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Supplement: Summary of Committee Study
Section I Program Assessment In its review of advanced organic composite technology the committee considered (a) their potential advantages, (b) inhibiting factors or barriers to their application, (c) technical issues that need to be resolved to help accelerate their application, and (d) possible actions the government could take (through the National Aeronautics and Space Administration [NASA], U.S. Department of Defense [DOD], and Federal Aviation Administration [FAA]). The committee's views on these matters are summarized in this Supplement (which addresses aircraft manufacturers and airlines, composite material manufac- turers, and government agencies) based on the committee's review of the material presented to it and its own deliberations. AIRCRAFT APPLICATIONS The committee used four classes of aircraftâlarge transports (and airlines as users), rotorcraft, high-performance aircraft, and general aviationâfor its assess- ments of potential advantages, inhibiting factors, technology needs, and possible government actions. Following is a summary of these assessments. Potential Advantages Advanced organic composites can, if the technology is fully developed, provide appreciable advantages for all classes of new, advanced aircraft. Some of the more important advantages are listed in Table S-I-1. These range from reduced costs for design, manufacturing, and operation of the aircraft to aerodynamic and structural tailoring to improved crashworthiness and life. The importance of each varies with class of aircraft. The subjects of reduced structural weight, increased aircraft productivity, and reduced costs are fundamental drivers of research and technology for all classes of 10
20 TABLE S-I-1 Potential Advantages Assessment Large High- Transports Performance General Subject & Airlines Rotorcraft Aircraft Aviation Reduced structural weight 1 1 1 1 Increased aircraft produc- 1 1 1 I tivity Reduced costs: design, de- velopment, manufacturing, and operations 1 1 1 1 Aerodynamic and structural tailoring 2 1 1 2 Increased stiffness and reduced fatigue 2 1 1 2 Improved performance 2 1 1 2 Reduced corrosion, main- tenance, and repair 2 1 1 : Improved crashworthiness 2 1 2 2 Damage reduction 2 2 2 2 Long life 2 2 2 2 KEY: IâVery important 2--Important 3âSignificant aircraft. With advanced organic composites, primary structural weight reductions of 20 to 25 percent are probable and up to 50 percent potentially possible, compared to a metal structure. This can be translated into various combinations of longer range, reduced fuel consumption, or larger payloads. Reductions in cost for design, development, and manufacturing will help broaden the market for individual aircraft and improve their competitive position. Reduced operational and life-cycle costs are possible because of the potential for reduced initial and operational costs through the integration of design and manufacturing, the manufacture and assembly of fewer parts, the automation of manufacturing, the reduction of labor requirements, and the increase in productivity per unit of cost. Composites produce smooth, finished surfaces and permit variable contours to maximize aerodynamic efficiency. They can be designed precisely to net-shape with fiber orientation to give the desired stiffness and achieve maximum structural ef- ficiency. Structural efficiency is enhanced further by the reduced susceptibility to
21 fatigue of composite structures. These factors combine to improve aircraft perfor- mance, and they synergistically interact with other factors that increase operational efficiency and, thus, productivity. The matters of tailoring stiffness, reducing fatigue, and lowering structural weight are relatively more important for rotorcraft because of their severe oper- ating environment and higher weight empty fraction. Because composites are stiffer than metals, do not corrode, and experience less fatigue, they should require less repair and maintenance than metal structures. This basic stiffness advantage is important to all of the aircraft classes. For rotorcraft, additional potential advantages are reduced vibration and cyclic loads. For high- performance aircraft a significant potential advantage is greater capability to sustain repeated high-stress maneuvering. Although a conventional composite structure has relatively poor crashworthiness due to its lack of inherent plasticity and residual strength following yield, current Army and FA A research indicates that, when properly designed to enhance crash- worthiness, a composite structure can have a higher specific energy absorption than a metal structure. This represents a fertile area for additional research if the full benefit of composite structures is to be realized. The potential for improved crash- worthiness, at a reduced weight penalty, is important for both civil and military rotorcraft. Inhibiting Factors Use of advanced organic composites has been limited because of the inhibiting factors listed in Table S-I-2. Thus, the potential advantages addressed above have not been fully exercised. Among the major