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This study examines the effects of temperature and fiber and matrix diffusivities on the diffusion of fluid in glass fiber-reinforced polymer composites. Glass fiber-reinforced polymer thin plates were immersed in deionized water at two temperatures: room temperature and 50℃. During the diffusion process, the overall mass changes and dimension changes were recorded, which relate to the volumetric change and the through-the-thickness strain. Different constitutive models are considered in order to understand the diffusion of fluid through the glass fiber-reinforced polymer plates. The macroscopic models of this work, Fickian and Gurtin coupled deformation–diffusion, are first considered in order to describe the macroscopic diffusion behaviors. Two microscopic models that include fiber volume contents and diffusivities of the constituents (fiber and matrix) are then considered in order to gain fundamental insight into the effects of microstructural morphologies and constituents' diffusivities on the diffusion process in the glass fiber-reinforced polymer specimens. [ABSTRACT FROM AUTHOR]

Some manufacturing processes of polymeric materials, such as injection molding or film blowing, cause the final product to be highly anisotropic. In this study, the mechanical behavior of drawn polyethylene (PE) tapes is investigated via micromechanical modeling. An elasto‐viscoplastic micromechanical model, developed within the framework of the so‐called composite inclusion model, is presented to capture the anisotropic behavior of oriented semicrystalline PE. Two different phases, namely amorphous and crystalline (both described by elasto‐viscoplastic constitutive models), are considered at the microstructural level. The initial oriented crystallographic structure of the drawn tapes is taken into account. It was previously shown by Sedighiamiri et al. (Comp. Mater. Sci. 2014, 82, 415) that by only considering the oriented crystallographic structure, it is not possible to capture the macroscopic anisotropic behavior of drawn tapes. The main contribution of this study is the development of an anisotropic model for the amorphous phase within the micromechanical framework. An Eindhoven glassy polymer (EGP)‐based model including different sources of anisotropy, namely anisotropic elasticity, internal stress in the elastic network and anisotropic viscoplasticity, is developed for the amorphous phase and incorporated into the micromechanical model. Comparisons against experimental results reveal remarkable improvements of the model predictions (compared to micromechanical model predictions including isotropic amorphous domains) and thus the significance of the amorphous phase anisotropy on the overall behavior of drawn PE tapes. © 2019 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 378–391 Oriented semi‐crystalline polymers have an oriented amorphous phase in addition to the oriented crystallographic structure. It was found that the role of an oriented amorphous phase on the strongly anisotropic mechanical behavior of an oriented semi‐crystalline polymer is not negligible. A multi‐scale two‐phase (crystalline‐amorphous) micro‐mechanical model is presented in which the behavior of the amorphous phase is described anisotropic elasto‐viscoplastically. [ABSTRACT FROM AUTHOR]

Abstract The metals with gradient nanostructures possess exceptionally superior mechanical properties. Here, the gradient-nanotwinned 304 stainless steel wires are fabricated by surface mechanical attrition treatment (SMAT) with a range of process time. The quasi-static tensile tests and dynamic compressive tests are conducted to examine the constitutive response of gradient-nanotwinned 304 stainless steels under different loadings. The experimental measurements show that under static and dynamic loadings, their mechanical properties are closely related to the SMAT process time. With an increase in the process time, their yield strength is improved, while their ductility is weakened. Furthermore, a theoretical model is proposed to describe the static and dynamic constitutive relation of gradient nanotwinned 304 stainless steels. The micromechanical model of nanotwinned composite is developed to characterize the constitutive relation of the material with nanograins embedded in nanotwinned matrix in depth. For the constitutive relations of each phase in nanotwinned composite structure, the athermal behaviors of dislocations are only considered in describing the flow stress under the static loadings. The size-dependent athermal flow stress and rate-dependent thermal flow stress are both involved under the dynamic loadings. The theoretical simulations demonstrated that the mechanical response of gradient-nanotwinned 304 stainless steels under different loadings can be successfully characterized by the presented model. A good agreement is obtained between the numerical results and experimental measurements. Furthermore, the mechanical properties of gradient-nanotwinned 304 stainless steels are forecasted for the various distribution of twin spacing along the depth. The results in this work are helpful for optimizing the static and dynamic mechanical performance of the gradient-nanostructured metallic materials through controlling microstructural size and distribution. Highlights • Gradient-nanotwinned 304SS are prepared by the surface mechanical attrition treatment. • Static and dynamic mechanical properties of gradient-nanotwinned 304SS are measured. • A mechanism-based theoretical model for static and dynamic mechanical behaviors is developed. • The constitutive relations of gradient-nanotwinned 304SS are completely described. • The simulations show good agreement with experimental results. [ABSTRACT FROM AUTHOR]

