Particle-reinforced Composite Materials Research Articles

Material instability-induced extreme damping in composites: A computational study

We investigate the effective viscoelastic performance of particle-reinforced composite materials whose particulate phase undergoes a material instability resulting in temporarily non-positive-definite elastic moduli. Recent experiments have shown that phase transitions in geometrically-constrained composite phases (such as in particles embedded in a stiff matrix) can lead to stable non-positive-definite elastic moduli, and they hinted at strong damping increases that can be achieved from such metastable composite phases. All previous theoretical efforts to explain such phenomena have used simplistic one-dimensional models or they were based on composite bounds and specific two-phase solids. Here, we study particle–matrix composites with periodic randomized particle dispersion. A finite element discretization is used in combination with a sophisticated nonlinear solver in order to perform the numerous calculations in a feasible amount of computing time. Our computational analysis shows that stable non-positive-definite inclusion moduli can indeed lead to extreme damping increases (i.e. greatly exceeding the intrinsic damping of each composite phase) and that such extreme damping arises from a shift in microstructural mechanisms.

GA-fuzzy based estimation of equivalent hardness of particle reinforced flexible mould material composites

In the present work, an extensive experimental study on the equivalent hardness of various particle reinforced flexible mould materials is carried out. From the experimental study, it has been observed that the equivalent hardness of a composite mould material depend on many factors, such as filler content, morphology and type of filler particles, etc. Some of the factors may be correlated with each other and sometimes belong to uncertainty and ambiguity such as dispersion state of filler in the matrix, non-uniform filler particle size and shape. Moreover, the formation of physical bonding of filler particles with matrix polymer is highly complex and non-linear, because they are depending on such kind of parameters that are associated with uncertainty and ambiguity. By realizing it, an effort has been made to develop a model using a GA-fuzzy approach to estimate equivalent hardness of particle reinforced mould materials. An appropriate model is decided by carrying out a comparative analysis on the effectiveness of developed models based on different structures of TSK-type fuzzy rule-consequent function with the experimental measurements. It is found that better performance is envisaged by TSK-type fuzzy model which considers the variables namely hardness of polymer, hardness of filler material, volume fraction of filler particle as well as interactions among them in the rule- consequent function. In addition, the developed model seems to possess a generic one which can be applicable to a wide range of two-phase particle-reinforced composite mould materials.

Impact–abrasion wear characteristics of in-situ VC-reinforced austenitic steel matrix composite

In this investigation, in-situ precipitation of vanadium carbides was employed to reinforce Fe–13Mn and Fe–13Mn–3W alloys by means of conventional melting and casting route. Microstructures were characterized by optical and scanning electron microscopy techniques.Mechanical properties of the materials were determined by hardness, impact toughness and tension tests. It was observed that tungsten improved the strength of the matrix and the reinforcements as well as tensile properties and work hardening rate of the VC-reinforced composite. Ball mill abrasion test was utilized to simulate impact–abrasion wear condition using two types of abrasive minerals. The results showed that the degree of benefit to be gained by the use of in-situ VC-reinforced composite materials depends strongly on crush strength of the abrasives. It was found that the studied particle-reinforced composite materials were only advantageous when the abrasives were relatively soft, providing low-stress abrasion condition.

Inverse Stochastic Homogenization Analysis for a Particle-Reinforced Composite Material with the Perturbation-Based Approach

Inverse Stochastic Homogenization Analysis for a Particle-Reinforced Composite Material with the Perturbation-Based Approach

Finite element network approximation of conductivity in particle composites

A new finite element method computes conductivity in some unstructured particle-reinforced composite material. The 2-phase material under consideration is composed of a poorly conducting matrix material filled by highly conducting circular inclusions which are randomly dispersed. The mathematical model is a Poisson-type problem with discontinuous coefficients. The discontinuities are huge in contrast and quantity. The proposed method generalizes classical continuous piecewise affine finite elements to special computational meshes which encode the particles in a network structure. Important geometric parameters such as the volume fraction are preserved exactly. The computational complexity of the method is (almost) proportional to the number of inclusions. This is minimal in the sense that the representation of the underlying geometry via the positions and radii of the inclusions is of the same complexity. The discretization error is proportional to the distance of neighboring inclusions and independent of the conductivity contrast in the medium.

