Polymer Composite Samples Research Articles

Investigation of the Thermal and Mechanical Properties of Organic Waste Reinforced Polyester Composites

The aim of the research is to investigate the usability of composites produced using the organic waste from hazelnut and corn processing in the Black Sea Region in constructional applications with regard to mechanical and thermal conduction. Polymer composite test samples were produced to which hazelnut shells, corn stalk, nettle stalk (excl. fibres) and nettle fibres had been added in varying (5, 10, 15, 20%) weights to the polyester matrix. Thermal conductivity coefficients were determined in the context of the thermal properties of composite samples. In addition, mechanical properties were determined by compression strength and a three-point bending test. The physical properties of the wastes were determined via XRD, glass transition temperature, one of the thermal features of the composites that is found via DSC and, lastly, the thermal conductivity and specific heat capacity are determined via a heat flow meter. The effect of organic waste amounts and their chemical and physical features on composites’ mechanical and thermal properties are discussed in this study. The results of the study show that nettle stalk-reinforced composites have a low density and more advantageous features than the other composites tested in terms of their thermal conductivities.

Intrinsic cellulosic fiber architecture and their effect on the mechanical properties of hybrid composites

This study is mainly focused on the intrinsic fiber parameters and their influence on the mechanical properties of the hybrid composites. Cellulosic fibers are extracted from mesocarp of Cocos nucifera fruit and outer mat of Luffa cylindrica fruit. The inherent fiber parameters such as fiber diameter, lumen diameter, cell wall thickness are observed under light microscope. Micro-fibrillar angle is found using X-ray diffraction technique. Three varieties of hybrid polymer composite samples are fabricated using Cocos nucifera and Luffa cylindrica fibers as reinforcements in the ratio 2:1, 1:1 and 1:2 respectively employing hand layup technique with their combined weight maintained as 30%. Significant response in the Load Vs Deflection curve and mechanical properties of the hybrid composites are found attributing to the difference in the respective weight proportion of the constituent fibers in the hybrid composite system. Results exemplify that the hybrid composite sample comprising Cocos nucifera and Luffa cylindrica fibers in the ratio 1:2 capitulates the maximum flexural strength and impact strength of 31.05 MPa and 14.24 kJ/m2 respectively when compared with other hybrid composites. The reason for the difference in mechanical strength of hybrid composite samples containing two different fibers is found to be related to the built-in architecture and physical characteristics of the constituent fibers. The morphology of the fractured samples are examined and reported. It is concluded that properties of hybrid composites can be tailor made depending upon the requirements either by using the Cocos nucifera fibers to impart ductility or Luffa cylindrica fibers to impart brittleness.

Gamma-ray attenuation behaviors of hematite doped polymer composites

The studies for protection from gamma radiation have gained speed in recent years. Researchers are in search of a new material without toxic effects such as lead (Pb) and its derivatives. In this study, the polymer composites having different ratios of hematite (25, 50, 75 and 100%) were prepared. To determine the gamma radiation attenuation characteristics of the prepared composites, some gamma-ray radiation attenuation parameters such as transmission factor, mass and linear attenuation coefficients, half and tenth value layers, mean free path, effective atomic number and electron density, energy absorption build-up factor and exposure build-up factor were obtained. The experimental measurements were performed using an HPGe detector and eight different radioactive sources. The photon energies emitted from these sources range from 59.5 keV to 1408.0 keV. The obtained experimental results were compared with the theoretical ones and small differences were observed among them within the limits of experimental uncertainty. It was observed that the mass attenuation coefficients of prepared composites doped with 25%, 50%, 75% and 100% hematite in the range of 59.5–1408.0 keV photon energy were changed between 0.3301–0.0551, 0.4254–0.0545, 0.4943–0.0540 and 0.5461–0.0537 cm2 g−1, respectively. It was reported that the hematite (100%) polymer composite sample is a better gamma radiation shielding material than other prepared composites.

