Behavior Of Polymer Composites Research Articles

Accelerated weathering of sustainable and micro-filler Basalt reinforced polymer biocomposites: Physical, mechanical, thermal, wettability, and water absorption studies

This study intends to evaluate and comprehend the accelerated weathering behavior of various thermoset and thermoplastic composites loaded with an eco-friendly basalt micro-filler. Basalt incorporation into various polymer matrices is, in fact, a very innovative idea that might present some very exciting, as yet unexplored, perspectives. The four kinds of thermoset polymers (synthetic epoxy, bio-epoxy, polyester, vinyl ester) were reinforced with constant basalt reinforcement (30 wt %) and fabricated via the casting process. Whereas the three kinds of thermoplastic (polylactic acid, polypropylene, high-density polyethylene) polymers were also loaded with a constant basalt ratio and manufactured through an internal mixing process followed by a compression molding technique. The fabricated samples were employed inside the xenon arc light accelerated weathering equipment under ultraviolet (UV) rays, temperature, and humid conditions for 555.55 h as per ASTM G155-13 cycle 1. There is a significant improvement in the density of polymer composites due to highly dense basalt particle incorporation and maximum void percentage was observed in thermosets due to casting defects than in the thermoplastic samples. After weathering, the tensile, flexural, and impact properties of composites were significantly reduced due to the thermo-oxidative reaction and degradation under UV and moisture exposure. As a result of UV-induced chain scission, small fractures may develop. These spaces provide the ideal environment for moisture to infiltrate into the primary composite structures, weakening the links between the reinforcement and matrix. Scanning electron microscopy was used to analyze the significant changes in the surface morphology of weathered and unweathered tensile fractured samples. The hardness was considerably improved due to the presence of highly stiffen and hard basalt particles. The idea that accelerated weathering destruction creates hydrophobic surface characteristics in most of the composites due to a variety of factors, like physical and chemical transformations, is supported by the increased contact angle value and a decrease in surface free energy, particularly the polar section. The thermogravimetric analysis revealed that there is not much significant impact of weathering on composites, however, variations were observed in the thermomechanical analysis due to compatibility issues. It is observed that the onset and endset degradation temperatures got decreased with the reinforcement of 30 wt% basalts after the internal mixing process. This could be brought on by the molecular weight decreasing while mixing. The behavior of polymer composites in water absorption study is found to be unique depending on their hydrophilicity and defects raised during the fabrication.

Rheological properties of polypropylene composites with calcium carbonate under high shear rates

The rheological properties of isotactic polypropylene (iPP) and its composites with unmodified and stearic acid-modified calcium carbonate (5, 10, 20, 30 wt.%) were investigated. The processability factor K of the composites was determined based on changes in the mass flow rate (MFR). The assessment of rheological properties was carried out at high shear rates, in the injection process, using a special on-line measuring head. Measurements were performed at a temperature of 230°C, in the range of apparent shear rate from 19,100 to 101,900 s-1, based on the Ostwald-de Waele power-law model. It has been shown that the behavior of polymer composites during processing (flow resistance, flow, and viscosity curves, MFR) depends on the degree of filling, the type of filler used and the range of shear rates.

Investigations on interfacial moisture storage and its relation to the mechanical behavior in polymer composites

AbstractMoisture absorption in composites significantly influence the fiber/matrix interface regions and mechanical properties. Hence, it is very important to quantify the moisture storage in interfaces and correlate it to the mechanical behavior. The novelty of this article is that, for the first time, it explores the correlation of moisture absorption parameters with the mechanical behavior of composites. The paper studies four different types of moisture‐soaked composites—glass fiber/epoxy, carbon fiber/epoxy, ZnO nanowire incorporated glass fiber/epoxy, and ZnO nanowire incorporated carbon fiber/epoxy. One‐dimensional hindered diffusion model (1D HDM) was used for the extraction of moisture absorption parameters. The hindrance coefficient (ratio of bound to unbound moisture) of composites was found to increase proportionately with the increase in the volume of interfacial regions. Only in carbon fiber/epoxy composite, it did not increase proportionately due to the relatively larger degradation of interface. This was correlated well with mechanical test responses wherein carbon fiber/epoxy exhibited anomalous failure modes due to relatively larger degradation of interface. Numerical simulations were also carried out to describe the moisture absorption in composites. Numerical simulations of moisture absorption in composites using time‐varying boundary conditions matched very well with experimental as well as 1D HDM results.