Bending Strength of Cast Materials Reinforced with Hard Particles

Particle reinforcement via the insertion of hard particles is a promising process in materials reinforcing. Particle-reinforced spheroidal graphite martensitic cast iron (SGMC), in which mixed particles of cermet and cemented carbide are dispersed, was achieved by an insertion process. A four-point bending strength test was applied to evaluate the particle composite material. An evaporative pattern process was used on the bending-test specimen to form a composite layer in the central part. Using a combination of three sizes of cermet particles and two sizes of cemented-carbide particles, the bending strength was found to increase with each small-particle combination. The Weibull coefficient m of the four-point bending strength of the particle-reinforced composite material (PRCM) ranged from 4 to 13, and m was large in the specimen with large bending strength.

Identification of a microscopic randomness of a particle reinforced composite material with Monte-Carlo Simulation and inverse homogenization analysis

This paper describes a detailed procedure for identifying a microscopic randomness of a particle-reinforced composite material considering a microscopic uncertainty in elastic property of component materials of a particle reinforced composite material. Some reports on the stochastic homogenization analysis considering a microscopic random variation can be found in literatures. A microscopic stress field will take an influence of the microscopic variation, the stochastic microscopic stress analysis will be also important. In the previous reports, it is assumed the microscopic random variation is known. However, it is sometimes difficult to identify a microscopic random variation in a composite material especially after manufacturing process. An identification process for a microscopic randomness with solving an inverse problem, therefore, will be needed for the stochastic microscopic stress analysis. In this paper, an inverse stochastic homogenization problem is tried to be analysed with the inverse homogenization analysis and the Monte-Carlo simulation for the stochastic homogenization analysis. With numerical results, accuracy of the inverse analysis is discussed.

セラミックス粒子強化複合材料の疲労損傷評価に関する研究 : 第1報,AE信号のカオス解析と熱履歴の影響

セラミックス粒子強化複合材料の疲労損傷評価に関する研究 : 第1報,AE信号のカオス解析と熱履歴の影響

Constitutive behaviors of composites with interface debonding: the extended Mori–Tanaka method for uniaxial tension

Debonding of particle/matrix interfaces can significantly affect the macroscopic behavior of composite materials. We have used a nonlinear cohesive law for particle/matrix interfaces to study the effect of interface debonding on the macroscopic behavior of particle-reinforced composite materials subject to uniaxial tension. The Mori–Tanaka method, which is suitable for composites with high particle volume fraction, is extended to account for interface debonding. At a fixed particle volume fraction, small particles lead to the hardening behavior of the composite while large particles yield softening. The interface sliding may contribute significantly to the macroscopic behavior of the composite.

A Three-Dimensional Strain Gradient Plasticity Analysis of Particle Size Effect in Composite Materials

Recent experiments on particle-reinforced metal-matrix composite materials have shown particle size effects. Small particles tend to give larger plastic work hardening than large particles at the same particle volume fraction. Prior models used to study the particle size effect are based on the strain gradient plasticity theories, and these models are mainly axisymmetric models with vanishing lateral stress tractions in order to represent the uniaxial tension condition. However, the prior results fall short to agree with the experimental data. A three-dimensional (3D) unit-cell model is adopted in the present study. The periodic boundary conditions are imposed for the 3D unit cell to ensure the compatibility of the unit cell before and after the deformation. The particles are elastic, while the metal matrix is elastic-plastic and is characterized by the conventional theory of mechanism-based strain gradient plasticity, which is established from the Taylor dislocation model but does not involve the higher-order stress. It is shown that the 3D unit-cell model with the periodic boundary conditions gives better agreements with the experimental data than the unit-cell model with the traction-free boundary conditions on the lateral surfaces.

