Critical Fiber Length for Load Transfer in Carbon Nanotube (CNT) Reinforced Composites

Aerospace ◽  
2004 ◽  
Author(s):  
Feridun Delale ◽  
Huapei Wan
Keyword(s):  
Carbon Nanotube ◽  
Polymer Matrix ◽  
Fiber Length ◽  
Strain Energy ◽  
Load Transfer ◽  
Effective Properties ◽  
Critical Length ◽  
Polymeric Composite ◽  
Effective Moduli ◽  
The Matrix

In this paper the load transfer mechanism in a carbon nanotube (CNT) reinforced polymeric composite is considered. It is assumed that the polymer matrix is reinforced with single-walled carbon nanotubes and that the continuum model with adjustments is valid in estimating the effective properties of the composite. The existing studies contradict each other with respect to effective load transfer between the matrix and the nanotubes. In this study we show that there is a critical CNT length below which the load transfer is not effective. Thus for an effective load transfer the CNT length must exceed a critical length. To determine the critical length we consider a CNT embedded in a polymer matrix. The polymer/CNT interface is modeled as a distinct layer with elastic properties different than those of the CNT and the matrix. The strain energy change due to the inclusion of a CNT in a polymer matrix is then computed for various interphase stiffnesses using the finite element method. The variation of the strain energy per unit fiber length ΔU/L is plotted versus the aspect ratio of the CNT, L/D. It is observed that ΔU/L first increases steeply with L/D and then reaches a plateau. Since the region of constant ΔU/L is associated with uniform stress distribution, we define the critical CNT length as 90% of the asymptotic value of ΔU/L. It is shown that the load transfer is affected by the nature of the interphase. Next, using a dilute solution the effective moduli of the composite are derived for the cases of both hard and soft interphase. The results indicate that the nature of matrix/CNT interface affects the effective moduli of the composite only slightly.

Hierarchical Structure of a Natural Composite: Insect Cuticle

1991 ◽  
Vol 255 ◽  
Author(s):  
Stephen L. Gunderson ◽  
Katie E. Gunnison ◽  
John W. Sawvel
Keyword(s):  
Load Transfer ◽  
Natural Fiber ◽  
Polymeric Composite ◽  
Shear Stiffness ◽  
Insect Cuticle ◽  
Protein Matrix ◽  
Crosslinking Process ◽  
The Matrix ◽  
Improved Performance ◽  
Strength And Stiffness

AbstractThe insect cuticle is an excellent example of a natural, fiber-reinforced, polymeric composite consisting of chitin fibers embedded in a protein matrix. Optical and electron microscopy have been used to examine the structure and interaction of the constituents of the bessbeetle (Odontotaenius disjunctus) cuticle from the molecular to the macroscopic levels.Molecular chains of the polysaccharide chitin (N-acetylglucosamine) are grouped together to form “fibrils” which are either dispersed throughout the matrix or combined to form larger “fibers”. The fibers are unidirectionally oriented within individual sheets or laminae which are stacked on top of one another at various angles forming a laminated structure.The protein matrix is ductile upon initial deposition but then undergoes a crosslinking process which increases its shear stiffness, thereby improving load transfer between fibers. The matrix is bound to the chitin via beta linkages holding it together at both the fibril and fiber levels. The matrix has a fibrous morphology which provides adequate toughness in spite of the high degree of crosslinking.Reference is made to designs observed in the bessbeetle cuticle which could be applied to man-made composites for improved performance primarily in the areas of damage tolerance and strength and stiffness coupled with low weight. For these designs to be implemented using synthetic materials, new or modified processing and fabrication methods are needed.

scholarly journals Структурная трактовка изменения свойств нанокомпозитов полимер/углеродные нанотрубки у порога перколяции нанонаполнителя

2019 ◽  
Vol 89 (10) ◽  
pp. 1585
Author(s):  
Г.В. Козлов ◽  
И.В. Долбин
Keyword(s):  
Carbon Nanotube ◽  
Percolation Threshold ◽  
Polymer Matrix ◽  
Fractal Analysis ◽  
Formation Process ◽  
Structural State ◽  
The Matrix ◽  
Carbon Nanotube Network ◽  
Degree Of Reinforcement ◽  
Aggregation Level

AbstractThe structure of the nanofiller in the polymer matrix of polymer/carbon nanotube nanocomposites can be characterized by the dimension of the nanofiller network, which is a direct indicator of its aggregation level. The formation process of such a network is considered as a result of interaction of the matrix polymer and a carbon nanotube; which allows us to determine its dimension with the help of fractal analysis. It is found that the dimension of the carbon nanotube network changes both qualitatively and quantitatively at their percolation threshold, reflecting different aggregation levels. This dimension uniquely determines the degree of reinforcement of such nanocomposites and their structural state as a system.

