Interphase Parameters Research Articles

Simulation of tensile strength for polymer hydroxyapatite nanocomposites by interphase and nanofiller dimensions

AbstractSeveral models have been used in literature studies to describe the mechanical behavior of hydroxyapatite (HA) polymer nanocomposites. However, previous models have often overlooked the size of HA and the properties of the interphase. In this study, we further develop an equation originally proposed by Kolarik. This advanced equation predicts the tensile strength of polymer/HA nanocomposites by considering the interphase parameter (A), rod‐like HA size, HA concentration, and interphase properties, including depth and strength. We validate our method using experimental data from various examples and through parametric inspections. Both the strength and the depth of the interphase directly affect the ‘A’ value and, consequently, the strength of the nanocomposites. For instance, an HA radius (R) of 6 nm yields the highest ‘A’ value of 4.97, enhancing the nanocomposite strength by up to 250%. In contrast, ‘R’ value of 20 nm fails to reinforce the samples effectively. Additionally, the thickness of the interphase (t) and the concentration of HA directly handle the nanocomposite strength. The strength of the samples significantly improves by 137% and 160% with an interphase thickness of 50 nm and an HA volume fraction of 0.2, respectively. Generally, the length of HA and interphase characteristics (thickness and strength) directly control the strength of samples, but the HA radius has an inverse relationship with nanocomposite strength.Highlights Kolarik equation is developed to predict the tensile strength of polymer HA nanocomposites. Interphase parameter, HA size, HA concentration and interphase properties are considered. HA radius of 6 nm produces the maximum enhancement of nanocomposite strength by 250%. Interphase properties and concentration of HA directly control the nanocomposite strength. All parameters reasonably influence the strength of samples confirming the developed model.

Interphase parameter prediction in nanocellulose composites using young modulus modeling

In this study, the Ji-developed model for modeling the young modulus of nanocomposites was suggested to predict interphase thickness (Y) and modulus (Ei). The resulting model was evaluated for accuracy by comparing it to the experimental young moduli of various samples. Additionally, the effects of using a compatibilizer or modified nanocellulose on the interphase thickness and modulus of nanocellulose composites are investigated. Those samples exhibiting the highest Y and Ei parameters are TPS/NFC, PA6/NCC, and PVA/NCC, which can form hydrogen bonds with nanocellulose hydroxyl groups due to their ability to form hydrogen bonds. When compatibilizers are applied to nanocomposites or modified nanocellulose is applied in the polymer matrix, interphase parameters increase. In PLA/NFC composites, MA coupling agents were used to increase Y by 4000%, while Ei increased by 1045%. Moreover, the Y and Ei of CNCs modified with aminopropyl triethoxysilane (APS) in polyamide-6/NCC increased from 0.35 to 0.69 (97.14%) and 35.26 to 58.7 (66.47%). The Ji model was also investigated with and without considering the interphase thickness. As a result, the model became better fitted to experimental young modulus results by considering the interphase parameter in nanocomposites.

A graded interphase enhanced phase-field approach for modeling fracture in polymer composites

The superiority of nanosized filler particles in improving the elastic and fracture behavior of polymers, in comparison to microsized inclusions, has been substantiated by several experimental observations. Accurate modeling of crack propagation in such heterogeneous materials, however, involves resolution of complex crack topologies while taking into account the coalescence and branching of multiple cracks. Such complexity renders the traditional sharp crack modeling approaches, such as those based on the idea of partition of unity, to be of limited suitability, especially in 3D, since these involve explicit tracking of the evolving crack surfaces. Consequently, phase-field fracture approaches have come up as an attractive alternative to the traditional sharp crack models, especially when complex crack topologies need to be handled. Furthermore, standard two-phase continuum models, owing to their lack of the necessary length scale, are unable to capture the previously mentioned smaller is stronger size effect. In order to remedy this shortcoming, in context of finite strain hyperelasticity, a graded interphase based enhancement of the standard first-order continuum model was introduced in our previous work. The present contribution extends the idea of graded interphases to the phase-field fracture approach. Herein, an interphase region around filler particles, as observed experimentally, having continuously varying or graded material properties is considered. Fracture behavior of the composite material can be controlled by means of the degree of grading employed in determining the elastic and fracture properties within the interphase region. An optimal combination of the graded interphase parameters yields a tougher macroscopic response, as observed in case of tougher interphases, in comparison to the one obtained with a standard phase-field fracture model, The appropriateness of the introduced technique for modeling a wide spectrum of experimentally observed fracture behaviors, depending upon the degree of adhesion between the filler and the matrix phases, is depicted by means of extensive numerical experimentation.

