Materials

Friction Stir Welding of Aerospace Materials

AFRL scientists are studying a unique metal joining process— friction stir welding (FSW)—for building major structural assemblies. FSW is a solid-state welding process that forces a spinning tool along the joint line, heating the abutting components by friction and producing a weld joint formed by strong plastic mixing (stirring) of the two components' constituent materials. FSW promises to be a highly efficient and cost- effective alternative to the conventional fusion welding routinely used for joining structural alloys on military and civilian aircraft.

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Integrated Aircraft Oxygen Sensor

Shortly after its takeoff from New York City on July 17, 1996, Trans World Airlines (TWA) Flight 800 exploded over the Atlantic Ocean and crashed. The accident investigation board determined that the center wing fuel tank caught fire and exploded. Although the ignition source remains unknown, it was unquestionably the presence of a combustible fuel/air mixture in the center wing fuel tank that caused the resulting

explosion.

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Nonchromated Treatment for Aluminum Surfaces

AFRL scientists and engineers recently completed development of a nonchromated treatment for aluminum aircraft surfaces and structures. The new treatment method is the result of a collaborative effort between AFRL, Boeing Phantom Works, and the Aeronautical Systems Center's Aging Aircraft Systems Squadron (ASC/AASS). The development of a non-chromatebased aluminum conversion coating fulfills one of several Air Force (AF) initiatives intended to provide aircraft manufacturers and maintainers with an environmentally safe corrosion protection method. Conversion coating is a metal finishing process that involves the application of a coating to a base metal to increase corrosion resistance and prepare the surface for additional coatings.

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Ground-Penetrating Radar

AFRL engineers used prototypes of recently developed ground-penetrating radar (GPR) and electronic cone penetrometer (ECP) devices to determine whether voids and anomalies in a particular airfield's subsoil were facilitating crack formation in an aircraft runway. Using the data collected during their Langley Air Force Base (AFB), Virginia, investigation, they were able both to determine the extent (and, in some cases, the cause) of the subsoil deterioration and to provide several recommendations for repairing abnormal or weakened portions of the runway. This field investigation also provided valuable information about the AFRL-developed prototype inspection devices; the evaluation results will aid designers in further refining these developmental products.

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Materials Knowledge Base

A team of scientists, engineers, and developers from AFRL and RJ Lee Group, Inc., recently completed functional prototype development of the Materials Knowledge Base (MKB), an object-based data repository for laboratory materials characterization information. Constructed as part of a Small Business Innovation Research (SBIR) Phase II contract, MKB demonstrates enormous potential to affect the way data collection, processing, storage, and sharing occurs. The prototype knowledge base and data management system supports AFRL's aerospace materials research and development efforts, paving the way for unprecedented project collaboration and data accessibility that the development team believes will revolutionize the way AFRL scientists and engineers collect, process, store, and share materialsrelated data.

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AFRL Supports C-5A Evaluation Program

AFRL materials integrity experts are collaborating with the Aeronautical Systems Center's C-5 Systems Group, Warner Robins Air Logistics Center (WR-ALC), and Air Mobility Command (AMC) in an effort to disassemble and analyze components of an out-of-service C-5A aircraft. Members of the 653rd Combat Logistics Support Squadron at WR-ALC extracted the major components from the aircraft and shipped them to participating laboratories for analysis (see Figure 1). This study is the first of its kind performed on the C-5A, the US Air Force's (AF) largest cargo aircraft. General John W. Handy (USAF, Retired), former AMC commander, requested the study in order to determine if the C-5A's structure and components are fulfilling original design predictions and to evaluate the aircraft's long-term maintenance requirements.

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Microelectromechanical Systems Switch Simulator

AFRL materials scientists developed a highly sophisticated laboratory instrument that simulates the effects of physical forces and electrical current on microelectromechanical systems (MEMS) switches. The simulator's performance has induced revolutionary insights into microscale switches—how they work and what causes them to fail.

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Strain-Induced Porosity Model

AFRL scientists developed advanced computer models to improve the processing and quality of titanium alloys used in manufacturing gas turbine engine parts and critical structural components for military aircraft. AFRL transferred both the models and the basic materials knowledge to titanium mill suppliers to help them eliminate strain-induced porosity (SIP)—also known as cavitation—in billet products (see Figure 1) and finished parts. The models also increase product yield by reducing the amount of scrap material, which helps lower production costs.

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Conductive Polymeric Nanocomposite Materials

AFRL scientists have developed a method for uniformly dispersing carbon nanofibers throughout polymeric materials to increase their conductivity. Engineers will be able to employ the resulting polymeric nanocomposites in conductive paints, coatings, caulks, sealants, adhesives, fibers, thin films, thick sheets, tubes, and large structural components needed for both aerospace and industry applications.

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Composite Material Fire Safety Training Course

AFRL scientists and engineers, working cooperatively with experts from academia and the firefighting community, have developed a Composite Material Fire Safety training program designed to improve the safety and effectiveness of Air Force, Department of Defense (DoD), and civilian firefighters. The team created the program to educate firefighters on the methodologies they need to rapidly and safely extinguish composite materials fires.

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