Analysis of the Linearly Viscoelastic Behavior of Nanotube-Reinforced Polymer Composites

2004 ◽  
Author(s):  
K. Li ◽  
X.-L. Gao ◽  
A. K. Roy
Keyword(s):  
Polymer Composites ◽  
Small Volume ◽  
Physical Aging ◽  
Volume Fraction ◽  
Viscoelastic Behavior ◽  
Analytical Models ◽  
Limited Attention ◽  
Creep Stress ◽  
Reinforced Polymer ◽  
Small Volume Fraction

In the last few years a lot of efforts have been made to demonstrate that the addition of carbon nanotubes, even with a small volume fraction, can substantially enhance the stiffness and strength of polymers [1]. Nevertheless, very limited attention has been paid to the viscoelastic responses of nanotube-reinforced polymer composites. Several groups have investigated the changes in glass transition temperatures of polymers induced by adding nanotubes to polymers [2–4]. Fisher [4] also studied the frequency response and the physical aging of polymers with or without nanotubes. However, the creep/stress relaxation behavior of nanotube-reinforced polymer composites is still not well understood. Experimental characterization tends to be configuration specific and expensive. Therefore, there is a need to develop analytical models that can predict the said behavior. The objective of this communication is to present a study on the creep behavior of carbon nanotube-reinforced polymer composites using a continuum-based micromechanics model.

On Viscoelasticity in CNT-Reinforced Polymer Composites

2010 ◽  
Author(s):  
K. Yazdchi ◽  
M. Salehi
Keyword(s):  
Polymer Composites ◽  
Volume Fraction ◽  
Viscoelastic Behavior ◽  
Limited Attention ◽  
Viscoelastic Problem ◽  
Neat Polymer ◽  
Reinforced Polymer ◽  
Equivalent Inclusion ◽  
Linear Viscoelastic Behavior ◽  
Linear Viscoelastic

The nanocomposites exhibit high electrical conductivity, significant non-linear optical behavior and electroluminescence, while having substantially improved mechanical properties relative to the neat polymer. However, very limited attention has been paid to the viscoelastic behavior of nanotube reinforced polymer composites (NTRPCs). In this paper, the constitutive relation and linear viscoelastic behavior of NTRPC are studied using methods of micromechanics and nanomechanics. First, the effects of volume fraction, aspect ratio and orientation of carbon nanotubes (CNTs), on the overall elastic properties of NTRPC are obtained through a micromechanical technique based on Eshelby’s Equivalent Inclusion (EEI) and Mori-Tanaka (MT) method. Secondly, by incorporating the Dynamic Correspondence Principle (DCP), the elastic solution is extended to solve the related linear viscoelastic problem. The results of this study are in good agreement when compared with previous analytical and experimental data.

Viscoelastic behavior of epoxy resin reinforced with shape-memory-alloy wires

2020 ◽  
pp. 1045389X2097549
Author(s):  
Niloufar Bagheri ◽  
Mahmood M Shokrieh ◽  
Ali Saeedi
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Epoxy Resin ◽  
Volume Fraction ◽  
Niti Alloy ◽  
Micromechanical Model ◽  
Viscoelastic Behavior ◽  
Mechanical Analysis ◽  
Reinforced Polymer ◽  
Small Volume Fraction

The effect of NiTi alloy long wires on the viscoelastic behavior of epoxy resin was investigated by utilizing the dynamic mechanical analysis (DMA) and a novel micromechanical model. The present model is capable of predicting the viscoelastic properties of the shape-memory-alloy (SMA) reinforced polymer as a function of the SMA volume fraction, initial martensite volume fraction, pre-strain level in wires, and the temperature variations. The model was verified by conducting experiments. Good agreement between the theoretical and experimental results was achieved. A parametric study was also performed to investigate the effect of SMA parameters. According to the results, by the addition of a small volume fraction of SMA, the storage modulus of the composite increases significantly, especially at higher temperatures. Moreover, applying a 4% pre-strain caused a 10% increase in the maximum value of the loss factor of the SMA reinforced epoxy in comparison with the 0% pre-strained SMA reinforced epoxy.

