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Mineral aggregates are the main constituent of asphalt mixtures by volume, having a significant influence on the performance and durability of asphalt materials and flexible pavements, but their elastic stiffness properties are rarely investigated in the scientific literature. Nevertheless, these properties represent important input to micromechanical models which are aimed at providing a better understanding of the behaviour of asphalt mixtures as the basis for optimising their design. Herein, the elastic properties of 55 cylindrical specimens representing six types of rock from two quarries are investigated using ultrasonic testing, in order to assess the variation of the results between different rock types and between different samples of the same rock type as well as the sensitivity to specimen length (50–150 mm) and frequency (0.05–5.00 MHz). Most of the elastic stiffness values of the investigated rocks are found to be larger than stiffness values frequently used as input to micromechanical models. [ABSTRACT FROM AUTHOR]

A new constitutive creep model for Ni-base superalloys has been developed that links the instantaneous creep response to incremental microstructure changes occurring during creep. The structure starts with cuboidal γ′- particles embedded in the γ-phase, and transitions to a rafted structure. In the present Kocks-Mecking type of model, the dislocation density ρ is considered as a state variable that evolves during creep. The increase of ρ depends on the γ-channel width in the γ/γ′-microstructure. Recovery, i.e., the reduction of ρ, is modelled from thermally activated, mechanically assisted climb. The strain rate is also modelled from the very same recovery process. The model successfully describes creep curves in a range of temperatures and load stresses with a maximum of five physical parameters. Once the model has been calibrated, it can be used to predict creep curves for other temperatures, stresses, and microstructures if the channel width evolution is known. The model is even capable of making reasonable predictions when fitted only to a single experiment. Extrapolations to different alloys with moderately varying compositions are possible. • A new constitutive creep model for Ni-base superalloys has been developed. • The microstructure starts with cuboidal γ′- particles and transitions to a rafted structure. • The model describes creep curves in a range of temperatures and stresses with five physical parameters. • Once calibrated, the model predicts creep curves for other temperatures, stresses, microstructures, and chemical composition. • It can even make reasonable predictions when fitted only to a single experiment. [ABSTRACT FROM AUTHOR]

Graphene fillers have gained widespread attention as functional reinforcements for cement composites due to their excellent physical properties. The prediction of the thermal and electrical properties of graphene reinforced cement composites (GRCCs) is of great importance for developing intelligent and multifunctional civil engineering materials and structures. In this current work, a unified hybrid micromechanical model combining effective medium theory (EMT) and Mori-Tanaka-Benveniste (MTB) is developed to simultaneously predict the thermal and electrical conductivity of the GRCCs with considering pores and saturation, in which mechanisms including phonon transport, electron tunnelling and Maxwell-Wagner-Sillars (MWS) polarization are incorporated. Graphene nanoplatelets (GNPs) reinforced cement composites (GNPRCCs) samples are prepared and tested to validate the developed unified model. The results show that the electrical conductivity of the GNPRCCs is more sensitive to saturation than the thermal conductivity. When the porosity n = 0.2 and the GNP concentration is 1 wt%, the relative thermal and electrical conductivity increases by 5 % and 193 %, respectively, when the saturation index increases from 0.6 to 1. Elongated pores are more favorable for the formation of ionic networks for electrical conductivity in the saturated GNPRCCs, while spherical pores are more beneficial for heat transport. Elongated graphene fillers are preferred for enhancing both the thermal and electrical conductivity of dry and saturated GNPRCCs. The work is envisaged to provide guidelines for developing multifunctional cement composites. [ABSTRACT FROM AUTHOR]

