Authors: Alex P Selimov, Ryan Hoover, Quentin Fouliard, Albert C Manero, Peter Dackus, Declan Carolan, Ambrose Taylor, Seetha Raghavan
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Hybrid carbon fiber reinforced polymers (HCFRPs) are a new breed of material that are currently being explored and characterized for next generation aerospace applications. Through the introduction of secondary reinforcements, such as alumina nanoparticles, it is possible to achieve improved mechanical behavior and enable structural sensing to create unique hybrid properties. The photoluminescent properties of the alumina inclusions allow for the application of local stress measurements through piezospectroscopy (PS) in addi- tion to dispersion characterization. Measuring the shift in emission wavenumber at several points across the face of a sample allows for determination of the local stress through the application of the PS relationship. Measuring local intensity differences across the face of the sample, alternatively, allows for the determination of relative local particle concentra- tion for dispersion characterization. Through investigation of an HCFRP sample loaded with 10 wt% of alumina nanoparticles, it was found that stress was greater in regions with high relative particle concentrations upon mechanical loading. Further investigation also found evidence of particle-matrix debonding, characterized by a lower particle stress re- sponse to increasing composite strain at higher loads. In order to address both of these issues silane coupling agents are utilized to adjust particle behavior. It is found that the use of these treatments results in improved particle dispersion and reduced sedimentation. A reactive and non-reactive surface treatment were compared and it was found that the reactive treatment was more effective at improving dispersion for the weight percentage investigated. The outcomes of this work demonstrate the potential of utilizing the photo- luminescent sensing capability of these reinforcing particulates to tailor the design of the hybrid carbon fiber composites.