Effect Of Interphase Research Articles

Effect of heterogeneous interphase on the mechanical properties of unidirectional fiber composites studied by FFT-based method

Based on representative volume element (RVE) with interphase region between fiber and matrix, the microscopic mechanical behavior of transversely randomly distributed unidirectional (UD) carbon fiber reinforced polymer composites is studied by using fast Fourier transforms (FFT) simulation. The change of mechanical properties across interphase region can be described by an exponential function. By using FFT method, the effect of fiber volume fraction and interphase properties distribution on the effective material properties and the damage development mechanism of the composites are investigated. The effect of heterogeneous behaviors of carbon fiber with core/shell like behavior and interphase is also discussed. Compared to the traditional finite element model with zero-thickness interface, the stress-strain results obtained by the present computational approach are in good agreement with experimental data. This study can be helpful for interface design and manufacturing of fiber reinforced composites.

Investigation on the effects of microstructure on machining unidirectional carbon fiber reinforced polymer composites with a modified force model

The paper aims to investigate the correlation of microstructural characteristics and machinability of unidirectional carbon fiber reinforced polymer composites by a modified analytical model. A representative volume element was selected to present the microstructure and analyze the force distribution, in which the interphase between the fiber and the matrix was considered significantly. And the microstructure can be obviously measured by using microscopic observation, especially the interphase was found to be around 0.3 μm in the used carbon fiber reinforced polymer composites. To study the representative volume element effect on the cutting behavior of unidirectional carbon fiber reinforced polymer composites, the prediction of cutting force was done by using a modified force model. Compared with the experiments, the developed model can well predict the cutting forces and subsurface damage in the carbon fiber reinforced polymer composites cutting. It was found that surface integrity as well as subsurface damage has a coincident varying trend with the fiber orientations, as confirmed by the observations of the machined surface at different fiber orientations. The good surface integrity can be obtained at the low fiber orientation of 0° and the poor surface occurs at the large fiber orientation of 135°. Moreover, the effect of interphase and the fiber volume fraction in representative volume element were further investigated. The results show that the cutting forces increase with increasing the fiber volume fraction as well as the interphase volume fraction, and the interphase affects the cutting force in the transverse direction is significantly higher than that in longitudinal direction.

Modeling Long Open-Air Electric Arcs

Abstract This article presents a model of Sparking Gap to be used in the Alternative Transients Program (ATP). The model includes the simulation of breakdown and a representation of the electric arc. The arc will be non-constrained and burn in air at atmospheric pressure, thus a discussion of the model and parameters to be used is presented. The effect of the arc on the interruption of current will be studied. Examples of power arc interruption following an impulse impact on a 230 kV transmission line are presented. The effects of interphase capacitive coupling and line length are discussed, in order to establish guidelines to allow successful reclosing operations.

Postbuckling behavior of functionally graded CNT-reinforced nanocomposite plate with interphase effect

Abstract The present paper is aimed to study the buckling and postbuckling response of functionally graded carbon nanotube (FG-CNT)- magnesium (Mg) nanocomposite plate with interphase effect. Interphase zone is characterized by employing a cohesive zone model for its elastic modulus and thickness. An equivalent solid fiber (ESF) of CNT and interphase is modeled and dispersed into the matrix material by utilizing random sequential adsorption (RSA) technique. The effective elastic properties of the nanocomposite are computed by finite element method (FEM) based numerical homogenization technique. The obtained elastic properties of nanocomposite are utilized to investigate the buckling and post-buckling behaviour of different functionally graded (i.e., FG) nanocomposite plates modeled by varying the volume fraction of CNT/ESF along thickness direction, under in-plane compressive loads. The non-linear formulation is based on first-order shear deformation theory and von Karman’s assumptions. It is found that considering the interphase between CNT and Mg matrix would result in decrease in buckling load and postbuckling strength of FG-CNT-reinforced nanocomposite plate as compared to nanocomposite without interphase. It is also reported that the higher volume fraction of CNTs near top and bottom surfaces than the middle portion of nanocomposite plate provide better resistance to buckling and postbuckling.

