Matrix-based Composites Research Articles

A simple model to predict effective conductivity of multicomponent matrix-based composite materials with high volume concentration of particles

For high-contrast-component-property composites, most popular effective medium approximations that are based on the dilute analytical solution for an ellipsoidal inclusion embedded in an infinite matrix diverge significantly from each other and from experimental and numerical data. This paper discusses the challenges in this research area and proposes some homogenization strategies to solve the problems. In this work, a simple effective medium approximation is constructed to predict the effective conductivity of multicomponent matrix-based composites containing high concentrations of particles in d-dimensional space (d=2,3). The maximum volume fraction that depends on particle size distribution and the geometric approximation are accounted for in the micromechanical model to obtain new closed-form solutions. A flexible version of the model containing a free parameter is proposed to make the predictions more accurate at very high-volume fraction of inclusions. Applications are illustrated by comparing the theoretical predictions with the available experimental data or finite element simulations for various types of material to show the agreeable results close to the maximal packing points of the interactions.

Analysis of mechanical and micro structural property of aluminium metal matrix (LM25) composite hybrid with nano silicon carbide and nano alumina as reinforcement particles

The effect of reinforcement of silicon carbide nano particle (SiCnp) and nano alumina particle (Al2O3np) in base matrix composite of aluminium (LM25) alloy is studied. By using stir casting method, the hybrid aluminium matrix-based nano composites (AMNC) samples are made. The addition of nano particles in a base matrix increases the strength compared to pure LM25 aluminium alloy. The distributions of reinforcement particles are evident in the EDAX and SEM analysis. Both the density test and compression test results of AMNC samples are compared with the pure LM25 aluminium alloy. By increasing the percentage of reinforcements in matrix phase influences the increase in their mechanical properties. Aluminium matrix-based nano composites having high density, compression strength and wear resistance than pure aluminium. The above results indicates that the AMNC have excellent corrosion resistance and good fluidity but limited strength in high temperature.

Evaluation of physico-mechanical characteristics of cashew nut shell liquid-epoxy composites with Borassus and Tamarind fruit fibres as reinforcements

ABSTRACTIn this study, Cashew Nut Shell Liquid (CNSL)-epoxy matrix-based composites reinforced with borassus and tamarind fibres were fabricated using compression moulding technique. Three different types of composites were fabricated, namely Borassus fruit fine fibre/CNSL-epoxy composites (BF composites), Tamarind fibre/CNSL-epoxy composites (TF composites) and Tamarind/Borassus fruit fine fibre CNSL-epoxy hybrid composites (HB composites). In addition, CNSL-epoxy neat polymer was also fabricated for comparison. Physical properties such as micro-hardness, void percentage, and mechanical properties like tensile, flexural, Interlaminar Shear Strength (ILSS), and impact strength were investigated. Scanning Electron Microscope (SEM) was used to study the failure mechanism of the composites. Experimental results indicate that tensile and flexural properties of BF composites were higher when compared to TF and HB composites. Micro-hardness and impact strength of HB composites were better than the others. SEM images indicated better fibre-matrix bonding in BF composites indicating improved resistance to delamination. Thus, borassus and tamarind fibre reinforced CNSL-epoxy composites can be used as an alternative material for light to moderately loaded structural engineering applications.

Preparation and characterisation of Al‐doped ZnO and PVDF composites

A single organic composite material having high dielectric constant is difficult to meet the needs of the market. Nowadays, polymer matrix-based composites have become a promising option that researchers are focusing on. Al-doped zinc oxide (ZnO) and composites containing ZnO as reinforcement and poly(vinylidene fluoride) (PVDF) as matrix were prepared. The microstructure of composites was analysed by scanning electron microscope and transmission electron microscopy techniques. The chemical structures and crystallisation behaviour of the materials were investigated by the means of FT-IR and X-ray diffractometer. ZnO, having both rod- and sheet-shaped, was evenly distributed within the PVDF material. Additionally, the dielectric properties and breakdown field strength of composite were tested. As the content of the fillers was kept steady, the dielectric constant of the composite material increased proportionally with the Al content. Thus, a composite containing 10% ZnO with 7% Al displayed a dielectric constant of 18.5 at 100 Hz, twice when compared with the pure ZnO/PVDF composites. This phenomenon was attributed to ZnO semiconductor properties which can significantly improve the conductive nature of the materials.