Abstract A new three-dimensional (3D) micromechanical model is proposed to simulate the arbitrary multidirectional carbon fiber reinforced polymer (CFRP) composite laminates. Carbon fiber is assumed as transversely isotropic and linear elastic, matrix is assumed as isotropic and elastic–plastic. Maximum strain criterion is used to describe the failure of fiber and matrix. The stresses, strains and damage are described in the fiber and matrix levels, but the debonding between the fiber and matrix and the delamination between two plies are not modeled in the present analysis. Numerical analyses of nonlinear mechanical behavior of angle-ply [±θ] 2s under tension are conducted to verify the validity of the present micromechanical model. Numerical results of nonlinear mechanical behavior, negative Poisson's ratio through the thickness direction, and stress distribution on the free edge show good agreement with previous experimental and analytical results. [ABSTRACT FROM AUTHOR]

Abstract This paper calibrates micromechanical fracture models for duplex stainless steel in order to study its fracture behaviour under seismic loading, characterized by large strain ultra low cyclic conditions. In this investigation, smooth round bars and notched round bars were subject to monotonic and cyclic loading. Monotonic and cyclic loading constitutive models were calibrated against smooth round bar test tests. The fracture toughness parameters of the void growth model (VGM), the stress modified critical strain (SMCS) model and the cyclic void growth model (CVGM) were calibrated against the notched round bar tests. Furthermore, the skeleton curve, hysteresis loop and characteristic length of duplex stainless steel were also investigated. The test results indicate that duplex stainless steel exhibits cyclic hardening behaviour under cyclic loading, and the subsequent numerical simulation successfully captured this behaviour. The toughness parameters of duplex stainless steel are generally higher than those for carbon steel grades Q345B and Q460, which demonstrates that duplex stainless steel has better toughness. All the experimental results provide useful data for the prediction of ultra low cycle fatigue (ULCF) fracture of duplex stainless steel. Highlights • We establish the constitutive model of duplex stainless steel under cyclic loading. • We calibrate the fracture toughness parameters of microscopic mechanism model. • The fracture toughness parameters are related to the material itself. • Duplex stainless steel has better ductility than Q345 and Q460. • Duplex stainless steel is more sensitive to ULCF than Q345 and Q460. [ABSTRACT FROM AUTHOR]

The effect of water on the hydromechanical behavior of unsaturated granular materials has been studied with a micromechanical model based on thermodynamic principles. A general framework based on the theory of thermodynamics with internal variables for constructing thermodynamically consistent multiscale constitutive relations for unsaturated granular materials has been developed. Within this framework, the microscopic total Helmholtz free energy has been separated between a mechanical and a hydraulic part, each of which is a function of either the elastic displacement or the capillary bridge volume and the distance between particles at the microscale. The inter-particle dissipation of energy, assumed to be frictional in origin, is a function of the incremental plastic displacements at the microscale. Both the microscale Helmholtz free energy and the dissipative energy have been volumetrically averaged to obtain the homogenized energy functions at the macroscale. In accordance with the suggested multiscale thermomechanical framework, a micromechanical model has been constructed to describe the behavior of partially saturated granular soils. This model has considered the deformation of soil skeleton by applying a Coulomb-type criterion at the inter-particle contacts. The hydraulic potential is made to be dependent on the size of the particles and is derived through use of the expression for the water retention curve by assuming that liquid bridges are isotropically distributed within the specimen. The performance of the suggested model has been demonstrated through numerical simulations of the behavior of sand under various degrees of saturation and a wide range of mechanical loadings. [ABSTRACT FROM AUTHOR]

