D. Lin, M. F. Zamora, P. D. R. Kovacevic, Southern Methodist University, Dallas, TX
The focus of this investigation is the feasibility study of paint removal from a typical aircraft skin structure consisting of a thin substrate of aluminum alloy, 2024 T3 or 7075 T6, a thin primer layer, and a thin layer of topcoat paint. In certain cases, the topcoat of paint must be removed for aircraft paint repair. To remove the damaged topcoat of paint, the Center for Laser-aided Manufacturing (CLAM) at Southern Methodist University has developed an innovative technology that successfully removes the topcoat paint without damaging the underlying primer layer and the aluminum alloy substrate.
The developed paint-removal technology is based on a hybrid approach which integrates a short pulsed laser beam from the direct diode laser with a cold air stream from a cooling system. Preliminary results have shown that: (1) a direct diode laser with continuous or pulsed waves will burn the primer, or even substrate, and so fail to effectively remove the topcoat paint, and (2) a pulsed laser beam in conjunction with a cold air stream can efficiently de-bond the topcoat paint from the primer layer transforming the topcoat into loose, reticulated particles with segment sizes around 100 µm. Temperature measurements on the backside of the specimen, EDX analysis after paint removal and the study of various laser parameters have been performed to optimize this process.
Summary: Paint removal of aircraft skin without damaging underlying primer and aluminum substrate is a chanllenging task. Chemical solution can be used for paint removal, but it’s hard to control the removal rate and it is not environmentally friendly. Short pulse laser ablation can remove the paint but it generates fine powder which could cause health-related problems to the operators. The low-cost technology developed at Southern Methodist University is environmentally friendly and does not generate the fine powder.
