Elastic Modulus Of Nanocomposites Research Articles

Determination of mechanical properties of nanocomposites reinforced with spherical silica nanoparticles using experiments, micromechanical model and finite elements method

In this research, experimental, numerical, and micromechanical methods are used to determine the effects of silica nanoparticle content on the elastic modulus of polymer matrix nanocomposites in tension and compression. The direct mixing method was used to prepare experimental samples containing 0.1, 0.25, and 0.5 volume fractions of silica nanoparticles. The elastic modulus of the nanocomposites is evaluated by the Einstein, Guth, Mori-Tanaka, Halpin-Tsai, Kerner, and Ji et al. micromechanical models. In addition, the elastic modulus of the nanocomposites is evaluated using the RVE method in ABAQUS software. The effects of volume fraction and diameter of silica nanoparticles, thickness, and adhesion exponent of the interphase on the elastic modulus of polymeric nanocomposite are extensively examined. Stiffer elastic modulus behavior is found in the presence of interphase region. The results indicate that the elastic modulus of nanocomposites reinforced with spherical silica nanoparticles is improved with increasing nanoparticle volume fraction, decreasing the nanoparticle diameter, increasing the interphase thickness, and decreasing the interphase adhesion exponent. The validity of the results of numerical and micromechanical models has been checked with experimental results. It can be seen that the results obtained from the experiments with 1 hour of ultrasonic waves in the tensile samples with volume fractions of 0.1, 0.25, and 0.5, compared to the pure sample, have increased by 5.4, 10.3, and 9.7 percent, respectively. Similarly, for compression samples with the same volume fractions, the results have increased by 7, 13, and 11 percent, respectively.

Effects of stone–wales defects of carbon nanotubes on the elastic properties of the carbon nanotube-polyethylene nanocomposite and its interface

Carbon nanotube (CNT) filling in a polymer is an advanced approach to improve and manage the mechanical behaviors of polymer-matrix nanocomposites. However, some structural defects exist in CNTs, e.g., Stone–Wales (SW) defects on single-walled carbon nanotubes (SWCNT), which reduces the strength and changes the mechanical properties of CNT-reinforced nanocomposites. The influences of CNTs’ SW defects on the Young’ modulus of the CNT-polyethylene (PE) composite and its interface were investigated. All studies were performed through molecular dynamics (MD) simulations with the consistent force field (PCFF) on the platform of a large-scale atomic/molecular massively parallel simulator (LAMMPS). In the MD model of the CNT-PE nanocomposite, CNTs contained SW defects. The elastic modulus of the nanocomposite was obtained from its stress-strain relation, and that of the CNT-PE interface varied with strain according to the interfacial interaction energy. The correctness and rationality of the work were verified by comparing the results from references, experiments, and the rule of mixtures (ROM). The results showed that SW defects of CNTs reduced the mechanical strength no matter for the interface and integral nanocomposite. Specifically, with increased SW defect concentration (defined as the ratio of atoms in the SW defect region to total atoms of a CNT), the interfacial strength significantly weakened, and the elastic modulus of the integral nanocomposite reduced on the macro level. These results are beneficial to understanding the mechanical properties of CNT-PE composites and the design of related products.

Thermal buckling analysis of porous functionally graded nanocomposite beams reinforced by graphene platelets using Generalized differential quadrature method

In this paper, thermal buckling of functionally graded (FG) porous nanocomposite beams subjected to a thermal gradient are studied by generalized differential quadrature method (GDQM). We consider three different types of nanofillers dispersion patterns and porosity distributions. Materials parameters vary along the thickness direction. Under Gaussian random field (GRF) scheme, the mechanical properties of closed- cell cellular solids are used. Thereby, the variation of Poisson's ratio as well as the relationship between porosity coefficient and mass density are determined. The elastic modulus of nanocomposite is obtained by applying Halpin-Tsai micromechanics model. In the course of this work, the accuracy and efficiency of the (GDQM) are validated. We studied the effects of weight fraction, dispersion pattern, geometry, and size of graphene platelets (GPLs), as well as porosity distribution, porosity coefficient, slenderness ratio and metal matrix on the thermal buckling of the nanocomposite beam. Our findings, contrary to what was expected, are somewhat surprising. According to our results, the graphene platelets (GPLs') performance is affected strongly by their geometry.

