The paper deals with its own oscillations of a rectangular rod with a cross section of a rectangular shape. The method of determining real part of Young's dynamic modulus and tangent of mechanical loss of samples in the form of rods of a number of polymer materials by means of resonant vibrating-reed method are proposed. Experimental setup, algorithm and software for determining the amplitude of the sample oscillations are developed. The accuracy of measurements was determined and a comparative analysis of results was performed with data obtained by other methods.
The use of fractal and percolation approaches to the metal-filled polymer systems enables to analyze processes of their structure formation. The main aim of research paper is to define structural parameters and mechanical properties of metal-filled polyurethane systems based on results of ultrasonic study using fractal analysis and percolation approach. Polyurethanes auxetics filled with particles of iron (Fe), molybdenum (Mo) and wolfram (W) with radius between 0.3-1.0 µm are investigated. Polyurethane composites with polymer matrix are made of thermoplastic polyurethane synthesized from 4.4′-Methylen diphenyl diisocyanate, 1.4-Butanediol and Poly(tetramethylene ether)glycol with molecular weight 1500. Metal-filled polymer systems are obtained with the help of hot-pressing in T-p mode just after the components were all mixed. The results of acoustic research of investigated metal-filled thermoplastic polyurethane systems with 52% vol. Fe, 48% vol. W, 43% vol. Mo have proven to be with negative Poisson's constant. Based on percolation cluster model of metal-filled polyurethane auxetics their fractal dimensions and percolation indexes are distinguished. Usage of fractal-percolation ap
Резонансним методом зсувних коливань вільного кінця закріпленого зразка на звукових частотах у широкому діапазоні температур проведено вимірювання дійсної частини динамічного модуля пружності та тангенса кута механічних втрат конструкційного полівінілхлориду. Показано, що для амплітуд резонансних максимумів послідовних мод коливань зразків існує лінійна залежність.
The paper presents experimental values of lateral and extension transmission ultrasonic waves speed and their absorbance coefficient obtained with the help of discrete immersed method in metal filled polymer auxetic samples with polyurethane matrix. Poisson’s ratio, real and imaginary parts of complex dynamic elastic modulus (Young’s modulus, shear modulus, bulk modulus) and mechanical losses tangent of angle for extension, lateral and bulk deformation have been calculated regarding paper’s results. Viscoelastic properties of polyurethane auxetic have been examined regarding different theoretical approaches. To support negative values of Poisson’s ratio, a filled polymer model with critical filler amount and auxetic deformation models have been used. Models structural characteristics for filled polyurethane auxetics have been defined. Systems modeling with solid bulky inclusions, that are able to absorb and to disseminate ultrasonic waves, enables to consider suchlike systems as complex density materials. It is shown that in certain ratio of wave parameters and environment structural and mechanical properties, resonance effects take place, regarding filler’s particles vibration as inclusions in general.
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