Individual Material Properties Research Articles

(Invited, Digital Presentation) Multiscale Measurements and Characterization of Thermal Transport in Materials and across Interfaces in Li-Ion Cells

Li-ion cells are used universally for energy conversion and storage. Key application areas include electric vehicles, grid energy storage, air/space vehicles and consumer electronics. Overheating of Li-ion cells is a well-known problem, with serious concerns related to thermal runaway and fire. Additionally, Li-ion cells also under-perform at low temperatures, which is a particularly important problem for automotive and space applications. Advances in battery materials are needed to mitigate these concerns and improve the performance and safety of Li-ion cells. This talk will summarize research advances in understanding and optimizing thermal transport in Li-ion cell and battery pack materials. Measurement of thermal conductivity of cylindrical Li-ion cells, indicating the highly anisotropic nature of thermal conduction will be described. This will be followed by discussion of measurement of thermal properties of individual cell materials, such as the separator, as well as thermal contact resistance at the cathode-separator interface. This contact resistance will be shown to play a rate-limiting role in determining overall thermal transport properties of the cell, and is, in particular, responsible for anisotropic thermal conduction. Experiments to mitigate this thermal resistance through molecular bridging at the interface will be described. Good agreement with molecular dynamics simulations will be demonstrated. Challenges associated with practical implementation of such techniques will be discussed. Finally, numerical simulations to understand the nature of thermal transport in battery packs will be described, with the goal of minimizing thermal runaway propagation. These measurements and modeling techniques contribute towards a fundamental understanding of multiscale thermal transport in Li-ion cell materials, and may help optimize and improve thermal performance of practical energy conversion and storage devices.

Decoupling the role of chemistry and microstructure in hMSCs response to an osteoinductive calcium phosphate ceramic.

Calcium phosphates (CaP) are widely used synthetic bone graft substitutes, having bioactivity that is regulated by a set of intertwined physico-chemical and structural properties. While some CaPs have shown to be as effective in regenerating large bone defects as autologous bone, there is still the need to understand the role of individual material properties in CaP performance. Here, we aimed to decouple the effects of chemical composition and surface-microstructure of a beta-tricalcium phosphate (TCP) ceramic, with proven osteoinductive potential, on human mesenchymal stromal cells (hMSCs) differentiation. To this end, we replicated the surface structure of the TCP ceramic into polylactic acid without inorganic additives, or containing the chemical constituents of the ceramic, i.e., a calcium salt, a phosphate salt, or TCP powder. The microstructure of the different materials was characterized by confocal laser profilometry. hMSCs were cultured on the materials, and the expression of a set of osteogenic genes was determined. The cell culture medium was collected and the levels of calcium and phosphate ions were quantified by inductively-coupled plasma mass spectrometry. The results revealed that none of the tested combinations of properties in polymer/composite replicas was as potent in supporting the osteogenic differentiation of hMSCs as the original ceramic. Nevertheless, we observed some effects of the surface structure in the absence of inorganics, as well as combined effects of surface structure and the added salts, in particular calcium, on osteogenic differentiation. The approach presented here can be used to study the role of independent properties in other CaP-based biomaterials.

Enhanced valley splitting of WSe2 in twisted van der Waals WSe2/CrI3 heterostructures

Van der Waals (vdW) heterostructures composed of different two-dimensional (2D) materials offer an easily accessible way to combine properties of individual materials for applications. Owing to the discovery of a set of unanticipated physical phenomena, the twisted 2D vdW heterostructures have gained considerable attention recently. Here, we report enhanced valley splitting in twisted 2D vdW WSe2/CrI3 heterostructures. In particular, the splitting can be 1200% (or 5.18 meV) of the value for a non-twisted heterostructure. According to the k·p model, this value is equivalent to a ~20 T external magnetic field applied perpendicular to the 2D sheet. The thermodynamic stability of 2D vdW WSe2/CrI3 heterostructures, on the other hand, depends linearly on the interlayer twisting angle.

Promoted photocarrier separation by dipole engineering in two-dimensional perovskite/C2N van der Waals heterostructures.