Infrared thermography to evaluate thermoplastic composites under bending load

Thermoplastic matrix-based composites are becoming ever more popular due to their many advantages over both metals and thermoset matrix-based composites. In particular, they can be tailored by the addition of a compatibilizing agent to the matrix, which allows to create a multitude of materials. Of course, each of these materials requires characterization for an appropriate exploitation. In this context, infrared thermography represents a viable inspection means since it is non-contact, non-intrusive and can be used to monitor the entire existence of a product, from its manufacturing process to completion as well as in-service life. In this work, several composite materials based on a polypropylene matrix, which may be neat, or modified by addition of a certain amount of a specific compatibilizing agent, and reinforced with glass, or jute, woven fibres are considered and subjected to cyclic bending tests. Infrared thermography is used for monitoring the bending event.

YSZ-Reinforced Mg-Based Amorphous Composites: Processing, Characterisation & Corrosion

MgZnCa amorphous matrix-based composites whereby reinforcing the matrix with suitable reinforcements to achieve enhanced mechanical, biomedical and anti-corrosion properties have been studied here. Here, MgZnCa-based composites have been developed with different amounts (0-25%wt) of yttria-stabilized zirconia (YSZ) reinforcement phase. The aim is to understand the corrosion behaviors of YSZ-reinforced MgZnCa-based composites in physiological saline solution. It is found that the incorporation of YSZ into amorphous MgZnCa matrix can cause crystallization of the amorphous matrix. The higher the YSZ introduced, the higher the degree of crystallization, and a fully crystalline matrix is obtained at a YSZ concentration of 25%. Electrochemical testing and ion release measurements, revealed that the composite with 8%YSZ possesses the smallest corrosion current density and the least ion release rate. Surface morphology analysis indicates a much stronger anti-corrosion ability of 8%YSZ-reinforced MgZnCa composite.

On the effective medium approximations for the properties of isotropic multicomponent matrix-based composites

From our three-point correlation bounds, which are based on minimum energy principles and Hashin–Shtrikman polarization trial fields, the polarization approximations for the effective conductivity and elastic moduli of isotropic multicomponent suspension of particles in a continuous matrix, generally in d-dimensions, have been deduced, which account for near distance inclusion-matrix interaction, but not the details of far distance inter-particle ones. The approximations, always obeying Hashin–Shtrikman bounds for isotropic multicomponent materials, are compared favourably with other approximations and finite element results.

The effective medium and the average field approximations vis-à-vis the Hashin–Shtrikman bounds. I. The self-consistent scheme in matrix-based composites

The effective medium approximation (EMA) and the average field approximation (AFA) are two classical micromechanics models for the determination of effective properties of heterogeneous media. They are also known in the literature as ‘self-consistent’ approximations. In the AFA, the basic idea is to estimate the actual average field existing in a phase through a configuration in which a typical particle of that phase is embedded in the homogenized medium. In the EMA, on the other hand, one or more representative microstructural elements of the composite is embedded in the homogenized effective medium subjected to a uniform field, and the demand is made that the dominant part of the far-field disturbance vanishes. Both parts of this study are concerned with two-phase, matrix-based, effectively isotropic composites with an inclusion phase consisting of randomly oriented particles of arbitrary shape in general, and ellipsoidal shape in particular. The constituent phases are assumed to be isotropic. It is shown that in those systems the AFA and EMA give different predictions, with the distinction between them becoming especially striking regarding their standing vis-à-vis the Hashin–Shtrikman (HS-bounds). While due to its realizability property the EMA will always obey the bounds, we show that there are circumstances in which the AFA may violate the bounds. In the AFA for two-phase matrix-based composites, the embedded inclusion is a particle of the inclusion phase. If the particle is directly embedded in the effective medium, the method is called here the self-consistent scheme–average field approximation (SCS-AFA), and will obey the HS-bounds for an inclusion shape that is simply connected. If the embedded entity is a matrix-coated particle, then the method is called the generalized self-consistent scheme–average field approximation (GSCS-AFA), and may violate the HS-bounds. On the other hand, in the EMA for matrix-based composites with well-separated inclusions, we indicate that in view of its premises the embedding with a matrix-coated particle generally becomes the appropriate one, and the method is thus called the generalized self-consistent scheme–effective medium approximation (GSCS-EMA). Part I of this study is concerned with SCS-AFA in dielectrics and elasticity, and Part II with the GSCS-AFA and GSCS-EMA in dielectrics.