Physical properties and safety of 100% post-consumer PET bottle -organoclay nanocomposites towards a circular economy

Polyethylene terephthalate from bottle waste (RPET) was compounded with an organically modified nanoclay at increasing concentrations by extrusion to improve its physical-mechanical properties. Nanocomposites evidenced combined intercalated/tactoid structures by XRD and TEM. The higher tactoid proportion increased the color variation and the opacity of the films but did not affect the transparency. Although clay addition did not affect the thermal properties of PET samples, crystallinity and the barrier effect against volatile release increased with clay concentration. The elastic modulus of nanocomposites was higher than control RPET film. Mechanical parameters of RPET film with 5 wt% of organoclay were similar to those obtained from virgin polymer (PET). Global migration and metal traces migration from nanocomposite films to food simulants were below current European Union legislation.

Prediction of mechanical properties of quaternary nanocomposites based on polypropylene using fuzzy logic

The goal of the present study is to investigate and predict the mechanical properties, including impact strength, elastic modulus, and elongation-at-break of quaternary nanocomposites based on polypropylene (PP)/ethylene–propylene–diene monomer (EPDM)/glass fiber (GL)/graphene nanosheets (GPn) by fuzzy logic. Three parameters in different levels, including EPDM, GL, and GPn, were chosen for combination with a PP matrix. The fuzzy logic surfaces showed that the EPDM rubber and GPn had the main role in the elastic modulus of nanocomposites. The high levels of EPDM content resulted in a considerable increase in impact strength and, generally, the presence of EPDM had no effect on elongation-at-break.

On the constant parameters of Halpin-Tsai equation

The Halpin-Tsai method is a well-known technique to calculate the stiffness of composites reinforced by micro and nano particles. In this method, first the longitudinal and transverse moduli of composites are calculated. Then, the elastic modulus of randomly oriented composites is obtained using an equation contains a constant coefficient. This coefficient is assumed to be constant and independent of the matrix and reinforcement properties. The aim of the present research is to calculate this coefficient with an analytical model and show that it depends on the matrix and reinforcement properties. In this regard, an analytical method called the Mori-Tanaka laminated analogy (MT-LA) was developed which is able to calculate the elastic modulus of the randomly-oriented composites. Comparing the result of the MT-LA method with that of the Halpin-Tsai equation, the coefficient of Halpin-Tsai equation was obtained. It was shown that this coefficient is not constant and depends on the volume fraction and the stiffness ratio of the matrix to reinforcement. Finally, using this new coefficient, equations are presented which are able to compute the elastic modulus of both platelet and fibrous randomly oriented composites. Using the mechanical properties of the carbon nanotube (CNT), graphene sheet (GS) and the polymer, the elastic moduli of nanocomposites were calculated. The results were compared with experimental data available in the literature. It was shown that more accurate results were achieved by using this new coefficient in the Halpin-Tsai equation.

Effects of quaternary ammonium chain length on the antibacterial and remineralizing effects of a calcium phosphate nanocomposite.

Composites containing nanoparticles of amorphous calcium phosphate (NACP) remineralize tooth lesions and inhibit caries. A recent study synthesized quaternary ammonium methacrylates (QAMs) with chain lengths (CLs) of 3–18 and determined their effects on a bonding agent. This study aimed to incorporate these QAMs into NACP nanocomposites for the first time to simultaneously endow the material with antibacterial and remineralizing capabilities and to investigate the effects of the CL on the mechanical and biofilm properties. Five QAMs were synthesized: DMAPM (CL3), DMAHM (CL6), DMADDM (CL12), DMAHDM (CL16), and DMAODM (CL18). Each QAM was incorporated into a composite containing 20% NACP and 50% glass fillers. A dental plaque microcosm biofilm model was used to evaluate the antibacterial activity. The flexural strength and elastic modulus of nanocomposites with QAMs matched those of a commercial control composite (n = 6; P > 0.1). Increasing the CL from 3 to 16 greatly enhanced the antibacterial activity of the NACP nanocomposite (P < 0.05); further increasing the CL to 18 decreased the antibacterial potency. The NACP nanocomposite with a CL of 16 exhibited biofilm metabolic activity and acid production that were 10-fold lesser than those of the control composite. The NACP nanocomposite with a CL of 16 produced 2-log decreases in the colony-forming units (CFU) of total microorganisms, total streptococci, and mutans streptococci. In conclusion, QAMs with CLs of 3–18 were synthesized and incorporated into an NACP nanocomposite for the first time to simultaneously endow the material with antibacterial and remineralization capabilities. Increasing the CL reduced the metabolic activity and acid production of biofilms and caused a 2-log decrease in CFU without compromising the mechanical properties. Nanocomposites exhibiting strong anti-biofilm activity, remineralization effects, and mechanical properties are promising materials for tooth restorations that inhibit caries.

