Papers by Keyword: Loss Modulus

Abstract: In general, composite materials are widely used in many industries. A composite material is a material composed of two or more components. Such a composite material differs in its properties from the individual components of the entire composite. This contribution is aimed at evaluating the parameters of selected composite materials - wood fiber boards, carbon prepreg boards and epoxy boards. The measured quantities that were investigated on the given materials were the modulus of elasticity, the loss modulus and the tan delta angle. To evaluate the properties of the given composite materials, a dynamic-mechanical analysis using the DMA Q800 device from TA Instruments was used. Three samples were measured from each material. From the measured values, it is demonstrable for the modulus of elasticity that the greatest mechanical disturbance began to occur gradually due to the influence of temperature and frequency with three materials in this order: fiber board - carbon prepreg board - epoxy board. From the obtained values ​​of the loss modulus, it was proven that the sample - wood fiber board - had the lowest glass transition temperature. Finally, regarding the measured values ​​of the glass transition temperature for the loss angle (tan delta), it can be said that the wood fiber board also has the lowest damping ability.

Abstract: Fiber reinforced polymer composites made with glass fibers are among the oldest and most popular kinds of composites in use today. Glass fiber reinforced composites' key benefits are their adaptability for specific material applications, which allows them to give a number of design advantages relating to strength, chemical stability, impact damage tolerance, heat insulation, and low cost. The focus of this research is to investigate the role of hybridized ramie fibers in the assessment of enhanced vibrational damping capabilities in fiber glass reinforced composites, as well as in the initial assessment to verify their acceptability for real-time applications. Composite molding employing the hand layup technique was used to fabricate hybrid epoxy composites with ramie to glass fiber weight ratios from 0 to 50%. A free vibration test was performed to determine the hybrid composite's vibration dampening capabilities as a function of the ramie fiber filler content. The results demonstrated that the damping ratio was reduced when the percentage of ramie fiber in the GFRP composite was raised from 10% weight to about 50% weight. But adding up to 40% wt of ramie fiber to the hybrid composite had the biggest effect on the damping ratio, natural frequency, storage modulus, and loss modulus. This means that using ramie fiber in hybrid composites will be cost-effective and good for the environment.

Abstract: Damping properties are crucial in determining the dynamic structural response. In this paper, the experimental results for Neoprene rubber of 40, 50 and 60 shore A hardness are reported in view of improving structural damping to control noise and vibrations. Additionally, the system loss factors of the unconstrained layer damped structures of same material were predicted by Ross-Kerwin-Ungar equation to validate the obtained experimental results. The results showed that Neoprene rubber (also known as Polychloroprene) of 60 shore A showed better static and dynamic characteristics than those of the 40 and 50 shore A hardness. The system loss factor results reached the saturation when the applied viscoelastic layer thickness was increased from 40 mm to 50 mm in unconstrained damping. As such, the proposed method can help to build a database of the properties of various materials which are applicable in the design of noise and vibration control.

Abstract: The attractiveness of glass is something that occupied the world market with a unique claim. It has many applications that go beyond the provision of visual aesthetics, which includes a view of the inside and out. Due to extreme levels of clarity, structural glazing may be so transparent that it may go unnoticed by design or make a strong visual impact such as the focal point of a building. This paper focused on structural glass with various laminated/laminated conditions that were used to investigate the Dynamic Mechanical Properties. The storage modulus (G'), loss modulus (G'') and damping factor (tan delta) were determined at various levels, ranging from room temperature to elevated temperatures (250 °C) to understand the behavior of glass structure with and without laminated glass over a range of temperatures. The G' & G'' were tested to understand the effect of bonding, fracture behavior between the pure glass and laminated glass to observe the response with respect to temperature. Results are found that G' and G'' improve over a range of temperatures for laminated glass with enlightening fracture behavior. Laminated glass also has a major influence on the damping factor, but it also depends on the laminated thickness and materials. Thermo-Mechanical Properties of laminated glass are more improved, without affecting the transferability of glass.

Abstract: In this paper we report on investigation of the viscoelastic and rheological properties of early synthesized and characterized nanosuspensions by acoustical method, allowing to obtain the characteristic curves of shear elastic moduli and to assess the degree of "hardening" and structuring of the suspension. The paper is rising the question of fundamental problem - the structuring the nanosuspension, that might shed a light on the possibility of "engineering" the structure of a liquid by controlling and regulating the degree and nature of intermolecular interaction.

