Rapid Method for Aircraft Fastener Surface Preparation

Each of the more than 40,000 fastener heads in the F-35's outer mold line must be covered with a special thermoplastic conductive polymer fill prior to application of the primer and final finish coatings that will ultimately define the stealth of the aircraft. This is currently a time-consuming, labor-intensive operation, and the potential for fastener-to-fastener quality differences is high. Systems and Materials Research Corporation (SMRC) proposes development of the Rapid Intelligent Fastener Fill System (RIFFS), an automated handheld tool which the operator simply places over a fastener head. With the press of a button, RIFFS will secure itself to the airframe, accurately measure the cavity depth, then dispense, melt and compress a metered load of thermoplastic material into the fastener head cavity - all in under 30 seconds. Unlike current fastener fill procedures which take considerably longer and leave large amounts of excess thermoplastic material to be removed and disposed of, RIFFS dispenses 1-5 thin dots, designed to slightly overfill the cavity when melted and compressed. RIFFS delivers low power (2 watts) microwave energy to the dots, rapidly and uniformly melting them as a dielectric plunger compresses the conductive thermoplastic material into the fastener head cavity.