Publications
93 results found
Quino G, De Cola F, Tagarielli V, et al., 2019, Exploring the application of sound measurements to assess the structural integrity of fibre bundles, 25th International Conference on Fracture and Structural Integrity, Publisher: ELSEVIER SCIENCE BV, Pages: 507-515, ISSN: 2452-3216
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- Citations: 1
Pedrazzini S, Galano M, Audebert F, et al., 2018, High strain rate behaviour of Nano-quasicrystalline Al93Fe3Cr2Ti2 alloy and composites, Publisher: arXiv
In the present work, we demonstrate for the first time the outstandingdynamic mechanical properties of nano-quasicrystalline Al93Fe3Cr2Ti2 at.% alloyand composites. Unlike most crystalline aluminium-based alloys, this alloy andcomposites exhibit substantial strain rate sensitivity and retain much of theirductility at high rates of strain. This opens new pathways for use insafety-critical materials where impact resistance is required.
Song W, Tagarielli VL, Lee KY, 2018, Enhancing the fracture resistance and impact toughness of mechanically frothed epoxy foams with hollow elastomeric microspheres, Macromolecular Materials and Engineering, Vol: 303, ISSN: 1438-7492
Nonporous elastomeric particles are often employed to improve the toughness of brittle epoxy foams but this also decreases their compressive strength and stiffness. Herein, a novel strategy utilizing hollow elastomeric microspheres as toughening agent for epoxy foams is presented. The addition of 0.5 wt.% hollow elastomeric microspheres into epoxy foam leads to a 15% increase in critical stress intensity factor (K1c) to 0.38 MPa m0.5and 33% increase in Charpy impact strength (acU) to 1.05 kJ m−2, respectively, compared to unfilled epoxy foam (K1c = 0.33 MPa m0.5and acU= 0.79 kJ m−2). However, a further increase in the hollow elastomeric microsphere concentration to 1.0 wt.% leads to microsphere agglomeration, which reduces both K1cand acUto 0.35 MPa m0.5and 0.93 kJ m−2, respectively. Nevertheless, the added hollow elastomeric microspheres do not lead to a reduction in the quasi-static compressive properties of the epoxy foams.
Iliev S, Gommer F, Tagarielli V, 2018, Measurement of an indentation size effect for Indium as a function of temperature, Materials Science and Engineering: A, Vol: 733, Pages: 232-234, ISSN: 0921-5093
We present compression and instrumented indentation experiments on high-purity Indium, at temperatures from 22 to −100 °C. A strong indentation size effect is detected at all temperatures, corresponding to a large material length-scale. Therefore the large length-scale is not a consequence of creep mechanisms but an intrinsic property of the material.
Gauch H, Montomoli F, Tagarielli V, 2018, On the role of fluid-structure interaction on structural loading by pressure waves in air, Journal of Applied Mechanics, ISSN: 0021-8936
Quino G, Pellegrino A, Tagarielli VL, et al., 2018, Measurements of the effects of pure and salt water absorption on the rate-dependent response of an epoxy matrix, Composites Part B: Engineering, Vol: 146, Pages: 213-221, ISSN: 1359-8368
The study reports the measured effects of water absorption on an epoxy resin. Epoxy samples were exposed to wet conditioning environments including pure water, NaCl-water solution, and pure water at boiling temperature, measuring absorption as a function of time. Vickers hardness and indentation creep tests were performed and the mechanical response of the material to uniaxial stress was also measured in both compression and tension, at imposed strain rates in the range 0.001–2500 s−1. It was found that the absorption of both pure and salt water caused decrease of stiffness, yield stress and hardness, but only mildly affected the sensitivity of the response to the imposed strain rate and the tensile ductility. Mechanical testing after re-drying of the samples revealed the permanent effects of water absorption.
Zhou J, Tagarielli V, Heisserer U, et al., 2018, An apparatus for tensile testing of engineering materials, Experimental Mechanics, Vol: 58, Pages: 941-950, ISSN: 0014-4851
We develop a novel apparatus and an associatedtest protocol to measure the tensile response of materials. The apparatus allows testing of ring-shaped specimens,fibre yarns and tapes of arbitrary length; it can be employed to conduct experiments at different strain rates and in different environmental conditions.The technique is tested at low rates of strain on several materials, including carbon fibres, metals, polymers and ceramics; the tensile responses measured with the new apparatus are compared to those obtained from conventional measurements and found to be in good agreement with these.
