Repair of Damaged Fiber-Reinforced Polymer Composites with Cold Spray

The promising structural properties of fiber-reinforced polymer composites make them widely popular in the energy, automotive, defense, and aerospace industries. One of the most challenging limitations associated with the application of composites is their maintenance and repair. In this study, a polymer cold spray approach is introduced as an efficient alternative for the structural repair of fiber-reinforced polymer composites, without the use of additional repair media. Damage in the form of circular tapered holes is created in glass fiber-reinforced polymer (GFRP) composite substrates using conventional drilling. This damage is repaired by cold spray with thermoplastic (nylon 6) and thermosetting (polyester epoxy resin) materials. The fundamental adhesion mechanisms near the repair surface are investigated through microstructural observations and highlight the role of adiabatic shear instability due to the occurrence of severe plastic deformation in the particle impact zone. Microstructural examinations also suggest that no significant fiber damage or surface degradation occurs due to 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. Additionally, the cold spray-repaired GFRP samples are compared with conventional epoxy resin repair methods. Results obtained in this work highlight cold spray as a promising and rapid technique for the on-site repair of composite structures with minimal pre-/post-processing requirements.