This study aims to develop a metal-based compatibilizing sublayer on a Carbon Fiber-Reinforced Polymer (CFRP) composite to overcome the erosion issue of polymer substrate using the cold spray deposition technique. The objective is to contribute to the in-situ repair of aircraft structures. Two cases of sublayers, i.e., Al-based sublayer (1126 μm thick) and Cu-based sublayer (547 μm thick), have been prepared and co-cured with the CFRP substrates by pressure assisted molding process. Gas-atomized copper powders were deposited on a reference sample of aluminum panel (A-0) and on two functionalized composite substrates (A-1 and C-1) by a high-pressure cold spraying (HPCS) process. The results show that cold spray deposition onto the Al-based sublayer leads to a coating formation whereas the Cu-based sublayer is strongly eroded by the supersonic collision of copper powders. Scanning electronic microscope (SEM) morphologies were used to investigate the HPCS deposition mechanisms on various configurations of substrates. It was found that the high deposition efficiency of case Cu/A-0 was achieved by metallic bonding, evidenced by the significant flattening powders and agglomeration phenomenon of multiple particles. The copper particles of case Cu/A-1, encapsulated by the deformed aluminum powders, could anchor to the substrate via mechanical interlocking, whereas only pure localized fracture of epoxy and exposed broken carbon fibers were observed on the substrate of case Cu/C-1. The results demonstrated the feasibility of an Al-based sublayer-assisted cold spray process for the thermosetting CFRP composite to achieve a successful deposition of copper powders, which also emphasized the necessity to search an optimal material coupling between sublayers and coatings.

Supersonically Induced Mechanical Alloy Technology (SIMAT™) also known as gas-dynamic spraying is under development for corrosion protection and material repair for aluminum airframe structures. This technology enables material powder consolidation that is not possible using other spray technologies. Similar to cold spray but based on compact spray head with nozzle powder feed, SIMAT™ is a low temperature process and does not create the high-temperature environment that affects both the substrate (especially thermally non-stable substrates) and the deposited coating. The emerging SIMAT™ technology, now in development, has the potential for coating, repairing, joining and rapid prototyping powder based materials. The SIMAT™ method adds new flexibility to powder material deposition producing thin to very thick deposits of various metals and metal-ceramic mixtures based on a cold spray particle kinetic approach inducing impact fusion. Solid particles in the size range of 10 to 100 microns are accelerated into a supersonic stream (ranging from 300 to 1200 m/s) using compressed air. These high velocity cold particles are projected on to a work piece. There is no heat discharge in the spray device itself, thus the powder material retains original characteristics. This spraying technique can generate a wide range of deposited layers with thickness ranging from tens of microns up to as much as centimeters. The process extends beyond the concept of “coatings” and includes the capability for in-situ material build-up and consolidation to three-dimensional structures and joining of the components. The deposition and consolidation can be performed from a range of hybrid powders consisting of metals, alloys, ceramics and glasses. Sample tests demonstrate examples of the process on typical aircraft components for new or restored corrosion protection and demonstrate damage repair for potential service life extension of the aircraft structure.