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The use of organically modified clays as nano-reinforcement in polymer matrices is widely investigated owing to their remarkable reinforcement at low filler loading. In this body of work, the nanocomposites were prepared by melt blending nanoclay with polyamide 11 (PA 11) utilising a twin-screw extruder in order to maximise the dispersion of clay particles within the matrix during compounding. The main aim of the work was to study the reinforcing effect of nanoclay within PA 11 using two micromechanical model namely Halpin-Tsai and Mori-Tanaka composite theories. These theories were used to predict the effective tensile modulus of PA 11 nanocomposites and the results were compared to the experimental data. In addition, the Halpin-Tsai model was used to predict the storage modulus and heat distortion temperature (HDT) of PA 11 nanocomposites. It was found that the tensile modulus for nanocomposites with a high clay aspect ratio exhibits up to 10% higher when compared to the nanocomposites with lower clay aspect ratio. Thus, it is believed that the combination of clay aspect ratio and modulus contributes to the super reinforcing effect of nanoclay within the PA 11 matrix.

On the example of metal-diamond composites (MDC), a number of issues of thermomechanics of disperse-filled materials with high thermal conductivity used for thermal management are formulated and solved. Due to the importance of the thermal conductivity factor of the interfacial layer, a refined method is proposed for calculating the boundary thermal resistance. This method considers two counter heat flows: from the matrix to the filler and back, and also provides the condition of zero thermal resistance at the same values of the thermomechanical characteristics of these components. Based on the micromechanical model of the disperse-filled composite, an analytical method is developed for determining the effective thermal conductivity coefficient of the metal-diamond composites. The method makes it possible to take into account the boundary thermal resistance, the presence of a thin coating on the diamond particle, the anisometry of diamond particles and the porosity of the metal matrix. The results of the performed parametric analysis are compared with known experimental data and estimates obtained within the framework of existing models. The conclusion on the validity of the developed method is made. A simplified finite-element model is developed for a representative volume of the metal-diamond composites in the form of a cube formed by an aluminum matrix and containing 27 spherical diamond particles of the same radius with a modifying tungsten coating. At a given temperature difference on the opposite faces of the cube, the distribution of heat flux density and the effective heat transfer coefficient of the metal-diamond composites are calculated. Comparison of the results of using the finite element model and the analytical method mentioned above shows their good agreement. Modification of the finite element model is carried out in order to better match the real internal structure of the metal-diamond composites studied by high-resolution X-ray microtomography. Numerical analysis of the temperature field, thermal stress state and fracture kinetics of the aluminum-diamond composite during thermal cycling is performed.

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.

Large-scale 3D printed concrete structures with lattice infill will result in lightweight components with high mass-specific strength, and faster fabrication, compared to conventional casting methods. However, the effect of different infill patterns on mechanical performance is still not addressed clearly in many scientific publications. This study investigates the bending performance of 3D-printed concrete beams with four infill patterns such as lattice, triangular, lattice-triangular, and sinusoidal tested in vertical (layer deposition direction) and transverse (layer translation direction) loading directions. The load versus displacement curves and crack propagation patterns are investigated both via Finite Element (FE) simulations and experiments. The FE results corroborated by experiments indicated that the triangular patterns perform better than lattice-shaped infill counterparts particularly under the transverse loading direction exhibiting the highest flexural deformation resistance capacity. The findings of this study would be useful in latticing large-scale concrete structures for diverse applications.

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.

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.

Polyvinylidene fluoride or polyvinylidene difluoride (PVDF) is a piezoelectric semi-crystalline polymer whose electro-mechanical properties may be modulated via strain-induced α → β phase transition and the incorporation of polarized inorganic particles. The present work focuses on the constitutive representation of PVDF-based piezo-composites developed within the continuum-based micromechanical framework and considering the combined effects of particle reinforcement, α → β phase transition, and debonding along the interface between the PVDF matrix and the particles under increasing deformation. The micromechanics-based model is applied to available experimental data of PVDF filled with various concentrations of barium titanate (BaTiO3) particles. After its identification and predictability verification, the model is used to provide a better understanding of the separate and synergistic effects of BaTiO3 particle reinforcement and the micromechanical deformation processes on the electro-mechanical properties of PVDF-based piezo-composites.