Due to the aggravation of environmental pollution and the energy crisis, it is urgent to develop and design environment-friendly and efficient photocatalysts for water splitting. van der Waals heterostructures composed of different two-dimensional materials offer an easily accessible way to combine properties of individual materials for applications. Herein, a novel Cs3Bi2I9/C2N heterostructure is proposed through first-principles calculations. The structural, electronic, and optical properties, as well as the charge transfer mechanism at the interface of Cs3Bi2I9/C2N are systematically investigated. Due to the difference between the work functions of Cs3Bi2I9 and C2N monolayers, when they are constructed into heterostructures, redistribution of charge occurs in the whole structure, and some of the charge transfer occurs at the interface due to the formation of an internal electric field. The band structure of Cs3Bi2I9/C2N has type-II band alignment, and the band edge position as well as the band-gap value of the heterostructure are suitable for visible light water splitting. The in-plane biaxial strain, interfacial spacing, and external electric field can effectively modulate the electronic structure and photocatalytic performance of the heterostructure. Under certain conditions, the heterostructure can be changed from type-II to type-I band alignment, accompanied by the transition from an indirect band-gap semiconductor to a direct band-gap semiconductor. Moreover, the intrinsic anion defect (I vacancy) at different positions, as donor defects, can introduce defect levels near the conduction band edge, which affects the transition of photogenerated carriers in these systems. Our findings provide a theoretical design for strategies to improve the performance of two-dimensional perovskites/C2N in photocatalytic and optoelectronic applications.

Environmental Durability of an Optical Fiber Cable Intended for Distributed Strain Measurements in Concrete Structures.

The present study investigates the environmental durability of a distributed optical fiber sensing (DOFS) cable on the market, commonly used for distributed strain measurements in reinforced concrete structures. An extensive experimental program was conducted on different types of specimens (including samples of bare DOFS cable and plain concrete specimens instrumented with this DOFS cable) that were exposed to accelerated and natural ageing (NA) conditions for different periods of up to 18 months. The instrumentation of both concrete specimens consisted of DOFS cables embedded at the center of the specimens and bonded at the concrete surface, as these two configurations are commonly deployed in the field. In these configurations, the alkalinity of the surrounding cement medium and the outdoor conditions are the main factors potentially affecting the characteristics of the DOFS component materials and the integrity of the various interfaces, and hence impacting the strain transfer process between the host structure and the core optical fiber (OF). Therefore, immersion in an alkaline solution at an elevated temperature or freeze/thaw (F/T) and immersion/drying (I/D) cycles were chosen as accelerated ageing conditions, depending on the considered configuration. Mechanical characterizations by tensile and pull-out tests were then carried out on the exposed specimens to assess the evolution of the mechanical properties of individual component materials as well as the evolution of bond properties at various interfaces (internal interfaces of the DOFS cable, and interface between the cable and the host structure) during ageing. Complementary physico-chemical characterizations were also performed to better understand the underlying degradation processes. The experimental results highlight that immersion in the alkaline solution induced a significant and rapid decrease in the bond properties at internal interfaces of the DOFS cable and at the cable/concrete interface (in the case of the embedded cable configuration), which was assigned to chemical degradation at the surface of the cable coating in contact with the solution (hydrolysis and thermal degradation of the EVA copolymer component). Meanwhile, F/T and I/D cycles showed more limited effects on the mechanical properties of the component materials and interfaces in the case of the bonded cable configuration. A comparison with the same specimens exposed to outdoor NA suggested that the chosen accelerated ageing conditions may not be totally representative of actual service conditions, but provided indications for improving the ageing protocols in future research. In the last part, an analysis of the distributed strain profiles collected during pull-out tests on instrumented concrete specimens clearly illustrated the consequences of ageing processes on the strain response of the DOFS cable.