inhibiting factors for all aircraft classes are the high costs of design, development (including certification), and production of advanced organic composite structures. Design and development costs are pervasive. They involve such matters as (a) the lack of technology data bases from design to test to certifica- tion to manufacturing, (b) limited understanding of failure mechanisms and related analytical methods for predicting and designing to avoid failure, (c) the inability to certificate (acceptance for military aircraft) with assurance, (d) low tolerance to ac- cidental, natural, and battle damage, (e) the need for nondestructive inspection and testing techniques, (f) difficulty in making repairs in the field, and (g) the low-stress limits of present advanced organic composite materials. Certification deserves special comment. It is a cost item because of the time and complexity of a process that in the end has not had high success. This has resulted in an understandable reluctance on the part of designers and manufacturers to apply composites aggressively, particularly in civil aircraft. Technical uncertain- ties associated with design and development, and the certification process itself, are inhibitors. The certification agencies (FAA and DOD) also have difficulties in identifying appropriate tests and processes for validating safety, performance, and life characteristics and in assessing test data. The difficulties experienced by the
22 TABLE S-I-2 Inhibiting Factors Assessment Subject Large Transports & Airlines Rotorcraft High- Performance Aircraft General Aviation High costsâdesign, de- velopment, and production 1 1 1 I Lack of technological data base 1 1 1 1 Understanding failure mechanisms 1 1 1 1 Low tolerance to damage 1 1 1 1 Inadequate nondestructive testing 1 1 1 1 Certification difficulty 1 1 1 1 Difficulty of damage repair in field 1 1 1 2 Lack of design experience/ education 2 2 2 1 Costly maintenance and repair 2 2 2 2 High acoustic response 2 3 3 2 Limited manufacturing capability 2 2 3 2 Inconsistent manufacturing quality 2 2 2 3 Low-stress limits 2 1 1 3 Brittleness of matrices 3 2 1 3 Adverse effects of environ- ment 3 3 3 3 Material cost 2 3 3 2 Ability to design thick-wall components 3 1 2 3 Erosion of rotor blades 3 1 3 3 Low tolerance for high temperature 3 3 1 3 KEY: l--Very important 2--Important 3--Significant
23 certification agencies are exacerbated by the lack of standardized definitions and test procedures for composites. The inability to make a full commitment to composites is in part due to the lack of advanced production techniques, procedures, and automation. The inability to handle design, development, and production factors expeditiously raises costs and reduces product quality and performance. This, in turn, will adversely affect the scope and rate of technology development. Production (i.e., manufacturing) is inhibited by limited capability and capacity, high tooling costs, and inconsistent quality. The ratings for these factors range from important to significant depending on the class of aircraft (Table S-I-2). Factors such as low-stress limits, brittleness of matrices, and environment (Table S-I-2) affect all aircraft classes and vary in importance with class. The ability to design (and test) thick-walled components is very important to rotorcraft. Such components are used extensively in rotors and major structures, and are expected to find their way into drive trains. Also important in rotorcraft design is avoidance of rotor-blade erosion by sand and dust, rain and hail. A unique concern for high- speed, high-performance aircraft is the low structural tolerance of advanced organic composites to high temperatures. Costly repair and maintenance and lack of design experience and education are considered universally important inhibitors. For general aviation, experience and education are very important and of special concern because these manufacturers have limited production facilities and staffs, and find it difficult to compete with the large firms for trained personnel. Comments specifically pertinent to airline operations are contained in Appendix B, special correspondence from the Air Transport Association of America. Technology Needs To gain the potential advantages of composites, the inhibiting factors must be reduced or removed. The needs, among a broad spectrum considered most significant, are noted in Table S-I-3. They include reduced costs, concepts and design innovation, and data bases, among other items. Costs There is no question that costs must be reduced. Much of the costs are asso- ciated with manufacturing (tooling, processes, and labor), some with development testing and certification, some with materials (which will become a larger factor with expanded use of composites in a given design), and some with design. New Concepts and Design Innovation The full benefits of composites will not be realized until designs (and manufacturing processes) take advantage of the unique characteristics of composites and composite structures are not designed and built like metal structures. This requires new design and manufacturing concepts; it requires innovation.