Nanomaterials have shown more interests to the field of nanotechnologies. Polymeric nanocomposites combine the lightweight and low cost of manufacturing for polymers with nanoparticles of higher performance properties. The aim of this paper is to find the mechanical properties of nanocomposite of polymer reinforced by nanoparticles with considering matrix viscoelasticity. The viscoelasticity of the polymer was obtained from the experimental tests for the thermoplastic polymer of Poly ether ether Ketone (PEEK) at a range of temperatures and frequencies. The viscoelasticity of the polymer was confirmed by comparing the experimental results with a finite element model. The approved viscoelasticity was used for the matrix of the nanocomposite numerically. To obtain the mechanical properties of the nanocomposite, a micromechanical model was developed. It was used to find their homogeneous mechanical properties with range temperatures. It was found that the viscoelasticity have effect on mechanical properties for the nanocomposite, and the modulus of the nanocomposite increases with nanoparticle content. However, it decreases as the temperature increases. Parameswaranpillai J., Kurian N. and Yu Y.2015, Nanocomposite materials: synthesis, properties and applications, CRC press, Taylor and Francis group. Yas M, Korani H. and Jouneghani F. 2020. Studying the mechanical and thermal properties of polymer REFERENCE nanocomposites reinforced with montmorillonite nanoparticles using micromechanics method, Journal of solid mechanics, 12(1), 90-101, 2020. Le B. 2020. A review on Nanocomposites Part 1: Mechanical Properties, Journal of Manufacturing Science and Engineering, DOI:10.1115/1.4047047. Ou Y., Yang F., Yu Z. 1998. A new conception on the toughness of nylon 6/silica nanocomposite prepared via in situ polymerization, Journal of Polymer Scenc. B: Polymer Phyics, 36, 789–795. 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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.

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.

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.

Rubber-like materials can deform largely and nonlinearly upon loading, and they return to the initial configuration when the load is removed. Such rubber elasticity is achieved due to very flexible long-chain molecules and a three-dimensional network structure that is formed via cross-linking or entanglements between molecules. Over the years, to model the mechanical behavior of such randomly oriented microstructures, several phenomenological and micromechanically motivated network models for nearly incompressible hyperelastic polymeric materials have been proposed in the literature. To implement these models for polymeric material (undoubtedly with widespread engineering applications) in the finite element framework for solving a boundary value problem, one would require two important ingredients, i.e., the stress tensor and the consistent fourth-order tangent operator, where the latter is the result of linearization of the former. In our previous work, 14 such material models are reviewed by deriving the accurate stress tensors and tangent operators from a group of phenomenological and micromechanical models at large deformations. The current contribution will supplement some further important models that were not included in the previous work. For comparison of all selected models in reproducing the well-known Treloar data, the analytical expressions for the three homogeneous defomation modes, i.e., uniaxial tension, equibiaxial tension, and pure shear, have been derived and the performances of the models are analyzed.

A new model is proposed in this research to calculate the longitudinal strengthof unidirectional E-glass reinforced polymer composites exposed to sulfuricacid environment, using a micromechanics model. In the proposed method,it is assumed that the residual strength of the degraded composites under acidic environment can be calculated by knowing the degraded strength properties of the constituent materials. In order to measure the properties of the degraded epoxy resins and E-glass fibers, corrosion tests are performed on them when exposed to 5% sulfuric acid for different immersion times. Acid penetration in composites is a time consuming phenomenon. Thus, before the acid reaches to inside region of composites, the degraded composites cross-section can be divided to two regions, namely intact and degraded regions. In this stage, a simple model is suggested to estimate the acid penetration depth in the degraded composites. Based on the corrosion mechanisms of glass fibers, the energy dispersive x-ray microanalysis (EDX) results of different points of composites cross-section are used to estimate the acid penetration depth in composites. Both the acid penetration depth model and micromechanics model are used to calculate the longitudinal strength of intact and degraded regions for different immersion times. Thus, the longitudinal strength of degraded composites can be calculated. Moreover, some similar unidirectional E-glass/ epoxy composites exposed to sulfuric acid for different immersion times are tested to measure the longitudinal strength of them. The theoretical results are in good agreements with those experimentally measured.

