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Earthquake-induced fractures in steel structures are characterised by high-strain low-cycle conditions. In order to investigate the ultra-low cyclic fatigue fracture of steel welded joints under earthquakes, two most commonly used structural steels (Q235B and Q345B) and the corresponding welds were studied by experiments and numerical analysis in this paper. Specimens were extracted from the base material, the weld metal and the heat affected zone to investigate the behaviour in different parts of the welded joint. Eighteen smooth round bars were tested under large strain amplitudes, the hysteretic properties, damage degradation characteristics and failure process were analyzed. Constitutive model named Chaboche model was calibrated to describe the cyclic hardening behaviour of these materials. Seventy-two notched round bars with three different notch sizes and two loading protocols were tested to study the fracture behaviour of different materials at different stress triaxialities and different strain amplitudes. Two micromechanical fracture models: cyclic void growth model and degraded significant plastic strain model were calibrated based on the test results. The micromechanical models and Chaboche model were incorporated into numerical simulations by software ABAQUS with subroutine VUMAT to predict the materials fracture. The results show that the failure process under cyclic loads is opposite to that of monotone loads. The dissipation capacity of Q345B is superior to that of Q235B. The fracture resistance deteriorate more in the weld zone under the same loading conditions. The validated models can be used to effectively and accurately evaluate the fracture in steel welded connections under ULCF conditions. [ABSTRACT FROM AUTHOR]

This article is divided into two main sections. The focus of the first is the determination of the effective piezoelectric and dielectric properties of Boron-Nitride (BN) reinforced nanocomposite (BNRC) and the focus of the second is the electromechanical response of the BNRC beam accounting for surface and flexoelectric effects. The effective properties of the BNRC were obtained using micromechanics and homogenization techniques that consider Hill's average concentration factor, while in the second the electromechanical response, which requires the developed effective BNRC properties, was analytically determined by making use of size-dependent Euler–Bernoulli (E–B) beam description and an extended theory of linear piezoelectricity. The considered beam is subjected to a uniformly distributed load with three different types of support: clamped–clamped, simply-supported, and clamped-free. The outcomes of E–B beam model are also compared with that of FE results and are found to be in excellent agreement. Our results reveal that the electromechanical properties of BNRC are improved in the transverse direction, which in turn activates transverse actuation under the applied field. Furthermore, our results show that the size-dependent flexoelectric and surface effects must be considered for the accurate modeling of active nanostructures. We also observed that the bulk flexoelectric effect stiffens the nanobeam irrespective of the support type, whereas the surface effect stiffens or softens the nanobeam depending on the support type. This foundational study highlights the scope for the development of high-performance and efficient BN-based piezoelectric nanostructures, which can be used in nanoelectromechanical systems and structural health monitoring applications. [ABSTRACT FROM AUTHOR]

In this study, the elastic response and residual stress of the ceramic matrix composites were simulated in multiscale view for exploring the elastic modulus of the two-phase composites reinforced with ceramic particles by diffraction method. Combined with the macroscopic stress-strain relationship of two-phase composites, the effective elastic response model under uniaxial loading was theoretically predicted by introducing the effective representative volume element (RVE). Subsequently, the effective elastic properties of the material and its constituents were calculated, along with comparison with the experimental values reported in the literature. On the basis of Eshelby's inclusion theory, a micromechanical elastic response model for the two-phase composites was established, and a series of micromechanical field equations related to the crystal planes diffraction elastic constants were derived. A comparison with the different micromechanical models for predicting the crystal planes diffraction elastic constants of the ceramic matrix and particle reinforcement was carried out, so as to qualitatively and quantitatively analyze the residual stress. It was revealed that the effective elastic parameters of the ZrB 2 matrix and SiC particle reinforcement were very close to the experimental values reported in literature, and the calculated values of the elastic modulus in seven crystallographic diffraction directions were similar to the experimental values. In addition, the average residual stress of the SiC reinforcement and the ZrB 2 ceramic matrix predicted by the developed model were consistent with the measured, which proved the reliability and accuracy of the theoretical model for multiscale simulation of the residual stress of two-phase composites. [ABSTRACT FROM AUTHOR]

The numerical study on the complex failure mechanism in dual phase steels is significant because of their intricate microstructure. Their mechanical behavior depends on the volume fraction of martensite/ferrite and microstructural morphology, such as size, aspect ratio, interconnectivity, and mechanical behavior of individual phases. Like all multiphase materials, the connectivity between different phases and possible changes in mechanical properties near the interface (interphases) play significant roles in microstructural damage initiation and propagation and, therefore, affect the overall mechanical response. This study focused on the stress–strain behavior of DP-800 steel using finite element analysis of three-dimensional representative volume elements. Based on experimental results, local hardening was considered in the ferrite matrix near the martensite islands. Also, various volume fractions and material properties for different hardening zones were implemented to study the stress–strain behavior of DP steels. Interface elements based on cohesive zone modeling were considered to simulate the damage on the ferrite and martensite interface numerically. Furthermore, hydrostatic stress distribution which is known as an indicator to show the void initiation was used to predict damage zones and the stress distribution is compared with the results obtained from the cohesive zone method. The mechanical behaviors of the finite element models by the proposed methodology, considering cohesive elements and hardening zones in three-dimensional representative volume elements, indicated a better adaptation to the experimental results. [ABSTRACT FROM AUTHOR]

In this paper, mechanical properties of thermoset epoxy based two-phase and hybrid nanocomposites containing carbon nanotubes (CNTs), and carbon nano diamond particles (CNPs) are determined using two different multiscale modeling approaches. The effects of resin crosslinking, interphase mechanical properties, and filler agglomeration on nanocomposite mechanical properties are investigated. First, the crosslinking between Diglycidyl ether of bisphenol A (DGEBA) resin and Diethylenetriamine (DETA) hardener is modeled considering different crosslinking forms and ratios using molecular dynamics (MD) simulations. Results indicate that resin elastic modulus increases with increasing the crosslinking ratio especially above 75%, but crosslinking form has an insignificant effect on resin modulus. Next, different nanofillers and their interphases are modeled using MD simulations to determine the representative volume element (RVE) and the effective fiber sizes and mechanical properties. The thickness of the interphase for each nano filler type is determined from the radial distribution function (RDF) diagram in order to determine the effective fiber volume more realistically. Then, the general Halpin-Tsai model is modified by adding an interphase volume factor and is used to determine two-phase and hybrid nanocomposite mechanical properties using effective nano filler properties. In addition, a new numerical multiscale modeling technique was developed which uses the MD-determined effective filler properties along with finite element method (FEM) to determine nanocomposite mechanical properties. Nanocomposites reinforced with aligned and randomly oriented reinforcements are modeled. Good agreement is observed between the two multiscale modeling techniques for the two-phase nanocomposite mechanical properties. Finally, the effect of filler agglomeration on nanocomposite properties is investigated. The results indicate that agglomeration decreases elastic modulus of CNT/epoxy nanocomposite. However, agglomeration does not have a significant effect on elastic modulus of CNP/epoxy nanocomposite. [ABSTRACT FROM AUTHOR]

