Thin Rubber Layer Research Articles

Viscoelastic material enhancement of underwater sound absorption in higher-order resonators: from low-frequency to ultra-broadband

Underwater noise control is crucial for improving the marine acoustic environment. This study introduces a novel underwater acoustic absorber design that integrates viscoelastic materials with higher-order resonance structures to enhance the absorption efficiency of low-frequency sound waves. By embedding a thin layer of rubber within a conventional second-order Helmholtz resonator, the rubber's viscoelastic and damping properties significantly improve this structure's underwater low-frequency acoustic performance. Theoretical and simulation calculations have shown that the structure has two perfect absorption peaks in the low-frequency range. The simulation results show that in the frequency range of 415-1848 Hz (Simulation), only four units are needed to effectively absorb up to 90% of noise energy, and the total volume is only. Moreover, the absorber maintains excellent absorption performance over a wide range of incidence angles from 0 to 60 degrees. This work is helpful to design ultra-thin low-frequency underwater absorbers.

A new hybrid metamaterial absorber composed of ceramic resonators stacked on thin conductive rubber layer

In this letter, a hybrid metamaterial absorber made of ceramic resonators stacked on the traditional thin conductive rubber layer (RAT) has been developed. While RAT has been proven to be an effective absorber with good absorption around 10.5 GHz, its ability to absorb electromagnetic (EM) waves is inconsistent due to its flexible characteristic. Meanwhile, the absorption bandwidth above 90 % for RAT is constrained by its dispersion, limiting the coverage across the entire X-band (8–12 GHz). To address these limitations, we have incorporated the ceramic artificial nanostructure to enhance absorption intensity and broaden the absorption bandwidth by leveraging the strong magnetic Mie resonance of the ceramic resonator. Simultaneously, the number of absorption peaks and the bandwidth of each absorption peak can be controlled by adjusting the offset distance of the ceramic resonators and by varying the sintering temperature of the ceramics. Through the integration of metamaterial design and ceramic materials optimization, we have experimentally demonstrated the feasibility of multi-band, high-absorption devices by utilizing the hybrid structure of ceramic resonators and RAT, which opens up new possibilities for the further development of absorber devices.

Constitutive models for confined elastomeric layers: Effects of nonlinearity and compressibility

Elastomers tend to undergo large deformations accompanied by small volumetric changes. For elastomeric layers sandwiched between rigid plates, large deformations can be significantly limited by the constraints imposed by the plates. Further, those constraints can be enhanced by material’s inability to undergo large volumetric changes. From this perspective, it is appropriate to examine the validity of constitutive models, in which an elastomer is treated as incompressible, for analysis of the confined layers. Here, this issue is addressed by considering the mechanical response of sandwiched elastomeric layers using three constitutive models. The first one, referred to as compressible neo-Hookean, is regarded as exact. The other two models are regarded as approximations. Of those two, the first one neglects nonlinearity and the second one neglects compressibility. Accordingly, the modeling errors associated with the former are treated as measures of importance of nonlinearity, and the modeling errors associated with the latter are treated as measures of importance of compressibility. The modeling errors are evaluated using the force–displacement curve and the mean stress at the layer center as the quantities of interest. Numerical results are presented for rubber and polydimethylsiloxane (PDMS), characterized by Poisson’s ratios ν=0.4999 and ν=0.49, respectively. It is shown that, even when the forces applied to the plates are large, considering nonlinearity is important for thick but not for thin layers. In contrast, considering compressibility is important for thin layers. The need for considering compressibility is further assessed by introducing a competition parameter, which reinforces the notion that compressibility is important for modeling PDMS layers and thin rubber layers.

