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Desert Sand Meets its Match in New Military Testing Standards

  • Published
  • By Lynn Pfledderer
  • Materials and Manufacturing
WRIGHT-PATTERSON AIR FORCE BASE, Ohio --  Today's Air Force operates in hot, arid, sandy environments that are tough on systems and their components. Reliable testing of protective materials is essential to assess their durability and safe operation, but it has been discovered that the decades-old characterizations of sand don't match the reality of today's warfighter experience.

Thanks to work by the Air Force Research Laboratory, there is a new military standard for measuring the resistance of materials used to prevent particle and sand erosion on the leading edges of rotor blades. The standard will be used to assess protective materials for systems and components, such as jet engine turbine blades, helicopter rotor blades, electric power turbine blades, thermal protection coatings, and missile materials. Testing was conducted using AFRL's particle erosion test apparatus, which researchers use to formulate new materials and application methods intended to protect aircraft from erosion damage.

Harsh desert environments have resulted in a growing need to test aerospace material capabilities at ambient and elevated temperatures to determine their resistance and durability to particle and sand erosion. Until recently, sand characterization requirements that originated at the Department of Geology at the University of Chicago in 1941, and specifically the Krumbein particle roundness and sphericity chart developed by W.C. Krumbein, were used to determine particulate shape and size used in material and coating testing. AFRL researchers discovered that sand from dry and arid theaters of operation differed from those covered in aging standards.

AFRL's particle erosion test apparatus was developed by the Defense Nuclear Agency in the late 1980s to simulate dust effects on aircraft surfaces at ambient temperatures in a post-strike nuclear environment. During an Office of the Secretary of Defense-funded effort in 2007, researchers characterized numerous natural sand samples which ultimately led to the identification of a more aggressive synthetic test media to better replicate damage on aerospace materials exposed to a dry-arid environment. Additionally, the size range and particulate cloud density for the new test method were verified with sand characterization results accomplished during touch-and-go flight testing in Yuma, Arizona.

The particle erosion test apparatus is operated and maintained by personnel from the University of Dayton Research Institute (UDRI) by way of an on-site contract with the CTIO. A cooperative research and development agreement between AFRL and UDRI accommodates testing for commercial and industrial customers. The CTIO also offers rain erosion testing in its Rain Erosion Test Facility and the newly integrated Supersonic Rain Erosion apparatus. Customer requests for combined effects erosion testing can also be accommodated.

In March 2011, personnel from AFRL's Systems Support Division and the University of Dayton Research Institute received the Defense Standardization Program Award for Excellence at the 2010 Defense Standardization Program Awards ceremony at the Pentagon. The award was presented for their development of test methods and military standards that measure the particle and sand erosion resistance of materials used in aerospace systems.