Evaluation of cold spray for aircraft repair

icaf2023 Tracking Number 136

Aircraft parts are subjected to stringent regulations to maintain airworthiness. As a result, minor corrosion or mechanical damage can disqualify a part and require replacement even though the majority of the part is acceptable. For complex parts that are difficult and expensive to manufacture in low production runs, it can be more economical to use an additive manufacturing repair process such as cold spray (CS) repair to restore the original part geometry without manufacturing an entire part. This extends the life of existing parts and thereby, extends the usable life of the aircraft. Substantiation is the first step to achieving certification for the repair on certified aircraft. A logical and conservative analysis approach to substantiate the repair of non-structural and structural parts has been developed using stress analysis and material property generation [1]. Often prior to the substantiation, a comprehensive test matrix is carried out to determine the material allowables of the cold spray material system. The substantiation analysis incorporates this new information in a logical progression. The result is a process that is useful for non-structural and ultimately structural part repair. Cold spray is being use in both civil aviation and military aircraft fleets as a method for repairing obsolete or damaged parts mainly for dimensional repair. There is ongoing research examining the corrosion and mechanical property equivalency of CS repairs on aluminium alloys for structural applications on aircraft. Coupon testing has shown that CS repairs of fatigue sample geometries with 15-30% blend outs depths are able to improve fatigue life to near that of a standard fatigue coupons. Tensile coupons with 15% depth CS repairs have also shown tensile properties within 90% of wrought material for two alloy systems. Various coupon geometries have been used to evaluate how cold spray repairs would perform, all have shown promising results. Bending and pin-bearing testing has also been conducted, both show excellent bond performance of the cold spray and acceptable mechanical properties. All the work developing coupon data is critical to building the material database which will allow for additively manufactured or repaired parts to be installed on aircraft [2]. [1] Sarah Galyon Dorman, and Scott Fawaz (2019). FAA Certification of Cold Spray Dimensional Repair. 2019 Cold Spray Action Team (CSAT) Workshop, Worcester, MA. [2] Kabbara, J. and Gorelik, M., 2016, “FAA Perspectives on Additive Manufacturing,” from http://www.nianet.org/ODM/ODM%20Wednesday%20presentations%20Final/7%20Kabbara%20On-Demand%20Workshop%20AM%20Presentation(03-09-2016.pdf.