Papers by Keyword: Loss Factor

Abstract: The damping capacity improvement in under seawater for torpedo cone is the main of the research work. In the proposed work, an induction furnace was used to fabricate aluminum alloy AA7075 by melting individual elements such as pure Al, Zn, Mg, and Cu, followed by 10 wt.% graphite with varying sizes of reinforcement C1 (3 to 10μm), C2 (53 to 66μm), and C3 (106 to 150μm). Ingot casting was made in steel mold of 45 45 120mm³ and then hot forged at 490ᵒC, followed by solutionizing and artificial aging. Composites characterized for optical, SEM, hardness, and DMA analysis for loss factor. The improved performance in damping capacity by 50% observed for the threshold modulus of particulate (volume to the surface) for C2 composite. The processing cycle of fabrication of composites has been established.

Abstract: Nowadays, the usage of blowing agent in polyurethane preparation has been an essential enhance the characterization of polymers or composites material. The use of blowing agent may affect the properties of the materials and directly alter the performance of resulting product. In this paper, the effect of a blowing agent on dielectric properties of palm oil-based polyurethane (POlyOP) have been studied. The palm oil-based polyurethane ( POlyOP) has been prepared using the presence of water act as a blowing agent and tegostab 8486 act as a surfactant. The Oil Palm Empty Fruit Bunch (EFB) was used in the composite as filler. The dielectric constant and loss factor analysis in this study was carried out by Vector Network Analyzer (VNA) at x-band frequency using Nicholson-Ross-Weir (NRW) technique. The dielectric study of PolyOP composite showed that the presence of blowing agent in composite enhance the value of dielectric properties of composite at x-band frequencies.

Abstract: This study reports on the elaboration and characterization of bulk nanocomposites samples obtained by dispersion of metallic powders at the nanoscale as reinforcements in a polymer matrix. Elemental Fe powders were successfully nanostructured via high-energy ball milling. Structural characterization of the produced powders was conducted using X-Ray Diffraction (XRD) analysis and Scanning Electron Microscopy (SEM). The Halder-Wagner approach was adopted to determine the powder’s average grain size, internal strain, lattice parameters and the mixing factors. Structural parameters evolution and morphological changes according to milling progression are discussed. Bulk nanocomposites samples were shaped in a home moulder by dispersion of coarse Fe and nanostructured Fe powders in a continuous matrix of commercial epoxy resin. The obtained bulk samples match the metallic X-band wave-guide WR-90 dimensions used for electromagnetic characterization. The two-port S_ij scattering parameters were measured via an Agilent 8791 ES network analyzer. The measured scattering parameters served to calculate the loss factor of samples and to extract the dielectric permittivity via the Nicholson-Ross-Weir conversion. Spectra evolution of the scattering parameters, the loss factor and the dielectric constant for epoxy resin with coarse Fe and nanostructured Fe reinforcements are commented.

Abstract: The article deals with the problem of creating vibration damping polymeric materials with high damping properties in a wide temperature range. The purpose of the article is to study physical-mechanical properties of composites based on ethylene-vinyl acetate by adding various modifiers in the form of resins. The main method to investigate this problem is the method of dynamic mechanical analysis, which makes possible to obtain viscoelastic properties of polymeric materials under the influence of an oscillating load at various temperatures and oscillation frequencies. Due to the established experimental dependencies, the authors have determined the type of resin, which improves the damping properties and increases the stiffness of the composites based on ethylene-vinyl acetate. Moreover, the authors have defined the limit of working capacity of composites with resins at negative temperatures.

Abstract: To work out effective damping materials it is necessary to perfect analytical dependences linking dynamic properties of a composite with its structure-forming parameters. The analytical model of the particulate-filled polymers, based on the method of strain energy, convenient for engineering use and allowing to predict damping properties of a composite more reliable is given in this article. The detailed leading-out of formulas for scaling of a bulk modulus and loss factor of both two-phase and three-phase model of a composite is presented. Comparison of numerical values of damping characteristics under the derived formulas with experimental researches show that the offered model allows not only to show a qualitative pattern of dependence of dynamic behavior of a composite from degree of admission, but also to receive comprehensible quantitative results.

Abstract: This paper aims to investigate the damping properties of plate-like carbonyl iron particle (CIP) magnetorheological elastomer (MRE). The damping properties of MRE is mainly dependent on the strength of magnetic field. Anisotropic MRE was fabricated under various magnetic fields strength (70, 210, 345, and 482 mT) and its damping property prior to frequency-dependent was measured using a rheometer. Firstly, the plate-like CIP was first synthesized from spherical CIP using a ball-milling method. The microstructure of plate-like CIP was observed using low vacuum scanning electron microscope. Subsequently, two types of MREs which are isotropic and anisotropic were fabricated using 70 weight percent (wt.%) of plate-like CIP. The experimental results showed that the anisotropic MRE has lower damping factor than isotropic MRE. Meanwhile, the damping factor increases with the increase of frequency.

Abstract: A great deal of attention is presently being drawn to the question of noise and vibration damping. One of the basic means of the effective damping of unfavorable noises and vibrations is the usage of special sheets with high vibration and noise damping properties in thin-slab structures. In this article the results of a study of the dynamic behavior (of the loss factor) of multilayer vibration damping sheets are being described. The aim of this article is to show the design optimization of multilayer vibration damping sheets, carrying a high loss factor. The theoretical prerequisites for the structure optimization of vibration damping sheets, having a high loss factor, have been determined. The experimental studies on the influence of the thickness of the vibration damping layer, thickness and Young’s modulus of experimental with theoretical data have also been carried out. More effective designs of multilayer vibration damping sheets have been scientifically substantiated.

Abstract: Non-curing sealants have a complex composition consisting of a mixture of polymers, plasticizers, extenders, adhesive additives, various special purpose additives (pigments, biocides, fire-retardants), and therefore the optimization of their compositions to improve the physical and mechanical and technological characteristics is rather complicated. This article demonstrates the experimental results of physical and mechanical properties such as penetration, strength, density, adhesion to metal and concrete, water absorption, and elongation of sealants on the basis of butyl-rubber and EPDM, depending on filler type and volume. The basic regularities of the nature influence and fillers on the physical and mechanical and technological characteristics of sealants are revealed. We’ve identified the ultimate proportion of fillers when the sealants meet the required specifications. The research results are the recommendations on the selection and optimization of the filler content of the sealant composition.

Abstract: NDT impedance spectroscopy method was used to characterize a Cetris wood-cement chipboard. Dry specimen pre-stress and post-stress cycle tan δ (f) spectrum variances were observed. Effects of potential dielectric losses and the predominance of the polarization and conductivity components in various regions of the impedance spectrum of samples after frozen stress cycle are described. The method reproducibility has been verified by multiple measurements.

Abstract: Process time reduction and energy/cost savings are usually in the focus of production process improvements. New technologies provide possibilities to achieve significant enhancements for relevant operation figures.Curing cycle times for CFRP manufacturing depend on several requirements: Type of resin, requested glass transition temperature, used equipment and energy source as well as sample size, weight, fibre volume ratio, fibre orientation etc. Conventional methods are mostly based on heat conduction while microwaves offer a selective and volumetric heating of the samples. Process time reduction and energy saving are the positive effects of the microwave curing technology.This paper will give an overview of the current status of this process technology not only focussing on technical aspects but also covering the process and economic effects.This work has been performed under the German BMBF project 02PJ2131, FLAME under the program Energy Efficient Light Weight Construction.