24 TABLE S-I-3 Needs Subject Assessment Large High- Transports Performance General & Airlines Rotorcraft Aircraft Aviation Reduce costs 1 1 1 1 New concepts and design innovation 1 1 1 1 Technical data bases 1 1 1 1 Failure mode analysis/under- standing 1 1 1 l Design and manufacturing integration 1 1 1 1 Simplify and accelerate certification/acceptance 1 1 1 1 Education and training 2 2 2 1 Easy repair and field re- pairability 2 2 2 2 Advanced composites program 2 1 3 3 High-temperature, long-life processable systems 3 3 1 3 Honeycomb and sandwich systems 3 3 3 3 KEY: l--Very important 2âImportant 3--Significant Data Bases The large manufacturers are building data bases for design, testing, and certification. These data bases are not universal nor are they available to other manufacturers. The proliferation of new basic materials and composites, and designs and processes make the maintenance of data bases complex and expensive. Some semblance of order and standardization is required if the time, complexity, and cost of design and testing are to be reduced and certification is to be approached with confidence. Failure Mode Analysis and Understanding If designs are to be sound and certifiable, failure and its progression and an understanding of how to design to avoid failure under severe operating conditions must be predictable. Analytical toolsâtheoretical and/or empiricalâthat provide this capability are needed to assist in design and testing for safe, long-life composite structures. Design and Manufacturing Integration To capitalize fully on composites, innovation
25 in design must be integrated with innovation in manufacturing. The very process- ing of composites affects the characteristics of the material and the finished part. The activities are interdependent not independent. Automated manufacturing will reduce production costs and improve quality control. Simplify and Accelerate Certification There are two parties to certificationâindustry and government, i.e., the producer and the certificator/acceptor. The producer needs to know what to design for and how to design and test for certification. The certification agent needs to specify requirements and procedures that will satisfy guardianship of the public interest. Data bases on related matters will help. There is a need for a high level of confidence in the ability to certify a new composite aircraft design including the realization of reduced certification process time and cost. Particular attention to simplification and acceleration of the process is needed and warranted. Education and Training Most people involved in composites today were not trained in this specialty field. Expanded development and application of composites will require an enlargement of the cadre of professionals and technicians in the field. The problem is specialized training in this relatively new field. Needed is cooperative effort among industry, government, and universities on both near- and long-term educational matters. Advanced Composites Program An advanced composite rotorcraft program that ad- dresses generic technology development (noted in the discussion on inhibiting factors pertinent to rotorcraft) would significantly improve these aircraft. The technology development effort must include validation of the generic technology at reasonable system scales and give attention to new, innovative rotorcraft concepts. Related work for transport and the other classes of aircraft, with a focus on generic primary structures (fuselages and wings), is considered by the committee to be an impor- tant, integral part of the technology development effort for helping U.S. aircraft manufacturers maintain a competitive edge in world markets. Ease of Repair and Field Repairability Important to all aircraft classes is ease of repair at the maintenance base and in the field from time, cost, and tooling considerations. Owners and operators need techniques and tools that allow simple and inexpensive repairs in the field. This is especially important for military and airline operations. Service disruption results in loss of mission or revenue. High-Temperature, Long-Life Systems Composite systems that can tolerate high temperatures, have long life, and are readily processed into components and struc- tural elements are critical to the development of future high-speed and high-perfor- mance military aircraft. These aircraft will operate at high-supersonic (in the future possibly at hypersonic) speeds for extended periods of time. Organic composite ma- terials and structural designs are needed that can withstand temperatures to about
26 550°F. But, of course, much higher temperatures must also be dealt with for exterior structures and propulsion system elements. Honeycomb and Sandwich Systems Although there has been a movement away from honeycomb and sandwich composite structures due to poor past performance un- der conditions of high humidity and widely varying temperatures, they warrant re-examination because these systems are efficient and relatively inexpensive. Hon- eycomb and sandwich systems can be very important to general aviation and have significant value for the other aircraft classes. Possible Government Action Table S-I-4 lists some of the more important actions that government agencies could take, related to aircraft design, manufacturing, and testing, to help further the application of advanced organic composites. The government agencies can: (a) build technology confidence, (b) continue support of basic research, (c) support, se- lectively, the development of data bases, (d) support development of new structural concepts and innovative structural designs including manufacturing processes, and where appropriate, large-scale (including flight) integrated system concept testing for technology development, (e) develop fatigue and failure mechanism analyses, (f) identify and pursue activity to reduce the time, cost, and uncertainties of cer- tification of composite aircraft structures, (g) support development of advanced manufacturing techniques and processes, and (h) support fellowships and other ed- ucational endeavors to help improve the cadre of professional and support people in the field of composite aircraft structure design, development, manufacture, testing, and operation. Other subjects warranting government support, because they are important or of significant value, involve the exploration of the potential for application of new and innovative composite structures, the development of technology pertinent to damage-tolerant design, and the definition and development of an advanced com- posite aircraft technology program encompassing large-scale validation of analyses and small-scale experiments. MATERIAL MANUFACTURERS Table S-I-5 summarizes the observations of the committee with regard to three classes of materials having special interest to aircraft designers and manufactur- ers: (1) epoxy resin pre-impregnated fiber (prepreg), (2) bismaleimides/polyimides (BMI/PI) for higher-temperature applications, and (3) thermoplastics for manufac- turing advantages. Potential Advantages Epoxy resin prepreg has the advantages of lower-cost manufacturing, existing
27 TABLE S-I-4 Possible Government Action Assessment Subject Large Transports & Airlines Rotorcraft High- Performance Aircraft General Aviation Build technical confidence 1 1 1 1 Support technical data-base development 1 1 1 1 Support basic research 1 1 1 1 Support new concept and in- novation design and man- ufacturing 1 1 1 1 Develop fatigue and fail- ure mechanism analyses 1 1 1 1 Reduce time and costâ cer- tification/acceptance 1 1 1 1 Support fellowships 1 1 1 1 Explore potential appli- cations 1 2 2 2 Develop advanced composite (flight) aircraft technology program 2 2 2 3 Address manufacturing cost reduction 2 2 2 2 Develop technology for thermoplastics manufac- ture 2 2 1 3 Develop damage tolerant design technology 3 1 3 3 KEY: IâVery important 2âImportant 3âSignificant data bases (within a few companies), experience, and available facilities. However, there is significant room for technical advancement in each area. BMI/PI composites can withstand the moderately high temperatures (up to about 550°F) associated with moderate supersonic flight speeds. Like epoxy, to some degree, the kinds of tools needed for manufacturing are in-hand, but data bases and experience are less and costs are higher than for epoxy. Thermoplastics have high potential. They can handle higher temperatures than the other organic composites noted and possess higher toughness. There is also a potential for lower-cost, uniform manufacturing.
