In-Flight Environmental Effects on Airplane Composite Vertical Fin Caps 871800

An investigation of the effects of severe in-flight weather environments on composite structures has been conducted as part of the NASA Langley Research Center Storm Hazards Program. The program used an extensively-instrumented F-106B airplane to make thunderstorm penetrations. The vertical fin cap was chosen for the experimental composite structure because of the likelihood of lightning strike attachments and the ease of component replacement. Four components were flown and investigated. The first was the U.S. Air Force production glass/epoxy fin cap which Was flame-sprayed by NASA with aluminum for lightning protection. The second fin cap was fabricated with Kevlar/epoxy fabric skins and used an aluminized glass cloth for lightning protection. The third fin cap was fabricated with graphite/epoxy fabric skins with no lightning protection. The fourth fin cap was fabricated with graphite/epoxy fabric skins with no lightning protection, and was electrically isolated from the airplane structure. All four components were exposed to high rain rates and direct lightning strikes. The effects of the flight environments on the components were monitored visually and areas of interest photographed. The performance of the four fin caps and required repairs are reported herein.