Search results for "micromechanic"
showing 10 items of 64 documents
Effective electrical conductivity of carbon nanotube–epoxy nanocomposites
2016
The electrical conductivity of carbon nanotube–epoxy composites is investigated analytically and experimentally. The theoretical predictions of the effective electrical conductivity of carbon nanotube–epoxy composites were performed by the analytical approach based on a micromechanical model of composites. The parametric analysis carried out revealed an influence of geometrical and electrical parameters of the micromechanical model on the effective electrical conductivity of carbon nanotube–epoxy nanocomposite. The nanocomposites made from the DGEBA-based and RTM6 epoxy resins filled with different weight content of Baytubes C150P and N7000 multi-walled carbon nanotubes were prepared. The …
Micro-cracking of brittle polycrystalline materials with initial damage
2016
In this paper, the effect of pre-existing damage on brittle micro-cracking of polycrystalline materials is explored. The behaviour of single and multiple cracks randomly distributed within a grain scale polycrystalline aggregate is investigated using a recently developed grain boundary 3D computational framework. Each grain is modelled as a single crystal anisotropic domain. Opening, sliding and/or contact at grain boundaries are modelled using nonlinear cohesive-frictional laws. The polycrystalline micro-morphologies are generated using Voronoi tessellation algorithms in combination with a regularisation scheme to avoid the presence of unnecessary small geometrical entities (edges and face…
Boundary Element Crystal Plasticity Method
2017
A three-dimensional (3D) boundary element method for small strains crystal plasticity is described. The method, developed for polycrystalline aggregates, makes use of a set of boundary integral equations for modeling the individual grains, which are represented as anisotropic elasto-plastic domains. Crystal plasticity is modeled using an initial strains boundary integral approach. The integration of strongly singular volume integrals in the anisotropic elasto-plastic grain-boundary equations are discussed. Voronoi-tessellation micro-morphologies are discretized using nonstructured boundary and volume meshes. A grain-boundary incremental/iterative algorithm, with rate-dependent flow and har…
Characterization of MEMS accelerometer self-noise by means of PSD and Allan Variance analysis
2017
In this paper, we have studied the sources of error of a low-cost 3-axis MEMS accelerometer by means of Power Spectral Density and Allan Variance techniques. These techniques were applied to the signals acquired from ten identical devices to characterize the variability of the sensor produced by the same manufacturer. Our analysis showed as identically produced accelerometer have somehow variable behavior in particular at low frequency. It is therefore of paramount importance before their use in Inertial Navigation or Earthquakes Monitoring System, a complete characterization of each single sensors.
VIRTUAL ELEMENT METHOD FOR COMPUTATIONAL HOMOGENIZATIONS OF UNIDIRECTIONAL FIBER-REINFORCED COMPOSITE MATERIALS
2019
The Virtual Element Method (VEM) is a generalization of the Finite Element Method (FEM) for the treatment of general polygonal/polyhedral mesh elements. Despite its recent introduction, VEM has been applied to several problems in structural mechanics. Due to such capability of dealing with mesh elements of general shape and of naturally addressing the presence of hanging nodes, the VEM ensures a noticeable simplification in the data preparation stage of the analysis, allowing implementing a mesh generation process over complex multi-domain geometries in a fully automated way. Moreover, for the lowest order VEM used in this contribution,no numerical integration is required to compute the sys…
two-scale three-dimensional boundary element framework for degradation and failure in polycrystalline materials
2014
A fully three-dimensional two-scale boundary element approach to degradation and failure in polycrystalline materials is proposed. The formulation involves the engineering component level (macroscale) and the material grain scale (micro-scale). The damage-induced local softening at the macroscale is modelled employing an initial stress approach. The microscopic degradation processes are explicitly modelled by associating Representative Volume Elements (RVEs) to relevant points of the macro continuum and employing a three-dimensional grain-boundary formulation to simulate intergranular degradation and failure in the microstructural Voronoi-type morphology through cohesive-frictional contact …
Moisture effect on deformability of epoxy/montmorillonite nanocomposite
2010
In this article the moisture effect on deformability of epoxy/montmorillonite nanocomposite was investigated. The change of fracture character and drop of elastic characteristics due to moisture absorption was observed. The estimation of filler morphological peculiarities (platelet stack constitution) in composite and its effect on nanocomposite elastic properties was undertaken. It is shown that the higher number of filler platelet per stack consistently leads to the decrease of nanocomposite elastic properties. Nevertheless prediction by micromechanical model is rough for moistened nanocomposite because of resin structural changes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Multiwalled carbon nanotube reinforced polymer composites
2008
Due to their high stiffness and strength, as well as their electrical conductivity, carbon nanotubes are under intense investigation as fillers in polymer matrix composites. The nature of the carbon nanotube/polymer bonding and the curvature of the carbon nanotubes within the polymer have arisen as particular factors in the efficacy of the carbon nanotubes to actually provide any enhanced stiffness or strength to the composite. Here the effects of carbon nanotube curvature and interface interaction with the matrix on the composite stiffness are investigated using micromechanical analysis. In particular, the effects of poor bonding and thus poor shear lag load transfer to the carbon nanotube…
Single-step arbitrary control of mechanical quantum states in ultrastrong optomechanics
2015
We describe how ultrastrong interactions in optomechanical systems can be used to force the system ground state to evolve into an arbitrary quantum state of mechanical motion in a completely controlled and deterministic manner. If the target quantum state is a superposition of $N$ Fock states, it can be obtained by applying in single-step $N$ classical optical signals of different frequencies for a common time interval. This protocol can be applied to various strongly interacting quantum systems as trapped ions beyond the Lamb-Dicke regime and cavity QED into the ultrastrong coupling regime.
A BOUNDARY ELEMENT FORMULATION FOR MICROMECHANICAL HOMOGENIZATION OF POLYCRYSTALLINE MATERIALS WITH PIEZOELECTRIC COUPLING
2019
A novel boundary element formulation for the evaluation of the effective properties of threedimensional polycrystalline aggregates with piezoelectric coupling is presented. The aggregates are modelled at the scale of their constituent crystals and are artificially generated through Voronoi-Laguerre tessellations. The electro-mechanical behaviour of each crystal is represented upon introducing an ad-hoc mesh of its boundary and a generalised integral representation of the governing equations of the piezoelectric problem. The behaviour of the whole aggregate is then retrieved upon introducing a suitable set of electro-mechanical interface conditions at the grain boundaries. With respect to cl…