Repair of Damaged Fiber Reinforced Polymer Composites with Cold Spray

In this present work, a novel cold spray approach is introduced as an efficient alternative for the structural repair of fiber composites. Damages in the form of circular holes are created in glass fiber reinforced polymer (GFRP) composite substrates. The in-lab created damages are repaired by cold spray with thermoplastic (Nylon 6) and thermoset (Polyester epoxy resin) feedstock. A parametric study has been performed to correlate the quality of the cold spray repaired parts with the process parameters, gas carrier pressure, temperature, and flow rate for thermoplastic feedstock as well as different curing conditions (e.g., gel curing, conventional curing) for thermoset PCF powder. The fundamental adhesion mechanisms are characterized through microstructural observations which point to adiabatic shear instability due to the occurrence of severe plastic deformation as the governing factor. Supplemental computational simulations indicate that no fiber damage and surface degradation occur after the repair by cold spray. Mechanical tests performed on neat, damaged, and repaired composites reveal the partial recovery of structural performance and load-bearing capacity after cold spray repair. Results obtained in this work establish the feasibility of the cold spray as a promising alternative technique for onsite structural repair of composite structures with minimal pre/post processing required.