Matrix laminate composites: Realizable approximations for the effective moduli of piezoelectric dispersions

1999 ◽  
Vol 14 (1) ◽  
pp. 49-63 ◽  
Author(s):  
L. V. Gibiansky ◽  
S. Torquato
Keyword(s):  
Effective Properties ◽  
Matrix Material ◽  
Transversely Isotropic ◽  
Effective Moduli ◽  
Phase Volume ◽  
Laminate Composites ◽  
Effective Coefficients ◽  
The Matrix ◽  
Axis Of Symmetry ◽  
Free Parameters

This paper is concerned with the effective piezoelectric moduli of a special class of dispersions called matrix laminates composites that are known to possess extremal elastic and dielectric moduli. It is assumed that the matrix material is an isotropic dielectric, and the inclusions and composites are transversely isotropic piezoelectrics that share the same axis of symmetry. The exact expressions for the effective coefficients of such structures are obtained. They can be used to approximate the effective properties of any transversely isotropic dispersion. The advantages of our approximations are that they are (i) realizable, i.e., correspond to specific microstructures; (ii) analytical and easy to compute even in nondegenerate cases; (iii) valid for the entire range of phase volume fractions; and (iv) characterized by two free parameters that allow one to “tune” the approximation and describe a variety of microstructures. The new approximations are compared with known ones.

Preparation of Electron Transparent Metal-Matrix Composites

1968 ◽  
Vol 26 ◽  
pp. 334-335 ◽  
Author(s):  
M. R. Pinnel ◽  
A. Lawley
Keyword(s):  
Stainless Steel ◽  
Load Transfer ◽  
Volume Fraction ◽  
Steel Wire ◽  
Initial Step ◽  
Interfacial Region ◽  
Matrix Composites ◽  
Specific Test ◽  
The Matrix ◽  
The One

Numerous phenomenological descriptions of the mechanical behavior of composite materials have been developed. There is now an urgent need to study and interpret deformation behavior, load transfer, and strain distribution, in terms of micromechanisms at the atomic level. One approach is to characterize dislocation substructure resulting from specific test conditions by the various techniques of transmission electron microscopy. The present paper describes a technique for the preparation of electron transparent composites of aluminum-stainless steel, such that examination of the matrix-fiber (wire), or interfacial region is possible. Dislocation substructures are currently under examination following tensile, compressive, and creep loading. The technique complements and extends the one other study in this area by Hancock.The composite examined was hot-pressed (argon atmosphere) 99.99% aluminum reinforced with 15% volume fraction stainless steel wire (0.006″ dia.).Foils were prepared so that the stainless steel wires run longitudinally in the plane of the specimen i.e. the electron beam is perpendicular to the axes of the wires. The initial step involves cutting slices ∼0.040″ in thickness on a diamond slitting wheel.

Deformation at interfaces of Ti-6Al-4V/SiC fiber composites

1992 ◽  
Vol 50 (1) ◽  
pp. 158-159
Author(s):  
Warren J. Moberly ◽  
Daniel B. Miracle ◽  
S. Krishnamurthy
Keyword(s):  
Thermal Stresses ◽  
Load Transfer ◽  
Coefficient Of Thermal Expansion ◽  
Hot Isostatic Pressing ◽  
Matrix Composites ◽  
Ongoing Research ◽  
Aerospace Applications ◽  
Sic Fiber ◽  
The Matrix ◽  
Intermetallic Matrix Composites

Titanium-aluminum alloy metal matrix composites (MMC) and Ti-Al intermetallic matrix composites (IMC), reinforced with continuous SCS6 SiC fibers are leading candidates for high temperature aerospace applications such as the National Aerospace Plane (NASP). The nature of deformation at fiber / matrix interfaces is characterized in this ongoing research. One major concern is the mismatch in coefficient of thermal expansion (CTE) between the Ti-based matrix and the SiC fiber. This can lead to thermal stresses upon cooling down from the temperature incurred during hot isostatic pressing (HIP), which are sufficient to cause yielding in the matrix, and/or lead to fatigue from the thermal cycling that will be incurred during application, A second concern is the load transfer, from fiber to matrix, that is required if/when fiber fracture occurs. In both cases the stresses in the matrix are most severe at the interlace.

