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This Defense Intelligence Reference Document, DIA-08-0912-008, is dated 12 January 2010. It was prepared by the Defense Warning Office's Acquisition Support Division at the Defense Intelligence Agency as one of a series of FY 2009 technology reports under the Advanced Aerospace Weapon System Applications program. It reviews materials for launch vehicles, space vehicles and reusable rocket engines, including aluminum alloys, polymer and metal matrix composites, titanium and nickel alloys, and titanium aluminides. It concludes that newer materials and integrated design could improve on the space shuttle.
From the source:Release of 2026-09-18 Incident: 1/12/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD surveys the structural materials needed for advanced aerospace platforms and argues that material choice cannot be separated from overall vehicle design, because launch vehicles, space vehicles, reusable systems, and propulsion hardware each face different temperature, durability, weight, and manufacturing constraints. The report reviews a range of candidate material classes, including advanced aluminum alloys; polymer-, aluminum-, and titanium-matrix composites; titanium alloys; nickel-base alloys; refractory metals; ceramic-matrix composites; carbon-carbon composites; and titanium aluminides. It emphasizes that balancing performance against practical limits such as fabrication methods, cost, inspection, contamination control, and service environment remains a major challenge. Its overall conclusion is that many promising materials exist, but their usefulness depends on application-specific tradeoffs and on closer integration of material selection with design and manufacturing, with some systems judged to be more valuable targets for development than others.
UNCLASSIFIED/ /POil Offl@IAL l:ISli 8PtLY will eventually fracture at their weakest points, which, statistically, is often somewhere in the matrix rather that at the mouth of the crack . These fractured fibers then must be pulled out of the matrix during crack extension under continued loading, an action that dissipates add itional energy . Therefore, the total energy expended during fracture of a CMC is much greater than it would be in the case of a monolithic specimen of the ceramic matrix. The crack bridging and pullout mechanisms of toughening, with the attendant increase in energy dissipation during fracture, are the conceptual foundation for CMCs. In SiC fiber-reinforced SiC matrix (called SiC-SiC) CMCs, the toughness can be as high as 10 times that of the unreinforced matrix. Clearly, the nature of the fiber matrix interface determines the resistance to fiber pullout after fracture and controls the toughness. In high-temperature CMCs, the fibers are coated to achieve an intermediate fiber-matrix interfacial bond strength that optimizes pullout toughening. If the interface is too weak, the fibers pull out too easily. If it is too strong, the fibers break without any pullout. Neither of these situations maximizes the toughness. Therefore, the challenge in creating a tough CMC is not only creating this interface but also finding a coating that will remain stable over time during exposure to elevated temperatures. As service temperature increases, this latter requirement becomes more challenging. For extended service, SiC-SiC CMCs currently are limited to about 1,400 °Celsius, but this is higher than the capability of metallic materials. The matrix microcrack stress is also significant because once the matrix develops microcracks, it allows the environment to gain access to the fiber-matrix interfaces. The role of environment can be to alter the nature of the interface and reduce the extent of pullout toughening. The obvious difficulty with this is that the properties are better initially than after a period of exposure in service. This leads to a nonconservative design that is dangerous. Absent an arbitrary knockdown, there currently exists no means of estimating the reduced toughness as a function of service life. Nevertheless, CMCs are the material class that holds the greatest promise of defeating the temperature limits of current metals. An important issue at present is the limited industrial base for producing CMCs and the even more restrictive range of su itable ceramic fibers available for use as the reinforcement in CMCs. The cost of CMCs is currently very high but should come down with increased demand, as happened with TMCs. Even so, CMCs will always be expensive, making development of efficient designs that make optimal use of this class of material important. Carbon-Carbon Composites Carbon-carbon composites (C-CCs) consist of carbon fibers in a typically amorphous carbon matrix. In principle, this class of materials is very attractive because it has very low density and high strength at elevated temperatures. C-CCs also have good oxidation resistance at very high temperatures (1,200 °Celsius) because they use an Si-rich coating that forms a stable, protective Si02 film on the surface. This coating system is "self healing" if breached because, among other things, it is glassy (viscous) and reforms over cracks. The principal vulnerability occurs at intermediate temperatures where the viscosity of the glass is high enough that it may not flow rapidly enough to heal a breach, exposing the reactive C substrate to the damaging oxidizing environment. As with CMCs, there also are some questions concerning long term changes in the fiber-matrix interfaces that are at least partially responsible for the loss of impact toughness over time, as experienced in the Columbia accident. 19 UNCLASSIFIED//FOA OFFICl.t.k Uilii Qptla¥
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Official release, from the pursue collection. The PDF is mirrored here; the original link is above. 27 pages are in the text index: search them above, or from the library's search.