28 TABLE S-I-5 Summary ObservationsâMaterials Possible Government Actions Potential Advantages Inhibiting Factors Needs EPOXV Lower costs Existing data base Experience Existing facilities Moisture damage Low toughness and ease of damage Supportability Bismaleimides/pol vim ides High High cost temperature Thermoplastics Greater reproducibility Ease of repair Higher temperature Higher toughness High cost Availability Need for high temperature and pressure for processing Raise toughness and temperature Improve processing Improve manufacturing methods Increase data base Develop measurement and evaluation techniques and processes Develop measurement and evaluation techniques and processes Develop measurement and evaluation techniques and processes Inhibiting Factors Epoxy systems are subject to strength reduction, i.e., environmental damage, due to moisture ingestion if detailed attention is not given to design. The materials have low toughness and are relatively easily damaged. This can lead to problems con- cerning damage detection, knowledge of the extent of damage and failure potential, and when and how to repair. BMI/PI materials are relatively expensive. They are inherently brittle and possess low toughness. These factors lead to the same class of supportability issues that epoxies have. Thermoplastics have had relatively little application in aircraft. Their costs are high, they are relatively unavailable, and they require high pressure and temperature for forming components.
20 Needs Epoxy's major drivers, from material considerations, are increased toughness and higher usable temperatures than are available today. However, considerable progress in toughness has been achieved since 1985. For BMI/PI, one of the more important needs is to improve the ability to process these materials with consistency and low cost. Possible Government Action In the area of materials the committee believes that the government can be of most help through attention to the development of standards of measurement, evaluation techniques, and basic material production processes. Although industry can develop materials, it is not in the best, most unbiased, position to develop and set standards for the measurement and evaluation of materials. It is the view of the committee that the detailed development of new materials, manufacturing processes, and applications can be left essentially to the materials industry in concert with the aircraft designers and manufacturers. However, in the area of basic understanding of chemical and mechanical processes, government research and technology devel- opment support would be very useful in accelerating fundamental understanding, leading to industrial development and application. GOVERNMENT AGENCIES The views of government representatives on important technology development needs are summarized in Table S-I-6. The technology development needs noted for the Army relate to rotorcraft; the Navy and Air Force needs relate principally to high-performance aircraft; the FAA to transport, general aviation, and rotory-wing aircraft; and NASA to generic research and technology. Observations common to all aircraft classes are summarized in Table S-I-7. The data in Tables S-I-6 and S-I-7 reinforce the earlier industry discussions of needs, potential advantages, inhibiting factors, and needs. Potential Advantages The government agencies see common advantages and benefits associated with advancing the state of technology of advanced organic composites. These bene- fits relate to broader design, operational, and mission flexibility and thus greater performance and/or productivity. They see the potential for reducing the costs of composite structures through enhanced technology, advanced designs, and greater application of composites. The committee agrees with the government agency rep- resentatives' belief that successful pursuit of these advantages will help maintain U.S. competitiveness and preserve U.S. jobs in aircraft development and produc- tion programs. Thermoplastics have interesting potentials but there is relatively little experience with applications. Application would be enhanced with improved
30 TABLE S-I-6 Individual Government Agency Views on Advanced Organic Composite Technology Development Needs U.S. Army Composites for rotor blades that withstand rain and sand Design criteria and standards for damage, durability, and fatigue Design for damage tolerance, durability, and crashworthiness Methods (standards) for handling fatigue in a uniform and consistent manner Realistic qualification procedures U.S. Navv New materials and material forms to meet more severe design conditions, i.e., woven composites and new resin systems Systems for better impact and damage resistance, survivability, low cost, supportability, crashworthiness, fatigue life, durability, and maintainability including analytical tools Postbuckling analysis methodology Certification procedure definition Low-weight design Issue areas: airframes and structural integrity, landing gears, load and life management, supportability, and electromagnetic compatibility U.S. Air Force Research and development: thermo- setsânew polymer concepts and resin characterization, processing science, ordered polymer fiber and film, molecular composites, opto-electronic materials Supportability: field repair materials, postfailure analysis, paint removal, and thermoplastic support Manufacturing technology and science: regarding computer-aided cure of complex shapes, integrated composites center, large composite aircraft Thermoplastic and organic materials for propulsion systems Federal Aviation Administration Detection of understrength bonds (all classes) Failure analysis methodology Standards for material property testing Cost-effective finite element analysis techniques for complex-load transfer areas Flammability, toxicity, and smoke characteristics of materials Damage growth analysis Repeated-load response Statistical analyses to allow reduction of mechanical testing Full-scale component response versus coupon response and data scatter Crashworthiness Lightning-strike behavior National Aeronautics and Space Administration Systems characterization: mechanical properties, damage tolerance, micromechanics/failure, and environmental effects Structural concepts, efficiency, and tailoring Gradients, discontinuities, cutouts, and damage Postbuckling and nonlinear effects and analyses Local and global structural analyses including failure mechanisms and analyses Subscale wing-box and fuselage-shell modeling Filament-wound structures Thermoplastics
