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July 2, 2010 — Two graduate students in the Department of Aerospace Engineering at Texas A&M University received $1,000 stipends from the federal government to present papers at the 2010 Aircraft Airworthiness & Sustainment (AA&S) conference. Nirmal Sigamani presented his paper, "Characterization of Polyurethane at Multi-Scales for Erosion Mechanisms under Sand Particle Impact." Sourav Banerjee presented his paper, "Durability of Polymer Films for Erosion Protection of Helicopter Rotor Blades Impacted by Sand Particles." Both papers stemmed from Sigamani and Banerjee’s work on the Helicopter Rotor Blade Erosion project, which brings together resources from Texas A&M’s aerospace engineering faculty, researchers, graduate students and post docs; the Texas Engineering Experiment Station’s (TEES) Texas Center for Applied Technology (TCAT) managers; the University of Dayton Research Institute; and the United Technologies Research Center, as well as donations from 3M. Blade erosion in helicopters continues to be an area of concern in particular in severe environments of sand and rain.

The current approach to assuring safe performance relies upon frequent inspection, repair, and replacement of protection films without sound and reliable procedures. The consequences are costly. New erosion resistant coatings are being developed but there are no physics based models available to guide their development. In short, the current state of affairs employs situation-specific reaction without a clear strategy to advance the industry to a knowledge-based plan for cost-effective safe performance.

The Helicopter Rotor Blade Erosion research program systematically addresses the erosion problem. This program, now in its third year, is focused on polyurethane films that are mounted on the leading edge of blades to provide protection from erosion caused by sand particles. A comprehensive strategy has been devised to accomplish three interrelated objectives: determine the impact conditions for particles in the airflow field interacting with the rotor blades; clarify the deformation and failure mechanisms leading to erosion of polyurethane films under the particle impact; and develop a predictive modeling methodology for erosion of polyurethane films mounted on a rigid substrate undergoing particle impact. The overall goals are to provide guidelines for maintenance (i.e., inspection, repair, and replacement), of polyurethane protection systems (films and coatings) for safety against blade erosion; to help designers of rotor blades to incorporate erosion in blade design; and to provide directions for developing erosion resistant films and coatings.

This project has supported numerous Texas A&M graduate students pursuing their degrees in aerospace engineering. To date, two students have received their Master of Science in Aerospace Engineering (MSAE), three students are completing their MSAE, three have completed their Ph.D. degrees, and one will be entering into the Ph.D. program. The AA&S conference, formerly known as the Aging Aircraft Conference, brought together leaders from government, industry, foreign nations, and academia to exchange perspectives and information about critical areas of interest, such as wiring, corrosion, structures, space, avionics, obsolescence, and airworthiness. "To promote student participation in AA&S, this year NASA sponsored 23 full-time students from 12 universities to present at the conference. Sigamani’s and Banerjee’s research in rotor blade erosion was selected for presentation because it addresses a relevant sustainment issue confronting the rotorcraft community," said NASA’s Dr. Richard Young, a member of the conference organizing committee.

Conference sponsorship is rotated between NASA, the Federal Aviation Administration and the U.S. Department of Defense (DoD); this year the DoD was the host. For its 13th annual conference, the federal government looked beyond the classical focus on older aircraft, adding new topics that are intended to anticipate and position the community to proactively deal with airworthiness and sustainability issues in existing and future systems. There were more than 100 different speakers presenting in five individual technical tracks.