One of the limiting factors in the life of lithium-ion batteries is the diffusion-induced stresses on their electrodes that cause cracking and consequently, failure. Therefore, improving the structure of these electrodes to be able to withstand these stresses is one of the ways that can extend the life of the batteries as well as improve their safety. In this study, the effects of adding graphene nanoplatelets and microparticles into the active plate and current collectors, respectively, on the diffusion induced stresses in both layered and bilayered electrodes are numerically investigated. The micromechanical models are employed to predict the mechanical properties of both graphene nanoplatelet-reinforced Sn-based nanocomposite active plate and silica microparticle-reinforced copper composite current collector. The effect of particle size and volume fraction in the current collector on diffusion induced stresses has been studied. The results show that in electrodes with a higher volume fraction of particles and smaller particle radii, decreased diffusion induced stresses in both the active plate and the current collector are observed. These additions will also result in a significant decrease in the bending of the electrode. [ABSTRACT FROM AUTHOR]

This study focused on an innovative practical method using computer vision for particle size measurement, which serves as a key precursor for predicting the elastic modulus of polymer nanocomposites. This approach involved the morphological segmentation of the nanodispersed phase. It aimed, for the first time, to address the impractical conditions resulting from the assumption of idealized single-particle sizes in a monodispersed system during modeling. Subsequently, a micromechanical finite element framework was employed to determine the interphase thickness and modulus in ultrahigh molecular weight polyethylene/nanozeolite composites, following the quantification of nanoparticle sizes. The size measurement approach relied on morphological images extracted from scanning electron microscopy micrographs of impact-fractured surfaces. To compute the interphase thickness, experimental data was fitted to an interphase-inclusive upper-bound Hashin-Shtrikman model, with the measured average particle size per composition serving as a crucial input. Subsequently, the interphase elastic modulus was computed based on its thickness, employing a hybrid modified-Hashin-Hansen and Maxwell model. These estimated interfacial variables were then utilized as inputs for the finite element model to determine the tensile modulus. A comparison between the model results and measured data revealed a maximum discrepancy of 3.29%, indicating the effectiveness of the methodology employed in quantifying interfacial properties.

This paper aims to investigate the effect of viscoelastic behavior of polymer matrix of unidirectional fiber-reinforced laminated composite on stress distribution around the pin-loaded hole under tensile loading. The Laplace transform is used to prevent the integral form of matrix governing stress-strain relation. Applying a micromechanical model, all equilibrium equations for the fibers are written analytically in the Laplace domain. The numerical algorithm of Gaver–Stehfest is implemented, and the governing equations were solved at any given time to extract the concerned results in the time domain. The obtained results are validated against the Finite Element Method results obtained through ANSYS software. Moreover, a comparison of the results of this study at the time equal zero with elastic solutions of other references showed a good agreement. The results revealed that in the long term, the maximum tensile load in the intact fiber around the pinhole was enlarged and the tensile load in fibers far from the pinhole slightly was decreased. Moreover, the location of the maximum axial load that had occurred on pinhole edges was moved slightly toward the center over time. [ABSTRACT FROM AUTHOR]

Much attention has recently been paid to investigating the internal mechanisms between the void structures of foamed concrete and its mechanical behavior. This study adopted the X-ray computed tomography (X-CT) technique to build three-dimensional (3D) internal void structures of foamed concrete before conducting the unconfined compression test. A sensitivity analysis was conducted to evaluate the influence of the void structure on the mechanical properties. The results showed that the contacts between voids had a primary influence on the residual strength, and the void size was the major influence factor on the modulus. A micromechanical model was developed to simulate the mechanical behavior of the foamed concrete under compression, and good agreements were found with the test results. A simple equation was proposed to predict the mechanical properties of the foamed concretes considering the effects and variations of the void structures on the mechanical properties. Combining the equation with the micromechanical damage model, the variations of the mechanical behavior due to the difference in void structures can be well predicted. [ABSTRACT FROM AUTHOR]

Photopolymerization is an advanced technology to trigger free radical polymerization in a liquid monomer solution through light-induced curing, during which mechanical properties of the material are significantly transformed. Widely used in additive manufacturing, parts fabricated with this technique display precisions up to the nanoscale; however, the performance of final components is not only affected by the raw material but also by the specific setup employed during the printing process. In this paper, we develop a multiphysics model to predict the mechanical properties of the photo-cured components, by taking into account the process parameters involved in the considered additive manufacturing technology. In the approach proposed, the main chemical, physical, and mechanical aspects of photopolymerization are modelled and implemented in a finite element framework. Specifically, the kinetics of light diffusion from a moving source and chain formation in the liquid monomer is coupled to a statistical approach to describe the mechanical properties as a function of the degree of cure. Several parametric examples are provided, in order to quantify the effects of the printing settings on the spatial distribution of the final properties in the component. The proposed approach provides a tool to predict the mechanical features of additively manufactured parts, which designers can adopt to optimize the desired characteristics of the products. [ABSTRACT FROM AUTHOR]

