P. Materials, Processes, and Structures
The Armys Materials, Processes, and Structures Program (MP&S) provides enabling technologies that are used to construct every physical system or device that the Army uses. The MP&S program provides Army-unique technology solutions and options that will increase the level of performance and durability, and reduce the maintenance burden and life cycle costs of all Army systems.
The materials subarea focuses on providing materials with the superior properties required for use in structural, optical, armor, and armament, chemical/biological/laser protection, biomedical, and Army infrastructure applications. All classes of materials are included: metals, ceramics, polymers, composites of all types, coatings, energetic, semi- and super-conductor, and electromagnetic functional materials. Meeting the performance needs of future Army systems will require synthesis of new materials, modification of existing materials, design of property specific microstructures and composite architectures, and development of advanced characterization techniques to specify microstructure, properties, and degradation modes.
The efforts in materials processing include those technologies by which raw or precursor materials are transformed into useful materials and/or components with the requisite properties and reliability and at an acceptable cost for Army utilization. Included in the processing subarea are such technologies as casting, rolling, forging, sintering of metal or ceramic powders, polymerization, filament winding, composite processing and curing, machining, and chemical vapor deposition. Lower substrate temperature coating processes are being developed including ion beam assisted deposition (IBAD) (see Figure IV-P-1), pulsed laser deposition (PLD), and other surface modification technologies. Process modeling and control will improve quality and reduce costs of future Army materiel. Under the new paradigm of "intelligent processing," quantitative process models, artificial intelligence/expert systems, embedded sensors, and feedback/feedforward control systems are coupled so that processes can be adjusted in real time. Closely allied to "intelligent processing" are on-line nondestructive testing and inspection technology, which enhance quality and durability assurance.
Figure IV-P-1. Environmentally Compatible Ion Beam Assisted Deposition (IBAD) Coatings for Wear
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The structures subarea is aimed at demonstrating generic structures based on advanced materials and processes that meet Army specific needs such as structural elements for armored vehicle and helicopters, guns and ammunition, and missile/smart projectiles. Particular emphasis is on the development and modification of design tools and modeling for failure, fatigue, and life prediction analysis.
All Army hardware critically depends upon MP&S for its performance, affordability, and durability. To the maximum extent possible, the Army relies on improvement of existing MP&S capabilities in industry, academia, and the other Services. However, the many unique Army requirements, such as thick-section ballistically efficient composite structures for combat vehicles, combat helicopter structures, chemical/biological protective materials, low-cost durable laser eye protection, transparent armor, and armaments, do not have commercial markets that support an adequate private sector R&D infrastructure. Further, there is no commercial analogue that superimposes both the severe environments and necessity of sustained high-stress use to which materials are subjected on the modern battlefield. Thus, a robust in-house MP&S technology generation program is essential to sustain the Armys current and especially its future warfighting edge. A soldier responsive in-house R&D center of excellence with a critical mass of dedicated experts is essential to focus and manage the creation, transfer, and transition of both external and internal MP&S technology advances to address Army specific requirements.
3. Technology Subareas
Goals and Time Frames
New materials with greatly improved properties and durability are being developed that enable major capability improvements for Army systems. For example, entirely new polymer matrix composite materials concepts that are being developed for reducing armor weight by 35 to 45 percent will also dramatically improve ballistic performance and reduce overall systems costs. This weight reduction development will have a significant impact on increasing air deployment capability. Further opportunities arise from the multifunctional capabilities of such composite material systems whereby structural, ballistic, and signature reduction improvements can be simultaneously incorporated into one material system. Ballistically efficient composites have been transitioned into the Composite Armored Vehicle-Advanced Technology Demonstration Program (CAV-ATD) during FY96.
Advanced Ceramics are under development for missile guidance domes and windows. These materials provide transparency in the required wave frequencies as well as high temperature performance and rain erosion resistance. A unique nanoscale Silicon-Nitrogen-Oxygen, Si-N-O, ceramic alloy for radome applications will be developed by FY98. Also, transparent spinel ceramics for window applications will be demonstrated by FY97. In addition, process/property optimization for recently developed high performance Barium Strontium Titanate ferroelectric materials are being refined as thick films that will enable size, weight, and cost reduction for a new generation of microwave phased array radars. This technology will transition to CECOM in FY98.
Recent advances in converting highly ordered polymers into textile fibers with outstanding strength-to-weight ratios will lead to lighter weight body armor, helmets, and shelters without reducing ballistic protection (see Section IV-F). Computer-aided design of the molecular structure of polymers will be utilized to develop improved transparent armor and controlled permeability barrier materials for protection against chemical and biological agents by FY98¹. Higher performance heavy alloys for penetrators and warheads are essential to defeat advanced armor systems. Advanced powder metallurgical processed two-phase tungsten alloys are being developed that may provide an alternative for depleted uranium penetrators. The goal is a full-sized tungsten penetrator with equal performance to depleted uranium by FY00. Issues related to the development of advanced warhead materials are discussed in Section I, Conventional Weapons.
