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Free Vibration and Damping Characterization of the Biocomposites
Published in Senthil Muthu Kumar Thiagamani, Md Enamul Hoque, Senthilkumar Krishnasamy, Chandrasekar Muthukumar, Suchart Siengchin, Vibration and Damping Behavior of Biocomposites, 2022
The other prominent testing parameters under dynamic analysis are dynamic modulus, storage modulus (E′), loss modulus (E″), damping efficiency or loss factor (tan δ), and logarithmic decrement (δ). The dynamic modulus represents the stress–strain ratio under vibratory conditions (free or forced vibrations). The storage modulus gives details about the amount of structure that has the capacity to store the input mechanical energy in a material. The storage modulus, which reflects the composite structure’s elastic properties, generally show a decrease in values as the temperature rises. The loss modulus represents the viscous properties of a material. It determines the flow material under deformation and the amount of energy lost or heat dissipated in one cycle. Tan δ represents the conversion of vibration energy to heat, and thus, the energy dissipated per radian to the peak potential energy is the cycle. δ represents the natural logarithm of the rate of decrement of any two successive amplitudes under free damped vibration. The study of controlling vibration has made researchers explore new composite viscoelastic and other polymeric materials owing to their high loss factor and high dissipation of energy and better damping capacity [15,16].
Dynamic Mechanical Thermal Analysis (DMTA) of Polylactic Acid (PLA)/Cellulose Composite
Published in Jyotishkumar Parameswaranpillai, Suchart Siengchin, Nisa V. Salim, Jinu Jacob George, Aiswarya Poulose, Polylactic Acid-Based Nanocellulose and Cellulose Composites, 2022
Sandeep Kumar, Georg Graninger, Brian G. Falzon
DMTA is a thermal analysis technique that measures the viscoelastic response of materials over a broad temperature range, as they are deformed under periodic stress (Menard, 2008). In DMTA, a sinusoidal deformation (stress(σ)) is applied, which results in a sinusoidal deformation (strain (ε)) under control temperature/or frequency program, as shown in Figure 8.1. DMTA measures stiffness and damping, which are reported as modulus and tan δ. Because we apply a sinusoidal stress, the response signal strain (ε) is split into two components. We express the storage modulus, E′, as an in-phase component and loss modulus, E″, as an out of phase component (Menard, 2008). The storage modulus provides a measure of elastic response/energy absorption ability of materials and as well as the molecular relaxation taking place as a function of temperature. The loss modulus represents the viscous response of a material and the amount of energy dissipated in a sample during one cyclic load. Tan δ is the ratio of loss modulus to storage modulus, E″/E′, and is often called damping. It is a measure of the energy dissipation of a material. a higher area under the tan δ peak suggests higher energy dissipation in the system. It is worth mentioning that the maximum tan δ peak occurs at the glass transition temperature of the polymeric material.
A Review on Dynamic Mechanical Properties of Polymer Nanocomposites
Published in Jose James, K.P. Pramoda, Sabu Thomas, Polymers and Multicomponent Polymeric Systems, 2019
T.A. Sajith, Azerai Ali Rahman, Zakiah Ahmad, Sabu Thomas
DMA gives more details regarding polymer composites because it consists of wide range of temperatures and frequencies that are not possible with other mechanical characterization techniques. All types of transitions and relaxation processes and the morphology of the polymer composites are sensitive to DMA analysis. The dynamic mechanical test provides three major parameters: (i) Storage modulus: it is the amount of the maximum energy stored in the polymer material during one cycle of oscillation. It also provides the information regarding the stiffness behavior and load-bearing capability of polymer material. The factors that depend on the storage modulus are polymer type, temperature, and frequency of oscillation. Furthermore, it is symbolized as the elastic modulus of the material. (ii) Loss modulus is the quantity of energy lost in one cycle in the form of heat. The internal molecular friction occurring during the viscous flow is the reason for heat energy dissipation. Additionally (iii) loss factor or damping factor (tan δ) is the ratio of the loss modulus and storage modulus and is associated to the degree of molecular motion in the composites. It is related to molecular movements, viscoelasticity, as well as certain imperfections that contribute toward damping such as dislocations, grain boundaries, phase boundaries, and various interfaces (Saba et al. 2016).
Design of peptide-PEG-Thiazole bound polypyrrole supramolecular assemblies for enhanced neuronal cell interactions
Published in Soft Materials, 2021
Sarah M. Broas, Ipsita A. Banerjee
Mechanical properties of scaffolds play a critical role in tissue engineering[65] with respect to cell attachment, differentiation, and[66] migration.[67] The optimal scaffold must provide ideal mechanical support for growing neurites with precise biological cues for axonal growth and promote regeneration.[68] We carried out rheological analysis of the assemblies before and after incorporation of PPy. The storage and loss moduli of the assemblies was first investigated (Figure 5). As shown in Figure 5A, for the Lam-PEG-Thiazole assemblies, both the storage and loss modulus increase as the angular frequency is increased; however, the loss modulus shows a linear pattern of increase. The storage modulus plateaus at an angular frequency range of 30 − 300 rad/s indicating that the texture becomes rubbery in that range followed by a steep increase. The rubbery behavior is attributed to the polydispersity of the assemblies.[69] The curves intersect when the frequency equals the reciprocal relaxation time. In general, storage modulus is indicative of the elastic portion of a material and is a measure of the resistance to oscillatory deformation[70] while the loss modulus represents viscous behavior. Thus at lower angular frequency, the assemblies are more elastic and display comparatively lower rotational freedom. At higher angular frequency the assemblies show viscous behavior and the energy is dissipated as heat due to movement of the assembly chain and motion of the assemblies.[71]
Static and dynamic mechanical analysis of hybrid composite reinforced with jute and sisal fibres
Published in Journal of the Chinese Advanced Materials Society, 2018
M. K. Gupta, Niraj Choudhary, Vandana Agrawal
Storage modulus obtained from dynamic mechanical analysis shows the stiffness of the materials. It can be described as maximum amount of energy absorbed by the materials during per cycle of oscillation. The variation of storage modulus with temperature of jute/sisal hybrid composites at 10 Hz frequency is shown in Figure 5. Storage modulus was improved due to incorporation of sisal fibres into jute fibre reinforced polyester composites. In the glassy region, increase in values of storage moduli follows the order: J25S75 > J50S50 > J75S25 >J0S100 > J100S0. The value of is mainly depends upon fibres-matrix bonding. Hybrid composite J25S75 had higher storage modulus owing to better interfacial bonding between fibres and matrix which gives uniform transfer of stress. In all cases, the storage moduli of the composites were seen to decrease as temperature increased. This could be due to lowering in stiffness of fibres at elevated temperature [14]. In transition region, it was seen that all the composites had a steady drop in values of with increase in temperature due to softening of the composites with increase in temperature. In rubbery region, the highest value of was found for hybrid composites J25S75. This fact shows that hybrid composite J25S75 was the stiffer composite materials than all other composites.
Damping behavior of Al/SiC functionally graded and metal matrix composites
Published in Journal of Asian Ceramic Societies, 2021
It is clear that the storage moduli of FGMs were higher compared to MMCs. Storage modulus is a sign of deformation energy that the material stores during loading. This means that storage modulus can be linked to elastic behavior (e.g. elastic modulus) of materials. Thus, higher storage modulus signifies stiffer behavior in materials. Since the FGMs have higher strength and stiffness compared to MMCs, higher storage modulus in FGMs compared to MMCs is an expected result.