Glass transition temperature and elastic modulusof nanocomposites based on polyimides

Today great attention is paid to production and research of the mechanical and termal properties of nanocomposites based on polyimides. These polymers are heatresisting and possess the increased mechanical properties in wide range of temperatures. Various nanoparticles are introduced into polyimides: graphite nanotubes and flatparticles, the particles of SiO , the surface of which is modified, the particles of ZrOandmontmorillonite, etc.The authors analyzed the influence of nanoparticles on the glass transition temper-ature T and elastic modulus E of the polyimides based on 1,3-bis-(3,3’,4,4’-dicarboxy-phenoxy)benzene and 4,4’-bis-(4-aminophenoxy)biphenyl, and pyromellitic dianhydride and oxydianiline. Nanoparticles introduced in small amounts are produced of graphite and ZrO . The suggested ratios take into account the chemical structure of the polymer and nanoparticles, as well as the structure of their surface in case of chemical modification; the concentration of nanoparticles and their form, the number of polar groups on the surface. The number of polar groups and nanoparticles’ concentration have the greatest influence on T . The elastic modulus of nanocomposites depending on nanoparticles’ concentration is connected with van der Waals volume of the repeating unit of polymer and nanoparticle.

Preparation and evaluation of collagen-silk fibroin/hydroxyapatite nanocomposites for bone tissue engineering

A new in situ precipitation technique was developed to synthesize collagen-silk fibroin/hydroxyapatite nanocomposites. The componential properties and morphological of nanocomposites were investigated. It was revealed that the inorganic phase in the nanocomposite was carbonate-substituted hydroxyapatite with low crystallinity. Morphology studies showed that hydroxyapatite particles with size ranging from 30 to 100nm were distributed uniformly in the polymer matrix. According to the TEM micrographs, inorganic particles were composed of more fine sub-particles whose diameters were between 2 and 5nm in size without regular crystallographic orientation. The mechanical properties of the composites were evaluated by measuring their elastic modulus. The data indicated that the elastic modulus of nanocomposites was improved by the addition of silk fibroin. Finally, the cell biocompatibility of the composites was tested in vitro, which showed that they have good biocompatibility. These results suggest that the collagen-silk fibroin/hydroxyapatite nanocomposites are promising biomaterials for bone tissue engineering.

Mechanical behavior of solid and foamed polyester/expanded graphite nanocomposites

Poly(ethylene 2,6-naphthalate)- PEN is a thermoplastic polyester characterized by a high glass transition temperature (125°C), comparable to that of polyetheretherketone (143°C), but with a significantly lower melting temperature (265°C). Its physical and chemical properties are very promising for applications in transport industry and aeronautics. Nanocomposite matrices based on PEN and expanded graphite were developed to be used as matrix for foams. Expanded graphite was melt blended with the polymer by means of extrusion process and its effects on the foaming properties were investigated through solid state foaming process. Graphite nanoparticles increased the crystallization kinetics of the polymer, inducing the formation of small crystals but lowering the total amount of crystalline phase. Transmission electron microscopy analysis showed a good dispersion of the nanofiller but some aggregates were still present, as also confirmed by graphite peak in the X-ray diffraction patterns of all nanocomposites. The elastic modulus of nanocomposites with amorphous matrix increased with respect to the neat amorphous PEN, while the modulus of crystallized nanocomposites decreased. Nanocomposite foams were successfully prepared, and an higher cell density was obtained when compared to the neat PEN. In the latter case, a strong increase in both yield and strain at break was measured. Furthermore, the elastic modulus and compressive yield stress of foamed PEN nanocomposites increased with the expanded graphite.

Effect of carbon nanotube orientation on the mechanical properties of nanocomposites

