Rain impact testing of durable coatings on water-clear ZnS

摘要

Abstract: Quantitative measurements of the influence of high-speed rain impact damage on uncoated water clear ZnS as a function of velocity and impact exposure were made using Nomarski microscopy, total integrated scattering, integrated spectral transmission and equibiaxial flexural testing. The rotating arm tests assessed the response of the material to nominal 2 mm diameter drops at normal incidence. The measure of drop exposure selected for these studies was the density of drop impacts expected to strike the specimen for the test conditions (rain rate, velocity, run time, and spatial distribution of drops). The expected exposure is compared to measurements on PMMA calibration specimens. The influence of high durability coatings on the water clear ZnS was assessed using the same characterization methods. The limitations imposed by statistical variability illustrate the difficulty of comparisons made without adequate control of the parameters.!1