Dimensionally engineered ternary nanocomposite of reduced graphene oxide/multiwalled carbon nanotubes/zirconium oxide for supercapacitors

Three dimensional (3D) hybrid nanoarchitecture of two-dimensional (2D) reduced graphene oxide/one dimensional (1D) multiwalled carbon nanotube and zero-dimensional (0D) zirconium oxide (ZrO2) nanoparticles (rGO/MWCNT/ZrO2) was synthesised by a simple hydrolysis method for high performance supercapacitors. To unlock the properties of individual materials to the maximum, binaries of ZrO2 with GO and MWCNT were also synthesised. The increased wettability, integrated structure, and the synergistic effect of rGO, MWCNT, and ZrO2 in rGO/MWCNT/ZrO2 (GMZ) offer a capacitance of 357 F g−1 at 1 A g−1 with excellent capacitance retention of 98% across 5000 cycles. 1D structure of MWCNT creates an exceptional conductive network with rGO due to the confinement of electrons and ions without disturbing its electronic structure. The intriguing supercapacitor performance of differently dimensioned framework with ZrO2 emphasises the engineered orientation and tuning of a designed environment for its appropriateness, uniqueness, and sensitivity to push up enhanced performance.

Synergy Effects in Blended Electrodes for Li‐ion Batteries: A Conceptual Clarification

AbstractThe use of electrodes with multiple active materials is considered a promising approach to develop advanced Li‐ion batteries. Recent studies even point to synergistic effects in terms of rate performance. However, the origin of synergistic effects is still insufficiently understood to enable targeted material and design development and to optimize batteries accordingly. Using straightforward equivalent circuit modeling combined with electrochemical studies, we reveal that improvements in rate capability are an intrinsic property of blended electrodes. The electrical parallel connection of the components in the composite electrode allows the applied current to be distributed among the components in a way that the voltage losses become minimal. This way, rate‐limiting components can still contribute to the electrode's capacity at high loads, which makes blended electrodes particularly attractive, e. g., for applications that must be able to handle high pulse loads. Based on the results, rational design principle are derived by means of a systematic sensitivity analysis, quantifying the influence of the individual active material properties. These findings greatly contribute to the understanding of the internal dynamics and synergy effects in blended electrodes and support the targeted development of advantageous material combinations and electrode designs for future Li‐ion batteries.

Broadband photodetector based on ReS2/graphene/WSe2 heterostructure

Two-dimensional van der Waals heterostructures can combine properties of individual materials to enable high-performance photodetection. Here, a novel ReS2/graphene/WSe2 heterostructure, prepared by dry transfer, demonstrates air-stable, high-performance, polarization-sensitive, and broadband photodetection. Dark current can be strongly suppressed by the built-in electric field of the heterostructure. The specific detectivities are up to 1010 Jones and 109 Jones under zero and reverse bias, respectively. Response time is on the order of a millisecond. The polarization-sensitive photodetection has been observed in the heterostructure due to the low lattice symmetry of ReS2. Broadband photoresponse from visible to infrared range has been demonstrated. A high photoresponsivity of 1.02 A W−1 is achieved for illumination at the wavelength of 785 nm. This work provides a viable approach toward future high-performance, air-stable, and polarization-sensitive broadband photodetectors.

On the stress analysis around a nanoinhomogeneity embedded in a half-space with the account of Steigmann–Ogden interface effects

This paper examines the interface elasticity between an elastic half-space and a spherical nanoinhomogeneity subjected to a unidirectional far-field tension that is parallel to the half-space plane boundary. The spherical interface is modeled by the full version of Steigmann–Ogden interface theory. Due to their marginal significance, the effects of half-space plane boundary are neglected. The problem is solved by decomposing the unidirectional load into an all-around and an equal-but-opposite traction field. Benefitting from the property of axial symmetry, the former subproblem is solved by the sole use of Boussinesq displacement potentials. The latter condition is addressed by six harmonic functions extracting from Boussinesq, Papkovich–Neuber and Dougall displacement potentials. The relations between cylindrical and spherical harmonic functions are employed to clear the tractions along the half-space plane boundary and to satisfy the nonclassical traction equilibrium conditions across the matrix/nanoinhomogeneity interface. Truncating the resultant infinite series and equating the coefficients preceding Legendre polynomials, associated Legendre functions as well as their derivatives lead to a system of algebraic equations with respect to the dimensionless unknown parameters in displacement potentials. Extensive parametric studies are further performed in order to analyze the importance of interface tension, interface Lamé constants, interface flexural rigidities, shear moduli ratio and nanoinhomogeneity radius-to-depth ratio on stress distributions and stress concentrations. Comparisons against both the classical and the Gurtin–Murdoch solutions help to clarify the separate effects of individual interface material properties. Stresses inside a soft nanoinhomogeneity is most affected by the additional incorporation of interface flexural rigidities. In addition, the deviatoric component of the interface curvature change tensor is found to be more important than the mean part for the proposed nanoinhomogeneity problem.