Growth of the Cycle Life and Rate Capability of LIB Silicon Anodes Based on Macroporous Membranes.

This work investigated the possibility of increasing the cycle life and rate capability of silicon anodes, made of macroporous membranes, by adding fluoroethylene carbonate (FEC) to the complex commercial electrolyte. It was found that FEC leads to a decrease in the degradation rate; for a sample without FEC addition, the discharge capacity at the level of Qdch = 1000 mAh/g remained unchanged for 220 cycles and the same sample with 3% FEC added to the electrolyte remained unchanged for over 600 cycles. FEC also improves the power characteristics of the anodes by 5-18%. Studies of impedance hodographs showed that in both electrolytes (with 0% and 3% FEC, respectively) the charge transfer resistance grows with an increasing number of cycles, while Solid Electrolyte Interphase (SEI) parameters, such as its resistance and capacitance, show little change. However, the addition of FEC more than halves the overall system impedance and reduces the resistance of the liquid electrolyte and all current carrying parts as well as the SEI film and charge transfer resistances.

Interface Effects on the Viscoelastic Properties of PDMS/SiO2 Particle-Reinforced Nanocomposites

Abstract Polydimethylsiloxane/silica (PDMS/SiO2) particle-reinforced nanocomposites prepared at the present study are typical viscoelastic materials. Due to the high surface-to-volume ratio of the SiO2 nanoparticles, the interface effects on the overall properties of the nanocomposites cannot be ignored. In order to investigate the interface effects on the viscoelastic properties of the nanocomposites, a multiscale model is established in the present study, combining the molecular dynamics (MD) model of the interface at the nanoscale and the unit cell model of the nanocomposites at the mesoscale. In the MD model of the interface, the viscoelastic properties of the interphase region influenced by the interface are found to be different from that of the pure PDMS matrix and the bulk SiO2. Because the polymer chains subject to different restrictions existing in the interphase region, this region can possess high stiffness and damping properties simultaneously. The interphase parameters can be determined by the inverse multiscale simulation method, taking advantage of both the numerical model and the experimental results. Due to the interface effects, as demonstrated by the unit cell model, the dynamic shear moduli of the nanocomposites can be simultaneously improved by several times to an order of magnitude higher than that of the matrix, in consistent with experimental results. Thus, the mechanism of the interface effects enhancing the viscoelastic properties of the PDMS/SiO2 nanocomposites can be revealed in the present study, which can be useful for the design of viscoelastic nanocomposites with high stiffness and damping properties.

Heat transfer enhancement in a nanofluid saturated porous medium with cross diffusion and nonequilibrium: A regression approach

The work has been made to analyze the influence of local thermal nonequilibrium through a stretching surface in a laminar transient flow of nanofluid with the inclusion of cross diffusion. Brownian motion and thermophoresis are taken into account for the modeling of nanofluid. To describe the departure from thermal equilibrium, three temperature model has been assumed. The governing transport equations are transformed using similarity analysis and they are evaluated by Runge–Kutta–Fehlberg with shooting technique. The present results are compared with the previously published reports and they met agreement. The obtained numeric values of the boundary layer flow characteristics such as velocity, thermal, and mass transfer among the phases are illustrated graphically for different combinations of the interphase parameters. In addition, the regression study on heat and mass transfer with prominent parameters has been made to provide a highly accurate rendition and can be accessibly used in engineering problems.