• A micromechanical model for bioinspired nanocomposites was established with the interphase explicitly considered. • A compact formula of the effective modulus was derived, showing a load sustain dominant term and a term reflecting the load transfer. • The significance of the interphase influence was revealed to be dependent and tuned by a non-dimensional parameter β II. The stagger-aligned structures including "brick-and-mortar" are well-known as a generic feature in biological tough and strong nanocomposites, leading to bioinspired high-performance composites. Experimental observations have shown that the region between the stiff reinforcements and the soft matrices is not an interface of zero thickness but a nanoscale interphase. The interphases are believed to play an important role in the overall mechanical achievements; however, related theoretical models are still yet to be developed for decoding the interphase-related mechanisms. Based on the shear-lag theory, this work establishes a theoretical model for the staggered nanocomposites explicitly considering the interphase. In particular, a compact formula of the nanocomposites' effective modulus (E c) is derived, clearly showing the relations to a load-sustain dominant term (E R) and a term (E S) reflecting the load-transfer through shear deformation, as well as other microstructural and material parameters. With comparison to results by the finite element analysis and other existing relevant models, our model exhibits superior accuracy and simplicity, as well as general applicability. Furthermore, our model reveals an interesting working mechanism of the interphase: E c is sensitive to the interphase properties for the shear transfer parameter (β II ) being around 1.5–7.5, as the interphase undertakes both stress-transfer and stress-sustaining roles. The model and findings shed light on the role of the interphase in enhancing load-bearing biological composites and provide new insights in optimizing bioinspired nanocomposites through modulating the interphase properties. [ABSTRACT FROM AUTHOR]

• The combination of GO and steel fiber makes UHPC have the best fracture property. • GO improves the pull-out property of steel fiber by reinforcing the UHPC matrix. • The prediction model of UHPC fracture energy based on micromechanics is established. This paper aims to achieve multi-scale crack control of concrete by using graphene oxide (GO) and macroscopic steel fiber in combination, and to reveal the multi-scale collaborative reinforcement mechanism of GO and steel fiber. A three-point bending fracture mechanics test was employed to analyze the macroscopic fracture properties of ultra-high performance concrete (UHPC) reinforced by GO, and a single fiber pull-out test was utilized to assess the impact of GO on the fiber–matrix interface properties. The results showed that 0.04% GO reinforced UHPC had the best fracture property, and steel fiber and GO showed good synergistic crack control effect. GO directly acted on controlling the cracking of concrete matrix at the nanoscale, thus improving the fracture energy of UHPC matrix by 14% from 73.08 N/mm to 83.39 N/mm. This micro-scale matrix reinforcement provided by GO further improved the pull-out property of steel fibers, and the pull-out energy dissipation of straight steel fibers and hook-end fibers was increased by 43.7% and 31.5%. A micromechanical prediction model for fracture energy of straight steel fiber UHPC was established, which could construct the quantitative relationship between UHPC fracture energy and micromechanical parameters. The model showed that the initial fiber–matrix bond strength (τ 0) and slip hardening coefficient (k 0) had a powerful influence on the UHPC fracture energy. [ABSTRACT FROM AUTHOR]

In this research, piezoelectric polymer nanocomposite films were produced through solution mixing of laser-synthesized Au nanoparticles in poly (vinylidene fluoride) (PVDF) matrix. Synthetization of Au nanoparticles was carried out by laser ablation in N-methyle-2-pyrrolidene (NMP), and then it was added to PVDF: NMP solution with three different concentrations. Fourier transformed infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were carried out in order to study the crystalline structure of the nanocomposite films. Results revealed that a remakable change in crystalline polymorph of PVDF has occurred by embedding Au nanoparticles into the polymer matrix. The polar phase fraction was greatly improved by increasing the loading content of Au nanoparticle. Thermogravimetric analysis (TGA) showed that the nanocomposite films are more resistant to high temperature and thermal degradation. An increment in dielectric constant was noticed by increasing the concentration of Au nanoparticles through capacitance, inductance, and resistance (LCR) measurement. Moreover, the mechanical properties of nanocomposites were numerically anticipated by a finite element based micromechanical model. The results reveal an enhancement in both tensile and shear moduli.

