Manufacturing & Prototyping

Improvements in Manufacturing BMI/Fiber Composites Using AFP

A program now in progress is dedicated to making improvements in automated fiber placement (AFP) for the manufacture of advanced composite-material (matrix/fiber) structural components — especially skin and shell components for aircraft. [In AFP, a composite-material part is formed by laying down fiber tow or tape pre-impregnated with a matrix resin (“prepreg”) onto a mandrel that defines the shape of the part.] Improvements are sought for the following reasons:

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Patterning of Polycrystalline Bi2Te3 Thin Films on Silicon

Experiments in patterning of thin films of polycrystalline bismuth telluride (Bi2Te3) on silicon substrates have been performed. Bi2Te3 is representative of a family of thermoelectric materials that are well suited for use in extracting electric energy from thermal gradients associated with flows of waste heat at temperatures in the approximate range of 0 to 150°C. Techniques and processes for fabricating macroscopic thermoelectric devices from bulk thermoelectric materials are mature and well known, but the same cannot yet be said concerning the fabrication of microscopic thermoelectric devices. The experiments reported here were performed as part of a continuing effort to develop capabilities for fabrication (including mass production) of microscopic thermoelectric devices, with a view toward eventually enabling the incorporation of them as integral parts of micro-electromechanical systems (MEMS) that could also include heat exchangers, sensors, actuators, and/or flow channels. Thus, the development of microscopic thermoelectric devices could benefit from the established industrial infrastructure for manufacturing MEMS and other silicon-based microsystems.

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Progress Toward Carbon-Nanotube Arrays for Probing Cells

Progress has been reported in research oriented toward the goal of fabricating arrays of interconnected single-walled carbon nanotubes (SWNTs) that could serve as probes for measuring localized events within living cells. As used here, "interconnected" signifies mechanically and electrically connected to patterned metal films (interconnections) that lead to contact pads, which, in turn, enable electrical connection to external electronic instrumentation. This research poses a high economic risk because it entails pushing several technological disciplines beyond their present limits. There is no previously reported combination of fabrication techniques and processes for producing carbon nanotubes that have the required properties at the required positions and orientations on patterned metal films.

Posted in: Briefs, Manufacturing & Prototyping, Architecture, Sensors and actuators, Biological sciences, Fabrication, Metals, Nanomaterials
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Inexpensive Free-Form Fabrication of Titanium-Alloy Parts

A continuing effort to devise relatively inexpensive means of manufacturing titanium-alloy parts has been focused on a free-form fabrication approach. As used here, “free-form fabrication” refers generally to any or all of a number of methods and processes denoted, variously, as rapid prototyping or three-dimensional (3D) printing.

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Advances in Fabrication of Nanoscale Devices

Some advances have recently been made on several fronts in a continuing effort to develop of means of fabricating electronic and magnetic devices having dimensions of the order of tens to hundreds of nanometers. This effort is a collaboration of members, from three universities, whose interests, expertise, and facilities span synthesis of materials, nanoscale characterization, nanoscale lithography, and non-lithographic processing of nanostructures.

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Experiments in Vacuum Brazing of Titanium

An experimental study of vacuum brazing of titanium and of the effects of changes in brazing alloys and brazing process conditions has been performed. [As used here, “titanium” signifies both commercially pure titanium and an alloy nominally consisting of 90 weight percent of titanium, 6 weight percent of aluminum, and 4 weight percent of vanadium (commonly abbreviated “Ti-6Al-V”).] The knowledge gained in this study is intended to contribute to development of capabilities for fabricating titanium structures in circumstances in which welding — heretofore the typical method of joining titanium — cannot be performed because access is limited or adjacent nonmetallic components would be harmed. There is a particular need for such knowledge to enable fabrication of lightweight, durable titanium- based structures for armored vehicles. Examples of such structures include standard lightweight plate structures, titanium components encapsulating ceramics, and panels that comprise pyramidal frame cores sandwiched between face sheets.

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Small-Scale Combustion-Chamber Testing Facility

A small-scale combustion-chamber testing facility has been designed and partly built for use in evaluating advanced combustor designs for future gas turbine engines. The specific model combustor for which the facility was designed is an approximation of a planar section of an ultra-compact combustor (UCC). In the full-scale UCC (Figure 1), vanes in an annular cavity are positioned and oriented to cause the combustion gases to flow in a spiral pattern and the resulting centripetal acceleration in the cavity is utilized to increase the speed of combustion and thereby make it possible to design the combustion chamber to be shorter than would otherwise be necessary. In the model combustor, the spiral aspect of the flow is approximated by means of a small flow of air directed perpendicular to a main flow. The design of the facility and the model combustor provides access for off-axis optical (including visual) observation and measurement of cavity-vane interactions. The facility can also be used to test many other combustor models.

Posted in: Briefs, Manufacturing & Prototyping, Combustion chambers, Test facilities
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Fabrication of Lightweight Armored Doors for HMMWVs

A document describes a concept for fabricating lightweight armored doors for the Army’s high-mobility multipurpose wheeled vehicles (HMMWVs). Essentially, the concept is to reinforce high-hard (HH) steel armored doors used on some HMMWVs with a laminated, woven, high-tensile-strength glassfiber/ polyester-matrix composite that has performed well as armor material in previous military applications. A fabrication procedure for implementing the concept, described in the document, can be summarized as follows:

Posted in: Briefs, Manufacturing & Prototyping, Doors, Fabrication, Composite materials, Glass fibers, Steel, Military vehicles and equipment
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Rapid Model Fabrication for Responsive Aerodynamic Experimental Research

Technicians machine traditional metal wind tunnel models in a process that can span months. Although these models are highly precise, the meticulously slow manufacturing process precludes a quick assessment regarding a new design's feasibility and thus impedes the ever-increasing need to help today's warfighter address constantly changing warfare threats. In support of the Integrated Rapid Aerodynamics Assessment program, AFRL has been exploring the impact of rapid prototyping (RP) technology in meeting this escalating need. According to AFRL's Mr. Gary Dale, an originator of this experimental research effort, "We were looking for a way to quickly generate experimental data that we could use to verify computational fluid dynamics (CFD) results. The CFD researchers were generating solutions in a matter of days or even hours, and they wanted to verify their solutions with [wind tunnel] experimental data." By producing a model in days—or possibly hours, depending upon model complexity—RP technology enables this concurrent study of air vehicle concepts via computer simulation and wind tunnel results.

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