Improved ceramic thermal barrier coatings, wear resistant coatings, and monolithic and reinforced ceramics composites for rotorcraft and ground vehicle propulsion (see Sections IV-C and IV-S) will be demonstrated in the FY98-02 time frame. Wear resistant coatings and advanced composite materials with tailored combinations of mechanical and physical properties for reducing weight and improving durability of both conventional armaments and electric guns will be demonstrated by FY98 (see Section I).
Major Technical Challenges
While the field of materials science and engineering has made dramatic advances to materials performance by understanding the underlying role of microstructure in obtaining desired performance characteristics, many formidable scientific and technological problems still exist. Of particular importance to the Army is the ability to relate the state-of-the-art knowledge base of composition-microstructure-property parameters to models that predict behavior of materials in such complex phenomena as ballistic penetration, long term environmental exposure, and chemical agent permeation.
Specific technical challenges:
- Develop and validate models to predict the static and dynamic behavior of fiber/matrix interphases for improved synthesis and performance of polymer and/or inorganic matrix composite structural materials.
- Develop and validate predictive models for the environmental durability of monolithic and composite materials.
- Develop and validate models for the interactions of gases, vapors, and liquids with polymeric barrier materials.
- Develop cost-efficient lightweight transparent armors for personnel and sensor protection.
- Design tungsten or other heavy metal alloys/microstructures that will provide equal ballistic performance as depleted uranium.
- Develop high strength steels that combine high strength, toughness, and ballistic properties. These steels should be weldable and resistant to stress corrosion cracking.
- Model and mitigate the micromechanical failure mechanisms in elastomeric materials for Tank Track application.
- Develop improved materials for protection from agile laser threats for the individual soldier and direct view optics. Also, improved nonlinear optical materials for sensor protection devices.
- Reduce wear and erosion in armament launching components.
Goals and Time Frames
The MP&S program thrusts in processing science and technology focus on those processes that are required to implement the incorporation of advanced materials in Army systems. R&D on the intelligent processing of thick sections, resin transfer molded (RTM) structural composite armor materials (embedded sensors) will lead to both increased quality and reduced costs (see Figure IV-P-2). Improved process control methodologies including neural net feedback/feedforward capabilities will be demonstrated in the FY97-98 time frame, and will transition to the CAV-ATD and follow-on programs. Integration of the SMART weave process into manufacturing systems is covered in Section T, Manufacturing Science and Technology. Processing thrusts to develop low cost Ti-alloys for lightweight armor and weapons systems such as howitzers with enhanced air mobility will be demonstrated by FY98. Tape casting of multilayer Barium Strontium Titanate materials for low cost microwave phase shifters at 35 GHz will be demonstrated in FY98.
Figure IV-P-2. Smart Weave, a technique for cure monitoring of resin matrix composites during processing, is an example of intelligent processing.
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Major Technical Challenges
Much progress has been made in the area of modeling single processes and process steps. However, the integration of real-time, non-contact, or on-line sensing (especially at the very high temperatures required in liquid metal and ceramic processing) with adaptive control technology for the vast array of materials processes used by the Army is a formidable challenge.
- Develop and validate knowledge-based models for consolidation synthesis, post-consolidation thermal or thermomechanical processing, and improved capability for joining or repair of polymers, ceramics, metals, and organic and inorganic matrix composites.
- Develop process-specific sensors and control systems.
- Develop new materials processing and/or surface modification to achieve near or actual net shape components of complex geometry and variable composition and microstructural combinations to yield significantly improved tribological or structural performance in more affordable materials/design systems.
Goals and Time Frames
The structures portion of the MP&S technology area focuses on developing structures with a high level of structural integrity that are inspectable, analyzable, and survivable in the harsh combat environment. To be cost-effective the structural design must integrate advanced structural design concepts that are compatible with mass production manufacturing technologies. These structures can be either man rated or unmanned air or ground vehicles and hence must be designed to specific vibration and noise levels to maintain crew comfort and a low noise signature.
The results of these technological efforts have led to improved methodologies to detect and predict the onset and growth of internal damage in composite structures. This results in lighter weight and more durable structure. In the advanced concepts area unidirectional rod packs used as axial stiffening members are being evaluated (see Figure IV-P-3). Application of the rod packs reduces fiber waviness, which is detrimental to compression response. Through the integration of the rod packs in compression loaded structures, significant improvements in compression stiffness and strength have been achieved. The application of smart materials to control sound transmission through a structure has been demonstrated on fuselage like shell structures fabricated from composite materials. Reducing interior noise levels greatly improves crew comfort and reduces occupant fatigue levels.
Figure IV-P-3. Unidirectional Rod Packs Used as Axial Stiffening Members
Major Technical Challenges
- Design structurally efficient, cost-effective, and durable composite structures for Army unique ground and air vehicles as well as other structural applications.
- Develop fracture mechanics methodologies and stress analyses suited to meet Army structural needs.
- Develop NDE techniques for identification and quantification of defects and anomalies in composite structures.
4. Roadmap of Technology Objectives
The roadmap of technology objectives for Materials, Processes, and Structures is shown in Table IV-P-1, below.
Table IV-P-1. Technical Objectives for Materials, Processes, and Structures
¹ Recent developments in polymer science, specifically dendritic polymers, are being investigated for Army applications as polymer resin and composite materials, adhesives and coatings, and electrically conducting polymers