scholarly journals Investigation of the Viscoelastic Behavior Variation of Glass Mat Thermoplastics (GMT) in Compression Molding

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 335 ◽  
Author(s):  
Chao-Tsai Huang ◽  
Ling-Jue Chen ◽  
Tse-Yu Chien
Keyword(s):  
Rheological Properties ◽  
Polymer Matrix ◽  
Power Law ◽  
Compression Molding ◽  
Rheological Parameters ◽  
Separation Effect ◽  
Matrix Separation ◽  
Viscoelastic Parameters ◽  
Matrix Interactions ◽  
Power Law Index

Compression molding is a lightweight technology that allows to preserve fiber length and retain better mechanical properties compared to injection molding. In compression molding development, a suitable material such as glass fiber mat thermoplastics (GMT) is often used. However, because of the complicated micro-structure of the fibers and the fiber–resin matrix interactions, it is still quite challenging to understand the mechanism of compression molding and it is very difficult to obtain a uniformly compressed GMT product. In this study, we propose a method to measure the rheological properties of GMT through a compression system. Specifically, we utilized a compression molding system to record the relation between the loading force and the displacement. This quantitative information was used to estimate the power-law index and viscoelastic parameters and predict viscosity. Moreover, the estimated viscoelastic parameters of GMT were implemented into Moldex3D to evaluate the flow behavior under compression. The results showed that the trend of the loading force variation was consistent in numerical simulation and experiments. However, at the final stage of compression molding, the experimental loading force was much higher than that estimated by simulation. To find out the mechanism causing this deviation, a series of studies were performed. Through TGA measurement, we found that the fiber content of the center portion of the compressed part increased from 63% to 85% during compression. This was expected, as a result of the fiber–polymer matrix separation effect. This fiber–polymer matrix separation effect influenced the power-law index and rheological parameters of GMT, making them fluctuate. Specifically, the power-law index changed from 1.0 to 0.62. These internal changes of the rheological properties further induced a much higher loading force in the real experimental GMT system. We further verified the rheological properties variation using pure polyamide (PA) and found that since there is no fiber–polymer matrix interactions the power-law index and curve-fitting rheological parameters were almost constant. The mechanism causing the deviation was therefore validated.

Thermorheological Characterization of Elastoviscoplastic Carbopol Ultrez 20 Gel

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
M. A. Hassan ◽  
Manabendra Pathak ◽  
Mohd. Kaleem Khan
Keyword(s):  
Experimental Investigation ◽  
Yield Stress ◽  
Elastic Properties ◽  
Viscous Dissipation ◽  
Power Law ◽  
Effect Of Temperature ◽  
Rheological Parameters ◽  
Frequency Range ◽  
Power Law Index

The temperature and concentration play an important role on rheological parameters of the gel. In this work, an experimental investigation of thermorheological properties of aqueous gel Carbopol Ultrez 20 for various concentrations and temperatures has been presented. Both controlled stress ramps and controlled stress oscillatory sweeps were performed for obtaining the rheological data to find out the effect of temperature and concentration. The hysteresis or thixotropic seemed to have negligible effect. Yield stress, consistency factor, and power law index were found to vary with temperature as well as concentration. With gel concentration, the elastic effect was found to increase whereas viscous dissipation effect was found to decrease. Further, the change in elastic properties was insignificant with temperature in higher frequency range of oscillatory stress sweeps.

scholarly journals Viscosity Estimation of a Suspension with Rigid Spheres in Circular Microchannels Using Particle Tracking Velocimetry

Micromachines ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 675 ◽  
Author(s):  
Kawaguchi ◽  
Fukui ◽  
Funamoto ◽  
Tanaka ◽  
Tanaka ◽  
...  
Keyword(s):  
Rheological Properties ◽  
Power Law ◽  
Particle Tracking ◽  
Particle Tracking Velocimetry ◽  
Colloidal Particles ◽  
Fluid Model ◽  
Relative Viscosity ◽  
Circular Cross Section ◽  
Rigid Spheres ◽  
Power Law Index

Suspension flows are ubiquitous in industry and nature. Therefore, it is important to understand the rheological properties of a suspension. The key to understanding the mechanism of suspension rheology is considering changes in its microstructure. It is difficult to evaluate the influence of change in the microstructure on the rheological properties affected by the macroscopic flow field for non-colloidal particles. In this study, we propose a new method to evaluate the changes in both the microstructure and rheological properties of a suspension using particle tracking velocimetry (PTV) and a power-law fluid model. Dilute suspension (0.38%) flows with fluorescent particles in a microchannel with a circular cross section were measured under low Reynolds number conditions (Re ≈ 10−4). Furthermore, the distribution of suspended particles in the radial direction was obtained from the measured images. Based on the power-law index and dependence of relative viscosity on the shear rate, we observed that the non-Newtonian properties of the suspension showed shear-thinning. This method will be useful in revealing the relationship between microstructural changes in a suspension and its rheology.

