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SESSION m: DRIVERS FOR MATERIALS DEVELOPMENT SESSION OBJECTIVES Determine the drivers for development and application of advanced fire-resistant materials. PARTICIPANTS Chair: Dennis Nollen, DuPont Committee: lames Peterson, Boeing Commercial Airplane Group Bruce DeBona, AlliedSignal Participants: Fred Arnold, Federal Aviation Administration Donald Cardis, Schneller, Inc George Danker, Akro Fireguard Products Thor Eklund, Federal Aviation Administration Michael O'Donnell, Imi-Tech Swen Schaich, Deutsche Aerospace Airbus Martin Spencer, Heath Tecna Marte} Zeldin, City University of New York Staten Island SESSION REPORT Current F'r+Res~stant Materials Just as different materials have varying weight, cost, processability, and availability, they also have varying fire resistance. For example, highly fire-resistant materials include poly- benzimidazoles, polyquinoxalines, polyphosphazines, polyimides, phenolics, polyether- ketonekelones, polyetheretherkelones, ceramics, and mews. Materials that have been modified to meet current regulations include epoxies, polyesters (e.g., Trevira@), and polyurethanes (with carbon). Aircraft interiors are today made of materials of varying fire resistance, depending on application and materials availability. Typical applications and current materials usage are summarized in the following table. However, many of the available highly fire-resistant materials find limited application in aircraft interiors because of the requirements for aircraft interiors such as weight, cost, manufacturability, and end-use suitability. 233
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234 Improved Fire- and Smoke-Resistant Materials Applications Materials Floor and floor covering Glass or carbon/epoxy or phenolic/Nomex~ honeycomb floor panels - flexible urethane seat track covers - urethane foam edge band Mylar0 film over galley and entry floor panels Wool or nylon carpet - double-backed tapes to attach carpet to floor - Nomex. felt underlay (at customer request) Polyvinylchloride galley mats Lower sidewall panel Glass or carbon/phenolic/Nomex~ honeycomb plus scuff-resistant surface (wool or Named fabric, or tough plastic) Upper sidewall panel Glass or carbon/phenolic/decorative thermoplastic layer plus Tedlar~ Light covers Polycarbonate Overhead stowage bins Glass or carbon/phenolic/Nomex~ honeycomb plus edge urethane foam layer plus reinforcement Gap fillers Silicone or urethane Passenger seats Wool, wool/nylon, or leather upholstery Urethane foam cushions Polybenzimidazole or Nomex@/Kevlar~ blocking layer Polyethylene form flotation foam Thermoplastic seat trays Cabin attendant seats Wool, wool/nylon, or leather upholstery Urethane foam cushions Polybenzimidazole or Nomex@~/Kevlar~ blocking layer Polyethylene foam flotation foam Partitions Glass or carbon/phenolic/Nomex~ honeycomb Decorative thermoplastic laminate or wool/Nomex~ textile or leather Polycarbonate transparent wind screen (infrequent) Stowage bins Glass or carbon/phenolic/Nomex~ honeycomb Decorative thermoplastic laminate Wool textile interior liner (infrequent) Placards Polyvinylchloride or urethane Insulation Fiberglass bats, phenolic binder, Mylar cover Polyvinylchloride/nitrile rubber, polyethylene, foams Polyimide foam Windows Outer pane stretched acrylic Idner pane cast acrylic Dust cover polycarbonate or acrylic
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Part 11- Workshop Seminary TABLE (continued) 235 Applications Materials Passenger service units Hoses Air ducting Molded thermoplastics (Ultem@, Radel@, PEKK) Aluminum Glass or carbon/phenolic Silicone Nylon Urethane Glass/phenolic, epoxy, or polyester for large ducts Polyisocyanurate foam for large ducts Fire-retarded nylon Glass/silicone Nomex0 felt (small quantity) Polyimide foam wrap For non-aircraft applications, materials are generally used according to the requirements of the application. For marry commercial applications, such as buildings, the fire resistance requirements are not very stringent, so the materials used have less fire resistance than those used in aircraft applications. In specially high-cost and vulnerable items such as manned space vehicles and submarine applications where fire is an extreme hazard, materials that are more fire resistant are used. Design and Performance Requirements for Interior Materials Design and performance requirements were not addressed in this session. The participants fell that the conference papers on this subject by Hanns-Ioerg Betz, Swen Scha~ch, and Hans- Dieter Berg were complete treatments of these topics. Goals for fire Performance of Future Materials Performance goals for improved materials for future applications were suggested by participants. Commercialization of any new material for aircraft interiors requires, in addition to flammability characteristics, economic viability, consistent manufacturing base, pleasing aesthetics, cleanability, and low smoke and toxic product emission. No Flashover. Full-scale tests conducted by the Federal Aviation Administration showed that after flashover, escape from a post-crash fuel-fed fire was no longer possible. Thus a critical step in improving survivability is to preclude flashover. Uniform Requirements. Standardizing flammability requirements for all interior parts would make materials selection simpler and would reduce the testing and development costs.
