Dynamic mechanical, thermal, and dielectric properties of ZnO varistor-epoxy composite material

AbstractThe electrospray deposition method was used to deposit carbon nanotubes (CNT) onto the surfaces of woven carbon fiber (CF) to produce woven hybrid carbon fiber–carbon nanotubes (CF–CNT). Extreme high-resolution field emission scanning electron microscopy (XHR-FESEM), X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR) were used to analyze the woven hybrid CF–CNT. The results demonstrated that CNT was successfully and homogenously distributed on the woven CF surface. Woven hybrid CF–CNT epoxy composite laminates were then prepared and compared with woven CF epoxy composite laminates in terms of their flexural and dielectric properties. The results indicated that the flexural strength, flexural modulus and dielectric constant of the woven hybrid CF–CNT epoxy composite laminates were improved up to 19, 27 and 25%, respectively, compared with the woven CF epoxy composite laminates.

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Effect of Terminal Groups on Thermomechanical and Dielectric Properties of Silica–Epoxy Composite Modified by Hyperbranched Polyester

Polymers ◽

10.3390/polym13152451 ◽

2021 ◽

Vol 13 (15) ◽

pp. 2451

Author(s):

Jianwen Zhang ◽

Dongwei Wang ◽

Lujia Wang ◽

Wanwan Zuo ◽

Lijun Zhou ◽

...

Keyword(s):

Dielectric Constant ◽

Dielectric Properties ◽

Binding Energy ◽

Epoxy Resin ◽

Volume Fraction ◽

Epoxy Composite ◽

Mean Square Displacement ◽

Mean Square ◽

Hyperbranched Polyester ◽

Free Volume Fraction

To study the effect of hyperbranched polyester with different kinds of terminal groups on the thermomechanical and dielectric properties of silica–epoxy resin composite, a molecular dynamics simulation method was utilized. Pure epoxy resin and four groups of silica–epoxy resin composites were established, where the silica surface was hydrogenated, grafted with silane coupling agents, and grafted with hyperbranched polyester with terminal carboxyl and terminal hydroxyl, respectively. Then the thermal conductivity, glass transition temperature, elastic modulus, dielectric constant, free volume fraction, mean square displacement, hydrogen bonds, and binding energy of the five models were calculated. The results showed that the hyperbranched polyester significantly improved the thermomechanical and dielectric properties of the silica–epoxy composites compared with other surface treatments, and the terminal groups had an obvious effect on the enhancement effect. Among them, epoxy composite modified by the hyperbranched polyester with terminal carboxy exhibited the best thermomechanical properties and lowest dielectric constant. Our analysis of the microstructure found that the two systems grafted with hyperbranched polyester had a smaller free volume fraction (FFV) and mean square displacement (MSD), and the larger number of hydrogen bonds and greater binding energy, indicating that weaker strength of molecular segments motion and stronger interfacial bonding between silica and epoxy resin matrix were the reasons for the enhancement of the thermomechanical and dielectric properties.

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Enhancement of the Dynamic Mechanical and Dielectric Properties of Prosopis juliflora Fiber-Reinforced Composites by Fiber Modification

Journal of Natural Fibers ◽

10.1080/15440478.2021.1932676 ◽

2021 ◽

pp. 1-17

Author(s):

P. Venkateshwar Reddy ◽

R. V. Saikumar Reddy ◽

B. Veerabhadra Reddy ◽

D. Mohana Krishnudu ◽

P. Rajendra Prasad ◽

...

