Properties Of Related Materials Research Articles

Multi-scale fracture analysis of fibre-reinforced composites

Fibre reinforced composite (FRC) have been widely used in engineering applications for the purpose of strengthening or lightening of the structures. Many modern applications such as aircraft structures, automotive components, ships, yacht, and infrastructures etc. are fabricated by FRC materials. Since the FRC is the homogenized mixture of fibre and resin (matrix). The structural performance of the FRC materials depends on the fibre arrangement in the matrix, as well as FRC constituents. Therefore, an accurate prediction of structural response of this material needs prior information of micro to macro-level material properties. This paper presents a multi-scale numerical approach to predict the fracture response of fibre reinforced composites. At the micro-level, analysis of representative volume element (RVE) using DIGIMAT software has been presented to describe the microstructure related material properties. In this analysis, fibre is described as a linear elastic material while the matrix phase is modelled by an exponential linear law. The unknown constitutive relationship at the macro-scale has been obtained by DIGIMAT-FE analysis. Further, the macro-scale constitutive relation is used to predict fracture behaviour of FRC. Virtual crack closure technique (VCCT) of Finite Element Method has been implemented to study fracture parameters of FRC. All presented computational results are obtained by DIGIMAT-FE analysis and ABAQUS software. In order to check the robustness and accuracy of the presented approach, few benchmark problems were solved at the multi-scale level and compared with the reference results. In addition, edge crack and centre crack problems were solved by the multi-scale approach to analyse the fracture response of FRC.

Collective Strong Light-Matter Coupling in Hierarchical Microcavity-Plasmon-Exciton Systems.

Polaritons are compositional light-matter quasiparticles that arise as a result of strong coupling between the vacuum field of a resonant optical cavity and electronic excitations in quantum emitters. Reaching such a regime is often hard, as it requires materials possessing high oscillator strengths to interact with the relevant optical mode. Two-dimensional transition metal dichalcogenides (TMDCs) have recently emerged as promising candidates for realization of strong coupling regime at room temperature. However, these materials typically provide coupling strengths in the range of 10-40 meV, which may be insufficient for reaching strong coupling with low quality factor resonators. Here, we demonstrate a universal scheme that allows a straightforward realization of strong coupling with 2D materials and beyond. By intermixing plasmonic excitations in nanoparticle arrays with excitons in a WS2 monolayer inside a resonant metallic microcavity, we fabricate a hierarchical system with the collective microcavity-plasmon-exciton Rabi splitting exceeding ∼500 meV at room temperature. Photoluminescence measurements of the coupled systems show dominant emission from the lower polariton branch, indicating the participation of excitons in the coupling process. Strong coupling has been recently suggested to affect numerous optical- and material-related properties including chemical reactivity, exciton transport, and optical nonlinearities. With the universal scheme presented here, strong coupling across a wide spectral range is within easy reach and therefore exploration of these exciting phenomena can be further pursued in a much broader class of materials.

Wave propagation and pattern formation in two-dimensional hexagonally-packed granular crystals under various configurations

We study wave propagation in two-dimensional granular crystals under the Hertzian contact law consisting of hexagonal packings of spheres under various basin geometries including hexagonal, triangular, and circular basins which can be tiled with hexagons. We find that the basin geometry will influence wave reflection at the boundaries, as expected, and also may result in bottlenecks forming. While exterior strikers the size of a single sphere have been considered in the literature, it is also possible to consider strikers which impact multiple spheres along a boundary, or to have multiple sides being struck simultaneously. It is also possible to consider obstructions or even strikers in the interior of the hexagonally packed granular crystal, as previously considered in the case of square packings, resulting in the basin geometry no longer forming a convex set. We consider various configurations of either boundary or interior strikers. We shall also consider the case where a granular crystal is composed of two separate crystals of differing material, with a single interface between the two distinct materials. Depending on the relative material properties of each type of sphere, this can result in a trapping of most of the wave energy within one of the two regions. While repeated reflections from the boundaries will cause the systems we study to fall into disorder for large time, there are a number of interesting wave structures and patters that emerge as transients at intermediate timescales.