Rapid Infrared Spectroscopic Nanoimaging with nano-FTIR Holography

Scattering-type scanning near-field optical microscopy (s-SNOM), and its derivate, Fourier transform infrared nanospectroscopy (nano-FTIR) are emerging techniques for infrared (IR) nanoimaging and spectroscopy with applications in diverse fields ranging from nanophotonics, chemical imaging and materials science. However, spectroscopic nanoimaging is still challenged by the limited acquisition rate of current nano-FTIR technology. Here we combine s-SNOM, nano-FTIR and synthetic optical holographic (SOH) to achieve infrared spectroscopic nanoimaging at unprecedented speed (8 spectroscopically resolved images in 20 min), which we demonstrate with a polymer composite sample. Beyond being fast, our method promises to enable nanoimaging in the long IR spectral range, which is covered by IR supercontinuum and synchrotron sources, but not by current quantum cascade laser technology.

Estimating Stress Concentration near Grips by the Tension of Polymer Composite Samples

This work aims at the problem of justification of the tensile strength test of flat glass- and carbon-fiber-reinforced plastic samples. Any technique of sample holding causes a concentration of stress and influences negatively on the strength; quantitative estimates of this effect are presented in this work. Based on a simplified equation of shear analysis, the stress distributions in the samples were calculated by different ways of simulation of the diagram of shear stresses applied from the grip side. The advantage of the analytical solution consists in the fact that a clear description of the influence on strength of the following factors is possible, namely, the lengths of the grips and the working part and, particularly, the sample thickness. A similar scale effect is often explained in terms of statistical strength theory, but the analysis shows that the decrease in strength observed with an increase in the sample thickness can be explained by the effect of nonuniformity of the stress field near the grips. The appearance of this edge effect like a Saint-Venant effect is especially pronounced in polymer composites with a low ratio (as compared with metals) of the interlaminar shear modulus to the longitudinal Young’s modulus.

AC conductivity and dielectric behaviour of NaNbO3 ceramic polymer composites

The sodium niobate (NN) polymer composites of different compositions were prepared using solution casting method. The prepared polymer composite film samples were characterized by XRD to study the microstructure of the composites. The SEM studies on composite films revealed a better dispersion of ceramic crystallites in the host matrix. The dielectric constant (∊r) and the ac conductivity of the composites with different concentrations at various frequencies (100 Hz–5 MHz) were investigated. The results showed an increment of dielectric constant of NN-PVA (polyvinyl alcohol) composites with ceramic concentration and ac conductivity of the sodium niobate composites increased with increasing frequency. The complex impedance of the composites were also calculated to understand the dielectric behaviour of the composites.

Mechanical property of polymer composites reinforced with nanomaterials

Polymer composite samples were prepared consisting of NC-826 epoxy and approximately 0.1–0.5 wt% aerographite nanomaterial. The compression properties of the various samples were evaluated at strain rates of 10−3–10−1 s−1 using a universal testing machine. The fracture surfaces of the tested samples were examined by scanning electron microscope. Additional composite samples consisting of NC-826 epoxy and 0.3 wt% multiwalled carbon nanotubes (MWCNTs) were prepared and tested under the same compression strain rates of approximately 10−1–10−3 s−1. In general, the results showed that the addition of aerographite nanomaterials to the resin matrix is beneficial in suppressing crack propagation under compression loads and therefore leads to an improved stress, toughness, and fracture strain compared to the pure resin sample. The results additionally showed that the use of MWCNTs as a reinforcement material yields a further small improvement in the mechanical properties of the sample.

Flash method experiment design for the thermal characterization of orthotropic materials

In this paper an experiment design of the flash method dedicated to orthotropic material thermal characterization is considered. The present study relies on a comparative evaluation of the laser excitation duration time and intensity level, with respect to the measurement face, and their effects on the estimation accuracy of orthotropic material thermal diffusivities. The present estimation method, based on the well-known flash method concept, allows the simultaneous estimation of the three main thermal diffusivities. The identification method relies on the resolution of an inverse problem by means of a stochastic optimization algorithm retrieving the thermal properties by minimization of the least-squares criterion between the outputs of an analytical model and numerical predictions or experimental measurements. Both the direct analytical model and the estimation strategy are validated using an experimental test bench conducted on a carbon fiber reinforced polymer composite sample. The evaluation of various experiment designs, corresponding to different combinations of laser spot intensity and duration time, is conducted according to the face of the observation. A sensitivity analysis is conducted to complete the search of the optimal configuration. The present numerical study has enabled us to identify the rear face to be the most effective in order to successfully estimate the thermal diffusivities of such materials, especially the in-depth thermal diffusivity. For this configuration, excitation with a relatively long duration time (about 10 s in the present relatively low-diffusivity-material case), has been proved to be more convenient for such identification problems, compared to the impulse or very short pulse types.

