Dynamic mechanical properties of ZN-35 silicone rubber materials based on H-N model 

Tieneng Guo1,a，Yunchao Gu2,b，Shiming Ma3,c，Li Wang4,d

1Beijing University of Technology，Beijing 100124，China; 2Beijing University of Technology，Beijing 100124，China. 3Beijing University of Technology，Beijing 100124，China; 4Beijing University of Technology，Beijing 100124，China.

aguotn@163.com，bgycferrari@126.com，cmashiming@163.com，djiaoyuanwangli@163.com

Keywords：Viscoelastic damping material, temperature, frequency, energy storage modulus, loss factor, H-N model.

Abstract. ZN-35 silicone rubber is a kind of effective vibration damping material in aerospace, which can be made into a vibration damping pad for preventing vibration and damage to important components in the rocket. In this paper, the energy storage modulus and loss factor of ZN-35 silicone rubber materials at 11 different temperatures were tested by DMTA . The dynamic mechanical properties of the materials were analyzed at different temperatures. Finally, through the selection and fitting of data, the four parameters( ， ， 0E ， E ) of H-N model is determined. Meantime the H-N model curve is drawn. The dynamic mechanical properties of the materials are provided by using the H-N model, which provides the basic data for the use of vibration damping materials and the design of shock absorber.

1. Introduction

Damping material is a kind of vibration attenuation material, which can consume kinetic energy in the process of mechanical vibration, so that the resonance frequency of the structure can be reduced or transferred. Because of the damping of the material, the amplitude of the vibration is attenuated in the free vibration, and the amplitude of the response is suppressed or deformed in the forced vibration.

ZN-35 silicone rubber, which belongs to the viscoelastic damping material, has the following characteristics: (1) high temperature performance. in high temperature environment, silicone rubber can still maintain a certain degree of flexibility, resilience and surface hardness, and no significant changes in mechanical properties. (2) low temperature performance. The glass transition temperature of silicone rubber is generally -70-50 , the special formula can reach ℃ -100 , which ℃indicates that the low temperature performance is excellent. it is significant for the aviation and aerospace industry. (3) electrical performance. Silicone rubber has excellent insulation performance, resistance to corona resistance and strong arc resistance. So it is very important to apply ZN-35 silicone rubber materials in aviation field [1].

Pertinent literature about the dynamic mechanical properties of ZN-35 silicone rubber were not found. In this paper, the energy storage modulus and loss factor of ZN-35 silicone rubber were studied . Because of the limitation of the present test instrument, it is very difficult to obtain the dynamic mechanical properties of the materials in a wide frequency domain. [2] for practical application and theoretical research, as early as 1970s, the U.S. air force used the master curve method to expand the dynamic mechanical properties of a wider frequency range. This method has now become the national standard and ISO standard. However, this method can produce all kinds of errors in the process of data translation. Moreover, the parameters of the main curve obtained by this method have no physical meaning. H-N model overcomes the disadvantages of the

4th International Conference on Machinery, Materials and Computing Technology (ICMMCT 2016)

© 2016. The authors - Published by Atlantis Press 1074

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3.H-N model

The Havriliak-Negami equation is[5] * 0( )

[1 ( ) ]

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（1）

where *( )E w is the complex Young's modulus， 0E is the low frequency modulus，E is the high

frequency modulus，w is the angular frequency， is a parameter governing the width of the relaxation， is a parameter governing the asymmetry of the relaxation， is a relaxation time governing the position of the relaxation in the frequency domain,

* ' ''( )E w E iE （2） Solving for the real 'E and imaginary ''E , parts of Young's modulus respectively,

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（6）  

In this model it is assumed that the only temperature dependent parameter is the relaxation time and that only one polymer relaxation is involved. If there are multiple relaxation processes then a more complicated analysis or the use of more than one H-N equation is required. 

4.The Wicket plot

In order to reduce the errors caused by the improper operation of and the overload of the instrument, the test data should be selected to reduce the error The screening method is to draw the measured loss factor and the storage modulus data directly into the double logarithmic coordinates, that is, the Wicket plot. The Wicket plot is an extremely useful tool in analyzing dynamic viscoelastic data. The principle is that the storage modulus and loss factor are the only function of the conversion frequency for most amorphous polymers. Therefore, there must be a functional relationship between the energy storage modulus and the loss factor. It means that there is only one function relationship curve in the loss factor and the energy storage modulus. [6,7] No matter how the frequency and temperature of the test, all the valid data should be close to this curve, and those who are obviously deviate from the curve are questionable. The deviation data should be abandoned.

Fig.4 shows the original data Wicket plot for the ZN-35 silicone rubber material. Fig.5 shows the fitting data. It can be seen from figures, the original data dispersion is greater, there are obvious defect data. After screening, the data curve is smooth and continuous, which is convenient for the data fitting.

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