Tagarielli V, Matos MAS, Pinho S, et al., 2018, Predictions of the electro-mechanical response of conductive CNT-polymer composites, Journal of the Mechanics and Physics of Solids, Vol: 114, Pages: 84-96, ISSN: 0022-5096
We present finite element simulations to predict the conductivity, elastic response and strain-sensing capability of conductive composites comprising a polymeric matrix and carbon nanotubes. Realistic representative volume elements (RVE) of the microstructure are generated and both constituents are modelled as linear elastic solids, with resistivity independent of strain; the electrical contact between nanotubes is represented by a new element which accounts for quantum tunnelling effects and captures the sensitivity of conductivity to separation. Monte Carlo simulations are conducted and the sensitivity of the predictions to RVE size is explored. Predictions of modulus and conductivity are found in good agreement with published results. The strain-sensing capability of the material is explored for multiaxial strain states.
Pathan M, Patsias S, Tagarielli V, 2018, A real-coded GA algorithm for optimizing the damping response of composite laminates, Computers and Structures, Vol: 198, Pages: 51-60, ISSN: 0045-7949
We develop a real-coded constrained genetic algorithm (GA) and assessits performance in selected classical optimisation problems. The proposed GA uses a roulette selection method, BLX-α crossover operation, non-uniform mutation along with single elitist selectionat every generation. The GA is then applied, in conjunction with the finite element (FE) method, to optimise the damping response of a laminate comprising unidirectional composite laminae and viscoelastic damping layers. Modal loss factors are maximised against the constraints of given structural stiffness and mass.
Tagarielli V, gauch HL, montomoli F, 2018, The response of an elastic-plastic clamped beam to transverse pressure loading, International Journal of Impact Engineering, Vol: 112, Pages: 30-40, ISSN: 0734-743X
This study presents a new analytical model to predict the response of elastic-plastic, fully clamped beams to transverse pressure loading. The model accounts for travelling elastic flexural waves, stationary and travelling plastic hinges, elastic-plastic stretching and plastic shear deformation. The predictions of the model are validated by detailed Finite Element simulations. The model is used to construct deformation mechanism maps and design charts.
Pathan MV, Patsias S, Rongong J, et al., 2017, Measurements and predictions of the viscoelastic properties of a composite lamina and their sensitivity to temperature and frequency, Composites Science and Technology, Vol: 149, Pages: 207-219, ISSN: 0266-3538
We perform finite element analysis of the mechanical response of random RVEs representing the microstructure of a unidirectional (UD) fibre composite, predicting its anisotropic stiffness and damping properties and their sensitivity to temperature and frequency, using as inputs only the measured response of the constituents. The simulations are validated by DMTA measurements on a UD composite; then, the numerical predictions are compared to those of previously published theoretical models. New equations are proposed to predict the viscoelastic constants, providing better accuracy than existing models. The accuracy of these new equations is tested, over wide ranges of fibre volume fractions and stiffness ratios of the constituents, against the numerical predictions.
Matos MAS, Tagarielli VL, Pinho ST, 2017, Simulation of the electromechanical repsonse of self-sensing carbon nanotube polymer nanocomposites, 21st International Conference on Composite Materials
© 2017 International Committee on Composite Materials. All rights reserved. A novel finite element approach to simulate the electromechanical properties and strain sensing capabilities of carbon nanotube polymer composites is presented. The models capture the nanoscale tunneling effect and its sensitivity to the imposed strain field. The approach is based on mechanical and electrical simulations of a representative volume element constructed based on measurable statistical descriptors of the microstructure. 2D and 3D approaches are described and resulting homogenized properties compared. Predictions are found in good agreement with previously published data.
Tagarielli V, song Y, li Y, et al., 2017, Measurements of the mechanical response of unidirectional 3D-printed PLA, Materials & Design, Vol: 123, Pages: 154-164, ISSN: 0261-3069
Fully dense PLA blocks were manufactured by 3D-printing, depositing a polymer filament in a single direction via the fusion deposition method (FDM). Specimens were cut from printed blocks using conventional machining and were used to perform tension, compression and fracture experiments along different material directions. The elasto-plastic material response was found to be orthotropic and characterised by a strong tension-compression asymmetry; the material was tougher when loaded in the extrusion direction than in the transverse direction. The response of the unidirectional, 3D-printed material was compared to that of homogeneous injection-moulded PLA, showing that manufacturing by 3D-printing improves toughness; the effects of an annealing thermal cycle on the molecular structure and the mechanical response of the material were assessed.
