Documents / Report
This Defense Intelligence Reference Document from the Defense Intelligence Agency, dated 12 January 2010, is one of a series of advanced technology reports produced in FY 2009 under the Advanced Aerospace Weapon System Applications (AAWSA) 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, ceramics and titanium aluminides. It concludes that newer materials and design methods offer many ways to improve structural efficiency and cost compared with the space shuttle.
“metallic”11 pages
UNCLASSIFIED,C,CFOA 0111611 L :,es OIPP M • Once a. case is present, can the structure be repaired (for example, by fusion or friction stir welding}? The Air Force Materials and.Manufacturing Directorate is starting a new project intended to address these questions. The motivation for this program is hypersonic flight vehicles. The results from this U.S. Air Force program should prove highly useful to the design of future reusable 550 vehicles. Earlier uses of Ti alloys at high temperatures included the skin and much of the load- bearing structure of the SR-71 Blackbird. This airplane flew successfully at peak speeds in excess of mach 3.2 for 34 years (1964-1998). While the maximum skin temperatures are not readily available, they were in excess of 300 °Celsius, There were no known issues involving o: case during the SR-71's service. Notably, the primary alloy used for ·the SR-71 was one of the original ~-Ti alloys, B-120 VCA, the composition of which is Ti-13V-11Cr-3AI. The primary reason for choosing this alloy was that it is much easier than any of the u +f3 Ti alloys are to roll into sheet gauges. Today there are newer (3-Ti sheet alloys featuring a better balance of properties that could be used in the same way as B-120 VCA. The most common of these is Ti-15V-3Cr-3Sn-3AI. However, the successful use of B-120 VCA raises the question of whether f3-Ti alloys are more resistant than a.+~ alloys such as Ti-6-4 are to a case formation. The attraction to using Ti alloys, in addition to their structural efficiency, is the extensive industrial base for making the material in a variety of product forms and the extensive knowledge base resulting from the many successful applications of Ti alloys in high-performance products. For example1 the ability to superplastically form Ti alloys such as Ti-6-4 creates the opportunity for design of a structure that functions both as load bearing and as thermal protection. Ti Matrix Composites As Table 1 showed, Ti alloys are not especially attractive for their specific stiffness. One way to overcome this limitation is to reinforce a Ti alloy matrix with SiC fibers. In this case, the fibers are "long" fibers-they have sufficient length for the matrix to transfer the maximum possible fraction of the external load to the fiber. The fibers are essentially monofilaments and must be carefully placed so adjacent fibers do not touch one another. Areas of contact between fibers essentially are incipient cracks that degrade the mechanical strength. As Table 2 shows, TMCs have excellent properties. Table 2. Example of Properties of Ti Matrix Composites Property Property Value (English /Metric Units) Ultimate tensile strenoth 276 ksi / 1902 MPa Youna's modulus 32.8 msi / 226 GPa Strain to fracture 0.95% Density 0.16 lb/in 3 / 4.43 g/cm3 Fiber Volume fraction 0.39 14 UNCLASSIFIEDJ.s'F81l 8PPlelt11L 532 ONLft
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Report, from the dia collection. The PDF is mirrored here; the original link is under it. 27 pages are in the text index: search them above, or from the library's search.