Investigation on strain rate sensitivity of 3D printed sPEEK-HAP/rGO composites

Nanofillers can be added to polymers to improve their mechanical behaviour. However, the yield behaviour of most polymer composites is influenced by strain rate. The majority of the research focused on the behaviour of polymer composites at high strain rates. This work aims to investigate how hydroxyapatite (HAP) and reduced Graphene Oxide (rGO) nanofillers affect the mechanical properties of sulphonated polyetheretherketone (sPEEK) at low (tensile and compression behaviour) and high strain rates (compression behaviour). The thermal, mechanical, and toughness responses of sPEEK filled with HAP and varying Mf of rGO (0.5%, 1%, and 1.5%) at different strain are studied in detail. The strong strain rate effect was seen in HAP and rGO loaded sPEEK composites. The strain rate sensitivity factor of sPEEK-HAP/rGO increased with strain rate but reduced with increased rGO concentration. Under low strain rate compression, HAP and rGO loaded sPEEK absorbed approximately 4% more energy at Mf of 1.5% than the neat sPEEK. Higher concentration of rGo (1.5%) withstood better melt processing, and demonstrated excellent integrity inside the sPEEK-HAP matrix. Increased rGO density resulted in lower sPEEK-HAP composite density and better mechanical characteristics, even at low strain rates. MFI decreases as rGo concentration increases, which might resolve printing issues. The increased compatibility between sPEEK-HAP and rGO particles was demonstrated by SEM images.

Mechanical Behavior of Polymer Composites Reinforced with Coir and Date Palm Frond Fibers

This article explains to study the feasibility of natural fiber (date palm frond and coir fibers from Oman) reinforced polymer composite laminates processed using the hand lay method. Untreated and alkali-treated fiber composite laminate specimens of longitudinal and transverse direction fibers were subjected to various mechanical property tests (such as tensile, flexural, compression, shear, and hardness). Results show that the required polymer composite is ecofriendly, has no harm by natural fiber composite, and enhances mechanical strength and low density with specific strength. Hence, it is suitable for industrial and structural applications due to its improved mechanical properties.

Statistical Study of the Influence of Fiber Content, Fiber Length and Critical Length in the Mechanical Behavior of Polymeric Composites Reinforced with Carica Papaya Fibers (CPFs)

Vegetable fibers are excellent substitutes for manmade fibers because are biodegradables, resistant and sustentables. This article studied the potencial application of Carica Papaya Fibers (CPF) in polymerics composites of natural resin. A simple model of micromechanical analysis was used for prediction of breaking stress, strain and Young’s modulus in composites with short fibers of Carica Papaya with matrix of polyurethane resin obtained from Ricinus Communis vegetable. The fiber content used between 10–35% and fiber length between 3–6%. The analyzes were performed using analysis of variance (ANOVA) to assess the influence of variables on the mechanical properties of each composite produced. The results obtained show that increased in fiber length promoted increase in stress values, while the increase in fiber content favored the increased in the stiffness of the composite.

Formation of anisotropic properties in elastomeric nanocomposites

The mechanical properties of elastomeric composites along different loading directions are known to depend on their production technology (initial anisotropy) and on the loading history (induced anisotropy). It is also obvious that the geometry of the filler and its concentration in the matrix should have an effect on the formation of both the initial anisotropy in composites and the strain-induced anisotropy. In this study, the behavior of polymer composites was investigated depending on the type of filler particles (granular - carbon black, nanodiamonds; layered - graphene; fibrous - single-walled and multi-walled nanotubes). In the experiments, materials with different filler concentrations and with varying combinations of fillers were tested. Analysis of the results has revealed that the formation of the initial anisotropy is determined not only by the shape of the filler particles but also by their structure. It is shown that the induced anisotropy is clearly manifested itself in high-filled systems, but the way of its formation in composites strongly depends on the type of filler.

