The CNT sheet fabricated by the floating catalyst chemical vapor deposition (CVD) method has attracted great attention due to its easy fabrication process and promising mass production at low cost. However, the randomly oriented CNT sheet with a loose stacking density shows relatively poor mechanical properties. In this work, a highly aligned dense CNT sheet was successfully fabricated by a simple process of two-time stretching and pressing of a multilayered CVD-grown CNT sheet. Drastic nanotube rearrangements occurred during stretching and pressing processes. A polymer-like tensile necking behavior was observed during the stretching process, accompanied by inter-tube junction breakage due to long-distance slippage. Simultaneously the CNT sheet was thickened after the stretching process due to the increase of the inter-layer space, which could be effectively eliminated by the following pressing treatment. After two-time stretching and pressing, a highly aligned dense CNT sheet was fabricated with the volume density increasing to 0.98 g cm(-3) (by 109%) and the tensile strength increasing to 598 MPa (by 221%) compared to the as-prepared CNT sheet.
Three-dimensional (3-D) spacer fabric composite is a newly developed sandwich structure, the reinforcement of which is integrally woven by advanced textile technique. Two facesheets of 3-D spacer fabric are connected by continuous fibers, named pile in the core, providing excellent properties like outstanding integrity, debonding resistance, light weight, good designability and so on. Usually the 3-D spacer fabric composite without extra reinforcement is a kind of core material. In comparison with the facesheet reinforced spacer fabric composite, here the composite without additional weaves is called monospacer fabric composite. In this paper, two kinds of mono-spacer fabric composites with integrated hollow cores have been developed, one with 8-shaped piles and the other with corrugated piles. The mechanical characteristics and the damage modes of these monospacer fabric composites under different load conditions have been investigated. Besides, effects of pile height, pile distribution density and pile structure on the composites mechanical performances were analyzed. It is shown that the mechanical performances of mono-spacer fabric composites can be widely adapted to the respective requirements through the choice of the structural factors.
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