Integrated random-aligned carbon nanotube layers: deformation mechanism under compression

Abstract

Carbon nanotubes have the potential to construct highly compressible and elastic macroscopic structures such as films, aerogels and sponges. The structure-related deformation mechanism determines the mechanical behavior of those structures and niche applications. Here, we show a novel strategy to integrate aligned and random nanotube layers and reveal their deformation mechanism under uniaxial compression with a large range of strain and cyclic testing. Integrated nanotube layers deform sequentially with different mechanisms due to the distinct morphology of each layer. While the aligned layer forms buckles under compression, nanotubes in the random layer tend to be parallel and form bundles, resulting in the integration of quite different properties (strength and stiffness) and correspondingly distinct plateau regions in the stress-strain curves. Our results indicate a great promise of constructing hierarchical carbon nanotube structures with tailored energy absorption properties, for applications such as cushioning and buffering layers in microelectromechanical systems.

Interlocked CNT networks with high damping and storage modulus

“…Cheng et al [16] reported excellent mechanical properties for CNT film/bismaleimide composites, but its damping ratios decreased with the CNT alignment improvement. The CNT macroscopic assemblies (such as arrays [17,18], fibers [19], films [20,21], and sponges [22,23]) are also found to display structure dependent viscoelastic properties. Korathkar et al [24] fabricated a macroscopic dense-packing CNT film from vertically-aligned nanotube arrays, and the CNT network reinforced sandwich beam manifested a high damping ratio of 0.3.…”

Carbon Nanotube Sponges, Aerogels, and Hierarchical Composites: Synthesis, Properties, and Energy Applications

“…Enhanced CNT alignment with associated bundling events during creep was the main cause for property degradation. [ 102,103 ] In those reports, a double-layer composite was compressed and the process was monitored by SEM, which revealed morphology-dominated deformation mechanism (Figure 8 i-k). [ 80 ] A random CNT sponge can be connected tandem with an aligned CNT array, forming a well-defi ned all-CNT composite in series with distinct mechanical behaviors.…”

“…Additionally, the initial random entangled CNTs, as shown in Figure 8 h, was evaluated to play a signifi cant role in creep recovery. [ 103 ] Upon unloading, uniform and random networks reappeared in those bundling region due to the CNTs debundling and pores recovery. [ 102,103 ] In those reports, a double-layer composite was compressed and the process was monitored by SEM, which revealed morphology-dominated deformation mechanism (Figure 8 i-k).…”

“…[ 39 ] Mechanical tests revealed that these sponge-array composites significantly enhanced energy absorption and dissipation compared with individual sponges or arrays. [ 39,102,103 ] In addition, SWNT-MWNT array-based multi-component micropatterns were fabricated via a multiple contact-transfer technique. [ 104 ] In this report, a pre-designed pattern of MWNT arrays was contacttransferred to a PDMS sheet, and then a complementary pattern of SWNT arrays was transferred onto the MWNT-PDMS substrate, resulting in a 3D microarchitecture containing the SWNT and MWNT components with tunable nanotube orientation (Figure 4 d).…”

“…2016, 6, 1600554 www.MaterialsViews.com www.advenergymat.de Figure 8. [ 103 ] Copyright 2014, The Royal Society of Chemistry. a) Schematic of the structure in the CNT and AC-CNT sponges.…”