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Air Safety Week, Nov 14, 2005

From Dec. 13 through Jan. 13, 2006, the Department of Defense (DoD) will be accepting proposals for its small business innovative research (SBIR) program, which applies to the needs of the commercial sector. The military services have published topics for which they are seeking proposals, which in a way point out gaps in current knowledge. For example, the Air Force has published a list of more than 250 topics for which it is seeking research proposals. When the unique weapons-system topics and such are stripped away, many of the remainder have civilian applicability. Winning companies will receive a $100,000 grant to prove the feasibility of their approach. Phase II, to be competed later, will involve a $750,000 grant to develop a working prototype to be installed or tested.

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Here are extracts of four topics that have commercial applicability for which the Air Force desires proposals:

Automated Delamination Onset and Growth Prediction in Composite Structures (Project number: AF06-092):

Objective: Develop a software package with which to perform automated delamination onset and growth prediction in composite structures containing an initial crack.

Description: A working relationship with a commercial software vendor is recommended. Demonstration of predictive abilities versus data will also be required. Important features of this product shall include (a) use of any common commercial off the shelf (COTS) finite element solver ... (c) ability to efficiently define initial crack geometry ... (d) ability to determine 3D strain energy release rates (SERRs) for multiple delamination areas on a single plane ... (e) ability to determine SERRs at mesh corners and in growth directions that are not normal to the as-meshed crack front ... and (f) ability to automatically determine efficient delamination area ... sizes based on growth-rate gradients.

Dual use commercialization: This technology can be applied to all composite structures in DoD or civilian applications.

Fatigue-Resistant Wire for Airborne Applications (Project number: AF06- 132):

Objective: Develop fatigue resistant electrical wire technology for application in high vibration airborne environments.

Description [ASW note: what follows is an excellent description of the wire 'problem']: An observed failure mode in aircraft ... instrumentation

systems, etc. is the simple open circuit created by wire breakages in electrical circuits. This breakage is caused by the harsh environment that the aircraft imposes on the electrical wire - causing abrasions, defective insulation, loose terminations, and potential corrosion. These severe conditions cause problems with grounding connections for power, distribution equipment, and electromagnetic shielding, which in turn causes electrical bonding resistance to significantly increase due to corrosion or loosening of connections.

Variables that may affect wire degradation are creep (time), thermal variations, electrical loads, mechanical loads (bending, static, dynamic/flexure, abrasions, vibration, thermal expansion), chemicals (cleaners, hydraulic fluid, lubricants, deicing fluids, etc. from aircraft), humidity, oxidizers (Ozone, NOx, SOx, etc.), radiation (heat, ultraviolet), and biological organisms. It is desirable that the wire has a high tolerance for these environmental conditions. These wires must have sufficient mechanical strength to allow for these conditions, but wire properties must not cause excessive voltage drop levels and must meet circuit current carrying requirements.

The occurrence of wire breakage/degradation is often noted at termination/connection points or other stress points subject to the effects of high vibration flight environments. These occurrences result in aircraft downtime and higher maintenance costs. Innovative technologies in mechanical design and/or fatigue resistant wire technology are required to resist these affects experienced by current technology.

Dual use commercialization: The automobile and civilian aircraft industry will greatly benefit from the application of the technology.

Delamination and Water Intrusion Detection (Project number: AF06-346):

Objective: Develop a reliable process/instrument and engineer a design to detect delamination and water intrusion in advanced composite structures. [ASW note: the effect of entrained water on composite structures was made evident earlier this month when an F-15C fighter out of Kadena, Okinawa, lost part of its left horizontal stabilizer in a training flight about 115 miles northwest of Okinawa over water. Maintenance personnel had determined the in-flight emergency was caused by "water incursion into the left horizontal stabilizer," which is of composite construction. The water froze and expanded at high altitude, causing part of the stabilizer's leading edge to break away under the stresses, or G loads, that maneuvers place on fighter aircraft.]

Description: Two common damage states of advanced composites include delamination and water intrusion. Detection of each is critical. The current method involves tap testing. Though primitive in this age of technology, tap testing continues to be the preferred method of damage detection in DoD advanced composite structures due to the unreliability of advanced methods utilized thus far. It is proposed, however, that current detection methods can be improved to be more reliable and accurate, or that a completely new process can be developed for damage detection. An automatic process that requires minimal analysis would be preferable, especially since such a process would be lower cost than one that demands scrutiny by testers and since such a process could eliminate much human error.

Government Industry

Knowledge Gaps

Air Safety Week, Nov 14, 2005

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