Experimental Model of Temperature-Driven Nanofluid

2006 ◽  
Vol 129 (6) ◽  
pp. 697-704 ◽  
Author(s):  
A. G. Agwu Nnanna
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Small Volume ◽  
Volume Fraction ◽  
Convective Heat Transfer Coefficient ◽  
Isothermal Condition ◽  
Carrier Fluid ◽  
Small Volume Fraction ◽  
The Impact

This paper presents a systematic experimental method of studying the heat transfer behavior of buoyancy-driven nanofluids. The presence of nanoparticles in buoyancy-driven flows affects the thermophysical properties of the fluid and consequently alters the rate of heat transfer. The focus of this paper is to estimate the range of volume fractions that results in maximum thermal enhancement and the impact of volume fraction on Nusselt number. The test cell for the nanofluid is a two-dimensional rectangular enclosure with differentially heated vertical walls and adiabatic horizontal walls filled with 27 nm Al2O3–H2O nanofluid. Simulations were performed to measure the transient and steady-state thermal response of nanofluid to imposed isothermal condition. The volume fraction is varied between 0% and 8%. It is observed that the trend of the temporal and spatial evolution of temperature profile for the nanofluid mimics that of the carrier fluid. Hence, the behaviors of both fluids are similar. Results shows that for small volume fraction, 0.2⩽ϕ⩽2% the presence of the nanoparticles does not impede the free convective heat transfer, rather it augments the rate of heat transfer. However, for large volume fraction ϕ>2%, the convective heat transfer coefficient declines due to reduction in the Rayleigh number caused by increase in kinematic viscosity. Also, an empirical correlation for Nuϕ as a function of ϕ and Ra has been developed, and it is observed that the nanoparticle enhances heat transfer rate even at a small volume fraction.

scholarly journals Comparison of Analytical Approaches Predicting the Compressive Strength of Fibre Reinforced Polymers

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2517 ◽  
Author(s):  
Christian Leopold ◽  
Sergej Harder ◽  
Timo Philipkowski ◽  
Wilfried Liebig ◽  
Bodo Fiedler
Keyword(s):  
Compressive Strength ◽  
Prediction Accuracy ◽  
Volume Fraction ◽  
Fibre Volume Fraction ◽  
Experimental Results ◽  
Analytical Models ◽  
Reinforced Polymers ◽  
Reinforced Polymer ◽  
Fibre Reinforced Polymer ◽  
Analytical Approaches

Common analytical models to predict the unidirectional compressive strength of fibre reinforced polymers are analysed in terms of their accuracy. Several tests were performed to determine parameters for the models and the compressive strength of carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP). The analytical models are validated for composites with glass and carbon fibres by using the same epoxy matrix system in order to examine whether different fibre types are taken into account. The variation in fibre diameter is smaller for CFRP. The experimental results show that CFRP has about 50% higher compressive strength than GFRP. The models exhibit significantly different results. In general, the analytical models are more precise for CFRP. Only one fibre kinking model’s prediction is in good agreement with the experimental results. This is in contrast to previous findings, where a combined modes model achieves the best prediction accuracy. However, in the original form, the combined modes model is not able to predict the compressive strength for GFRP and was adapted to address this issue. The fibre volume fraction is found to determine the dominating failure mechanisms under compression and thus has a high influence on the prediction accuracy of the various models.