Abstract: A new fiber (x) reinforced Dynamic Covalent epoxy-polyurea Interface (x-DC_EPI) shows good mechanical energy transferability of impact and vibration forces. The bonding property of x-DC_EPI interface, engendered between curing, or reactive, epoxy and dynamic polyurea, is controlled by epoxy curing time (t_c). The reaction of curing epoxy, where t_c is a thermodynamic processing parameter, and fast-curing/ dynamic aliphatic polyurea, which lacks polyol in its resin chain extender, is linked to bulk mechanical energy transfer, quantified specifically via the loss modulus of x-DC_EPI. The parameter t_c effectuates designable chemical bond properties within x-DC_EPI. Using Generalized Maxwell models, viscoelastic properties of epoxy, polyurea, and x-DC_EPI are predicted, and results are verified using Dynamic Mechanical Analysis (DMA). The Maxwell models for x-DC_EPI, as a function of t_c, are used in a finite element analysis (ABAQUS) to control performance of dynamically loaded structures.

Abstract: Following the fundamental work by Bazaron, Bulgadaev and Derjaguin [6] on the observation of shear elasticity of low viscous liquids, we build on this study by examining viscous liquids, polymers and suspensions of nanoparticles. In this paper, we review our past and current efforts in these areas. The mechanical properties of liquids, polymers and nanosuspensions have been studied at relatively low frequencies of 10⁵ Hz. The real and imaginary shear moduli of these samples were obtained on equipment using the acoustic resonance technique. It was shown that the shear modulus and viscosity decreases with increasing shear deformation. The behavior of viscoelastic fluids near surfaces is similar to that of colloidal and polymer suspensions, suggesting that the liquid component is determined by the mechanical response of suspensions.

Abstract: The aim of this study is to investigate the effect of different carbon black structures towards heat build-up measurements and its dynamic properties such as tangent delta, loss modulus and storage modulus on the industrial rubber compounds containing Natural Rubber (NR) and Styrene Butadiene Rubber (SBR). Different carbon black structures were used and characterised with respect to their rheological and physical properties. Heat Build-up test is a testing procedure which is used to measure the rate of heat generated by the rubber vulcanisates when subjected to rapidly oscillating compressive stresses or strain under controlled conditions. It was found that NR compound containing low and high carbon black structures; N375 and N339 produced lower heat generation compared to NR/SBR blends that filled with the same type of carbon black fillers. It shows that NR with low and high carbon black structures exhibits low heat build-up (surface and intrinsic) with a balance of good traction and low rolling resistance for application in tyre.

Abstract: It was shown that fumed silica particles (FS), dispersed in polypropylene glycol (PPG), form shear thickening fluids (STF). PPGs with different molar mass were tested. The best combination of the properties (high viscosity, obtained at high shear rate) present the fluids composed of 7 nm FS and PPG 425. The highest volume fraction of FS, which was possible to disperse in PPG 425, was 25%. This fluid exhibited the highest viscosity. The highest magnitude of shear thickening effect was obtained, however, for 17.5 vol.% of the solid phase. Dynamic oscillatory shear experiments were conducted at either a constant amplitude or frequency. The constant strain amplitude tests showed, that for the frequency sweep, the systems showed viscous properties, except that of 25 vol.% of FS in PPG 425, which exhibited elastic properties in almost entire range of the frequency investigated. For the constant strain sweep, for low strains, the elastic modulus and loss modulus were hardly dependent on the strain, but for relatively high strain, this dependency was increasing. Also the complex viscosity was also growing for high strain values.

Abstract: Epoxy resin nanocomposite samples containing 0~3wt.% reactive diluent and 0~3wt.% silica nanopowder are prepared. The preparation process is presented for solvent-free and greenmanufacturing. The storage modulus, loss modulus and glass transition temperature of the various samples are then evaluated via Dynamic Mechanical Analysis (DMA). For samples containing 0wt.% and 3wt.% reactive diluent, respectively, 3wt.% nanoSiO₂ addition is found to increase the storage modulus by 51.06 % and 22.22 %, respectively. In addition, it is found that the loss modulus is determined principally by the level of SiO₂ addition, whereas the glass transition temperature is determined mainly by the level of reactive diluent addition.