Simulation of crack propagation in prestressed concrete sleepers by fracture mechanics

Abstract Mode I crack propagation in prestressed concrete sleepers B70 is simulated by a fracture mechanics approach. The plastic damage model, which takes the non-linear behavior of concrete into account, is utilized to calculate crack length and crack mouth opening displacement (CMOD). Numerical data from prestressed concrete sleepers B70 under three-point bending load are compared with those of the proposed fracture mechanics model. In this study, fracture mechanics parameters of prestressed concrete sleepers are investigated. Sleepers with the length of initiation crack of 5 to 45 mm (with 10 mm steps) and the width of initiation crack of 2 to 8 mm (with 2 mm steps) are analyzed. Sleeper cracks are created in the notch and both of its sides. These analyses confirm that the structural behavior of prestressed concrete sleepers can be predicted by a simple fracture mechanics model provided that the related material properties like KIC, crack length and CMOD, are known.

Photoacoustic response of a transmission photoacoustic configuration for two-layer samples with thermal memory

In this paper, the models of surface temperature variations have been derived. Based on these models, photoacoustic (PA) response has been commented for transmission PA setup configurations of two-layer optically transparent samples, including the impact of finite heat propagation velocity through both layers (thermal memory) and the existence of volume absorption in both layers. By analyzing the derived model it has been shown that many parameters influence the photoacoustic response. Based on the derived model, some approximations have been discussed in order to enable the development of more accurate inverse solutions of photoacoustic problem, and the estimation of optical, thermal and other related physical properties of versatile materials. By using specific two-layer structure that consist of aluminum sample coated with layer of color dye, used in some photoacoustic experimental investigations, the influence of thermal memory properties of either the sample or the coating has been discussed.

Quenching of Infrared-Active Optical Phonons in Nanolayers of Crystalline Materials by Graphene Surface Plasmons

Optical phonons are fundamental excitations in many solid-state materials and have crucial influences on numerous material properties. Therefore, achieving extrinsic control of optical phonon properties, such as the phonon frequency, lifetime and population, may lead to new ways of tailoring various material properties relevant to key technological applications. Here, we experimentally demonstrate that infrared-active optical phonons in thin (tens of nm) layers of crystalline materials such as III–V semiconductors can be significantly quenched by a monolayer graphene. The optical phonon quenching effect is attributed to the ultrafast decay of optical phonons into resonant graphene surface plasmons at a rate which is significantly higher than the intrinsic decay rate of optical phonons due to lattice anharmonicity. Our results point to a new approach to engineering optical phonon properties and potentially other related material properties. Such an approach can be applied to a wide range of materials with ...

Single-crystal elastic properties of minerals and related materials with cubic symmetry

Single-crystal elastic properties of minerals and related materials with cubic symmetry

Formation of Gradient Micro-Porous Titanium-Aluminides Through Elemental Powder Metallurgy

The research into alloys, specifically titanium and aluminum alloys (Ti & Al), has rapidly growing technological importance. The combined research into Ti-Al alloys in the field of powder metallurgy has advanced the fabrication of a part with high compressive strength, low relative density and material properties in addition to being a cost-effective process. In this work Ti-Al alloys were created using elemental Ti and Al powders. Elemental powders with a melting point of over 1000°C were sintered via liquid phase sintering (LPS). LPS is a process used for forming high performance, multiple-phase components from powders. It involves sintering at a temperature between the melting points of the two powders. The structural morphology, pore size and location were evaluated using Scanning Electron Microscopy (SEM) and optical microscopy. These methods allowed visible evidence of structural anomalies providing a capillary action which pulled the liquid Al to the surface and resulted into a densification of the part at the surfaces. The dense structure was seen on both the top and bottom of the samples with a layer of predominantly Al. The average on the top surface layer using optical measurements was 0.48mm and the bottom was 0.97mm.

Permeate Flux in Ultrafiltration Membrane: A Review

Membrane processes exist for most of the fluid separations encountered in industry. The most widely used is membrane ultrafiltration, pressure driven process which is capable of separating particles in the approximate size range of 0.001 to 0.1 μm. The design of membrane separation processes, like all other processes, requires quantitative expressions relating material properties to separation performance. The factors controlling the performance of ultrafiltration are extensively reviewed. There have been a number of seminal approaches in this field. Most have been based on the rate limiting effects of the concentration polarization of the separated particles at the membrane surface. Various rigorous, empirical and intuitive models exist, which have been critically assessed in terms of their predictive capability and applicability. The decision as to which of the membrane filtration models is the most correct in predicting permeation rates is a matter of difficulty and appears to depend on the nature of the dispersion to separated.