The generalized periodic boundary condition for microscopic simulations of heat transfer in heterogeneous materials

Porous and composite materials have been increasingly used in many heat transfer applications due to their enhanced thermal performance, and extensive studies have been conducted for a better scientific understanding of the heat transfer processes in such materials especially at the microscopic level. For heterogeneous materials with periodic microscopic structures, analysis can be performed over one such periodic unit if appropriate boundary conditions are applied. However, assumptions with no mathematical or physical justifications are often involved in previous studies, and this casts doubt on the accuracy and reliability of these results. In this study, a new set of boundary conditions are established based on rigorous mathematical derivations. The classical periodic boundary condition is generalized to incorporate the temperature differences between each pair of opposite boundaries of the periodic unit, and the global thermal gradient can be applied in arbitrary directions relative the structural periodicity. Also the interface between constituents in composite materials (or the fluid-solid interface in porous materials) is modeled according to the conjugate condition. This explicit approach incorporates the thermophysical properties of individual constituent materials and the possible thermal resistance at constituent interface, and thus provides a more complete and realistic representation of the heterogeneous system. This method with the generalized periodic boundary condition (GPBC) is carefully validated by comparing the temperature fields and effective conductivity for a two-dimensional (2D) heterogeneous model obtained from a direct simulation of a large domain size without using our boundary method and from one-unit simulations but with various periodic unit selections. The excellent agreement observed in these results indicates that our GPBC method correctly and accurately represents the underlying relationships in the thermal fields among periodic units. We also compare the simulation results for a 2D heterogeneous model with inclined poor conductivity rods in the middle, using our GPBC method and the insulated unit method (IUM) in previous publications; and remarkable differences in temperature fields and heat flux patterns are observed. Analysis and discussions are provided to show the unrealistic features in the IUM results due to the artificial assumptions on the boundary conditions. On the other hand, the temperature field from our GPBC method is consistent with intuitive physical considerations. The effects of constituent composition, conductivity and interface conductance on the effective thermal conductivity for a simple 2D heterogeneous material model, as well as the thermal flows with different Reynolds and Prandtl numbers through a staggered array of square blocks, are also examined. Despite the model simplicity, several interesting features are noticed, such as the heat flux response to changes in constituent conductivity and interface resistance and the saturation states of effective conductivity. Such information is valuable for a better understanding of the complex relationships between the microscopic structure and properties and the macroscopic thermal performances of composite and porous materials. The GPBC method developed in this work can also be readily implemented in typical numerical techniques in computational heat transfer such as the finite volume method, finite element method, and lattice Boltzmann method.

A review on mechanisms and recent developments in p-n heterojunctions of 2D materials for gas sensing applications

2D materials and their heterojunctions have been explored for gas sensing applications due to their tremendous surface-to-volume ratio, active edges with atomic thickness, and tunable electrical properties. Heterostructures of 2D materials exhibit absolutely novel physics and versatility with accelerated device performance by integrating the atomic scale properties of individual materials. Traditional gas sensors use homogeneous materials as the sensing interface in which the surface adsorbed oxygen ion species play an important role in its performance. But the performance of the sensors suffers greatly due to their selectivity and high working temperature leading to poor stability and short-term uses; the van der Waals 2D p-n heterojunction-based gas sensors hold several advantages since both the materials and the depletion layer formed at the junction can actively tune the sensing performance. By choosing 2D materials with different band structures, charge polarity, carrier concentration, and work function, band alignment at the interface can be precisely engineered to achieve the selective gas sensing performance with low operating temperature. Herein, we have reviewed the working principles, recent developments, and future perspectives of p-n heterojunctions of 2D materials for gas sensing applications.