In this research, the effects of induced delamination on the variation of the mechanical properties of composite laminates subjected to bending loads are investigated using a micromechanical model. For this purpose, the variation of the mechanical properties of delaminated laminates is determined using stress analysis of damaged ply and classical laminate theory (CLT) relationships. Using the proposed model and CLT, the fracture toughness due to induced delamination formation is presented in cross‐ply laminates. Subsequently, the variation of strain energy release rate (SERR) is calculated in terms of crack density using analytical and finite element (FE) models to detect dominant failure modes in different crack densities. The results are compared with those of matrix cracking propagation. The results obtained by the proposed analytical model are in good agreement with those obtained by existing numerical and experimental approaches. The proposed model can be utilized to predict induced delamination formation in composite laminates subjected to bending loads. Highlights: An analytical micromechanical model is adopted to predict the variation of flexural mechanical properties, for any stacking sequence.The laminates are subjected to bending loads containing matrix cracks and delamination.By using classical laminate theory (CLT), the fracture toughness required to formation of induced delamination in composite laminates has been estimated.By using the finite element (FE) method, numerical model has been introduced to predict SERR in terms of the damage modes in cross‐ply laminates. [ABSTRACT FROM AUTHOR]

The fracture strain of carbon fiber-reinforced plastics (CFRPs) within CFRP/steel hybrid laminate composites is reportedly higher than that of CFRPs due to transverse compressive stress induced by the steel lamina. A micromechanical model was developed to explain this phenomenon and also to predict the mechanical behavior of CFRP/steel hybrid laminate composites. First, the shear lag theory was extended to calculate stress distributions on fibers and matrix material in a CFRP under multiaxial stress condition, considering three deformation states of matrix (elastic and plastic deformation and fracture) and the transverse compressive stress. Then, the deformation behavior of CFRP was predicted using average stress in the ineffective region and the Weibull distribution of carbon fibers. Finally, the mechanical properties of CFRP/steel hybrid laminate composites were predicted by considering the thermal residual stress generated during the manufacturing process. The micromechanical model revealed that increased transverse compressive stress decreases the ineffective lengths of partially broken fibers in the CFRP and results in increased fracture strain of the CFRP, demonstrating the validity of the current micromechanical model. [ABSTRACT FROM AUTHOR]

As one of the most promising smart materials, magnetorheological (MR) gels have been widely applied in the vibration mitigation of engineering structures. An accurate and effective model for MR gels is of great significance for its in-depth research and engineering application. Existing models for MR materials mainly follow the magnetic dipole theory used for MR fluid, but this theory takes no account of the particle size and, thus, cannot apply to MR gels with a relatively higher volume fraction of particles. In this paper, a micromechanical model for MR gels was proposed and experimentally verified based on the planar current loop model. Firstly, high-performance MR gels were prepared, and basic performance characterizations, including the magnetization property and the sedimentation stability, were carried out. Then the magnetic energy of particles calculated by the magnetic dipole model and the planar current loop model were compared, and the micromechanical model of MR gels was proposed based on the planar current loop model. In the parameter determination process, the data obtained by magnetization tests of the particles were fitted to form the magnetization curve with higher accuracy. Finally, the yield shear stresses of the prepared MR gels were obtained by property tests, and the effectiveness and accuracy of the proposed micromechanical model were verified by comparing the test data with the theoretical values calculated by the proposed model. [ABSTRACT FROM AUTHOR]

Phenomenological models are commonly used to model void nucleation from second phase particles in ductile fracture simulations. Parameters in these continuum models are typically estimated using indirect methods, by comparison with experimental fracture data. In this paper, a novel approach based on acoustic emission (AE) measurements in smooth and notched bar tension tests is proposed to estimate void nucleation model parameters such as the mean and standard deviation of the nucleation strains. Tensile tests on AA 7075-T651 specimens combined with AE data establish a robust correlation between AE amplitude and the average void nucleation rate. The nucleation parameters are calibrated using a dog-bone tensile specimen. Simulations using these calibrated parameters accurately reproduces AE amplitude trends in other specimen geometries. This approach provides a promising alternative to traditional calibration methods, enhancing the reliability and adaptability of void growth based ductile fracture models. [Display omitted] • A correlation exists between void nucleation and acoustic emission (AE) amplitude for AA 7075-T651. • The Chu and Needleman void nucleation parameters can be calibrated using acoustic emission. • With calibrated parameters, the model reproduces AE amplitude characteristics in various geometries. [ABSTRACT FROM AUTHOR]

• A novel multiscale analysis is developed to assess the buckling behavior of MWCNT-reinforced laminated composites. • Integration of microstructural factors like MWCNT clustering, alignment, and curvature in evaluating composite material performance. • Comprehensive assessment of the influence of moisture and temperature on the buckling performance of MWCNT composites. • Results successfully compared and validated with existing experimental and theoretical data. • Offers significant insights for the design and optimization of MWCNT-reinforced composites. This study introduces a detailed method for analyzing the buckling behavior of laminated composite structures strengthened with multi-walled carbon nanotubes (MWCNTs). We propose a multi-scale analysis that combines analytical and computational techniques to assess the mechanical performance of MWCNT-reinforced composites under combined moisture, temperature, and mechanical stress conditions. The Halpin-Tsai equations are used to calculate the overall stiffness properties of the nano-enhanced matrix, considering factors like MWCNT clustering, alignment, and curvature. Additionally, we incorporate the nanoscopic, size-dependent features of MWCNTs into our model. The Chamis micromechanical formulas are applied to determine the individual elastic properties of the nanocomposite layers, considering the impacts of temperature and moisture. We then explore how variables such as MWCNT content and size, along with temperature and moisture levels, influence the critical buckling load of MWCNT-based laminated composite beams and plates using our multi-scale model. Our results are successfully compared with existing experimental and theoretical data to validate our approach. The developed method offers significant insights for the design and optimization of MWCNT-reinforced composites, potentially benefiting various engineering fields, including aerospace and automotive industries. [ABSTRACT FROM AUTHOR]

Most of the concrete structures in service are unsaturated, estimating the ionic diffusion coefficient of unsaturated cement-based material is of paramount significance to assessment of corrosion of reinforced concrete. Taking account of the contributions from different water configurations at multi-scale (water films, interlayer water, large gel pore (LGP) water and capillary pore water) and the corresponding diffusion mechanisms of each type of water, a micromechanical model for estimating the ionic diffusion coefficient of unsaturated hardened cement paste (UHCP), is developed in this study. Model results show that the interconnectivity of the spheroidal capillary pore water is closely related to the aspect ratio of spheroidal capillary pore, the slender the prolate pore, the higher the interconnectivity of the capillary pore water; when the capillary pore water is totally drained, water films and interlayer water within C-S-H governs the ionic diffusion, the higher the water to cement ratio (w/c), the less the contribution of interlayer water, and the greater the contribution of water film, to ionic diffusion within UHCP. Application on saturated hardened cement paste and UHCP shows the capability of the model to accurately reproduce the experimental results. [ABSTRACT FROM AUTHOR]

