Rubber Membrane Research Articles

Broadband low-frequency noise attenuation with parallel U-shaped membrane resonators

The attenuation of noise at low frequencies has been the subject of extensive research in the last two decades. Employing membrane-type acoustic metamaterials (MAMs) is one of the most promising solutions due to their lightweight structure and ease of fabrication. This study fabricated a metamaterial with four U-shaped cavities supporting a thin elastic nitrile rubber membrane. We print the U-shaped cavities using fused deposition modeling (3D printing). The sound absorption coefficient (SAC) is calculated using numerical simulations. For SAC computation, an electro-acoustic model is developed that constructs an equivalent electrical circuit based on an impedance analogy. Furthermore, the findings of the numerical and analytical analyses are supported by the actual data acquired from the experiments. We have determined that the average sound transmission loss (STL) is 29.84 dB, and the average SAC exceeds 82% within the frequency range of 500 Hz to 1000 Hz. Due to its lightweight, subwavelength thickness, ability to attenuate broadband noise, and very simple fabrication, this metamaterial is suitable for use in aircraft, automotive industries, and room/building acoustics.

Impact of rubber membrane on lunar regolith mechanical properties under low effective confining pressure

The existing lunar exploration activities and associated equipment interactions are limited to the surface environment, where the stress state of the lunar regolith is significantly lower than that in laboratory tests conducted on Earth. To address this, this paper proposes a new framework for discrete modeling of large-scale triaxial tests on lunar regolith under low confining pressure. The framework incorporates particle shapes from the Chang’E-5 mission (CE-5) and flexible boundary conditions. Firstly, the shape characteristics of the lunar regolith particles were adopted in the Discrete Element Method (DEM) model to reproduce the mechanical properties of the lunar regolith as accurately as possible. Then, experiments with varying membrane particle stiffness ratios were conducted to explore the effect of the rubber membrane’s properties on the mechanical characteristics of lunar regolith under low effective confining pressure. Topological Data Analysis (TDA) tools from persistent homology were utilized to quantify the dynamic response of particles during the onset and development of strain localization. The results indicate that under low effective confining pressure, selecting appropriate rubber membrane types is crucial for accurately determining the mechanical properties of lunar regolith.

The application of PVC hollow fiber ultrafiltration membrane in ultra-low permeability oilfield

Abstract Oil containing wastewater produced from ultra-low permeability oil fields generally needs to be treated to meet the 5-1-1 standard before it can be reinjected. In order to meet the standards for treating oily wastewater in ultra-low permeability oil fields, PVC hollow fiber ultrafiltration membranes and pre-treatment processes for removing oil, suspended solids, sulfides, etc. before the membrane were selected. The application shows that the aeration air flotation flow sand filtration PVC hollow fiber ultrafiltration membrane process can treat oily wastewater, and the treated water can reach the “5-1-1” standard. In the pre-treatment process of PVC hollow fiber ultrafiltration membrane, the silicone rubber membrane aeration device has good oxidation effect, high efficiency in micro nano air flotation for oil removal and suspended solids, and easy management of sand flow filters. This process has economic feasibility and provides technical support for the treatment of oily wastewater in ultra-low permeability oil fields, with great promotional value.

Soft bottles drain faster but glug slower

An inverted container of water drains with a periodic glugging process where bubbles of air enter through the bottom hole, thus replacing the exiting water. If the container is soft, its walls can flex with each glug. We examine the effect of container elasticity on the drainage process. Experiments are conducted to measure the drainage rate and the glug period as water drains out of a container through a bottom hole. The container compliance is varied by varying the diameter of a soft rubber membrane comprising the lid of the container. Increasing container compliance (i.e., making the container softer) is found to increase the drainage velocity, increase the glugging period, and increase the volume of each glug. Previously, Clanet and Searby (2004) modeled the glugging process as a spring-and-mass oscillator where the compressibility of air in the headspace acts as the spring. We adapt this model so that the membrane elasticity acts in series with the air compressibility. This adapted model qualitatively agrees with the observations but underpredicts the observed effect on the glug period.

