3

Research Priorities

Chapter 2 highlights DOD’s need for various types of functionality or combinations thereof for systems. In this chapter, those system needs are examined to determine priorities for materials and processes research areas. The committee also points out crosscutting issues any material must address. These research priorities will provide a basis for the technical panels for the next phase of the study.

SYSTEM MOTIVATION FOR MATERIALS AND PROCESS NEEDS

R&D in materials and processes will be needed in a number of general areas. A combination of breakthroughs in long-established materials and new materials or materials combinations will probably be necessary to address system needs. Examples of the types of materials needed are shown in Box 3-1 and are described below.

Types of Materials

Lightweight Materials with Retained or Enhanced Functionality

A pervasive requirement for DOD systems is weight reduction in everything from tanks to the equipment carried by individual soldiers. At the same time, military forces will require at least the same functionality as today’s force—for example, the ability to withstand enemy fire. New functionalities will also be required, particularly in sensing surroundings, communicating with and responding to other elements of the force, increasing lethality, and responding to new threats.



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3 Research Priorities Chapter 2 highlights DOD’s need for various types of functionality or combinations thereof for systems. In this chapter, those system needs are examined to determine priorities for materials and processes research areas. The committee also points out crosscutting issues any material must address. These research priorities will provide a basis for the technical panels for the next phase of the study. SYSTEM MOTIVATION FOR MATERIALS AND PROCESS NEEDS R&D in materials and processes will be needed in a number of general areas. A combination of breakthroughs in long-established materials and new materials or materials combinations will probably be necessary to address system needs. Examples of the types of materials needed are shown in Box 3-1 and are described below. Types of Materials Lightweight Materials with Retained or Enhanced Functionality A pervasive requirement for DOD systems is weight reduction in everything from tanks to the equipment carried by individual soldiers. At the same time, military forces will require at least the same functionality as today’s force—for example, the ability to withstand enemy fire. New functionalities will also be required, particularly in sensing surroundings, communicating with and responding to other elements of the force, increasing lethality, and responding to new threats.

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BOX 3-1 Material Types for Defense After Next lightweight materials that retain their functionality materials that enhance protection/survivability stealth materials electronic/photonic materials for high-speed communications sensor materials high-energy-density materials materials for improved propulsion technologies Materials for Enhanced Protection/Survivability The ability of DOD forces to withstand enemy fire will continue to be critical. Considerable research could be done on new approaches to providing this capability, particularly at reduced weight. Hybrid materials that perform multiple functions are likely to be a promising area of research. Stealth Materials As the range of operations increases, it will be increasingly important for some elements to remain invisible for as long as possible by means of stealth technologies. This presents an important area of research in several directions, ranging from multifunctional structural materials that incorporate a stealth capability to electronic and/or optical materials and devices that may actively respond to probes to achieve invisibility. Electronic and Photonic Materials for High-Speed Communications New levels of communication and coordination of elements in a force will require extremely high bandwidth, secure transmission, reception, and interpretation. These in turn will require materials that will enable these functions,

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be they optical, electronic, or some combination thereof. In addition, the force elements that must be coordinated will be under constraints for weight, speed, or both—meaning that the desired functionality must be achieved in very small volume and probably also with as little weight as possible. Sensor Materials A battlefield of interconnected elements poses many demands, one of which is the need to detect signals, which may be of many types (e.g., electromagnetic, molecular, etc.). Research on sensor materials and their integration into larger systems will be important to DOD. An emerging area of sensor needs is for the detection of chemical and/or biological agents. High-Energy-Density Materials The projected increase in operating distance for forces of the future, coupled with the need for environmental consciousness (see below), will require R&D on materials and systems that can increase energy efficiency. Materials for Improved Propulsion Technology Future forces hope to rely eventually on hypersonic propulsion systems. Regardless of the validity of this hope, improved propulsion will be necessary in several arenas, particularly undersea, in air, and in space. Abundant materials issues will have to be addressed, ranging from the need for high-energy-density fuels to high-temperature materials to materials for improved undersea propulsion. Materials Properties In addition to the materials needs discussed above, a number of adjunct materials properties would be desirable for DOD systems. These characteristics cut across the classes of materials already discussed. Although they would not, in and of themselves, lead to the selection of a particular material for a given application, they are likely to play an important role in that selection. Examples of these properties are listed in Box 3-2 and discussed below.

