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Wednesday 4 January 2017

Noncovalently functionalized multi-walled carbon nanotube with core-dualshell nanostructure for improved piezoresistive sensitivity of poly(dimethyl siloxane) nanocomposites

Published Date
Composites Part A: Applied Science and Manufacturing
March 2017, Vol.94:124132doi:10.1016/j.compositesa.2016.12.008

Author 
  • Biao Zhang 
  •  
  • Buyin Li ,
  •  
  • Shenglin Jiang ,
  • School of Optical and Electronic Information, Huazhong University of Science and Technology, No. 1037, Luoyu Road 1037, Wuhan 430074, China

Abstract

Poor sensitivity in low pressure regimes (<100 kPa) of pressure-sensitive rubbers (PSRs) is one of their major disadvantages compare to other piezoresistive materials. The reasons induced the poor sensitivity include bad dispersion and week interface of multi-walled carbon nanotubes (MWCNTs) applied in poly(dimethyl siloxane) (PDMS). A novel vinyl-terminated poly(dimethyl siloxane)-poly(phenylmethyl siloxane)-multi-walled carbon nanotubes (V-P-MWCNTs) with core-dualshell nanostructure is fabricated by noncovalently functionalized method. The V-P-MWCNTs as conductive fillers exhibits homogenous dispersion as well as good interfacial interaction in PDMS matrix. Slightly above the percolation threshold (0.19 vol.%), the PDMS-based nanocomposites with 0.2 vol.% of V-P-MWCNTs shows high piezoresistive sensitivity (22.16 × 10−3 kPa−1), high electrical conductivity (5.43 × 10−3 S/m) and low Young’s modulus (288.83 kPa). These results demonstrate that the V-P-MWCNTs are of great potential as the conductive fillers for improved piezoresistive sensitivity of PDMS nanocomposites, which can be potentially applied in the flexible touch sensors.

Keywords

  • A. Smart materials
  • B. Electrical properties
  • B. Mechanical properties 
  • C. Micro-mechanics



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      Corresponding author. Tel.: +86 2787542693; fax: +86 2787542693.
    For further details log on website :
    http://www.sciencedirect.com/science/article/pii/S1359835X16304353

    The effect of fiber meso/nanostructure on the transverse compression response of ballistic fibers

    Published Date
    Composites Part A: Applied Science and Manufacturing
    March 2017, Vol.94:133145, doi:10.1016/j.compositesa.2016.12.003
    • Author 
    • Preston B. McDaniel a,b,,
    • Subramani Sockalingam a,c
    • Joseph M. Deitzel a
    • John W. Gillespie Jr. a,b,c,d
    • Michael Keefe a,b
    • Travis A. Bogetti e
    • Daniel T. Casem e
    • Tusit Weerasooriya e
    • aCenter for Composite Materials, University of Delaware, DE, USA
    • bDepartment of Materials Science and Engineering, University of Delaware, DE, USA
    • cDepartment of Mechanical Engineering, University of Delaware, DE, USA
    • dDepartment of Civil and Environmental Engineering, University of Delaware, DE, USA
    • eUS Army Research Laboratory, Aberdeen Proving Ground, Aberdeen, MD, USA

    Abstract

    The goal of this research is to understand the effect of fiber meso/nanostructure on the macroscopic quasi-static transverse compression response of ultra-high molecular weight polyethylene (UHMWPE) Dyneema SK76 fibers. These fibers exhibit nonlinear inelastic behavior with a small elastic limit and negligible elastic recovery upon unloading. Finite element model predictions of the experiment, using a continuum nonlinear inelastic constitutive description agree reasonably well with experimental force-displacement, but under-predict the contact area. The apparent fiber cross-sectional area is found to increase up to a maximum of 1.83 times the original area at 46% nominal strain. SEM and AFM images of the meso/nanostructure of the compressed fibers indicate the apparent area growth is due to fibrillation. This fibrillation results in the deformation of a fibril network causing non-uniform fibril nesting and nucleation of new nanoscale voids between fibrils. A comparison of UHMWPE and Kevlar KM2 fiber transverse compressive response is also discussed.

    Keywords

  • Polymer (textile) fibers
  • Nano-structures
  • Mechanical testing
  • Finite element analysis (FEA)

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      Corresponding author at: Center for Composite Materials, University of Delaware, DE, USA.


    For further details log on website :
    http://www.sciencedirect.com/science/article/pii/S1359835X16304304

    A viscoelastic approach for modeling bending behavior in finite element forming simulation of continuously fiber reinforced composites

    Published Date
    Composites Part A: Applied Science and Manufacturing
    March 2017, Vol.94:113123, doi:10.1016/j.compositesa.2016.11.027
    • Author 
    • Dominik Dörr a,,
    • Fabian J. Schirmaier a
    • Frank Henning a,b
    • Luise Kärger a
    • aKarlsruhe Insititute of Technology (KIT), Institute of Vehicle System Technology (FAST), Department of Lightweight Technology (LBT), Karlsruhe, Germany
    • bFraunhofer - Institute of Chemical Technology (ICT), Pfinztal, Germany

    Abstract

    An approach for modeling rate-dependent bending behavior in FE forming simulation for either a unidirectional or a woven/bidirectional reinforcement is presented. The applicability of the bending model to both fiber architectures is guaranteed by introducing either an orthogonal or a non-orthogonal fiber parallel material frame. The applied constitutive laws are based on a Voigt-Kelvin and a generalized Maxwell approach. The bending modeling approaches are parameterized according to the characterization of thermoplastic UD-Tape (PA6-CF), where only the generalized Maxwell approach is capable to describe the material characteristic for all of the considered bending rates. A numerical study using a hemisphere test reveals that the Voigt-Kelvin approach and the generalized Maxwell approach lead to similar results for the prediction of wrinkling behavior. Finally, the approaches for modeling bending behavior are applied to a more complex generic geometry as an application test with a good agreement between forming simulation and experimental tests.

    Keywords

  • Forming
  • Process simulation
  • Finite element analysis (FEA)
  • Thermoplastic resin

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      Corresponding author.


    For further details log on website :
    http://www.sciencedirect.com/science/article/pii/S1359835X16304213

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