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 polyester-based thermoplastic polyurethane (TPU) fastener fill material prior to application of outer mold line primer and final finish coatings that ultimately define the stealth of the aircraft. This is currently a time-consuming, labor-intensive operation that results in a high potential for variations in installation quality from fastener to fastener. Systems and Materials Research Corporation (SMRC) proposes development of the Rapid Intelligent Fastener Fill System (RIFFS), an automated handheld tool that the operator simply places over an installed fastener head. With the press of a button, RIFFS dispenses a TPU dot over the fastener head, melts and compresses the dot to adhere to the primed fastener and fastener cavity while filling all crevices, and removes and disposes of excess TPU material above flush to the airframe - all in under 30 seconds. RIFFS accomplishes this by delivering near-infrared energy to the TPU dot, rapidly and uniformly melting the dot as a plunger compresses the material into the fastener cavity. In this Phase II program, fastener fill installation, melting, compression, and final finish techniques will be developed for use in RIFFS. BENEFIT: The Rapid Intelligent Fastener Fill System (RIFFS) will shorten fastener installation times to less than 30 seconds per fastener with minimal residual cleanup, while improving process safety, and reducing operator fatigue. With over 40,000 fasteners in the F-35 outer mold line and current fastener fill installation times of approximately 2 minutes per fastener, a potential savings of 1,000 hours per aircraft in direct labor may be realized, saving 312,000 man-hours per year at F-35 full rate production. RIFFS will be used by field maintainers as well as on the manufacturing floor to ensure that the low radar profiles engineered into the F-35 and other stealth platforms are sustainable throughout their life cycles.