Materials Properties for the Simulation of Electro-Chemo-Mechanical Coupling Behavior of SOFC

Research and development of solid oxide fuel cells (SOFCs) have been mainly conducted from the aspect of electrochemistry and materials science to improve cell- and stack performances. Long-term reliability and durability are of great importance for the commercialization of SOFCs. Mechanical behaviors of ceramics components, including cell fracture, are necessary to be understood in order to ensure stability of SOFCs. For the multiscale simulation of the thermo-chemo-mechanical behavior, various related materials properties are indispensable. This paper reports the evaluation procedure for comprehensive analysis of chemically- and thermally induced mechanical behavior of SOFCs.

The inferomedial femoral neck is compromised by age but not disease: Fracture toughness and the multifactorial mechanisms comprising reference point microindentation.

The influence of ageing on the fracture mechanics of cortical bone tissue is well documented, though little is known about if and how related material properties are further affected in two of the most prominent musculoskeletal diseases, osteoporosis and osteoarthritis (OA). The femoral neck, in close proximity to the most pertinent osteoporotic fracture site and near the hip joint affected by osteoarthritis, is a site of particular interest for investigation. We have recently shown that Reference Point micro-Indentation (RPI) detects differences between cortical bone from the femoral neck of healthy, osteoporotic fractured and osteoarthritic hip replacement patients. RPI is a new technique with potential for in vivo bone quality assessment. However, interpretation of RPI results is limited because the specific changes in bone properties with pathology are not well understood and, further, because it is not conclusive what properties are being assessed by RPI. Here, we investigate whether the differences previously detected between healthy and diseased cortical bone from the femoral neck might reflect changes in fracture toughness. Together with this, we investigate which additional properties are reflected in RPI measures. RPI (using the Biodent device) and fracture toughness tests were conducted on samples from the inferomedial neck of bone resected from donors with: OA (41 samples from 15 donors), osteoporosis (48 samples from 14 donors) and non age-matched cadaveric controls (37 samples from 10 donoros) with no history of bone disease. Further, a subset of indented samples were imaged using micro-computed tomography (3 osteoporotic and 4 control samples each from different donors) as well as fluorescence microscopy in combination with serial sectioning after basic fuchsin staining (7 osteoporotic and 5 control samples from 5 osteoporotic and 5 control donors). In this study, the bulk indentation and fracture resistance properties of the inferomedial femoral neck in osteoporotic fracture, severe OA and control bone were comparable (p > 0.05 for fracture properties and <10% difference for indentation) but fracture toughness reduced with advancing age (7.0% per decade, r = -0.36, p = 0.029). Further, RPI properties (in particular, the indentation distance increase, IDI) showed partial correlation with fracture toughness (r = -0.40, p = 0.023) or derived elastic modulus (r = -0.40, p = 0.023). Multimodal indent imaging revealed evidence of toughening mechanisms (i.e. crack deflection, bridging and microcracking), elastoplastic response (in terms of the non-conical imprint shape and presence of pile-up) and correlation of RPI with damage extent (up to r=0.79, p=0.034) and indent size (up to r=0.82, p<0.001). Therefore, crack resistance, deformation resistance and, additionally, micro-structure (porosity: r=0.93, p=0.002 as well as pore proximity: r = -0.55, p = 0.027 for correlation with IDI) are all contributory to RPI. Consequently, it becomes clear that RPI measures represent a multitude of properties, various aspects of bone quality, but are not necessarily strongly correlated to a single mechanical property. In addition, osteoporosis or osteoarthritis do not seem to further influence fracture toughness of the inferomedial femoral neck beyond natural ageing. Since bone is highly heterogeneous, whether this finding can be extended to the whole femoral neck or whether it also holds true for other femoral neck quadrants or other material properties remains to be shown.

