Epoxy Composite Materials Research Articles

Viscoelastic behavior of carboxylated multi-walled carbon nanotube reinforced epoxy composites with various frequencies

An ultrasonically assisted stirring mixing process was used to fabricate epoxy composites filled with pristine carbon nanotubes (P-CNTs) and functionalized CNTs (M-CNTs). The viscoelastic properties of the resulting nanocomposites are systematically evaluated by dynamic mechanical thermal analyses (DMTA). Fourier transform infrared spectroscopy proves the existence of carboxyl groups on the surface of M-CNT. It is found that both the storage modulus and glass transition temperature increased with the addition of M-CNTs. Furthermore, the peak of loss modulus and loss tangent shift to higher temperatures and the width of their curves become wider when the loading frequency goes up for all the samples. This effect is attributed to the reduction in the mobility of the epoxy matrix and leads to the observed increase in thermal stability. In the present work, a kind of epoxy with increased glass transition temperature and high thermal stability is obtained.

Fiber Diameter-Dependent Elastic Deformation in Polymer Composites—A Numerical Study

Abstract Microbeam bending and nano-indentation experiments illustrate that length scale-dependent elastic deformation can be significant in polymers at micron and submicron length scales. Such length scale effects in polymers should also affect the mechanical behavior of reinforced polymer composites, as particle sizes or diameters of fibers are typically in the micron range. Corresponding experiments on particle-reinforced polymer composites have shown increased stiffening with decreasing particle size at the same volume fraction. To examine a possible linkage between the size effects in neat polymers and polymer composites, a numerical study is pursued here. Based on a couple stress elasticity theory, a finite element approach for plane strain problems is applied to predict the mechanical behavior of fiber-reinforced epoxy composite materials at micrometer length scale. Numerical results show significant changes in the stress fields and illustrate that with a constant fiber volume fraction, the effective elastic modulus increases with decreasing fiber diameter. These results exhibit similar tendencies as in mechanical experiments of particle-reinforced polymer composites.

Epoxy Composites Based on Low-cost Carbon Filler Derived from Hydrothermal Carbonization of Waste

Different kinds of composites based on polymer matrix are present on the market. In particular, composites based on epoxy resin are used as high-performance polymers due to their excellent mechanical properties, chemical resistance, thermal stability and low cost production. Recently, in composites production the attention has been focused on the study of materials derived from biomass and organic waste to be used as filler.Hydrochar is a carbonaceous material obtained from hydrothermal carbonization (HTC) of biomasses and organic waste. During HTC biomass is carbonized in an aqueous environment at temperatures of 180-250?°C under saturated pressure (autogenous or provided by a gas) for several hours. For its characteristics, hydrochar can be potentially used as filler in composite materials in view of the growing concern about environmental sustainability.In this work, hydrochar obtained from hydrothermal carbonization of green waste was used as filler for the preparation of diglycidyl ether of bisphenol A-type epoxy composite materials. Two different epoxy matrices were used; the content of hydrochar was varied between 5 and 15 wt%. The resulting samples were characterized by morphologic and mechanical analyses, and electrical properties were evaluated. The addition of hydrochar to epoxy resins resulted in a slight increase of the elastic modulus, although there was a decrease in tensile strength and toughness. Moreover, electrical properties of epoxy resins were not significantly modified by the addition of hydrochar. Therefore, the study provided encouraging results for the production of innovative hydrochar-based epoxy composites, allowing the recycling and re-use of industrial waste.

Evaluation of Mechanical Properties of Kevlar Fibre Epoxy Composites: An Experimental Study

Kevlar fiber reinforced polymer composites are rapidly growing in manufacturing applications such bicycle tires and racing sails to body armor, bullet proof vests, military helmets, walking boots etc. Kevlar epoxy composite material using the Kevlar fiber and epoxy resin LY-556 was fabricated with manual hand layup procedure. The mechanical characteristics like tensile, impact strength and flexural rigidity were evaluated. With the results obtained it is found that kevlar epoxy composite provides better mechanical characteristics than aluminum. In this work, the possibility of replacing aluminum with Kevlar reinforced epoxy composite material is investigated for various applications viz. manufacturing of bus body frame, bullet proof vests, automobile body, sports applications, fire proof clothing, military helmets etc. Also, the FE analysis is carried out with MIDAS NFX software to correlate the test results with FEA.

