Honeycomb Structural Sealants-New Sealer Coatings

Water leakage and entrapment is a common problem for helicopters honeycomb composite structures. Reports from Army repair depots indicated that about 20% of the CH47(Chinook) blades returned for service had water trapped in 3,000 - 5,000 honeycomb cells. Problems are also present in Blackhawk, Cobra, and Heuey helicopters. Micro cracks in the composite skin are believed to be the main cause of the problem. Water entrapment prevents adequate rotor track and balance for rotor blades, which causes vibration problems and increased maintenance. Water entrapment adds weight to composite floor panels and fuselage skins, decreasing mission capability. Damage to honeycomb structures due to water leakage and entrapment is very time consuming to repair. Typical phase maintenance interval for rotor blades is 500 hours, but a great number of blades have to be serviced after only 300-400 hours. It is the objective of this contract proposal to find a solution to the above common and expensive problem. The contractor proposes to evaluate different types of sealer coatings and to develop application technologies to prevent water leakage and entrapment problems. Among materials to be tried are new generation hybrid urethane erosion resistant coatings developed by this contractor and other commercial waterproofing sealer coatings. The new sealer coatings will find immediate applications in helicopter rotor blades, floor panels and fuselage skins. Other commercial uses are as sealer coatings for: radomes, landing gear doors, fairings, flaps, trailing edges, structural parts, racing cars, skis, yachts, military shelters, truck superstructures, and sports equipment.