In this paper, a micromechanics-based constitutive representation of the deformation-induced phase transformation in polyethylene terephthalate is proposed and verified under biaxial loading paths. The model, formulated within the Eshelby inclusion theory and the micromechanics framework, considers the material system as a two-phase medium, in which the active interactions between the continuous amorphous phase and the discrete newly formed crystalline domains are explicitly considered. The Duvaut–Lions viscoplastic approach is employed in order to introduce the rate-dependency of the yielding behavior. The model parameters are identified from uniaxial data in terms of stress–strain curves and crystallization kinetics at two different strain rates and two different temperatures above glass transition temperature. Then, it is shown that the model predictions are in good agreement with available experimental results under equal biaxial and constant width conditions. The role of the crystallization on the intrinsic properties is emphasized thanks to the model considering the different loading parameters in terms of mechanical path, strain rate and temperature.

Quasi-brittle materials such as rock are rate sensitive materials and their behaviour under dynamic loading is not identical with that under static loading. In this study, numerical Brazilian tensile tests are conducted using a Split Hopkinson Pressure Bar system in an attempt to reproduce the dynamic increase factors (DIF) of the experimental tests. The rock is modelled by a bonded particle system made of spherical particles which interact at the contact points. The numerical results indicate that while the bonded particle system with a simple contact bond model can closely mimic the static behaviour of the sandstone specimens, it lacks what is needed for a rate dependent material. Therefore, a micromechanical model in which the contact bond strength is allowed to vary in proportion to the relative velocity of the involved particles is introduced. It is shown that the modified model can reproduce the physical tests data reported in the literature. In particular, with the application of strength enhancement coefficients in the range of 0–16 × 105, DIF values of 1.1–13 are obtained in the indirect tensile Brazilian tests, and the induced strain rate in the specimen is in 10–1000 s−1 range. Our preliminary study indicates that the model, consistent with the fact reported for the quasi-brittle materials, shows different rate-dependent sensitivity and dynamic strength enhancement in tension and compression. The micromechanical parameters in the proposed model can be adjusted to reproduce the physical rock strength, and that the shape of the reflected and transmitted numerical waves can be modified to approach those in the physical tests. [ABSTRACT FROM AUTHOR]

The microscopic damage initiation characteristic in welded joint greatly determines the subsequent damage evolution and fracture behavior of aluminum alloy tailor-welded blank (TWB) during plastic forming. In this study, the interactive dependence of void nucleation on microstructure and stress state in the welded joint of a 2219 aluminum alloy TWB was quantitatively explored by in-situ SEM testing. Moreover, a micromechanical model based on actual microstructure was adopted to reveal the underlying mechanisms from the perspective of microscopic heterogeneous deformation. The results showed that three void nucleation mechanisms, including particle-cracking, interface-debonding and matrix-cracking, coexisted in the deformation at different microstructure regions and stress states. The nucleation strain of each mechanism mainly depended on the particle volume fraction, grain size and stress triaxiality. Besides, the proportions of particle-cracking and interface-debonding greatly varied with the grain size and particle volume fraction, and the variation law changed with the stress state. The proportion of matrix-cracking had a weak dependence on the microstructure, while increased with the stress triaxiality decreasing. It made the damage initiation in aluminum alloy welded joint transit from particle-cracking dominance to matrix-cracking dominance with the stress triaxiality decreasing. The micromechanical modeling results suggested that the changes of evolutions and distributions of Mises stress in particle, hydrostatic stress at interface and plastic strain in matrix with microstructure and stress state were responsible for the above effects. [Display omitted] • Interactive dependence of void nucleation on microstructure and stress state in welded Al-alloy blank was revealed. • Nucleation strain and proportions of voids depend on the particle volume fraction, grain size and stress triaxiality. • The dependence of proportions on microstructure varies with the stress triaxiality. • Void nucleation changes from matrix-cracking to particle-cracking dominance with stress triaxiality increasing. • Nucleation features are explained by the microscopic heterogeneous deformation characteristics. [ABSTRACT FROM AUTHOR]

This study is aimed at investigating short- and long-term aged properties of glass fibre (GF)-reinforced asphalt mixtures using indirect tensile strength (ITS) and associated fracture energy, moisture susceptibility, creep compliance, resilient modulus, and indirect tension continuous and discontinuous (IDT) fatigue tests. Also, to portray the influence of fibre reinforcement at micro level, a micromechanical finite element model (MFEM) was built utilising representative volume element (RVE) to consider the effect of fibre dose, length, and dispersion (fully aligned or random) on the mechanical characteristics (or stress-strain curve) of the composite under unidirectional strain perturbation. Based on the study results, for the same binder, compared to shorter fibre (i.e. 6-mm length), the application of 12-mm GF to the mixtures showed unnoticeable change in the short- and long-term properties of the reinforced mixtures. On the whole, the GF can impart positive characteristics to the asphalt mixture such as increase strength, resistance to rutting, less susceptibility to moisture damage, retard fatigue cracking, enhance healing capability, and combat adverse aging changes. Unlike the effect of fibre length, the numerical model proved that the orientation and concentration of GF showed noticeable influence on the mechanical response of the composite. Overall, using the GF in asphalt mixtures can help produce durable bituminous pavements. Although the present study investigated the GF-reinforced bituminous materials from performance stand point, one can speculate that building GF-reinforced pavements is more costly initially compared to unreinforced pavements however the benefits may be received over time by extending service life and saving the maintenance cost of the bituminous pavement. [ABSTRACT FROM AUTHOR]

This work applies a higher order thickness-stretched model for the electro-elastic analysis of the composite graphene origami reinforced square plate sandwiched by the piezoelectric/piezomagnetic layers subjected to the thermal, electric, magnetic and mechanical loads. The plate is manufactured of a copper matrix reinforced with graphene origami where the effective material properties are calculated based on the micromechanical models as a function of volume fraction and folding degree of graphene origami, material properties of matrix, reinforcement, and local temperature. The governing equations are derived using the virtual work principle in terms of the bending, shear and stretching functions, in-plane displacements, electric, and magnetic potentials. The numerical results including various displacement components, maximum electric, and magnetic potentials are presented with changes of volume fraction, folding degree of reinforcement, electrical, magnetic, and thermal loading. A verification investigation is presented for approve of the methodology, and the solution procedure. The main novelty of this work is simultaneous effect of the thickness stretching and the multi-field loading on the electromagnetic bending results of the sandwich plate. Another novelty of this work is usage of graphene origami nano-reinforcement as a controllable material in a sandwich structure subjected to multi-field loadings. The results show an increase in bending, shear, and stretching deflections with an increase in electromagnetic loads, and folding degree as well as a decrease in volume fraction of reinforcement., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author(s).)