Preparation of Thermally Conductive Polymer Composites with Good Electromagnetic Interference Shielding Efficiency Based on Natural Wood-Derived Carbon Scaffolds

In the modern electronic industry, multifunctional polymer composites associated with heat removal and electromagnetic shielding are highly needed. This work reports a method to fabricate epoxy composites with high electromagnetic interference shielding effectiveness (EMI SE) and thermal conductivity (TC) using natural wood as a starting material via backfilling epoxy into wood-derived carbon scaffolds. The results showed that after carbonization at 1200 °C, the carbon scaffolds could be well-maintained, which could serve as thermally and electrically conductive pathways in the composites. The resultant composites at the carbon loading of 7.0 vol % possessed a high TC of 0.58 W/(m·K), an electrical conductivity of about 12.5 S/m, and an average EMI SE of 27.8 dB over the X-band at the thickness of only 2 mm. Our work proposed a promising strategy to use cost-effective and green materials to fabricate multifunctional polymer composites.

Fabrication and characterization of S glass hybrid composites for Tie rods of aircraft

Abstract This paper explains the fabrication of S-Glass epoxy composite hybrid composite materials from a combination of 7-mill glass fabric, ceramic paper as intermediate and carbon fabric. The ceramic papers which acted as intermediate layers are treated with a mixture of short carbon fibers and carbon powder along with epoxy, epoxy terminated butadiene acrylonitrile (ETBN) and room temperature hardener. The composites are fabricated using Hand lay-up process and solidification of material is obtained through high temperature oven. Further these composite materials are machined to obtain required dimensions as per the design of shield for Tie-rod and splitter rod by considering Radar Cross Section calculation. Flexural and Inter Laminar Shear Strength (ILSS) tests were performed on S-Glass epoxy composite before and after machining. Flexural and Inter Laminar Shear Strength (ILSS) tests were considered in fabrication of Radom structures. Deviations observed in ILSS are around 3% to 18% and deviations observed in Flexural tests are 16% to 23%. In Flexural tests, the samples after machining have positive affect. Whereas, in ILSS tests, the machined samples have least effect. The tests obtained in S-Glass epoxy composite before and after machining were in allowable deviations.

An Artificial Neural Network (ANN) Model for Predicting Water Absorption of Nanoclay-Epoxy Composites

Glass fiber reinforced epoxy (GFRE) composite materials are prone to suffer from water absorption due to their heterogeneous structure. The main process governing water absorption is diffusion of water molecules through the epoxy matrix. However, hydrolytic degradation may also take place during components service life specially due high temperatures. In order to mitigate the effects of the water diffusive processes in the deterioration of in-service behavior of epoxy matrix composites, the use of chemically modified nanoclays as an additive has been proposed and studied in previous works [1]. In this work, an Artificial Neural Network (ANN) model was developed for better understanding and predicting the influence of modified and unmodified bentonite addition on the water absorption behavior of epoxy-anhydride systems. An excellent correlation between model and experimental data was found. The ANN model allowed the identification of critical points like the precise temperature at which a particular system’s water uptake goes beyond a predefined threshold, or which system will resist an immersion longer than a particular time.

Mechanical Properties of Epoxy Composite Materials Produced with Different Ceramic Powders

In this study, production and mechanical properties of polymer composite materials obtained by using Al2O3, SiO2, MgO and TiO2 hard ceramic fillers were studied. Epoxy resin was used as the matrix material, and four different ceramic powders were mechanically mixed into the resin at 3% and 5% as reinforcement. The mechanical properties of the polymer composite materials were then characterized. For this purpose, flexural modulus and flexural strength of composite materials were determined by using three point bending test and impact toughness of the materials were determined by Charpy impact test. In addition, the hardness values of the samples were determined by Shore D hardness test.

