Elastomer Layer Research Articles

Head-worn, trimodal device to increase transcript accuracy in a voice recognition system and to process unvocalized speech

A voice recognition device and method allows position-stabilized capture of spoken sounds with great repeatability and accuracy. The voice recognition device may additionally provide two channels of lip movement information to supplement the usual audible speech component recognition system in selecting the proper pairing of data input to text output. The voice recognition device may provide a further channel of information about the speech generating motions via an ultrasonic injection of sound into the vocal cavity and subsequent decoding of the emitted sound after injection. The ultrasonic injection and decoding may also used to provide audible clues as to the unvoiced sound formed by speaking when the vocal cords are not energized. The ensemble of electronic equipment upon the bail band may be in microcircuit form, including placing the components on a copper layer polyimide flexible strip. The side camera and “other side” illuminator LED may be on thin copper polyimide strips attached to the main electronics ensemble, and a set of thin polyimide conductors would conduct power into the ensemble and the signals out of the ensemble through one of the bail band ends, into the ear piece and down the connector to the associated computer equipment and may also supply the power for the electronic ensemble. The electronic ensemble may be potted with a thin layer of elastomer, such as translucent silicone, and provide a moisture barrier and physical protection for the ensemble, while still offering a very light visual weight to the combination of the electronic ensemble and the bail band.

Neck retardation and enhanced energy absorption in metal–elastomer bilayers

Retardation of necking under biaxial stretching of bilayer plates comprised of an elastomer layer bonded to a metal layer is studied. Substantial increases in necking limits and consequent energy absorption can be achieved in metal–elastomer bilayers for both quasi-static and dynamic stretching. The phenomena is tied to the fact that under stretching the incremental modulus of the elastomer remains essentially unchanged, or increases, while the incremental modulus of the metal steadily decreases. The effective incremental modulus of the bilayer decreases with stretching but at a lower rate than the metal itself. Since necking instabilities are associated with an erosion of the incremental modulus, necking in the bilayer is delayed to larger strains. Although the strength of a bilayer having the same mass/area as an all-metal plate is reduced, it can nevertheless absorb more energy than the metal plate if the ratio of the elastomer modulus to metal yield stress is sufficiently large. The first part of the paper derives necking limits and energy absorption capacities for bilayers under quasi-static biaxial stretching. The second part of the paper analyses axisymmetric neck development in clamped circular bilayers subject to impulsive pressure loads. The ability of the bilayer to sustain intense impulses is compared to the performance of metal plates of the same material and total mass. Outstanding issues requiring further study are discussed.

Micromechanical analysis of an elastomer filled with particles organized in chain-like structure

Organization of iron filler particles inside an elastomer is obtained by curing the polymer in presence of a magnetic field. We have studied the effect of structuring the particles in chains on the quasistatic behavior in elongation in the absence of magnetic field. The effect of a coupling molecule between the surface of the particles and the elastomer is also analyzed. It is shown that the modulus of the first loading curve is strongly increased by structuring the particles, and also by the use of a coupling agent. Using an effective medium approach we well reproduce the experimental behavior of the elastic modulus and we deduce that a thick layer of elastomer is still present between the particles. A finite element calculation allows to distinguish between two modes of rupture at high strains, depending on the strength of the coupling between the particles and the matrix.

Design of end-plate connections with elastomeric intermediate layer

Goal of this paper is the development of analytical design rules for bolted end-plate connections with an elastomeric intermediate layer as thermal separation. The actual stress distribution is converted to an equivalent mean stress and an associated effective height. The geometry dependence of the design compressive stresses can be described using a form factor. A finite element model is developed for validating the design rules taking into account geometric and material nonlinearities like large deformations, creep processes or the frictional contact. A major conclusion that can be drawn from the finite element simulation is that compressive stresses decrease towards the edges leading to a stress concentration between the bolts. Investigations of the long-term behavior demonstrate that the influence of creeping processes on the stress distribution can be neglected. On the other hand, it can be shown that the moment–rotation characteristic is strongly dependent on the pre-load of the bolts and the elastomer thickness.

Hydrofoil Leading Edge Isolation for Vibration and Noise Reduction in Marine Systems

A technique for reducing the vibration and noise from hydrofoils subject to unsteady lift is examined experimentally. Since the unsteady lift is known to be concentrated in the leading edge vicinity, a single-stage vibration isolation mount is integrated into a hydrofoil near its leading edge to inhibit the leading edge-generated unsteady forces from being transmitted to the remainder of the foil and any structures coupled to it. A single layer of elastomer forms the mount and is used to isolate the leading 20% chord of the hydrofoil from the remainder of the structure. The hydrofoil is excited into vibration by turbulence from an upstream wake generator in a water tunnel facility. Compared to a nonisolated hydrofoil, vibration reductions up to 10dB in level are recorded on the portion of the hydrofoil isolated from the leading edge.

