scholarly journals Mori-Tanaka-based statistical methodology to compute the effective Young modulus of polymer matrix nano-composites considering the experimental quantification of nanotubes dispersion and alignment degree

2022 ◽  
Vol 10 (1) ◽  
pp. 79-98 ◽  
Author(s):  
Iván David Patiño ◽  
Cesar Augusto Isaza
Keyword(s):  
Polyvinyl Alcohol ◽  
Free Path ◽  
Orientation Angle ◽  
Young Modulus ◽  
Distribution Functions ◽  
Reinforced Composites ◽  
Statistical Methodology ◽  
Weight Content ◽  
Path Distance ◽  
Walled Cnts

This paper presents a Mori-Tanaka-based statistical methodology to predict the effective Young modulus of carbon nanotubes (CNTs)-reinforced composites considering three variables: weight content, reinforcement dispersion and orientation. Last two variables are quantified by two parameters, namely, free-path distance between nano-reinforcements and orientation angle regarding the loading direction. To validate the present methodology, samples of multi-walled CNTs (MWCNTs)-reinforced polyvinyl alcohol (PVA)-matrix composite were manufactured by mixing solution. The MWCNT/PVA Young modulus was measured by nano-indentation, while the MWCNTs Young modulus was quantified by micro-Raman spectroscopy. Both stretched and unstretched composite specimens were fabricated. Transmission electron microscopy (TEM) and in-plane image analysis were used to obtain fitting coefficients of log-normal frequency distribution functions for the free-path distance and orientation angle. It was evidenced that numerical results fit well to measured values of effective Young modulus of MWCNTs and MWCNT/PVA, with exception of some particular cases where significant differences were found. Microstructural heterogeneities, cluster formation, polymer chains alignment, errors associated with the dispersion, orientation and mechanical characterization procedures, as well as idealization and statistical errors, were identified as possible causes of these differences. Finally, using the proposed methodology and the dispersion and orientation distribution functions experimentally obtained, the effective Young modulus is estimated for three kinds of thermoplastic matrices (polyvinyl alcohol, polyethylene ketone, and ultra-high molecular weight polyethylene) with different kinds of nanotubes (single wall, double wall, and multi-walled), at different weight contents, finding the superior mechanical performance for double-walled CNTs-reinforced composites and the lower one for multi-walled CNTs-reinforced ones.

On the Overall Properties of Composites Reinforced by Fibers With Prescribed Orientations

2015 ◽  
Author(s):  
Yana Morenko ◽  
Pavlo Krokhmal ◽  
Olesya I. Zhupanska
Keyword(s):  
Uniform Distribution ◽  
Elastic Properties ◽  
Optimization Problem ◽  
Distribution Functions ◽  
Fiber Reinforced Composites ◽  
Semidefinite Optimization ◽  
Reinforced Composites ◽  
Fiber Reinforced ◽  
Positive Semidefinite Matrices ◽  
Orientational Distribution

This study is concerned with development of bounds on the elastic properties of fiber reinforced composites with arbitrary orientational distribution of fibers. Generalization of the Mori-Tanaka model [1] and Hashin-Schtrikman variational bounds [2] to the cases of non-aligned composite phases are examined. Orientation distribution functions (ODF) are used to describe orientation probability density. It is shown that the Mori-Tanaka scheme applied to the non-aligned fiber reinforced composites violates symmetry of the effective elastic moduli tensor. The study of the literature also reveals that there are no known bounds derived for the composites with orientational distribution (except for the random uniform distribution) of phases. To overcome this issue we propose to formulate a problem of finding tightest bounds for the composites with non-aligned phases as a nonlinear semidefinite optimization problem, i.e., an optimization problem where the optimization variables are represented by symmetric positive semidefinite matrices. Such a formulation guarantees that any solution of the optimization problem represents a valid tensor of elastic material properties. The optimization problem then is solved by an interior point method to produce optimal bounds for the overall elastic properties of two-phase composite with uniform distribution of carbon nanotubes in a polymer matrix.

Mechanical Properties of Functionalized Carbon Nanotube as Reinforcements

2012 ◽  
Vol 583 ◽  
pp. 22-26 ◽  
Author(s):  
Cui Cui Ling ◽  
Qing Zhong Xue ◽  
Xiao Yan Zhou
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Carbon Nanotube ◽  
Binding Energy ◽  
Functional Groups ◽  
Functional Group ◽  
Young Modulus ◽  
Electrostatic Energy ◽  
Walled Cnts

The effects of functional groups and degree of functionalization on the young modulus of carbon nanotubes (CNTs) are investigated through molecular dynamics and molecular mechanics simulations. It is found that young’s modulus depends greatly on the functional groups and degree of functionalization. The results show that the fluorine (-F) can replace the hydrogen, and young modulus of sing-walled CNTs (SWNT) modified by -F functional group can inherit the mechanical properties of intrinsic SWNT. The binding energy between functional groups and SWNT, and electrostatic energy among the functional groups are mainly responsible for these findings. These characteristics rival those of SWNT modified by hydrogen allow one to consider SWNT modified by -F functional group for a range of technologies, in particular require better inertness and stability than unachievable for the compound.

