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In finite element analysis of steel-reinforced elastomeric bearings (SREB) under compression, modeling of rubber as a nearly or fully incompressible material requires special attention. In this study, finite element simulations of circular elastomeric pads and rectangular SREB under compression were performed to analyze the effects of rubber compressibility with respect to different pad geometries and shape factor values. The ratio of the compressive modulus for a compressible rubber to that of an incompressible rubber was also introduced based on the previously derived exact solutions as well as the ad hoc approximations. This ratio accurately represents the influence of compressibility on compressive stiffness in terms of relative compressibility (K/G) and shape factor values. Numerical results were also compared with the experimental results on rectangular SREB with moderate shape factors. Recommended values for relative compressibility of carbon black-filled rubbers in the range of 50-200 result in underestimated compressive stiffness, especially for bearings with shape factor values greater than five. It is recommended to adjust the relative compressibility, considering the shape factor, so that the compressive stiffness does not decrease by more than 50% compared to the incompressible case. KEYWORDS bulk modulus, compressibility, compressive modulus, finite element analysis, rubber, shape factor, steel-reinforced elastomeric bearing, 1 | INTRODUCTION Elastomeric bearings allow displacement and rotation of individual parts of the supported structure by deformation of the elastomeric material, that is, rubber. Because of their relatively low [...]

A huge amount of rubber waste coming from tire industry or other sources (eg, weather strips producers) has attracted interest from researchers to investigate the possibility of recycling used rubber for various products, particularly in construction sector. This article presents a series of experimental and numerical investigations to evaluate the feasibility of regenerated synthetic rubber ethylene propylene diene monomer (EPDM) for production of a building seismic isolation system. Four rubber blends using two different sources of regenerated EPDM are considered in this study. The mechanical properties of the recycled rubber under study are evaluated through uniaxial tensile and relaxation tests, considering the accelerated aging effect. Based on several hyperelasticity and viscosity models of rubber available in the literature, several numerical test simulations on rubber compounds and on a prototype of fiber reinforced elastomeric isolators (FREIs) are performed. The test results reveal that the proposed regenerated EPDM compounds can be particularly suitable for the production of unbonded FREIs, especially because they are able to exhibit low/moderate tensile stresses at high-shear strain. The results also show that not all regenerated rubber blends fulfill the durability requirements of rubber for seismic isolation after accelerated aging tests. The durability of the specimens seems to be mainly affected by the choice of the regenerated rubber source. KEYWORDS aging effect, fiber reinforced elastomeric isolators, hyperelasticity, recycled rubber, regenerated EPDM, viscoelasticity, 1 | INTRODUCTION The use of rubber materials has been reported since the prehistoric era for household and industrial needs. [1] Rubber nowadays is widely used for tires, marine fenders, [...]

A new conducting blend from natural rubber (NR), low-density polyethylene (PE), and Bi-based superconductor (BSCCO) nanoparticles was successfully formulated. Blends were prepared by means of an open two-roll mill for five ratios (100/0, 90/10, 80/20, 70/30, and 60/40 NR/LDPE). The microstructures of the blends were examined in terms of scanning electron microscopy (SEM), bound rubber (BR), cross-linking density (CLD), and Mooney viscosity ([M.sub.100]). The mechanical properties like hardness (H) shore A, tensile strength (TS), and elongation at break (EB) of the blends were studied. The applicability of the blends as double thermistors, i.e., positive and negative coefficient of resistivity (PTCR/NTCR), was examined. The applicability of the blend for antistatic charge dissipation was also tested. Finally, electromagnetic interference response of conducting NR/PE-filled BSCCO in the frequency range 1-12 GHz has been studied. Shielding effectiveness of the conducting blends in the microwave range 8-12 GHz shows an attenuation of 44-60 dB for PE ≤10 wt%. POLYM. ENG. SCI., 49:592-601, 2009. ©2009 Society of Plastics Engineers, INTRODUCTION Incorporation of conductive fillers such as carbon black, graphite, metals, and others into a hosting polymer matrix constitutes a good approach for the development of special materials, which combine [...]

The study deals with the Payne effect (a substantial decrease in the storage modulus of a particle-reinforced elastomer with an increase in the amplitude of mechanical oscillations). The influence of temperature, concentration of filler and amplitude and frequency of strains is analyzed on the mechanical response of filled rubbery polymers. Constitutive equations are derived using the concept of two interpenetrating networks: one comprises semiflexible polymeric chains connected to temporary junctions, whereas the other is formed by filler clusters. Adjustable parameters are found by fitting experimental data for natural rubber, bromobutyl rubber and styrene-butadiene rubber reinforced by carbon black and polymeric particles. The critical concentration of particles is determined that characterizes transition from an ensemble of disjoint clusters to the network of filler. The volume fraction of filler corresponding to this transition is found to be close to the theoretical predictions based on the percolation theory, as well as to experimental data for isolator--conductor transition., 1 INTRODUCTION This paper is concerned with the Payne effect (1-4): a noticeable decrease in the storage modulus of filled rubbery polymers with an increase in the amplitude of small-strain [...]

Elastomeric (rubber-like) materials are extensively used in various machine design applications, particularly for flexible elements of vibration/shock/noise control devices and of power transmission couplings. In order to have high performance characteristics, such elements should accommodate large static and dynamic loads and/or large deflections in a limited size. In many applications high damping, low creep and substantial nonlinearity of the load-deflection characteristic are required. These contradictory requirements are often impossible to satisfy just by selecting special rubber blends. It was demonstrated in [9] that for unbonded rubber flexible elements of a cylindrical shape loaded in a radial direction, desirable nonlinear load-deflection characteristics can be naturally obtained, and creep rate can be significantly reduced as compared with conventional shapes of bonded rubber elements loaded in compression. This paper presents the second part of the study [9]. It applies the Finite Element Method to analyze large deformations of nonlinear components made of viscoelastic materials. Some convenient and efficient methods are proposed to determine material constants for the analytical study of static load-deflection characteristics and creep. These proposed methods result in good agreement between the numerical results and the experimental results in [9]

Fiber-reinforced elastomer offers abrasion resistance. A fiber-reinforced eiastomer for protecting underlying materials from erosion and/or fire has been developed by United Technologies Corp., Hartford, Conn. The material can be applied […]

The microstructures, mechanical properties, and fracture toughness of LCP (Vectra B950) reinforced PC/PBT blend with a 60/40 weight ratio have been studied. LCP of varying concentrations were investigated as rigid fillers in matrices of multi-phase polymer blends. In this study, differences in microstructures and morphology between samples of two thicknesses (4 mm thick and 6 mm thick) and two geometries (dumbbell and rectangular) were compared using scanning electron microscopy (SEM). Given identical processing conditions, fibrous LCP structures were evident in the 4-mm-thick injection molded, dumbbell-shaped samples, whereas the 6-mm-thick rectangular samples displayed spherical dispersion of LCP aggregates that embrittled the preblended ductile matrix. Tensile properties of the dumbbell specimens showed superior strengthening and stiffening whereby the tensile strength increased twofold and the modulus increased fourfold. Plane strain fracture toughness was slightly enhanced as the LCP content increased because of the fiber strengthening effect but the overall fracture performance of the in situ composites was relatively poor compared with PC/PBT. Experimental results were compared with those predicted in composite theory. Simplified micromechanics equations were developed to describe the tensile moduli of injection molded LCP reinforced blends that exhibited a strong skin-core morphology., INTRODUCTION Reinforcement of single polymer matrices by LCP has been studied extensively in the last decade (1-3). Results show that thermotropic LCP generally form in situ fibers in a polymer [...]