Crumb Rubber Modified (CRM) binder specifications has historically relied on empirical testing with limited relationships to pavement performance. Several fundamental rheological tests have been developed in the Dynamic Shear Rheometer (DSR) with demonstrated correlation to field performance. However, these tests are conducted on aged materials to simulate in service performance through laboratory aging protocols that are not suitable for CRM binders. With the growing need for reliable performance-based characterisation of asphalt binders, a new approach to evaluating CRM binder performance is needed. This study utilises an experimental approach to introduce a new analysis methodology for evaluating performance characteristics of CRM binders. A new rheological parameter 'Crossover Temperature' is introduced and defined as the temperature at which the stiffnesses of CRM and residual (rubber filtered out after interaction) binders coincide. Crossover Temperature provided strong correlations to CRM binder fatigue and rutting characteristics, without the need for binder aging or micromechanical modelling. A wide range of base asphalt binders and CR sizes were utilised in this study. This parameter is recommended for Quality Control screening of CRM binders. [ABSTRACT FROM AUTHOR]

Brick-and-Mortar structures can exhibit exceptional combinations of properties, such as high strength and toughness. The properties are highly dependent on the failure regime, namely the ability to distribute damage prior to failure. In our recent work on rectangular Brick-and-Mortar structures, we have identified a transition from localised damaged (called ‘two-peak’ failure) to distributed damage (called ‘peak-plateau-peak’ failure), depending on the brick aspect ratio and the relative normal and shear layer material properties. However, the effect of non-rectangular brick shapes on these failure regimes has not yet been explored. In this work we predict with semi-analytical modelling, and validate with experiments, that introducing an angle into the ‘shear’ layers of the Brick-and-Mortar structure to create ‘diamond’ and ‘inverse diamond’ brick shapes results in a transition from ‘two-peak’ to ‘peak-plateau-peak’ failure for low aspect ratios. It is further shown that the angle required to transition to ‘peak-plateau-peak’ failure decreases with increasing aspect ratio, and that introducing an out of-plane angled layer in the form of an osteomorphic brick shape can further decrease the angle required for the transition. Our work demonstrates that the transition from ‘two-peak’ to ‘peak-plateau-peak’ failure significantly increases the toughness of the structure, without compromising strength or stiffness, highlighting the importance of understanding and controlling the parameters that affect the failure regimes.

Understanding nucleation of the cube-oriented grains during static recrystallization of medium to high stacking fault energy (SFE) FCC metals is both scientifically and industrially important. Dynamic recovery due to weak Hirth junctions is considered as one of the plausible explanations for the nucleation advantage of the cube orientation. However, influence of cross slip based dynamic recovery on the nucleation propensity of the cube orientation has not been studied in detail. For this purpose, we explicitly incorporated stress dependent dynamic recovery of screw dislocations into a dislocation density based crystal plasticity model. The model is utilized for studying influence of cross slip based local dynamic recovery during deformation and recrystallization nucleation of aluminium. We show that dynamic recovery influences local dislocation density difference and disorientation with the neighbouring locations for the main rolling texture components. Next, we analysed nucleation propensity of these texture components using a stochastic nucleation model. Simulation results show that without explicit incorporation of the dynamic recovery of screw dislocations, the Goss orientation shows the highest nucleation propensity. On the other hand, incorporation of the cross slip based dynamic recovery enhances nucleation propensity of the cube component. Therefore, cross slip based dynamic recovery is one of the important mechanisms for nucleation of the cube-oriented recrystallized grains. These results provide new insights into deformation and recrystallization nucleation of medium to high SFE FCC metals. [Display omitted] [ABSTRACT FROM AUTHOR]