Constrained Mixture Models of Soft Tissue Growth and Remodeling - Twenty Years After.

Soft biological tissues compromise diverse cell types and extracellular matrix constituents, each of which can possess individual natural configurations, material properties, and rates of turnover. For this reason, mixture-based models of growth (changes in mass) and remodeling (change in microstructure) are well-suited for studying tissue adaptations, disease progression, and responses to injury or clinical intervention. Such approaches also can be used to design improved tissue engineered constructs to repair, replace, or regenerate tissues. Focusing on blood vessels as archetypes of soft tissues, this paper reviews a constrained mixture theory introduced twenty years ago and explores its usage since by contrasting simulations of diverse vascular conditions. The discussion is framed within the concept of mechanical homeostasis, with consideration of solid-fluid interactions, inflammation, and cell signaling highlighting both past accomplishments and future opportunities as we seek to understand better the evolving composition, geometry, and material behaviors of soft tissues under complex conditions.

НАПРЯМИ РОЗВИТКУ СИСТЕМИ ЖИТТЄЗАБЕЗПЕЧЕННЯ КОМПЛЕКСУ БОЙОВОГО ЕКІПІРУВАННЯ ВІЙСЬКОВОСЛУЖБОВЦЯ З ВИКОРИСТАННЯМ ДОСВІДУ ПРОВІДНИХ КРАЇН СВІТУ

The location of the system of life-support in the complex of battle equipment of servicemen of subdivisions of military secret service of Land forces of the Armed Forces of Ukraine and perspective directions of her improvement are determined with the use of experience of leading countries of the world. The battle equipment of servicemen must answer the modern requirements of the tactics based on the new going near implementation of combat and special missions. Component part of complex of battle equipment is the system of life-support of serviceman. The system of life-support is totality of facilities of complex of battle equipment, that provides the vital functions of serviceman in composition of subdivisions and in tearing away from basic forces at executed combat missions. The system of life-support of complex of battle equipment includes the individual arming, engineering facilities, material property, food, medical facilities and facilities of monitoring of the physiology state of serviceman. One of priority directions of researches there is medical control of the functional state of servicemen and position-fix of scotched at development of the system of life-support of complex of battle equipment. Decimators, connection and management, and also providing of survival, vitality and mobility have decision influence on ability of serviceman in good time and qualitatively to execute the tasks put before him. The American specialists under a survival mean ability of serviceman provide the personal vital functions in a battle situation, that depends first of all on the level of preparation, adequate feed, medical providing and clothing. Due to modern development of technique, economic and demographic reasons today soldiery forces of NATO (The USA and Europe) began realization of the general programs, sent to reduction to the personnel, modernisation and restructuring of operative possibilities of their armies. Within the framework of these programs a project appeared under the name «Soldier of the future», that unites in itself work in area of increase of the productivity and efficiency of the separately taken fighter on the basis of technological achievements of XXI of century. For the armed forces of the USA the worked out system that is able to watch the bodily condition of soldiers. The system unites in itself the row of medical devices for determination of physical parameters of fighters: frequencies of heart-throbs, temperature of body, pressure, level of stress. The system is able to process data that come, and in case of necessity to pass them to medical service for realization of necessary actions. The analysis of consequences of battle actions showed that the half of victims that died would survive almost, if previous medical help would be given them during the first six hours upon receipt damages. Thus 10-15% reanimation events need victims during the first 10-30 min upon receipt defeats, otherwise they perish from bleeding, impassability of standard or heavy damage of cerebrum. In this connection there is a necessity of the use of the permanent checking system after the physiology state of servicemen and receipt of emergency signal in the moment of registration of deviations from the set intervals of norm regardless of location of the coverage of off-wire network staggered (patient) within the limits of zone. Development over of modern methods of diagnostics together with swift development of informatively-communication technologies was brought to creation quite of new methods of grant of medicare, where an important role is played exactly by information technologies. Keywords: system of life-support, individual arming, monitoring of the physiology state of serviceman, medical facilities.

