Elastomer

A micromechanics framework for the development of continuum-level constitutive models for the large-strain deformation of porous hyperelastic materials is presented. A kinematically admissible deformation field is assumed which enables the derivation of a strain energy density function for the porous material. The strain energy density function depends on the properties of the incompressible hyperelastic matrix material, the initial level of porosity, and the macroscopic deformation. Differentiation of the strain energy density function, with respect to deformation, provides an expression for the stress–strain behavior of the porous hyperelastic material. Example calculations are carried out for porous hyperelastic materials with a Neo–Hookean matrix. The constitutive model is used to predict the stress–strain behavior of the pore-containing matrix as a function of initial porosity and macroscopic loading conditions. Predictions of the dependence of the small-strain elastic response on porosity are compared to various estimates of effective elastic moduli for porous materials found in the literature. Constitutive model predictions of the small to large-strain deformation behavior compare well with results from numerical three-dimensional micromechanical multi-void cell models.

The present research reports comparative analysis of effects of cold working (CW) and annealing on tensile and impact-toughness behavior of 7075 Al alloy. Cold-rolled samples were annealed at various temperatures in the range of 225-345 °C for 5 min. A remarkable increase in ductility and impact toughness was observed when specimens were annealed at temperatures above 265 °C for 5 min. It was also found that cold rolling has a profound effect on strength anisotropy that enhances with amount of % CW. The maximum strengths were observed in the transverse direction in the investigated alloy. Cold rolling has been found to impart a significant effect on decreasing the impact toughness of alloy that enhance with amount of % CW; this loss in impact energy could not be compensated by recrystallization process. It has also been shown that impact test can be considered as a simple method for measurement of toughness and plastic anisotropy in sheet and plate. The analysis of the fracture surfaces with the scanning electron microscope presented dimpled morphology for the failure ductile mechanism in starting material and fibrous structure with some quasi-cleavage regions in cold-rolled samples, corresponding to the ductile to brittle fracture mechanism. © 2009 Elsevier Ltd. All rights reserved.

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ABSTRACT Tyre Rubber Modified Binders (TR-MBs), produced through McDonald wet process and used worldwide (e.g. asphalt rubber), have been demonstrated to provide various benefits to pavements and, moreover, they represent a good opportunity for recycling tyre rubber. However this technology is still struggling to be fully adopted in Europe, mainly because of their poor stability during high temperatures storage, which leads to high initial costs in modifying existing asphalt plants. NO-agitation TR-MBs (also known as terminal blends) is proving to be a great option and its development could also be the key to spreading the recycling of tyre rubber in paving applications in Europe. This paper aims to enrich this field of research by presenting the results of a study focused on the optimisation of laboratory procedures to better understand the effect of varying processing conditions on the rheology TR-MBs. The experimental programme has been carried out by a preliminary selection of materials, followed by the production of the TR-MBs, via practical laboratory protocols. A continuous comparison between two commercially used SBS-MBs, with high and medium levels of modification, and the produced TR-MBs, helped to understand the effect of varying the selected processing conditions on binder properties. Results have shown that TR-MBs are a very effective alternative to commercially used SBS-MB. Although the rheology of TR-MBs is very sensitive to the varying of processing conditions, therefore an appropriate selection of materials and a superior binder design are mandatory to optimise the modification process to achieve the desired level of modification.

Addition of small amounts (0.5–10 vol%) of multiwall carbon nanotubes (CNT) to thermoplastic elastomer Morthane produced polymer nanocomposites with high electrical conductivity (σ∼1–10 S/cm), low electrical percolation (ϕ∼0.005) and enhancement of mechanical properties including increased modulus and yield stress without loss of the ability to stretch the elastomer above 1000% before rupture. In situ X-ray scattering during deformation indicated that these mechanical enhancements arise not only from the CNTs, but also from their impact on soft-segment crystallization. The deformation behavior after yielding of the nanocomposites, irrespective of CNT concentration, is similar to the unfilled elastomer, implying that the mechanistics of large deformation is mainly governed by the matrix. The relative enhancement of the Young's modulus of the nanocomposites is comparable to other elastomeric nanocomposites, implying that to the first order specific chemical details of the elastomeric system is unimportant.

