Theoretical And Experimental Studies On The Viscoelasticity Of Carbon Black Filled Rubbers

Rubber-like materials are widely used in the fields of automotive engineering and aerospace as sealing and damping materials because of the superior mechanical properites.Although natural rubber has the property of high elasticity at the ambient temperature,it cannot satisfy the engineering requirements,such as the higher tensor strength and fatigue resistance.So,carbon black usually used to improve the mechanical properties in the rubber industry.On one hand,carbon black reinforced rubber has a more excellent performance.On the other hand,because of the viscoelasticity,the dynamic mechanical nonlinearity can be enhanced,such as hysteresis loss,stress softening and Payne effect.In this paper,a large amount of experimental study and theoretical analysis have been conducted.Besides,the selection strategies of classic viscoelastic and fractional derivative models,peak value of dynamic viscoelasticity,Payne effect,hysteriesis loss and self-heating have been discussed.Specific reseach contents are divided into the following five parts:1.The linear viscoelastic constitutive theory has been introduced simply and the suitability of the integral differential generalized viscoelastic models(the generalized Maxwell model and the generalized Kelvin model)and the fractional differential viscoelastic model(FDZ model)in the dicription of the static viscoelasticity and dynamic linear viscoelasticity has been discussed in detail.After the analysis and comparision of the mentioned models,the selection strategy of the viscoelastic constitutive model has been presented:(1)for the creep and stress relaxtion,the generalized models with five parameters are apt to be used to predict the static viscoelastic behaviors;(2)For short term or narrow frequency conditions,the generalized models with five parameters are selected to predict the viscoelastic behaviors;(3)while for widen frequency conditions,the fractional derivative models are more suitable,such as the ten-parameter FDZ model.2.By ues of the time-temperature superposition principle,the master curves of dynamic modulus and loss factor are constructed in widen frequency conditions.The results show that the dynamic modulus curves and loss factor curves at the condition of various temperatures can be shifted horizontaly into smooth master curves,which verify the carbon black filled rubber is a kind of thermorheological simple material.3.In the process of constructing the master curves,the asymmetry can be found.Based on the experimental results,the FDZ model was verified to be unsuitable to reproduce the dynamical viscoelastic behaviors.Therefore,a modified FDZ model by adding a spring-pot into the fractional Zener model is presented.The applicability of the modified FDZ model in describing the dynamic behavior of the CB-filled rubber is validated by the experimental results.4.In this paper,effects of temperatures ranging from-30? to 50? on the Payne effect and hysteresis loss of the CB filled rubber are investigated.The fitting results show that the storage modulus and loss modulus vs.strain amplitude curves at nine different temperatures can be shifted vertically along the logarithmic to get a single smooth one,and the temperature shift factor satisfies the WLF equation.This can provide an accelerated method to evaluate the Payne effect at any temperature based on just fewer test data.Moreover,according to the Kraus model and Payne effect test data,a method to predict the hysteresis loss of the material under different temperatures is developed and validated,and the results show that the method proposed in the paper can provide an accurate estimation of the hysteresis loss of CB filled rubber under cyclic loadings with various temperatures.5.Cylindrical carbon black(CB)filled rubber specimens were sinusoidally compressed with a Gabo Eplexor 500N dynamic mechanical analyzer,under various frequencies(10,30,50,70 and 90 Hz)and dynamic strain amplitudes(1%,2%,3%,4%and 5%).A ThermaCAM SC3000 infrared camera was used to capture the surface temperatures of the specimens.To predict the influence of two main influent factors(loading strain amplitude and frequency)on the heat build-up,the dynamic properties were updated as functions of the strain and frequency based on the Kraus and General Maxwell models,respectively.Combine with the heat equation,an analytical method for calculating the HBU was established.The comparison between the calculated results and experimental data shows that the proposed analysis method provides a satisfactory way to predict HBU for rubber compounds.