Electro-thermo-elastic stress analysis of piezoelectric polymeric thick-walled cylinder reinforced by boronnitride nanotubes (BNNTs) subjected to electro-thermo-mechanical fields is presented in this article. The electro-thermo-elastic properties of piezoelectric fiber reinforced composite (PEFRC) was studied by a modified XY micromechanical model capable of exhibiting full coupling relation between electric, thermal and elastic fields. Assuming the basic relation for the axisymmetric deformation of a thick-wall cylinder subjected to uniform internal and external pressures, an axial electrical load, a temperature change T ∆ between inner and outer radius are derived. The stress results suggest that increasing BNNTs content in longitudinal direction reduces the effective stress. Also, displacement along radial direction indicates an optimum content of 5% BNNT for this. Furthermore, at normal working conditions, the influence of thermal and mechanical fields are much higher than the electric one on the effective stress; hence, this smart structure is best suited for applications as sensors than actuators.

In this research, the effect of the drawing process on the physical and thermal properties of commercially available polypropylene fiber containing selective peroxide was studied. Attempts have also been made to compare this drawn fiber sample with conventional polypropylene fibers produced from reactor and with controlled rheology grades. The results showed that the drawn PP/Peroxide fiber has higher birefringence, tenacity, and initial modulus compared with that of the drawn polypropylene fiber. Moreover, the fraction of load carrying chains in various drawn polypropylene fibers was evaluated on the basis of simplified models.

To describe the rheological behavior of polymer blends using emulsionbased (Palierne theory) as well as micromechanical models (Coranapproach), two immiscible polymeric blend systems of poly(trimethylene terephthalate) (PTT)/polyamide-12 (PA12) and PTT/polyethylene (PE) having different levels of molecular interactions were investigated as model systems. The role of interfacial interactions, viscosity ratio, composition, and shear rate were also explored with respect to the aforementioned theories. For both systems no reasonable agreement was noticed between the experimental data and Palierne model predictions, which was related to high viscosity ratio and high dispersed phase content. Nevertheless, the PTT/PE blend, having almost a zero interfacial thickness due to the absence of intermolecular interaction, exhibited a seemingly better correlation with experimental data compared to PTT/PA12 system. Moreover a better agreement between experimental and theoretical data was obtained in the blend where the viscosity of dispersed phase was higher than that of matrix. Also, in both model systems, the values predicted from Palierne were closer to empirical data at higher frequencies most likely due to breakdown in physical network structure. Coran analysis due to its micromechanical origin could give outputs in good agreement with the experimental results in both model systems.

Shape memory polymers (SMPs) have thermomechanical property drastically altering around the glass-transition temperature (Tg), temporary shape fixity and shape recovery property, and so on. To understand the mechanisms of such unique properties and design products including SMPs optimally, a mathematical model which is simple yet can represent these properties reasonably and accurately is necessary. Especially, it is important for the model to be able to consider the effect of temperature and strain history on the properties because the properties are considered to depend on not only the temperature and the strain themselves but also their history. Therefore, in this paper first the effect of the temperature and strain history on the shape fixity and shape recovery properties was examined. Then, a micromechanical model of SMP was developed to describe this effect. This model consisted of a lot of unit elements having four springs, two dash pots, one latch, and one thermal expansion element. Different Tg was assigned to each element because Tg depends on local condition inside of SMP and distributed in general. It was found from the experiment that the temperature and strain history applied to SMP when the shape is gradually frozen has an influence on the shape recovery process. With respect to the model, it was shown that the proposed micromechanical model can capture the thermomechanical behaviors of SMP and, especially, the temperature and strain histories dependence on the shape recovery process quite well.

In this research, the effect of the drawing process on the physical and thermal properties of commercially available polypropylene fiber containing selective peroxide was studied. Attempts have also been made to compare this drawn fiber sample with conventional polypropylene fibers produced from reactor and with controlled rheology grades. The results showed that the drawn PP/Peroxide fiber has higher birefringence, tenacity, and initial modulus compared with that of the drawn polypropylene fiber. Moreover, the fraction of load carrying chains in various drawn polypropylene fibers was evaluated on the basis of simplified models.

In this research, the effect of the drawing process on the physical and thermal properties of commercially available polypropylene fiber containing selective peroxide was studied. Attempts have also been made to compare this drawn fiber sample with conventional polypropylene fibers produced from reactor and with controlled rheology grades. The results showed that the drawn PP/Peroxide fiber has higher birefringence, tenacity, and initial modulus compared with that of the drawn polypropylene fiber. Moreover, the fraction of load carrying chains in various drawn polypropylene fibers was evaluated on the basis of simplified models.