1,721,007 research outputs found
A class of auxetic three-dimensional lattices
No full textWe propose a class of auxetic three-dimensional lattice structures. The elastic microstructure can be designed to have an omnidirectional Poisson's ratio arbitrarily close to the stability limit of -1. The cubic behaviour of the periodic system has been fully characterized; the minimum and maximum Poisson's ratio and the associated principal directions are given as a function of the microstructural parameters. The initial microstructure is then modified into a body-centred cubic system that can achieve Poisson's ratio lower than -1 and that can also behave as an isotropic three-dimensional auxetic structure
Electro-chemo-mechanics of solid state batteries: inelastic response to lithium plating and stripping
No full textOne of the most important issues facing modern science is how to deal with the rising need for storage technologies and renewable energy sources. There is likely no cutting-edge technology that can replace lithium-ion batteries (LiBs) for such purposes. Although the high ionic conductivity allows liquid organic electrolytes (LoEs) to remain state-of-the-art for this type of technology, the safety concerns correlated with these devices induce scientists to study new types of batteries with different kinds of electrolytes. Solid-state electrolytes (SSEs) are considered promising candidates to replace LoEs, due to their higher energy density, non-flammability, mechanical properties and electrochemical stability against lithium metal. However, a few drawbacks, like high contact resistance, reduced ionic conductivity compared with a liquid electrolyte, dendritic growth and degradation at the Li-foil anode, affect contemporary SSEs. A correct mechanical characterization of SSEs becomes paramount. The current work investigates the mechanical response of an all-solid-state lithium battery (ASSB). An electro-chemo-transport-mechanics model, in the realm of continuum mechanics and thermodynamics, is here proposed to describe the behaviour of a battery cell, in which the negative electrode consists of a lithium metal foil. Lithium deposition on the anode surface, accompanied by the shrinkage and expansion of the cathode, has been considered to evaluate the outbreak of mechanical stresses. A detailed investigation of the mechanical problem of growth connected with the inelastic nature of lithium has been carried out. The problem has been originally framed using an elasto-plastic constitutive model for lithium foil, which has been later enhanced to highlight its rate-dependent nature. The electrochemical response of the cell is investigated in terms of electric potential and species concentrations to complete the model description. To substantiate the reliability of the proposed model, it was tested against experimental galvanostatic discharge curves on a commercial all-solid-state thin film battery (Raijmakers et al. 2020 Electrochim. Acta330, 135147 (doi:10.1016/j.electacta.2019.135147)) and from a mechanical perspective, against the experimental outcomes of a tensile test performed on a lithium sample. Predictive science could provide new tools to reveal the physical laws behind the pitfalls that penalize the smooth operation and the performance of the ASSBs
GRAPHENE OXIDE AS ADDITIVE FOR INCREASING THE STRENGTH AND DURABILITY PERFORMANCE OF EXISTING CONCRETE STRUCTURES
No full textGraphene and graphene-based nanosheets (GNS) have valid mechanical, thermal and electrical properties, enabling interesting applications for improving structural strength and durability. If combined with the Ordinary Portland Concrete (OPC), they can enhance its mechanical behaviour, an analogous improvement in terms of strength can also be seen in Ultra-High-Performance Concrete (UHPC). These features appear very useful in case of the restoration of existing concrete structures, thanks to the durability properties due to the GNS. Providing a wide state of the art about the use of GNS in concrete structures, this paper shows the strength improvements achievable in term of strength and durability. The benefits are finally discussed in relation to the restoration of existent concrete buildings
Auxetic two-dimensional lattices with Poisson's ratio arbitrarily close to - 1
No full textIn this paper, we propose a class of lattice structures with macroscopic Poisson's ratio arbitrarily close to the stability limit-1. We tested experimentally the effective Poisson's ratio of the microstructured medium; the uniaxial test was performed on a thermoplastic lattice produced with a three-dimensional printing technology. A theoretical analysis of the effective properties was performed, and the expression of the macroscopic constitutive properties is given in full analytical form as a function of the constitutive properties of the elements of the lattice and on the geometry of the microstructure. The analysis was performed on three microgeometries leading to an isotropic behaviour for the cases of three-and sixfold symmetries and to a cubic behaviour for the case of fourfold symmetry