This study aims to investigate the effect of the volumefraction of zalacca fibres on the tensile strength and modulus of the LDPE-ZF composites both experimentally and analytically. The tensile tests were carried out on the randomly oriented LDPE-ZF composites manufactured by hot-pressing method. Hirsch and Bowyer–Bader’s model was used to predict the tensile strength of the composites where the elastic modulus was determined by using Tsai–Pagano, Manera and Cox–Krenchel’s model. The experimental results of tensile strength and elastic modulus of the composites was close by the Bowyer–Bader and Tsai–Pagano’s model, respectively. It is due to the consideration of fibre length and orientation factor in the Bowyer–Bader’s model and fibre elastic anisotropy in the Tsai–Pagano’s model. This study establishes that the hot press method is applicable for processing LDPE-ZF composites

The eight-chain model, also known as Arruda-Boyce model, is widely used to capture the rate-independent hyperelastic response of rubber-like materials. The parameters of this model are physically based and explained from micromechanics of chain molecules. Despite its excellent performance with only two material parameters to capture bench measurements in uniaxial and pure shear regime, the model is known to be significantly deficient in predicting the equibiaxial data. To ameliorate such drawback, over the years, several modified versions of this successful model have been proposed in the literature. The so-called full-network model is another micromechanically motivated chain model, which has also few modified versions in the literature. For this study, two modified versions of the full-network model have been selected. In this contribution, five modified versions of the Arruda-Boyce model and two modified versions of full-network model are critically compared with the classical eight-chain model for their adequacy in representing equibiaxial data. To do a comparison of all selected models in reproducing the well-known Treloar data, the analytical expressions for the three homogeneous deformation modes, that is, uniaxial tension, equibiaxial tension, and pure shear have been derived and the performances of the selected models are analysed. The comparative study demonstrates that modified Flory-Erman model, Gornet-Desmorat (GD) model, Meissner-Matějka model, and bootstrapped eight-chain model predict well the three deformation modes compare to the classical eight-chain model.

Highlights • A micromechanics based model is proposed for the CTE of HFRC. • Model is validated level by level from the cement paste level to HFRC level. • The micromechanical model can provide reasonable predictions on the CTE of HFRC. • Water/cement ratio, hydration degree, aggregate type and fiber type are taken into consideration. Abstract This study is involved with presenting a multi-level micromechanical model for predicting the coefficients of thermal expansion (CTE) of randomly distributed and oriented short hybrid fiber reinforced concrete (HFRC), which includes the cement paste level, concrete level, and HFRC level. In this micromechanical model, the inner products (IP), outer products (OP), calcium hydroxide (CH), unhydrated clinker, sands, aggregates and hybrid fibers are comprehensively considered. A substepping homogenization framework is presented to realize the upscaling from the microstructure to macro HFRC, based on which the overall CTE of HFRC is determined. In addition, the volume fractions of phases at each level are also presented to facilitate the prediction of CTE. Comparisons with experimental data from previous studies are implemented level by level. Subsequently, the influences of the water-cement ratio, the hydration degree, the aggregate property and the fiber property on the CTE are discussed carefully. [ABSTRACT FROM AUTHOR]

Abstract This article investigates the history of long-term radial and circumferential creep strains and radial displacement for a three-phase nano-composite exposed to an internal pressure and placed uniform temperature and magnetic field. Three-phase nano-composite made of single-walled carbon. The results in this paper were achieved by presuming a non-linear viscoelasticity, based on Shapery's integral model, classical laminate theory, Prandtl-Reuss's relation and Mendelson's approximation method. The distribution of the radial creep strain, circumferential creep strain and radial displacement in two states of with and without magnetic field and three temperature conditions for two lay-ups [0/45/0/45] and [0/90/0/90] described for 10 years. It has been found that the values of creep strain and radial displacement in magnetic field are lower than without a magnetic field, for two lay-ups. [ABSTRACT FROM AUTHOR]

Eutectic composite ceramics has a wide range of applications in the aerospace industry due to its excellent mechanical properties. The rupture stress of the materials is a subject of considerable importance. Eutectic composite ceramics primarily consist of rod-shaped crystals, with a small amount of particles and preexisting defects dispersed throughout. Aligned nano-micron fibers are embedded within the rod-shaped crystals. Rupture stress of a eutectic composite ceramic depends on its fracture surface energy and preexisting defects. In this study, the equivalent fracture surface energy of a eutectic ceramic composite was calculated based on its additional fracture work. Next, the effects of the preexisting defects were considered. Then, a micromechanical model of the eutectic composite ceramic was established based on its microstructural characteristics. The defects were assumed to be lamellar, and the surrounding matrix was assumed to be transversely isotropic. Using this information, the rupture stress of the eutectic ceramic composite was predicted. A comparison of the theoretical and experimental results indicated that the predicted rupture stresses corresponded with the tested data. [ABSTRACT FROM AUTHOR]