The effect of the addition of a slip agent on the rheological properties of polyethylene: off-line and in-line measurements

2019 ◽  
Vol 39 (5) ◽  
pp. 422-431 ◽  
Author(s):  
Arkadiusz Kloziński ◽  
Paulina Jakubowska
Keyword(s):  
Rheological Properties ◽  
Power Law ◽  
Extrusion Process ◽  
Low Density Polyethylene ◽  
Rheological Parameters ◽  
Low Density ◽  
Polymer Modification ◽  
Modified Polymer ◽  
Extrusion Head ◽  
Slip Agent

Abstract The article describes an investigation into the effect of a slip agent on the rheological properties of low-density polyethylene. As a slip modifier, oleamide was used in the amounts of 0.5, 1.0, 2.0, 3.0 and 4.0 wt.%, respectively. The process of polymer modification was carried out in a twin-screw extrusion process. The effect of the slip agent on the mass flow rate index was determined. The specific plasticisation energy of the modified polymer was also assessed based on the change in the torque of a batch mixer. The assessment of the effect of the addition of oleamide on the change in the flow and viscosity curves was made using an off-line (plastometer) and an in-line (extruder rheometer) measuring technique. The rheological parameters were determined based on the Ostwald-de-Waele power law model. The operation of the plastometer was brought closer to the principles of operation of the capillary rheometer by applying variable piston loading. In in-line measurements, an extrusion head with replaceable cylindrical dies was used. Using two rheological measuring techniques made it possible to determine the low-density polyethylene viscosity variations and the values of flow power law index (n) and consistency factor (K) in a wide shear rate range.

Annular Shear-Thinning Flow Over an Axisymmetric Sudden Expansion

2016 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Power Law ◽  
Shear Thinning ◽  
Sudden Expansion ◽  
Rheological Parameters ◽  
Recirculation Region ◽  
Flow Recirculation ◽  
Flow Stagnation ◽  
Power Law Index ◽  
Annular Pipe ◽  
Steady Laminar

Suddenly expanding annular pipe flows of a shear-thinning non-Newtonian fluid were numerically investigated within the steady laminar flow regime. The power-law constitutive equation is used to model the rheology of interest. A parametric study is performed to reveal the influence of annular diameter ratio, k, and power-law index, n, over the following range of parameters: k = {0, 0.5, 0.7} and n = {1, 0.8, 0.6}. Flow separation and entrainment, downstream of the expansion plane, creates two recirculation regions. The first is a central recirculation region between the expansion plane and the flow stagnation point along the centerline. A second, corner recirculation region forms between the expansion plane and the flow reattachment point along the wall. The results demonstrate impact of the investigated geometrical and rheological parameters on the extent and intensity of both flow recirculation regions, the wall shear stress distribution, and the evolution and redevelopment characteristics of the flow downstream the expansion plane.

Properties of nanocomposites based on isotactic polypropylene and high-pressure polyethylene with metal-containing nanofillers

2020 ◽  
pp. 59-64
Author(s):  
N. I. Kurbanova ◽  
◽  
T. M. Gulieva ◽  
N. Ya. Ischenko ◽  
◽  
...  
Keyword(s):  
High Pressure ◽  
Synergistic Effect ◽  
Polymer Matrix ◽  
Isotactic Polypropylene ◽  
Rheological Parameters ◽  
Mechanochemical Method ◽  
X Ray ◽  
Effect Of Additives ◽  
High Pressure Polyethylene ◽  
Properties Of Composites

The effect of additives of nanofillers (NF) containing nanoparticles (NP) of copper oxide, stabilized by a polymer matrix of maleized polyethylene (MPE), obtained by the mechanochemical method, on the properties of composites based on isotactic polypropylene (PP) and high-pressure polyethylene (PE) was studied by X-ray phase (XRD) and thermogravimetric (TGA) analyzes. The enhancement of strength, deformation, and rheological parameters, as well as the thermo-oxidative stability of the obtained nanocomposites was revealed, which, apparently, is due to the synergistic effect of the interaction of copper-containing nanoparticles with anhydride groups of MPE. It is shown that nanocomposites based on PP/PE/NF can be processed both by pressing and injection molding and extrusion, which expands the scope of its application.