This study explores the hybridizing effect of mechano-chemical activated fly-ash (FA) in polypropylene (PP) composites reinforced with sisal fibers. Activation and resistance against agglomeration of FA has been achieved by modifying it with 2, 4, and 6 wt.% of the cetyltrimethylammonium bromide (C-tab). FA activation with C-tab and particle size reduction to nano-level (< 1 µm) have been appropriately achieved with a planetary ball milling and the same has been confirmed from the dynamic light scattering technique. The hybrid composite containing 25 wt.% of sisal fiber and 5 wt.% of (6 wt.% C-tab) treated FA shows much improved tensile (40.12 MPa), flexural (53.27 MPa), and impact strengths (0.75 kJ/m2) than that of virgin PP and its 30 wt.% sisal fiber composites. This increase in tensile and flexural strength was 30.54% and 48% higher than neat PP. Maximum notched impact strength of 0.80 kJ/m2 have been reported by hybrid composite containing FA treated with 2 wt.% of the C-tab. Micromechanical modelling using a combination of rule of mixture and inverse rule of mixture separately with Halpin–Tsai predicted a value close to the experimental Young's modulus. DSC studies showed an increment in the composite's crystallinity upon fiber addition. Morphological analysis of the hybrid composite revealed good wettability of reinforcing fiber and FA within the matrix, whereas TGA showed an improved thermal stability of the composites. [ABSTRACT FROM AUTHOR]

Minimizing interfacial failure in the composite cathode remains a crucial challenge to unravel the full potential of all solid-state batteries (ASSBs). Polymer-based ASSBs offer promising means of minimizing those damage effects due to their high ductility. However, multicomponent polymers such as block copolymers (BCPs) are needed to meet requirements for both ionic conductivity and mechanical resistance. This study aims to provide a new insight into the combined effects of block copolymer composition (soft-to-hard phase ratio) and interfacial strength on the coupled diffusion-mechanics response of an ASSB cathode, achieved by proposing a non-linear computational micromechanics approach. The approach combines a pressure-dependent diffusion process, interfacial gap-dependent diffusivity, and advanced elasto-viscoplastic constitutive model for a BCP, and it is implemented numerically within a non-linear finite element framework. Two cathode design concepts are explored here, with and without the BCP coating. Results from these case studies suggest that there is a strong interplay between the interface strength (between active particles and the BCP matrix), the BCP material composition, and the interfacial diffusivity. It is found that interfacial damage can be minimized by increasing both the interfacial strength and the amount of the soft component in the BCP system. If the diffusivity across the interface is damage-dependent, the latter is reduced when the BCP is predominantly made of the hard phase. Ultimately, a simple sensitivity analysis reveals that interfacial strength plays a vital role in minimizing interfacial damage, while the coating thickness is the least influential design parameter. [Display omitted] • Non-linear computational micromechanics diffusion-mechanics framework is developed. • Finite-strain elasto-viscoplastic constitutive model for a block copolymer is proposed. • Effect of the block copolymer composition on interfacial damage is investigated. [ABSTRACT FROM AUTHOR]

Conventional Laves phase is extremely brittle at room temperature. However, through a systematic study, we showed that the quinary Co-Cr-Fe-Ni-Nb Laves phase in a eutectic high entropy alloy (EHEA) can be plastically deformed at room temperature when its size is refined below 200 nm. Based on our current results, we propose a general micromechanical model that not only explains the suppression of cracks in the high entropy Laves phase but also enables the extraction of its fracture toughness even when the high entropy Laves phase deforms and cracks in a dual-phase microstructure. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The present work provides an analytic solution for the stiffness to crack length relation in microscopic cantilever shaped fracture specimens based on classical beam theory and substitution of the crack by a virtual rotational spring element. The resulting compact relationship allows for accounting of the actual beam geometry and agrees very well with accompanying finite element simulations. Compared with the only other model present in literature the proposed relationship reduces the deviation between model and data to a maximum of 1.6% from the previous minimum of 15%. Thus, the novel solution will help to reduce the necessity for individual simulations and aim to increase the comparability of elastic-plastic microcantilever fracture experiments in the future.

