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A novel approach based on conventional solution-coating and wire-drawing processes has been employed for the production of carbon nanotube (CNT) coated conductors. The solution process employs a mesoscopic building block, a CNT fibril dispersion formed in acid from forest-grown, long-length multiwall CNTs, to help bridge the transition from nanomaterials to thick, highly aligned technical coatings. The coatings are formed onto a roughened copper wire former through dip-coating. The roughened surface provides for mechanical attachment between the CNT coating and copper wire core that allows for the composite to be wire-drawn while wet to further shape, densify, and align the CNT coating. The wet chemistry approach offered a facile integration of different CNT and dopant types in the CNT coatings. For the specific process described here, it was observed that the CNT coatings were simultaneously doped with acid and copper nanoparticles. Coated wires were produced with conductivities on par with copper but in an engineered material that is lighter than the pure metal analogue. Dense coatings up to 90 μm in thickness were made that comprised up to 60% of the wire cross-sectional area and enabled composite densities to dip below half that of copper. The CNT coated wires had overall resistivities in the range 2.1–5 μΩ·cm, with specific conductivities relative to copper as high as 108%. The ubiquitous nature of the solution coating and conventional wire drawing processes may enable a novel approach to the light-weighting of advanced conductors for a broad range of applications.

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Additively manufactured polymers can be reinforced with high-performance reinforcements such as carbon fibers. Printed thermoplastics with embedded continuous carbon fibers are up to two orders of magnitude stronger and stiffer than high-grade 3D printed polymers. In this work, the mechanical response of such 3D printed carbon fiber specimens is evaluated. While the precursor carbon fiber reinforced filaments achieve a stiffness of 50GPa and strength 700MPa, mechanical properties of their printed parts are highly affected by printed carbon fiber curvatures. In this work, the structure of 3D printed parts was examined, and some design rules for 3D printing with continuous carbon fibers are suggested. Moreover, failure mechanisms in these samples are discussed and correlated to the micro-structure of the composites and the carbon fiber configuration.

The paper presents results of an experimental study conducted to understand the effect of a bio-inspired blade planform on the small propeller thrust and energy consumption. In the study, the Cicada wing was used as a prototype for the blade planform. This blade planform was combined with symmetric (NACA 0015) and asymmetric (NACA 64(4)-221) airfoils resulting in two propellers with bio-inspired blades. The comparative analysis of these two propellers is complimented with the analysis of two propellers with rectangular blades with the same profiles: NACA 0015 and NACA 64(4)-221. The two airfoils were selected for the study based on a review of airfoils suitable for small rotorcrafts, which are of interest for our research. The blade span and the blade planform area of the four propellers are the same. The propellers were manufactured using the 3D printing technology, which affects the blade shape and surface. A study was conducted to analyze the effect of 3D printing on the performance of the propellers with the NACA 0015 blade profiles. In the paper, the performance of propellers with untreated blades, that is, right after their printing, is compared with that of the same propellers, but with the blades soaked several times in a chemical solvent that smoothed the blade surface/shape.

Here, we report our understanding of carbon nanotube (CNT) solution coating and wire drawing processes toward fabricating high conductivity coated conductors from millimeters long CNTs. The approach studied here enables the formation of dense and aligned coatings of CNTs on various substrate wires. To achieve the coating, millimeters long and vertically aligned multiwalled carbon nanotube arrays were first dispersed in diluted sulfuric acid via mild shear mixing, forming mesoscale CNT fibrils. The resulting fibrils were solution coated onto a substrate wire (i.e., nylon or copper here) and the coating was subsequently wire drawn. During each drawing step, the CNT coated wire was passed through a die to decrease the coating thickness and to coax the CNTs to pack. Effects of various key processing parameters on the structure and resulting electrical conductivity of the coated wires were investigated. Especially, it was shown that the coating quality was strongly controlled by the surface characteristics of the wire former, where both a rough and hydrophobic surface were required. Microscopy and Raman spectroscopy were utilized to probe the structure of CNTs in the coatings. The continuous coating process discussed here can be used to manufacture high conductivity coatings for applications such as electrical wiring, electromagnetic and radio frequency shielding, electrostatic dissipation, and radar absorption. This approach holds the promise for the scalable manufacturing of lightweight CNT-based conductors.