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The response of NiTi shape memory alloy (SMA) changes drastically with the loading rate. This paper presents a three-dimensional thermomechanically coupled constitutive model to describe the rate dependent cyclic performance of superelastic NiTi SMA. Two inelastic mechanisms, i.e. martensitic transformation and transformation-induced plasticity, are taken into account. The fully coupled heat equilibrium equation is deduced from the first law of thermodynamics. The thermodynamic driving forces of the internal variables are derived from the second law of thermodynamics (Clausius-Duhem inequality). The constitutive model is extended from single crystal scale to polycrystalline version via finite element approach. The validity of the model is verified through simulating thermomechanical response of cyclically tensioned superelastic NiTi SMA at various deformation rates. Moreover, the robustness of the model is checked by simulating the thermomechanical behavior of superelastic NiTi cantilever tube subjected to cyclic bending. The simulation results match with the experimental observation reasonably. [ABSTRACT FROM AUTHOR]

As confining pressure increases, crystalline rocks of moderate porosity usually undergo a transition in failure mode from localized brittle fracture to diffused damage and ductile failure. This transition has been widely reported experimentally for several decades; however, satisfactory modeling is still lacking. The present paper aims at modeling the brittle-ductile transition process of rocks under conventional triaxial compression. Based on quantitative analyses of experimental results, it is found that there is a quite satisfactory linearity between the axial inelastic strain at failure and the confining pressure prescribed. A micromechanics-based frictional damage model is then formulated using an associated plastic flow rule and a strain energy release rate-based damage criterion. The analytical solution to the strong plasticity-damage coupling problem is provided and applied to simulate the nonlinear mechanical behaviors of Tennessee marble, Indiana limestone and Jinping marble, each presenting a brittle-ductile transition in stress-strain curves. [ABSTRACT FROM AUTHOR]

In this paper a micromechanical model considering PyC interphase thermal conductance and manufacture-induced voids is proposed to predict the thermal conductivities of plain woven C/SiC composite. This model is based upon the analysis of the representative volume element (RVE) models of composite. The modeling strategy starts with a geometrical description and finite element discretization on two scales consisting of the fiber yarn modeling (fiber-scale) followed by a woven fabric modeling (yarn-scale). The PyC interphase is introduced in the fiber-scale modeling while the large voids at the intersection of orthogonal yarns are included in the yarn-scale modeling. Experiments are conducted to measure the thermal conductivities of plain woven C/SiC samples from room temperature to 800 °C temperature. The satisfied agreement with experimental data has highlighted the predictive capability of the proposed micromechanical model. Finally, a parametric study is performed using the presented model to investigate the effects of PyC interphase thermal conductance and manufacture-induced voids on the thermal conductivities of composite. [ABSTRACT FROM AUTHOR]

Particulate composites are found in a wide range of applications. Their heterogeneous microstructure affects their bulk behavior and structural performance, however tools for predicting this important structure-property relationship are still lacking. In this study, a numerical method that can provide predictions of the mechanical response of a particulate polymeric matrix composite as a function of volume fraction and particle mean diameter is presented. The work is derived for an alumina trihydrate filled poly(methyl methacrylate) but the methodology is generic and can be used for any particulate composite. Representative Volume elements are determined through images obtained from scanning electron microscopy. The model takes into account the possibility of failure through interface debonding as well as cracks through the matrix. The model predictions for the modulus and fracture strength of the composites are validated through independent experiments on the composite. The numerical results are also used to qualitatively explain the trends measured regarding the fracture toughness of the composites. Compared to other literature on particulate composites, our study is the first to report accurate stress-strain distributions as well as fracture predictions whilst all the necessary model parameters defining the failure criteria are all derived through independent experiments. This paves the way for a relatively simple methodology for determining structure-property relationships in composites design, enabling smarter material utilization and optimal mechanical properties. [ABSTRACT FROM AUTHOR]