Functionally graded porous structures (FGPSs), characterized by a continuous spatial gradient in both porosity and material properties, have been considered as the new generation lightweight structures. Research activities on FGPSs have grown rapidly in recent years. This paper is devoted to review the existing research works on FGPSs and to highlight the important advances in this emerging area. It consists of: (i) a brief introduction of porous materials and Functionally graded porous materials (FGPMs); (ii) an elaboration of the key factor and micromechanical models related to material properties of FGPMs; (iii) a comprehensive review of mechanical analysis of FGPSs; (iv) a detailed discussion of the main challenges and future research directions; (v) a conclusion. [ABSTRACT FROM AUTHOR]

The aim of this study is to analysis the tensile deformation behavior of 3D printed unidirectional continuous fiber reinforced thermos-plastic composites (UD-CFRTP). Tensile experiments were performed to obtain the deformation curves and tensile properties of composites specimens. It is found that the reinforcement fiber bundles of specimens bearing the load non-synchronously. Meanwhile, with the fiber content change, the deformation form could be different. An improved micromechanical model was proposed to investigate the influence of non-synchronous phenomenon and fiber content on the deformation behavior. The fiber content is measured by the number of reinforcement fiber bundles instead of fiber volume fraction in this model. Based on this model, the deformation behavior and tensile properties of test specimens with different fiber bundles number were analyzed in detail. The analytical results about deformation behavior and tensile properties show a good agreement with experiment results. [ABSTRACT FROM AUTHOR]

This paper presents a micromechanical model to predict the time-dependent damage and deformation behavior of an orthogonal 3-D woven SiC fiber/BN interface/SiC matrix composite under constant tensile loading at elevated temperature in vacuum. In-situ observation under monotonic tensile loading at room temperature, load–unload tensile testing at 1200 °C in argon, and constant load tensile testing at 1200 °C in vacuum were conducted to investigate the effects of microscopic damage on deformation behavior. The experimentally obtained results led to production of a time-dependent nonlinear stress–strain response model for the orthogonal 3-D woven SiC/SiC. It was established using the linear viscoelastic model, micro-damage propagation model, and a shear-lag model. The predicted creep deformation was found to agree well with the experimentally obtained results. [ABSTRACT FROM AUTHOR]

Several experimental studies, carried out on anisotropic rocks, have evidenced that even though strains, due to isotropic loading and/or internal fluid pressure, are strongly anisotropic, the resulting Biot's tensor is almost isotropic. Those results were found on two different rocks: a clay rock (France—Bure argillite) and a sandstone from the Vosges region (France). Such (a priori) surprising results led us to develop micromechanical modelling in which anisotropy comes either from an anisotropic solid matrix (and isotropic pore space) or from an anisotropic pore space (and isotropic solid matrix). The obtained results have shown that for both cases the Biot's tensor is virtually isotropic or presents a very weak anisotropy. This unambiguously supports the fact that a strongly anisotropic porous material is compatible with experimental measurements of isotropic (or quasi isotropic) Biot's tensor. [ABSTRACT FROM AUTHOR]

Unsuitable surface quality is frequently observed in the machining of composites due to their heterogeneity and anisotropic properties. Thus, minimizing the machining damages requires a thorough understanding of the machining process. In this study, two different finite element models were developed using Abaqus/Explicit to simulate the cutting process of unidirectional carbon fiber-reinforced polymer: (i) a macromechanical model based on the homogenization approach and (ii) a micromechanical model in which the composite constituents were treated separately. The effects of CFRP mechanical properties, the energy of breaking and hourglass control were analyzed using a macromechanical model. The results revealed that CFRP properties and the numerical parameters highly influenced the cutting process. A comparative study was also performed between the macromechanical and the micromechanical models to study the mechanisms of chip formation. It was demonstrated that the material removal mechanisms for both models are in good agreement with the experimental observations for different fiber orientation angles. [ABSTRACT FROM AUTHOR]

It is shown on the basis of the micromechanical tensile strength model of a polymer composite, that the strength of an interfacial region material in polymer–high modulus filler nanocomposites decreases as its thickness increases, which contradicts the case of adhesion between two polymers, in which the thickness of an interfacial region is linearly dependent on the degree of interfacial adhesion. A fractal model of phase interactions is used to estimate the threshold values of the nanocluster volume ratio of an epoxy polymer matrix and the metal nanoparticles of a filler, with the mechanical stress transfer from the polymer matrix to the filler being weakened upon reaching these values. It is shown that exceeding a threshold value of the filler volume ratio violates the aggregate stability of the filler and reduces the values of the dimensionless parameter of the micromechanical model, which characterizes the degree of interfacial adhesion. With a further increase in the filler volume ratio, the values of this parameter become negative, while the composite strength virtually does not increase. [ABSTRACT FROM AUTHOR]

This work presents an analytical approach to investigate the mechanical buckling of functionally graded material (FGM) thin conical panels surrounded by Winkler–Pasternak foundation and exposed to thermal environments. The material properties of FGMs are assumed to be temperature-dependent and graded only in the thickness direction according to the power-law, sigmoid and the exponential distribution of volume fraction. Eight well-known types of micromechanical models, namely Voigt, Reuss, Mori–Tanaka, Hashin–Shtrikman, modified Wakashima–Tsukamoto, Halpin–Tsai, Tamura and LRVE estimations, are studied to determine the effective two-phase FGM material properties as a function of the particles' volume fraction considering thermal effects. Further, it is been supposed that the FG conical panel is heated uniformly, linearly and nonlinearly through the thickness. The nonlinear temperature distribution is obtained based on Fourier's law by applying a semi-analytical procedure. The fundamental relations and the basic equations are derived by using Love's thin shell theory. Finally, the numerical results are provided to reveal the effect of explicit micromechanical model, FGM profile, temperature distribution with various thermal boundary conditions, foundation conditions and the geometric parameters on the stability of these panels. Additionally, the critical buckling load is compared with that of FG truncated conical shells, cylindrical panels and the cylindrical shells. [ABSTRACT FROM AUTHOR]