Anomalous strain effect on the thermal conductivity of borophene: a reactive molecular dynamics study

Borophene, an atomically thin, corrugated, crystalline two-dimensional boron sheet, has been recently synthesized. Here we investigate mechanical properties and lattice thermal conductivity of borophene using reactive molecular dynamics simulations. We performed uniaxial tensile strain simulations at room temperature along in-plane directions, and found 2D elastic moduli of 188Nm−1 and 403Nm−1 along zigzag and armchair directions, respectively. This anisotropy is attributed to the buckling of the borophene structure along the zigzag direction. We also performed non-equilibrium molecular dynamics to calculate the lattice thermal conductivity. Considering its size-dependence, we predict room-temperature lattice thermal conductivities of 75.9 ± 5.0Wm−1K−1 and 147 ± 7.3Wm−1K−1, respectively, and estimate effective phonon mean free paths of 16.7 ± 1.7nm and 21.4 ± 1.0nm for the zigzag and armchair directions. In this case, the anisotropy is attributed to differences in the density of states of low-frequency phonons, with lower group velocities and possibly shorten phonon lifetimes along the zigzag direction. We also observe that when borophene is strained along the armchair direction there is a significant increase in thermal conductivity along that direction. Meanwhile, when the sample is strained along the zigzag direction there is a much smaller increase in thermal conductivity along that direction. For a strain of 8% along the armchair direction the thermal conductivity increases by a factor of 3.5 (250%), whereas for the same amount of strain along the zigzag direction the increase is only by a factor of 1.2 (20%). Our predictions are in agreement with recent first principles results, at a fraction of the computational cost. The simulations shall serve as a guide for experiments concerning mechanical and thermal properties of borophene and related 2D materials.

Dynamic solutions of mode III crack in copper matrix composites

By utilising the methods of the theory of complex variable functions, dynamic propagation problems on symmetrical mode III crack in copper matrix composite materials were analysed. The crack extension should also appear in the form of self-similarity because failure is ascertained by the maximum tensile stress in actual engineering structions and everyday applications occurring in usually dynamic conditions. The formulation and the development of a Riemann–Hilbert problem were involved in this kind of issue. According to self-similar functions, the queries considered in this paper can be very easily translated into a Riemann–Hilbert problem. Analytical solutions of stresses, displacements and dynamic stress intensity factors K 3(t) for the edges of symmetrical mode III crack, subjected to motive alterable loads, P x 5/t 5 and P t 6/x 5 were obtained. In view of the relative material properties, the changeable law of dynamic stress intensity factor was illustrated very well. After the solutions were applied by the use of the superposition principle, the solutions of discretionally complicated problems were easily acquired.

Materials Properties for the Simulation of Electro-Chemo-Mechanical Coupling Behavior of SOFC

Long-term reliability and durability are of great importance for the commercialization of SOFCs. Mechanical behaviors of ceramics components, including cell fracture, are necessary to be understood in order to ensure stability of SOFCs. For the multiscale simulation of the thermo-chemo-mechanical behavior, various related materials properties are indispensable. This paper reports the evaluation procedure of material properties for comprehensive analysis of chemically- and thermally induced mechanical behavior of SOFCs.

Material properties and their influence on the behaviour of tungsten as plasma facing material

With the aim of a possible improvement of the material specification for tungsten, five different tungsten products by different companies and by different production technologies (forging and rolling) are subject to a materials characterization program. Tungsten produced by forging results in an uniaxial elongated grain shape while rolled products have a plate like grain shape which has an influence on the mechanical properties of the material. The materials were investigated with respect to the following parameters: hardness measurements, microstructural investigations, tensile tests and recrystallisation sensitivity tests at 3 different temperatures. The obtained results show that different production processes have an influence on the resulting anisotropic microstructure and the related material properties of tungsten in the as-received state. Additionally, the recrystallization sensitivity varies between the different products, what could be a result of the different production processes. Additionally, two tungsten products were exposed to thermal shocks. The obtained results show that the improved recrystallisation behaviour has no major impact on the thermal shock performance.

Bio-inspired micro-to-nanoporous polymers with tunable stiffness.

Background: Inspired by structural hierarchies and the related excellent mechanical properties of biological materials, we created a smoothly graded micro- to nanoporous structure from a thermoplastic polymer.Results: The viscoelastic properties for the different pore sizes were investigated in the glassy regime by dynamic flat-punch indentation. Interestingly, the storage modulus was observed to increase with increasing pore-area fraction.Conclusion: This outcome appears counterintuitive at first sight, but can be rationalized by an increase of the pore wall thickness as determined by our quantitative analysis of the pore structure. Therefore, our approach represents a non-chemical way to tune the elastic properties and their local variation for a broad range of polymers by adjusting the pore size gradient.

