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The penetration behavior of Kevlar fabric intercalated with dry particles and shear thickening fluids (STF), highly concentrated fluid-particle suspensions, is presented. In particular, the role of particle hardness is explored by comparing fabric treatments containing SiO(2) particles, which are significantly harder than Kevlar, to treatments containing softer poly(methyl methacrylate) (PMMA) particles. The fabric testing includes yarn pull-out, quasi-static spike puncture, and ballistic penetration resistance, performed on single fabric layers. It was found that both dry particle and STF treatments resulted in improvements in fabric properties relative to neat or poly(ethylene glycol) (PEG) treated fabrics. On comparison of treatments with different particle hardness, the SiO(2) materials performed better in all tests than comparable PMMA materials, although the SiO(2) treatments caused yarn failure in pull-out testing, reducing the total pull-out energy. In addition, resistance to yarn pull-out was found to be substantially higher for STF-treated fabrics than for dry particle treated fabrics. However, both dry particle addition and STF treatments exhibited comparable enhancements in puncture and ballistic resistance. These observations suggest that viscous stress transfer, friction, and physical entrainment of hard particles into filaments contribute to the demonstrated improvements in the properties of protective fabrics treated with shear thickening fluids.

Polymer electrolytes were investigated for potential use in multifunctional structural batteries requiring both mechanical and electrochemical properties. Electrolytes were formulated with a broad range of multifunctional behaviors, spanning continuously from highly conductive and structurally weak materials to poorly conductive and highly structural materials. Solvent-free polymer scaffolds were synthesized from monomers containing poly(ethylene glycol) (PEG) oligomers and one to four vinyl ester groups. The electrolytes were formed by dissolving lithium trifluoromethanesulfonate in the monomers prior to thermal cure. Electrochemical, mechanical, and viscoelastic properties were studied with respect to salt concentration, polymer chemistry, and polymer architecture. The addition of salt was found to have minimal impact on compressive stiffness, whereas it increased T g and significantly influenced ion conductivity, with a maximum conductivity at 9−12% salt w/w PEG. At a constant salt concentration, the homopolymer electrolytes exhibited close to a 1:1 inverse correlation between conductivity and stiffness as monomer composition was changed.

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Two-dimensional (2D) materials can uniquely span the physical dimensions of a surrounding composite matrix in the limit of maximum reinforcement. However, the alignment and assembly of continuous 2D components at high volume fraction remain challenging. We use a stacking and folding method to generate aligned graphene/polycarbonate composites with as many as 320 parallel layers spanning 0.032 to 0.11 millimeters in thickness that significantly increases the effective elastic modulus and strength at exceptionally low volume fractions of only 0.082%. An analogous transverse shear scrolling method generates Archimedean spiral fibers that demonstrate exotic, telescoping elongation at break of 110%, or 30 times greater than Kevlar. Both composites retain anisotropic electrical conduction along the graphene planar axis and transparency. These composites promise substantial mechanical reinforcement, electrical, and optical properties at highly reduced volume fraction.

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Dielectric capacitors with mechanical load-bearing capability have been constructed by laminating glass-epoxy prepregs with metalized film electrodes. Mechanical characterization and high-voltage testing are used to quantify the elastic modulus, mechanical strength, and dielectric energy density of these structural devices. An approach for predicting mass savings in systems utilizing multifunctional material structures is also presented. The experimental results show that, in spite of increases in void content with fiber volume fraction, overall structural capacitor performance is greatest at maximum fiber volume fraction. At these high-fiber volume fractions, the overall multifunctional performance of the structural capacitors is predicted to provide mass and volume savings over conventional designs.