Properties Of Representative Volume Element Research Articles

Structural analysis of small-scale 3D printed composite tidal turbine blades

The existing research literature lacks comprehensive investigations into assessing the structural performance of marine renewable energy conversion devices, particularly 3D printed turbine blades, which often rely solely on computational modelling without experimental validation methods and/or established mechanical characterization techniques. This leads to significant uncertainty regarding the performance of 3D printed turbine blades manufactured by additive manufacturing technology. This study aims to fill this gap by proposing a procedure for evaluating the structural integrity of commercial small-scale tidal turbine blade (5 KW) manufactured using fused filament fabrication 3D printing with a linear infill pattern. This is achieved by developing a combined experimental, hydrodynamic, and finite element approach with the view to inspect the micro-mechanical properties of representative volume elements of 3D printed microstructures using homogenization technique. The results of mechanical testing and hydrodynamic modelling are used to create a finite element model of the 3D printed blade, allowing for stress and failure analysis. Findings indicate that while integrating 3D printed materials into blade design via 3D printing technology is feasible, the choice of materials is limited to high stiffness composite filaments. Finally, experimental validation of numerical results, particularly full field strain distribution maps obtained by digital image correlation technique for flexural testing and laboratory-scale 3D printed blade, confirms the accuracy of the finite element results. Finite element-based homogenization techniques provide valuable insights into potential failure modes in 3D printed tidal turbine blades. However, the expedited calculation of orthotropic properties through finite element analysis proves to be a faster mechanical characterization method compared to experimental approaches. The proposed methodology in this study facilitates quicker iterative design of 3D printed blades, thereby reducing the need for repeated experiments and ultimately lowering manufacturing costs.

Application of Artificial Neural Networks to Numerical Homogenization of the Precast Hollow-Core Concrete Slabs

The main goal of this work is to combine the usage of the numerical homogenization technique for determining the effective properties of representative volume elements with artificial neural networks. The effective properties are defined according to the classical laminate theory. The purpose is to create and train a rapid surrogate model for the quick calculation of the mechanical properties of hollow concrete slabs. First, the homogenization algorithm was implemented, which determines membrane, bending and transverse shearing properties of a given parametrized hollow-core precast slab reinforced with steel bars. The algorithm uses the finite element mesh but does not require a formal solution of the finite element method problem. Second, the learning and training artificial intelligence framework was created and fed with a dataset obtained by optimal Latin hypercube sampling. In the study, a multilayer perceptron type of artificial neural network was used. This allows for obtaining rapid calculations of the effective properties of a particular hollow-core precast slab by using a surrogate model. In the paper, it has been proven that such a model, obtained via complex numerical calculations, gives a very accurate estimation of the properties and can be used in many practical tasks, such as optimization problems or computer-aided design decisions. Above all, the efficient setup of the artificial neural network has been sought and presented.

Identification of Variables and Determination of the Mechanism Affecting the Effective Properties of Representative Volume Elements of Unidirectionally Aligned CNT-Based Nanocomposites

This study identified the governing variables affecting the effective properties of the representative volume element (RVE) of nanocomposites consisting of unidirectionally aligned carbon nanotubes (CNTs) and determined the mechanism through which they act. For this purpose, multi-walled nanotubes (MWNTs) and polyvinylidene fluoride (PVDF) were selected as the components of the nanocomposites, and Monte Carlo simulations were conducted to examine the variability of the effective properties according to the CNT length. The governing variables affecting the effective properties were identified considering the conditions under which the selected CNTs can be arranged inside the RVE. Using the geometrical relationship between the RVE and CNTs, a simplified two-parameter equation that can calculate the effective properties of the RVE was derived. Using this equation and Monte Carlo simulations, this study confirmed that the characteristics of the effective properties vary with changes in the length of the RVE and the length fraction of the CNTs, and the mechanism of these changes was determined. In addition, the variation in the characteristics of the effective properties according to the coefficient of variation of the CNT length was also determined.

