Nanoparticle reinforced composites are greatly desired by the aerospace community for a multitude of applications for their tailorable quasi-isotropic mechanical properties such as the high strength-to-weight ratio. With increasing demand of structural nanoparticulate composites, the optimization of their structural integrity and performance can be improved with a better understanding of the load transfer mechanics. Extensive nanoparticulate composites research has focused on the roles of particle shape, size, and volume fraction on the mechanical properties. Nanocomposites are often experimentally characterized through the determination of the bulk composite material properties. Load transfer research with a micro-mechanics perspective, distinguishing particle and matrix behavior, has been explored significantly using analytical and finite element modeling. For a more complete understanding of load transfer mechanics of particle composites, high spatial resolution experiments measuring exclusively the particles strain response are valuable. In this work, photoluminescent piezospectroscopy (PLPS) uses the frequency shift of the stress sensitive R-lines to non-destructively establish the mechanics of 100 nm, 150 nm, and 350 nm Cr3+ doped -alumina nanoparticles in an EPON 826 matrix under applied compressive stress. The R-lines' stress sensitivity represented by the piezospectroscopic (PS) coefficient is used here to assess the particles' load transfer capability. The PS coefficients allow us to investigate the load transfer variation with three different nanoparticle sizes. As the particle size reduces from 350 to 100 nm, the PS coefficients show that the particles experience 59% more stress indicating that the load transfer escalates with smaller particle sizes. This work also utilizes the R-line luminescent lifetime decay and assesses its reliability for stress measurements of particles within the composites. The lifetime decay measurements demonstrated significant inconsistencies due to the large variation in particle dispersion. The findings unravel the effect of particle size, to support new load transfer models that can be leveraged to tailor the design of structural nanocomposites.
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Master of Science in Mechanical Engineering (M.S.M.E.)
College of Engineering and Computer Science
Mechanical and Aerospace Engineering
Mechanical Engineering; Mechanical Systems Track
Length of Campus-only Access
Masters Thesis (Open Access)
Vo, Khanh, "Effect of Particle Size on Mechanics of Particle Reinforced Composites using Photoluminescence Piezospectroscopy" (2023). Electronic Theses and Dissertations, 2020-. 1688.