A microstructure-based modelling approach was used to study the deformation behaviour of polycrystalline honeycomb structures under rubbing loading. Rubbing originates from the sliding contact between sealing surfaces in a gas turbine engine. As a stationary component of the sealing system, the honeycomb structure's role is to prevent catastrophic failure of the rotating component. Therefore, normal forces and surface deformations of the honeycomb structure need to be minimised to limit the heat input into the rotating component. To achieve a detailed representation of the honeycomb material response, the constitutive behaviour of the employed nickel-based superalloys Hastelloy X and Haynes 214 was modelled with a crystal plasticity approach, utilising a finite element framework. Uniaxial tensile tests at relevant temperatures and strain rates resembling the rubbing allowed the identification of crucial model parameters. The simulative studies based on the unit cell of the honeycomb structure revealed that the normal forces and the surface deformations are strongly affected by the microstructural features (size and orientation of the grains) and the applied deformation rate. In addition, a significant amount of residual stresses could be found for the macroscopically unstressed state after cooling and unloading. [ABSTRACT FROM AUTHOR]

This paper carries out a survey on available methods for micromechanical modelling on asphalt mixture. Focus is placed on models based on different concepts as well as different computational methods in numerical implementation. The major topics covered include: models based on discrete element method, micromechanical finite element models, disturbed state concept, the discontinuous deformation analysis method, integration of mechanics on different scales, etc. A brief description of some fundamental algorithms in discrete element and finite element methods are also included due to the modelling accuracy and thus wide interest in them. Simple case studies are included to illustrate the methods in discussion wherever space allows. [ABSTRACT FROM AUTHOR]

Brick-and-Mortar structures are of high interest because their staggered multi-material arrangement can result in a remarkable combination of high strength and high toughness. Synthetic replication of these structures with high geometric control has been made possible recently with the advances in multi-material Additive Manufacturing (AM). However, very little is known on how inherent material variation in the constituent materials, which can be significant in AM, affects the structure response. In this work, we use a semi-analytical model to theoretically show that a variation in the strength of the layers in a Brick-and-Mortar structure has a significant effect on the failure response of the structure. It can lead to changes in failure regimes and negatively impact the mechanical properties, such as decrease the strain to failure or decrease the yield stress. This is particularly pronounced when the material behaviour is situated close to the transition point between failure regimes. We then present an experimental method to capture strength variability in the layer material and demonstrate that the incorporation of this variability into the semi-analytical model improves our prediction of the failure response of the structure, as compared to experiments. [Display omitted] • Strength distribution incorporated into Brick-and-Mortar semi-analytical model. • Strength distribution can change the failure regime of the structure. • Structures near the failure regime transition point most sensitive to distribution. • Calibrated layer strength distribution improves experimental predictions. [ABSTRACT FROM AUTHOR]

Damage characterization and micromechanical modelling in dual-phase (DP) steels have recently drawn attention, since any changes in the alloying elements or process route strongly influence the microstructural features, deformation behavior of the phases, and damage to the micro-mechanisms, and subsequently the particular mechanical properties of the material. This approach can be used to stablish microstructure–properties relationships. For instance, the effects of local damage from shear cutting on edge crack sensitivity in the following deformation process can be studied. This work evaluated the deformation and damage behaviors of two DP1000 steels using a microstructure-based approach to estimate the edge cracking resistance. Phase fraction, grain size, phase distribution, and texture were analyzed using electron backscatter diffraction and secondary electron detectors of a scanning electron microscope and employed in 3D representative volume elements. The deformation behavior of the ferrite phase was defined using a crystal plasticity model, which was calibrated through nanoindentation tests. Various loading conditions, including uniaxial tension, equi-biaxial tension, plane strain tension, and shearing, along with the maximum shear stress criterion were applied to investigate the damage initiation and describe the edge cracking sensitivity of the studied steels. The results revealed that a homogenous microstructure leads to homogenous stress–strain partitioning, delayed damage initiation, and high edge cracking resistance.