The effective medium and the average field approximations vis-à-vis the Hashin–Shtrikman bounds. II. The generalized self-consistent scheme in matrix-based composites

The present Part II of this two-part study is concerned with the average field approximation (AFA), and the effective medium approximation (EMA) in two-phase matrix-based dielectric composites through the use of an auxiliary configuration in which a particle of the inclusion phase is first surrounded by some matrix material, and then embedded in the effective medium. Those models will be referred as the generalized self-consistent scheme-average field approximation (GSCS-AFA), and the generalized self-consistent scheme-effective medium approximation (GSCS-EMA). We show that there are four types of the GSCS-AFA and a single type of the GSCS-EMA. In this paper the application of those models to dielectric composites with isotropic constituents and an inclusion phase that consists of randomly oriented ellipsoidal particles will be studied. The analytical solution of the auxiliary problem, which consists of an ellipsoidal particle confocally surrounded by a matrix shell and embedded in the effective medium, is achieved by means of ellipsoidal harmonics. Our results show that the effective property predictions of the GSCS-EMA and GSCS-AFA for the considered systems differ from each other, and more importantly, out of the four GSCS-AFA models, three of them violate the Hashin–Shtrikman bounds. The predictions of the GSCS-EMA obey the bounds. It is then shown that the version of the GSCS-AFA which obeys the Hashin–Shtrikman bounds for an inclusion phase with randomly oriented ellipsoids will violate them in the case of a particle shape which is not simply connected. Moreover, it turns out that the SCS-AFA studied in Part I also violates the Hashin–Shtrikman bounds in that case; the EMA, as expected, owing to its realizability property, continues to obey the bounds. Among the AFA and EMA in matrix-based composites, the GSCS-EMA therefore stands out as the method to be recommended.

Mechanical, Morphological, and Thermal Characterization of Compression-Molded Polymer Biocomposites

In the present communication, synthesis and characterization of short Saccaharum cilliare fiber reinforced resorcinol–formaldehyde (RF) polymer matrix-based composites through compression molding technique are reported. Experimental results reveal that when Saccaharum cilliare fibers are incorporated into the resorcinol–formaldehyde polymer matrix, mechanical properties such as tensile strength, compressive strength, flexural strength, and wear resistance of the matrix increase up to 30% fiber loading and then decrease for higher fiber loading. Morphological and thermal studies of the matrix, Saccaharum cilliare fiber, and short fiber-reinforced polymer composites have also been carried out. The results obtained emphasize utilization of these fibers as potential reinforcing materials in bio-based polymer composites.