Joining behavior of polymeric composites fabricated using agricultural waste as fillers

The joining feasibility of natural fillers (wheat husk, rice husk and coir fiber) reinforced polymer composites has been studied. The different types of joints, i.e. adhesive joint (with and without hole), mechanically fastened, as well as hybrid joints (adhesive with riveting) have been analyzed in terms of their mechanical properties. The adhesive joints were found comparatively better in strength than adhesive joints with drilled hole. Anchorage effect of adhesive was found negligible in the drilled hole joint, and the joint failed at lower load due to the increase in stress concentration near the hole edge. At the same time, mechanical joining requires drilling of holes, which is still a challenging task in glass fiber reinforced plastic (GFRP) composites. The mechanical properties of the hybrid joints were found similar to adhesively bonded composites, but extension at the break in the hybrid joints was found higher than adhesively bonded joint (without hole).

Factors affecting the solid particle erosion of environment pollutant and natural particulate filled polymer composites—A review

Solid particle erosion of polymer matrix composites filled with naturally available and environment pollutant fillers have not been studied to the same level as for metals or ceramics and is focus of the present study. In this article, review of the research associated with the erosion response of polymer composites is presented. Particulate polymer composites are employed extensively owing to their enhanced specific properties and tribological response. Particulate filler particles such as environmental pollutants and naturally available ones need to be effectively incorporated in utilitarian applications so as to reduce land fill burden issues and other specific problems. Nevertheless, adequate data is not available in review articles on the erosion of fillers that are environment pollutants and thereby an ample amount of research can be carried out in this regard. Erosion behavior of polymer composites in particular has gained a lot of attention among researches in the recent decade. Viability of incorporating various fillers in polymer matrix for erosion resistive applications needs to be assessed so that the potential of these composites can be well understood. Therefore in this study, erosion response of polymer composites reinforced with fillers is reviewed with a focus on input parameters (impact velocity, impingement angle and erodent properties) and material properties (density).

Experimental Estimation of Relaxation Behavior for Hemp Fiber Reinforced Polypropylene Composite with Torque Rheometer

Relaxation behavior of natural fiber reinforced polymer composites exists in both solid and molten state and profoundly affects the control and optimization of processing parameters and dimensional accuracy of final products. The aim of this study was to establish an experimental estimating method to characterize relaxation behavior of polymer composite with traditional torque rheometer and investigate the effects of fiber concentration, dimension, and processing parameters on the relaxation behavior. Relaxation time of hemp fiber reinforced polypropylene composite were obtained by fitting the experimental torque data and corelated to the buckling deformation of packaging boxes manufactured by injection with the same injection parameters. The results show that all the increasing concentration of hemp fiber, higher rotor speed, and higher temperature can significantly decrease the relaxation time and result in a stable and better dimensional accuracy of injection packaging boxes. The finer fibers with the same weight concertation can bring an obvious reduction in relaxation time and buckling deformation. The proposed method for estimating relaxation behavior of polymer composite is a feasible and cost-effective way to investigate the viscoelastic properties of polymer composites close to the real processing conditions. And it can be widely used in optimization of processing parameters and performance of polymer composite products.

Modeling of fracture behavior in polymer composites using concurrent multi-scale coupling approach

