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Infusing Lightweight Composite Structures

European researchers examine simulation-based solutions for the manufacture of large-scale, liquid-resin-infusion composite substructures. Liquid resin infusion (LRI) is a proven manufacturing technology for both small- and large-scale structures for which, in most cases, experience and limited prototype experimentation is sufficient to get a satisfactory design. However, large-scale aerospace and other vehicle structures require reproducible, high-quality, defect-free parts with excellent mechanical performance. These requirements necessitate precise control and knowledge of the preforming (draping and manufacture of the composite fabric preforms), their assembly, and the resin infusion.

Posted in: Materials, Composites, Aerospace, Defense, Articles, DTB

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Business Jets Bounce Back

The business jet segment suffered badly from an extended economic downturn but is now seeing a new generation of airplanes becoming available, introducing features and technologies that are equal to, and in some cases superior to, jets in airline service. by Richard Gardner The business jet market has a resilience all its own. While defense spending has sharply declined, the commercial sector is over-flowing with multi-thousand order backlogs. But if business jet orders can tail off dramatically and then bounce back so quickly, what accounts for this collective long-term immunity to volatile market demands?

Posted in: Aerospace, Aviation, Defense, Articles, DTB

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Enhancing Mission Readiness with Rugged Portable Instruments

To support warfighters in the field, engineers and technicians install, maintain, troubleshoot, and repair a wide range of mission-critical radar and communication systems. These tasks typically require measurements of cables, antennas, components, signals, and more. Often, this work must be done in non-ideal conditions such as rain or shine, hot or cold, aboard a ship, in an aircraft, or in a vehicle.

Posted in: Aerospace, RF & Microwave Electronics, Antennas, Defense, Articles, DTB

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RF Photonics for Avionics Signal Processing

The maturity of RF photonic components has reached the point where fiber optic links are being system-tested to replace traditional copper coax links on avionic platforms. Many demonstrations of RF photonic links have been made with traditional and non-traditional modulation formats to improve the RF performance of the link. While the advantages of RF photonic links in regard to size and weight are important, the large instantaneous bandwidth of the fiber optic links is a key driver for the use of this technology in the airframe.

Posted in: Fiber Optics, Aerospace, RF & Microwave Electronics, Defense, Articles, DTB

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Continuous Sputter Deposition Coating of Long Monofilaments

Monofilaments with continuous, conformal metal or ceramic coatings could be used to develop new sensing and photonic technologies. Army Research Laboratory, Aberdeen Proving Ground, Maryland A thin, uniform coating on long segments of monofilament could drastically improve the functionality of many complex fibers. A length of fishing line, microtubing, or polylactic acid (PLA) coated with copper could be left to cure within an epoxy, and upon removal of the monofilament, a narrow channel with a thin outer wall of copper would remain. That channel would be open for fluid flow, and also have a conductive shell. The “vascularized” material could be used for thermal management or self-healing composites.

Posted in: Materials, Coatings & Adhesives, Aerospace, Defense, Briefs

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Hydrolytic Stability of Polyurethane-Coated Fabrics Used for Collapsible Fuel Storage Containers

Coated fabric tanks are used to store fuel and water in the field. Army Research Laboratory, Aberdeen Proving Ground, Maryland Collapsible fabric fuel tanks have provided critical tactical bulk petroleum storage for military operations for over 50 years. Beginning in the 1940s with the 900 to 3,000-gallon pillow tanks, collapsible fabric tanks have evolved into the primary tactical fuel storage vessels now used by all of the military services.

Posted in: Materials, Coatings & Adhesives, Aerospace, Defense, Briefs

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Materials Design Principles for the Dynamic Fracture of Laminar Composite Structures

Providing significant improvements in impact and ballistic resistance via materials and structural design. Army Research Office, Research Triangle Park, North Carolina Crack bridging (e.g., from stitches or pins) and friction have profound and potentially very useful effects on delamination crack growth, controlling growth rates (damage levels) and the energy absorbed. However, the implications for structural design principles have remained quite obscure. The difficulty is that no simple analogue of crack toughness, which underpins static structural design, exists for dynamic cases with large-scale bridging effects. The external shape of the structure and the loading configuration dictate stress waves, frictional contact zones, and crack tip stress intensity factors in a way that is very difficult to approach, other than by brute case-specific numerical simulation. The problem is compounded by the common occurrence of multiple cracking, a complexity that is rarely entertained in laboratory fracture specimen design. Physically sound material models for the important structural problem of multiple, nonlinear cracking in laminated structures with large-scale bridging due to friction and reinforcement had previously remained undeveloped, in spite of the technological importance of these systems.

Posted in: Information Sciences, Electronics & Computers, Materials, Aerospace, Defense, Briefs

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