Hydrogen transport behaviour in metals is greatly influenced by the mechanical stress and the underlying microstructural features. In this work, a micromechanical model based on coupled crystal plasticity and hydrogen diffusion is developed and applied to model hydrogen diffusion and storage in a polycrystalline microstructure. Particular emphasis is laid on mechanical influences on hydrogen transport, invoked by internal stresses and by trapping of dislocations generated by plastic strains. First, a study of a precharged material is carried out where hydrogen is allowed to redistribute under the influence of mechanical loading. These simulations demonstrate to which extent hydrogen migrates from regions with compressive strains to those with tensile strains. In the next step, the influence of plastic prestraining on hydrogen diffusion is analysed. This prestraining produces internal residual stresses in the microstructure, that mimic residual stresses introduced into components during cold working. Lastly, a series of permeation simulations is performed to characterise the influence of hydrogen trapping on effective diffusivity. It is shown that the effective diffusivity decreases with stronger traps and the effect is more prominent at a larger predeformation, because the trapped hydrogen concentration increases considerably. The reduction of effective diffusivity with plastic deformation agrees very well with experimental findings and offers a way to validate and parameterise our model. With this work, it is demonstrated how micromechanical modelling can support the understanding of hydrogen transport on the microstructural level. [ABSTRACT FROM AUTHOR]

Uniform dispersion of carbon nanotubes (CNTs) is a key issue for utilization of their reinforcement potential in CNT-reinforced metal matrix nanocomposites (MMNCs). It was reported that CNT clusters often exist in MMNCs prepared by various techniques, which reduces the load transfer efficiency between the matrix and reinforcement. In this paper, a new micromechanical constitutive model of CNT-reinforced MMNCs is developed, which takes into account of the influences of CNT clusters and misorientations. The strength values of a CNT/Al nanocomposite predicted by the new model are compared first with experimental data for validation. Then, the developed model is applied to predict the size effect, temperature effect and strain rate effect of the nanocomposite in its overall elastoplastic response.

A validation is reported for micromechanical simulation using a reimplementation of an elasto-viscoplastic FFT-based (EVPFFT) formulation, i.e., the Micromechanical Analysis of Stress-strain Inhomogeneities with fast Fourier transform (MASSIF) code, against experimental data obtained from synchrotron x-ray diffraction. The experimental data was collected during in-situ deformation of a titanium alloy specimen by High Energy Diffraction Microscopy (HEDM), which provided the average elastic strain tensor and orientation of each grain in a polycrystalline sample. MASSIF was used to calculate the local micromechanical fields in a Ti-7Al polycrystalline sample at different load levels. The initially attempted simulation showed that, although the effective response was calibrated to reproduce the experiment, MASSIF was not able to reproduce the micromechanical fields at the scale of individual grains. The differences between calculated and measured averages at the grain scale were related to initial residual strains resulting from the prior processing of the material, which had not been incorporated in the original calculation. Accordingly, a new simulation was instantiated using information on the measured residual strains to define a set of eigenstrains, calculated via an Eshelby approximation. This initialization significantly improved the correlation between calculated and simulated fields for all strain and stress components, for measurements performed within the elastic regime. For the measurements at the highest load, which was past plastic yield, the correlations deteriorated because of plastic deformation at the grain level and the lack of an accurate enough constitutive description in this deformation regime. [ABSTRACT FROM AUTHOR]

Elastic properties of laminate composites based Carbone Nanotubes (CNTs), used in military applications, were estimated using homogenization techniques and compared to the experimental data. The composite consists of three phases: T300 6k carbon fibers fabric with 5HS (satin) weave, baseline pure Epoxy matrix and CNTs added with 0.5%, 1%, 2% and 4%. Two step homogenization methods based RVE model were employed. The objective of this paper is to determine the elastic properties of structure starting from the knowledge of those of constituents (CNTs, Epoxy and carbon fibers fabric). It is assumed that the composites have a geometric periodicity and the homogenization model can be represented by a representative volume element (RVE). For multi-scale analysis, finite element modeling of unit cell based two step homogenization method is used. The first step gives the properties of thin film made of epoxy and CNTs and the second is used for homogenization of laminate composite. The fabric unit cell is chosen using a set of microscopic observation and then identified by its ability to enclose the characteristic periodic repeat in the fabric weave. The unit cell model of 5-Harness satin weave fabric textile composite is identified for numerical approach and their dimensions are chosen based on some microstructural measurements. Finally, a good comparison was obtained between the predicted elastic properties using numerical homogenization approach and the obtained experimental data with experimental tests. [ABSTRACT FROM AUTHOR]