Keyword(s):

Dielectric Properties ◽

Prosopis Juliflora ◽

Fiber Reinforced Composites ◽

Reinforced Composites ◽

Fiber Reinforced ◽

Fiber Modification ◽

Dynamic Mechanical

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Multiscale Characterization of E-Glass/Epoxy Composite Exposed to Extreme Environmental Conditions

Journal of Composites Science ◽

10.3390/jcs5030080 ◽

2021 ◽

Vol 5 (3) ◽

pp. 80

Author(s):

George Youssef ◽

Scott Newacheck ◽

Nha Uyen Huynh ◽

Carlos Gamez

Keyword(s):

Power Distribution ◽

Epoxy Composite ◽

Fire Retardant ◽

Sandwich Composite ◽

Dynamic Mechanical Analyzer ◽

Fire Event ◽

Balsa Wood ◽

X Ray ◽

Dynamic Mechanical ◽

Composite Skins

Fiber-reinforced polymer matrix composites continue to attract scientific and industrial interest since they offer superior strength-, stiffness-, and toughness-to-weight ratios. The research herein characterizes two sets of E-Glass/Epoxy composite skins: stressed and unstressed. The stressed samples were previously installed in an underground power distribution vault and were exposed to fire while the unstressed composite skins were newly fabricated and never-deployed samples. The mechanical, morphological, and elemental composition of the samples were methodically studied using a dynamic mechanical analyzer, a scanning electron microscope (SEM), and an x-ray diffractometer, respectively. Sandwich composite panels consisting of E-glass/Epoxy skin and balsa wood core were originally received, and the balsa wood was removed before any further investigations. Skin-only specimens with dimensions of ~12.5 mm wide, ~70 mm long, and ~6 mm thick were tested in a Dynamic Mechanical Analyzer in a dual-cantilever beam configuration at 5 Hz and 10 Hz from room temperature to 210 °C. Micrographic analysis using the SEM indicated a slight change in morphology due to the fire event but confirmed the effectiveness of the fire-retardant agents in quickly suppressing the fire. Accompanying Fourier transform infrared and energy dispersive X-ray spectroscopy studies corroborated the mechanical and morphological results. Finally, X-ray diffraction showed that the fire event consumed the surface level fire-retardant and the structural attributes of the E-Glass/Epoxy remained mainly intact. The results suggest the panels can continue field deployment, even after short fire incident.

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Preparation of epoxy composite material containing natural aluminosilicate filler

Polymer Science Series D ◽

10.1134/s1995421211040125 ◽

2011 ◽

Vol 4 (4) ◽

pp. 281-283 ◽

Cited By ~ 3

Author(s):

P. A. Sitnikov ◽

A. V. Kuchin ◽

A. G. Belykh ◽

I. N. Vaseneva ◽

Yu. I. Ryabkov

Keyword(s):

Composite Material ◽

Epoxy Composite ◽

Natural Aluminosilicate

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The Estimation of Thermal Conductivity for Alumina-Epoxy Composite Material with High Filling Volume Fraction

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.918.21 ◽

2014 ◽

Vol 918 ◽

pp. 21-26

Author(s):

Chen Kang Huang ◽

Yun Ching Leong

Keyword(s):

Thermal Conductivity ◽

Composite Material ◽

Composite Materials ◽

Physical Model ◽

Electron Scattering ◽

Volume Fraction ◽

Epoxy Composite ◽

The Matrix ◽

Transport Theorem ◽

Good Agreement

In this study, the transport theorem of phonons and electrons is utilized to create a model to predict the thermal conductivity of composite materials. By observing or assuming the dopant displacement in the matrix, a physical model between dopant and matrix can be built, and the composite material can be divided into several regions. In each region, the phonon or electron scattering caused by boundaries, impurities, or U-processes was taken into account to calculate the thermal conductivity. The model is then used to predict the composite thermal conductivity for several composite materials. It shows a pretty good agreement with previous studies in literatures. Based on the model, some discussions about dopant size and volume fraction are also made.

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

Journal of Composite Materials ◽

10.1177/0021998318807278 ◽

2018 ◽

Vol 53 (20) ◽

pp. 2909-2924 ◽

Cited By ~ 8

Author(s):

Ajit Dhanawade ◽

Shailendra Kumar

Keyword(s):

Surface Roughness ◽

Composite Material ◽

Process Parameters ◽

Surface Finish ◽

Epoxy Composite ◽

Water Jet ◽

Machining Parameters ◽

Abrasive Water Jet ◽

Abrasive Water Jet Machining ◽

Pull Out

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.

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