Multicoating Inhomogeneities Problem for Effective Viscoelastic Properties of Particulate Composite Materials

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Yao Koutsawa ◽  
Mohammed Cherkaoui ◽  
El Mostafa Daya
Keyword(s):  
Loss Modulus ◽  
Micromechanical Model ◽  
Polymer System ◽  
High Capacity ◽  
Viscoelastic Behavior ◽  
Particulate Composite ◽  
Micromechanical Modeling ◽  
High Loss ◽  
Wide Range ◽  
The Matrix

The present work extends the multicoated micromechanical model of Lipinski et al. (2006, “Micromechanical Modeling of an Arbitrary Ellipsoidal Multi-Coated Inclusion,” Philos. Mag., 86(10), pp. 1305–1326) in the quasistatic domain to compute the effective material moduli of a viscoelastic material containing multicoated spherical inclusions displaying elastic or viscoelastic behavior. Losses are taken into account by introducing the frequency-dependent complex stiffness tensors of the viscoelastic matrix and the multicoated inclusions. The advantage of the micromechanical model is that it is applicable to the case of nonspherical multicoated inclusions embedded in anisotropic materials. The numerical simulations indicate that with proper choice of material properties, it is possible to engineer multiphase polymer system to have a high-loss modulus (good energy dissipation characteristics) for a wide range of frequencies without substantially degrading the stiffness of the composite (storage modulus). The numerical analyses show also that with respect to the relative magnitudes of the loss factors and the storage moduli of the matrix, inclusion and coating, the overall properties of the viscoelastic particulate composite are dominated by the properties of the matrices in some frequency ranges. The model can thus be a suitable tool to explore a wide range of microstructures for the design of materials with high capacity to absorb acoustic and vibrational energies.

scholarly journals Research and Modeling of Viscoelastic Behavior of Elastomeric Nanocomposites

2021 ◽  
pp. 76-87
Author(s):  
V. D Kislitsyn ◽  
K. A Mokhireva ◽  
V. V Shadrin ◽  
A. L Svistkov
Keyword(s):  
Constitutive Relations ◽  
Viscoelastic Behavior ◽  
Polymer Materials ◽  
Material Structure ◽  
Softening Effect ◽  
Single Walled Nanotubes ◽  
Wide Range ◽  
Significant Difference ◽  
The Matrix ◽  
Entire History

The paper presents results of studying mechanical properties of polymer composites depending on types of filler particles (granular - carbon black, nanodiamonds; layered - graphene plates; fibrous - single-walled nanotubes). These nanofillers differ greatly from each other in their structure and geometry. A significant difference in behavior of nanocomposites was revealed even with little introduction of particles into the elastomer. The highest level of reinforcement of the matrix was obtained when single-wall nanotubes and detonation nanodiamonds were used as fillers. The viscoelastic properties and the Mullins softening effect [1-4] were investigated in experiments performed with material samples subjected to complex uniaxial cyclic deformation. In these experiments, the amplitude of deformations was changed step by step; and at each step a time delay was specified to complete rearrangement processes of the material structure. It was found that a pronounced softening effect after the first cycle of deformation and significant hysteresis losses occur in the material filled with single-walled nanotubes. These characteristics are insignificant for the rest of nanocomposites until elongation increases twofold. In accordance with the obtained results, a new version of the mathematical model to describe properties of the viscoelastic polymer materials was proposed. The constants of the constitutive relations were calculated for each material; the theoretical and experimental load curves were compared. As a result, the introduced model is able to describe the behavior of elastomeric nanocomposites with a high accuracy. Moreover, this model is relatively easy to use, suitable for a wide range of strain rates and stretch ratios and does not require the entire history of deformation as needed for integral models of viscoelasticity.