Schiffer A, Gardner M, Lynn R, et al., 2017, A new apparatus to induce lysis of planktonic microbial cells by shock compression, cavitation and spray, Royal Society Open Science, Vol: 4, ISSN: 2054-5703
Experiments were conducted on an aqueous growth medium containing cultures of Escherichia coli(E. coli)XL1-Blue,to investigate, in a single experiment, the effect of twotypes of dynamic mechanical loading on cellular integrity. A bespoke shock tube was used to subject separate portions of a planktonic bacterial culture totwo different loading sequences: (i) shock compression followed by cavitation, and (ii) shock compression followed by spray. The apparatus allowsthe generation ofan adjustable loading shockwave ofmagnitude up to 300MPa in a sterile laboratory environment. Cultures of E. coliwere tested with this apparatus and the spread-plate technique was used to measure the survivabilityafter mechanical loading.Theloading sequence (ii) gave higher mortality than (i), suggesting that thebacteria aremore vulnerableto shear deformation and cavitation than to hydrostaticcompression. We present results of preliminary experiments and suggestions for further experimental work; we discuss the potential applications of this technique to sterilise large volumes of fluid samples.
Zacharopoulos P, Tagarielli VL, 2017, Numerical modelling of the mechanical response of cellular solids made from sintered Titanium powders, International Journal of Solids and Structures, Vol: 113, Pages: 241-254, ISSN: 1879-2146
Two algorithms are developed to generate virtual microstructures of Titanium foams of medium relative density, in the range 0.37 – 0.48; one of the algorithms captures the effect of pore shape and size distribution, while the other algorithm only accounts for the relative density of the material. Foams are modelled as two-phase composites consisting of a solid material and voids; the elasto-plastic and damage response of the parent material is deduced from its measured mechanical responses in tension and compression, while the material occupying the voids is assigned a plastically compressible constitutive response, to mimic the effects of pore collapse and subsequent self-contact. Finite Element (FE) simulations are conducted to predict the measured macroscopic material response in uniaxial tension and compression, as well as in pure shear; a mesh convergence study is performed and the minimum RVE size is determined. The simulations are found in good agreement with measurements and can predict accurately and effectively the material's mechanical response up to large strains, as well as the scaling of mechanical properties with relative density.
Schiffer A, Tagarielli V, 2017, Observations and Numerical Modeling of the Response of Composite Plates to Underwater Blast, EXPLOSION BLAST RESPONSE OF COMPOSITES, Editors: Mouritz, Rajapakse, Publisher: WOODHEAD PUBL LTD, Pages: 233-263, ISBN: 978-0-08-102092-0
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Iliev S, Chen X, Pathan MV, et al., 2016, Measurements of the mechanical response of Indium and of its size dependence in bending and indentation, Materials Science and Engineering A: Structural Materials: Properties, Microstructure and Processing, Vol: 683, Pages: 244-251, ISSN: 1873-4936
Tension, compression, three-point bending and indentation experiments are conductedon high purity Indium at room temperature and low strain rates. The material displays a ductile viscoplastic response, found to be size-independent in tension and compression. Simple analytical models are constructed to aid interpretation of the test resultsand detection of a size effect in bending and indentation, associated to a length-scale of order 50-100μm.
Schiffer A, Tagarielli VL, 2016, Underwater blast loading of water-backed sandwich plates with elastic cores: theoretical modelling and simulations, International Journal of Impact Engineering, Vol: 102, Pages: 62-73, ISSN: 1879-3509
Analytical predictions and finite element (FE) calculations are performed to predict the 1D response to underwater blast loading of sandwich plates with elastic cores, in contact with water on both sides and loaded by an exponentially decaying shock wave on one side. The theoretical models explicitly account for cavitation processes and effects of deep water, and their formulation helps identifying the governing parameters of the problem. Three characteristic regimes of behaviour are identified and regime maps are constructed. The analytical models are validated by FE simulations and used to explore the sensitivity of the predictions to the governing non-dimensional parameters. It is shown that, in the absence of plastic core deformation, sandwich plates with stiff cores are imparted higher blast impulses compared to those with softer cores and equivalent areal mass.
