The Wiper Abrasion and Rain Erosion Resistance of Transparent Materials and Coatings for Aircraft Glazing,
ROYAL AIRCRAFT ESTABLISHMENT FARNBOROUGH (ENGLAND)
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The requirements for improved abrasion and rain erosion resistance of transparent materials for helicopters and aircraft glazing have led to the development and application at NPL of a laboratory-scale wiper abrasion apparatus, and also to an investigation using the RAE rain erosion rig. The NPL apparatus employs the linear motion of a short windscreen wiper blade across a 50 mm diameter specimen. The characteristics of the blade, chosen to produce even and reproducible abrasion over the rubber area. Surface condition is assessed in detail by Nomarski interference microscopy with a quantitative estimation of abrasion damage from profilometry, light scatter and transmittance measurements. The RAE rain erosion rig enables specimens to be exposed in a simulated rain field under conditions of known velocity and impact angle. Detailed examinations have been made of the progressive effects of rain erosion by weight loss and transmittance measurements. The in-service degradation of glazing materials as simulated by these techniques are compared.