Lead(II) chloride effects on nuclear shielding capabilities of polymer composites

This study investigated the radiation shielding capacity of undoped polymer composite and lead (II) chloride (PbCl2)-containing polymer composite samples. The PbCl2 and polyester resin were used as filler and base materials, respectively. The PbCl2 was added to the polyester resin from 5 wt% to 20 wt%, and so an undoped polymer composite and four polymer composite samples each with different PbCl2/polymer resin ratios were investigated for their radiation attenuation capacity. Experimental data of the samples were taken using an HPGe detector, and 241Am, 133Ba, 57Co, 22Na, 137Cs, 152Eu, 54Mn and 60Co radioactive point sources were used with energies in the range of 59.5–1408.0 keV. The experimental data were compared with both those simulated with FLUKA code and those theoretically calculated in WinXCOM. Mass attenuation coefficients used in estimating the shielding capacity of the samples were in good agreement with those found using FLUKA and WinXCOM. Radiation protection efficiency was improved by 244% especially at 59.5 keV energy by using PbCl2(20%) polymer composite compared to undoped polymer composite. The sample with the maximum weight percentage of PbCl2, PbCl2(20%), had the highest attenuation coefficients and lowest absorption thicknesses, and had the best radiation shielding property compared to the other polymer composite samples.

РОЗРОБКА АНТИСТАТИЧНИХ І НАПІВПРОВІДНИКОВИХ КОМПОЗИЦІЙ ПОЛІЕТИЛЕН/ПОЛІАНІЛІН ТА ПОЛІВІНІЛХЛОРИД/ПОЛІАНІЛІН

The effect of the polyaniline content on the mechanical, rheological and electrical properties of polyethylene and polyvinylchloride compositions for the production of antistatic and semiconductive materials was established. Samples of polymer composites were obtained in two stages: 1) mixing of components in a mixer type "disk in disk"; 2) pressing into films by the method of "hot pressing." Tensile strength, relative elongation, melt flow index and specific volume electrical resistance of the compositions were investigated by standard methods. It was found that an increase in the volume content of polyaniline in the polyethylene and polyvinylchloride matrix leads to a monotonic decrease in the melt flow index, as well as tensile strength and relative elongation. At the same time, there is a significant decrease in the specific volume electrical resistance in polyethylene and polyvinylchloride composite films, which contain up to 30% vol. of polyaniline. The reduction of the tensile strength and the relative elongation of films from compositions containing up to 30% vol. of polyaniline. This is due to the decrease in the viscosity of the melt-filled compositions, as evidenced by the decrease in the flow index of the melt polyethylene compositions from 3 to 2 g / 10 min, and polyvinylchloride – from 13 to 3 g / 10 min. Specific volume electrical resistance naturally decreases with increasing volume concentration of the filler in ranges from 1014 to 102 Ohm ∙ m for polyethylene compositions and from 1010 to 101 Ohm ∙ m for polyvinylchloride compositions. The developed polyethylene and polyvinylchloride compositions filled with polyaniline can be used for the production of polymer products with antistatic and semiconductive properties.

A review on the mechanical properties for thin film and block structure characterised by using nanoscratch test

AbstractThe nanoscratch test has been identified as one of the important tools for evaluating the mechanical and tribological properties of materials. This paper reviews the current researches on the nanoscratch test using to characterise the mechanical properties of three typical materials, including thin film, polymer composite and concrete, from the perspectives of the Berkovich indenter, parameter selection, mode selection, and analysis of resulting data. In addition, to provide a deep understanding on the test from different magnitude, a comparison between the microscratch test and nanoscratch test on the evaluation of tribological performance is also provided in this paper. The characterisation by nanoscratch test of two structural samples, in terms of layered film structures (thin film and coating sample) and single layer block structure (polymer composite sample and concrete samples) are also described in this paper, which aims to provides a deep understand on the evaluation the adhesion, tribological and interfacial properties of the typical materials samples by nanoscratch test. Finally, the coefficient of friction and critical load are discussed, which are two important parameters in tribological properties and adhesion properties.