Mechanical Behaviour of Glass Fiber Reinforced Epoxy Composite Material

Mechanical Behaviour of Glass Fiber Reinforced Epoxy Composite Material

Fire resistant glass fabric-epoxy composites with reduced smoke emission

In this article a preparation method of epoxy resin/glass fabric composites with reduced flammability and smoke emission was presented. For this purpose the two groups of powder-epoxy compositions containing: (1) melamine polyphosphate (MPP) and aluminum diethyl phosphinate (AlDPi); (2) ammonium polyphosphate (APP) and dipentaerythritol (DPE) were used as matrices in six-ply glass fabric reinforced composites. The flame retardants content was 25 wt %. In addition, the 10–15 wt % of zinc borate (ZB) as a smoke reducing agent was added to each compositions. The flame resistant and smoke emission of prepared laminates designed for application in public transport components were evaluated. It was found that with the increase of zinc borate content, the emission of fumes decreased. The lowest maximum of specific optical density (Dsmax = 312.2), specific optical density in the first 4 minutes of the test [Ds(4) = 304.1] and cumulative specific optical densities in the first 4 minutes of the test (VOF4 = 707.6 min) have been achieved for composite containing 10 wt % of MPP, 15 wt % of AlDPi and 15 wt % of ZB. Furthermore, this composite was characterized by V0 class by UL94 test, limiting oxygen index LOI = 36.8 % and maximum average rate of heat emission MAHRE = 80 kW/m2.

Ethanothermal synthesis of phenol-derived carbon dots with multiple color emission via a versatile oxidation strategy

Herein, we report an ethanothermal synthesis of multicolor fluorescent carbon dots (CDs) by using a series of phenols and oxidants as the precursors. The emission colors of CDs are well-controlled at blue, green, yellow or red wavelengths by adjusting the combination of a phenol and an oxidant. And the naphthalenediol with highly reactivity and the oxidant with heavy halogen atom result in CDs exhibiting long wavelength emission. The resulting nanodots are characterized as amorphous aggregates with abundant oxygen species. The phenol-derived CDs can be used as highly processible fillers to fabricate epoxy composites, and a white light-emitting diode (LED) employing the multicolor CDs/epoxy composite as the light converter is also demonstrated.

BaTiO3\Epoksi Kompozit Malzemelerin Kapasitör Uygulamaları İçin Üretimi Ve Karakterizasyonu

Son yillarda elektronik devrelerin uretim yogunlugunun artmasi ile elektrik devrelerinin mikron mertebesinde kucultulmesine ihtiyac duyulmustur. Bu kucuklukteki bir elektronik devrenin cok yuksek bir performansa sahip olmasi gerekir. Dielektrik sabiti degeri yuksek oldugu bilinen BaTiO3(1200-1250 F\m) yalitkanligi yuksek epoksi recine ile guclendirilirse kapasitorlerde kullanim alani bulacak dielektrik sabiti cok yuksek ayni zamanda dielektrik kayibi cok dusuk olan bir malzeme uretilebilir. Bunun icin oncelikle BaTiO3 tozu geleneksel toz hazirlama yontemlerine gore hazirlanir, daha sonra agirlikca %72, %70 ve %68 oranlarinda BaTiO3, 1:2 ve 1:4 epoksi-sertlestirici oranina sahip recinelerle birlestirilip kompozit malzeme olarak uretilir. Neticede dielektrik kayibi dusuk olan plakalarla elektrik kacagini minimum duzeye indirecek homojen urunler elde edilmistir.

Study on carbon epoxy composite surfaces machined by abrasive water jet machining

Traditional machining of carbon epoxy composite material is difficult due to excessive tool wear, excessive stresses and heat generation, delamination, high surface waviness, etc. In the present paper, research work involved in the experimental study of abrasive water jet machining of carbon epoxy composite material is described. The aim of present work is to improve surface finish and studying defects in machined samples. Taguchi's orthogonal array approach is used to design experiments. Process parameters namely hydraulic pressure, traverse rate, stand-off distance and abrasive mass flow rate are considered for this study. Analysis of machined surfaces and kerf quality is carried out using scanning electron microscope to evaluate microscopic features. Further, the effect of machining parameters on surface roughness is investigated using analysis of variance approach. It is found that traverse rate and pressure are most significant parameters to control surface roughness. Optimization of process parameters is performed using grey relational analysis. Thereafter, confirmation tests are carried out to verify the improvement in the surface quality with optimum set of process parameters. It is found that surface finish of machined samples is improved by 10.75% with optimum levels of process parameters. Defects like delamination, fiber pull-out and abrasive embedment are also studied using SEM. It is observed that delamination and fiber pull-out are prominent in samples machined at low pressure and high traverse rate.

