Materials Parameters that Govern the Rain Erosion Behavior of Polymeric Coatings and Composites at Subsonic Velocities
Technical rept. Aug 1968-Oct 1970
AIR FORCE MATERIALS LAB WRIGHT-PATTERSON AFB OH
Pagination or Media Count:
Subsonic investigations of polymeric coatings, bulk polymers, and fiber reinforced polymeric composites are described for their erosion behavior and the influence of materials variables on their erosion response. Polymeric coatings such as epoxies, polyesters, and amide-imides are brittle relative to the impinging water droplets with rupture of the film occurring very rapidly. The most resistant coatings such as elastomeric polyurethanes typically show no surface erosion at all but fail at isolated points associated with a breakdown of the composite i.e., glass-epoxy UNDERNEATH THE COATING. Other elastomeric coatings such as neoprene will gradually erode on the surface by structural failure or tearing within the film erosion of the composite then follows. The elastomeric coatings protect the surface by pulse attenuation of the impact load and by protecting the composite from the radial outflow of the impinging drop. The modulus of these coatings is related to their performance in a rain environment since it governs the stress level which is transmitted to the substrate. The void content and type of reinforcement are shown to significantly influence the behavior of fiber reinforced composite structures in a subsonic rain erosion environment whether uncoated or coated. The effects of various fiber lay-up schemes with a particular fiber reinforcement have been found to be minor compared to void content effects.
- Coatings, Colorants and Finishes
- Laminates and Composite Materials