Cassava bagasse cellulose nanofibrils reinforced thermoplastic cassava starch

Cellulose cassava bagasse nanofibrils (CBN) were directly extracted from a by-product of the cassava starch (CS) industry, viz. the cassava bagasse (CB). The morphological structure of the ensuing nanoparticles was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), presence of other components such as sugars by high performance liquid chromatography (HPLC), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) experiments. The resulting nanofibrils display a relatively low crystallinity and were found to be around 2–11 nm thick and 360–1700 nm long. These nanofibrils were used as reinforcing nanoparticles in a thermoplastic cassava starch matrix plasticized using either glycerol or a mixture of glycerol/sorbitol (1:1) as plasticizer. Nanocomposite films were prepared by a melting process. The reinforcing effect of the filler evaluated by dynamical mechanical tests (DMA) and tensile tests was found to depend on the nature of the plasticizer employed. Thus, for the glycerol-plasticized matrix-based composites, it was limited especially due to additional plasticization by sugars originating from starch hydrolysis during the acid extraction. This effect was evidenced by the reduction of glass vitreous temperature of starch after the incorporation of nanofibrils in TPSG and by the increase of elongation at break in tensile test. On the other hand, for glycerol/sorbitol plasticized nanocomposites the transcrystallization of amylopectin in nanofibrils surface hindered good performances of CBN as reinforcing agent for thermoplastic cassava starch. The incorporation of cassava bagasse cellulose nanofibrils in the thermoplastic starch matrices has resulted in a decrease of its hydrophilic character especially for glycerol plasticized sample.

Synthesis and characterization of short Grewia optiva fiber‐based polymer composites

AbstractNatural fibers, such as Flax, Sisal, Hibiscus Sabdariffa, and Grewia optiva (GO) possess good reinforcing capability when properly compounded with polymers. These fibers are relatively inexpensive, easily available from renewable resources, and possess favorable values of specific strength and specific modulus. The mechanical performance of natural fiber‐reinforced polymers (FRPs) is often limited owing to a weak fiber‐ matrix interface. In contrast, urea–formaldehyde (UF) resins are well known to have a strong adhesion to most cellulose‐containing materials. This article deals with the synthesis of short G. optiva fiber‐reinforced UF polymer matrix‐based composites. G. optiva fiber‐reinforced UF composites processed by compression molding have been studied by evaluating their mechanical, physical, and chemical properties. This work reveals that mechanical properties such as: tensile strength, compressive strength, flexural strength, and wear resistance of the UF matrix increase up to 30% fiber loading and then decreases for higher loading when fibers are incorporated into the polymer matrix. Morphological and thermal studies of the matrix, fiber, and short FRP composites have also been carried out. The swelling, moisture absorbance, chemical resistance, and water uptake behavior of these composites have also been carried out at different intervals. The results obtained lay emphasis on the utilization of these fibers, as potential reinforcing materials in bio‐based polymer composites. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

Physical, Chemical and Mechanical Properties of Hibiscus sabdariffa Fiber/Polymer Composite

Tensile, compressive, flexural and wear resistance properties of Hibiscus sabdariffa fiber-reinforced phenolic (Resorcinol Formaldehyde) resin matrix-based composites were evaluated to assess the possibility of using these fibers as a new eco-friendly material in engineering applications. Polymer composite samples were fabricated by a compression-molding technique developed in our laboratory. The effect of fiber dimension on mechanical properties was evaluated. The interfacial bonding between Hibiscus sabdariffa fiber and the polymer matrix has been found to affect the mechanical properties of the resorcinol formaldehyde resin matrix. It has been observed that particle-reinforced polymer composites exhibit better mechanical properties as compared to short and long fiber-reinforced polymeric composites. These composites were further subjected to an evaluation of morphological, thermal, physical (swelling and moisture absorption) and chemical properties.

Mechanical, Morphological and Thermal Properties of Pine Needle-Reinforced Polymer Composites

In the present communication, the synthesis and characterization of pine needle (PN)-reinforced urea formaldehyde (UF) polymer matrix-based composites are being reported. These composites were prepared by compression molding technique. The composites were subjected to evaluation of mechanical properties such as tensile strength, compressive strength, flexural strength, and wear resistance. These composites have been found to possess better mechanical properties than the UF polymer matrix. These properties were found to depend on the different loadings of the pine needle, and to increase until 30% loading of pine needle. Beyond this loading the mechanical properties decrease. Morphological and thermal analysis of the UF matrix, fiber, and fiber-reinforced polymer composites have also been carried out.