This study focuses on the poroelastic behaviour and permeability of tight sandstones, which are characterized by a low porosity, a low gas permeability and a strong sensitivity to in-situ stress. Experimentally the Biot coefficient takes a value close to 1 at low confinement and decreases with increasing confining pressure; the permeability shows an important reduction with increasing confining pressure. This behaviour can be attributed to pore entrapment and to the closure of cracks and joints. Micromechanical models, considering low permeable sandstones as made up of an assemblage of grains with interfaces and pores, reproduce well the observed trends of Biot coefficient and permeability. [ABSTRACT FROM AUTHOR]

Microcracks can affect the mechanical properties of rocks, such as their stiffness and strength. To provide a link between the microstructural parameters and the mechanical behaviour of rock, micromechanical models use parameters that represent a quantitative description of the microcrack population. However, these parameters are difficult to constrain. With the aim of better constraining micromechanical models for rock strength and stiffness, we provide here robust measurements of microcrack characteristics. We developed an algorithm to process optical micrographs of rock, automatically creating binary images of the microcrack network. We applied this procedure to optical micrographs of fine-grained granite samples that have undergone varying degrees of thermal microcrack damage. From these processed images, we calculate the mean microcrack length and the number of microcracks per unit area (and therefore the 2D microcrack density). We also create heat maps showing the spatial distribution of microcracks and their lengths. The results of our automated image analysis are in very good agreement with those of widely-used stereological techniques, and we show that our method can be applied to other rock types (sandstone and andesite) that contain microcracks. Using the measured microcrack characteristics as inputs for Ashby and Sammis’ (1990) 2D micromechanical sliding wing crack model, we predict the uniaxial compressive strength of the granite and compare the predictions with strength measurements made in the laboratory. We find good agreement between the model and the experimental data for granite heated to temperatures below the alpha-beta transition of quartz (~573 °C). Rock strength is overestimated above this threshold, possibly due to variations in fracture toughness, which is considered constant in our modelling. Finally, we use the 2D sliding crack model of David et al. (2012) to infer microcrack density and aspect ratio from the mechanical response of the thermally microcracked samples to cyclic stressing. We show a good agreement between inferred and measured crack densities if a scaling factor is introduced. [ABSTRACT FROM AUTHOR]

The topic of this work is assessment of ductile fracture initiation and development in different zones of welded joint of a high strength low alloyed (HSLA) steel. A combined experimental-numerical procedure is applied for determination of properties of the weld metal and the heat affected zone - HAZ. One tensile specimen with rectangular cross-section is tested, and the surface strains are determined using stereometric 3D measurement (measurement system Gom Aramis with two cameras and software solution). This methodology enabled formation of the stress-strain curves for micromechanical analysis of fracture of specimens with initial fatigue pre-cracks. Two different geometries are considered: standard single-edge notched bend (SENB) specimens and surface-cracked tensile specimens. The cracks were positioned either in weld metal or in HAZ - within the fine-grained part. Micromechanical model (complete Gurson model, by Z.L. Zhang) is applied for assessment of crack growth onset and stable growth. Higher resistance to ductile fracture initiation and crack growth in HAZ is successfully predicted, as well as constraint effect caused by different crack shapes. [ABSTRACT FROM AUTHOR]

Nano-reinforced composites have a wide range of useful applications thanks to their exceptional all-encompassing characteristics. Understanding the micromechanical model and the reinforcing process in nano-composites is crucial for a quantitative assessment of the reinforcement impact of nano-fillers and performance optimization. The original micromechanical model for common composite materials is no longer applicable since mechanical modeling of composite materials takes into consideration variables like multi-scale, multi-phase, and multi-morphology. The multi-scale parameter equivalent modeling theory of nano-reinforced composites is examined in this work. It is suggested to use a generalized modified Halpin-Tsai micromechanical model, which may accommodate any reinforcement form, size, or orientation, after theoretical and experimental comparison and verification. A tiny sample of the nano-reinforced composite material's mechanical tensile characteristics was examined, and its microscopic. • By examining the multi-scale parameter equivalent model and technique of nano reinforced composite materials, a generalized modified Halpin Tsai model that can be used for any form, size, and orientation was developed. • Using the mixed solution approach, nano reinforced composite material samples were created, their mechanical tensile properties were examined, their microscopic features were observed, and the distribution and reinforcing process of nano reinforced materials were researched. • Experimental evidence shows that GPL in epoxy resin/GPL nanocomposites made using the mixed solution approach is randomly oriented in the same section, making the micromechanical concept of random orientation distribution more applicable. [ABSTRACT FROM AUTHOR]

