MECHANICAL-BEHAVIOR OF 2024-AL-ALLOY SPECIMEN SUBJECTED TO PAINT STRIPPING BY LASER-RADIATION AND PLASMA-ETCHING

Paint removal is required in a series of aeronautical procedures such as maintenance and repair. Today's paint stripping processes which are based on application of chemicals and abrasion are inadequate for mod em aircraft structures in addition to environmental contamination, Sev eral alternative techniques are in progress. However, the aspect of ma terial property degradation when developing novel, alternative paint s tripping techniques has not been properly faced up to present. The inf luence of two novel paint stripping processes on the mechanical proper ties of the substrate 2024 T351 aluminium alloy has been investigated. The paint stripping processes included laser radiation with excimer, CO2, TEA-CO2 and YAG laser sources as well as plasma etching. These pr ocesses have been applied for the removal of polyurethane coating whic h is a typical aeronautical paint system. The results indicated no sig nificant degradation in yield strength and ultimate tensile strength. However a significant degradation in tensile ductility and toughness i s observed with the application of all paint stripping processes, the highest degradation being associated with the ultraviolet excimer lase r and plasma etching. On the other hand there is a considerable extens ion in fatigue life, which depends on the paint stripping process and the applied stress amplitude. At high stress there is no appreciable e ffect while at low stress there is an order of magnitude life extensio n associated with CO2 laser paint stripping. At moderate stresses, the re is an up to sixfold life extension associated with the excimer lase r processing.