even though the precise phenomenology is not understood. Fundamental research directions are used occasionally if they have the potential of resulting in the development of advanced products. Sometimes employers support their employees who are students at the universities where they perform fundamental research studies that have a corporate goal. More often, the corporation gives the universities money for the general support of students that are studying under a particular professor or in a department where the corporation is interested in acquiring first class students. Then, the corporation expects to be given a “preferential" choice in obtaining the best students. This method of operation is utilized because the supply of well trained and qualified students is less than the demand. This system is particularly effective as, generally, all the |