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Structure-Property Relationships for the Mechanical Behavior of Rubber-Graphene Nanocomposites
Published in Titash Mondal, Anil K. Bhowmick, Graphene-Rubber Nanocomposites, 2023
The resulting molecular structure brings about the various observed effects in rubber’s mechanical behavior. For example, Mullins effect involves cyclic stress softening, which results from the slipping or detachment of rubber molecules from the filler surfaces during the cyclic loading (Mullins 1969). A similar effect occurs at small strains and is referred to as the Payne effect caused by a different mechanism involving the disruption of aggregation of the filler particles (Payne 1963). However, in general, it is difficult to separate the effects of these two mechanisms. Since the original structure of rubber behaves like a viscous fluid, it is not surprising that the filled rubber also exhibits viscoelasticity (Ferry 1980). Rubber also exhibits temperature dependence in its mechanical response, and the effect of rising temperature can often be likened to that of increasing the strain rate (which in practice is termed as time temperature superposition). With this mechanistic understanding, a variety of constitutive models for rubber have been developed that can capture these effects and are used in practice for predicting the mechanical behavior and assisting the design of various engineering applications. The SPRs for rubber/graphene nanocomposites are best interpreted in the context of these behaviors.
Constitutive modelling of the amplitude and rate dependency of carbon black-filled SBR vulcanizate and its implementation into Abaqus
Published in Alexander Lion, Michael Johlitz, Constitutive Models for Rubber X, 2017
M. Fujikawa, N. Maeda, J. Yamabe, M. Koishi
Industrial rubbers are commonly used in tires and engine mounts and show nonlinear viscoelastic behavior. When designing such rubber components, it is important to capture its stress–strain response under arbitrary loading conditions. In general, the rubber materials exhibit linear viscoelastic behavior under small deformation, whereas they show nonlinear viscoelastic behavior under large deformation. Figure 1 shows the storage modulus, E′, loss modulus, E″, and loss tangential, tan δ, of a carbon black-filled styrene-butadiene rubber (SBR-CB) measured by a dynamic measurement tester (DMA). Because of the well-known Payne effect, these properties show remarkable nonlinearity, depending on the strain amplitude and strain rate. In addition, these tendencies also depend on the strain history and loading condition. From the practical importance, various nonlinear viscoelastic constitutive laws have been proposed so for; however, there are few models with a capability to reproduce both dynamic characteristics and various loading conditions (uniaxial tension (UT), pure shear (PS), and equibiaxial tension (BT)) under large deformations.
A constitutive law based on a dynamic strain amplitude dependent spectrum to model the Payne effect
Published in Bertrand Huneau, Jean-Benoit Le Cam, Yann Marco, Erwan Verron, Constitutive Models for Rubber XI, 2019
The classical way to exhibit the Payne effect on a filled elastomer is perform a DMA test, at one temperature, for one or two angular frequencies and for several dynamic strain amplitude values. The obtained decrease of the stiffness, previously mentioned, is displayed on Figure 1 for the studied silicon.
Filler flocculation in elastomer blends - an approach based on measured surface tensions and monte carlo simulation
Published in Soft Materials, 2019
Norman Gundlach, Reinhard Hentschke, Hossein Ali Karimi-Varzaneh
Elastomer materials for use in mechanically demanding products, e.g., car or truck tires, require reinforcement by filler particles. During the initial mixing stage in the materials production, these fillers, consisting of agglomerates of nano-particles, particles with a diameter on the order of 10 nm, are finely dispersed in the polymer matrix. The prevailing particle structures at this point are aggregates, which are not further broken down into the primary particles they are composed of. However, in the post mixing stages, like storage, extrusion or vulcanization, before the polymer network is fully established, these finely dispersed aggregates tend to re-agglomerate in a process called filler flocculation (1–5). The flocculation leads to the formation of a filler network, which determines, to a large extend, the dynamic mechanical properties of the elastomer material. Notably the filler network is responsible for the non-linear amplitude dependence of the dynamic moduli, the Payne effect (6,7). This effect is the overwhelming contributor to fuel consumption due to rolling resistance of vehicle tires. The Payne effect cannot be avoided, but it may be controlled and even usefully employed to enhance desirable properties, e.g., a tire’s grip. Control became more versatile when the tire industry introduced the so-called ’green tire technology’ roughly two decades ago, which meant that the filler system in the tread compounds for high-performance passenger car tires was changed from carbon black to silica (8). Compatibilization of rubber with silica, using sulphur containing silanes, led to a better filler dispersion during the mixing process, governed by the silane chemistry and its attendant influence on the interface tensions between the components.