An anti-interpenetration model and connections between interphase and interface models in particle-reinforced composites

Linear spring interface model and interphase model are often used to simulate the interface behaviour of particle-reinforced composite materials. However, the former may give rise to nonphysical interpenetration at the interface between a particle and the surrounding material. In this paper, first, a model is presented to prevent the interpenetration phenomenon at the interface. This model can be used together with a given linear or nonlinear interface model to calculate the stress field in particle-reinforced composites with imperfect interface bonding condition, or with debonding damage. Second, the connections between the thin interphase model and interface models are studied for spherical particle-reinforced composites. It is found that while a relatively thin and compliant interphase can be well approximated by the equivalent linear spring interface model, a relatively thin and stiff interphase can be well approximated by the equivalent interface stress model. For the latter, the relations between the equivalent interface moduli and the interphase stiffness and thickness are presented.

21106 球状粒子強化型複合材料の巨視的弾性係数の評価(材料力学(シミュレーション))

In this paper, it is evaluated global averages of elastic properties for particle-reinforced composite materials including spherical inclusions, using a three dimensional analysis based on the finite element method. In the numerical analysis, it is assumed that particles of the same radius are arrayed in body-centered cubic. The volume fraction of the composite material is determined by the radius of particles. A cube including tow particles is as a unit cell and given forced-displacement. And then the global Young's modulus and the global Poisson's ratio of the composite material are obtained from the reaction forces. As an example, it is considered that a composite material consists of epoxy and glass. The obtained results are compared with results by methods based on the Eshelby's equivalent inclusion theory.

A model for predicting the evolution of damage in viscoelastic particle-reinforced composites

A viscoelastic cohesive zone model is employed within the framework of a finite element code to analyze a two-phase viscoelastic particle-reinforced composite material consisting of a relatively stiff aggregate embedded in a copolymer binder. The composite of interest, LX17, is noted to have a very large aggregate volume fraction and as such, aggregate grain boundaries were generated within finite element meshes along which viscoelastic cohesive zones have been embedded to model the binder. It has been observed experimentally that the majority of damage in LX17 occurs within the binder, and thus, a damage evolution law has been applied to the viscoelastic cohesive zones that is phenomenological in nature. The responses obtained for the composite from the FEM analysis are then compared to the experimental data compiled by Lawrence Livermore National Labs for various constant strain rate tests conducted by Groves and Cunningham [Tensile and compressive mechanical properties of billet pressed LX17-1 as a function of temperature and strain rate. UCRL-ID-137477. Internal report prepared for Lawrence Livermore National Laboratory, Livermore, CA].

A statistical micromechanics-based multi-scale framework for effective thermomechanical behaviours of particle reinforced composites

Particle-reinforced composite materials have been widely used as they can exhibit nearly isotropic material properties and are often easy to process. Some silicon carbide particle reinforced aluminium composites with high volume concentration of reinforcement exhibit excellent thermophysical properties and can be used in advanced electronic packaging. In this paper, a statistical micromechanics-based multi-scale material modelling framework is introduced to describe the macroscopic effective thermomechanical properties of the particle-reinforced composite. The formulation differs from most of the existing methods in that the interaction effects among the reinforcing particles are directly accounted for by considering pair-wise interaction and statistical information on particle distribution is included. The strain and stress concentration factor tensors that relate the local average strain and stress fields, respectively, to the corresponding global average fields are derived according to the theory of average fields. The effective coefficient of thermal expansion for the particle-reinforced composite material is derived. Comparisons of the prediction from the proposed framework to the results from other existing methods are presented. The results are expressed in analytical closed-form in terms of the thermal and mechanical properties of the two constituent phases and the volume fraction of particles. No parameter estimation or data fitting is required.