Failure mode analysis of ramie fiber reinforced composite material

This study aims to determine the failure mode of ramie fiber reinforced epoxy composite materials (RFRECM). The method used is testing the composite test sample that includes tensile test according to ASTM D 3039/D3039M, compression test according to ASTM D 695, simulation by using computer software, and morphology analysis by using Scanning Electron Microscope (SEM). The results show that RFRECM has SR ≥1 for failure criteria derived from stress theory, strain theory, and Tsai-Wu criteria, while having SR <1 only for the criteria of Tsai-Hill. Theoretically, the epoxy flax fiber composite has good strength in fiber or longitudinal direction (00) and decreases with the addition of the angle of the fiber. The failure mode of RFRECM is caused by voids, initial cracks, delimination and debonding occurring between 5-10% of the total area observed in the test sample. This condition can occur in all test samples as a result of imperfections of the fabrication process.

Research into parameters of magnetic treatment to modify the disperse­filled epoxy composite materials

Improving the operational properties of epoxy composites makes it possible to extend the scope of their application. One of the techniques to enhance the strength and durability of epoxy composites is the use of magnetic treatment. In order to modify polymeric compositions under the influence of a magnetic field, it is necessary to maintain the optimal treatment modes and time-temperature conditions, determining which is the aim of this research. The result of the conducted experimental research is the established influence of parameters of an alternating magnetic field on physical-mechanical properties of the modified epoxy composites. We investigated patterns in the influence of proportionality coefficients, integration and differentiation coefficients in the algorithm to control magnetic treatment on impact viscosity and heat resistance of the modified epoxy composites. The optimum values for the frequency of an alternating magnetic field during treatment of epoxy composites were determined. We examined dependences of the content of a finely-dispersed ferromagnetic filler on residual stresses and temperature in the zone of magnetic treatment. Research into epoxy composites was accompanied by the parallel tests of properties related to the effect of similar temperature at magnetic treatment. The law of change in temperature parameters without magnetic treatment was assigned similarly to that of magnetic treatment. This paper reports results of the mathematical planning of the experiment and correlation dependences of magnetic field induction and the content of a filler on heat resistance of the modified epoxy-composite material. The research identified limiting values for the content of a filler and treatment modes of epoxy-composite materials, which ensure the improved performance properties. Our study is important for improving the technological process to modify epoxy compositions with magnetic treatment

Dielectric properties of epoxy composites with mixed fillers including graphite nanoplatelets/BaTiO3

The electrical properties of L285 epoxy composite materials (CMs) with a mixed filler including graphite nanoplatelets (GNP)/barium titanate(BT) at various GNP concentrations and at 35 wt.% of BT are measured using the AC impedance spectroscopy with frequencies ranging from 1 kHz to 2 MHz. The complex permittivity and its frequency dependence increase with the GNP content. The addition of a BT filler in GNP/L285 CM increases the percolation threshold in addition to a slight increase in the permittivity, allowing a higher GNP content in the composite without the formation of a conductive network. The AC conductivity increases and its dependence on the frequency decreases, as the GNP content increases.

Modelling of mechanical failure due to constrained thermal expansion at the lightning arc attachment point in carbon fibre epoxy composite material

Abstract Examination of artificial lightning strike test damage suggests that mechanical loading contributes to some aspects of composite material degradation and failure. So far numerical work has focused on modelling resistive heating from the electrical load and a very limited number of studies have considered the thermal induced mechanical effects. Also preceding work which has modelled the effect of acoustic pressure loading has predicted the influence on specimen damage to be negligible. Thus the objective of this paper is to quantify the potential magnitude of the internal specimen mechanical loading resulting from electrical load induced thermal expansion. This is achieved through a simulation study and the definition of a bespoke modelling procedure to map specimen time dependent temperature from a thermal-electric analysis into a mechanical thermal-expansion analysis. The study compares predicted behaviour with measured test specimen damage. The results for the first time quantify the potential scale of loading resulting from constrained thermal expansion, the dimensions of induced damage and the strain rate magnitudes required for accurate material representation.