The fraction of overlapping interphase around 2D and 3D polydisperse non-spherical particles: Theoretical and numerical models

The fraction of interphase is an important microstructure parameter in the prediction of macroscopic properties of particulate composites. Currently, some researchers have presented theoretical and numerical investigations on the interphase fraction for spherical particle systems, and even quantify the influence of interphase fraction on the overall elastic and transport properties of particulate composites. However, the overlapping interphase fraction in polydisperse non-spherical particle systems is still an open issue. In this work, a generic theoretical model is formulated to derive the overlapping interphase fraction for polydisperse 2D non-circular and 3D non-spherical particle systems by means of the statistical geometry of composites. In this model, the morphology of interphase coated onto the surface of non-spherical particles can be characterized by circularity and sphericity of particles that are important parameters to describe the shape of particles. On the other hand, numerical simulations for the one-point probability function of interphase are presented to verify the proposed theoretical framework. In the numerical simulations, a novel algorithm is developed by reducing the problem of identifying the precise location between an arbitrary spatial point and interphase to the basic issue of finding the distance from the point to the surface of particles. If the distance is less than the interphase thickness, the point definitely locates inside interphase. In addition, the algorithm can be further used to detect the overlap between adjacent ellipsoidal particles (2D ellipses). Moreover, a variety of particle shapes (such as regular polygons and ellipses with the same circularity, and regular polyhedrons and ellipsoids with the same sphericity) are taken into account to generate particle packing structures. Then, the fraction of overlapping interphase in each packing structure is statistically obtained. Results show that statistical values are consistent with their theoretical values under the same conditions. This validates the reliability of the theoretical framework. Finally, the effects of particle size distributions and interphase thicknesses on the interphase fraction are investigated. It can be found that the interphase fraction increases with the increase of particle volume fraction, particle fineness and interphase thickness.

Micromechanical analysis of elastic modulus of carbon nanotube-aluminum nanocomposites with random microstructures

The formation of Al4C3 interphase in carbon nanotube (CNT)-reinforced aluminum (Al) nanocomposites is a critical issue which must be well-known to more realistic estimations of mechanical behavior of such materials. In this work, the effect of Al4C3 interphase on the elastic modulus of Al nanocomposites reinforced with randomly distributed CNTs is investigated using a numerical micromechanical model based on the finite element method (FEM). Moreover, the influences of the CNT volume fraction and diameter on the elastic modulus of Al nanocomposites are explored. The results reveal that Al4C3 interphase significantly affects the elastic modulus of Al nanocomposites especially as the CNT diameter decreases. It can be observed that with increasing interphase thickness, the elastic modulus of the nanocomposite increases. The applicability of the presented model in predicting the elastic modulus of CNT-reinforced Al nanocomposites is investigated by comparing the results of the FEM with those of experiment available in the literature. Furthermore, the results of the FEM with and without Al4C3 interphase for aligned continuous and discontinuous CNT-reinforced Al nanocomposites are presented. It is found that the effect of the interphase on the elastic modulus of nanocomposites reinforced with continuous CNT is more important than that of nanocomposites reinforced with discontinuous CNT.

Effect of interphase on mechanical properties and microstructures of 3D Cf/SiBCN composites at elevated temperatures

AbstractInterphase between the fibers and matrix plays a key role on the properties of fiber reinforced composites. In this work, the effect of interphase on mechanical properties and microstructures of 3D Cf/SiBCN composites at elevated temperatures was investigated. When PyC interphase is used, flexural strength and elastic modulus of the Cf/SiBCN composites decrease seriously at 1600°C (92 ± 15 MPa, 12 ± 2 GPa), compared with the properties at room temperature (371 ± 31 MPa, 31 ± 2 GPa). While, the flexural strength and elastic modulus of Cf/SiBCN composites with PyC/SiC multilayered interphase at 1600°C are as high as 330 ± 7 MPa and 30 ± 2 GPa, respectively, which are 97% and 73% of the values at room temperature (341 ± 20 MPa, 41 ± 2 GPa). To clarify the effect mechanism of the interphase on mechanical properties of the Cf/SiBCN composites at elevated temperature, interfacial bonding strength (IFBS) and microstructures of the composites were investigated in detail. It reveals that the PyC/SiC multilayered interphase can retard the SiBCN matrix degradation at elevated temperature, leading to the high strength retention of the composites at 1600°C.