The change of the mechanical properties of granular materials with pressure is an important topic associated with many industrial applications. In this paper we investigate the influence of hydrostatic pressure (P e) on the effective bulk compressibility (C eff) of a granular material by applying two modified theoretical approaches that are based on contact mechanics and micromechanics, respectively. For a granular material composed of rough grains, an extended contact model is developed to elucidate the effect of roughness of grain surfaces on bulk compressibility. At relatively low pressures, the model predicts that the decrease of bulk compressibility with pressure may be described by a power law with an exponent of -1/2 (i.e., C eff ∝ P e −1/2), but deviates at intermediate pressures. At elevated pressures beyond full contact, bulk compressibility remains almost unchanged, which may be roughly evaluated by continuum contact mechanics. As an alternative explanation of pressure-dependent bulk compressibility, we suggest a micromechanical model that accounts for effects of different types of pore space present in granular materials. Narrow and compliant inter-granular cracks are approximated by three-dimensional oblate spheroidal cracks with rough surfaces, whereas the equant and stiff pores surrounded by three and four neighboring grains are modeled as tubular pores with cross sections of three and four cusp-like corners, respectively. In this model, bulk compressibility is strongly reduced with increasing pressure by progressive closure of rough-walled cracks. At pressures exceeding crack closure pressure, deformation of the remaining equant pores is largely insensitive to pressure, with almost no further change in bulk compressibility. To validate these models, we performed hydrostatic compression tests on Bentheim sandstone (a granular rock consisting of quartz with high porosity) under a wide range of pressure. The relation between observed microstructures and measured pressure-dependent bulk compressibility is well explained by both suggested models. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Deformation band localization modes, uniform tensile strength, and uniform elongation of Ferrite-Martensite Dual-Phase (DP) steels are analyzed by finite element (FE) study. Treating the microstructure inhomogeneity as the sole cause of imperfection, failure initiation is predicted as the natural fallout of plastic instability caused by load drop because of localized plastic strain in the Representative Volume Element (RVE) during straining. Strain partitioning between two phases (ferrite matrix and martensite island) are investigated on RVEs, and it reveals that the increase of martensite yield stress decreases the plastic deformation and increases the stress state in martensite. Whereas, a decrease in martensite island volume fraction (Vm) results in the reduction of plastic deformation and stress state in the island. Studies are then carried out to investigate the effects of the ferrite-martensite flow properties and martensite volume fraction on the macroscopic tensile deformation behavior and band localization of DP steels. Micromechanical based FE simulation results emphasize that an increase in initial yield strength and volume fraction of martensite increases the ultimate tensile stress (UTS) with the decrease in uniform elongation. Similarly, as the hardening rate of ferrite increases, it increases the ultimate tensile stress (UTS) and uniform elongation. Additionally, deformation band localization modes alter from inclined to perpendicular to the loading axis with an increase in martensite volume fraction and initial yield strength of martensite. The knowledge of this work can be used to design DP steels with desired mechanical properties. [ABSTRACT FROM AUTHOR]

High temperature creep and fatigue properties are important characteristics of SiC/SiC composites. In this work, dwell-fatigue tests were conducted at 1300 °C for 3D-braided SiC/SiC with and without coatings, and experimental results of dwell-fatigue tests were analyzed together with results of fatigue and creep tests. Then, general quantitative method was adopted to explain the deformation and rupture behaviors of SiC/SiC in creep, fatigue and dwell-fatigue tests. Micromechanical creep model could effectively simulate deformation behavior when the maximum load was under matrix cracking stress. Stress transfer behavior of constituents during creep and fatigue tests provided insights into the difference in macro time/cycle dependent deformation. Next, by incorporating damage evolution model which represents oxidation assisted unbridged crack growth, deformation acceleration in tertiary stage of creep was successfully simulated. Finally, SiC/SiC lifetimes under all fatigue, creep, and dwell-fatigue loads were predicted considering matrix crack propagation and fiber strength degradation. Simulated results correlated well with experimental data, verifying the effectiveness of micromechanical model to predict the creep and fatigue behaviors of SiC/SiC composites at high temperatures. [ABSTRACT FROM AUTHOR]

In this paper, micromechanical models are used to predict the 3D viscoelastic behaviour of asphalt mixtures (with volume fraction of aggregate particles up to 87%) from the mechanical properties of their constituents. To fulfil the objective of study, complex modulus tests are conducted on bituminous materials at three different scales: bitumen, asphalt mastics and asphalt mixtures. The volume fraction of particles varies from 0% (bitumen) to 15%, 25%, 35% (asphalt mastic) and up to 87% (asphalt mixture). In the experimental program, complex modulus of bitumen, asphalt mastic and asphalt mixtures at different temperatures, frequencies are measured. For asphalt mixtures, measurements of complex Poisson's ratio are also performed. The rheological model 2S2P1D is used to simulate the 3D viscoelastic behaviour of tested bituminous materials. From the experimental results and simulations, two micromechanical models (self-consistent and generalized self-consistent model) are used to predict the complex modulus and complex Poisson's ratio of asphalt mixtures. The obtained results show that both micromechanical models give the good prediction of complex modulus for asphalt mastic where the volume fraction of aggregate particles is lower than 35%. At asphalt mixture scale where the volume fraction of particles is up to 87%, only simulation using the generalized self-consistent model can show good results. The prediction using the generalized self-consistent model at the mixture scale can be applied for both complex modulus and complex Poisson's ratio. In addition, the prediction of complex modulus and complex Poisson's ratio of asphalt mixtures becomes better when the asphalt mastic instead of bitumen is considered as viscous matrix. ● Relationships between 3D LVE properties of asphaltic materials are built. ● Large volume fraction of filler/aggregate is considered (from 0 up to 87%). ● Rheological model parameters are linked with volume fraction of filler/aggregates. ● Complex modulus/complex Poisson's ratio is predicted using micromechanical models. ● Asphalt mastic instead of bitumen is considered as the matrix phase of mixture. [ABSTRACT FROM AUTHOR]