Linear and Non-Linear Stability Analysis for Thermal Convection in A Bidispersive Porous Medium with Thermal Non-Equilibrium Effects

The linear instability and nonlinear stability analyses are performed for the model of bidispersive local thermal non-equilibrium flow. The effect of local thermal non-equilibrium on the onset of convection in a bidispersive porous medium of Darcy type is investigated. The temperatures in the macropores and micropores are allowed to be different. The effects of various interaction parameters on the stability of the system are discussed. In particular, the effects of the porosity modified conductivity ratio parameters, and , with the inter-phase momentum transfer parameters and, on the onset of thermal Convection are also considered. Furthermore, the nonlinear stability boundary is found to be below the linear instability threshold. The numerical results are presented for free-free boundary conditions.

An ABAQUS® plug-in for generating virtual data required for inverse analysis of unidirectional composites using artificial neural networks

This paper presents a robust ABAQUS® plug-in called Virtual Data Generator (VDGen) for generating virtual data for identifying the uncertain material properties in unidirectional lamina through artificial neural networks (ANNs). The plug-in supports the 3D finite element models of unit cells with square and hexagonal fibre arrays, uses Latin-Hypercube sampling methods and robustly imposes periodic boundary conditions. Using the data generated from the plug-in, ANN is demonstrated to explicitly and accurately parameterise the relationship between fibre mechanical properties and fibre/matrix interphase parameters at microscale and the mechanical properties of a UD lamina at macroscale. The plug-in tool is applicable to general unidirectional lamina and enables easy establishment of high-fidelity micromechanical finite element models with identified material properties.

The effects of interphase parameters on transverse elastic properties of Carbon–Carbon composites based on FE model

A modified random fiber removal algorithm is proposed to numerically study transverse elastic properties of unidirectional carbon fiber reinforced pyrolytic carbon (C/C) composites. This method can efficiently generate the Representative Volume Element (RVE) of composites with random distribution fibers. On the basis of the numerical homogenization strategy, the effect of interphase between carbon fiber and pyrolytic carbon on the mechanical behaviors of unidirectional C/C composites are investigated. Meanwhile, periodic boundary conditions and linear elastic constitutive materials are taken into account. For validation, numerical calculations are compared with these obtained by atomic force microscopy (AFM) tests, which shows that more accurate results will be pursued when the interphases are considered. In addition, the influences of interphase parameters including the thickness, modulus, and Poisson’s ratio, on the effective transverse behavior of unidirectional C/C composites are studied numerically.The results demonstrate that the effective transverse properties of unidirectional C/C composites are mainly determined by the interphase modulus and independent of the interphase Poisson’s ratio. If the interphase thickness (less than 140 nm) of unidirectional C/C composites are very small, the modulus of interphase beyond 8 GPa makes little effect on the effective transverse properties.

Simulation of tensile strength for halloysite nanotubes/polymer composites

There are limited equations for determining the mechanical performance of halloysite nanotubes (Hal)/polymer samples, and these equations ignore the reinforcing efficacy of the interphase zone. In this article, the Kolarik system is used to determine the tensile strength of Hal-reinforced nanocomposites by Hal size, Hal concentration, and interphase properties. In addition, Pukanszky model is modified for this material type to account for effective Hal concentration based on the advanced Kolarik model. Numerous sets of experimental data for several samples and parametric inspections endorse the developed models. Both interphase depth and power directly govern the nanocomposite's strength and the interphase factor “A” in the advanced Kolarik model. The lowest ranges of interphase properties lead to the lowest level of “A,” and at this level, there is no strengthening of the nanocomposites. The Hal radius (R) of 10 nm and Hal length (l) of 3 μm lead to the highest “A” of 50 and the maximum relative strength of 4.5 (350% improvement in nanocomposite's strength), whereas Hal with R > 50 nm and l < 1.5 μm cannot reinforce the sample. Moreover, the Hal content, interphase parameter “B,” and interphase thickness have a direct relationship with nanocomposite's strength according to the developed Pukanszky model, whereas the Hal radius has an inverse relationship.