Pathan MV, Tagarielli VL, SPatsias, 2016, Effect of fibre shape and interphase on the anisotropic viscoelastic response of fibre composites, Composite Structures, Vol: 162, Pages: 156-163, ISSN: 1879-1085
We perform Monte Carlo analyses of the anisotropic viscoelastic response of random RVEs representing the microstructure of UD fibre composites. Both fibres and matrix are taken as isotropic viscoelastic solids; the fibres have different cross-sections including circular, elliptical, Reauleaux and star-shaped; they are separated from the matrix by interphase regions of different mechanical properties and thicknesses. The analyses allow determining the sensitivity of the transversely isotropic, viscoelastic response of UD composites to fibre volume fraction, fibre shape, interphase volume fraction and interphase properties.
Pathan MV, Tagarielli VL, Patsias S, et al., 2016, A new algorithm to generate representative volume elements of composites with cylindrical or spherical fillers, Composites Part B - Engineering, Vol: 110, Pages: 267-278, ISSN: 1359-8368
A new algorithm to generate random spatial distributions of cylindrical fibres and spheres is developed based on a constrained optimization formulation. All filler particles are generated simultaneously within the specimen domain; subsequently their position is iteratively perturbed to remove particle overlapping. The algorithm is able to achieve volume fractions of up to 0.8 in the case of circular cylindrical fibres of equal diameter; the method can be applied to any statistical distribution of fibre diameters. The spatial distribution of fibres and spheres is analysed by plotting spatial statistical metrics; it is shown that the microstructures generated are spatially random and similar to those observed in real fibre composites. The algorithm is employed to effectively predict the transversely isotropic elastic, damping and plastic properties of a unidirectional fibre composite by analysis of an RVE of smaller size than previously reported.
Pathan MV, Tagarielli VL, Patsias S, 2016, Numerical predictions of the anisotropic viscoelastic response of uni-directional fibre composites, Composites Part A: Applied Science and Manufacturing, Vol: 93, Pages: 18-32, ISSN: 1359-835X
Finite Element (FE) simulations are conducted to predict the viscoelastic properties of uni-directional (UD) fibre composites. The response of both periodic unit cells and random stochastic volume elements (SVEs) is analysed; the fibres are assumed to behave as linear elastic isotropic solids while the matrix is taken as a linear viscoelastic solid. Monte Carlo analyses are conducted to determine the probability distributions of all viscoelastic properties. Simulations are conducted on SVEs of increasing size in order to determine the suitable size of a representative volume element (RVE). The predictions of the FE simulations are compared to those of existing theories and it is found that the Mori-Tanaka (1973) and Lielens (1999) models are the most effective in predicting the anisotropic viscoelastic response of the RVE.
Siegkas P, Petrinic N, Tagarielli V, 2016, Measurements and Micro-Mechanical Modelling of the Response of Sintered Titanium Foams, Journal of the Mechanical Behavior of Biomedical Materials, Vol: 57, Pages: 365-375, ISSN: 1751-6161
Titanium foams of relative density in the range 0.35–0.50 are tested in quasi-static compression, tension and shear. The response is ductile in compression but brittle, and weaker, in shear and tension. Virtual foam microstructures are generated by an algorithm based on Voronoi tessellation of three-dimensional space, capable of reproducing the measured size distribution of the pores in the foam. Finite Element (FE) simulations are conducted to explore the mechanical response of the material, by analysing the elasto-plastic response of a statistical volume element (SVE). The simulations correctly predict the ductile compressive response and its dependence on relative density.
Tagarielli V, schiffer A, 2016, 10 - The response to underwater blast, Dynamic Deformation, Damage and Fracture in Composite Materials and Structures, Publisher: Woodhead Publishing, ISBN: 9780081000830
As the mechanical behavior and performance of composites varies under different dynamic loading regimes and velocities, the book is divided into sections that examine the different loading regimes and velocities.
Matos MAS, Tagarielli VL, Pinho ST, 2016, Simulation of the electromechanical properties of carbon nanotube polymer nanocomposites for strain sensing
We present a Finite Element (FE) approach to model the conductivity and strain-sensing capabilities of Carbon Nanotube (CNT) reinforced polymer composites. A periodic Representative Volume Element (RVE) is constructed based on measurable statistical descriptors of the microstructure, and its response is simulated by concurrent electrical and mechanical FE analyses; the scatter of the predictions and their sensitivity to RVE size are explored. The model captures the nanoscale tunneling effect and its sensitivity to the imposed strain field. Predictions are found in good agreement with previously published data.