Ballistic performance of monolithic rubber-ceramic composite armor

This work presents the research results regarding the ballistic response characteristics of monolithic ceramic armors. Two different configurations of armors are considered for investigation, aiming at identifying ways to increase the ballistic performance of Small Arms Protective Insert (SAPI). The first configuration consists of a monolithic ceramic tile (Al2O3) with a backing plate made of high-performance Kevlar-29 fiber reinforced composite; the second one has the same design as the first, but the monolithic ceramic tile is covered by a thin rubber layer. The impact behavior of the ceramic composite armors is analyzed numerically, using the finite element method. Some characteristic features, including the ballistic performance and the fracture conoid angle (for the ceramic tile) are discussed. The numerical models developed for the two armor configurations are validated by ballistic tests, where the projectile impact on the armors and the mechanical integrity of the armor systems after impact are observed. The results from simulations and experiments show that the Al2O3/Kevlar 29 composite armor is able to capture a 7.62 mm bullet with a striking velocity of 690 m/s and the rubber-ceramic composite armor is able to capture 5.56 × 45 mm bullet M855 (with an armor piercing tip) with an impact velocity of 894 m/s. It has been found that, when a rubber layer is placed on the front face of a ceramic composite armor, better ballistic performance is achieved. The experiments show that, when a rubber material is impacted by a projectile, its behavior at high velocities and high strain rates changes from elastic to brittle.

Developing RobEVELOPING DURABLE SUPERAMPHIPHOBIC COATING ON ROUGH ALUMINUM USING RESIDUAL FROM BURNED RECYCLED SILICONE RUBBER FOR ANTI-CORROSIONust Superamphiphobic Coating on Rough Aluminum Substrates Using Recycled Silicon Rubber and Simple Spray Pyrolysis Technique for Anticorrosion Applications

This study presents a new, cost-effective, and environmentally friendly approach for creating a superamphiphobic coating. The method involves using a spray coating technique to apply silicone rubber onto smooth and micro-rough aluminum (Al) substrates. To enhance the coating's surface energy reduction, a thin layer of silicone rubber – trifluorotoluene (SR-TFT) was added. The morphology and chemistry of the coatings were analyzed utilizing scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and Fourier Transform Infrared Spectrometer (FTIR). The coatings displayed superamphiphobic properties with contact angles (CAs) of 170° for water and over 150° for both glycerol and ethylene glycol. Additionally, a remarkably low water droplet sliding angle (SA) of less than 2° was observed for surfaces coated with silicone rubber (SR)- trifluorotoluene (TFT), whether smooth or roughened. The coatings were tested for mechanical and chemical durability by impinging water droplets and immersing them in an acidic liquid respectively. The results showed that SR-TFT-coated silicone rubber on micro-rough Al substrates maintained its superamphiphobic property and exhibited excellent corrosion resistance compared to hydrophilic Al plates. Furthermore, the coatings displayed self-cleaning properties when water droplets were poured over a dusty surface, as the rolling water droplets effectively collected contaminant particles, leaving the surface of the sample clean. These findings indicate potential applications for the developed coatings as self-cleaning surfaces in challenging environmental conditions.

Mechanical behaviour of rubber blocks

This study investigates the behaviour of rubber blocks bonded between two plates under combined compression and shear loading, using experimental and numerical analyses, and also approximate analytical theories. First, experimental data from a series of compression and shear tests of rubber blocks with different aspect ratios are presented. Next, numerical simulations are carried out with three-dimensional finite element (FE) models, allowing insight to be gained into the stress and strain fields within the blocks. Existing analytical theories for blocks under compression and combined compressive and shear loading are then reviewed, and their accuracy is evaluated against test and numerical results. The study shows that those theories accounting for the effect of the axial shortening of the blocks provide a better description of the combined compression and shear behaviour, compared to theories, developed for laminated structural bearings with many thin rubber layers, that ignore this effect. An improved theory is also proposed, which better describes the effects of the bulging of the compressed blocks on their shear and flexural parameters and provides a better fit to experimental and numerical results.

Locally resonant porous phononic crystal sensor for heavy metals detection: A new approach of highly sensitive liquid sensors