Molecular Motion in Viscous DGEBA with Nanoparticles as Seen by Quasi‐Elastic Neutron Scattering

AbstractPure and filled epoxies are widely used in industry. Nanocomposites especially are affected by interphase regions where properties deviate from bulk. The study of molecular mobility in epoxy monomers is a first step to understanding the molecular dynamics in nanocomposites and their effect on crosslinking in epoxy networks. Here, quasi‐elastic neutron scattering is used to disentangle the molecular motions of monomeric diglycidylether of Bisphenol A (DGEBA) and a suspension of zeolite nanoparticles in DGEBA on a timescale from 2 ps to 5.5 ns. Regarding molecular transport of DGEBA inside the suspension, the particles have no impact on the faster rotational motions. A combination of neutron time‐of‐flight and backscattering spectroscopy reveals a pronounced hindrance of DGEBA molecular dynamics on/in the zeolite particles along with a new type of molecular motion occurring on intermediate timescales. That localized motion is attributed to jump diffusion motions, emanating from interphase effects at the zeolite particles.

Studying buckling of composite rods made of hybrid carbon fiber/carbon nanotube reinforced polyimide using multiscale FEM

In this paper, the buckling behavior of rods made of carbon fiber/carbon nanotube-reinforced polyimide (CF/CNT-RP) under the action of axial load is investigated based on a multiscale finite element method. A dual-step procedure is first adopted to couple the influences of micro- and nano-scale in order to obtain the equivalent elastic properties of CF/CNT-RP for various volume fractions of CF and CNT. The interphase effect between CNTs and the polymer matrix is taken into consideration. Also, dispersion of CF/CNT into the polymer matrix is assumed to be random. Then, rods with square and circular cross sections are considered whose stability characteristics are analyzed. The finite element modeling is performed using two models including a 3D brick model and a 2D beam model. Selected numerical results are given to study the effects of volume fraction of CNT/CF, interphase and geometrical properties on the axial buckling response of multiscale composite rods.

Multiple-inclusion model for the transport properties of porous composites considering coupled effects of pores and interphase around spheroidal particles

Understanding of the effects of particle geometries, pores and interphase characteristics on transport properties of porous composites is very crucial to the smart design of porous composites and the improvement of their durability. In this work, the authors devise a multiple-inclusion micromechanical model to predict the effective transport properties of multiphase porous composites, where spheroidal inclusions of diverse types are randomly dispersed in a homogeneous matrix. The multiple-inclusion model is then applied to estimate the effective diffusivity of four-phase porous composites containing impermeable particles, pores, highly permeable interphase and matrix. Specifically, the microstructural characteristics of pores, interphase and particles, and their physical properties are incorporated into the evaluation of the effective diffusivity of porous composites. It is shown that the present model leads the prediction of diffusivity of porous composites to reasonable accuracy by comparing with extensive experimental data. Moreover, utilizing the proposed model, we investigate the dependence of effective diffusivity of porous composites on the shape, volume fraction and size distribution of impermeable particles, the interphase thickness and volume fraction, and the porosity characterized by the hydration degree of cement and the water-cement ratio. The results reveal that the geometrical and physical properties of these components play a significant role in determining the diffusivity of porous composites. The multiple-inclusion model provides a powerful and convenient predictive toolkit for multiphase composite design and evaluation.

Insight into the Formation/Decomposition of Solid Electrolyte Interphase Films and Effects on the Electrochemical Properties of Sn/Graphene Anodes

A robust solid electrolyte interphase film formed on the anode is of importance for the electrochemical performances of a lithium-ion battery. In this work, the formation and decomposition of the s...