31 TABLE S-I-7 Summary of Government Agency Views on Advanced Organic Composite Technology Development Factors Potential Advantages Inhibiting Factors Needs and Possible Government Action Reduced structural weight and increased stiffness Aerostructural tailoring Design flexibility Increased aircraft performance and/or productivity Fatigue resistance No corrosion Longer life Reduced part count and manufacturing costs Reduced life-cycle costs Competitive edge and jobs Costs; design, devel- opment, manufacture, certification, and maintenance and repair Data base for design and test Manufacturing techniques and capability Limited experience and trained personnel Impact damage susceptibility, i.e., low damage tolerance and understanding failure mechanisms Nondestructive and non- invasive test and inspection methods Ability to certificate Cost reduction; design, manufac- ture, test, and certification Data bases for design and test Design and manufacture innovation New concepts for structural design and manufacture Design and manufacture integration Certification; simplify and accelerate Build technology confidence Large-scale systems; advanced composites airframe program Thermoplastics; increase attention Education; professional and technical support manufacturing technology and enlargement of design and development data bases. Particular attention needs to be given to the development of low-cost manufacturing processes. Inhibiting Factors Government agency representatives view inhibiting factors as relating to high costs; limited design, development, and testing data bases; integration of design and manufacturing; certification; and the lack of appropriately trained engineering personnel and technicians. These are the same factors considered important by the designers and manufacturers, and by the committee.
32 Needs and Possible Government Action It is the view of the committee that the government can play a significant role in gaining the advanced organic composite benefits that have been identified in this study through the reduction or elimination, selectively, of inhibiting factors. The government could help reduce costs by supporting technology developments that improve design, manufacturing, testing, certification, and maintenance pro- cesses; including support of related definition, development, and sustenance of data bases. Other key factors in cost reduction and leadership are new concepts and inno- vation; pertinent is work related to structural design, manufacturing, certification, and maintenance processes. Certification is difficult under normal circumstances, and with composite designs even more so. The government could review the entire certification process, includ- ing assessment of technology development needs, and pursue adjustments to the process that can result in less time-consuming, less costly certification of composite structures. In all of this work it is important to build confidence in the technology and processes for handling composites from design to certification. This will require detailed attention to technology development including large-scale work to validate small-scale experimental data and analyses. Thermosets have received the most attention in past programs. Thermoplastics, on the other hand, have interesting attributes, such as reproducibility, manufac- turing simplicity, and high toughness and temperature capability, which may well outweigh their higher manufacturing costs. These materials should be included in the program. Education programs supported by special grants should be developed to train engineers (and technicians) in the application and use of composites. A summary of key technology program considerations for all aircraft classes that should be factored into this planning from a review of government agency consid- erations is presented in Table S-I-8. The committee did not attempt to identify a top-level technology development program plan. This level of planning should, of course, respond to policy and programmatic objectives set by responsible manage- ment. The committee believes that the government's program policy, objectives, and plan should be developed, in concert, within the responsible government agencies (NASA, DOD, and FAA). This will be a complex undertaking. It is recognized that the development of an advanced organic composite material technology program is indeed complex because of the generic as well as the unique considerations associated with aircraft classes and their users. Regarding materials, the agencies agree that the basic (generic) technology should be pursued. They believe, and the committee concurs, that the govern- ment should direct attention to basic R&T and standards for assessing and testing, and that industry should pursue product development. The value of pursuing mate- rial technology development includes cost reduction (though not assessed as a major life-cycle, cost-controlling factor), greater reproducibility, ease of repair, and greater
TABLE S-I-8 Government Agency SummaryâTechnology Program Considerations, All Aircraft Classes Technology Development Effects of discontinuities; cutouts, gradients, and damage Modeling and full scale; wing boxes and fuselage shells Airframe structural integrity, landing gears, and electromagnetics Aerostructural tailoring Filament-wound structures Methods for controlling fatigue and standards for design System response to repeated loads System characteristics; mechanics, damage tolerance, failure modes, environmental effects, and energy attenuation Supportability; maintenance and repair in depot and field Testing; bond strength, standards, techniques, and instruments Lightning-strike protection without weight penalties Components and Systems. Analytical Tools Complex load transfers; finite element techniques Local and global systems including failure mechanisms Postbuckling and nonlinear effects Failures and damage growth Materials and Processing Characterization; flammability, toxicity, and smoke Improved erosion characteristics Thermoset research and technology development Thermoplastic research and technology development Materials and material forms for severe design conditions Manufacturing technology; reproducibility, automation, and effects on products Data bases Nondestructive testing Design Concepts and Innovation Low cost and weight Criteria and standards; fatigue, damage, and durability Damage tolerance and durability Survivability, crashworthiness, and fatigue life Structural concepts; efficiency and tailoring Maintainability and repairability Certification Capability Definition of processes and procedures Full scale versus coupon response and scatter Statistical analysis to reduce testing and costs Standardized processes and definitions