Micromechanical Modeling for the Damage Accumulation and Adhesive Wear of Metallic Materials Containing Inclusions

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Aizhong Wu ◽  
Lin Weng ◽  
Dingyu Hu ◽  
Aihua Liao
Keyword(s):  
Adhesive Wear ◽  
Shear Fracture ◽  
Micromechanical Model ◽  
Micromechanical Modeling ◽  
Metallic Materials ◽  
Contact Loading ◽  
Micro Cracks ◽  
Proposed Model ◽  
The Matrix ◽  
Model Crack

Abstract Metallic materials usually contain some amounts of inclusions which are known to affect their mechanical properties since the bonding strength of the matrix–inclusion interface is relatively low, voids or cracks are thus easily formed under a tensile loading. However, under a contact loading, the effects of subsurface inclusions on the sliding wear of metallic materials are not thoroughly understood. In this work, a micromechanical model is proposed to study the shear fracture and wear of metallic materials containing random inclusions. With the model, crack branching and crack aggregation during contact loading are simulated, and the formation process of sheet-like wear particles is clarified. It is demonstrated that the subsurface micro-cracks, particularly those near inclusions, and their subsequent evolution play a major role in the adhesive wear. This investigation is helpful in understanding the adhesive mechanism of wear, and the proposed model could be a promising approach for the prediction of adhesive wear.

scholarly journals Microrheology of DNA hydrogels

2018 ◽  
Vol 115 (32) ◽  
pp. 8137-8142 ◽  
Author(s):  
Zhongyang Xing ◽  
Alessio Caciagli ◽  
Tianyang Cao ◽  
Iliya Stoev ◽  
Mykolas Zupkauskas ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Melting Temperature ◽  
Loss Modulus ◽  
Viscoelastic Behavior ◽  
Building Blocks ◽  
Diffusing Wave Spectroscopy ◽  
Wide Range ◽  
Transient Network ◽  
Gel Transition ◽  
Dna Hydrogels

A key objective in DNA-based material science is understanding and precisely controlling the mechanical properties of DNA hydrogels. We perform microrheology measurements using diffusing wave spectroscopy (DWS) to investigate the viscoelastic behavior of a hydrogel made of Y-shaped DNA (Y-DNA) nanostars over a wide range of frequencies and temperatures. We observe a clear liquid-to-gel transition across the melting temperature region for which the Y-DNA bind to each other. Our measurements reveal a cross-over between the elastic G′(ω) and loss modulus G″(ω) around the melting temperature Tm of the DNA building blocks, which coincides with the systems percolation transition. This transition can be easily shifted in temperature by changing the DNA bond length between the Y shapes. Using bulk rheology as well, we further show that, by reducing the flexibility between the Y-DNA bonds, we can go from a semiflexible transient network to a more energy-driven hydrogel with higher elasticity while keeping the microstructure the same. This level of control in mechanical properties will facilitate the design of more sensitive molecular sensing tools and controlled release systems.

Rheology of aqueous boehmite-coated silicon nitride suspensions and gels

1995 ◽  
Vol 10 (11) ◽  
pp. 2808-2816 ◽  
Author(s):  
Wei-Heng Shih ◽  
Leh-Lii Pwu
Keyword(s):  
Silicon Nitride ◽  
Shear Modulus ◽  
Volume Fraction ◽  
Loss Modulus ◽  
Viscoelastic Behavior ◽  
Exponential Behavior ◽  
Shear Rates ◽  
Wide Range ◽  
Density Relationship ◽  
Bingham Yield Stress

The rheological properties of boehmite-coated silicon nitride aqueous suspensions and gels are reported. In unidirectional rheological tests, it was found that the boehmite coating reduces the viscosity of the suspensions over a wide range of shear rates and volume fractions of particles. The suspension shear stress as a function of shear rate can be described by the Bingham model, and the Bingham yield stresses of boehmite-coated silicon nitride suspensions are lower than those of the uncoated suspensions. The reduction in the viscosity and the Bingham yield stress is attributed to a shallower secondary minimum in the Derjaguin-Landau-Verwey-Overbeek (DLVO) potential between coated particles than that for uncoated silicon nitride particles. Moreover, at low values of pH, the coated silicon nitride suspensions gelled over time, and the viscoelastic behavior of the gels was studied by dynamic oscillatory tests. It was found that the shear modulus (G′) and loss modulus (G″) remain constant up to a certain strain amplitude, γ°, beyond which G′ and G″ begin to vary. The value of G′ in the linear region increases exponentially, whereas γ° decreases exponentially with the volume fraction of coated silicon nitride particles. The exponential behavior of the shear modulus G′ of the gels is similar to the exponential pressure-density relationship found in the previous pressure filtration study, indicating that particulate rearrangement occurs as volume fraction of particles is increased.

scholarly journals Creep Response of Neat and Carbon-Fiber-Reinforced PEEK and Epoxy Determined Using a Micromechanical Model