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BOX 3-2 Crosscutting Materials Properties multifunctionality self-healing and/or self-diagnosing materials materials for low total-cost systems low-maintenance materials high-reliability materials environmentally conscious materials and processes Multifunctionality One way to reduce weight and volume is through multifunctionality—materials that can perform at least two functions (e.g., stealth and structural support). Multifunctionality can be thought of on two scales: (1) on a mesoscopic (e.g., coatings) or macroscopic (e.g., load-bearing) scale, and (2) on a microscopic or nanoscopic scale, in which multiple physical phenomena are produced through molecular design and/or architectural textures. The need for multifunctionality is driven by the need to incorporate more functions into a fixed or shrinking volume. The concept of multifunctionality encompasses many classes of materials and applications, ranging from structural materials that may be self-interrogating, self-healing, provide stealth, or protect against enemy fire, to microscopic materials or systems that may do some combination of sensing, moving, thinking, communicating, and acting. Self-Healing and/or Self-Diagnosing Materials These materials could address a number of DOD needs, ranging from improving survivability to minimizing system maintenance. Materials for Low Total-Cost Systems Cost is expected to be a primary criterion for DOD decisions for the foreseeable future. Materials that enable low total-system cost (i.e., including

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procurement, processing, maintenance, etc.) will have a decided advantage, even if the cost of the material itself is high relative to other choices. Low-Maintenance Materials As history demonstrates, systems for Defense After Next are likely to be in use for many decades. Therefore, materials that do not require extensive, active maintenance are clearly preferred. This is especially true for structural materials, which would make it possible to upgrade many components in a large system as technology advances without having to scrap the entire system. An example is the Navy’s critical need for ship structures or coatings that reduce the necessity of paint chipping, an egregious task that adds significantly to the Navy’s manpower requirements, recruiting levels, and retention levels. High-Reliability Materials The consequences of materials failure in many DOD systems can be dire. The need for materials and processes that meet reliability requirements spans all classes of materials. Environmentally Conscious Materials and Processes DOD has become increasingly sensitive to the environmental impact of military activities. The use of environmentally friendly energy sources, the efficient use of power, and so forth are areas where considerable R&D is needed. Environmental concerns extend to other materials as well. Materials and processes for DOD systems should have as little adverse impact on the environment as possible. An area of special concern is the decommissioning and disposal of obsolete systems, including the recycling and/or reuse of as much of an old system as possible. Crosscutting Issues Successful research on the broad classes of materials and process research enumerated above would impact systems for Defense After Next only if a number of crosscutting issues are also are addressed. These issues (see Box 3-3 ) must be considered concurrently with R&D because they are likely to reveal the direction research should take.

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BOX 3-3 Crosscutting Issues design issues materials-by-design materials tailorability materials influence on development and deployment costs availability of a commercial alternative risk management manufacturing issues life-cycle issues Design Issues The successful introduction of a new material into a system requires that the design/selection of the material(s) be integrated with the design of the entire system. In this way the best material for meeting the needs of the system can be selected (or, perhaps even tailored or designed). Conversely, early in the design process, certain modifications can be made to the design to compensate for the shortcomings of a material. Materials-by-Design If system designers and materials and process experts are in communication early enough in the process, it may be possible to design a material to meet the needs of the system, rather than designing the system around available materials. In fact, this is likely to become more common as selected strategic experiments, coupled with validated physical models, are incorporated into computer simulations that enable the “virtual” exploration of composition/structure/processing/properties space as a partial replacement for extensive laboratory experimentation. A move in this direction would also address the need for reducing development time and cost. Comprehensive databases of materials properties, although not glamorous to compile, would greatly facilitate

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the design of materials. In addition, characterizing materials for the desired properties, an essential aspect of materials design, may require the development of new techniques. Tailorability of Materials The properties of a material are seldom ideal for all aspects of a particular application. Materials and process scientists must be aware of the desirability of materials or systems of materials with properties that can be tailored over a range of parameters to be compatible with a variety of system requirements. The concept of treating multiple materials as a system as, for example, in structural composites, has already been shown to increase the tailorability of materials properties substantially. The ability to tailor materials systems in multiple dimensions or at shorter length scales than has previously been possible also promises to open new doors. The degree of tailorability required will vary with the type of material and application. Early communication between materials scientists and systems engineers can help in defining the required or desired variations. Influence of Materials on Development/Deployment Costs The choice of a material can influence development and deployment costs in many ways. First, the cost of raw materials may be an issue, particularly if it is very high. If a material is extremely difficult to process, or if there is a great deal of waste or rejected material, costs can escalate quickly. The development of an entirely new processing technology or qualification procedure is also a cost factor. It is critical that the baseline process, the range of acceptable properties, and other factors governing these costs be understood early on so that the research program can at least be mindful of the issues and perhaps even tailor the research to respond to them. Availability of a Commercial Alternative Buying a commercial material or part will almost always be cheaper than designing, developing, and manufacturing a new one specifically for DOD. In some cases, the quality of a commercial product may even be better as a result of economies of scale and well understood process quality controls. Before DOD invests in the development of a new material or process that would marginally improve performance, the improvement should be shown to have a sufficiently