Loading Rate Effect on Translaminar Fracture Toughness of Hybrid Composite Laminate

2000 ◽  
Author(s):  
Paul Moy ◽  
Jerome Tzeng
Keyword(s):  
Fracture Toughness ◽  
Composite Laminates ◽  
Glass Matrix ◽  
Small Volume ◽  
Loading Rate ◽  
Volume Fraction ◽  
Rate Effect ◽  
The Matrix ◽  
Small Volume Fraction ◽  
Matrix Property

Abstract Fracture toughness properties of composite laminates were evaluated at a loading rate commonly observed in ordinance applications. The laminates are composed of IM7 graphite and a small volume fraction of S2 glass plies to form a cross-ply laminate. Fracture toughness appears to be very rate sensitive if the crack growth perpendicular to the plane dominated by glass/matrix property. Experimental data shows a 30–40% increase of fracture toughness for various layup as the loading rate was increase by 1000 times. The specimens examined under microscopic indicates the strengthening might due to different failure mechanism in the matrix. In addition, there is no visible rate effect if the crack propagation is perpendicular to the graphite dominant plane.

scholarly journals Stress–Corrosion Cracking of AISI 316L Stainless Steel in Seawater Environments: Effect of Surface Machining

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1324
Author(s):  
Zhe Ren ◽  
Frank Ernst
Keyword(s):  
Stress Corrosion ◽  
Small Volume ◽  
Volume Fraction ◽  
Single Point ◽  
Crack Density ◽  
Aisi 316L ◽  
Surface Machining ◽  
Subsurface Zone ◽  
Small Volume Fraction ◽  
Effect Of Surface

To understand the effect of surface machining on the resistance of AISI 316L to SCC (stress–corrosion cracking) in marine environments, we tested nuts surface-machined by different methods in a seawater-spraying chamber. Two forms of cracks were observed: on the machined surface and underneath it. On the surface, cracks connected with the pitting sites were observed to propagate perpendicular to the hoop-stress direction, identifying them as stress–corrosion cracks. Under the surface, catastrophic transgranular cracks developed, likely driven by hydrogen embrittlement caused by the chloride-concentrating level of humidity in the testing environment. Under constant testing conditions, significantly different SCC resistance was observed depending on how the nuts had been machined. Statistical evaluation of the nut surface-crack density indicates that machining by a “form” tool yields a crack density one order of magnitude lower than machining by a “single-point” tool. Microstructural analysis of form-tool-machined nuts revealed a homogeneous deformed subsurface zone with nanosized grains, leading to enhanced surface hardness. Apparently, the reduced grain size and/or the associated mechanical hardening improve resistance to SCC. The nanograin subsurface zone was not observed on nuts machined by a single-point tool. Surface roughness measurements indicate that single-point-tool-machined nuts have a rougher surface than form-tool machined nuts. Apparently, surface roughness reduces SCC resistance by increasing the susceptibility to etch attack in Cl--rich solutions. The results of X-ray diffractometry and transmission electron microscopy diffractometry indicate that machining with either tool generates a small volume fraction (< 0.01) of strain-induced martensite. However, considering the small volume fraction and absence of martensite in regions of cracking, martensite is not primarily responsible for SCC in marine environments.

scholarly journals A 2D Multiphase Model of Drop Behavior during Electroslag Remelting

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 490
Author(s):  
Jérémy Chaulet ◽  
Abdellah Kharicha ◽  
Sylvain Charmond ◽  
Bernard Dussoubs ◽  
Stéphane Hans ◽  
...  
Keyword(s):  
Small Volume ◽  
Slag Phase ◽  
Volume Fraction ◽  
Liquid Pool ◽  
Electroslag Remelting ◽  
Multiphase Model ◽  
Momentum Exchange ◽  
Small Volume Fraction ◽  
Drag Law ◽  
Two Fluid

Electroslag remelting is a process extensively used to produce metallic ingots with high quality standards. During the remelting operation, liquid metal droplets fall from the electrode through the liquid slag before entering the liquid pool of the secondary ingot. To better understand the process and help to optimize the operating condition choice, a 2D axisymmetric multiphase model of the slag domain has been developed using a two fluid Eulerian approach. During their fall, droplets hydrodynamic interactions are calculated thanks to an appropriate drag law. Influence of droplets on the electromagnetic field and on the slag hydrodynamics is discussed, as well as their heat exchange with the slag. Even with a small volume fraction, the droplets influence is noticeable. The present investigation shows that small droplets have a large influence on the slag hydrodynamics, due to a great momentum exchange. However heat transfer is more influenced by large drops, which are found to be relatively far from the thermal equilibrium with the slag phase.