(Invited) Solid State Sodium Satteries: From Solid Electrolytes to Functional Device

Li-ion batteries (LIBs) dominate the electrochemical energy storage technology because of their extraordinary performance, high energy density, and long cycle life. Still, the enormously growing demand of Li due to the expanding market raises concerns about the costs and the availability of lithium in the future, necessitating the development of beyond-lithium electrochemical energy storage concepts. Sodium is among the most investigated alternatives for lithium due to its abundance, widespread availability and much lower costs. The simple replacement of lithium with sodium in liquid electrolyte cells while keeping otherwise similar cell design results however in lower energy densities as compared to LIBs due to a higher molar mass, more positive redox potential and higher reactivity of sodium with liquid electrolytes as compared to lithium. In combination with solid electrolytes, however, much higher energy densities can be expected due to a possible use of metallic sodium as an anode instead of currently used hard carbons, opening new perspectives for the development of Na-based electrochemical energy storage systems.Sodium is among the most investigated alternatives for lithium due to its abundance, widespread availability and much lower costs. The simple replacement of lithium with sodium in liquid electrolyte cells while keeping otherwise similar cell design results however in lower energy densities as compared to LIBs due to a higher molar mass, more positive redox potential and higher reactivity of sodium with liquid electrolytes as compared to lithium. In combination with solid electrolytes, however, much higher energy densities can be expected due to a possible use of metallic sodium as an anode instead of currently used hard carbons, opening new perspectives for the development of Na-based electrochemical energy storage systems.Fundamental prerequisite for the development of high-performance solid state sodium batteries is a sufficiently high total conductivity of all its components at room temperature. The latter includes the ionic conductivity of the electrolyte (simultaneously acting as a separator in solid state batteries), the combined electronic/ionic conductivity of the cathode and the anode half-cells, as well as a high conductivity of key interfaces between the electrolyte and the electrode materials. The total conductivity critically relies on the bulk properties of individual materials, but also on their nanomorphology in the component assemblies as well as on the processing- and operation-dependent interface between the materials. The materials challenge therefore goes far beyond the bulk structure level, including the other fundamental aspects of materials chemistry (such as integration of materials into components, optimization of component microstructure, interface properties), electrochemistry (individual contributions to the total impedance, degradation mechanisms upon cell operation), and engineering (development of processing technology enabling fabrication of optimized components).I will give an overview of the sodium solid state battery development that spans from the development of solid state sodium conductors to their processing to functional battery components and finally to the fabrication and testing of the complete cells. I will discuss bottlenecks in the battery performance and will show the concepts for the mitigation of critical steps.

Spectral Radiative Properties of Ceramic Particles for Concentrated Solar Thermal Energy Storage Applications

This work investigates the spectral radiative properties of ceramic particles using a monochromator and a Fourier-transform infrared spectrometer (FTIR) with integrating spheres at wavelengths from 0.38 μm to 15 μm. Particles are encased between two transparent windows to obtain the directional-hemispherical reflectance of the particle bed. Two types of commercially available particles with three different sizes are examined. Integration over the solar spectrum reveals that the solar absorptance of the particle beds is between 0.940 and 0.957. The total emittance at 1000 K is also estimated by assuming the spectral emittance is independent of temperature. The optical constants of particles are modeled with effective medium approaches, considering the optical properties of individual constituent materials. The absorptance of the particle is estimated using the effective optical constants and compared with that of the particle bed from the measurement. This work facilitates the characterization of radiative properties of particles with a windowed method and provides a modeling scheme for approximating the radiative properties of composite ceramic materials.

