Deposition and characterization of flame-sprayed aluminum on cured glass and basalt fiber-reinforced epoxy tubes

An oxy-acetylene flame spray torch was used to deposit thin layers of aluminum onto cured glass and basalt fiber-reinforced epoxy tubes. The composite specimens were fabricated by filament winding. Surface coatings embedded in composite laminates were produced. The composite substrates were grit blasted to promote adhesion of the molten aluminum particles. It was found that adhesion increased significantly when the composite substrate was lightly grit blasted, with no adhesion on smooth composite surfaces. The number of passes of the flame spray torch was varied to change the coating thickness and uniformity over the substrate. The electrical resistance of the coatings was measured to assess the suitability of a coating as a conductor. It was found that uniform, electrically conductive coatings were produced with a minimum of two torch passes. Optical images were captured to characterize the coating microstructure and thickness. This investigation did not reveal any visible evidence of damage to the composite substrate. To assess possible degradation effects from the grit blasting and flame spraying processes, the tube specimens were subjected to mechanical testing by applying internal pressurization with hydraulic oil. The tests indicated that the grit blasting and flame spraying processes must be carefully executed to mitigate degradation of the strength of the composite material substrate.