Use of Flax-g-poly(MMA) as Reinforcing Material for Enhancement of Properties of Phenol Formaldehyde Composites

The present article deals with synthesis of phenol-formaldehyde (PF) matrix-based composites using raw flax and flax graft copolymers as reinforcing agents. Prior to use of the graft copolymer as reinforcing material, its strength vis-à-vis that of raw flax was studied. Composites thus prepared were subjected to the evaluation of different mechanical properties such as wear test, tensile strength, and compressive strength. It has been observed that the composites reinforced with raw flax were more wear-resistant than the graft copolymer-reinforced composites. In the case of tensile strength, composites reinforced with grafted flax showed more extension, but required higher force (175 N) at break-point than composites reinforced with raw flax, which failed at 150 N. Phenol-formaldehyde composite with grafted fiber reinforcement was found to show more compressive strength (800 N) than flax reinforcement. Moreover, the water-repellency property of the fiber could be improved on grafting with methyl methacrylate (MMA), whereas the raw flax was found to be more vulnerable to moisture.

Revisiting the generalized self-consistent scheme in composites: Clarification of some aspects and a new formulation

The determination of an effective property in composite materials necessitates the knowledge of some averaged field quantities in the constituents (like the average heat intensity or average strain) of a composite sample, which is subjected to homogeneous boundary conditions. In the generalized self-consistent scheme (GSCS) which is today a classical micromechanics model suited for the determination of the effective properties of matrix-based composites, those average quantities are estimated by using an auxiliary configuration in which a particulate phase is first surrounded by some matrix material and then embedded in the effective medium. In the present study, we revisit the GSCS both for two- and multi-phase matrix-based composites containing spherical particles, and clarify aspects related to the volume fractions of the particle core and matrix shell within the composite element which is embedded in the effective medium. The contribution of this study is believed to be mainly on the conceptual side and resides in a new formulation of the method in which the embedding volume fractions are determined in the course of the analysis by means of some fundamental relations on the averaged fields. The study is carried out in thermal conduction and elasticity and contains new results on the effective shear modulus of multi-phase composites.

Abrasive wear properties of tool steel matrix composites in rubber wheel abrasion test and laboratory cone crusher experiments

Abrasive wear is the most common type of wear phenomenon in mineral crushing industry. Tool steel matrix-based composites are an attractive choice to combat wear in those conditions because of their excellent abrasion resistance. One purpose of this study is to evaluate the abrasion resistance of such composites having different microstructures. Another purpose is to find out whether the simple dry sand rubber wheel abrasion test (ASTM G 65-91), which is a commonly used and relatively cheap and easy-to-perform test, could be used to rank materials for rock crushing although abrasive wear is not the only type of wear in the real rock crushing conditions. For this purpose Nordberg laboratory cone crusher test was used. Seven different composites were studied. The tool steel of type Ralloy ®WR6 was used as a matrix material in all composites. The reinforcement was either cemented carbide (WC–Co), cast tungsten carbide (WC) or titanium carbide (TiC). The composites were manufactured by hot isostatic pressing (HIP). Abrasive wear properties of all the studied composites are very good. The reinforcement type, size, properties, volume fraction and reinforcement distribution in the matrix all influenced the wear results in both of the tests, but in a different way. Best wear resistance in cone crusher conditions was obtained with cemented carbide (WC–10Co) reinforced Ralloy ®WR6 and in dry sand abrasion with WC reinforced Ralloy ®WR6. No simple correlations between the dry sand rubber wheel abrasion test results and the cone crusher test results were found. This can be attributed to the different wear mechanics and consequently wear mechanisms in the two tests. In the dry sand rubber wheel abrasion test abrasion and detachment of the reinforcements are the major wear mechanisms while in the cone crusher abrasion with rock sliding and pure indentation are the major wear mechanisms. The differences in wear mechanisms result from differences in abrasives (type, size and hardness) and other wear conditions. It is concluded that dry sand rubber wheel abrasion test should not be used for screening materials for rock crushing applications as far as metal matrix composites are concerned.