Symmetry ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 1680
Author(s):  
Mostafa Katouzian ◽  
Sorin Vlase
Keyword(s):  
Carbon Fiber ◽  
Matrix Material ◽  
Micromechanical Model ◽  
Viscoelastic Behavior ◽  
Experimental Tests ◽  
Fiber Reinforced ◽  
Element Analysis ◽  
Nonlinear Viscoelastic ◽  
The Matrix ◽  
Carbon Fiber Reinforced

A micromechanical model is developed to study the creep phenomena with neat and carbon-fiber-reinforced PEEK (Polyetheretherketon) and epoxy. The model considers that the continuous elastic circular fibers form a regular array inside the matrix material. In this study, the fibers are considered to be linear elastic and anisotropic, while the matrix has a nonlinear viscoelastic behavior. The approach describes the time-dependent response of unidirectional viscoelastic composites subjected to various types of loading conditions. A comparison between the finite element analysis and the proposed micromechanical model shows a good agreement. Experimental tests validate the results obtained using the proposed theoretical model.

Optimization of Damping Properties of Staggered Composites Through Microstructure Design

2018 ◽  
Vol 85 (10) ◽  
Author(s):  
Junjie Liu ◽  
Xusheng Hai ◽  
Wenqing Zhu ◽  
Xiaoding Wei
Keyword(s):  
Loss Factor ◽  
Loss Modulus ◽  
Low Frequency ◽  
Underlying Mechanism ◽  
Damping Properties ◽  
Microstructure Design ◽  
Element Analysis ◽  
Aspect Ratios ◽  
Wide Range ◽  
The Matrix

Many natural materials, such as shell and bone, exhibit extraordinary damping properties under dynamic outside excitations. To explore the underlying mechanism of these excellent performances, we carry out the shear-lag analysis on the unit cell in staggered composites. Accordingly, the viscoelastic properties of the composites, including the loss modulus, storage modulus, and loss factor, are derived. The damping properties (particularly, the loss modulus and loss factor) show an optimization with respect to the constituents' properties and morphology. The optimal scheme demands a proper selection of four key factors: the modulus ratio, the characteristic frequency of matrix, aspect ratios of tablets, and matrix. The optimal loss modulus is pointed out to saturate to an upper bound that is proportional to the elastic modulus of tablets when the viscosity of matrix increases. Furthermore, a loss factor even greater than one is achievable through microstructure design. Without the assumption of a uniform shear stress distribution in the matrix, the analysis and formulae reported herein are applicable for a wide range of reinforcement aspect ratios. Further, for low-frequency loading, we give practical formulae of the three indexes of damping properties. The model is verified by finite element analysis (FEA) and gives novel ideas for manufacturing high damping composites.

Influence of κ-Carrageenan, Modified Starch and Inulin Addition on Rheological and Sensory Properties of Non-fat and Non-added Sugar Dairy Dessert

2020 ◽  
Vol 16 (4) ◽  
pp. 462-469
Author(s):  
Zhaleh Sheidaei ◽  
Bahareh Sarmadi ◽  
Seyede M. Hosseini ◽  
Fardin Javanmardi ◽  
Kianoush Khosravi-Darani ◽  
...  
Keyword(s):  
Storage Modulus ◽  
Loss Modulus ◽  
Viscoelastic Behavior ◽  
Textural Properties ◽  
Complex Viscosity ◽  
Sensory Properties ◽  
Modified Starch ◽  
Consumer Health ◽  
Added Sugar ◽  
Textural Parameters

<P>Background: The high amounts of fat, sugar and calorie existing in dairy desserts can lead to increase the risk of health problems. Therefore, the development of functional and dietary forms of these products can help the consumer health. </P><P> Objective: This study aims to investigate the effects of &#954;-carrageenan, modified starch and inulin addition on rheological and sensory properties of non-fat and non-added sugar dairy dessert. </P><P> Methods: In order to determine the viscoelastic behavior of samples, oscillatory test was carried out and the values of storage modulus (G′), loss modulus (G″), loss angle tangent (tan &#948;) and complex viscosity (&#951;*) were measured. TPA test was used for analysis of the desserts’ texture and textural parameters of samples containing different concentrations of carrageenan, starch and inulin were calculated. </P><P> Results: All treatments showed a viscoelastic gel structure with the storage modulus higher than the loss modulus values. Increasing amounts of &#954;-carrageenan and modified starch caused an increase in G′ and G″ as well as &#951;* and a decrease in tan &#948;. Also, firmness and cohesiveness were enhanced. The trained panelists gave the highest score to the treatment with 0.1% &#954;-carrageenan, 2.5% starch and 5.5% inulin (sucralose as constant = 0.25%) and this sample was the best treatment with desirable attributes for the production of non-fat and non-added sugar dairy dessert. </P><P> Conclusion: It can be concluded that the concentration of &#954;-carrageenan and starch strongly influenced the rheological and textural properties of dairy desserts, whereas the inulin content had little effect on these attributes.</P>

