Innovative laser heating methodology study for crack growth retardation in aircraft structures

Aging aircraft, both in military and commercial sectors, present a risk of air safety to the crew and passengers. The air safety risk associated with older aircraft is structural degradation often in the form of fatigue. Neglecting the extent of fatigue crack growth can result in detrimental effects to the aircraft and, in turn, to the people on board. This paper discussed the evaluation on a unique method for reducing the growth rate of fatigue cracks in aluminum alloy sheet materials commonly used in aircraft fuselage. This is accomplished by a laser heating technique using a CO2 laser which results in thermally inducing a sufficiently high tensile residual stress at a region in front of the crack without altering the microstructure or the strength of the material. The methodology associated with this technique was evaluated in two steps: parametric study of key processing variables using finite element method and experimental testing of fatigue samples for crack growth. 2024-T3 aluminum alloy sheet was chosen for the study. Results to date indicate that the laser heating process has great potential as a means to retard fatigue crack growth in aluminum sheet, and thus can improve the life of aircraft skin structures.