In this research, a novel and highly sensitive phononic crystal (PnC) sensor is presented for the detection of CdBr2 concentrations at a low scale (ppm) which is considered a highly toxic heavy metal ion in freshwater. The proposed sensor is composed of two thin layers of rubber covering both the top and bottom surfaces of a one-dimensional ternary porous silicon (PSi) PnC. As a result, the whole designed structure is arranged as {rubber/[PSi1/PSi2/PSi3]N/rubber}. The appearance of local resonant modes is due to the presence of two thin rubber layers as a cap layer of the PnC design. In particular, the spectral position of the modes is significantly tuned when filling the PSi layers with CdBr2 ions. It is worth mentioning that the novelty of this work is mainly focused on three axes. The first one is the use of locally resonant PnCs (not conventional defective ones) as highly sensitive biosensors. The second one, the liquid of interest here is considered a dangerous aqueous solution with a very low scale (ppm). The last promising point, we proposed the pores inside Si layers are filled with a liquid material in contrast to most of the micromechanics methods of composite materials that supposed the pores are empty (just voids are inside). To realize the best performance of this sensor, an optimization strategy of some related parameters such as the rubber layer thickness, the geometry of the PnC, and the unit cell number was conducted. In this regard, the proposed sensor provides promising values of sensitivity, quality factor, detection limit, and damping rate of 47.25 Hz/ppm, 2756.2, 82 ppm, and 0.00018, respectively. Therefore, the present design could be of serious contribution to liquid sensors and bio-sensing applications due to its simplicity, novelty, and high performance.

Rice Husk Ash/Silicone Rubber-Based Binary Blended Geopolymer Coating Composite: Fire Retardant, Moisture Absorption, Optimize Composition, and Microstructural Analysis.

Geopolymer coating using rice husk ash (RHA) as the aluminosilicate source has shown excellent fire retardant properties. However, incorporation of rice husk ash into the geopolymer matrix increased water absorption properties of the polymer composite. As such, silicone rubber (SiR) was introduced to improve the moisture absorption and fire retardant properties of the composite. Additionally, the less efficient one-factor-at-a-time (OFAT) approach was conventionally used in past studies on the RHA-based geopolymer composite. In understanding the optimum value and significant effect of factors on the fire retardant and moisture absorption properties of the binary blended geopolymer coating composite, the use of statistical analysis and regression coefficient model (mathematical model) was considered essential. The objectives of this study are to identify the significant effect of factors on moisture absorption and fire retardant properties, to determine the optimum composition, and to study the microstructure of the rice husk ash/silicone rubber (RHA/SiR)-based binary blended geopolymer coating composite. The RHA/AA and SiR/Ge ratios were chosen as factors, and the response surface methodology (RSM) was employed to design experiments and conduct analyses. Fire retardant and moisture absorption tests were conducted. A scanning electron microscope (SEM) was used to observe the microstructure of geopolymer samples. The RHA/alkaline activator (AA) and SiR/Ge ratios were shown to have a significant effect on the responses (temperature at equilibrium and moisture absorption). The high ratio of RHA/AA and SiR/Ge resulted in a lower temperature at equilibrium (TAE) below 200°C and at moisture absorption below 16%. The optimum formulation for the geopolymer coating composite can be achieved when the RHA/AA ratio, SiR/Ge ratio, and sodium hydroxide concentration are set at 0.85, 0.70, and 14 M, respectively. SEM micrographs of samples with good fire retardant properties showed that the char residue of the geopolymer composite coating, which is a layer of excess silicone rubber, is porous and continuous, thus providing a shielding effect for the layer of geopolymer underneath. The sample with good moisture absorption showed the formation of a thin outer layer of silicone rubber without any cracks. The unreacted SiR formed a thin layer beneath the geopolymer composite matrix providing a good moisture barrier.

Analysis of Reasons for Reduced Strength of Multiply Conveyor Belt Splices

Belt conveyors are used for the transportation of bulk materials in a number of different branches of industry, especially in mining and power industries or in shipping ports. The main component of a belt conveyor is its belt, which serves both as a support for the transported material along the conveyor route and as an element in the drive transmission system. Being crucial to the effective and reliable operation of the conveyor, the belt is also its most expensive and the least durable element. A conveyor belt comprises a core, covers and edges. A multiply textile belt, in which the core is constructed of synthetic fibers such as polyamide, polyester or aramid, is the oldest and still the most commonly used conveyor belt type. The plies are joined with a thin layer of rubber or another material (usually the material is the same as the material used in the covers), which provides the required delamination strength to the belt and allows the plies to move relative to each other as the belt is bent. Belts are installed on the conveyors in a closed loop in order to join belt sections, whose number and length depend on the length and type of the belt conveyor. Belts are joined with each other in a splicing procedure. The cutting of the belt core causes belt splices to be prone to concentrated stresses. The discontinued core also causes the belt to be the weakest element in a conveyor belt loop. The article presents the results of strength parameter tests that were performed on laboratory and industrial splices and indicated the reasons for the reduced strength of conveyor belt splices. Splice strength is reduced mainly due to incorrect preparation of the spliced surfaces and to different mechanical parameters of the spliced belts.