Elastomeric bearings are design efficient and economical, hence widely used in
bridge construction worldwide. These bearings need reinforcement to restrict vertical
deformation which is generally provided in terms of steel plates. In present study,
mechanical property analysis on elastomeric bearing is carried by changing
materials of reinforcement. The results suggest that it is possible to produce the
strong and effective reinforced elastomeric bearing using material other than steel,
that matches the behavior of a steel-reinforced bearing. The study compares the
design of bearing reinforced using ASTM B22 and an optimized alloy with the
conventional steel laminates used for bearing reinforcement. The bearing used in the
case study is designed for the forces applicable to metro rail viaduct. The load
calculations are done according to the specification provided by BMRCL (Bangalore
Metro Rail Corporation Limited).

... Rubber World, : May, 25; 9. Rodriguez, EL 1988. Polym. Eng. Sci., 28: 1455 [CROSSREF] [CrossRef], [Web of Science ®]; 10. Tipana, M. and Kale, DD 1997. Rubb. Chem. Technol., 70: 815 [CrossRef], [Web of Science ®]; 11. Ismail, H., Nordin, R. and Noor, AM 2002. ...

Fiber-reinforced isolators not anchored to the structure represent a new development in seismic isolation. Their light weight, low cost and great ease of installation, in comparison with conventional elasto-meric isolators, could allow to extend the use of these valuable devices to seismic protection of housing and commercial buildings, particularly in developing countries. As demonstrated in studies available in the literature, fiber-reinforced isolators match the behavior of steel-reinforced ones. However the friction behavior between such new devices and the structure has not been investigated yet. This paper describes an experimental study on elastomeric isolators reinforced by bi-directional carbon fiber fabrics performed to investigate the static friction at contact surfaces. The isolators were placed in contact with concrete surfaces and subjected contemporaneously to compressive stress and shear strains. Friction behavior was analyzed in terms of isolator sliding with respect to the concrete sub-and superstructure. Influence on friction behavior of different parameters, such as level of compressive stress, rubber typol-ogy, concrete roughness, aging and loading rate, was investigated. The tests showed that, in relation to the value of the applied compressive stress, uncontrolled sliding of the isolator can occur by increasing the shear force. This unstable condition is called sliding instability herein. The experimental results are explained and the limit values of the compressive stress needed to avoid sliding instability is provided both for new and aged isolators, under quasi-static loading conditions. It is demonstrated that quasi-static tests are reasonably conservative with regard to safety. Patterns of stresses and relative displacements based on the experimental results are also proposed.

Polyphosphazenes elastomers have major utilization as fire resistant materials, gas kits, O-rings, electrical insulation, oil-resistant hoses, foam, ceramics, especially helicopter, air craft, aerospace, military and navy hardware applications. Tremendous achievements have been obtained for the synthesis and applications of polyphosphazenes. In this review, we highlighted the types, synthesis, characterization and applications of polyphosphazenes elastomers.

An overview of the chemistry and properties of silicone and related silicon-containing polymers is presented in the context of biomedical applications of silicones including both implantable and non-implantable medical devices. Implantable devices, contact lenses, skin scaffolding, LVADs among others are described. Keywords: Mammary Prosthesis, Artificial Heart, Snail in silicone, Oviductal Plugs, Interpenetrating Polymer Networks (IPNs)

Morphing wings are desired for their ability to reduce drag, to change flight characteristics, and perhaps to reduce weight by eliminating flap/aileron mechanisms. Development of two generations of a morphing wing project is documented. The work shows how a relatively low cost but realistic morphing wing test-bed can be fabricated. Wing skin, actuator, and actuator attachment development are discussed, as well as possible auxetic skin behavior. Aerodynamic characterization of the wing will be discussed in another paper. A very simple morphing wing was fabricated in generation one. The nose was able to elastically camber down approximately 25 deg and the tail 20 deg. Actuation was provided by three pneumatic “rubber muscle actuators” that produce high contractive/tensile forces. Upper and lower wing skins were fabricated from carbon fiber/polyurethane elastomer laminates. Lower skin buckling, actuator air leaks, and actuator attachment problems were resolved in the second generation....