High-rate cycling performance and surface analysis of LiNi1-Co/2Mn/2O2 (x=2/3, 0.4, 0.2) cathode materials

Abstract The electrochemical performance of layered LiNi1-xCox/2Mnx/2O2 cathode materials (x = 2/3, 0.4, 0.2; so-called NCM333, NCM622, NCM811) in 1.0 M LiPF6-dissolved conventional carbonate-based electrolyte during formation at a 0.1 C-rate and consequent cycling at a 1.0 C-rate is measured and considered together with the results of morphology observation, impedance spectroscopy, and surface analysis. X-ray photoelectron spectroscopy (XPS) is carried out on the surface of the cathode materials before and after formation and cycling to investigate the effects of solid electrolyte interphase (SEI) formation on the electrochemical performance. As the Ni content increases, the initial specific capacity increases but the capacity retention ratio decreases. High-rate cycling overrides the SEI formation on the NCM surfaces, but NCM622 suffers great changes in the SEI components with a thick layer resulting in large interfacial resistance. It is also proved that NCM811 shows significant dissolution and accumulation of Ni species on the surface, contributing structural degradation and leading to fast capacity fading.

Fully coupled thermo-magneto-electro-elastic properties of unidirectional smart composites with a piezoelectric interphase

In the present study, the effect of PZT-5A piezoelectric interphase on the effective thermo-magneto-electro-elastic properties of CoFe2O4 piezomagnetic matrix composites reinforced with carbon fibers is investigated. In this type of three-phase smart composite, the unidirectional fiber is coated with the piezoelectric shell. To this end, the fully coupled thermo-magneto-electro-elastic constitutive relations are developed for a unit cell-based micromechanical model in conjunction with a proper representative volume element. The influences of piezoelectric interphase thickness on the effective properties of the unidirectional smart composite are extensively investigated at different carbon fiber volume fractions up to 70%. The results demonstrate that piezoelectric interphase can greatly affect the overall thermo-magneto-electro-elastic properties of the smart composites. For two-phase smart composites, the present predictions are found to be in close proximity with the Mori–Tanaka results, which validates the present model.

Effect of aluminum carbide interphase on the thermomechanical behavior of carbon nanotube/aluminum nanocomposites

The objective of this work is to investigate the coefficient of thermal expansion of carbon nanotube reinforced aluminum matrix nanocomposites in which aluminum carbide (Al4C3) interphase formed due to chemical interaction between the carbon nanotube and aluminum matrix is included. To this end, the micromechanical finite element method along with a representative volume element, which incorporates, carbon nanotube, interphase, and aluminum matrix is employed. The emphasis is mainly placed on the effect of Al4C3 interphase on the coefficient of thermal expansion of aluminum nanocomposites with random microstructures. The effects of interphase thickness, carbon nanotube diameter, and volume fraction on the thermomechanical response of aluminum nanocomposite are discussed. The results reveal that the effect of Al4C3 interphase on the coefficient of thermal expansion of the aluminum nanocomposites becomes more significant with (i) increasing the coefficient of thermal expansion volume fraction, (ii) decreasing the coefficient of thermal expansion diameter, and (iii) increasing the interphase thickness. It is clearly observed that the coefficient of thermal expansion varies nonlinearly with the carbon nanotube diameter; however, it decreases linearly as the carbon nanotube volume fraction increases. Furthermore, the axial and transverse coefficient of thermal expansions of aligned continuous and discontinuous carbon nanotube-reinforced aluminum nanocomposites with Al4C3 interphase are predicted. Also, the presented finite element method results are compared with the available experiment in the literature, rule of mixture, and concentric cylinder model results.

Critical Role of Interfacial Diffusion and Diffuse Interphases Formed in Multi-Micro-/Nanolayered Polymer Films Based on Poly(vinylidene fluoride) and Poly(methyl methacrylate).