Effective properties of a new auxetic triangular lattice: An analytical approach
No full textIn this article we propose a new auxetic periodic lattice with negative Poisson's ratio which tends to the limit v=-1 under particular conditions. We have studied its generation and kinematic, and we give a full description of the mechanical properties of this innovative model. Calibrating the geometrical configuration of the lattice and the mechanical properties of the constituent material we are able to have a Poisson's ratio which is arbitrarily close to -1
Rotational inertia interface in a dynamic lattice of flexural beams
No full textThe paper presents a novel analysis of a transmission problem for a network of flexural beams incorporating conventional Euler–Bernoulli beams as well as Rayleigh beams with the enhanced rotational inertia. Although, in the low-frequency regime, these beams have a similar dynamic response, we have demonstrated novel features which occur in the transmission at higher frequencies across the layer of the Rayleigh beams
Floquet–Bloch Waves in Periodic Networks of Rayleigh Beams: Cellular System, Dispersion Degenerations, and Structured Connection Regions
No full textThe paper is dedicated to Professor N. F. Morozov on the occasion of his 85th birthday. In the paper, we consider new dispersive properties of elastic flexural waves in periodic structures with rotational inertia. The structure is represented as a lattice with elementary bonds of Rayleightype beams. Although such beams in the semiclassical regime react as the classical Euler–Bernoulli beams, they exhibit new interesting characteristics as the dispersion frequency of flexural waves increases. Special attention is paid to degenerate cases related to the so-called Dirac cones on dispersion surfaces and to the directed anisotropy for the doubly periodic lattice. A comparative analysis accompanied by numerical simulation is carried out for the Floquet–Bloch waves propagating in periodic flexible lattices of different geometry
Rotational inertia interface in a dynamic lattice of flexural beams
No full textThe paper presents a novel analysis of a transmission problem for a network of flexural beams incorporating conventional Euler–Bernoulli beams as well as Rayleigh beams with the enhanced rotational inertia. Although, in the low-frequency regime, these beams have a similar dynamic response, we have demonstrated novel features which occur in the transmission at higher frequencies across the layer of the Rayleigh beams
Dispersion degeneracies and standing modes in flexural waves supported by Rayleigh beam structures
No full textThe paper presents a novel analysis of Floquet–Bloch flexural waves in a periodic lattice-like structure consisting of flexural beam ligaments. A special feature of this structure is in the presence of the rotational inertia, which is commonly neglected in conventional models of the Euler-Bernoulli type. The dispersion properties of the Rayleigh beam structure with rotational inertia include degeneracies linked to Dirac cones on the dispersion diagrams as well as directional anisotropy and special refraction properties. Steering of Dirac cones is described for rectangular flexural structures with a rotational inertia. Numerical examples for a forced network of Rayleigh and Euler–Bernoulli beams illustrate directional localisation, negative refraction, localisation at an interface and neutrality for propagating plane waves across a structured interface for a frequency range corresponding to a Dirac cone
Electro-chemo-mechanics of solid state batteries with lithium plating and stripping
Full text linkThis note is about a novel, thermodynamically consistent formulation for small strains continuum electro-chemo-mechanics applied to all solid state batteries, which are claimed to be the next-generation battery system in view of their safety accompanied by high energy densities. The response of a cell, made of a lithium metal foil, a solid electrolyte, and a porous LiCoO2 cathode, has been investigated in terms of quantities of interest such as the electric potential, the lithium concentrations profiles, displacements, and stresses. The plating and stripping of the lithium has been considered together with the volumetric evolution of the porous cathode. Together they contribute to the outbreak of mechanical stresses, which may influence the life cycle of a battery
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