Physical, chemical, thermal, and mechanical assessments of Roselle-reinforced composites

2012 ◽  
Vol 32 (2) ◽  
Author(s):  
Ashish Chauhan ◽  
Balbir Singh
Keyword(s):  
Mechanical Strength ◽  
Moisture Absorption ◽  
Chemical Resistance ◽  
Phenol Formaldehyde ◽  
Graft Copolymers ◽  
Young Modulus ◽  
Hibiscus Sabdariffa ◽  
Reinforced Composites ◽  
High Mechanical Strength ◽  
Physicochemical Changes

Abstract Hibiscus sabdariffa stem fiber has 73.9% cellulose, high mechanical strength and is found in abundance throughout the world. Hibiscus sabdariffa graft copolymers were synthesized, characterized by FTIR, XRD, TGA, DTA, and SEM techniques, and evaluated for physicochemical changes in properties such as moisture absorption, chemical resistance against 1 n NaOH and 1 n HCl. These graft copolymers were reinforced in phenol-formaldehyde polymer matrix to form biocomposites that were characterized by advanced techniques and evaluated for physicochemicothermal resistance. The mechanical strength was accessed on the basis of hardness, flexural strength, Young modulus, and stress at the limit of proportionality, which was found to be high. These novel materials could have numerous scientific and industrial application to pave the way for development of technology.

scholarly journals Optimization of elasticity of unidirectionnal non-overlapping fiber reinforced materials

2019 ◽  
Vol 286 ◽  
pp. 03004
Author(s):  
L. Lakhal ◽  
Y. Brunet ◽  
T. Kanit
Keyword(s):  
Elastic Properties ◽  
Elastic Moduli ◽  
Volume Averaging ◽  
Distribution Functions ◽  
Fiber Reinforced Composites ◽  
Effective Elastic Moduli ◽  
Reinforced Composites ◽  
Fiber Reinforced ◽  
Fiber Reinforced Materials ◽  
Local Stresses

The aim of this work is to efficiently select samples of non-overlapping parallel fiber reinforced composites with regard to their elasticity and their fiber distribution in the composite cross-section. The samples were built with the help of the simulated annealing technique according to chosen Radial Distribution Functions. For each sample the fields of local stresses were simulated by finite element method, then homogenized by volume averaging in order to investigate their elastic properties. The effect of RDF shape on elastic properties was quantified. The more the fiber distributions deviate from Poisson’s Law the higher the effective elastic moduli are. A method to select samples of real fiber reinforced composites according to their elasticity is proposed.

scholarly journals Hi-Nicalon fiber-reinforced celsian matrix composites: Influence of interface modification

1998 ◽  
Vol 13 (6) ◽  
pp. 1530-1537 ◽  
Author(s):  
Narottam P. Bansal ◽  
Jeffrey I. Eldridge
Keyword(s):  
Fiber Strength ◽  
Mechanical Damage ◽  
Young Modulus ◽  
Matrix Cracking ◽  
Fiber Reinforced Composites ◽  
Matrix Composites ◽  
Reinforced Composites ◽  
Fiber Reinforced ◽  
Coated Fiber ◽  
Point Bend

Unidirectional celsian matrix composites having 42–45 vol% of uncoated or BN-SiC coated Hi-Nicalon fibers were tested in three-point bend at room temperature. The uncoated fiber-reinforced composites showed catastrophic failure with strength of 210 ± 35 MPa and a flat fracture surface. In contrast, composites reinforced with coated fibers exhibited graceful failure with extensive fiber pullout. Values of first matrix cracking stress and strain were 435 ± 35 MPa and 0.27 ± 0.01%, respectively, with ultimate strength as high as 960 MPa. The elastic Young modulus of the uncoated and coated fiber-reinforced composites were 184 ± 4 GPa and 165 ± 5 GPa, respectively. Fiber push-through tests and microscopic examination indicated no chemical reaction at the uncoated or coated fiber-matrix interface. The low strength of composite with uncoated fibers is due to degradation of the fiber strength from mechanical damage during processing. Because both the coated- and uncoated-fiber-reinforced composites exhibited weak interfaces, the beneficial effect of the BN-SiC dual layer is primarily the protection of fibers from mechanical damage during processing.

scholarly journals Cylindrical Polyurethane Scaffold Fabricated Using the Phase Inversion Method: Influence of Process Parameters on Scaffolds’ Morphology and Mechanical Properties