Vibration attenuation of finite-size metaconcrete: Mechanism, prediction and verification

To mitigate shock and vibration, metaconcrete with single-mass-coating resonators and double-mass-coating resonators was designed based on local resonance mechanism. The resonator is constructed by metallic ball coated with thin and soft rubber layer. Dynamic analysis method for finite-size metaconcrete is developed to predict the effective bands for vibration attenuation, which is verified by frequency-sweeping vibration experiment. Local resonance of the mass-coating system endows finite-size metaconcrete excellent vibration attenuation ability at the desired frequency band. Having two local resonation frequencies, double-mass-coating system effectively expands the vibration attenuation band from one to two and much wider compared with single-mass-coating system. The finite-size metaconcrete block designed in this research can dissipate 56.4% more energy than the common concrete block.

Seismic behavior of unbonded post-tensioned precast concrete members with thin rubber layers at the jointed connection

Seismic behavior of unbonded post-tensioned precast concrete members with thin rubber layers at the jointed connection

Calculation of thin-layer rubber-metal elements of machines and buildings considering the compressibility of the material

In some constructions with rubber-metal elements, the rubber is loaded in such a way that the hydrostatic stress is tens of times greater than the shear stress. In this case, ignoring the compressibility of rubber can lead to large errors in calculating the elastic and strength parameters of rubber parts. The elastic elements, for which consideration of the material compressibility is essential, include thin-layer rubber-metal elements, whose dimensions in plan are much larger than the thickness. Such rubber-metal elements are used for vibration and seismic protection of heavy machines, buildings and structures. In this paper, the compression of a thin-layer cylindrical rubber-metal element is considered with taking into account the compressibility of the material. In the calculation, it was assumed that the hydrostatic stress is constant over the thickness of the rubber layer, and also that the rate of change of the displacement components in the middle surface of the layer can be neglected in comparison with the corresponding speed in the direction normal to the layer. These assumptions were substantiated as a result of the analysis of the geometry of deformation and equilibrium conditions of a thin layer of rubber bonded to metal reinforcement. As a result of applying these assumptions to the solution of the problem set, a boundary value problem is obtained for an ordinary inhomogeneous linear differential equation of the second order. The corresponding homogeneous equation is solved using a power series, the coefficients of which are expressed in terms of the previous ones using a recurrent formula. Finally, a formula with a modified Bessel function of the first kind is obtained for the hydrostatic stress. The analysis of the obtained formula leads to some simplifications for different values of the dimensionless parameter, which connects the bulk modulus and shear modulus, and the radius of the cylindrical element and its thickness. The resulting axial load on the rubber element is represented by the force that would be perceived by the element in case of uniaxial deformation, i.e. if displacements in cross-sections were prohibited and compression would be performed only due to the change in volume, multiplied by a certain coefficient less than one, which takes into account the decrease in the stiffness of the element due to shear deformation. The paper also presents the results of experimental studies carried out by the authors for thin-layer cylindrical rubber-metal elements made of medium-filled rubber 2959. An example of calculating the axial load on a thin-layer element considering the compressibility of rubber is given. The obtained axial load value coincides with the experimental results with a sufficient accuracy value. Keywords: thin-layer rubber-metal element, rubber compressibility, hydrostatic stress, axial load.

