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/J1P91l 8PPllli.ltt 1191! 8HL\' material is not suitable for the reasons stated earlier. Clearly, the time required for layup places practical limitations on component size. • In automated tow placement, thin ribbons of a pre-preg are fed off a drum or rolled into a computer numerically controlled machine that places them in the desired position. In principle, this process trades recurring labor cost for up-front capital investment (the tow placement machine) and programming time. If the anticipated volume of identical parts is high enough to amortize the capital investment and, particularly, the programming cost, this can be an attractive means of reducing manufacturing costs. For axisymmetric shapes, such as cylinders, this essentially becomes a winding process and is quite efficient .. An example of a finished composite fuselage barrel section for the Boeing 787 is shown in Figure 2. For more irregular three-dimensional shapes, such as a spar or a strut, placing the tows becomes much more difficult and presents a fundamental limitation. Consequently, PMC structures with complex shapes are still for the most part made using the hand layup process. A variant of automated tow placement is compression, whereby a preform, made by automated tow placement, is forced by a press into a preshaped die. This process allows fabrication of more complex shapes, but the rigidity of the fiber and the extreme anisotropy of the tows can lead to wrinkles, which are not acceptable because of the reductions in properties these cause. '-! I .....M.L.- Figure 2. Specially Modified 747 Transporter Unloading a Boeing. 787 Composite Fuselage Barrel Section • The third main composite fabrication method, resin transfer molding (RTM), begins with a woven fiber mat or preform. The polymeric matrix is injected into this mat to create a fully dense composite. The major benefit of RTM is that it permits use of a three-dimensional weave that minimizes the risk of delamination between plies. Note that, with the other two methods, the material is reinforced in only two dimensions (the plane of the pre-preg or tows). RTM's limitations include the viscosity of the resins used. If the resin is too viscous, injecting it will either distort the fiber architecture of the woven preform or not fully penetrate the preform, 4 UNCLASSIFIED,CJP81i1 arr1&1., L ■ ,Si 0011 Y
Not linked to a story yet.
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.