Improvement of the Mechanical Properties of Thermosetting-Binding-System-Based Composites by Means of Kneading Procedure Modification and Composite Formulation

By understanding the effects of the physical properties of individual input materials (e.g., binding system) on the physical and thermal properties of a composite material, the latter can be engineered in advance according to the desired properties and application. Often, a need to replace a specific component in a composite material arises, due to various reasons such as high raw material prices, product price reduction, environmental issues, improvement of properties, and others. In this study, we focused on the substitution of a phenolic novolac resin binding system and the reduction of compounding process temperature in combination with material throughput and screw speed variation of a phenolic-novolac-resin-based composite material, manufactured by kneading process using a co-kneader single screw extruder. Modifications were carried out in the interest of reducing production process cost and positive environmental effect due to reduction of energy consumption in the compounding process. We achieved great success in improvement of mechanical properties with all four substituted phenolic molding compounds (PMCs), while the decrease in thermal stability was the lowest for PMCs prepared at higher screw speeds and material throughput. The results indicated that higher screw speeds produce the best combination of mechanical and thermal properties of PMCs.

Delaminacija višeslojne elastične osovine opterećene torzijom

Delamination cracks in multilayered circular shafts loaded in torsion are analyzed in terms of the strain energy release rate. It is assumed that the material in each layer has non-linear mechanical behaviour that is treated by the Ramberg-Osgood constitutive law. Also, each layer exhibits smooth material inhomogeneity in radial direction. It is assumed that the three material properties involved in the Ramberg-Osgood constitutive law vary continuously in radial direction of layers. A methodology for determination of the strain energy release rate is developed that is applicable for shafts made of arbitrary number of adhesively bonded concentric layers which have individual thickness and material properties. The delamination cracks are located arbitrary between layers. The methodology is used to investigate a delamination in a multilayered clamped shaft. The delamination is also studied by analyzing the energy balance for verification. Parametric analyses of the clamped multilayered shaft are carried-out.

Inhomogeneous Multilayered Beams of Linearly Changing Width: a Delamination Analysis

Delamination behaviour of an inhomogeneous multilayered cantilever beam of linearly changing width of the cross-section along the beam length is analyzed. The material in each layer of the beam has non-linear elastic mechanical behaviour. Besides, each layer exhibits continuous material inhomogeneity along the layer height. The solution to the strain energy release rate derived by considering the complementary strain energy is valid for beams made of arbitrary number of layers of individual thickness and material properties. In order to verify the solution, the strain energy release rate is obtained also by considering the balance of the energy.

Investigation of the effect of shape of inclusions on homogenized properties by using peridynamics

Fiber-reinforced composite materials are widely used in many different industries due to their superior properties with respect to traditional metals including their light weight, corrosion resistance, high strength, impact resistance, etc. Fiber-reinforced composite materials are composed of a strong fiber material, which mainly carries the applied load, and soft matrix material, which transfers the load to the fiber material and keep the fibers together. Macroscopic analysis of fiber-reinforced composite materials is done by utilising the homogenised material properties which mainly depends on individual material properties of fiber and matrix. In this study, in addition to the effect of individual material properties of constituents, the effect of the shape of fibers (inclusions) on homogenised properties is investigated by using a new methodology called peridynamics.

A two-constituent nonlinear viscoelastic model for asphalt mixtures

The goal of this study is to model the creep and recovery response of fine asphalt mixtures using a thermodynamically consistent nonlinear viscoelastic model. The model considers asphalt mixture to consist of two constituents: aggregate structure incorporating the asphalt–aggregate interface and asphalt binder. The efficacy of the model is evaluated using the response of warm fine aggregate mixtures (WFAM). These materials were produced using a polymer-modified binder of PG 76-22 and three warm mix additives (Sasobit, Advera and Rediset). Unaged and aged samples were subjected to creep stress levels of 75 and 400 kPa followed by rest periods. The model was quite successful in capturing the material behaviour as a single set of parameters were derived from the prediction of shear and normal stress responses for both 75 and 400 kPa stress levels. The presented model offers a unique feature in modelling the energy storage and dissipation of each of the two constituents. As such, one can examine the effect of changes in individual material properties on the material response and performance.