Elastic Foundation Analysis of Uniformly Loaded Functionally Graded Viscoelastic Sandwich Plates

2012 ◽  
Vol 28 (3) ◽  
pp. 439-452 ◽  
Author(s):  
A. M. Zenkour ◽  
M. Sobhy
Keyword(s):  
Power Law ◽  
Sandwich Plate ◽  
Plate Theory ◽  
Functionally Graded ◽  
Sandwich Plates ◽  
Equilibrium Equations ◽  
Graded Material ◽  
Plate Aspect Ratio ◽  
Type V ◽  
Power Law Index

AbstractThis paper deals with the static response of simply supported functionally graded material (FGM) viscoelastic sandwich plates subjected to transverse uniform loads. The FG sandwich plates are considered to be resting on Pasternak's elastic foundations. The sandwich plate is assumed to consist of a fully elastic core sandwiched by elastic-viscoelastic FGM layers. Material properties are graded according to a power-law variation from the interfaces to the faces of the plate. The equilibrium equations of the FG sandwich plate are given based on a trigonometric shear deformation plate theory. Using Illyushin's method, the governing equations of the viscoelastic sandwich plate can be solved. Parametric study on the bending analysis of FG sandwich plates is being investigated. These parameters include (i) power-law index, (ii) plate aspect ratio, (iii) side-to-thickness ratio, (iv) loading type, (v) foundation stiffnesses, and (vi) time parameter.

scholarly journals Jet Impingement Heat Transfer of Confined Single and Double Jets with Non-Newtonian Power Law Nanofluid under the Inclined Magnetic Field Effects for a Partly Curved Heated Wall

2021 ◽  
Vol 13 (9) ◽  
pp. 5086
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Oztop ◽  
Ali J. Chamkha
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Particle Size ◽  
Aspect Ratio ◽  
Power Law ◽  
Volume Fraction ◽  
Inclined Magnetic Field ◽  
Magnetic Field Effects ◽  
Power Law Nanofluid ◽  
Power Law Index

Single and double impinging jets heat transfer of non-Newtonian power law nanofluid on a partly curved surface under the inclined magnetic field effects is analyzed with finite element method. The numerical work is performed for various values of Reynolds number (Re, between 100 and 300), Hartmann number (Ha, between 0 and 10), magnetic field inclination (γ, between 0 and 90), curved wall aspect ratio (AR, between 01. and 1.2), power law index (n, between 0.8 and 1.2), nanoparticle volume fraction (ϕ, between 0 and 0.04) and particle size in nm (dp, between 20 and 80). The amount of rise in average Nusselt (Nu) number with Re number depends upon the power law index while the discrepancy between the Newtonian fluid case becomes higher with higher values of power law indices. As compared to case with n = 1, discrepancy in the average Nu number are obtained as −38% and 71.5% for cases with n = 0.8 and n = 1.2. The magnetic field strength and inclination can be used to control the size and number or vortices. As magnetic field is imposed at the higher strength, the average Nu reduces by about 26.6% and 7.5% for single and double jets with n greater than 1 while it increases by about 4.78% and 12.58% with n less than 1. The inclination of magnetic field also plays an important role on the amount of enhancement in the average Nu number for different n values. The aspect ratio of the curved wall affects the flow field slightly while the average Nu variation becomes 5%. Average Nu number increases with higher solid particle volume fraction and with smaller particle size. At the highest particle size, it is increased by about 14%. There is 7% variation in the average Nu number when cases with lowest and highest particle size are compared. Finally, convective heat transfer performance modeling with four inputs and one output is successfully obtained by using Adaptive Neuro-Fuzzy Interface System (ANFIS) which provides fast and accurate prediction results.

scholarly journals Blocks Size Frequency Distribution in the Enceladus Tiger Stripes Area: Implications on Their Formative Processes

Universe ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 82
Author(s):  
Maurizio Pajola ◽  
Alice Lucchetti ◽  
Lara Senter ◽  
Gabriele Cremonese
Keyword(s):  
Frequency Distribution ◽  
Power Law ◽  
Size Frequency Distribution ◽  
Surface Stresses ◽  
Size Frequency ◽  
The One ◽  
Power Law Index ◽  
Comet 67P ◽  
South Polar ◽  
Degree Of Fragmentation