• Effective thermoelectric properties considering interfacial resistance are reached. • Effective thermoelectric properties under large temperature difference are derived. • Effect of inclusion's shapes on effective thermoelectric properties is discussed. • Effect of inclusion's sizes on effective thermoelectric properties is discussed. • Theoretical model is well validated by finite element analysis. The effective design of thermoelectric composites is of great significance in improving performance of thermoelectric composites. Herein, we develop a homogenization theory to predict the effective thermoelectric properties of thermoelectric composite containing ellipsoidal inclusions whereby interfacial thermal and electrical resistances are considered. Firstly, the closed-form representations of the effective thermoelectric properties are derived under the assumption of a small temperature difference. Then the effective properties of the thermoelectric composite subjecting to a large temperature difference are obtained by cutting the composite to a serial connection of pieces with a small temperature difference. The relationship between the interfacial resistances and the effective properties of thermoelectric composites is discussed systematically under the different conditions of the aspect ratio, volume fraction, size of inclusion and temperature difference in the composite. Our theoretical predictions well match the effective properties obtained from finite element analysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • This improved micromechanical model can consider contributions of microstructure, multiscale fibers, thermal cracking, and interfacial thermal resistance between sands and the matrix. • The proposed model confirms that thermal cracking beyond 400 °C can significantly influence the thermal conductivity. • The addition of multi-scale fibers can increase the thermal conductivity of high performance concrete by around 10% An improved micromechanical model to estimate the thermal conductivity of multi-scale fiber reinforced ultra-high performance concrete (MSFUHPC) subjected to elevated temperatures is formulated in this study. This model considers the contributions of microstructure, multiscale fibers, water/cement ratio, thermal dehydration of hydrates, thermal cracking, interfacial thermal resistance, heating rate and temperature dependent thermal conductivity of each phase. To verify the proposed model, comparisons with experimental data on MSFUHPC specimens are carried out. Accordingly, factors affecting the thermal conductivity of MSFUHPC are discussed through the proposed model. Results suggest that blending multi-scale fibers and increasing the sand content can significantly enhance the thermal conductivity of MSFUHPC. While adding cenosphere particles can reduce the thermal conductivity. Overall, the thermal conductivity of MSFUHPC exhibits a decreasing trend with temperature. Meanwhile, thermal cracking occurs beyond 400 °C can remarkably decrease the thermal conductivity of MSFUHPC. A higher interfacial thermal resistance between sands and the matrix can result in a lower thermal conductivity. It is also found that thermal conductivity mainly depends on the maximum temperature experienced rather than the heating rate. [ABSTRACT FROM AUTHOR]

This study presents a new micromechanical model to investigate the effects of thermal residual stresses and interfacial properties on the transverse behaviors of SiC/Ti composites with different microstructures. In this model, the fiber-matrix interface is modeled by the bilinear cohesive zone model. The interface model is introduced into the generalized method of cells, which has the advantage of computational accuracy and efficiency. At the same time, the generalized method of cells is extended to consider thermal residual stresses within the fiber and matrix phases. Thermal residual stresses are found to have a significant influence on the transverse behaviors of the composites. Compared with the perfect interface, the transverse behaviors of the composites with weak interface bonding are much lower. Moreover, with the increase of fiber fraction, the stiffness of the composites increases before debonding occurs while the saturation stress decreases. The predicted results using the circular fiber model and considering thermal residual stresses are more consistent with the experimental values compared with the results using the square or elliptical fiber model. When the stress concentration factor is considered and the interface is weakly bonding, the strength predictions are much better than the results using the perfect bonding.

• Three micromechanical models was selected to predict the asphalt mastic behavior. • GSCG gave the most accuracy modulus prediction of mastic with low filler fraction. • J-C model cannot predict modulus of mastic with high filler fraction. • Phy-C gave a good modulus prediction for mastic with moderate filler fraction. • Prediction accuracy deteriorated severely with the increase of filler fraction. Micromechanical models have been used since the 1990s to predict the properties of asphalt mastic. However, most of these models are found to be unsatisfactory in predicting the mastic's properties because the models were derived from the research of particle-filled composites that did not take into account the asphalt-filler physico-chemical interactions and particle interactions. In this paper, three micro-mechanical models for predicting the complex shear modulus master curve of asphalt mastic are evaluated: the generalized self-consistent scheme model, the four-phase micro-mechanical model, and the particle interaction model. All three micro-mechanical models are based on the mechanical properties of their constituent materials as well as the filler-asphalt physiochemical interactions and the particle interactions. Two virgin asphalt binders and two polymer modified asphalt binders were selected to fabricate 16 mastics of four different filler volume fractions. The accuracy of prediction was evaluated by comparing the relative differences between the experimental complex shear modulus master curves and that predicted by the models. The results suggest that (1) the generalized self-consistent scheme model have a satisfactory prediction at a low filler volume fraction, but their accuracy is significantly affected by frequency; (2) the particle interaction model cannot calculate the complex shear modulus of mastic with a filler volume fraction of more than 0.53; (3) the four-phase model shows a precise forecast of complex shear modulus for mastic with moderate and high filler volume fractions; and (4) for all of the three models, the deviations increase severely with the increase of the filler volume fraction. [ABSTRACT FROM AUTHOR]

A distinct perspective of using the hybrid composite patches with varying stiffness for repair of a cracked Al 6061-T6 plate and its influence on repair performance is presented. The hybrid composite patches of carbon and glass fibers are considered. The volume fraction of constituents is selected in accordance with the required stiffness ratio. Numerical analysis is performed to evaluate the J-Integral, reduction factor of SIF and interfacial stresses. Patch hybridization has restricted the J-Integral and shown positive impact on interfacial stresses at the edges. The obtained results indicate that the hybrid composite patches have ensured alternative and effective repair solution. [ABSTRACT FROM AUTHOR]