Strain Hardening Cementitious Composites (SHCC) are fiber reinforced composites exhibiting strain hardening and multiple cracking behaviors. The Polyvinyl Alcohol (PVA) fibers used in SHCC are expensive for normal civil engineering applications, so one kind of Polyethylene terephthalate (PET) fibers recycled from waste plastics are used in this study as a substitute of PVA fibers. Uniaxial tensile test was carried out on SHCC samples made with PVA or PET fibers where the PET-SHCC was found to behave poorer than the PVA-SHCC due to the weaker bond between PET fibers and matrix. Nevertheless, in the modified Charpy impact test which was designed to evaluate the impact energy absorption ability of SHCC, the PET-SHCC dissipated a great amount of energy comparable to that by PVA-SHCC, indicating that PET fibers can provide excellent impact resistance to cementitious composites. To reveal the mechanism of impact energy absorption, a physical model was developed to simulate the impact test, which can well support the experimental observations. Based on above findings, a hybrid mix of 1 vol% PVA fibers and 1 vol% PET fibers is recommended for practical applications to provide adequate tensile performance and excellent impact resistance with eco-friendly ingredients at low cost. [ABSTRACT FROM AUTHOR]

In biomedical implant applications, porous metallic structures are particularly appealing as they enhance the stiffness compatibility with the host tissue. The mechanical properties of the porous material are critically affected by microstructural features, such as the pore shape, the distribution of porosity, and the level of porosity. In this study, mechanical properties of porous commercially pure titanium structures with various porosity levels were investigated through a combination of experiments and finite element modelling. Finite element simulations were conducted on representative volume elements of the microstructure to assess the role of pore parameters on the effective mechanical properties. Modelling results indicated that the shape of the pore, in addition to porosity level, play a significant role on the effective behaviour. Finite element simulations provide reasonably accurate prediction of the effective Young’s modulus, with errors as low as 0.9% for porosity of 35%. It was observed that the large spread in yield strength produced by the simulations was most likely due to the random pore distribution in the network, which may lead to a high probability of plastic strain initiation within the thin walls of the porous network. [ABSTRACT FROM AUTHOR]

Friction Stir Processing (FSP) is an attractive manufacturing technique to produce Mg matrix composites since it avoids the problem of excessive reactivity between reinforcement and matrix encountered in liquid-phase processing routes. However, the strength of the interface in C-reinforced Mg matrix composites produced by FSP remains to be assessed. A short fibre composite has been fabricated by FSP a stack of a C-fabric between two Mg-AZ91D alloy sheets. In order to elucidate the interplay between matrix hardness and interface bonding strength, the work investigates the influence of heat treatment on the mechanical properties of the composites. An incremental Mori-Tanaka model is developed to analyse the relative roles of heat treatment and C-fibre reinforcement on the flow strength and ductility of the composites in tension and compression. The mean-field model provides an estimate of the stress at the matrix/fibre interface, from which a simple debonding criterion can be derived. Comparison between model predictions and experimental data indicates that damage in the FSP composites is triggered by early interfacial debonding. Based on Finite Element simulations of a tensile test carried out in-situ in a scanning electron microscope, the critical interfacial stress for debonding was identified to be 435 MPa in simple traction but only 250 MPa when damage is governed by shear. This explains the limited strengthening by C fibres observed in heat treated composites. [ABSTRACT FROM AUTHOR]

Machining tools are used in many areas of production. To a considerable extent, the performance characteristics of the tools determine the quality and cost of obtained products. The main materials used for producing machining tools are steel, cemented carbides, ceramics and superhard materials. A promising way to improve the performance characteristics of these materials is to design new nanocomposites based on them. The application of micromechanical modeling during the elaboration of composite materials for machining tools can reduce the financial and time costs for development of new tools, with enhanced performance. This article reviews the main groups of nanocomposites for machining tools and their performance. [ABSTRACT FROM AUTHOR]