Effects of critical interfacial shear strength between polymer and nanoclay on the Pukanszky's “B” interphase factor and tensile strength of polymer nanocomposites

This paper aims to develop the “B” interphase parameter and Pukanszky model for tensile strength of polymer clay nanocomposites assuming critical interfacial shear strength (τc) providing the stress transferring between polymer and nanoparticles. The clay properties express the “τc” and both “τc” and interfacial shear strength (τ) develop the effective thickness, strength and volume fraction of interphase region as well as the effective volume fraction of clay in nanocomposites. The effective terms are applied to expand the “B” interphase parameter and Pukanszky equation. The experimental data of tensile strength for some samples and the parametric investigations validate the developed equations for “B” and tensile strength of nanocomposites. All parameters consistently control the “B” and tensile strength. Low critical interfacial shear strength, high interfacial strength, thick interphase, high interfacial shear strength, high aspect ratio (length per thickness) of clay and a small number of clay in the stacks produce a high “B” and improve the tensile strength of nanocomposites. The absence of interphase section in nanocomposites largely decreases the “B” and very thin interphase deteriorates the strengthening efficiency of nanoclay in nanocomposites.

Effect of interphase parameters on elastic modulus prediction for cellulose nanocrystal fiber reinforced polymer composite

Abstract In this study, the effective elastic modulus (Ec ) of a cellulose nanocrystal fiber reinforced polymer composite was evaluated using the Mori-Tanaka and finite element (FE) model. The FE model was generated using a representative volume element with a periodic boundary condition. The mass fractions of the fiber in the composites (MFf ) were set to 1, 2, and 3 wt.%. Elastic modulus values for interphase were input and were either uniform or exhibited a gradient. The E c for the uniform interphase region increased significantly with MFf , but was relatively low for interphase regions exhibiting a gradient. The results show that interphase parameters must be considered carefully when predicting Ec using the FE model.

A novel bisection method based algorithm to quantify interphase in epoxy alumina nanocomposites

Polymer nanocomposites (PNCs) are emerging materials for the future due to their superior material characteristics with respect to base polymer and composites formed with traditional micro sized fillers. Researchers are concordant in attributing the improved properties of PNCs to large proportion of polymer-filler interaction zone (or an interphase). However, literature is indeed scanty to characterize interphase in terms of its size and properties. To come into possession of fine-tuned material properties through optimal use of naofillers, characterization of interphase is necessary. In this work, we propose a novel algorithm to characterize interphase in terms of its permittivity and thickness. Epoxy resin (LY556) is used as base polymer and aluminum oxide (Al2O3, average particle size = 50 nm) is used as filler material. Filler particles are surface treated using silane. Dispersion of nano filler in polymer matrix is verified using scanning electron microscopy (SEM). Dielectric spectroscopic measurements are carried out to measure permittivity over a frequency range of 10-2 to 107 Hz. A finite element based numerical model is developed to estimate effective permittivity of composites for different values of assumed interphase parameters (i.e. thickness and permittivity). Bisection method based algorithm is devised to assign actual thickness and permittivity to interphase based on the best fit of experimental and simulated results.

A Simple Technique for Calculation of an Interphase Parameter and Interphase Modulus for Multilayered Interphase Region in Polymer Nanocomposites via Modeling of Young’s Modulus

In this work, a simple technique is suggested applying the simple models for Young’s modulus of polymer nanocomposites to calculate the Y interphase parameter and interphase modulus for multilayered interphase in polymer nanocomposites. The developed model is compared to the experimental results of several samples to examine its correctness. The effects of Y on the Young’s moduli of interphase Ei and polymer nanocomposite Ec are also studied. The different levels of Y parameter calculated for the reported samples demonstrate the various extents of interphase properties. The results show that the high levels of bothY parameter and nanofiller modulusEp are required to achieve a desirable interphase modulus in polymer nanocomposites.

Modeling of interphase strength between polymer host and clay nanoparticles in nanocomposites by clay possessions and interfacial/interphase terms

This article develops the equations for interphase strength and Pukanszky's “B” interphase parameter in clay nanocomposites as a function of clay properties and interfacial/interphase parameters. The experimental results of tensile strength for various samples are applied to validate the developed models. Moreover, the developed equations for interphase strength and “B” are examined by parametric analyses. All parameters acceptably influence the interphase strength and “B” confirming the advanced equations. Poor critical interfacial shear strength and strong polymer matrix positively handle the interphase strength, but only high critical interfacial shear strength causes a poor interphase. Additionally, the exceptionally poor interfacial shear strength or very short clay significantly deteriorates the interphase strength. Furthermore, only thick clay mainly weakens the interphase region demonstrating that the thick clay declines the efficiency of interphase area in the nanocomposites.