The quasi‐static, dynamic compression experiments and micromechanical model were employed to declare the dynamic compressive response of ZrB2–20%SiC composite at high‐strain rates. The quasi‐static compressive strengths were measured to determine the range of initial microcrack length in ZrB2–20%SiC composite. The effects of the strain rate on dynamic compressive strength, critical stain, as well as fracture mechanisms were discussed based on experimental results. Dynamic mechanical properties of ZrB2‐based composites display obvious strain rate dependence. The dynamic increase factor in the compressive strength shows a rapid increase above a transition strain rate of 1228 s−1. Moreover, a micromechanical model considering initial microcrack lengths is used to predict dynamic compressive strengths, which agree with the experimental results. Additionally, the critical strain has a linear increase tendency with the increase of strain rate. The dynamic compressive fracture mechanism of ZrB2–20%SiC composite is relative to the combination effect between strain rate and microstructure. The size of flaw distribution is critical below the transition strain rate resulting in bigger fragments, whereas the flaw density is primary with more and smaller fragments above the transition strain rate. [ABSTRACT FROM AUTHOR]

• This work deals with biaxial low-cycle fatigue (LCF) response of a micromechanical model. • The damage activation/deactivation phenomenon was formulated at the macroscale. • A new hybrid cycle jump approach was proposed to minimize the computation costs through. • The proposed development is able, for example, the concept of new hybrid cycle jump. • The model response highlights that the greater, the number of cycles, the greater, the gain in computation time but the less, the accuracy. In this work, a new hybrid cycle jump approach was proposed to predict the low-cycle fatigue (LCF) response using a well-established micromechanical model. The damage activation/deactivation phenomenon was formulated at the macroscale. Using the concept of rate independent plasticity with the small strains assumption, the damage deactivation effect on the LCF response and its lifetime was accurately described by the model under simple and complex cyclic loading paths. Three algorithms namely, Taylor 1st and 2nd order and predictor-corrector were utilized for estimating the model response after each cycle jump. An optimum precision factor (ρ) value was defined and then tested via a suitable compromise between computation times and accuracy. In order to numerically determine the cyclic jump length (ΔN), a new hybrid approach was developed based on the overall von Mises stress and the overall damage together with monitoring the accumulated slip. Then, a comparative study revealed that the predictor-corrector algorithm was opted due to its robustness compared to the other algorithms. The numerical study was carried out using two different cyclic loading configurations. One was under simple tension-compression and the other under complex tension-torsion with 90° out-of-phase angle. The model response was described under two distinct states: (i) cycle-by-cycle and (ii) cycle jump concept. For each numerical state, the overall and local responses were recorded. With the new hybrid cycle jump approach, the model response highlights that the greater, the number of cycles, the greater, the gain in computation time but the less, the accuracy. For example, in TC for N f = 10,000 cycles, a recorded gain in computation time was attained 77% (against 95% by means of cycles number) with a relative error of 4%; whereas in TT90 of N f = 2124, the computation gain became 43.4% (and 73.4% with respect to number of jumped cycles) with a relative error of 3%. [ABSTRACT FROM AUTHOR]

In this paper, a micromechanical model is proposed to study the elastoplastic behavior of the Callovo-Oxfordian (COx) argillite. Three scales (i.e., macroscopic, mesoscopic and microscopic) are considered. At the mesoscopic scale, the COx argillite is regarded as a three-phase composite with clay as matrix and calcite and quartz as reinforcements. At the microscale, the clay matrix is a porous medium constituted by clay minerals and interparticle pores. The porous clay is described with an extended Gurson-Tvergaard-Needelman (EGTN) model while the calcite and quartz reinforcements are described with the linear isotropic elastic model. The macroscopic behavior of the COx argillite is determined by adopting the Hill's incremental formulation. All the numerical aspects including: (1) the integration of the EGTN model with the backward Euler method; (2) the derivation of the corresponding consistent tangent moduli from a new point of view; (3) the realization of the homogenization process, are fully described. The proposed micromechanical model is validated from two aspects. The first aspect is the numerical predictions against the finite element (FE) computations performed on a two-phase unit cell, where the key steps related to the modelling are presented. The second aspect is the comparisons between the numerical predictions and experimental data. [ABSTRACT FROM AUTHOR]

Highlights • A multiscale micromechanical homogenization framework is proposed for fluid-filled porous materials. • The overall elastic properties of the fluid-filled porous materials are determined in the framework. • The effects of pore distribution and fluid pressure on the effective elastic properties are quantified. • By considering the fluid diffusion from macro- to micro-scale pores, evolution of the effective properties is predicted. Abstract Fluid-filled porous materials are widely encountered in natural and artificial systems. A comprehensive understanding of the elastic behavior of such materials and its dependence on fluid diffusion is therefore of fundamental importance. In this work, a multiscale framework is developed to model the overall elastic response of fluid-filled porous materials. By utilizing a two-dimensional micromechanical model with porosity at two scales, the effects of fluid diffusion and the geometric arrangement of pores on the evolution of effective properties in fluid-filled porous materials are investigated. Initially, for a single-porosity model the effective elastic properties of the dry and fluid-filled porous materials with ordered pores are obtained theoretically by considering a geometrical factor, which is related to the distribution of pores in the matrix. Model predictions are validated by finite element simulations. By employing a double-porosity model, fluid diffusion from macro- to micro-scale pores driven by a pressure gradient is investigated, and the resulting time-dependent effective elastic properties are obtained for both constant pressure and constant injection rate conditions. It is found that the presence and diffusion of pressurized pore fluid significantly affect the elastic response of porous materials, and this must be considered when modeling such materials. It is expected that the proposed theoretical model will advance the understanding of the fluid-governed elastic response of porous materials with implications towards the analysis of geophysical, biological and artificial fluid-filled porous systems. Graphic abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract Evidences of both sluggish eutectoid and active eutectoid (not suppressible under rapid cooling) transformations have been found for the first time in a single hyper-eutectoid Ti-Cu alloy. Both of these types of eutectoid reactions have been investigated in detail, at different length scales, by coupling scanning electron microscopy (SEM),transmission electron microscopy (TEM) and atom probe tomography (APT). The unique three phase crystallographic relationship between the parent β (bcc) and the two product phases, α (hcp) and Ti 2 Cu, has been established. The extent of partitioning of the solute (Cu) between the two product phases has been determined by APT and is rationalised in terms of thermodynamic considerations. Based on the observed lattice site correspondence and the extent of solute partitioning, a possible mechanism of active eutectoid transformation is proposed. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]