34 toughness (reduced damage susceptibility and failure response). Inhibiting factors today are high material and processing costs, low levels of toughness, high degrees of response-to-damage, rate-of-failure progression, and the inability to operate at high temperatures. SUMMARY OF KEY OBSERVATIONS In summary the committee notes the following about the development and ap- plication of advanced organic composites: ⢠AdvantagesâThe potentials for weight reduction, increased performance, and/or mission flexibility, ease of manufacturing and assembly, and reduced life- cycle cost. ⢠DriversâIncreased performance, mission flexibility, new capability, and for- eign competition. ⢠DrawbacksâIf technology development is not pursued, there are high costs, susceptibility to damage, and limited serviceability and supportability. ⢠ProblemsâDamage tolerance: design capability (analysis, data bases) related to failure mechanisms, bonds, joints, and other elements; repair; nondestructive eval- uation; environmental effects; high-temperature capability; low-cost manufacturing; and certification. ⢠Unresolvable issuesâNo real unresolvable issues, but need management cul- tural changes, more experience, and facilities. ⢠Government roleâTechnology development, new concepts (innovation) for design and manufacturing, test and evaluation processes, standards, data-bank de- velopment and support, education, and improved certification processes to build confidence in design and application. With regard to materials the committee be- lieves that the government should help develop materials system characteristics, standards, processes, and techniques for measurement and evaluation of materials, and leave focus on materials and material system development to the materials industry. The committee's key observations are the following: ⢠Despite successful application of organic composites to aircraft, their full potential is largely unused. ⢠Foreign competition (with government support) has been more aggressive in applying advanced technology and will continue to be aggressive. ⢠The driver for composites has been performance. The new emphasis must be on reduced costsâinitial, operations, and support. Affordable aircraft is a must for both civil and military systems. ⢠Innovation and data-base development and documentation are other points for program emphasis. ⢠New programs must be directed at significant increases in technology: new ways to design, test, build, and maintain low-cost, high-strain, integrated-structure
35 aircraft. Selective generic component and system test work is required. Funding for such work falls short in all government programs. ⢠The military does provide substantive support to R&T programs for highly loaded, high-performance aircraft, but this does not relieve the needs noted. ⢠Future use of composites depends upon the level of confidence that designers, project managers, and corporate management have in the available technology. ⢠A bold new program will have to be defined and brought to the attention of NASA and other involved government agency managements, the administration, and the Congress. Part of this program development task will be to make clear the inseparable roles of government and industry. ⢠Program planning needs to involve the government agencies, industry, and the universities. The definition, support, and conduct of critical, large, expensive test programs should also involve these groups, in the form of joint ventures. Thus, the committee takes the position that the full potential of composites for aircraft are far from realized, and, (1) the government's program must be directed to the future and be appropri- ately visionary; (2) it is incumbent on the government (NASA, DOD, and FAA) to provide the nation, through industry, with the capacity to capitalize on composite material potential; and (3) a bold new technology development program is needed. It is the view of the committee that these actions will provide the nation with the technology that will allow the design, development, and certification of cost-effective composite aircraft with high levels of confidence.
Section II Response to Government Issues and Questions The role of government in aeronautical technology development, particularly that of the National Aeronautics and Space Administration (NASA), has been brought into question due to budget constraints. This has had an adverse im- pact on NASA's support for advanced composite structures work, especially re- lated to civil aviation. For example, NASA's fiscal year (FY) 1986 budget for research and technology (R&T) development was under $4 million. The Federal Aviation Administration's (FAA) budget was also quite low, less than $1 million for safety/certification-related composite structures R&T. Because of its constrained budget for advanced organic composite structures, NASA raised a series of questions related to a future NASA R&T program: (1) Can a new program help resolve industry needs? (2) Is a long-term major national effort appropriate? If appropriate, (3) What is the government's role? (4) Where can the government best apply resources? (5) What specific program guidance and priorities are appropriate? and (6) What are the key barriers to the consideration of composites as routine structural material? FUTURE R&T PROGRAM New Program The committee believes that the current R&T program in government is not deep enough or broad enough to provide the data required for sound design and development of advanced organic composite aircraft with reasonable industrial risk. A new R&T program is indicated if, as a matter of national policy, the United States wants to maintain a leadership role and a competitive advantage over other nations in aircraft design, manufacturing, and sales.
