Investigation of the bending response of carbon nanotubes reinforced laminated tapered spherical composite panels with the influence of waviness, interphase and agglomeration

A technique to detect the random failure in composite structures is presented. The epoxy matrix material is made conductive by the incorporation of carbon nanotubes. The modified matrix is used to fabricate glass fiber/epoxy/carbon nanotubes composite panels. Conductive grid points made from silver-epoxy paste are attached on the surface of the composite panels, so that electrical resistances in the regions between the grid points can be measured. The increase in electrical resistance between grid points is used to determine the increase in deformation (and possibly cracks) at the region between the grid points. It is found that the location of maximum increase in electrical resistance jumps from point to point as the number of cycles during fatigue loading is increased. This shows the random nature of the development of damage in the composites. The technique can detect the occurrence of early failure, usually in the matrix materials. The result of this work brings out the random nature of the early failure in composites. This also sheds light into whether the concept of crack initiation in composites is valid, since the early cracks jump around. When the paths of the final cracks reach stability, there is rapid crack propagation leading to fast final failure.

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Investigation on the flexural response of multiscale anisogrid composite panels reinforced with carbon fibers and multi-walled carbon nanotubes

Journal of Composite Materials ◽

10.1177/0021998317704981 ◽

2017 ◽

Vol 52 (2) ◽

pp. 225-233 ◽

Cited By ~ 6

Author(s):

Reza Eslami-Farsani ◽

Alireza Shahrabi-Farahani

Keyword(s):

Carbon Nanotubes ◽

Energy Absorption ◽

Carbon Fibers ◽

Composite Structures ◽

Glass Fibers ◽

Bending Test ◽

Composite Panels ◽

Flexural Response ◽

Multi Walled Carbon Nanotubes ◽

Walled Carbon Nanotubes

Grid stiffened composite structures have been maturely developed in aircraft and automobile industries due to their excellence properties such as high specific strength, high specific stiffness, excellent energy absorption capability and corrosion resistance. In the current investigation, the effect of multi-walled carbon nanotubes addition in various weight percentages (0, 0.1, 0.25 and 0.4) on the flexural response of anisogrid composite panels was evaluated. For fabrication of the composite specimens, hand lay-up method was used where plain weave E-glass fibers and unidirectional carbon fibers impregnated to the epoxy resin that modified with multi-walled carbon nanotubes were used in the skin and rib parts, respectively. Experimental results from three-point bending test showed that with the addition of 0.4 wt.% of multi-walled carbon nanotubes, the maximum flexural load, flexural stiffness and energy absorption of anisogrid composite panels increased by 24%, 35% and 25%, respectively. Microscopic analyses revealed that the improvement in the flexural properties of anisogrid composite panels with the addition of multi-walled carbon nanotubes was due to improvement in the interfacial properties of matrix and fibers.

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Structural phenomena in the growth of carbon nanotubes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100149581 ◽

1993 ◽

Vol 51 ◽

pp. 750-751

Author(s):

Jun Jiao

Keyword(s):

Carbon Nanotubes ◽

Growth Mechanism ◽

Carbonaceous Material ◽

Cluster Growth ◽

Structural Elements ◽

Rich Variety ◽

Different Shapes ◽

Point To Point

HREM studies of the carbonaceous material deposited on the cathode of a Huffman-Krätschmer arc reactor have shown a rich variety of multiple-walled nano-clusters of different shapes and forms. The preparation of the samples, as well as the variety of cluster shapes, including triangular, rhombohedral and pentagonal projections, are described elsewhere.The close registry imposed on the nanotubes, focuses attention on the cluster growth mechanism. The strict parallelism in the graphitic separation of the tube walls is maintained through changes of form and size, often leading to 180° turns, and accommodating neighboring clusters and defects. Iijima et. al. have proposed a growth scheme in terms of pentagonal and heptagonal defects and their combinations in a hexagonal graphitic matrix, the first bending the surface inward, and the second outward. We report here HREM observations that support Iijima’s suggestions, and add some new features that refine the interpretation of the growth mechanism. The structural elements of our observations are briefly summarized in the following four micrographs, taken in a Hitachi H-8100 TEM operating at an accelerating voltage of 200 kV and with a point-to-point resolution of 0.20 nm.

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