714 Modified Analytical Model for Different Matrix Materials of the Particle-Reinforced Aluminum-Matrix Composites at High Strain Rate

In order to understand the compressive behaviors of particle-reinforced metal-matrix composite (MMCs) material for its potential usage on light armor, large compressive plastic deformation of MMC composite is investigated through numerical modeling at high strain rates. Based on the work of Li and Remash, the numerical modeling is performed using axisymmetric unit cell model, with the particles treated as elastic ellipsoids or cylinders embedded within a visco-plastic matrix. Five particle volume fractions from 10% to 50% and three aluminum matrix materials LY12CZ, LC4 and 7075 are analyzed. The contribution of this work is to add a term to the original analytical model. Thus it can take account the effect of strain hardening of the matrix material. The modified analytical model introduced here is able to better describe the features of the computational predictions at certain extent.

Research on the cutting performance of carbon nitride cutting tools

A new kind of superhard material C 3N 4 has been developed in recent years. C 3N 4 film is deposited on the surface of cutting tools by the dc active magnetron-sputtering method. It has ultrahigh hardness approaching that of diamond. A high speed steel (HSS) twist drill coated with C 3N 4 film is applied to drilling hole process in steel workpiece in cutting tests, the tool life being found to increase greatly. When the C 3N 4 film is coated on cemented carbide inserts, whilst the cutting performance is improved, it is not good enough. When a C 3N 4 coated cemented carbide tool is used in machining particle reinforced composite material (PRCM), the cutting performance is almost as poor as when machining with an uncoated tool. The data of the mechanical properties and cutting tests of about this kind of new coated cutting tool are given in this paper, showing that C 3N 4 has a promising future.

Modeling the effects of hole distribution in perforated aluminum sheets II: minimum strength failure paths

A method to predict the failure path and mechanical response of metal sheets with randomly distributed holes under uniaxial tension has been developed. The method considers all possible failure paths and estimates the load required to break the perforated sheet along these paths. The predicted ultimate strength of the sheet is obtained by finding the failure path with the lowest possible load. The results from the model are compared to tensile experiments on a set of perforated aluminum sheets with different hole patterns. We found that the model, though relatively simple, could capture the effects that hole distribution had on the ultimate strength of the sheet. The ideas presented here could be extended to model the effect of reinforcement distribution in particle-reinforced composite materials.

Computational mesomechanics of particle-reinforced composites

Numerical models of deformation, damage and fracture in particle-reinforced composite materials, based on the method of multiphase finite elements (MPFE) and element elimination technique (EET), are presented in this paper. The applicability of these techniques for different materials and different levels of simulation was studied. The simulation of damage and crack growth was conducted for several groups of composites: WC/Co hard metal alloys, Al/Si and Al/SiC composites on macro- and mesolevel. It is shown that the used modern techniques of numerical simulation (MPFE and EET) are very efficient in understanding deformation and damage evolution in heterogeneous brittle/ductile materials with inclusions.

Numerical identification of properties of particle-reinforced composite materials

The paper deals with numerical identification of the average elastic properties of particle-reinforced composite materials. The finite element method for the determination of deformation energy of the characteristic volume element was used. In earlier analytical investigations, an approximation function of the averaged elastic properties of the composite was derived. An identification procedure allows the estimation of the unknown approximation parameters from numerical experiments. The obtained functions describe precisely the numerical data for any relationships between constituents of the material.

A step-by-step method of rule-of-mixture of fiber- and particle-reinforced composite materials

A new method of rule-of-mixture is presented for predicting the mechanical properties of fiber- and particle-reinforced composite materials. The composite material is composed through a hypothetical process in which the matrix is reinforced one-by-one with reinforcing materials (fibers or particles). The mechanical properties of the composed material are obtained step-by-step using the cylinder model for fiber-reinforced materials and the sphere model for particle-reinforced materials. Results obtained by the present method are compared with those of other methods and experimental results. It is found that, for the longitudinal modulus, the present method gives equally good prediction as other methods. For the transverse modulus and shear modulus, the results obtained by the present method show better agreement with experimental results.