Materials Research Agenda for the Automobile and Aircraft Industries (1993)

The goal of this study was to determine the materials research agenda for the commercial automotive and aircraft industries during the next two decades. These industries have important roles in the U.S. (and the world) economy: they employ over one million workers in direct and allied industries and their combined sales of $156 billion in 1991 made up roughly 3 percent of the gross national product for the United States.

The underlying issue in materials use in these two commercial industries is the interplay, or even competition, between what are generically designated as existing and new materials. The latter often encompasses combinations of one or more metals, polymers, and ceramics. A conclusion of this study is that there are more similarities than differences between the four primary forces driving materials research within the commercial automotive and aircraft industries: manufacturing rates, global competition, societal and regulatory constraints, and execution cycles. Advances in materials can be applied either to improve product performance, quality, and reliability or to permit creative product design to provide new, uncontested competitive space in the marketplace. The common materials needs, and thus the long-term focus, for both industries are for cost-effective, easily manufacturable, lightweight, structurally efficient, strong, environmentally benign, recyclable materials. This report has explored how these somewhat parallel needs could manifest themselves in the identification of a long-range research agenda for the industries over the next two decades.

The committee believes that improved materials and materials processing will play an increasingly important role in improving the competitiveness of the U.S. automotive industry. Further, the possibility of added costs will not necessarily inhibit their introduction. Provided that the performance improvements enabled by the new material are sufficiently significant, the supply of the material is stable, the processing of the material can meet the high manufacturing rates, and a reasonable prospect of widespread use exists, there is likely to be a sufficient reduction in the cost of the advanced material to spur its application.

Some of these materials-selection, and hence development, decisions will be dependent on government regulations. For example, as stated in a recent Office of Transportation Materials report, ''projections of weight reductions necessary to enable automakers to meet upcoming anticipated legislative standards currently range from 30 percent to 35 percent (~1,000 lb.), with a 2,000-lb. vehicle projected as typical'' (OTM, 1993). The exact level of weight reduction required will depend on advances in other technologies, such as powertrain efficiency improvements. In principle, weight reductions of this magnitude could be achieved by materials substitution, redesign of all major subsystems (body, powertrain, and chassis), and secondary weight savings. However, the impact of these substitutions on fabrication and assembly processes, vehicle reliability, and recyclability in practice is quite another matter. In order of increasing cost penalty and weight savings and decreasing recyclability, future candidates for body materials include high-strength steels, aluminum alloys, glass-fiber reinforced polymers, and graphite-fiber reinforced polymers. The final decision on usage will likely be based on how well new materials can be individually or collectively incorporated into new, advanced body-construction techniques. One intriguing possibility is the further development of unimolded body construction using polymer composites. The

technological barriers here relate primarily to the higher cost of processing and the lack of available methods for recycling.

For powertrain components, decreased weight is a primary factor, along with other issues (e.g., increased power density, fuel economy, smoothness, and reduced emissions and noise). These needs will likely lead to the extensive use of cast aluminum and the gradual introduction of magnesium, titanium alloys, metal-matrix composites, ceramics, and intermetallics.

There are material-substitution opportunities for other parts of the automobile as well: the suspension and chassis and the brakes. Here again, as with the body and the engine, the issues and the drivers are the same: reduce weight by employing different materials that are cost-effective and environmentally acceptable. The committee believes these opportunities will be largely achieved in the future through the development of new, innovative processing and manufacturing approaches, using either existing materials or those currently being developed.

For the aircraft industry, while the same dominant materials drivers exist for lightweight, strong, environmentally benign materials, the considerations and the likely response will be quite different. A high sensitivity to cost of materials prevails, tempered by the need to meet high-performance requirements. Also, the materials needs of this industry are characterized by relatively small volumes at high-unit costs when compared with the automotive industry. However, similar barriers to the introduction of new materials exist, whether these are incrementally improved existing materials or those designated as revolutionary materials. Here again, the main opportunities lie in processing and manufacturing, which are estimated to account for more than 60 percent of the cost of a successful aircraft program. The effect of material type, processing, and manufacturing routes on

environmental impact, recyclability, safety, and energy use need to receive increased attention, as does potential "noise pollution."

The opportunity exists for future airframe and engine materials to change from monolithic, metal-base alloys to ceramics, both monolithic and composites, and graphite-epoxy type composites. These changes will be driven by cost, weight, processing, and operating environment considerations. Candidate materials for high-temperature environments include the carbon fiber-reinforced thermoplastics and thermosets, such as the cyanate esters and toughened bismaleimides, for airframe materials and TiAl and ceramic-matrix composites for engine materials. Anisotropic materials will also become increasingly important, as will surface and interface engineering to optimize desired engineered structures by creating uniformly graded materials.

The general materials research recommendations that impact both the automotive and aircraft industries are as follows:

• A systems approach to materials science and engineering should be adopted for enhancing existing materials and developing new materials in a cost-effective, competitive manner. This systems approach should include consideration of the material life cycle of the product and successful paradigms for processing of materials, manufacturing of components, and measuring inservice performance.

• Computer-based modeling is needed to integrate and assess the costs and benefits of the continued use of existing materials versus the introduction of new materials. The critical issues are processing, properties, joining, repair, and recycling.

• For automotive and some aircraft applications, research should focus on the development of a master aluminum alloy for wrought applications, the properties of which could be adjusted through processing rather than by alloying. This would eliminate the need for materials separation before recycling and would greatly foster wrought-to-wrought recycling.

• Cost-effective, lightweight, strong, environmentally benign, easily manufactured, and recyclable materials are required for both industries. These goals can best be met with the materials specified in Tables 3-2 and 3-3 in Chapter 3, such as aluminum, magnesium, polymer composites, metal-matrix composites, intermetallics, and ceramics. For instance, the development of low-cost, reliable processes for manufacturing and recycling composites will be key to their increased use.

It is clear that the more detailed analyses and conclusions are consonant with the broader vision of the Federal Coordinating Council on Science, Engineering, and Technology report quoted in Chapter 1 and further that the results described for materials for the transportation industries in this report have broader applicability to other industrial sectors dependent on advanced structural materials.