It is known that the macroscopic properties of multilayer polymer films are largely dominated by the diffuse interphase formed via interfacial diffusion between neighboring layers. However, not much is known about the origin of this effect. In this work, we reveal the role of interfacial diffusion and the diffuse interphase development in multilayer polymer films, based on a compatible poly(vinylidene fluoride)/poly(methyl methacrylate) system fabricated by forced-assembly micro-/nanolayer coextrusion. Interestingly, the layer morphology is found to prevail in all investigated multilayer films, even for the nanolayered system where the interdiffusion is substantial. It is also demonstrated that, in the presence of macromolecular and geometrical confinements, interfacial diffusion significantly alters the crystalline morphology and microstructure of the resulting micro-/nanolayered films, which leads to quantitatively different dielectric and rheological properties. More importantly, the combination of dielectric relaxation spectroscopy and energy-dispersive X-ray analysis further reveals that multiple diffuse interphases with various length scales exist in the multilayer structures. The presence of these multiple interphases is explained in terms of a proposed physical picture for the interdiffusion of fast-mode mechanism occurring in the coextrusion process, and their length scales (i.e., interphase thicknesses) are further mapped quantitatively. These findings provide new insights into the effects of interfacial diffusion and diffuse interphases toward tailoring interfaces/interphases in micro-/nanolayered polymer structures and for their advanced applications.

Interphase region effect on the biaxial yielding envelope of SiC fiber-reinforced Ti matrix composites

The objective of this paper is to investigate the coupled effects of interphase and thermal residual stress on the biaxial initial yield surfaces of metal matrix composites using the simplified unit cell micromechanical model. The representative volume element of the composite consists of three phases, including unidirectional silicon carbide (SiC) fiber, titanium (Ti) matrix, and the interphase region between the fiber and matrix. It is found that the interphase slightly affects the initial yield surfaces of metal matrix composites without thermal residual stress. However, the results reveal that as the thermal residual stress is considered in the micromechanical modeling, the effect of interphase on the response of metal matrix composites becomes much more significant. The effects of the SiC volume fraction, interphase parameters including thickness and material properties on the yielding behavior of the metal matrix composites are examined. To demonstrate the validity of the model, comparisons are carried out between the results of the present model and other micromechanical methods as well as experiment. The extracted results could be useful to guide the modeling and design of a wide range of multiphase metal matrix composites.

Micromechanical characterizing the effective elastic properties of general randomly distributed CNT–reinforced polymer nanocomposites

This work deals with a comprehensive study on the general off-axis mechanical properties of polymer nanocomposites reinforced by carbon nanotubes (CNTs) using a three-dimensional micromechanical model. The representative volume element (RVE) of the model consists of three phases including CNT, polymer matrix and interphase formed due to the non-bonded interaction between a CNT and the polymer. The CNTs are assumed to be transverse isotropic. Both random under several statistical distribution and regular arrangements of the CNTs within the matrix are considered in the analysis. The results are shown to be consistent with the results of other theoretical methods and experiment. Effects of various parameters, including the CNT aspect ratio, orientation, distribution, cross sectional shape and volume fraction, the interphase characteristics and the matrix material properties are examined on the effective elastic properties of CNT–reinforced polymer nanocomposites. The results reveal that the mechanical properties of the nanocomposite are extremely dependent on the CNTs off-axis angle. The interphase effect is more significant for the elastic modulus of 70°off-axis coupon. It is found that CNT volume fraction has the maximum effect for the longitudinal elastic modulus. For 90°coupons, elastic modulus of the nanocomposite is significantly affected by the matrix properties. The results obviously indicate that the elastic modulus, especially in the longitudinal direction increases up to a threshold value and then saturates as the CNT aspect ratio increases. Also, it is found that the CNT arrangement does not affect the longitudinal elastic modulus of CNT–polymer nanocomposites, whereas the transverse elastic modulus is significantly affected by the CNT arrangement.