ABSTRACTEmbedded statistical coupling method was originally developed to provide computational efficiency, to decrease coupling complexities, and to avoid the need to discretize the continuum model to atomic scale resolution in concurrent multi-scale modeling. An embedded statistical coupling method scheme is relatively easy to implement within a conventional finite element method code and has been tested in standard solid lattice structures. However, this method encounters difficulties when being implemented for amorphous materials like polymers, due to the fact that they lack specific ordered lattice structure and atoms may not be covalently bonded with each other, which are the requirements of common coupling schemes. Therefore, a new approach needs to be developed to resolve this problem. In this article, details of a modified embedded statistical coupling method approach for atomistic-continuum coupling developed to perform simulations of macroscale crack growth in polymers is presented. The presence of the continuum domain surrounding the molecular dynamics region allows for the application of far field loading, and prevents stress wave reflections from the external boundary impinging back on the crack tip. In our approach, a material point method, which is a meshless particle-in-cell method based on an arbitrary Euler-Lagrange scheme and has been proven to have good performance in large deformation problems, is used to model the continuum domain. It is concurrently coupled with molecular dynamics, a widely used method in atomistic simulations, using a so-called handshake region. Anchor points, the equilibrium positions of the constrained particles, which are designed to transmit displacements and forces between nanoscale and macroscale model, are defined in the handshake region. A concurrently coupled material point method-molecular dynamics simulation of crack propagation inside a polymer is performed to verify this new coupling approach, thereby providing a better understanding of the fracture mechanisms at the nanoscale to predict the macro-scale fracture toughness of a polymer system. Results are presented for concurrently coupled simulation of crack initiation and crack propagation in a di-functional cross-linked thermoset polymer, EPON 862.

Effect of Basalt Reinforcement Type and Content on the Abrasive Wear Behaviour of Polymer Composites

Basalt reinforced composites are quite recently (during last 20 years) developed materials having low density, high specific strength, good frictional, heat and chemical resistance. Natural mineral based fibres are potential alternatives to glass fibres for their strength and to carbon fibres for their lower cost. In order to use basalt reinforced composites for lightweight applications, it is necessary to perform wear characterisation. Basalt fibre, powder and scales reinforced, unsaturated polyester and epoxy resin composites were fabricated with various ratios of basalt and polymeric matrixes. The tribological behaviour of basalt reinforced composites was determined according to the ASTM G132 standard test method for pin abrasion testing. Results showed that type and content of reinforcement have a significant influence on the mechanical and tribological properties of the composites. Scanning electron microscope images are given to illustrate the wear mechanism of composites.

Projecting long-term non-Fickian diffusion behavior in polymeric composites based on short-term data: a 5-year validation study

The slow approach to equilibrium concentration indicative of non-Fickian diffusion in polymer composites necessitates experimental time frames which are often of limited feasibility. As a result, experimental studies are terminated prematurely due to time constraints or incorrect identification of equilibrium. Here, the three-dimensional anisotropic diffusion behaviors of six-, twelve-, and forty-ply quartz-reinforced bismaleimide laminates are quantified through a 5-year, full-immersion gravimetric absorption study. The applicability of the three-dimensional hindered diffusion model is investigated, while projections of future absorption behavior made at 21 months are revisited in light of 3 years of additional data. The mathematical equivalency of the hindered diffusion model and a diffusion–relaxation model under certain conditions is discussed. Moisture content rises continuously throughout the 5-year experiment for all samples. In the six-ply case, the standard termination criterion for the equilibrium condition is met before 6 months and 1.38 % moisture content by weight. Actual moisture content reaches 1.56 % after 5 years. The hindered diffusion model and associated forward projections of moisture content are found to conform well to experimental results.

Electrophysical properties of composite films based on multiwalled carbon nanotubes under hydrostatic pressure

The effect hydrostatic pressure of up to 9 GPa has on the electrical behavior of polymer composites based on multiwalled carbon nanotubes (MWCNT) is investigated at room temperature. The ratio R9GPa/R0 ≈ 7 for samples with resistance in the kilo-ohm range is higher than for samples in the ohm range. Pressure-induced MWCNT features at P ≈ 1.5 GPa are associated with the deformation of the circular form of nanotube walls, in agreement with theoretical predictions. Measurements of direct and reverse resistance and current voltage characteristics under pressure demonstrate the reversibility of electrophysical properties, which could find practical application in creating pressure sensors.