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236 Improved Fire- arm Smoke-Resistant Materials However, this would probably limit the availability of materials for the less critical applications, since all materials would have to conform with the most stringent requirements. Improved Burnthrough Resistance. Glass- and carbon-reinforced sandwich panels already have adequate burnthrough resistance. Other materials could be substituted if their burnthrough resistance was upgraded. Retention of Mechar~ical/Physical Properties. Retention of physical and mechanical properties of interior furnishings is important in maintaining the physical integrity of the fuselage, which is crucial for passenger escape. Totally Nonburrmble Materials. if totally nonburnable materials were developed that were also appropriate for aircraft use, fire safety would be upgraded to the highest possible level. Enclosed Air Circulation Systems. If materials could be adapted to enclose air circulation systems and implemented within acceptable design constraints, fire containment could be improved. State of the Materials and Fabrication Industries Although there is still adequate research capability within the materials and fabrication industries, there has been a substantial curtailment of research capability over the past few years with the downsizing of aerospace materials research. This is in part due to a downturn in the defense industry activities and in part due to a downturn in the commercial aviation business. For the materials industry to be able to respond effectively to the challenge of new materials development in a unilateral way, there must be a clear signal that the effort will be supported at government levels on a long-term and sustainable basis. Without this, there is a serious question whether companies would be willing to commit their resources to such research. The fabrication industry in turn will have to wall until materials are available before it can learn how to fabricate parts from such materials. Drivers and Barriers for the Development of Improved Materials Session participants identified drivers for, and barriers to, the development and implementation of new materials in commercial aircraft interiors. These are enumerated in the following sections.
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Part II - Workshop Summary Drivers . . Barriers 237 . . · The U.S. Congress recognized the need to pursue air travel fire safety by directing the Federal Aviation Administration to establish research and development in this area. Materials suppliers and researchers are driven by the potential for a return on investment. If materials with higher fire safety are developed, the developer will expect to obtain return on investment. Regulations provide a legal mandate that must be satisfied. If a material being used causes a part to be noncompliant with new rules, changes must be made. Also, the potential of anticipated future regulation would cause material manufacturers to consider working on new materials in anticipation of a potential future profit. Differences in regulations among worldwide regulatory agencies tend to drive the implementation of materials and structures that are compliant with the most stringent requirements, since the use of multiple materials for a common application is costly. There has been a substantial effort to develop common regulatory requirements across national boundaries (e.g., Federal Aviation Administration/lAR, etc.~. Life-cycle costs have been getting more attention recently. The effort to reduce the cost of ownership for the airlines is a significant factor in the implementation of new technologies. Life-cycle costs can be affected by material costs, fabrication costs, or maintenance requirements. Materials with good in-se~vice experience tend to see increased usage. Materials with poor in-service experience or with histories of failures tend to be replaced in subsequent design cycles. Aircraft manufacturers have applied new materials unilaterally for many years to provide product improvement or lower costs. Technologies that provide product/process simplification while satisfying other in-use requirements will have priority. Weight reduction is a significant driver in aircraft design. Implementation of a material that satisfies other in-use requirements at lower weight is favored. Developments that have been funded with government or aircraft industry research money are more likely to be implemented. If a manufacturer spends research money to develop a material, there is a strong motivation to receive a return on the investment. · Both competition and partnerships work to foster further development. Several barriers result from the way that the aircraft manufacturers do business. Since cabin designs are upgraded with the introduction of each new aircraft model, there are multiple designs for functionally similar parts with divided manufacturers resisting technologies that were Not invented here."
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238 Improved Fire- aM Smoke-Resistant Materials . Because of the aircraft industry's stringent engineering requirements, certification procedures, expensive quality control, and part configuration control, changes to existing designs are very difficult and costly. The cyclic business environment of aircraft manufacturers causes serious problems in materials manufacturers' ability to sustain long-term efforts in materials development. The nature and size of the market cause problems with the material suppliers. Manufacturer's price is high, because niche materials sold at low volume are expensive. It is very difficult to achieve implementation of a new, higher-cost alternative without tangible, quantifiable benefits. Without alternative uses for new developments to increase utilization, justifying development of new materials for the limited market will be difficult. Aircraft manufacturers are implementing shorter order-to-delivery time, decreasing the time available to implement new materials in a production cycle. The high cost of qualification and certification of a new material for aircraft applications makes embarking on a material development and implementation program risky for both the materials supplier and the aircraft manufacturer. Downsized industry research organizations will have more difficulty performing the work necessary to develop and commercialize new materials. Government research programs can present barriers. Inadequate cooperation or teaming among government, industry, and academic organizations inhibit the interdisciplinary exchanges required for substantial progress on fire-resistant materials. Undertunded government research initiatives inhibit the initiation of long-term research projects. Issues concerning intellectual property rights are barriers to joint programs between government, industry, and academia. It is crucial that there be suitable test procedures and acceptance criteria that have inter- and intralaboratory repeatability and reproducibility. Participants said that the poor reproducibility of current regulatory test procedures have caused, and are still causing, extreme problems. Long-Term Research . Make long-term research a priority. Establish acceptance criteria. · Establish goals and requirements. Establish repeatable and reproducible test equipment and procedures.
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Part 11 - Workshop Summary 239 Establish joint development programs between government, academia, and industry. Encourage development through prioritized government grants and contracts to industry and academia. Establish a forum for exchange of ideas and results. Explore alternative design concepts. Explore simplified configuration control possibilities for aircraft manufacturers. Explore cooperative ventures between the Federal Aviation Administration and other government agencies. To make investment in fire-resistant materials more attractive, expand markets by finding alternative uses for advanced materials, advanced materials concepts, and advanced materials systems. Explore promising technologies to improve existing materials, and to develop new materials, modified materials, and hybrid approaches. Suggested activities include new approaches to construction principles, testing, analytical modeling, and processing.
Representative terms from entire chapter: