Three-dimensional elastic constitutive relations of aligned carbon nanotube architectures

Tailorable anisotropic intrinsic and scale-dependent properties of carbon nanotubes (CNTs) make them attractive elements in next-generation advanced materials. However, in order to model and predict the behavior of CNTs in macroscopic architectures, mechanical constitutive relations must be evaluated. This study presents the full stiffness tensor for aligned CNT-reinforced polymers as a function of the CNT packing (up to ∼20 vol. %), revealing noticeable anisotropy. Finite element models reveal that the usually neglected CNT waviness dictates the degree of anisotropy and packing dependence of the mechanical behavior, rather than any of the usually cited aggregation or polymer interphase mechanisms. Combined with extensive morphology characterization, this work enables the evaluation of structure-property relations for such materials, enabling design of aligned CNT material architectures.NECST ConsortiumUnited States. Army Research Office (Contract No. W911NF- 07-D-0004)United States. Army Research Office (Contract No. W911NF-13-D-0001)United States. National Aeronautics and Space Administration (NASA Space Technology Research Fellowship Grant No. NNX11AN79H)National Science Foundation (U.S.) (Grant No. CMMI-1130437

Judging Fat Steers.

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The dominant ethnic moment: towards the abolition of 'whiteness'?

International audienc

Electron microscopy and small angle scattering studies of ionomer and block copolymer morphology/

Polymer Science and EngineeringDoctor of Philosophy (PhD

Phase Contrast Imaging of Styrene/Isoprene Block Copolymers

SAXS shows that in polystyrene (PS)/polyisoprene (PI) block copolymers with lamellar morphologies there is a sufficient electron density difference for x-ray scattering [1]. It has been accepted, however, that this difference is insufficient for TEM imaging by amplitude contrast. Therefore, contrast has been produced by staining the PI phase with OsO4 [2]. Staining changes the mechanical and chemical structure of the PI phase perhaps altering the phase separation and the domain interfaces (figure 1).Mean inner potential calculations, however, show potentials of 8.29V for PS and 7.57V for PI. This indicates that for a simple specimen geometry (e.g. lamellar) with sharp phase interfaces oriented parallel to the incident beam, a film 500Å thick will provide a phase change (Δψ) of 0.3 radians at 100 KV. This phase change is sufficient for imaging under defocus conditions and contains information about the interface region between the domains. The phase change may be increased by using lower voltage (50% increase at 40 KV).</jats:p