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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.

Posted in: Briefs, Materials
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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.

Posted in: Briefs, Materials
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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.

Posted in: Briefs, Materials
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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.

Posted in: Briefs, Materials
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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.

Posted in: Briefs, Materials
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Automated Material Deposition Chamber

AFRL materials scientists have acquired an automated deposition chamber (see figure on next page) that enables them to simultaneously or sequentially deposit solid-lubricant coatings onto target objectives from any of three deposition sources. The chamber also incorporates AFRLinvented technology entailing a hybrid, magnetron-assisted, pulsed-laser deposition (PLD) process. The scientists acquired the chamber to study protective solid-lubricant coatings capable of resisting wear and corrosion in (relatively) large friction components, including gears and bearings, and preventing static friction in microelectromechanical systems devices such as switches and connectors.

Posted in: Briefs, Materials
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Computational Model of a Plasma Actuator

Controlling subsonic aerodynamic flow through the use of plasma actuators is an active area of research in both the Air Force (AF) and the general scientific community. A typical plasma actuator consists of two offset electrodes separated by a dielectric material (see Figure 1). Plasma forms as the voltage difference between the electrodes ionizes the surrounding gas. The electric field can then direct the charged particles in the plasma to transfer momentum to the surrounding, neutral (nonionized) air. Most of this momentum transfer occurs as a result of particle collisions. Experiments have demonstrated the ability of plasma actuators to reattach separated airflow at high angles of attack (see Figure 2), as well as to induce flow movement in an initially stationary air mass.1,2,3,4,5

Posted in: Briefs, Software
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AFRL Finding Ways to Decrease Unmanned Air Vehicle Costs

In support of the Aeronautical Systems Center's (ASC) Global Hawk Systems Group, AFRL has undertaken a program to study manufacturing tolerances for laminar flow on aircraft wings. On the drawing board, air vehicle designs have perfectly smooth aerodynamic surfaces, yet it is nearly impossible for manufacturers to fabricate those surfaces without some imperfections. Any surface imperfection, no matter how slight, can affect the properties of the boundary layer— the air flowing nearest an air vehicle's body during flight. In turn, this airflow dramatically impacts the amount of drag an air vehicle experiences. When the boundary layer is smooth, or laminar, drag is minimal; as the boundary layer becomes more turbulent, drag increases. Nonetheless, decreasing the amount of surface imperfection is not always a practical solution, because as the manufacturing processes become more stringent, they also become increasingly expensive and time-consuming endeavors. It is therefore vitally important to determine the relationship between the height, shape, and location of surface imperfections and the resulting performance degradation.

Posted in: Briefs, Mechanical Components
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Cyberspace Security via Quantum Encryption

Perfect information- theoretical security requires that the meaning of an encrypted message transmitted from point A to point B be statistically independent of the ciphertext in which that message is embedded. In other words, possession and analysis of the ciphertext must yield no information about the message sent. This article briefly describes cryptographic protocols exhibiting perfect, or nearperfect, security before addressing a new quantum data encryption protocol that employs quantum noise of light at the physical layer to buttress security based on mathematical complexity. This new protocol is called Keyed Communication in Quantum Noise, or KCQ. KCQ does not presently guarantee flawless informationtheoretical security; however, because of KCQ's physical-layer encryption in the quantum noise of light, some scientists believe that it enables better security than current secure communications systems based solely on mathematical complexity.

Posted in: Briefs, Photonics
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Unified Flow Solver

A variety of gas flow problems are characterized by the presence of rarefied and continuum domains. In a rarefied domain, the mean free path of gas molecules is comparable to (or larger than) a characteristic scale of the system. The rarefied domains are best described by particle models such as Direct Simulation Monte Carlo (DSMC); or, they involve solution of the Boltzmann kinetic equation for the particle distribution function. The continuum flows are best described by Euler or Navier-Stokes equations in terms of average flow velocity, gas density, and temperature and are solved by computational fluid dynamics (CFD) codes. The development of hybrid solvers combining kinetic and continuum models has been an important area of research over the last decade. Potential applications of such solvers range from high-altitude flight to gas flow in microsystems.

Posted in: Briefs, Software
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