A detailed study on micromechanical constitutive modelling of unidirectional fiber reinforced and plain woven textile composites (PWTC) is performed. The primary objective is to compute the equivalent homogenized effective properties of PWTC through its mesoscale model. A novel parallel-series model is proposed, to compute the engineering constants in transverse plane of unidirectional composite, and validated against Chamis approaches, Mori–Tanaka and finite element method results for glass/epoxy composite. Computational homogenization of representative volume element (RVE) of transverse direction unidirectional composite is performed satisfying the periodicity of RVE. The RVE of PWTC is then approximated as cross-ply laminate consisting warp and fill plies, whose averaged properties are computed considering fiber undulations by micromechanics-based models. The bounds of the effective material properties of PWTC are determined employing Voigt and Reuss approximation. The effective engineering constants of glass/epoxy PWTC computed are compared with in-house experiments and found to be closely matching with Voigt model. [ABSTRACT FROM AUTHOR]

This paper presents a method for virtual testing composite microstructures with real fibre distributions, and compares the debonding and crack response with experimental results of identical microstructures under similar loading conditions. Prior to physical testing of HTA/6376 composite laminates, the fibre distribution of the undamaged physical specimen is automatically detected through image analysis and reconstructed as a 2D model in Abaqus software and tested following a sub-modelling approach. Once in-situ SEM micro-mechanical testing of the physical specimen is completed, the virtual and experimental crack paths can be directly compared to determine the viability of the virtual testing method. The influence of thermal residual stress on premature fibre-matrix debond initiation and crack propagation is also investigated. The results of the virtual testing presented in this paper give a strong correlation to the experimentally observed crack growth, where significant improvement on similar previously published virtual experimental results for composite materials in terms of both microstructure scale and accuracy of the crack representation, is observed. For the thermo-mechanically loaded models, thermal residual stresses were found to influence the crack path around certain fibres where localised thermal residual stresses were present, leading to a more accurate representation of damage than that given by the purely mechanically loaded models. [ABSTRACT FROM AUTHOR]

Novel non-destructive characterization techniques performed at light sources provide previously inaccessible 3-D mesoscopic information on the deformation of polycrystalline materials. One major difficulty for interpretation of these experiments through micromechanical modelling is the likelihood that processing and/or mounting the sample introduce residual stresses in the specimen. These stresses need to be incorporated into crystal plasticity formulations, for these models to operate directly from microstructural images and be predictive. To achieve this, the initial micromechanical state of each voxel needs to be specified. In this letter we present a method for incorporating grain-averaged residual stresses for instantiation of crystal plasticity simulations. [ABSTRACT FROM AUTHOR]

Ceramic materials are commonly used to design multi-layer armour systems thanks to their favourable physical and mechanical properties. However, during an impact event, fragmentation of the ceramic plate inevitably occurs due to its inherent brittleness under tensile loading. Consequently, an accurate model of the fragmentation process is necessary in order to achieve an optimum design for a desired armour configuration. In this work, shockless spalling tests have been performed on two silicon carbide grades at strain rates ranging from 10³ to 104 s-1 using a high-pulsed power generator. These spalling tests characterize the tensile strength strain rate sensitivity of each ceramic grade. The microstructural properties of the ceramics appear to play an important role on the strain rate sensitivity and on the dynamic tensile strength. Moreover, this experimental configuration allows for recovering damaged, but unbroken specimens, giving unique insight on the fragmentation process initiated in the ceramics. All the collected data have been compared with corresponding results of numerical simulations performed using the Denoual-Forquin- Hild anisotropic damage model. Good agreement is observed between numerical simulations and experimental data in terms of free surface velocity, size and location of the damaged zones along with crack density in these damaged zones. [ABSTRACT FROM AUTHOR]