Theoretical design of porous phononic crystal sensor for detecting CO2 pollutions in air

Abstract Phononic crystal sensor is a novel technology for sensing applications with high performance. The present work proposes theoretically a design of gas (CO2) sensor based on a one-dimensional (1D) porous silicon (PSi) phononic crystal (PnC) sandwiched between two thin rubber layers. The transfer matrix method (TMM) was used for the numerical modeling of the acoustic waves spectra through the 1DPSi-PnC sensor structure. The results showed that a resonant mode was created inside the transmission spectrum as a result of the presence of the two-sided rubber layers. Also, the position of the resonant mode was invariant with changing CO2 concentration, temperature, and pressure. On the contrary, the intensity of the transmitted mode is very sensitive to any change in these parameters. With increasing the CO2 concentration (from 0% to 90%) and pressure (from 2 atm to 6 atm), the intensity of the resonant mode are significantly increased. While, with increasing temperature (from 20 °C to 200 °C), the intensity of the resonant mode is decreased. These results are correlated directly to the density of the CO2/air mixture. Therefore, the proposed 1DPSi-PnC sensor can measure CO2 pollutions in the surrounding air over a wide range of concentration, temperature, and pressure values. The merits of a gas sensor based on porous materials and PnC structure are numerous. For example, the ease of fabrication, working under tough conditions, and its capability to sense CO2 pollutions from the surrounding air directly. Also, the proposed sensor can be developed as a monitor for many gases in industrial and biomedical applications. Moreover, porous materials enable the proposed design to be compatible with other fluidic components specifically liquids. Thereby, allowing the proposed gas sensor to be replicated for various fluidic sensing applications.

Rubber artificial skin layer with flexible structure for shape estimation of micro-undulation surfaces

In this paper, we propose a wearable tactile sensor for measuring the shape of micro-undulations on a hard surface. The proposed sensor has two layers. The inner one is a thin rubber layer into which a strain gauge is embedded that is formed around a user’s finger. The outer layer is a flexible structure that consists of numerous pins on a flexible sheet. The shape of micro-undulations on an object surface can be measured when a user wearing the sensor traces the surface. The results of an experiment, in which we compare the cases with and without the flexible structure of the sensor, show that our proposed sensor is sufficiently accurate to measure the shape of micro-undulations due to its flexible structure, which contributes significantly to improving its signal-to-noise ratio.

Vibroseismic protection of heavy mining machines, buildings and structures

In the article, the authors analyze main issues of protecting buildings and structures against vibroseismic effects with the help of system of elastomeric blocks, which are characterized by high vertical stiffness, low shear stiffness, high energy dissipation and ability to center vertical load; besides, they feature high reliability with no risk of sudden failure. Results of static and dynamic tests of parametric series of elastomeric blocks used for protection of residential buildings against vibrations are presented. Design of pile with anti-vibration rubber supports is described. Calculation of elastomeric blocks under static compression is presented. Components of the stress-strain state of the thin-layer elements were investigated, and rate of the thin rubber layer compression under the action of vertically applied force was calculated. In numerical calculation, weak compressibility of rubber was simulated by moment force of the finite element for weakly compressible materials, which assumes triple approximation of displacement fields, deformation components, and volume change function. The numerical solution was obtained by the finite element method for different radius-thickness ratios in case of geometrically nonlinear elastic and viscoelastic deformation.

Numerical Simulation of the Stress-Strain State of Thin-Layer Rubber-Metal Vibration Absorber Elements Under Nonlinear Deformation

Stress-strain state components of thin-layer rubber-metal elements are investigated. The compression level of a thin rubber layer under the action of vertically applied stress is calculated. For simplified hypotheses the relationship between the rubber layer thickness reduction and its radius-thickness ratio was analytically derived. The problem was solved under linear-elastic deformation of a rubber layer vulcanized onto the metal plates. For numerical calculations, weak rubber compressibility was simulated with the moment finite element scheme for weakly compressible materials, involving the triple approximation of displacement fields, strain components, and a volume variation function. The numerical solution was obtained by the finite element method for different layer radii and thicknesses under geometrically nonlinear elastic and viscoelastic deformation of the rubber material. The geometrical nonlinearity is described by the nonlinear strain tensor. Viscoelastic rubber properties are simulated by the hereditary Boltzmann– Volterra theory with the Rabotnov relaxation kernel. Nonlinear boundary problems are solved by the modified Newton–Kantorovich method. The calculation is effected for the two cases of curing the rubber layer onto the metal elements of the structure. The first case assumes that the rubber layer is vulcanized onto the metal plates, in the second one, it can freely slide over their surface. For the first case, numerical results are compared with the analytical solution. The effect of geometrical nonlinearity and viscoelastic rubber properties on the rubber layer thickness reduction was examined.

