International Journal of Engineering Science最新文献

The paper develops a new integral micromorphic elastic continuum model, which can describe dispersion properties of band-gap metamaterials, i.e., metamaterials that inhibit propagation of waves in a certain frequency range. The enrichment consists in nonlocal treatment of three terms in the expression for the potential energy density of the standard micromorphic continuum. After proper calibration, such a formulation can exactly reproduce two given branches of the dispersion curve (acoustic and optical), even in cases with a band gap. The calibration process exploits Fourier images of the unknown weight functions, which are analytically deduced from the dispersion relation of the material of interest. The weight functions are then reconstructed in the spatial domain by numerical evaluation of the inverse Fourier transform. The presented approach is validated on several examples, including discrete mass–spring chains with alternating masses, for which the dispersion relation has an explicit analytical form and the optical and acoustic branches are separated by a band gap.

The incorporation of ceramics into polymers, forming solid composite electrolytes (SCEs) leads to enhanced electrical performance of all-solid-state lithium metal batteries. This is because the dispersed ceramics particles increase the ionic conductivity, while the polymer matrix leads to better contact performance between the electrolyte and the electrode. In this study, we present a model, based on Hybrid Elements Methods, for the time-dependent Li metal and SCE rough interface mechanics, taking into account for the oxide (ceramics) inclusions (using the Equivalent Inclusion method), and the viscoelasticity of the matrix. We study the effect of LLTO particle size, weight concentration, and spatial distribution on the interface mechanical and electrical response. Moreover, considering the viscoelastic spectrum of a real PEO matrix, under a given stack pressure, we investigate the evolution over time of the mechanical and electrical performance of the interface. The presented theoretical/numerical model might be pivotal in tailoring the development of advanced solid state batteries with superior performance; indeed, we found that conditions in the SCE mixture which optimize both the contact resistivity and the interface stability in time.

The determination of surface elastic moduli is discussed in the context of a recently proposed strongly anisotropic surface elasticity model. The aim of the model was to describe deformations of solids with thin elastic coatings associated with so-called hyperbolic metasurfaces. These metasurfaces can exhibit a quite unusual behaviour and concurrently a very promising wave propagation behaviour. In the model of strongly anisotropic surface elasticity, strain energy as a function of the first and second deformation gradients has been introduced in addition to the constitutive relations in the bulk. In order to obtain values of surface elastic moduli, we compare dispersion relations for anti-plane surface waves obtained using the two-dimensional (2D) model and three-dimensional (3D) straightforward calculations for microstructured coatings of finite thickness. We show that with derived effective surface moduli, the 2D model can correctly describe the wave propagation.

Polylactic acid (PLA) nanofibrous networks have gained substantial interest across various engineering and scientific disciplines, such as tissue engineering, drug delivery, and filtration, due to their unique and multifunctional attributes, including biodegradability, tuneable mechanical properties, and surface functionality. However, predicting their mechanical behaviour remains challenging due to their structural complexity, multiscale features, and variability in material properties.

This study presents a hierarchical approach to investigate the fracture phenomena in both aligned and randomly oriented nanofibrous networks by integrating atomistic modelling and non-local continuum mechanics, peridynamics. At the nanoscale, all-atom molecular dynamics simulations are employed to apply tensile loads to freestanding pristine and silver-doped PLA nanofibres, where key mechanical properties such as Young's modulus, Poisson's ratio, and critical energy release rate are determined using innovative approaches. A new method is introduced to seamlessly transfer data from molecular dynamics to peridynamics by ensuring the convergence of the tensile response of a single fiber in both frameworks. This nano to micro coupling technique is then utilised to examine the Young's modulus, fracture toughness of mode I and II, and crack propagation in PLA nanofibrous networks. The proposed framework can also incorporate the effects of surface coating and fiber arrangements on the measured properties. The current research paves the way for the development of stronger and more durable eco-friendly nanofibrous networks with optimised performance.

The macroscopic behaviors of materials are determined by interactions that occur at multiple lengths and time scales. Depending on the application, describing, predicting, and understanding these behaviors may require models that rely on insights from atomic and electronic scales. In such cases, classical simplified approximations at those scales are insufficient, and quantum-based modeling is required. In this paper, we study how quantum effects can modify the mechanical properties of systems relevant to materials engineering. We base our study on a high-fidelity modeling framework that combines two computationally efficient models rooted in quantum first principles: Density Functional Tight Binding (DFTB) and many-body dispersion (MBD). The MBD model is applied to accurately describe non-covalent van der Waals interactions. Through various benchmark applications, we demonstrate the capabilities of this framework and the limitations of simplified modeling. We provide an open-source repository containing all codes, datasets, and examples presented in this work. This repository serves as a practical toolkit that we hope will support the development of future research in effective large-scale and multiscale modeling with quantum-mechanical fidelity.

Structural schemes of applicative interests in Engineering Science frequently encounter the intricate phenomenon of discontinuity. The present study intends to address the discontinuity in the flexure of elastic nanobeam by adopting an abstract variational scheme. The mixture unified gradient theory of elasticity is invoked to realize the size-effects at the ultra-small scale. The consistent form of the interface conditions, stemming from the established stationary variational principle, is meticulously set forth. The boundary-value problem of equilibrium is properly closed and the analytical solution of the transverse displacement field of the elastic nanobeam is addressed. As an alternative approach, the eigenfunction expansion method is also utilized to scrutinize the efficacy of the presented variational formulation in tackling the flexure of elastic nanobeams with discontinuity. The flexural characteristic of mixture unified gradient beams with diverse kinematic constraints is numerically illustrated and thoroughly discussed. The anticipated nanoscopic features of the characteristic length-scale parameters are confirmed. The demonstrated numerical results can advantageously serve as a benchmark for the analysis and design of pioneering ultra-sensitive nano-sensors. The established variationally consistent size-dependent framework paves the way ahead in nanomechanics and inspires further research contributing to fracture mechanics of ultra-small scale elastic beams.