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Influence of Fiber Treatment on the Damping Performance of Plant Fiber Composites
Published in Senthil Muthu Kumar Thiagamani, Md Enamul Hoque, Senthilkumar Krishnasamy, Chandrasekar Muthukumar, Suchart Siengchin, Vibration and Damping Behavior of Biocomposites, 2022
Polymers also act like viscoelastic materials and exhibit high loss factors than conventional metals (Chung 2001). Viscoelastic materials are inherently capable of dissipating vibration energy as heat energy under dynamic loadings (Jones 2001). The intrinsic damping of composite constituents is the primary source of damping of PFCs. The viscoelastic nature of polymers contributes substantially to the damping of polymeric composites. Thermoplastics have higher energy dissipation capacity relative to thermosets, while the latter are usually selected for their better mechanical properties, strong chemical bond formation capability with various substates/surfaces, and excellent dimensional stability. An increase in viscoelastic polymers improves PFCs damping, but this has a detrimental effect on the mechanical properties (i.e., stiffness and strength) (Rahman, Mace, and Jayaraman 2016, Rahman, Jayaraman, and Mace 2017, 2018). Viscoelastic materials can retain and dissipate mechanical energy at the same time because of the existence of their long molecular chains (Richards and Lenzi 1984). Restoration of molecular chains results in damping following deformation (Darabi 2013). The loss factor of polymers is highly dependent on temperature and frequency because of their direct interaction between temperature and molecular movement. Plant fibers can be embedded into the viscoelastic materials (e.g., polymers), which can offer beneficial properties including damping, stiffness, strength, thermal stability, durability, and so on over the chosen ranges of temperature and frequency (Nashif, Jones, and Henderson 1985).
Mathematical Modeling and Analysis of Soft Tissue Viscoelasticity and Dielectric Relaxation
Published in A. Bakiya, K. Kamalanand, R. L. J. De Britto, Mechano-Electric Correlations in the Human Physiological System, 2021
A. Bakiya, K. Kamalanand, R. L. J. De Britto
In general, soft tissues are viscoelastic and anisotropic. Elasticity can be classified into three types: Elastic materials: Elastic materials have a tendency to return to their original shape after applied forces are removed. Such materials are represented using a Hookean spring.Viscoelastic materials: Viscoelastic materials demonstrate both viscous as well as elastic characteristics when subjected to deformation due to stress. Such materials are represented using a combination of Hookean springs and Newtonian dashpots.Hyperelastic materials: These materials, unlike true elastic materials, do not have linear stress–strain relationships. Such materials are characterized by their non-linear stress–strain behavior.
Nanoindentation of Soft Tissues and Other Biological Materials
Published in Michelle L. Oyen, Handbook of Nanoindentation with biological applications, 2019
Load-relaxation (or stress-relaxation) tests are frequently used to characterize the mechanical properties of cartilage samples using indentation.10,11 In a load-relaxation test, a displacement is applied to the cartilage surface using the indenter tip. While maintaining the same displacement, the force (or load) on the tip is monitored. In viscoelastic materials, the load tends to decrease with time under a constant displacement, a phenomenon referred to as relaxation. Eventually, usually after minutes or hours, equilibrium is reached and the load stabilizes. Depending on the assumed material model used to interpret the load-relaxation results, elastic, viscoelastic or biphasic poroelatic properties can be measured from this indentation test.10,12–15
How complex viscoelastic behaviors within a viscoelastic three-layer structure affect the measurement accuracy of ultrasound viscoelastic creep imaging
Published in Mechanics of Advanced Materials and Structures, 2023
Biological tissues and biomaterials are viscoelastic in nature [1–3]. Such viscoelastic behaviors are due to solid components or structural matrices that exhibit viscoelastic behaviors, or the interaction between solid and fluid components (for example, the fluid flow through the solid matrix) within a material [4]. Materials that possess viscoelastic properties exhibit viscoelastic behaviors such as stress relaxation and creep [5, 6]. The viscoelastic properties of a material can be quantitatively evaluated by measuring and analyzing stress relaxation or creep behaviors [2, 7, 8]. Evaluation of the viscoelastic properties of a material can be valuable for biomedical and clinical applications. For example, the viscoelastic properties of tissues can be served as clinical biomarkers for diagnosing the severity of diseases and injuries, since the process of diseases and the occurrence of injuries can result in the changes in the composition, structure and viscoelastic properties of tissues [9]. In tissue engineering, the viscoelastic properties can be applied to quantitatively evaluate the functional status and quality of biomaterials [1, 7, 8].
Modified couple stress theory for wave propagation in viscoelastic sandwich microplates with FG-GPLRC core and piezoelectric face sheets as sensor and actuator
Published in Waves in Random and Complex Media, 2022
Mohammad Mosayyebi, Faramarz Ashenai Ghasemi, Mohammad Aghaee
Materials composed of a combination of viscous and elastic properties are viscoelastic. They are widely used in reducing and controlling various harmful behaviors of structures. One of the viscoelastic models, the Kelvin–Voigt model, is selected for simulating viscoelastic materials. Ren et al. [40] illustrated the vibration response of sandwich plates with viscoelastic core based on the Kirchhoff plate theory and HSDT. According to numerical results, changes in core thickness are directly related to the viscoelastic intensity. They showed that the reduction of viscoelastic intensity causes an increase in natural frequency. Kolahchi et al. [41] carried out the dynamic buckling of viscoelastic sandwich nanoplates located on orthotropic Visco Pasternak medium based on RZT with different boundary conditions. Moreover, the wave propagation problem of a thin plate composed of viscoelastic material under transient heating loud was solved by Li et al. [42]. Kundu et al. [43] discussed wave propagation of viscoelastic functionally graded material (FGM) plates resting on anisotropic foundations. It is shown that viscoelastic properties reduce the stiffness, and cause waste energy in the system. Consequently, it leads to a decrease in the phase velocity and frequency of structures.
Viscous loading effect on the transference of Love type waves In piezomagnetic layered structure
Published in Waves in Random and Complex Media, 2021
The study involving the theory of elasticity and viscoelasticity has always been of great interest. In 1965, Biot [4] gave the concept dealing with the elasticity and viscoelasticity of initially stressed solids and fluids. Viscosity characterizes the mechanical properties of liquid media in technological processes. Moreover, Viscoelastic materials exhibit both viscous and elastic characteristics while undergoing deformations. Due to these characteristics, such materials are of great use for researchers in several investigations. Some well-known examples of viscoelastic material include wood, human tissue, amorphous polymers and biopolymers at high temperatures. The liquids which follow Newton’s law of viscosity are Newtonian liquids. The viscous coefficient of Newtonian liquid depends only on temperature and is independent of shear rate. Examples of such liquids are water, honey and organic solvents.