ゴム皮膚層にワイヤ駆動機構を内蔵する連続体マニピュレータ

In this paper, we propose a method to fabricate a slim continuum manipulator by embedding pulling-wire mechanisms into a thin rubber layer formed around an elastic backbone of the manipulator without increasing its elasticity largely. Fundamental experimental results show that the continuum manipulator prototype based on the proposed method can achieve, not only bending on several planes on three-dimensional space by pulling its three wires appropriately, but also a 360-degree bending of its tip in some direction with forming non-constant curvature shape. It is also shown that a simple mathematical model can explain the linear relationship between the tip bending angle and the wire pulling distance which is verified experimentally.

Experimental characterization, design and modelling of the RBRL seismic‐isolation system for lightweight structures

SummaryThe Rolling‐Ball Rubber‐Layer (RBRL) system was developed to enable seismic isolation of lightweight structures, such as special equipment or works of art, and is very versatile, a great range of equivalent natural frequencies and coefficients of damping being achievable through choice of the system parameters.The necessity to have a simple and effective design procedure has led to a new parametric experimentation at Tun Abdul Razak Research Centre (TARRC) on the rolling behaviour of the RBRL system and load–deflection behaviour of the recentering springs. The experimental results, together with theories for the rolling resistance of a loaded steel ball on a thin rubber layer and the lateral load–deflection behaviour of cylindrical rubber springs, are used to develop a general design method for the RBRL system, which allows the system to be tailored to the specific application.Sinusoidal test results are presented for the small‐deflection behaviour of the system, influenced by the presence of a viscoelastic depression on the rubber tracks beneath each ball, and an amplitude‐dependent time‐domain model is proposed, based on these results and on the steady‐state behaviour of the system. The model is validated through comparison with previously performed shaking‐table tests. Attention is here restricted to uniaxial behaviour. Copyright © 2016 John Wiley & Sons, Ltd.

Mechanically stretchable and tunable metamaterial absorber

In this letter, we present experimental demonstration of a mechanically stretchable and tunable metamaterial absorber composed of dielectric resonator stacked on a thin conductive rubber layer. A near unity absorption is observed due to strong local field confinement around magnetic Mie resonance of dielectric resonator. Furthermore, the interspacing between unit cells is modulated dynamically under uniaxial stress. Owing to the decreases of longitudinal coupling between neighboring unit cells, the resonant absorption peak is reversibly tuned by 410 MHz, as the stain varies up to 180% along H field direction. On the contrary, the resonant absorption state is nearly independent on strain variation when external stress is applied along E field direction, due to the weak transverse interplaying. The mechanically tunable metamaterial absorber featured by flexibility paves a way forwards for actual application.

The filler-rubber interface in styrene butadiene nanocomposites with anisotropic silica particles: morphology and dynamic properties.

Silica-styrene butadiene rubber (SBR) nanocomposites were prepared by using shape-controlled spherical and rod-like silica nanoparticles (NPs) with different aspect ratios (AR = 1-5), obtained by a sol-gel route assisted by a structure directing agent. The nanocomposites were used as models to study the influence of the particle shape on the formation of nanoscale immobilized rubber at the silica-rubber interface and its effect on the dynamic-mechanical behavior. TEM and AFM tapping mode analyses of nanocomposites demonstrated that the silica particles are surrounded by a rubber layer immobilized at the particle surface. The spherical filler showed small contact zones between neighboring particles in contact with thin rubber layers, while anisotropic particles (AR > 2) formed domains of rods preferentially aligned along the main axis. A detailed analysis of the polymer chain mobility by different time domain nuclear magnetic resonance (TD-NMR) techniques evidenced a population of rigid rubber chains surrounding particles, whose amount increases with the particle anisotropy, even in the absence of significant differences in terms of chemical crosslinking. Dynamic measurements demonstrate that rod-like particles induce stronger reinforcement of rubber, increasing with the AR. This was related to the self-alignment of the anisotropic silica particles in domains able to immobilize rubber.