Effect of temperature on matrix multicracking evolution of C/SiC fiber-reinforced ceramic-matrix composites

2020 ◽  
Vol 39 (1) ◽  
pp. 189-199
Author(s):  
Longbiao Li
Keyword(s):  
Strain Energy ◽  
Ceramic Matrix Composites ◽  
Critical Value ◽  
Matrix Cracking ◽  
Interface Debonding ◽  
Matrix Composites ◽  
Temperature Dependent ◽  
Damage State ◽  
The Matrix ◽  
Sic Composites

AbstractIn this paper, the temperature-dependent matrix multicracking evolution of carbon-fiber-reinforced silicon carbide ceramic-matrix composites (C/SiC CMCs) is investigated. The temperature-dependent composite microstress field is obtained by combining the shear-lag model and temperature-dependent material properties and damage models. The critical matrix strain energy criterion assumes that the strain energy in the matrix has a critical value. With increasing applied stress, when the matrix strain energy is higher than the critical value, more matrix cracks and interface debonding occur to dissipate the additional energy. Based on the composite damage state, the temperature-dependent matrix strain energy and its critical value are obtained. The relationships among applied stress, matrix cracking state, interface damage state, and environmental temperature are established. The effects of interfacial properties, material properties, and environmental temperature on temperature-dependent matrix multiple fracture evolution of C/SiC composites are analyzed. The experimental evolution of matrix multiple fracture and fraction of the interface debonding of C/SiC composites at elevated temperatures are predicted. When the interface shear stress increases, the debonding resistance at the interface increases, leading to the decrease of the debonding fraction at the interface, and the stress transfer capacity between the fiber and the matrix increases, leading to the higher first matrix cracking stress, saturation matrix cracking stress, and saturation matrix cracking density.

scholarly journals Supramolecular ionic polymer/carbon nanotube composite hydrogels with enhanced electromechanical performance

2020 ◽  
Vol 9 (1) ◽  
pp. 478-488 ◽  
Author(s):  
Yun-Fei Zhang ◽  
Fei-Peng Du ◽  
Ling Chen ◽  
Ka-Wai Yeung ◽  
Yuqing Dong ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Ion Mobility ◽  
Artificial Muscles ◽  
Ionic Polymer ◽  
Composite Hydrogels ◽  
The Matrix ◽  
Electromechanical Performance ◽  
Carbon Nanotube Composite ◽  
Robotic Devices

AbstractElectroactive hydrogels have received increasing attention due to the possibility of being used in biomimetics, such as for soft robotics and artificial muscles. However, the applications are hindered by the poor mechanical properties and slow response time. To address these issues, in this study, supramolecular ionic polymer–carbon nanotube (SIPC) composite hydrogels were fabricated via in situ free radical polymerization. The polymer matrix consisted of carbon nanotubes (CNTs), styrene sulfonic sodium (SSNa), β-cyclodextrin (β-CD)-grafted acrylamide, and ferrocene (Fc)-grafted acrylamide, with the incorporation of SSNa serving as the ionic source. On applying an external voltage, the ions accumulate on one side of the matrix, leading to localized swelling and bending of the structure. Therefore, a controllable and reversible actuation can be achieved by changing the applied voltage. The tensile strength of the SIPC was improved by over 300%, from 12 to 49 kPa, due to the reinforcement effect of the CNTs and the supramolecular host–guest interactions between the β-CD and Fc moieties. The inclusion of CNTs not only improved the tensile properties but also enhanced the ion mobility, which lead to a faster electromechanical response. The presented electro-responsive composite hydrogel shows a high potential for the development of robotic devices and soft smart components for sensing and actuating applications.

scholarly journals A mechanism for fire retardancy realized by a combination of biofillers and ammonium polyphosphate in various polymer systems

Cellulose ◽  
2021 ◽  
Author(s):  
Koki Matsumoto ◽  
Tatsuya Tanaka ◽  
Masahiro Sasada ◽  
Noriyuki Sano ◽  
Kenta Masuyama
Keyword(s):  
Polymer Matrix ◽  
Synergetic Effect ◽  
Polymer System ◽  
Ammonium Polyphosphate ◽  
Fire Retardancy ◽  
Polymer Systems ◽  
Thermal Decomposition Behavior ◽  
Burning Behavior ◽  
The Matrix ◽  
Decomposition Behavior

AbstractThis study focused on realizing fire retardancy for polymer composites by using a cellulosic biofiller and ammonium polyphosphate (APP). The motivation of this study was based on revealing the mechanism of the synergetic effect of a cellulosic biofiller and APP and determining the parameters required for achieving a V-0 rating in UL94 standard regardless of the kind of polymer system used. As for the polymer matrix, polypropylene and polylactic acid were used. The flammability, burning behavior and thermal decomposition behavior of the composites were investigated through a burning test according to the UL-94 standard, cone calorimetric test and thermogravimetric analysis. As a result, the incorporation of a high amount of cellulose enabled a V-0 rating to be achieved with only a small amount of APP despite the variation of the optimum cellulose loading between the matrix polymers. Through analysis, the results indicated that APP decreased the dehydration temperature of cellulose. Furthermore, APP promoted the generation of enough water as a nonflammable gas and formed enough char until the degradation of the polymer matrix was complete. The conditions required to achieve the V-0 rating were suggested against composites incorporating APP and biofillers. Furthermore, the suggested conditions were validated by using polyoxymethylene as a highly flammable polymer.