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high potential payoff to be worth the investment. A crucial aspect of DOD’s investments in the development and acquisition of the best materials in the future will involve choosing between in-house development, collaboration with, or purchase from industry. Risk Management For obvious reasons, DOD is highly risk averse, whenever possible. In the materials and process arena, risk aversion translates to a reluctance to introduce new materials or processes unless the benefits have been clearly demonstrated and the risk has been shown to be acceptably low. Minimizing risk leads to a desire to minimize the number of materials in use and to a desire for identifying materials that would lead to the simplification of a component or system design, which in turn would potentially reduce cost and risk—assuming, of course, that the material meets all of the other risk minimization criteria. Finally, DOD must constantly be on the lookout for “fatal flaws” in a material that could eliminate it from consideration no matter how desirable its other characteristics might be. Manufacturing Issues A new material or process may be very promising in the laboratory and yet be completely inappropriate because it is not manufacturable. Materials and process scientists must ensure that production of the material or component can be scaled to a level appropriate for its end use. Defect density must be acceptably low and the yield high so there is little or no waste or inefficiency in the process. The end product must be able to be inspected and characterized, either through rigorous process-based quality approaches or more standard inspection. Finally, the product must be manufacturable at an acceptable cost. Life-Cycle Issues The performance of a material throughout the life of the component or system is an essential consideration in the selection of a material for a particular application. If a predictive reliability model exists for a material or process, the lifetime expectation for the material under conditions of use could be easily determined. An alternative would be a self-interrogating, self-reporting material or system that indicates when attention is required. Materials incorporated into DOD systems must meet extremely high reliability requirements, which can be ensured in a number of ways, ranging from the selection of materials with important

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properties that persist over a wide range of conditions to rigorous process-based quality that enables one to develop a prediction of material reliability. The components and systems must also be maintainable so that they can function at specification for many years, if necessary. Life-cycle costs, including the cost of maintenance over the life of the system, must be considered in the materials selection. Finally, the end of system life must be considered, including the recycling or reuse of as much of the system as possible and the environmentally conscious disposal of parts that cannot be of further use. CLASSES OF MATERIALS AND PROCESS NEEDS Several materials areas have been shown to have a pervasive need, as well as an opportunity, for major advances by appropriate research. One way to group these research areas would be to divide them into five (a manageable number) groups with sufficient overlap so that all major areas are covered. The committee then spent a good deal of time brainstorming and deliberating over classifications for these five areas: material types (polymeric, metallic, or ceramic), functions (structural or electronic), applications (aerospace, naval, etc.), or a combination. The committee first considered the classification used in the Defense S&T Reliance: Materials and Processes Joint Program Plan (DOD, 1999b). The five materials research areas finally agreed upon by the committee are described below. The five technical panels are: (1) structural and multifunctional materials; (2) energy and power materials; (3) electronic and photonic materials; (4) functional organic and hybrid materials; and (5) bio-derived and bio-inspired materials. Box 3-4 shows how the materials and process areas in the DOD Joint Program Plan relate to these five areas. Structural and Multifunctional Materials Panel A consistent theme in the list of system needs is the requirement for stronger, lighter, and stiffer materials that can meet increasingly stringent weight, mobility, and performance requirements. Other areas of need include higher temperature materials for improved performance. Merging multiple functions into a single material structure (e.g., structural member plus stealth) is another area for investigation.

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BOX 3-4 DOD Materials and Processing Needs and the Five Technical Panels DOD Joint Program Plan Panel Studies Platform structural materials Structural and multifunctional materials Bio-derived and bio-inspired materials Propulsion and power materials Energy and power materials Structural and multifunctional materials Bio-derived and bio-inspired materials Armor/antiarmor Structural and multifunctional materials Energy and power materials Materials for electronic and sensor systems Electronic and photonic materials Functional organic and hybrid materials Bio-derived and bio-inspired materials Laser-hardened materials Energy and power materials Operational support materials/nondestructive evaluation Structural and multifunctional materials Energy and Power Materials Panel Many Defense After Next needs are related to power generation, energy harvesting, energy conversion and storage, and energy delivery and dissipation. A particularly important area of research will be the emerging issues of operations from greater distances, survivability, weight minimization, and environmental consciousness. Electronic and Photonic Materials Panel The emergence of the battlefield as a network of entities each of which is collecting, transmitting, and processing information in real-time will place stringent demands on electronic and/or optical materials that can function securely at the required bandwidth. Sensors will be necessary to collect information to be

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processed and shared. Integrated microsystems that can move, sense, think, and act are also likely to be used in Defense After Next systems on the battlefield, for reconnaissance and/or in unmanned vehicles. Functional Organic and Hybrid Materials Panel The combination of requirements for minimal weight and maximum functionality could potentially be met by this class of materials. Attractive materials would be self-healing and/or self-diagnosing, including lightweight electronic, optical, sensing, and, perhaps, structural materials. Bio-derived and Bio-inspired Materials Panel This rapidly developing area will be of great interest for a variety of Defense After Next needs. These materials frequently offer weight advantages over their inorganic counterparts. If some functionalities, such as environmental responsivity or the capability of self-healing, could be introduced, these materials would be extremely attractive, as sensors, for example, or for dealing with chemical and biological agents. This class of materials is most likely to lead to advances in maintaining the health of soldiers—through wound healing, tissue engineering, drug delivery, and so forth.

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