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2977
Author(s):  
Aleksandra Kuźmińska ◽  
Dominika Kwarta ◽  
Tomasz Ciach ◽  
Beata A. Butruk-Raszeja
Keyword(s):  
Mechanical Properties ◽  
Polyvinyl Alcohol ◽  
Polymer Solution ◽  
Process Parameters ◽  
Phase Inversion ◽  
Young Modulus ◽  
Process Time ◽  
Inversion Method ◽  
Influence Of Process Parameters ◽  
Phase Inversion Technique

This work presents a method of obtaining cylindrical polymer structures with a given diameter (approx. 5 mm) using the phase inversion technique. As part of the work, the influence of process parameters (polymer hardness, polymer solution concentration, the composition of the non-solvent solution, process time) on the scaffolds’ morphology was investigated. Additionally, the influence of the addition of porogen on the scaffold’s mechanical properties was analyzed. It has been shown that the use of a 20% polymer solution of medium hardness (ChronoFlex C45D) and carrying out the process for 24 h in 0:100 water/ethanol leads to the achievement of repeatable structures with adequate flexibility. Among the three types of porogens tested (NaCl, hexane, polyvinyl alcohol), the most favorable results were obtained for 10% polyvinyl alcohol (PVA). The addition of PVA increases the range of pore diameters and the value of the mean pore diameter (9.6 ± 3.2 vs. 15.2 ± 6.4) while reducing the elasticity of the structure (Young modulus = 3.6 ± 1.5 MPa vs. 9.7 ± 4.3 MPa).

scholarly journals Anisotropic Diffusion in Electron Swarms

1975 ◽  
Vol 28 (5) ◽  
pp. 533 ◽  
Author(s):  
JLA Francey ◽  
DA Jones
Keyword(s):  
Free Path ◽  
Diffusion Coefficients ◽  
Anisotropic Diffusion ◽  
Collision Frequency ◽  
Mean Free Path ◽  
Distribution Functions ◽  
Isotropic Diffusion ◽  
Electrostatic Fields ◽  
Frequency Interaction

We show that the distribution functions derived by Parker (1963) in his analysis of the TownsendHuxley experiment can be used to calculate DL/D, the ratio of longitudinal to isotropic diffusion coefficients for electron swarms in electrostatic fields in gases. In the case of a constant collision frequency interaction our results agree with previous calculations, whilst for a constant mean free path we find DL/D = 0�58. This result is some 16% higher than previously published values but provides better agreement with experiment for electrons in helium.

"Preparation and Study the Electrical Properties of Chitosan, Hydroxyethylcellulose, and Polyvinyl Alcohol polymer Blend Doped with Different ratios of 4-(2-Pyridylazo)Resorcinol Monosodium Salt Hydrate "

2020 ◽  
Vol 8 (1) ◽  
pp. 49-55
Author(s):  
Zainab J. Sweah ◽  
Fatima H. Malik
Keyword(s):  
Polyvinyl Alcohol ◽  
Polymer Blend ◽  
Young Modulus ◽  
Weight Percent ◽  
Hydroxyethyl Cellulose ◽  
Salt Hydrate ◽  
Ohmic Behavior ◽  
Current Voltage ◽  
Semiconductor Behavior ◽  
Monosodium Salt

"The polymer blend of Chitosan: polyvinyl alcohol (PVA) (1:1) weight percent and hydroxyethyl cellulose (HEC) (0.5%) was prepared. The profile of the sample and its properties were measured by Fourier transfer Infrared spectroscopy (FTIR). The Scanning Electron Microscopy (FESEM) was used to describe the morphology of the polymer blend with two magnifications without any ratio of 4- (2-Pyridylazo) resorcinol monosodium salt hydrate and with 0.15 % of a 4-(2-Pyridylazo) resorcinol monosodium salt hydrate. The mechanical properties were demonstrated and characterized by Elongation and Young modulus. The polymer blend was incorporated with different weight ratios of 4-(2-Pyridylazo) of resorcinol monosodium salt hydrate, (0.03, 0.05, 0.07, 0.09, 0.15) gm of weight %. The current-voltage (I-V) characterization of prepared thin films showed ohmic behavior and the electrical conductivity was improved by increasing the ratio of dopant that leads all samples to reflect a semiconductor behavior.

Clausius: the kinetic theory of gases

2020 ◽  
pp. 543-551
Author(s):  
Robert T. Hanlon
Keyword(s):  
Heat Capacity ◽  
Kinetic Theory ◽  
Free Path ◽  
Mean Free Path ◽  
Kinetic Theory Of Gases ◽  
Path Distance ◽  
The Mean ◽  
Monatomic Gas

Rudolf Clausius developed the first modern version of the kinetic theory of gases. His derivation provided the means to predict the heat capacity of a monatomic gas and to quantify the mean free path distance traveled by atoms between collisions.

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