A discussion of rain erosion testing at the United States Air Force rain erosion test facility

Abstract

For the past twenty-five years the University of Dayton Research Institute has operated the Rain Erosion Test Facility for the United States Air Force Wright Laboratory Materials Directorate at Wright-Patterson Air Force Base, Ohio. This is a commercially available, whirling-arm facility that produces a 25.4 mm per h rain field and is capable of providing specimen velocities up to 290 m s −1 (650 mile h −1, 0.87 Mach). Various attack angles of specimen-to-rainfall are also possible ranging from 15° to normal. The average rainfall drop size is 2 mm (0.079 in). The facility is in use on a daily basis and serves the aerospace community on virtually a world-wide basis. Almost 40 000 test specimens have been evaluated as of January 1994. This paper will describe the facility in some detail. The method of testing and operation will be described and discussion will include the many types of specimens and materials that can be tested—ranging from metals, composites, plastics, honeycomb constructions, glass/optical, ceramics—and their allowable size and configurations. The mode of operation and the evaluation procedures used will be detailed. Failure mechanisms as erosion and adhesion loss will be discussed and related to materials performance and applications. Work in this facility has become the cornerstone for testing to many Military Specification coatings' requirements. It has been referred to as a ‘national resource’ by USAF personnel.