Composites internal friction

In eq. (5.27) quantities JeR and [ ] are equal to those obtained by Zimm. According to Cerf, the internal friction factor ( ) can be determined by systematically varying solvent viscosity rj0, e.g. by changing the temperature of measurement or the composition of a mixed solvent. In this way, a straight line should be obtained for a plot of tan a vs. rj0. The positive intercept of this line with the ordinate axis should be equal to the second term on the right-hand side of eq. (5.27). An indispensible condition for this procedure is that the intrinsic viscosity [rj] is independent of the solvents used. Otherwise one should plot the product rf rj0 on the abscissa. 

On the chemical changes taking place m the inner oone, see Ubbelohde and Dommer, Chem. Zentr., 1914, n., 1370 On the variation of internal friction and connection with the composition of the gaseous mixture m the flame, see Becker, Ann. Physik, 1907, 24, 823. 

Grains of composition which contain water-soluble paste and have been shaped in the wet state e.g, cylindrical stars under low pressure or cut stars contain about 20a water. These crack when they are exposed to direct sunlight, except in the case of the smallest grains, i.e. less than about 5 mm in thickness. The cracking sometimes causes spontaneous ignition due to internal friction v/hen the compositions are sensitive. 

A. R. Boccaccini, C. B. Ponton and K. K. Chawla, Development and Healing of Matrix Microcracks in Fibre Reinforced Glass Matrix Composites Assessment by Internal Friction, Mat. Sci. Eng. A 241, 142-150 (1998). 

Tan 5 sometimes is referred to as internal friction or damping such as vibration or sound damping. It is the ratio of energy dissipated per cycle to the maximum potential energy stored dining a cycle. Tan 5 is also used to evaluate T of the samples (Lu et al. 2003). Figure 14 (c) dehneates the vibration of tan 5 of the control PU and FR-filled PU composites. 

The viscosity of a polymer solution is not only dependent on the molar mass, but also on the concentration, the solvent, the type and composition of the polymer solution fraction, the temperature and the pressure. The measurement of the viscosity, therefore, is not only for the practical and simple determination of a single product trait. Besides a simple single-point measurement and the quality control, viscosimetry allows for a much deeper insight into the flow properties of a polymer solution. The increase of the internal friction of a solution (the viscosity ) can be... 

DYNAMIC ELASTIC MODULUS AND INTERNAL FRICTION IN FIBROUS COMPOSITES... 

Anisotropic internal friction in composites has several possible causes ... 

For a sharp, Lorentzian resonance peak (as shown schematically in Fig. 2) the composite oscillator s internal friction, Qq, is... 

Table II, Dynamic Young s Modulus and Internal Friction of Several Fibrous Composites at Room Temperature... 

W. Fritz, W. Huttner, and G. Hartwig. . Dynamic Elastic Modulus and Internal Friction in Fibrous Composites... 

Fig. 71 Polystyrene the changes in resistance to deformation (a), energetic state (AH) and IR spectral characteristics as a function of pre-straining on compression at 20°C [15] (1) the stress-strain curve for annealed samples (2) ditto for quenched samples (3) enthalpy increment AH (DSC) (4) the extinction coefficient i602 of the IR band of deformation vibrations of the benzene rings at 1,602cm" as a measure of universal IMI (5) increment in mechanical loss (internal friction) A5ip (6) the ratio of optical densities of the IR bands at 560 and 542 cm" as a criteria of changes in the conformational composition...

Dynamic Mechanical Properties n (1) The stress-strain properties of a material when subjected to an applied sinusoidally varying stress or strain. For a perfectly elastic material the strain response is immediate and the stress and strain are in phase. For a viscous fluid, stress and strain are 90° out of phase. (2) The mechanical properties of composites as deformed under periodic forces such as dynamic modulus, loss modulus and mechanical damping or internal friction. (Sepe MP (1998) Dynamic mechanical analysis. Plastics Design Library, Norwich, New York)... 

Heat BuUdup and Compression Fatigue - Heat buildup in elastomers is the accumulation of thermal energy and resultant temperature increase in a rubber product due to internal friction when the product is subjected to repeated, rapid cychc deformation. The loss in properties of an elastomer due to heat buildup and other molecular effects of dynamic deformation is known as fatigue. Elastomeric compositions which show the least heat... 

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