Micromechanical modeling on the rate-dependent viscoplastic behavior of polymer composites with thermal residual stress effect

The research focuses on the effect of thermal residual stress on the rate-sensitive viscoplastic behavior of polymer matrix composites with various fiber cross-sectional shapes. Micromechanical analysis was then conducted to incorporate the inelastic deformation and thermal residual stress into the micromechanical properties of a repeating cell and obtained the macromechanical response of polymer matrix composites by using homogenization theory. The responses of AS4/Polyetheretherketone (PEEK) with circular, square, and elliptical fibers are predicted by the method above at 10−5, 10−1, and 100/s with respect to 15°, 30°, 45°, 60°, 75°, and 90° off-axis angles. The results show that the viscoplastic difference of the response for various fiber shapes becomes more evident with the increase of strain rate. The effect of thermal residual stress varying with off-axis angle is similar to the sinusoidal curve. Besides, the thermal residual stress provides the largest effect on the response with square fiber and the smallest effect on the response with elliptical fiber, which of the effect decreases with the strain rate increasing.

Studies on the Performance of Polyester Composites Reinforced with Functionalized Grewia optiva Short Fibers

ABSTRACTThis paper deals with the fabrication and characterization of raw and surface‐modified Grewia optiva fibers reinforced unsaturated polyester (UPE) matrix based composites. Raw and surface‐modified fibers are used in different proportions (10, 20, 30, and 40%) for the fabrication of composites. The fiber proportion is optimized by studying various mechanical properties such as tensile, compressive, and flexural strength of UPE matrix‐based composites. After the optimization of fiber loadings, the optimized samples were evaluated for their physicochemical, thermal, fire retardancy, and biodegradability properties. Physicochemical and thermal stability of the composites is improved after fibers’ surface modification. The effect of different fire retardants (magnesium hydroxide and zinc borate) on the fire‐retardant behavior of polymer composites is also evaluated. Biodegradability of polymer composites is checked by using a soil burial method.

The left‐hand behaviour of polymer composites with Fe‐based microwires

AbstractIn the present paper, we deal with the electromagnetic properties of Fe‐rich microwire polymer meta‐composites prepared by embedding glass‐coated Fe‐based microwires into the E‐glass prepreg matrices in a parallel fashion. The free‐space measurement shows that a transmission window was created by adjusting the wire spacing below 7mm, which indicates that double negative index had been obtained. The correlation between the left‐handed feature with the local dielectric response has been established. The ‘natural' double negative behaviour is attributed to the intrinsic domain structure of Fe‐based ferromagnetic wires. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Predicting the behavior of polymer composites on the basis of a physical model of wear

The derivation of a physical model of wear from the empirical formula for wear is considered, with the goal of predicting the wear resistance of polymer composites. Formulas for the wear rate are proposed; these formulas take account of the content of disperse filler and the contact pressure.

Influence of Interphase Imperfection on Micro-Crack Behavior in Polymer Composites Filled by Rigid Particles

In this paper a particulate composites with polypropylene matrix and rigid mineral fillers are studied. The polymer particulate composites are frequently used in many engineering applications. Due to the physical and chemical interaction between matrix and particles a third phase (generally called interphase) is formed. The composite is modeled as a three-phase continuum. The properties of particles and interphase have a significant effect on the global behavior of the composite. On the basis of fracture mechanics methodology the interaction of micro-crack propagation in the matrix filled by rigid particles covered by the very soft interphase is analyzed. The effect of the composite structure on their mechanical properties is studied here from the theoretical point of view. The properties of particles and matrix were determined experimentally. Conclusions of this paper can contribute to a better understanding of the behavior of micro-crack in polymer particulate composites with respect to interphase.

Investigation Stress-Strain Behaviors of Glass/Polymer Composites

In this paper, a micromechanical model based on Generalized Method of Cells(GMC) for predicting stress-strain behaviors of polymer-matrix composites is presented. Improved Bodner-Partom viscoplastic model is incorporated into GMC to describe nonlinear mechanical behavior of composites. On this basis, strain rate and fiber volume fraction(FVF) influence on nonlinear behaviors of composites are discussed. The results show that strain rate influences on stress-strain behaviors of composites in inelastic region can be clearly discerned. Moreover, FVF tends to clearly increase stiffness behaviors of polymer-composites.