Shape Memory Polymer Composites for Long-Term Exposure to Space Environment

Shape memory polymer composite (SMPC) samples for long-term exposure in Space environment have been designed and tested. SMPC laminates consisted of two carbon fiber reinforced (CFR) plies and a SMP interlayer. Samples were manufactured by prepreg lamination and molding with subsequent thermomechanical processing for shape change. Commercial raw materials were selected both for CFR plies and SMP interlayer. Differential scanning calorimetry and dynamic mechanical analysis have been used to evaluate the thermo-mechanical behavior of the SMPC laminate in comparison with the neat CFR laminate and the SM epoxy resin of the interlayer. Results show that the hybrid nature of the SMPC laminate is responsible for their good shape memory behavior. A small disk with a simple shape change has been prepared to be integrated in the MISSE-FF platform for long-term exposure to Space environment. Recovery tests under IR light exposure highlighted the optimal functional behavior of this kind of sample. Copyright © VBRI Press.

Microstructure and Properties of Polymer Composites

This work aimed to characterise microstructure and mechanical properties of polymer composite samples. The main task was to adapt the well-known techniques of metallography (i.e. sample preparation and microscopic examination) to documentation of multi-component polymer materials and to optimize the methods of light and electron microscopy for this particular purpose. There were several issues (e.g. low melting point, absence of electrical conductivity), which made the process different from metal samples preparation and observation and which needed to be addressed. Various mounting resins were tested for the samples to find the suitable one, then the process of grinding and polishing was optimized and finally the microstructure was documented using light and scanning electron microscopy (SEM). Samples in the undeformed state were examined as well as the samples subjected to tensile test at different temperatures. Prior to the microscopic observations the material was analysed using methods of thermal analysis (TG A, DSC) and infrared spectroscopy (FT-IR). The tensile tests were employed not only to determine the mechanical properties but also to obtain deformed samples for further microscopic observation.

Investigating the mechanical and insulation performance of waste eggshell powder/epoxy polymer for power insulation application

In an effort towards the optimization of materials for industrial application, composite technology has been identified to provide an effective way to improve the performance of insulating materials used in power system applications. Clay and synthesized metal oxide micro- and nanoparticles have been used as fillers in host polymer materials. In this study, the focus is on the development of composite polymeric insulation using particles from animal shell waste for use in electrical and electronic power systems. Epoxy composite samples were prepared with waste chicken eggshell powder and titanium oxide (TiO2) nanoparticles, respectively. Mechanical (tensile strength) and dielectric properties were studied, and high-voltage AC was used to evaluate the variation in electrical conductance with percentage composition of the filler particles in the epoxy polymer matrix. This was done by monitoring the leakage current through the epoxy polymer composites under high-voltage stresses in the range of 0.5–5 kV. The two polymer composites’ type has comparable loss tangent, but the eggshell powder-filled polymer samples displayed higher dielectric constant and lower electrical conductance at high voltage compared with the TiO2 nanoparticle-filled polymer composite samples. While the minimum conductance of 2.68 × 10−9 S was obtained from the epoxy composite sample with 3 wt% eggshell particle loading, epoxy nanocomposite displayed a minimum conductance of 4.06 × 10−9 S with 2 wt% titanium oxide loading. This is an indication that polymer composite with the eggshell particles may produce polymeric insulation that could be more resistant to leakage current.