37 Major National Effort The committee believes that a major national effort is warranted in view of the complexity, high risk, large investment, and high-potential national payoff of an effective, successful R&T program. A mitigating factor in favor of a national, not a private, effort is the little likelihood of industry mounting and sustaining an appropriate program and appropriately disseminating the program data. Government's Role In the view of the committee, the government's role is to orchestrate the defini- tion and implementation of an appropriate R&T program with inputs from industry and the universities. It is anticipated that significant elements of the program will be carried out in-house and under contract and that some parts of the program will be joint government, industry, and university activity. This joint activity would be characterized by large, significant effort having a large payoff in next-generation designs. Application of Government Resources The application of government resources and the identification of program pri- orities were not addressed by the committee. The committee believes that program funding and priority judgments need to be made in the context of specific future development program possibilities and agency budgets and priorities, and these judgments can best be made by the agencies themselves with industrial guidance and university participation. Key Barriers Barriers to the application of advanced organic composites have been discussed in detail in Section I of this Supplement. In simple summary, the lack of data bases and experience combine to affect adversely the time, cost, and certainty of design, development, and certification of advanced organic composite aircraft and form the key barriers to accelerated use of these composites. PROGRAMMATIC MATTERS Costs Costs are possibly the most significant barrier to more rapid growth of compos- ites. The representative but rough estimate of costs noted in Table S-II-1 are for transport and fighter class aircraft. Manufacturing dominates structural costs. The committee believes that suc- cessful investment in manufacturing-processes R&T could significantly reduce total system cost.
38 TABLE S-II-1 Representative Costs of Composite Structures for Transport and Fighter Aircraft Costs (percent) Cost Segment Transports Fighters Manufacture 55-50 70-65 Material 30-35 10-15 Quality assurance 15 20 and test At least three manufacturing techniques hold some promise for cost savings over current techniques. These are filament winding, pultrusion, and three-dimensional weaving or other weaving/braiding techniques. Some technology development has been directed to these areas. However, the committee believes that greater invest- ments are required to determine the merits of these and other possible processes and forms of composite materials to enlarge this important activity. Structures A government advanced organic composites program plan should be formulated to provide a new effort in primary structures directed to design and development activity during 1990-2010. This should entail development of systems and manufac- turing technologies including innovative structural concepts that exploit advanced composites, particularly for wings and fuselages. An aggressive goal would be for new designs to have a 50 percent primary structure weight savings with a 50 percent savings in cost. The advanced primary structure design concepts would provide greater stiffness, strength, damage tolerance, and system life. Products of this work would include an understanding of design requirements and constraints. The innovative structural concepts work would include tailoring for best use of materials (i.e., do not follow the practices for metal structures). An integral part of the effort would involve textile technology, including three-dimensional braiding, fiber placement, and curing processes. This kind of primary structures work will require analyses and design-verification testing using component and system subscale models and selectively large-scale, in- cluding full-scale, models. The work would also require the development of analytical tools and models and the building of appropriate structural design and manufac- turing data bases. Included should be computer-aided design and manufacturing compatibility. These technology tools will assist in identifying and resolving critical structural issues from design to development to certification and operation.