A two-dimensional finite element analysis of a shape memory alloy laminated compositeplate

The deflection and time response of shape memory alloy laminated composite plate arestudied using first order shear deformation theory. The composite plate consists of a thinlayer of shape memory alloy bonded to an elastomer layer. The governing equations of theplate are developed using the energy balance equations and a two-dimensional model ofthe shape memory alloy layer. The finite element is modeled with the first ordershear deformation theory and equivalent single layer assumptions. The model isvalidated by comparing the results of the displacements and time responses with theliterature. As a specific example, a cantilever composite plate is used for parametricstudies. The effect of material properties, electric input power, thickness, thermalconductivity and heat sink strength on deflection and time response is also investigated.

Otrzymywanie i wlasciwosci elastomerowych silikonowych warstw antyadhezyjnych na papierze i pergaminie

Hydrolytic polycondensation and catalytic equilibration methods were used for preparation of poly(dimethyl-co-methylvinyl)siloxanes (PMVS) Me3SiO(Me2SiO)m(MeViSiO)nSiMe3 and poly(dimethyl-co-methylhydro)siloxanes (PMHS) Me3Si(Me2SiO)k(MeHSiO)lSiMe3 differing in molecular weights so also in m and n values as well as k and l (Table 1-3). As a result of crosslinking of PMVS with PMHS, with use of commercial platinic catalysts (Table 4), thin layers of silicone elastomers on a paper or parchment were obtained. In the same way the comparative coatings of commercial silicones were prepared with use of catalysts produced by three leader companies (Table 5). The following properties of the coatings were investigated: basis weight, abrasion, migration of the components at room temperature and at temp. 70 oC and release force (showing the release properties) (Table 6 and 7). The coatings made of silicone elastomers prepared in our syntheses showed similar properties to the layers made of commercial products.

Vibration dampening material

A vibration reducing assembly including a flexible headgear and at least one panel of vibration reducing material secured to the flexible headgear. The at least one panel of vibration reducing material includes at least a first elastomer layer and a reinforcement layer comprising a high tensile strength fibrous material.

Modulation of Adhesion at Silicone Elastomer–Acrylic Adhesive Interface

ABSTRACT To characterize the role of small silica like nanoparticles (MQ resins) in the modulation of adhesion at polydimethyl siloxane (PDMS) elastomers–acrylic adhesive contacts, we have designed systems in which the roles of MQ resins in enhancing interactions at the interface and in increasing viscoelastic dissipations in the elastomer layer could be separated. First, the contact between elastomers with various MQ resin contents and PDMS layers made of densely grafted short chains has been investigated through Johnson–kendall–Roberts (JKR) tests, in order to characterize how the dissipations in the elastomer depend on the resin content. The same elastomers in contact with thin-surface-anchored acrylic layers were then tested through JKR tests to determine the role of enhanced interactions in the modulation of adhesion at the interface due to the resins. In these experiments, the thickness of the acrylic layer was kept small enough so that dissipations in the acrylic adhesive could be neglected. Both G 0, the adhesive strength at zero fracture velocity, and G ( V), the velocity-dependent fracture toughness, strongly depend on the MQ resin content and on the contact time, suggesting the progressive building of strong interactions between acrylic and elastomer chains.

Synergistically toughening high‐density polyethylene with calcium carbonate and elastomer

AbstractThe microstructure, impact strength, and rheological properties of blends consisting of high‐density polyethylene (HDPE) and maleated poly (ethylene‐octene) (POEg) and/or calcium carbonate (CaCO3) were investigated. The improvement of impact strength of HDPE/POEg was limited due to the high miscibility between them. The introduction of CaCO3 had a negative impact on the toughness of the matrix because of the poor interfacial adhesion. In ternary blends of HDPE/POEg/CaCO3, an elastomer layer was formed around CaCO3 particles due to the strong interaction between POEg and CaCO3, which improves the HDPE‐CaCO3 interfacial strength and the toughness of the blends. A significant enhancement of dynamic viscosity, storage modulus, and the low‐shear viscosity were observed as the results of the high miscibility of HDPE with POEg and strong interaction between POEg and CaCO3. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3213–3221, 2005