Carbon nanotubes (CNTs) have been regarded as ideal reinforcements of high-performance composites with enormous applications. In this paper, nano-structure is modeled as a linearly elastic composite medium, which consists of a homogeneous matrix having hexagonal representative volume elements (RVEs) and homogeneous cylindrical nanotubes with various inclination angles. Effects of inclined carbon nanotubes on mechanical properties are investigated for nano-composites using 3-D hexagonal representative volume element (RVE) with short and straight CNTs. The CNT is modeled as a continuum hollow cylindrical shape elastic material with different angles. The effect of the inclination of the CNT and its parameters is studied. Numerical equations are used to extract the effective material properties for the hexagonal RVE under axial as well as lateral loading conditions. The computational results indicated that elastic modulus of nano-composite is remarkably dependent on the orientation of the dispersed SWNTs. It is observed that the inclination significantly reduces the effective Young’s modulus of elasticity under an axial stretch. When compared with lateral loading case, effective reinforcement is found better in axial loading case. The effective moduli are very sensitive to the inclination and this sensitivity decreases with the increase of the waviness. In the case of short CNTs, increasing trend is observed up to a specific value of waviness index. It is also found from the simulation results that geometry of RVE does not have much significance on stiffness of nano-structures. The results obtained for straight CNTs are consistent with ERM results for hexagonal RVEs, which validate the proposed model results.

The glass transition and thermoelastic behavior of epoxy-based nanocomposites: A molecular dynamics study

In this study, the glass transition and thermoelastic properties of cross-linked epoxy-based nanocomposites and their filler-size dependency are investigated through molecular dynamics simulations. In order to verify the size effect of nanoparticles, five different unit cells with different-sized silicon carbide (SiC) nanoparticles are considered under the same volume fraction. By considering a wide range of temperatures in isobaric ensemble simulations, the glass transition temperature is obtained from the specific volume–temperature relationship from the cooling-down simulation. In addition, the coefficient of thermal expansion (CTE) and the elastic stiffness of the nanocomposites at each temperature are predicted and compared with one another. As a result, the glass transition and thermoelastic properties of pure epoxy are found to be improved by embedding the SiC nanoparticles. Especially regarding the CTE and elastic moduli of nanocomposites, the particle-size dependency is clearly observed below and above the glass transition temperature.

A study on the prediction of the mechanical properties of nanoparticulate composites using the homogenization method with the effective interface concept

AbstractA sequential multi‐scale homogenization method combined with molecular dynamics (MD) simulation is developed for the mechanical characterization of nanoparticulate composites. In order to characterize the particle‐size effect of nanocomposites, the effective interface, which has been adopted in continuum micromechanics approaches, is considered as the characteristic phase. Owing to the existence of the interface and the size‐dependent elastic modulus that is observed from MD simulations, an analysis of the mechanical properties of nanocomposites with continuum micromechanics requires careful consideration of the particle‐concentration effect. Therefore, this study focuses on hierarchical information transfer from the molecular model to the continuum model through the homogenization method in lieu of an analytical micromechanics bridging method. Using the present multi‐scale homogenization method, the elastic properties of the effective interface are numerically evaluated and compared with the analytically obtained micromechanics solutions. In addition, the overall elastic modulus of nanocomposites is obtained from the present model and compared with the results of MD simulation, the micromechanics bridging model, and finite‐element analysis (FEA). Copyright © 2010 John Wiley &amp; Sons, Ltd.

Role of structure and morphology in the elastic modulus of carbon nanotube composites

The nature of nanoscale reinforcements in the carbon nanotube composites indicates nanocomposite properties are heavily dependent on the micro/nano-structure and morphology. Macroscopic parameter-based properties estimation may lead to deviation as large as 30%. In this paper, a modified shear-lag model, combined with probability statistical theory and composites morphology, is established to investigate the elastic properties of single wall carbon nanotubes (SWNTs)-reinforced polymer composites. The computational results indicated that elastic modulus of nanocomposite was remarkably dependent on the micro/nano-structure, including diameter, length, and orientation of the dispersed SWNTs. Microstructure-dependent shape factor and orientation effect factor played a key role on achieving high-performance nanocomposites. Elastic modulus of nanocomposite with well-dispersed carbon nanotubes was more susceptible to the orientation. Similarly, nanocomposite modulus was more subject to the dispersion influence when SWNTs were well-aligned. The maximal modulus was located in the zone of small rope diameters and small orientation angles when adequate interfacial bonding was provided. The computational results were also compared with experimental outcome and demonstrated good consistence.

Evaluation of elastic modulus of polymer matrix nanocomposites

AbstractA new model to evaluate the elastic modulus of polymer nanocomposites is developed with emphasising on the role of inclusion/matrix interphase. The new model can be applied to polymer nanocomposites reinforced by inclusions with different shapes including spherical, cylindrical, and platelet. After validating the new model using experimental and FEA results, the effects of several parameters such as inclusion shape and modulus, d‐spacing, and matrix properties on the elastic modulus of nanocomposites are investigated. POLYM. COMPOS., 28:405–411, 2007. © 2007 Society of Plastics Engineers