Transport properties of composites consisting of periodic arrays of exponentially graded cylinders with cylindrically orthotropic materials

The work is concerned with the determination of effective conductivities and field potentials of matrix-based composites consisting of periodic arrays of cylinders which are cylindrically orthotropic and exponentially graded along the radial direction. We generalize Rayleigh’s method to account for the periodic arrangements of these cylinders. The potential field and effective conductivities of composite systems were calculated to a very high order to achieve a sufficient accuracy. We find that the cylindrical orthotropy of the inclusions has a dramatic effect on the potential field of the inclusions. In addition, we discuss the effect of the grading factor on the effective conductivity. Interestingly, we find that when the inclusions are purely cylindrically orthotropic, their effects can be fully described by homogeneous isotropic cylinders. This equivalent isotropic conductivity is simply the geometric mean of the radial and tangential conductivities of cylindrically orthotropic cylinders.

Analysis of microstructural fields in heterogeneous piezoelectric solids

A theory is developed to analyze the internal fields in heterogeneous piezoelectric solids. It is used to derive expressions for mean values and variations of the internal fields due to external loading and eigenfields. The general theory is applicable to both polycrystalline ceramics as well as matrix-based composites. After the general development, the theory is applied to multiphase matrix-based piezoelectric composites, and explicit relations are obtained for two-phase composites. Exact connections are established between the effective thermal properties and the effective electroelastic moduli, and these agree with previous results of Benveniste [3] and Dunn [15] obtained by two different approaches. The stored enthalpy of the heterogeneous solid is also expressed as an explicit function of the effective thermoelectroelastic properties. Finally, to demonstrate the applicability of the theory, numerical results for average fields and field variations are presented for a two-phase composite consisting of continuous piezoelectric fibers embedded in a polymer matrix.

Effect of the matrix ageing conditions on the low strain rate response of a B4C particle reinforced 6061 aluminium matrix composite

Ceramic particle reinforced aluminium matrix-based composites have been studied extensively because of their technologically interesting properties. These include an enhancement in the strength, stiffness, wear resistance, and creep resistance, over unreinforced aluminium alloys. Ceramic particle reinforced aluminium composites have densities comparable to the aluminium alloys from which they are derived and hence are being pursued for use in a variety of engineering applications. The two most commonly used reinforcements for aluminium alloys are SiC and A1203. A number of studies have documented that improvements in the properties of the alloys can be achieved by incorporating relatively small volume fractions (1025 vol %) of SiC or A1203 into the aluminium alloys. Very few studies have been done on the use of BgC particles as reinforcements for conventional aluminium alloys. Boron carbide is an interesting candidate reinforcement material, and possesses physical and mechanical properties that are comparable with or better than those of SiC or A1203. A recent study [1] compared and contrasted the mechanical behaviour of a B4C particle reinforced 6061 aluminium matrix composite with that of a SiC particle reinforced 6061 aluminium matrix composite. Both composites studied were manufactured under identical conditions and incorporated identical volume fractions of the reinforcing particles. The compression strength of the B4C/6061 composite was significantly better than the strength of the SiC/ 6061 composite tested under identical conditions. It was also found that the tensile strength of the B4C particle composite was superior to that of the SiC particle composite. Scanning and transmission electron microscopy studies on these composites revealed that particle/ matrix debonding and particle cracking were the i~rimary reasons for the decreased strength of the SiC particle composites. No evidence of particle/ matrix debonding or particle fracture was found in the B4C/6061 composites. The difference in the interfacial particle/matrix strengths in the two composites was attributed to the differences in the particle/matrix wetting characteristics in the two composite systems [2, 3]. The lower strength of the SiC particles was primarily due to the presence of stacking faults within the ceramic particles themselves [4, 5]. In a previous study [1], matrix contributions to the composite strength were intentionally minimized. This was achieved by testing the unreinforced altoy