39 Advanced manufacturing technology should use intelligent machines and tool- ing, i.e., robotics with built-in (artificial) intelligence to increase productivity, con- sistency, and quality. Industry must develop new kinds of factories. The materials that would be employed would include thermoplastics and advanced thermosets. To be most useful to industry, this work must be accompanied by the selective building of appropriate data bases. To exploit innovative, low-cost manufacturing methods there must be parallel development of analytical tools that predict the structural behavior of components made by the new methods. These analytical tools can form the basis for future design and manufacturing procedures. Government laboratories should, through in-house, contract, and grant activity, help develop these analytical tools; and through coop- erative efforts with airframe manufacturers, fabricators, and universities, produce and test representative components to verify analyses. This effort should focus on the development of cost-effective composite struc- tures through the definition of efficient structural arrangements that can be rapidly produced by automated material placement techniques. The government can accel- erate this activity by soliciting and sponsoring research to identify new structural shapes, elements, and components that are amenable to low-cost manufacture. In preparation for such work it would be desirable to have system analyses that provide trade-off assessments of manufacturing cost against vehicle performance. Technology FIGURE S-II-1 conceptually presents the structuring of an integrated technology data base for the design, test, and manufacture of composite aircraft. As noted, the term "material properties" involves such matters as the mechanical, thermal, chemical, and electrical properties of the composite materials under consideration. Needed is the definition of the standard (generic) tests that characterize the basic properties of the materials. This includes the identification of the test type and methods for the measurement of such factors as tensile and compressive strength, shear fatigue, fracture, and thermal and chemical responses to environmental and loading conditions. This is not a simple matter. It is complicated by, among other things, test conditions and specimen geometry. To be able to compare types of materials, it will, in all probability, be necessary to test various composite systems (thermosets, thermoplastics, and bismaleimides or polyimides) for the same application. The structural elements noted in Figure S-II-1 include such matters as joints; three-dimensional forms; curved, bolted, and bonded structures; and cutouts, holes, and notches. Important to the designer is life prediction of elements, components, and systems involving knowledge of such characteristics as damage susceptibility, fatigue, compression, combined loads, buckling, and environment response. The life prediction work must be based on analysis and tests. Related documentation must be developed in a timely manner and in a form useful to designers at large. The areas of substructure and fabrication include such elements as frames,
40 MATERIAL PROPERTIES Mechanlcal Thermal Chemlcal Electrlcal Etc. STRUCTURAL ELEMENTS Jolnts 3-0 element* Curve* Bonds Cutouts Etc. FIGURE S-II-1 Data-base development concept. trusses, panels, and shells, and such activities as lay up and filament winding. The government should help define representative tests and perform tests on representa- tive substructures and fabrication techniques. It should assist in the development of life-prediction analyses and tests. These and other data would be used to provide the integrated data bases vital to sound design, manufacture, test certification, and other matters critical to the development of effective composite aircraft. The type of data-base documentation needed has to be developed. Here and for the other parts of the data-base activity an issue is: Who will develop, update, and maintain these data bases? Innovation The objective of technology development for innovative design and manufac- ture of aircraft structures is to build the data base to allow designers to produce components and secondary and primary structures that could cost one-half or less that of current aircraft structures. All types of aircraft are of concern: for the militaryâtrainers, patrol, surveillance, interceptor, and remote-piloted aircraft; and for civilâgeneral aviation, agricultural, and business aircraft, and transports. Approaches to achieving this objective include pursuit of new concepts and techniques for material and structural design and fabrication. Materials of future
41 interest include: thermoplastics, advanced thermosets, chopped fibers, bioadhesives, biomaterials, self-skinning foam, and hybrid systems. Design innovations involve: joints, e.g., Windecker wet tow, resistance welded, bonded; foam-stabilized wings and frameless, stringerless structures, e.g., sandwich skins (supported by various cover-to-cover sine wave, corrugated, or honeycomb structures); modular systems, e.g., multicell wing structures and mission adoptive control surfaces; and design and fabrication procedures for such advanced concepts. Total factory automation is the direction for the future. Fabrication meth- ods R&T should include filament winding and molding techniquesâresin transfer, resin injection, compression (for fuselages), and injection (for wing spars). Inno- vative materials processing should include nonautoclave cure, hot-forming thermo- plastics, welded thermoplastics (e.g., resistance welding and fusion welding), and three-dimensional weaving. GOVERNMENT PROGRAMS The committee does not believe that the government's advanced organic com- posites material and structure program supports the level of activity needed to realize the full potential of these materials. Industry has not and is not expected to support the development and dissemination of the data required to accelerate the application of advanced organic composites by the industry. The aircraft of interest are both civil and military of all classes. With the exception of very-high-performance (supersonic, hypersonic, and transatmospheric) military aircraft, reductions in structural weight and cost of as much as 50 percent axe possible with new or improved mission and performance capabilities. The technology leverage gained will not only provide better, less-expensive aircraft with enhanced or new capability but also provide industry with a competitive edge in world markets. The committee has noted that a new, bold technology development program is needed. The new program would focus on reduction of design, development, production, and support costs. It would support innovative work in the areas of design, test, and manufacture, and assist in rapid, lower-cost certification of resulting advanced aircraft systems. It would focus attention on new uses of materials as well as integrated design and manufacturing to make best use of the properties of composites and void the conservative practice of designs that duplicate metal structures. The new program would address the problem of building data bases and the problems of selective collection, documentation, and dissemination of data to assist design, test, and certification work. Current programs do not address the spectrum of work envisioned in this bold new program. Funding has been and is expected to continue to be a problem. It is suggested that the concept of joint government, agency-to-agency, and industry- to-government (including universities) programs be undertaken, especially for large- scale experimental work, to help mitigate cost problems. The institutional means appear to be in place to address the matters of program definition, approval, implementation, and management including reporting and data
42 dissemination. It is the committee's view that it would be appropriate for NASA to take the initiative in the development of the bold new program with strong participation from the U.S. Department of Defense and FAA, and with the active involvement of industry and universities.