Design of Cotton Duck Bridge Bearing Pads

Bearings are used to support loads and accommodate movements in bridges. Cotton duck bearing pads (CDP) offer a versatile and economical solution for bearing design. The CDPs have closely spaced layers of elastomer and fabric which result in large compressive strength and strain capacities. However, the engineering response of CDP has not been well understood and CDP design provisions are incomplete because of this limited knowledge. To better establish the engineering response and develop improved design provisions, an extensive experimental research study was conducted. The experimental program modeled loads and deformations induced on a bridge bearing and included both static and dynamic loading regimes in compression, shear, and rotation. The primary study parameters included pad geometry, pad manufacturer, and stress and strain levels. The results indicate that CDPs have significant compressive stress and deformation capacities. Using the experimental results, design limits to control pad damage and quality assurance provisions are proposed to ensure adequate service during the lifetime of the bridge. Delamination of the top pad layers occurs after many cycles of repeated load or deformation and limits on the maximum stress, stress range, and uplift are proposed to limit this type of damage. Diagonal fracture occurs when a CDP is subjected to large strains. Strict maximum strain limits are proposed to prevent this failure mode. Finally, quality control provisions are proposed to ensure adequate engineering performance of the pads.

Finite-amplitude shear wave in pre-stressed thin elastomers

We examine the elastic shear waves generated in a thin pre-stressed elastomer layer that is sandwiched between two relatively thick steel plates and is subjected to an elastic shear wave traveling in one of the steel plates. The elastomer layer has been deformed in uni-axial strain in advance, producing in the layer very large axial and lateral compressive stresses of the order of its bulk modulus. Deformations of this kind are produced in the thin layer when the sandwich structure is impacted by another steel plate at an oblique angle. Our results are thus relevant to the analysis of such pressure-shear plate impact experiments.

Improving organic/electrode interface in organic light-emitting diodes by soft contact Iamination

Organic light-emitting diodes (OLEDs), with few exvceptions, are fabricated in the standard way of sequentially depositing active layers and elecrodes onto a substrate. The conventional devices have ‘a detrimental layer’ at the interface between the organic and the top metal electrode because evaporation results in metal in-diffusion and chemical disruption at the metal-organic interface, Here, a different approach is introduced to construct OLEDs: soft contact lamination (SCL) is based on thysical lamination of thin metal electrodes supported by an elastomeric layer against the electrolumnescent organic layer. Thei method produces spatially homogeneous, intimate contacts via van der Waals interaction between the metal and the organic, resulting in no chemical and physical damages to the organic. Devices fabricated by SCL are shown to have no detrimental layer and fewer luminescence-quenching channels than conventional devices that have evaporated top metal electrodes.

Nonlinear evolution of thin liquid films dewetting near soft elastomeric layers

The nonlinear evolution of thin liquid films dewetting near soft elastomeric layers is examined in this work. Evolution equations are derived by applying the lubrication approximation and assuming that van der Waals forces in the liquid cause the dewetting and that the solid can be described as a linear viscoelastic material. Two cases are examined: (i) a liquid layer resting on an elastomer bounded from below by a rigid substrate, and (ii) an elastomer overlying a thin liquid film bounded from below by a rigid substrate. Linear stability analysis is carried out to obtain asymptotic relations which are then compared against solutions of the full characteristic equations. In the liquid-on-solid case, numerical solutions of the evolution equations show that van der Waals forces cause thinning of the liquid film and thickening of the elastomeric solid beneath film depressions. Inclusion of a short-range repulsive force suggests that regular patterns may form in which ridges of fluid rest on depressions in the solid. In the solid-on-liquid case, the van der Waals forces cause the solid layer to break up before the liquid film can dewet. The results presented here support the idea that the dewetting of thin liquid films might be exploited to create topographically patterned surfaces on soft polymeric solids.

Vibration damping tape

A tape adapted to absorb and/or regulate vibration preferably includes a multi-layer material that may include a first elastomeric layer of vibration absorbing material which is substantially free of voids therein. A second elastomeric layer includes an aramid material therein and is disposed on the first elastomeric layer. The amramid material distributes vibration to facilitate vibration dampening. A third elastomeric layer disposed on the second elastomeric layer.

