Authors: Imad Hanhan, Alex P Selimov, Declan Carolan, Ambrose Taylor, Seetha Raghavan
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Abstract: Carbon fiber composites have become popular in aerospace structures and applications due to their light weight, high strength, and high performance. Recently, scientists have begun investigating hybrid composites that include fibers and particulate fillers, since they allow for advanced tailoring of mechanical properties, such as improved fatigue life. This project investigated a hybrid carbon fiber reinforced polymer (HCFRP) that includes carbon fiber and additional alumina nanoparticle fillers, which act as embedded nano stress sensors. Utilizing the piezospectroscopic effect, the photo-luminescent (PL) spectral signal of the embedded nanoparticles has been monitored as it changes with stress, enabling non-contact stress detection of the material. The HCRFPs stress-sensitive properties have been investigated in-situ using a laser source and a tensile mechanical testing system. Hybrid composites with varying mass contents of alumina nanoparticles have been studied in order to determine the e↵ect of particle content on the overall stress sensing properties of the material. Additionally, high resolution photoluminescent maps were collected from the surfaces of each specimen in order to determine the particulate dispersion of specimens with varying alumina content. The dispersion maps also served as a method of quantifying particulate sedimentation, and can aid in the improvement of the manufacturing process. The results showed that the emitted photoluminescent spectrum can indeed be captured from the embedded alumina nanoparticles, and exhibits a systematic trend in photoluminescent peak shift with respect to stress, up to a certain critical stress. Therefore, the non-contact stress sensing results shown in this work have strong implications for the development of multi-functional hybrid composites to support structural health monitoring and nondestructive evaluation (NDE) of aerospace structures.