Prediction Of Viscoelastic Behavior Research Articles

An extension of the fractional model for construction of asphalt binder master curve

Knowledge and prediction of viscoelastic behaviour of asphalt binder is of great interest in order to design asphalt mixtures for civil construction of road and airports with good performances. The capability of a fractional model – requiring a very limited number of parameters – to describe and predict the linear viscoelastic behaviour of asphalt binder subjected to sinusoidal oscillations is investigated. Experimental data of complex modulus, |G*|, and phase angle, δ, are used to validate the proposed constitutive model. Based on the proposed extension of a fractional model, complex modulus isotherms for a range of frequencies can be created simply starting from isochronals at frequency value of 1 Hz. Furthermore, a mathematical procedure derived from the same model is proposed in order to compute the shift factors and automatically create the master curve, thus avoiding further errors due to manual adjustments. This shifting procedure requires only a few isotherms to create a smooth master curve able to describe asphalt binder behaviour under a wide range of temperature and loading conditions. When the fractional model is adopted and the mathematical shifting procedure is applied, only a temperature sweep test at 1 Hz is needed in order to create complex modulus and phase angle master curves.

Prediction of viscoelastic behaviour of polymer matrix composites based on polymer matrix

An effective micromechanics method of predicting the viscoelastic behaviour of polymer matrix composites based on a polymer matrix is presented. First, the Mori–Tanaka method is used to predict the elasticity properties of a unidirectional composite material from the matrix and reinforcement material. Then, the viscoelasticity of a layer in Laplace domain is obtained by the correspondence principle and the Laplace transform. The power law is used to model the polymer matrix's viscoelastic behaviour. Therefore, the inverse Laplace transformation can be used to obtain the viscoelasticity of a layer in the time domain. In the end, classic layer theories are adopted to predict the long-term viscoelastic properties of polymer matrix composites from a unidirectional composite material that is based on the viscoelastic properties of the polymer matrix. The mean relative deviation of the predicted results and experimental results for point 1 is 3·40% and for point 2 is 4·35% in 250 hours.

Prediction of viscoelastic behavior of interphase in polypropylene-chopped rice husk composites for β-relaxation domain

The effect of chopped rice husk (CRH) content on viscoelastic properties and crystallinity of polypropylene (PP) composites was investigated. Composites containing 0, 20, and 40 part per hundred plastics (php) of CRH into PP were prepared by twin-screw extruder, with maleic anhydride-grafted PP as the coupling agent. The viscoelastic behavior and the crystallinity of these composites have been studied by dynamic mechanical analysis as well as differential scanning calorimetry, respectively. By the incorporation of CRH into PP, the storage modulus (E′) was found to be increased progressively, whereas the mechanical loss factor (tan δ) decreased in a nonlinear manner. A self-consistent analysis was proposed for the prediction of viscoelastic response of the interphase between PP matrix and CRH particles. A three-phase model was applied in a reverse mode, and the viscoelastic behavior of the interphase was extracted and compared with the unfilled matrix. Differential scanning calorimetry results indicated that CRH influences crystallization temperature as well as the degree of crystallinity of the composites. An entrapped polymer within CRH filler and PP matrix was detected by scanning electron microscope, which can be attributed to the interfacial layer with a good adhesion between the main components. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Prediction of Viscoelastic Behaviour of Thermorheologically Complex Polymeric Materials

A simplified numerical computational technique based on a Gaussian spectral distribution model developed by Dutta and Edward [1] has been used to describe the stress relaxation behavior of polystyrene (PS) and isotactic polypropylene (iPP) over a wide range of time and temperature. An excellent fit between experimental data and the mathematical model is observed. The method may be applied generally for any linear viscoelastic property and for any polymer.

Towards realistic rheological models for polymer melt processing

AbstractGreatly needed improvements to rheological models of polymer fluids can best be made by understanding and modifying a model on the molecular level, where the physics governing real fluids are created. For this purpose, stochastic simulations are an indispensible tool. The usefulness of stochastic simulations for kinetic theory models are well‐known. In this paper, we show that the class of Rivlin‐Sawyers, or K‐BKZ, integral models is also subject to a molecular interpretation and can be simulated using stochastic techniques. We also illustrate how an existing molecular model can be modified, resulting in better predictions of viscoelastic behavior. For this we formulate a stochastic simulation of a reptation model modified to account for double reptation and tube‐length fluctuations.