scholarly journals Comparison of the Dielectric Properties of Ecoflex® with L,D-Poly(Lactic Acid) or Polycaprolactone in the Presence of SWCN or 5CB

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1719
Author(s):  
Patryk Fryń ◽  
Sebastian Lalik ◽  
Natalia Górska ◽  
Agnieszka Iwan ◽  
Monika Marzec
Keyword(s):  
Oleic Acid ◽  
Dielectric Properties ◽  
Polymer Matrix ◽  
Liquid Crystalline ◽  
Weight Ratio ◽  
Poly Lactic Acid ◽  
Relaxation Processes ◽  
The Matrix ◽  
Walled Carbon Nanotubes ◽  
Hybrid Layers

The main goal of this paper was to study the dielectric properties of hybrid binary and ternary composites based on biodegradable polymer Ecoflex®, single walled carbon nanotubes (SWCN), and liquid crystalline 4′-pentyl-4-biphenylcarbonitrile (5CB) compound. The obtained results were compared with other created analogically to Ecoflex®, hybrid layers based on biodegradable polymers such as L,D-polylactide (L,D-PLA) and polycaprolactone (PCL). Frequency domain dielectric spectroscopy (FDDS) results were analyzed taking into consideration the amount of SWCN, frequency, and temperature. For pure Ecoflex®, two relaxation processes (α and β) were identified. It was shown that the SWCN admixture (in the weight ratio 10:0.01) did not change the properties of the Ecoflex® layer, while in the case of PCL and L,D-PLA, the layers became conductive. The dielectric constant increased with an increase in the content of SWCN in the Ecoflex® matrix and the conductive behavior was not visible, even for the greatest concentration (10:0.06 weight ratio). In the case of the Ecoflex® polymer matrix, the conduction relaxation process at a frequency ca. several kilohertz appeared and became stronger with an increase in the SWCN admixture in the matrix. Addition of oleic acid to the polymer matrix had a smaller effect on the increase in the dielectric response than the addition of liquid crystal 5CB. Fourier transform infrared (FTIR) results revealed that the molecular structure and chemical character of the Ecoflex® and PCL matrixes remained unchanged upon the addition of SWCN or 5CB in a weight ratio of 10:0.01 and 10:1, respectively, while molecular interactions appeared between L,D-PLA and 5CB. Moreover, adding oleic acid to pure Ecoflex® as well as the binary and ternary hybrid layers with SWCN and/or 5CB in a weight ratio of Ecoflex®:oleic acid equal to 10:0.3 did not have an influence on the chemical bonding of these materials.

scholarly journals The Influence of Filler Size and Crosslinking Degree of Polymers on Mullins Effect in Filled NR/BR Composites

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2284
Author(s):  
Miaomiao Qian ◽  
Bo Zou ◽  
Zhixiao Chen ◽  
Weimin Huang ◽  
Xiaofeng Wang ◽  
...  
Keyword(s):  
Particle Size ◽  
Strain Energy ◽  
Mathematical Expression ◽  
Rubber Matrix ◽  
Mullins Effect ◽  
Butadiene Rubber ◽  
Crosslinking Degree ◽  
Test Range ◽  
Two Factors ◽  
The Matrix

Two factors, the crosslinking degree of the matrix (ν) and the size of the filler (Sz), have significant impact on the Mullins effect of filled elastomers. Herein, the result. of the two factors on Mullins effect is systematically investigated by adjusting the crosslinking degree of the matrix via adding maleic anhydride into a rubber matrix and controlling the particle size of the filler via ball milling. The dissipation ratios (the ratio of energy dissipation to input strain energy) of different filled natural rubber/butadiene rubber (NR/BR) elastomer composites are evaluated as a function of the maximum strain in cyclic loading (εm). The dissipation ratios show a linear relationship with the increase of εm within the test range, and they depend on the composite composition (ν and Sz). With the increase of ν, the dissipation ratios decrease with similar slope, and this is compared with the dissipation ratios increase which more steeply with the increase in Sz. This is further confirmed through a simulation that composites with larger particle size show a higher strain energy density when the strain level increases from 25% to 35%. The characteristic dependence of the dissipation ratios on ν and Sz is expected to reflect the Mullins effect with mathematical expression to improve engineering performance or prevent failure of rubber products.

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