Magnetostriction and piezoresistivity in elastomers filled with magnetic particles

Magnetorheological elastomers consist in a dispersion of micron size (typically 1-5μm) magnetic particles inside an elastomer. During curing, the suspension is subjected to a strong magnetic field that creates an attractive force between particles in a direction parallel to the magnetic field, thus arranging the homogeneous dispersion in a chain-like structure. Once the polymer is cured, this unidirectional structure is kept. We shall present some results showing that the adaptive character of the material does not depend on the fact that particles are grafted to the matrix or not, but rather on the volume fraction of particles and above all on their organisation inside the matrix. In particular we shall see that, in addition to the change of modulus in the presence of a field, some very important magnetostrictive effect can also be observed in such composite. We explain this behaviour by the existence of a small layer of elastomer between the magnetic particles. In an other situation, with the use of nickel particles inside the elastomer, the gap between particles is much thinner and a small compression can change the resistivity of the sample by many orders of magnitude making it a very sensitive pressure sensor.

How Stretchable Can We Make Thin Metal Films?

AbstractThin metal films deposited on elastomeric substrates can remain electrically conducting at tensile strains up to ~∼00%. We recently used finite-element simulation to explore the rupture process of a metal film on an elastomer. The simulation predicted the highest stretchability on stiff elastomeric substrates [1]. We now report experiments designed to verify this prediction. A ∼15-μm thick silicone elastomer layer with Young's modulus E ∼ 160 MPa is deposited on a 1mm thick membrane of polydimethylsiloxane (PDMS), a silicone elastomer with E ∼3 MPa. Metal stripes consisting of 25-nm thick gold (Au) film sandwiched between two 5-nm thick chromium (Cr) adhesion layers are fabricated either on top of the stiff layer spun onto the soft membrane substrate, or are encapsulated at the interface between the two elastomers. Encapsulated gold films remain electrically conducting beyond 40% strain. But conductors deposited on top of stiff elastomer lose conduction at strains of 3-8%. These results suggest that, in addition to the stiffness of the elastomeric substrate, the initial microstructure of the metal film plays a role in determining its stretchability.

Pressure-sensitive dissipation in elastomers and its implications for the detonation of plastic explosives

The role of binder deformation and the associated energy dissipation on the detonation sensitivity of plastically bonded explosives is considered by accounting for dilatation-sensitive viscoelastic shear response. Following the observation that pressurization can prolong the relaxation and retardation times of a viscoelastic elastomer tremendously, the implications of this phenomenon are considered for a thin layer of a model elastomer, sheared between two blocks of octahydro-1,3,5,7- tetranitro-1,3,5,7-tetrazocine under deformation rates typical in detonation scenarios. The consequences of concurrent pressurization on heat generation are examined using small deformation as well as finite deformation analyses. While a dilatation-insensitive viscoelastic behavior generates notable temperature increases, they are insufficient to cause ignition of the explosive. However, taking into account the increased dissipation associated with the pressure-induced changes in the intrinsic time scale and viscosity of the elastomer leads to temperature rises on the order of 1000°C, which are consistent with “hot spots” held responsible for the initiation of detonation in the adjacent explosive grains.

Buckling in elastomer/plastic/elastomer 3‐layer films

AbstractBuckling during recovery of stretched elastomer/plastic/elastomer 3‐layer films was studied using a block copolymer elastomer and polyolefin plastics. An elastic model was developed to describe the critical wavelength, critical compressive strain, and critical compressive stress for buckling without delamination. The predicted linear dependence of critical wavelength on the plastic layer thickness was confirmed, and the modulus ratio between the plastic and the elastomeric layers was extracted. Determination of the critical compressive strain provided an independent calculation of the modulus ratio. Similar modulus ratios were obtained by the two methods. The critical compressive stress in the plastic layer led to reasonable values for the compressive modulus of the stretched plastic layer and the bulk modulus of the elastomeric layers. To test the model further, the modulus ratio was altered by changing the stretch ratio and by varying the plastic layer material. No buckling occurred if the modulus ratio was too small. Polym. Compos. 25:653–661, 2004. © 2004 Society of Plastics Engineers.

Buckling load of seismic isolators affected by flexibility of reinforcement

Using the thinner steel reinforcing plates in the elastomeric multilayer isolators could reduce the weight of the isolators but would have a large effect on the buckling load of an isolator, which cannot be analyzed by the Haringx theory, a traditional approach on the stability analysis of rubber bearings. The buckling load of the isolators, which includes the effect of the flexibility of the steel reinforcing plates, is analyzed by a beam theory in which shear deformation and warping of the cross-section are considered. Pressure distributions in the elastomeric layer bonded to flexible reinforcements under compression force, bending moment and warping moment are derived from an assumed displacement field, from which the warping-related parameters used in the beam theory are established. The thickness of the steel reinforcement in the isolators is determined from the buckling load of the isolators, which is solved from a cubic equation established by the beam theory.