Modified embedded-atom method interatomic potentials for Mg-Nd and Mg-Pb binary systems

Interatomic potentials for the Mg-Nd and Mg-Pb binary systems have been developed within the framework of the second nearest-neighbor modified embedded-atom method (2NN MEAM) formalism. The potentials describe a wide range of fundamental materials properties (thermodynamic, structural and elastic properties of compound and solution phases) of relevant systems in reasonable agreement with experimental data or first-principles and CALPHAD calculations. The applicability of the developed potentials to atomistic simulations on deformation behavior in Mg and its alloys is demonstrated by showing that the potentials reproduce related material properties reasonably and are transferable sufficiently.

Comparison of shrinkage related properties of various patch repair materials

A patch repair material has been developed in the form of unsaturated polyester resin (UPR)-mortar. The performance and durability of this material are governed by its compatibility with the concrete being repaired. One of the compatibility issue that should be tackled is the dimensional compatibility as a result of differential shrinkage between the repair material and the concrete substrate. This research aims to evaluate such shrinkage related properties of UPR-mortar and to compare with those of other patch repair materials. The investigation includes the following aspects: free shrinkage, resistance to delamination and cracking. The results indicate that UPR-mortar poses a lower free shrinkage, lower risk of both delamination and cracking tendency in comparison to other repair materials.

Variation of surface generation mechanisms in ultra-precision machining due to relative tool sharpness (RTS) and material properties

The need for ultra-fine surface generation by machining in micrometer and sub-micrometer scales is increasing rapidly for fabrication of micro products. However, there are limitations of bringing down the process from macro to micro to ultra-precision level due to the variation of the physical phenomenon responsible for surface generation process which is significantly dependent on tool edge radius. To analyse the tool edge radius effect, the governing process parameter identified as the ratio of undeformed chip thickness (a) to tool edge radius (r), which is known as relative tool sharpness, RTS (a/r). However, there are lacking of mathematical models to quantify the micro-mechanics of the material deformation during the surface generation process. In this study, a mathematical model has been established for the material removal mechanism with relation to edge radius effect. The novelty of this model lies in its ability to quantify the instantaneous material flow angle (φne) for a particular tool-workpiece combination with relative tool sharpness (RTS). The proposed model is able to capture the trend of the change of surface generation mechanism from shearing to extrusion to ploughing and rubbing. The transition of the deformation behaviour is predicted form the mathematical model and orthogonal cutting experiments were conducted for the validation of the results for two materials (Mg and Cu alloy). Under identical machining conditions, micro-chips and machined surface integrity of Cu and Mg alloy exhibited different characteristics. For the best nanometric finishing, the ‘extrusion-like’ machining zone is identified where the RTS value for Cu alloy is found smaller than that for Mg alloy. Hence, smaller grain material (Cu alloy, ~35µm) provides smaller RTS value than larger grain material (Mg alloy, ~126µm) for achieving superior surface finishing. Therefore, material properties play an important role for the relative tool sharpness (RTS) during the variation of high quality surface generation mechanism.

Effects of Aliovalent Anion Substitution on the Electronic Structures and Properties of ZnO and CdS

AbstractAliovalent anion substitution in ZnO, CdS, and related materials brings about drastic changes in their electronic structure and properties, making them colored, with a narrow band gap. Progressive substitution of N and F in ZnO leads to the formation of Zn2NF, with complete replacement of O with N and F. The band gaps of Zn2NF and O‐doped Zn2NF are smaller than the band gap in ZnO, because N 2p states create a new sub‐band above the valence band. Band‐edge energies of these compounds are thermodynamically favorable for water splitting. First‐principles calculations of P‐ and Cl‐substituted CdS and ZnS show the presence of a band just above the valence band, due to the p orbitals of the trivalent dopant, resulting in a noticeable reduction in the band gap of these materials. Such substitution of anions can be quite effective in engineering the valence band, and hence, in tuning the related properties of materials. Complete substitution of S with P and Cl in CdS should result Cd2PCl, but the resulting material is Cd2PCl1.5 or Cd4P2Cl3. Cd4P2Cl3 shows a band gap of 2.36 eV and a photoluminescence band at 580 nm. First‐principles calculations show it to be an effective photocatalyst for water splitting; it is shown experimentally to exhibit photocatalytic hydrogen evolution in the presence and absence of a sacrificial agent. Moreover, resilience to photocorrosion is a unique property of Cd4P2Cl3.