Scratch Resistance Testing of Pilot Helmet Visors Using a New Scratch ResistanceTester

摘要

The causes for removing pilot helmet visors from service were investigated aspart of the Armstrong Laboratory's Advanced Aircrew Vision Protection (AAVP) program. The purpose of the investigation was to identify the factors which limit visor service life so that better technologies, specifications, or procedures could he developed and applied to the laser eye protection (LEP) visors being transitioned to the Human Systems Center (HSC) under the AAVP program. It was determined that the single cause of visor degradation which resulted in removing it from service was scratches in or delamination of the surface hardcoating (Reference AL/OE-TR-1996-0117, Failure Mechanisms in Pilot Helmet Visors). It was found that no specific scratch resistance requirements or specifications are applied to Pilot helmet visors. Abrasion resistance and coating adhesion are specified in MIL-V-43511C and MIL-C-83409 but not scratch resistance. A new apparatus, the Maier Scratch Resistance Tester (MSRT), for testing the scratch resistance of optical coatings was invented and two prototype Maier scratch resistance testers (MSRTs) were fabricated. These testers were used to test the scratch resistance of pilot helmet visors from three different manufacturers. The tests on the visors were performed by two different operators, using two different MSRTs with one type of stylus. The tests described here were the initial tests performed with the new MSRT apparatus and had the following objectives: 1) to investigate the repeatability and consistency of the results obtained by different operators and for different MSRTs; and 2) to establish baseline scratch resistance characteristics, values, and variability for existing hard coatings which are used on Air Force pilot helmet visors.