Impact resistance of short carbon fibre-carbon nanotube-polymer matrix hybrid composites: A stochastic multiscale approach

A multiscale approach is used here to investigate the impact properties of carbon fibre/carbon nanotube-reinforced polymer. For this purpose, the mechanical properties of the carbon nanotubes (CNTs) are obtained by molecular dynamics simulations. Then, they are included in the polyethene matrix, and the mechanical properties of CNT-reinforced polyethene are computed using a stochastic approach. Considering the CNT-reinforced polyethene as the matrix, the effect of adding the carbon fibres on its mechanical properties is investigated in the next step. Finally, utilizing a stochastic method, the macro-scale mechanical properties of carbon fibre/carbon nanotube-reinforced polymer are computed. Thereafter, the impact test is applied on the models. The finite element method is used to investigate the mechanical and impact properties of representative volume elements. The effects of waviness, volume percentage and aspect ratio of the carbon fibre and CNT on the mechanical properties of the multiscale composite are evaluated. It is shown that reinforcing the polyethene matrix by carbon fibres and CNTs significantly increases its impact resistance. Adding 3% and 5% volume percentages of CNT into 3%-carbon fibre/polyethene and 5%-carbon fibre/polyethene respectively, resulted in 26% and 47% improvement in the impact resistance of the composite.

A multilayer micromechanical model of the cuticle of Curculio longinasus Chittenden, 1927 (Coleoptera: Curculionidae).

Curculio longinasus Chittenden, 1927 (Coleoptera: Curculionidae), is a weevil species common throughout the southwestern United States that uses its rostrum - a very slender, curved, beak-like projection of the head - to excavate tunnels in plant organs (such as acorns) for egg laying (oviposition). Once the apical portion of the rostrum has been inserted into the preferred substrate for oviposition, the female begins rotating around the perimeter of the hole, elevating her head by extending the fore-legs, and rotating the head in place in a drilling motion. This action causes significant elastic deformation of the rostrum, which will bend until it becomes completely straight. To better understand the mechanical behavior of the cuticle as it undergoes deformation during the preparation of oviposition sites, we develop a comprehensive micro/macro model of the micromechanical structure and properties of the cuticle, spanning across all cuticular regions, and reliably mirroring the resultant macroscale properties of the cuticle. Our modeling approach relies on the use of multi-scale, hierarchical biomaterial representation, and employs various micromechanical schemata - e.g., Mori-Tanaka, effective field, and Maxwell - to calculate the homogenized properties of representative volume elements at each level in the hierarchy. We describe the configuration and behavior of this model in detail, and discuss the theoretical implications and limitations of this approach with emphasis on future biomechanical and comparative evolutionary research. Our detailed account of this approach can thereby serve as a methodological template for exploring the biomechanical behavior of new insect structures.

Four Phase Model: A New Formulation to Predict the Effective Elastic Moduli of Composites

We consider a linearly elastic composite medium, which consists of a homogeneous matrix containing coated spherical inclusions. The composite is modeled by a four phase pattern consisting of inclusion, interphase, matrix layer, and equivalent homogeneous medium. The overall elastic moduli are obtained using a micromechanical approach based on the Green function techniques and the interfacial operators. The four phase model assumes that all constituents are elastic and perfectly bonded. The model is used to derive the effective elastic properties of representative volume element using classical averaging schemes assuming the isotropy of constituent. Finally, effect of the thickness and stiffness of interphase on the global behavior of real composite materials are examined. Comparisons with experimental results show a good agreement.

A three-level hierarchical approach in modeling sheet thermoforming of knitted-fabric composites

A three-level hierarchical approach in modeling thermoforming process of curved-fabric-reinforced polymer sheet is presented in this paper. In the microscopic level, fiber bundle properties are analytically obtained from fiber filament and matrix material properties using simple rule-of-mixture approach. In the mesoscopic level, the representative volume element properties are obtained from the fiber bundle and matrix material properties using the mesoscopic mesh. Subsequent updating of mesoscopic nodal mesh coordinates and imposition of further strain gives the constitutive behavior of the composite material with due consideration to fabric reorientation, hence geometrical non-linearity. In the macroscopic level, the constitutive relationship, as a function of strain state, is applied to the macroscopic mesh whereby the material property of every macroscopic element is determined from the strain state resulting from the previous incremental plunger penetration and from the material database. Using the example of plain weft-knitted-fabric composites, both experimental and theoretical strain fields show reasonable agreement.

Orientation parameters for the specification of effective properties of heterogeneous materials

AbstractA general formulation is presented for the orientation averaging of the properties of representative volume elements of heterogeneous materials. Approximations are introduced that result in the identification of four independent orientation parameters that are required to specify a general state of three‐dimensional orientation. The general relationships are reduced further for the special case of “planar” and “axial” distribution and applied to an aggregate averaging scheme for short‐fiber composites.