Key Engineering Materials Vol. 550

Abstract: This paper describes a new technique allowing the monitoring of damage in metallic freestanding thin films during micro-tensile test by using electrical characterization. After a presentation of the set-up, results obtained on Aluminium thin coatings by using two calculation methods for damage variable are presented and commented.

Abstract: PolyVinyliDene Fluoride (PVDF)/Calcium carbonate (CaCO₃) composites were processed with incorporation of different weight fractions (1, 2 and 10 wt %) of CaCO₃ particles into PVDF matrix using melt blending method. The influence of CaCO₃ on the structural, thermal and mechanical properties of PVDF polymer was evaluated by using a variety of technique of characterization such as scanning electron microscopy (SEM), X-Ray diffraction (XRD), differential scanning calometry (DSC), thermogravitometric analysis (TGA) and uni-axial tensile test. It was found that the addition of CaCO₃ particles results in an increase of thermal stability and some selected tensile properties of PVDF polymer.

Abstract: This study is fulfilled to simulate numerically the interaction phenomenon of the bidimensional compressible and supersonic flow with M=2.28 of a turbulent boundary layer with an oblique choc wave. The oblique choc wave is released and oriented by a generator of choc in an angle of θ_w=8° on a plate plane maintained at a constant temperature. The interaction causes the detachment of the boundary layer and make it disturbed (The case of experimental study done by J. Deleuze (1995)). The contribution on the effects of turbulence and their characteristics is represented by k-w-SST model. This model is well adapted for this type of application. This study permits to underline the coherence of our analysis with existant numerical and experimental results. This simulation is effected by means of solver which based on the spatio-temporal discretization of the complex equations of Navier-Stockes with finite volumes method. We also use the Upwind scheme of second order.

Abstract: This paper presents a three dimensional finite element model for armchair, zigzag and chiral single-walled carbon nanotubes (SWCNTs). The influences of diameter, chirality and length on the elastic moduli (Young’s modulus and shear modulus) of SWCNTs are investigated. The formulation presented is based on the assumption of viewing the construction of SWCNTs as a geometric frame-like structure. The interatomic interactions of bond length, bond angle, bond torsion and non-bonded interactions are equivalent to corresponding structure features straightforwardly. The models of SWCNTs are developed according to the atomistic structure network of nanotubes. The interatomic interactions of C- C atoms are simulated via appropriate straight spring and torsional spring elements. The computational results indicate that both diameter and chirality have a significant effect on the Young’s and shear moduli of SWCNTs, while the elastic moduli are not very sensitive to the variation of length. It is also shown that with a similar radius, armchair SWCNT has a slight higher value of Young’s modulus than zigzag and chiral SWCNTs. While zigzag SWCNT has a slight higher value of shear modulus than armchair and chiral SWCNTs.

Abstract: Most of nanostructures are desired in nanodevices in order to perform their characteristics. Tiny, strong and stable nanomaterials are needed to get functional nanosensor, nanoactuator and nanodevices. For those reasons, we introduce the single walled carbon nanotube (SWCNTS) as a high flexural and cylindrical nanocantilever to reduce the electrical and mechanical lost energy. Therefore, a bundle of SWCNTs in cylindrical geometry with a diameter of about 5 nm and 60 nm as long was designed in clamped-free cantilever feature. Due to the exceptional mechanical and geometrical characteristic of SWCNT, the first resonance frequency was calculated by analytical method to be of 150MHz. Further research, the SWCNT nanocantilever could be covered with a thin piezoelectric layer such as PZT, ZNO, AlN, PVDF...to realize nanactuators, nanosensors and nanodevices. The proposed methodology directly supports quality engineering aspects enabling to specify the manufacturing to achieve desired product reliability. Within this context, the robust design obtained is optimal over the range of variable conditions because it considers uncertainties during the optimization process. The large number of exact evaluations of problem, combined with the typically high dimensions of Finite Element models, makes reliability-based optimization procedures very costly, sometimes unfeasible. Those difficulties motivate the study reported in this paper, in which a strategy is proposed consisting in the use of reliability-based optimization strategy combined with measurement and sensitivity technique specially adapted to the structures of industrial interested. Keywords: single walled carbon nanotubes, nanocantilever vibration, clamped-clamped, clamped-free. Reliability, Finite Element Method.

Abstract: This study presents the measurement of fields of displacement and deformations on butt joints in hydrostatic depression. The aim of this paper is to observe the general behaviour of the rubber. Various definitions of butt joints were tested in traction. We are interested on the types of fracture and the phenomenon of vacuolization, which occurs in the rubber.