Tensile Properties of Epoxy Matrix Reinforced with Fique Fabric

2020 ◽  
Vol 1012 ◽  
pp. 14-19
Author(s):  
Michelle Souza Oliveira ◽  
Fabio da Costa Garcia Filho ◽  
Fernanda Santos da Luz ◽  
Artur Camposo Pereira ◽  
Luana Cristyne da Cruz Demosthenes ◽  
...  
Keyword(s):  
Mechanical Strength ◽  
Polymer Composites ◽  
Natural Fiber ◽  
Volume Fraction ◽  
Fiber Reinforced Polymer ◽  
Epoxy Composites ◽  
Synthetic Fiber ◽  
Fiber Reinforced ◽  
Reinforced Polymer ◽  
Fiber Reinforced Polymer Composites

Composite materials are being extensively studied for ballistic armor. Their main advantage is connected to the possibility of deeply reducing weight and costs by maintaining high performances in terms of strength and security. Epoxy composites are reinforced with natural fibers which are replacing other synthetic reinforcement materials. Composites are prepared using polymers as matrix material because of ease of production with different reinforcements. The mechanical strength of the natural fiber reinforced polymer composites has been compared with synthetic fiber reinforced polymer composites and it is found that for achieving equivalent mechanical strength of the material, the volume fraction of the natural fiber should be much higher than synthetic fiber. This work being an experimental study on untreated “as received” fique fabric-reinforced epoxy composites, to demonstrate the potential of this renewable source of natural fiber for use in a number of applications.

Electrothermomechanical Modeling and Analyses of Carbon Nanotube Polymer Composites

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
S. Xu ◽  
O. Rezvanian ◽  
M. A. Zikry
Keyword(s):  
Finite Element ◽  
Carbon Nanotube ◽  
Polymer Composites ◽  
Volume Fraction ◽  
Electron Tunneling ◽  
Three Dimensional ◽  
Fe Modeling ◽  
Aspect Ratios ◽  
Reinforced Polymer ◽  
Polymer Dispersions

A new finite element (FE) modeling method has been developed to investigate how the electrical-mechanical-thermal behavior of carbon nanotube (CNT)–reinforced polymer composites is affected by electron tunneling distances, volume fraction, and physically realistic tube aspect ratios. A representative CNT polymer composite conductive path was chosen from a percolation analysis to establish the three-dimensional (3D) computational finite-element (FE) approach. A specialized Maxwell FE formulation with a Fermi-based tunneling resistance was then used to obtain current density evolution for different CNT/polymer dispersions and tunneling distances. Analyses based on thermoelectrical and electrothermomechanical FE approaches were used to understand how CNT-epoxy composites behave under electrothermomechanical loading conditions.

Flow past periodic arrays of spheres at low Reynolds number

1997 ◽  
Vol 335 ◽  
pp. 189-212 ◽  
Author(s):  
HONGWEI CHENG ◽  
GEORGE PAPANICOLAOU
Keyword(s):  
Reynolds Number ◽  
Viscous Flow ◽  
Small Volume ◽  
Volume Fraction ◽  
Periodic Array ◽  
Periodic Arrays ◽  
Flow Past ◽  
Random Array ◽  
Single Sphere ◽  
Small Volume Fraction

We calculate the force on a periodic array of spheres in a viscous flow at small Reynolds number and for small volume fraction. This generalizes the known results for the force on a periodic array due to Stokes flow (zero Reynolds number) and the Oseen correction to the Stokes formula for the force on a single sphere (zero volume fraction). We use a generalization of Hasimoto's approach that is based on an analysis of periodic Green's functions. We compare our results to the phenomenological ones of Kaneda for viscous flow past a random array of spheres.

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