Optimization of Solid Particle Erosion by ZrN Coating Applied Fiber Reinforced Composites by Taguchi Method

In this study, ZrN coatings are applied on glass and carbon fiber reinforced epoxy composite materials by magnetron sputtering method to gain an improved understanding of the solid particle erosion (SPE) wear resistance. The tests were carried out by selecting two different impact velocities (34, 53 m/s), four different impingement angles (30°, 45°, 60°, 90°) and two different abrasive (SiO2) particle sizes (approximate 250, 500 m). The thickness of ZrN coating material was 0.15 m. Protective coatings produced by using Physical Vapor Deposition (PVD) method can increase the life time of the components. All test specimens regardless of their various parameter properties exhibit maximum erosion rates at 45 impingement angle and thus exhibiting similar behavior as that observed for semi ductile materials. Optic microscopic views were performed on the surfaces in order to characterize the erosion mechanism. The erodent particles of the both coating layer and composite matrix were found of main role in governing the wear progression. The measured erosion rates were sensitively correlated with the material removal process in order to explain the changes within the coated interfaces. Moreover, an erosion test facility at room temperature and Taguchi’s orthogonal arrays were used for experimentation. The expression derived from the results of Taguchi experimental design is proposed as a predictive equation for estimation of erosion rate of these composites. It is demonstrated that the predicted results from this equation are consistent with the experimental observations. Finally, an optimal parameter combination was determined, which led to minimization of erosion rate (ER).

The use of Digital Image Correlation in determining the mechanical properties of materials

The main purpose of this paper is to study the use of Digital Image Correlation in order to determine the Poisson’s ratio in the case of aluminium alloy and composite materials under tensile tests. The satisfactory results obtained in the case of specimens made of aluminium alloy prove that Digital Image Correlation is able to satisfy the requirements in order to determine the Poisson’s ratio. The testing procedure was carried out for two kinds of composite materials: (1) jute / epoxy composite material; (2) jute / glass / epoxy composite material. During the tests, a digital camera was used to capture the images of the tensile specimen during the tensile test. In order to measure both the longitudinal strain in direction of the tensile force and the transverse strain, the Digital Image Correlation method is used in the post-processing of all images recorded for each specimen. The data of transverse strain related to the longitudinal strain were graphically shown. The initial portion of curve corresponding to the linear portion of the stress-strain curve, was approximated by a linear regression function for each specimen tested. The slope of the fitting line represents Poisson’s ratio. The Poisson’s ratio, corresponding to the reinforcing plane with fabric for Jute / epoxy composite, is 35.5% greater than the corresponding to Jute / glass / epoxy composite.

Mode II Interlaminar Fracture Properties of Treated Silk Fibre/ Epoxy Composites at Low and High Temperature Range

Composite materials have a wide range of applications including as an automotive components. In certain applications it is exposed to various heat conditions and might affect its mechanical properties. It is important to be able to predict the behavior of the composites under different temperature settings in order to prevent failure. The GIIC properties of composite epoxy laminate with silk fibre at various temperatures have yet to be investigated by any researcher. This study was carried out to analyse the Mode II interlaminar fracture properties, GIIC of the silk fibre / epoxy composite materials when treated with silane coupling agents at different test temperatures. This property is important since it provides the measure of the material’s resistance to delamination crack propagation. Composite specimens were produced using compression moulding technique with sixteen layers of silk fabric. The matrix is an epoxy D.E.R 331 and Hardener Joint mine 905-3S. The weight ratio of mixing epoxy and hardener is 2:1. Six sets of sample were prepared using silk fibre which has undergone surface treatment for 24 hour using silane coupling agent surface treatment solution. Specimens were tested by Instron Universal Testing Machine using a three-point bending based on an end notched flexural (ENF) method. The tests were carried out at six different temperatures which are at 20 oC, 23 oC, 26 oC, 38 oC, 50 oC and 75 oC. The temperature of the specimens during testing was monitored using a thermal imager in order determine the exact test temperature. It was found that as the temperatures increases, the mode II fracture toughness decreases by up to 71%. The length of crack propagation shows that higher temperature leads to longer crack length. This could be due to the residual tension between the fibre and matrix as they have different thermal coefficient of expansion.