Effects of critical interfacial shear strength between a polymer matrix and carbon nanotubes on the interphase strength and Pukanszky's "B" interphase parameter.

In this paper, the “B” interphase parameter in the Pukanszky model and interphase strength for polymer carbon nanotube (CNT) nanocomposites are expressed by the critical interfacial shear strength (τc) and interfacial shear strength (τ) between a polymer matrix and CNTs. A suggested model and a developed Pukanszky model for tensile strength of nanocomposites are combined to develop the equations for “B” and interphase strength. Many experimental data for various samples confirm the models. The impacts of all parameters on the “B” and interphase strength are explained to approve the developed equations. The contour plots display the same trends for the roles of all parameters in the “B” and interphase strength. Low “τc”, high “τ”, thin and large CNTs as well as a dense interphase are ideal to obtain the high levels for “B” and interphase strength. Among the studied parameters, CNT size largely controls the “B” and interphase strength, while the waviness and strength of CNTs play insignificant roles.

Evaluating unidirectional composite thermal conductivities through engineered interphase

ABSTRACTEffect of fibre/matrix interphase parameters, including thickness and material properties on the equivalent thermal conductivities of unidirectional fibre-reinforced polymer composites. A unit cell-based micromechanical method is proposed to evaluate the thermal conductivities of unidirectional multi-phase composites. The longitudinal thermal conductivity of unidirectional fibre-reinforced polymer matrix composites is seen to be independent of interphase region. When the thermal conductivity of interphase is higher than that of matrix, the increase of interphase thickness leads to an improvement in transverse thermal conductivity of fibre-reinforced polymer composites. The influences of fibre volume fraction, orientation angle and shape of cross-section as well as temperature on the thermal conducting behaviour are widely examined. The model predictions are in good agreement with the experimental data reported in the literature.

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.

Effect of “Z” factor for strength of interphase layers on the tensile strength of polymer nanocomposites

The influences of “Z” factor for the strength of interphase layers on the tensile strength of polymer nanocomposites and various interphase properties are explained applying three approaches including developed Leidner‐Woodhams, Pukanszky, and Callister‐Rethwisch models. All models and equations for interphase parameters are developed based on a multi‐layered interphase in different polymer nanocomposites. The calculations reveal that the role of “Z” factor is highlighted when much volume fraction of nanofiller ( ) is used attributed to the high probability of nanoparticles agglomeration and poor interfacial properties in this condition. However, both “ ” and “Z” parameters positively affect the tensile strength. Additionally, the highest values of interphase properties including “B” in Pukanszky and “s” in Callister‐Rethwisch models are achieved by the high levels of nanofiller strength and “Z” factor. POLYM. COMPOS., 40:1117–1122, 2019. © 2018 Society of Plastics Engineers

Prediction of filler/matrix interphase effects on AC and DC electrical properties of carbon reinforced polymer composites

This study predicts the effect of the conducting filler/insulating matrix interphase on the electrical properties of two series of percolated systems, differing from the type of carbon black particles mixed in an amine‐cured epoxy matrix, diglycidylic ether of bisphenol F. To take into account the interactions between the conducting filler and the matrix, as well as filler–filler overlapping, we introduce three parameters, characteristic of the interphase zone, such as concentration, conductivity and volume, on the generalized effective medium (GEM) model for DC and AC electrical conductivities. These interphase parameters, characterizing the boundary of the shaded zone between the macromolecular chain and the conducting particles, depend on the filler type and concentration. One output of GEM‐modified model is that it provides a mean to estimate the volume, concentration and intrinsic conductivity of the interphase in a composite by fitting the experimental data over a broad range of frequency. POLYM. COMPOS., 40:346–352, 2019. © 2017 Society of Plastics Engineers