Schiffer A, Tagarielli VL, 2015, Predictions of the interlaminar tensile failure of a carbon/epoxy composite laminate, Composite Structures, Vol: 133, Pages: 997-1008, ISSN: 1879-1085
Finite element calculations are performed to model failure of a carbon/epoxy composite laminate loaded in tension in the through-thickness direction, and to predict the dependence of failure loads upon specimen size. The spatial variability of the inter-laminar strength is modelled by introducing different types of discrete random fields of material tensile strength. Fracture processes are modelled using the cohesive segment method, within the extended finite element framework of ABAQUS Standard. Monte Carlo Simulation are conducted on different realisations of the random fields; the predicted responses are compared to previously published measurements and to reference FE simulations, in which the material strength is taken as uniform and equal to the measured average. The comparison shows that the modelling approach presented here provides more accurate predictions of the structural failure loads and their dependence on size, as well as capturing the failure modes observed in experiments.
Schiffer A, Cantwell WJ, Tagarielli VL, 2015, An analytical model of the dynamic response of circular composite plates to high-velocity impact, International Journal of Impact Engineering, Vol: 85, Pages: 67-82, ISSN: 1879-3509
Analytical models are developed to predict the transient elastic response of fully clamped circular composite plates subject to high-velocity impact by a rigid spherical projectile. The models are based on first-order shear deformation plate theory and account for the effects of large deformations as well as propagation and reflection of flexural waves. Analytical predictions of plate deflection history and peak strain in the plates are found in good agreement with those obtained from detailed explicit FE simulations. The dynamic response is found to be governed by four non-dimensional parameters and two characteristic regimes of behaviour are identified. The models are used to construct maps to design impact-resistant composite plates.
Schiffer A, Tagarielli VL, 2015, IMPACT BEHAVIOUR OF COMPOSITE PLATES SUBJECT TO HIGH-VELOCITY IMPACT BY RIGID PROJECTILES: ANALYTICAL MODELLING OF THE ELASTIC RESPONSE, 20th International Conference on Composite Materials (ICCM), Publisher: AALBORG UNIV PRESS
Schiffer A, Tagarielli VL, 2014, The response of circular composite plates to underwater blast: Experiments and modelling, Journal of Fluids and Structures, Vol: 52, Pages: 130-144, ISSN: 1095-8622
We present a new experimental technique to allow laboratory-scale observation of underwater blast loading on circular plates, including dynamic deformation and failure of the plates as well as the sequence of cavitation events in water. The apparatus is used to measure and compare the responses of a quasi-isotropic glass/vinylester composite and of a woven carbon/epoxy plate. Dynamic explicit FE simulations are conducted and their predictions are found in good agreement with experiments. Measurements and FE predictions are used to validate a recently developed theoretical model for the response of elastic orthotropic plates to underwater blast.
Pellegrino A, Tagarielli VL, Gerlach R, et al., 2014, The mechanical response of a syntactic polyurethane foam at low and high rates of strain, International Journal of Impact Engineering, Vol: 75, Pages: 214-221, ISSN: 1879-3509
Quasi-static and dynamic experiments are conducted to characterise the mechanical response of a syntactic foam comprising hollow glass microballoons in a polyurethane matrix. Stress versus strain histories are measured in uniaxial tension and compression as well as in pure shear, at strain rates ranging from 10−4 to 103 s−1, via non-standard experimental techniques; quasi-static in-situ tests are conducted to visualise the deformation mechanisms in tension and compression. The material displays a pronounced sensitivity to the imposed strain rate and relatively high tensile and shear ductility at both low and high strain rates. A tension/compression asymmetry is displayed in quasi-static tests but is lost at high rates of strain.
Siegkas P, Tagarielli V, Petrinic N, 2014, Modelling stochastic foam geometries for FE simulations using 3D Voronoi cells, Procedia Materials Science, Vol: 4, Pages: 221-226
A method for generating realistic foam geometries is developed for modelling the structure of stochastic foams. The method employs 3D Voronoi cells as pores. The virtual geometries are subjected to loading with the use of finite element methods and the results are compared to experimental data for open cell Titanium foams. The method applies statistical control to geometrical characteristics and it's used to either replicate or virtually generate prototype foam structures.
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