Experimental research on resistance of infrared optical windows to erosion caused by ice particle impact

The erosion resistance of infrared optical windows was studied experimentally using ice particles of 2 mm diameter. Single ice particles were accelerated to approximately Mach 4.7 using a two-stage light gas gun. Sapphire and zinc sulfide infrared optical windows were tested. The windows were impacted repeatedly until a linear or circumferential crack was found. From the normal impact tests, it was found that uncoated and AR-coated infrared windows have similar erosion characteristics. Damage threshold curves were determined from the test data to characterize the erosion resistance of the windows. From oblique impact tests, it was found that resistance to erosion from normal and oblique impacts is related by a trigonometric function based on damage threshold velocity (DTV).