Application of Stress Sensing Coatings on Metal Substrates with a Sub-surface Notch

Abstract

The future of aerospace structures is highly dependent on the advancement of reliable and high performance materials such as composite materials, ceramics, and metals. The application of photo-luminescent α-alumina nanoparticles in coatings allows for various structural materials to be evaluated nondestructively for stress and damage. The capabilities of these coatings and their ability to monitor the underlying substrate were measured by using photoluminescence piezospectroscopy (PLPS). Different volume fractions of α-alumina nanoparticles in the piezospectroscopic (PS) coatings were studied for determining the sensitivity of the coatings on 2024 aluminum tensile substrates with subsurface notches. Here, it was found that the 10 vol % PS coating better captured the location and the extent of the subsurface notch than the 1 vol% PS coating. Application of the PS coating can provide potentially invaluable information to monitor structural integrity of aerospace structures and allows for preventive measures to be taken before failure. I. Nomenclature ∆ν = average frequency shift ∆ν = frequency shift Π i j = PS coefficients (or PS tensor) σ i j = stress tensor Π ii = trace of the PS tensor σ j j = trace of the stress tensor