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 Plasmonic semiconductor nanogroove array enhanced broad spectral band millimetre and terahertz wave detection

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Jinchao Tong ◽  
Fei Suo ◽  
Tianning Zhang ◽  
Zhiming Huang ◽  
Junhao Chu ◽  
...  
Keyword(s):  
Surface Plasmon ◽  
High Performance ◽  
Room Temperature ◽  
Spectral Band ◽  
High Capacity ◽  
Terahertz Wave ◽  
Semiconductor Surface ◽  
Wide Range ◽  
Low Sensitivity ◽  
Air Interfaces

AbstractHigh-performance uncooled millimetre and terahertz wave detectors are required as a building block for a wide range of applications. The state-of-the-art technologies, however, are plagued by low sensitivity, narrow spectral bandwidth, and complicated architecture. Here, we report semiconductor surface plasmon enhanced high-performance broadband millimetre and terahertz wave detectors which are based on nanogroove InSb array epitaxially grown on GaAs substrate for room temperature operation. By making a nanogroove array in the grown InSb layer, strong millimetre and terahertz wave surface plasmon polaritons can be generated at the InSb–air interfaces, which results in significant improvement in detecting performance. A noise equivalent power (NEP) of 2.2 × 10−14 W Hz−1/2 or a detectivity (D*) of 2.7 × 1012 cm Hz1/2 W−1 at 1.75 mm (0.171 THz) is achieved at room temperature. By lowering the temperature to the thermoelectric cooling available 200 K, the corresponding NEP and D* of the nanogroove device can be improved to 3.8 × 10−15 W Hz−1/2 and 1.6 × 1013 cm Hz1/2 W−1, respectively. In addition, such a single device can perform broad spectral band detection from 0.9 mm (0.330 THz) to 9.4 mm (0.032 THz). Fast responses of 3.5 µs and 780 ns are achieved at room temperature and 200 K, respectively. Such high-performance millimetre and terahertz wave photodetectors are useful for wide applications such as high capacity communications, walk-through security, biological diagnosis, spectroscopy, and remote sensing. In addition, the integration of plasmonic semiconductor nanostructures paves a way for realizing high performance and multifunctional long-wavelength optoelectrical devices.

scholarly journals Influence of Alumina Nanofibers Sintered by the Spark Plasma Method on Nickel Mechanical Properties

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 548 ◽  
Author(s):  
Leonid Agureev ◽  
Valeriy Kostikov ◽  
Zhanna Eremeeva ◽  
Svetlana Savushkina ◽  
Boris Ivanov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Elastic Modulus ◽  
Strength Properties ◽  
Alumina Nanoparticles ◽  
Metal Powders ◽  
Wide Range ◽  
The Matrix ◽  
Spark Plasma ◽  
Average Size

The article presents the study of alumina nanoparticles’ (nanofibers) concentration effect on the strength properties of pure nickel. The samples were obtained by spark plasma sintering of previously mechanically activated metal powders. The dependence of the grain size and the relative density of compacts on the number of nanofibers was investigated. It was found that with an increase in the concentration of nanofibers, the average size of the matrix particles decreased. The effects of the nanoparticle concentration (0.01–0.1 wt.%) on the elastic modulus and tensile strength were determined for materials at 25 °C, 400 °C, and 750 °C. It was shown that with an increase in the concentration of nanofibers, a 10–40% increase in the elastic modulus and ultimate tensile strength occurred. A comparison of the mechanical properties of nickel in a wide range of temperatures, obtained in this work with materials made by various technologies, is carried out. A description of nanofibers’ mechanisms of influence on the structure and mechanical properties of nickel is given. The possible impact of impurity phases on the properties of nickel is estimated. The tendency of changes in the mechanical properties of nickel, depending on the concentration of nanofibers, is shown.

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