Effect of CuI concentration on structural and optical properties of PVA: CuI nanocomposites

The nanocomposite on the base of synthesis Copper iodidenanoparticles and polyvinyl alcohol (PVA/CuI) with differentconcentration of CuI were obtained using casting technique.PVA/CuI polymer composite samples have been prepared andsubjected to characterizations using FTIR spectroscopy, The FTIRspectral analysis shows remarkable variation of the absorption peakpositions with increasing CuI concentration. The obtained results byX-ray diffraction indicated the formation of cubic CuI particles. Theeffects of CuI concentrations on the optical properties of the PVAfilms were studied in the region of wavelength, (190-1100) nm.From the derivation of Tauc's relation it was found that the directallowed transitions was more probable in PVA/ CuI nanocomposite.The results indicate that the obtained values of optical absorptionedge, and energies band gap decreases from 4.05 to3.89 eV for directtransitions with the increasing salt contents.

Experimental studies of 3D woven composites interweaving types effect on the mechanical properties of a polymer composite material

The work is related to a various types experimental studies complex of 3D woven polymer composite materials samples based on preforms. In the work material mechanical properties was obtained and evaluation effect of various interlacing schemes on mechanical characteristics was conducted.

Phenomenological characteristics structural features research obtained at fibrous plastics standard tests

The work is aimed at developing fundamental experimental knowledge about the behavior of polymer composite materials samples (structural elements) during the implementation of non-trivial test methods and modeling. As part of the study an analysis of standard and approved testing methods for samples of composite materials was carried out.

Terahertz time-domain spectroscopy as a novel metrology tool for liquid-phase exfoliated few-layer graphene

Few-layer graphene (FLG) platelets exfoliated directly from graphite are finding a wide range of potential applications, including composites and printed electronics. However, characterisation of the FLG material following incorporation into polymers, including the quality of the dispersion, remains a challenge. Here, we present the use of terahertz time-domain spectroscopy as a potential solution to this challenge which could form the basis of a rapid characterisation tool. The THz refractive index was found to be highly sensitive to the loading of FLG, opening the route to mapping local FLG concentration within a polymer composite sample. By fitting the measured permittivity of the flakes to the Drude–Smith model of conductivity, we also show that the carrier concentrations of these materials are comparable to un-doped chemical vapour deposition produced materials. The ability to measure electronic properties of FLG following processing is important to ensure that defects have not been introduced or chemical functionalisation removed during processing.

Carbon Nanotube-Based Organic Thermoelectric Materials for Energy Harvesting.

Carbon nanotubes (CNTs) have attracted much attention in developing high-performance, low-cost, flexible thermoelectric (TE) materials because of their great electrical and mechanical properties. Theory predicts that one-dimensional semiconductors have natural advantages in TE fields. During the past few decades, remarkable progress has been achieved in both theory and experiments. What is more important is that CNTs have shown desirable features for either n-type or p-type TE properties through specific strategies. Up to now, CNT‒polymer hybrids have held the record for TE performance in organic materials, which means they can potentially be used in high-performance TE applications and flexible electronic devices. In this review, we intend to focus on the intrinsic TE properties of both n-type and p-type CNTs and effective TE enhanced strategies. Furthermore, the current trends for developing CNT-based and CNT‒polymer-based high TE performance organic materials are discussed, followed by an overview of the relevant electronic structure‒TE property relationship. Finally, models for evaluating the TE properties are provided and a few representative samples of CNT‒polymer composites with high TE performance are highlighted.

Fabrication of Fiber Reinforced Plastics by Ultrasonic Welding

Ultrasonic fabrication of fiber reinforced plastics made from thermoplastic polymer films and carbon or glass fibers enables cycle times of a few seconds and requires investment costs of only some 10,000 €. Besides this, the raw materials can be stored at room temperature. A fiber content of 33 vol % and a tensile strength of approximately 1.2 GPa have been achieved by ultrasonic welding of nine layers of foils from polyamide, each 100 µm in thickness, and eight layers of carbon fibers, each 100 µm in thickness, in between. Besides unidirectional carbon fiber reinforced polymer composite (CFRP) samples, multi-directional CFRP plates, 116 mm, 64 mm and 1.2 mm in length, width and thickness respectively, were fabricated by processing three layers of carbon fiber canvas, each 300 µm in thickness, and eight layers of polyamide foils, each 100 µm in thickness. Furthermore, both the discontinuous and the continuous ultrasonic fabrication processes are described and the results are presented in this paper. Large-scale production still needs to be demonstrated.