Y.C. Hsu

National Tsing Hua University, Hsin-chu-hsien, Taiwan, Taiwan

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Publications (3)1.99 Total impact

  • H.-C. Cheng · Y.-C. Hsu · W.-H. Chen
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    ABSTRACT: Due to the limitation of fabrication technologies nowadays, structural or atomistic defects are often perceived in carbon nanotubes (CNTs) during the manufacturing process. The main goal of the study aims at providing a systematic investigation of the effects of atomistic defects on the nanomechanical properties and fracture behaviors of single-walled CNTs (SWCNTs) using molecular dynamics (MD) simulation. Furthermore, the correlation between local stress distribution and fracture evolution is studied. Key parameters and factors under investigation include the number, type (namely the vacancy and Stone-Wales defects), location and distribution of defects. Results show that the nanomechanical properties of the CNTs, such as the elastic modulus, ultimate strength and ultimate strain, are greatly affected by the defects and also their percentage and type. It is also found that the CNTs present a brittle fracture as the strain attains a critical value, and in addition, the fracture crack tends to propagate along the high tensile stress concentration area. Moreover, the distribution pattern of defects is another driving factor affecting the nanomechanical properties of the CNTs and the associated fracture evolutions.
    No preview · Article · Jun 2009 · Computers, Materials and Continua
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    ABSTRACT: The study aims at developing a next-generation flip chip (FC) packaging technology that employs a novel anisotropic conductive adhesive (ACF) made of unidirectional Co-nanowire-reinforced polymer nanocomposite, and moreover, exploring the associated process-induced, thermal-mechanical behaviors during bonding process. For carrying out the process simulation, a process-dependent finite element modeling (FEM) methodology is proposed. The investigation starts from the theoretical and experimental assessments of the elastic properties the nanoscale Co metal using molecular dynamics (MD) simulations and nanoindentation testing, respectively, followed by the determination of the thermal-mechanical material properties of the nanocomposite, using the proposed FEM-based effective modeling approach. The predicted results are compared with those obtained from the widely-used rule-of-mixture (ROM) technique and existing analytical models, and also, with those from experimental measurements. At last, factors that most influence on the thermal-mechanical behaviors of the novel technology are also investigated through parametric FE analysis and Taguchi method.
    No preview · Conference Paper · Nov 2008
  • W.H. Chen · H.C. Cheng · Y.C. Hsu
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    ABSTRACT: The evaluation of the fundamental mechanical properties of single/multi-walled carbon nanotubes(S/MWCNTs) is of great importance for their industrial applications. The present work is thus devoted to the determination of various mechanical properties of S/MWCNTs using molecular dynamics (MD) simulations. The study first focuses on the exploration of the effect of the weak inlayer van der Waals (vdW) atomistic interactions on the mechanical properties of S/MWCNTs. Secondly, in addition to the zig-zag and armchair types of CNTs, the hybrid type of MWCNTs that comprise a zig-zag outer tube and an inner armchair tube is also analyzed. Thirdly, the investigation is extended to deal with the influence of the axial orientation mismatch between the inner and outer layers of MWCNTs on the associated mechanical properties. Lastly, the behaviors of the interlayer shear force/strength of MWCNTs are discussed in detail. In the MD simulations, the force field between two carbon atoms is modeled with the Tersoff-Brenner (TB) potential while the inlayer/interlayer vdW atomistic interactions are simulated with the Lennard-Jones (L-J) potential. The effectiveness of the MD simulations is demonstrated by comparing the computed results with the theoretical/experimental data available in literature. Some interesting and essential results are presented. With different dimensions and geometries of CNTs, the inlayer vdW atomistic interactions can have up to about 9% increase of the elastic moduli, 27% decrease of the Poisson's ratios, 12% growth of the shear moduli, and 13% enhancement of the interlayer shear strength. The mechanical properties of the hybrid MWCNTs are found to be midway between the zig-zag and armchair MWCNTs. It is also detected that the axial orientation mismatch between the inner and outer layers of a double-walled CNT has a trivial impact on the mechanical properties of CNTs. To separate the inner layer of a double-walled CNT from its outer layer, it requires a minimum external force of 0.889nN for the zig-zag type, 0.550 nN for hybrid type and 0.493nN for the armchair type. In summary, the effect of the inlayer vdW atomistic interactions can not be neglected and should receive attention in the MD simulations of the mechanical properties of CNTs.
    No preview · Article · Aug 2007 · Computer Modeling in Engineering and Sciences