• A new strategy is proposed to generate regional random fiber-reinforced polymer composites. • Theoretically, this method can produce FRP composites with a volume fraction of up to 90.7%. • The numerical model accurately predicts the mechanical properties of the composite. • The method alleviates the trend of decreasing tensile strength as volume fraction increases. This paper proposes a novel method of random fiber distribution inspired by the finite element mesh technique. It solves the problem of fiber interference when generating the Representative Volume Element (RVE) with a high volume fraction and prevents fiber cluster formation at low volume fractions. Theoretically, the method can produce Fiber-Reinforced Polymer (FRP) composites with volume fractions up to 90.7%. The mechanical properties of FRP composites are then predicted using a progressive damage model that considers the failure of the matrix and interface. The experimental results in the literature verify the rationality of the numerical model. Finally, the effect of varying volume fractions and cell-cutting methods on the mechanical characteristics of unidirectional FRP composites under transverse loading was studied. The results show that the elastic modulus increases with increasing fiber volume fraction, while the tensile strength shows an opposite trend. The hexagonal cell-cutting method can alleviate the adverse effect of the decrease in tensile strength with the increase in fiber volume fraction. Meanwhile, the hexagonal cell-cutting method is reliably reproducible, and the coefficient of variation for the 30 renditions is only 0.05%. It illustrates that the hexagonal cell-cutting method can generate composites with higher tensile strength compared to other methods. [Display omitted] [ABSTRACT FROM AUTHOR]

Hyperelastic rubber-like materials are described by their nonlinear elastic behavior subjected to large deformations. The one-dimensional strain energy function for polymeric material was introduced in Mahnken and Mirzapour (2022). This follow-up contribution presents a three-dimensional statistical micro-mechanical-based constitutive model incorporating the topological constraint's effects. The micro strain energy corresponding to the stored energy in a single polymer chain is mainly entropic and calculated from the entropic part of the Helmholtz free energy based on the Boltzmann equation. Then, the macro strain energy corresponding to the polymer networks is obtained by homogenizing the micro strain energy over the unit volume. At the same time, it can be decomposed into cross-linked and entangled strain energies. The current model is developed on the different angles of the polymer chain. The random nature of the polymer chain's angles is defined by proper probability distribution functions (PDFs) representing different angles' distribution. I incorporate the entangled chains based on the statistical degree of freedom introduced as polymer angles. Numerical examples to calibrate and verify the proposed model illustrate the capability of the current proposed model to reproduce the highly nonlinear behavior of rubber-like materials under different loading conditions. • An extension of one-dimensional strain energy to three-dimensional. • Incorporating the effects of the entangled chains. • Physically-based evolution of different angles of the polymer chain. • Considering the tension and compression phases of the polymer chain. [ABSTRACT FROM AUTHOR]

• Hollow spherical and flake-shaped microparticles can improve vibration reduction. • Three-phase model can be used for estimating the loss factor of microparticles. • FE strain energy method can predict the loss factor of cementitious composites. Recently, some microparticles have been proven to be effective in improving the damping performance of cementitious composites, which is described by the damping loss factor. Related studies have analyzed damping loss factors of cementitious composites with microparticles to determine optimum mixing proportion, but no efficient numerical analysis method is available for cementitious composites with microparticles. In this study, the micromechanical three-phase model and finite element (FE) strain energy were applied to cementitious composites reinforced with hollow sphere and flake-shaped microparticles. These methods have been widely used with fiber composites but never used with microparticle-reinforced composites. The three-phase model was used here to estimate the damping loss of microparticles, and FE strain energy method was used to analyze the damping loss factor of microparticle-reinforced cementitious composites with the damping loss factor from the three-phase model. This research highlights that the FE strain energy method can be an effective method for estimating the damping loss factor of cementitious composites with different types of microparticles at various volume fractions of fillers with less than 0.1% the least square error between the experimental and simulation results. [ABSTRACT FROM AUTHOR]