Solid Electrolyte Interphase and Nitrogen Doping Effect on Potassium Storage Mechanism in Graphite

The inferior cycling stability critically impedes the development of potassium-ion batteries (KIBs). The solid electrolyte interface (SEI) for nitrogen doped graphite foam (NGF) was studied in both KPF6 and KN(SO2F)2 (KFSI)-based organic electrolytes, aiming to unravel the SEI effect on K+ ion storage mechanism. Electrochemical characterizations disclose that the KN(SO2F)2-based cells deliver improved electrochemical performance in terms of reversibility and cycling stability, compared to KPF6 based cells. Experimental results including depth-profiling XPS and FTIR spectra, together with the theoretical calculations, reveal that (CH2OCO2K)2, C2H5OCO2K, KF and K2CO3 are the dominant components of SEI layers in both electrolytes. Particularly, the amount of K2CO3 in KPF6-based electrolyte is much more than that in KFSI-based electrolyte, resulting in inferior stability. Moreover, the depth-profile XPS results indicate that the SEI formed in KFSI based electrolyte is much more stable, compact and thinner than that in KPF6 based electrolyte. All these features, together, ensure good stability and high reversibility in KFSI-based electrolyte. The nitrogen doping effect on K+ ion storage was also explored. Enhanced electrochemical performance was identified upon increasing the nitrogen content, due to i) the enrichment of active sites for K+ ion storage and ii) the improved electronic conductivity. Moreover, the electrochemical performance is strongly dependent on N-doping types. Specifically, the pyridinic nitrogen dominates the reversible capacity, as identified by the presence of critical point at 4.29 at. %. In which, the atomic ratio of pyridinic N in NGF is 2.53 at. %, which is higher than that of 7.03 at. %, with only 2.16 at. % pyridinic N. The result is consistent with the theoretical study, which verifies that the charge transferred from K ions to NGF increases with the pyridinic nitrogen doping. Our results promote better understanding of K+ ion storage mechanism in graphite and provide invaluable guidance for optimized carbon-based electrode design for high-performance KIBs.

Effect of piezoelectric interphase on the effective magneto-electro-elastic properties of three-phase smart composites: A micromechanical study

ABSTRACTA unit cell-based micromechanical model is presented to investigate the effect of PZT-7A piezoelectric interphase on the effective magneto-electro-elastic properties of CoFe2O4 piezomagnetic matrix composites reinforced with piezoelectric fibers. The carbon fiber is coated with the PZT-7A piezoelectric material. The model is used to determine effective stresses, electric and magnetic field properties of the smart composite. By applying loads over the RVE of unit cell model in electric and magnetic fields, the in-plane strains, corresponding piezoelectric constants and corresponding piezomagnetic constants are obtained. The influences of interphase thickness on effective magneto-electro-elastic properties are investigated at different piezoelectric fiber volume fractions.

Micromechanical study of elastic-plastic and thermoelastic behaviors of SiC nanoparticle-reinforced aluminum nanocomposites

Elastic-plastic and thermal expansion responses of aluminum (Al) matrix nanocomposites reinforced with silicon carbide (SiC) nanoparticles are investigated through a micromechanics analytical unit cell method. The formation of the interphase region between SiC nanoparticles and Al matrix is taken into account in the modeling of nanocomposites. The influences of some important parameters such as the thickness and material properties of the interphase, volume fraction and diameter of SiC nanoparticles on the elastic modulus, coefficient of thermal expansion (CTE) and elastoplastic stress-strain curve of the Al nanocomposites are studied in detail. The results clearly reveal high contribution of the interphase region to the overall mechanical and thermal behaviors of Al nanocomposites. It is found that when nanoparticle diameter is lower than about 150 nm, the decrease of SiC nanoparticle diameter leads to (i) an increment in mechanical properties both in the elastic and plastic regions and (ii) a reduction in CTE of the metal matrix nanocomposites. Also, the effect of interphase on the elastic modulus and CTE of Al nanocomposites becomes more important with the reduction of SiC nanoparticle diameter. Finally, the micromechanical model is employed to predict the elastoplastic behavior of SiC nanoparticle-reinforced Al nanocomposites subjected to multi-axial loading conditions in the presence and absence of the interphase region.