Non-linear viscoelastic behavior

J.L. Leblanc, Investigating the non-linear viscoelastic behavior of filled mbber compounds through Fourier transform rheometry. Rubber Chem. TechnoL, 78, 54—75, 2005. 

The question whether ammonia treated wood shows linear or non-linear viscoelastic behavior has not been answered so far. 

N2 values are always lower than Nj values, see e.g. [40]. Therefore for many processes taking into consideration only Nj will suffice. The normal stress differences are independent of the direction of flow and, in laminar flow (low y), are proportional to y2. In following p = x/y for a Newtonian fluid, normal stress coefficients ipi = Nj/y2 and ip2 = N2/y2 are occasionally used. Their dependence on the shear rate i j(y) describes the non-linear viscoelastic behavior of the fluid. 

On a global scale, the linear viscoelastic behavior of the polymer chains in the nanocomposites, as detected by conventional rheometry, is dramatically altered when the chains are tethered to the surface of the silicate or are in close proximity to the silicate layers as in intercalated nanocomposites. Some of these systems show close analogies to other intrinsically anisotropic materials such as block copolymers and smectic liquid crystalline polymers and provide model systems to understand the dynamics of polymer brushes. Finally, the polymer melt-brushes exhibit intriguing non-linear viscoelastic behavior, which shows strainhardening with a characteric critical strain amplitude that is only a function of the interlayer distance. These results provide complementary information to that obtained for solution brushes using the SFA, and are attributed to chain stretching associated with the space-filling requirements of a melt brush. 

Theoretical calculations for llquld/llquid systems predict that the viscosity goes through a maximum at the spinodal. Depending on the type of system and its regularity, the increase may be quite large for example, Larson and Frederickson ( ) predicted that for block copolymers. These authors concluded that in the spinodal region a three-dimensional network is formed and that the system exhibits non-linear viscoelastic behavior. Experimentally, sharp Increases of n near the phase separation have been reported for low molar mass solutions as well as for oligomeric and polymeric mixtures (21). 

A. Damore, A. Pompo, P. Netti, E. Masi, and L. Nicolais. "Non-Linear viscoelastic behavior of poly-ether-ether-ketone (PEEK) and PEEK-based composites." Journal of Reinforced Plastics and Composites, pp. 327-340,1993. 

Gauthier Catherine, Reynaud Emmanuelle, Vassoille V. Rene, and Ladouce-Stelandre Laurence. Analysis of the non-linear viscoelastic behavior of silica fllled styrene butadiene rubber. Polymer. 45 no. 8 (2004) 2761-2771. 

A constitutive relationship between stress and strain describing viscoelastic behavior will have terms involving strain rate as well as stress and strain. If there is direct proportionality between the terms then the behavior is that of linear viscoelasticity described by a linear differential equation. Plastics may exhibit linearity but usually only at low strains. More commonly complex non-linear viscoelastic behavior is observed. 

As the first chapter of the book, the aim of this chapter is to give a brief introduction about the non linear viscoelastic behavior of mbber and its composites. The term viscoelasticity and stress softening usually observed in all elastomer systems are... 

This chapter focuses on the non-linear viscoelastic behavior of rubber composites and nanocomposites. Here, we have discussed about the effect of individual fillers (mineral fillers, nanotubes, carbon nanofillers, fibrous nanofiUers, biofillers, special structured fillers viz. nanorods, nanowires, nanoflowers etc.) on the linear/ nonlinear viscoelastic behavior of rubber composites. Moreover, as this chapter is more concerned on the non-linear viscoelastic behavior, we have also discussed the effect of hybrid fillers on the nonUnear viscoelastic behavior of rubber composites in more detail. 

Modeling of Non-Linear Viscoelastic Behavior of Filled Rubbers... 

Modeling of Non-Linear Viscoelastic Behavior of Filled Rubbers Table 3 Material models based on Rivlin s expansirai [115]... 

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