We study the size frequency distribution of the blocks located in the deeply fractured, geologically active Enceladus South Polar Terrain with the aim to suggest their formative mechanisms. Through the Cassini ISS images, we identify ~17,000 blocks with sizes ranging from ~25 m to 366 m, and located at different distances from the Damascus, Baghdad and Cairo Sulci. On all counts and for both Damascus and Baghdad cases, the power-law fitting curve has an index that is similar to the one obtained on the deeply fractured, actively sublimating Hathor cliff on comet 67P/Churyumov-Gerasimenko, where several non-dislodged blocks are observed. This suggests that as for 67P, sublimation and surface stresses favor similar fractures development in the Enceladus icy matrix, hence resulting in comparable block disaggregation. A steeper power-law index for Cairo counts may suggest a higher degree of fragmentation, which could be the result of localized, stronger tectonic disruption of lithospheric ice. Eventually, we show that the smallest blocks identified are located from tens of m to 20–25 km from the Sulci fissures, while the largest blocks are found closer to the tiger stripes. This result supports the ejection hypothesis mechanism as the possible source of blocks.

scholarly journals Impact of autocatalytic chemical reaction in an Ostwald-de-Waele nanofluid flow past a rotating disk with heterogeneous catalysis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bai Yu ◽  
Muhammad Ramzan ◽  
Saima Riasat ◽  
Seifedine Kadry ◽  
Yu-Ming Chu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Differential Equations ◽  
Chemical Reaction ◽  
Power Law ◽  
Variable Thickness ◽  
Rotating Disk ◽  
Thermal Profile ◽  
Nanofluid Flow ◽  
Power Law Index

AbstractThe nanofluids owing to their alluring attributes like enhanced thermal conductivity and better heat transfer characteristics have a vast variety of applications ranging from space technology to nuclear reactors etc. The present study highlights the Ostwald-de-Waele nanofluid flow past a rotating disk of variable thickness in a porous medium with a melting heat transfer phenomenon. The surface catalyzed reaction is added to the homogeneous-heterogeneous reaction that triggers the rate of the chemical reaction. The added feature of the variable thermal conductivity and the viscosity instead of their constant values also boosts the novelty of the undertaken problem. The modeled problem is erected in the form of a system of partial differential equations. Engaging similarity transformation, the set of ordinary differential equations are obtained. The coupled equations are numerically solved by using the bvp4c built-in MATLAB function. The drag coefficient and Nusselt number are plotted for arising parameters. The results revealed that increasing surface catalyzed parameter causes a decline in thermal profile more efficiently. Further, the power-law index is more influential than the variable thickness disk index. The numerical results show that variations in dimensionless thickness coefficient do not make any effect. However, increasing power-law index causing an upsurge in radial, axial, tangential, velocities, and thermal profile.

scholarly journals Influence of biopolymers on the rheological properties of seafloor sediments and the runout behavior of submarine debris flows

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jun Kameda ◽  
Hamada Yohei
Keyword(s):  
Rheological Properties ◽  
Debris Flows ◽  
Extracellular Polymeric Substances ◽  
Flow Behavior ◽  
Mass Movement ◽  
Rheological Parameters ◽  
Natural Environments ◽  
Natural Systems ◽  
Chemical Conditions ◽  
Seafloor Sediments

AbstractSubmarine debris flows are mass movement processes on the seafloor, and are geohazards for seafloor infrastructure such as pipelines, communication cables, and submarine structures. Understanding the generation and run-out behavior of submarine debris flows is thus critical for assessing the risk of such geohazards. The rheological properties of seafloor sediments are governed by factors including sediment composition, grain size, water content, and physico-chemical conditions. In addition, extracellular polymeric substances (EPS) generated by microorganisms can affect rheological properties in natural systems. Here we show that a small quantity of EPS (~ 0.1 wt%) can potentially increase slope stability and decrease the mobility of submarine debris flows by increasing the internal cohesion of seafloor sediment. Our experiments demonstrated that the flow behavior of sediment suspensions mixed with an analogue material of EPS (xanthan gum) can be described by a Herschel–Bulkley model, with the rheological parameters being modified progressively, but not monotonously, with increasing EPS content. Numerical modeling of debris flows demonstrated that the run-out distance markedly decreases if even 0.1 wt% of EPS is added. The addition of EPS can also enhance the resistivity of sediment to fluidization triggered by cyclic loading, by means of formation of an EPS network that binds sediment particles. These findings suggest that the presence of EPS in natural environments reduces the likelihood of submarine geohazards.

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