Empowering Particle Jamming Soft Gripper with Tactility via Stretchable Optoelectronic Sensing Skin

Particle‐jamming soft grippers demonstrate notable shape adaptability and adjustable stiffness, which improve their grasping efficiency. However, integrating tactile sensing into these grippers presents challenges due to the specific properties of the particle jamming mechanism. This study introduces a parallel particle jamming soft gripper equipped with tactile sensing capabilities. The gripper consists of two tactile sensing particle jamming pads (TSPJPs) that are integrated with flexible optoelectronic skins. These skins are made of silicone rubber membranes and are embedded with a 3 × 3 array of stretchable optical waveguide arrays (SOWAs). Testing indicates that incorporating these sensors enhances the gripper's tactile sensing capabilities, with minimal impact on its particle jamming‐based grasping function. A single TSPJP can accurately detect various contact points and estimate the contract forces. The proposed soft gripper can reliably grasp a wide range of objects, varying in shape, hardness, and weight, and it provides detailed tactile feedback on contact locations and the intensity of the grasping through the SOWA sensor. It can precisely distinguish between different grasping postures using a light gradient boosting machine (LightGBM) learning model. Furthermore, it can effectively detect the slippage of grasped objects, facilitating accurate closed‐loop control for secure manipulation.

Improving durability and efficiency in passive direct ethanol fuel cells using a biodegradable polyvinyl alcohol/epoxidized natural rubber membrane

AbstractIn this study, a novel biodegradable polymer electrolyte membrane with reduced fuel crossover, high selectivity, and high conductivity compared with Nafion 117 membrane in direct ethanol fuel cells (DEFCs) has been reported. Herein, polyvinyl alcohol/epoxidized natural rubber (PVA/ENR) blend membranes were synthesized via a simple solution casting method and applied in DEFCs. The structural and physicochemical features of the PVA/ENR blend membranes were examined using FESEM, FTIR, XRD, water absorption, ethanol uptake, swelling ratio and oxidative stability. ENR enhances the chemical, structural, and mechanical characteristics of PVA, making it a valuable material in fuel cell applications. The incorporation of ENR into the PVA matrix results in a compact morphology, excessive multifunctional groups, low fuel crossover, and high selectivity. The optimum membrane thickness achieves the highest selectivity, reaching up to 12.32 × 104 S s cm−3 at 30°C. Additionally, the maximum power density achieved is 19.52 mW cm−2, surpassing that of the Nafion membrane, which is only 14.55 mW cm−2 at 90°C. Furthermore, this biodegradable membrane can sustain operation for 1000 h at 90°C, owing to its ability to maintain hydration for an extended period. This study represents the first attempt to combine PVA and ENR in fuel cells.

The role of the carapace in the accumulation of metals from seawater in the green crab (Carcinus maenas): Studies with radio-labeled calcium, zinc, and nickel

The role of the carapace in the uptake and storage of newly accumulated metals was investigated in the green crab exposed to environmentally relevant concentrations of calcium ([Ca] = 389 mg L−1 or 9.7 mmol L−1), zinc ([Zn] = 82 μg L−1 or 1.25 μmol L−1), and nickel ([Ni] = 8.2 μg L−1 or 0.14 μmol L−1) in 12 °C seawater, using radio-tracers (45Ca, 65Zn, 63Ni). After 24-h exposure, carapace exhibited the highest concentration of newly accumulated Ca, whereas carapace and gills exhibited the highest concentrations of both newly accumulated Zn and Ni relative to other tissues. For all three metals, the carapace accounted for >85 % of the total body burden. Acute temperature changes (to 2 °C and 22 °C) revealed the highest overall temperature coefficient Q10 (2.15) for Ca uptake into the carapace, intermediate Q10 for Ni (1.87) and lowest Q10 (1.45) for Zn. New Ca uptake into the carapace continued linearly with time for 24 h, new Zn uptake gradually deviated from linearity, whereas Ni uptake reached a plateau by 6 h. Attachment of a rubber membrane to the dorsal carapace, thereby shielding about 20 % of the total crab surface area from the external water, eliminated both new Zn and Ni incorporation into the shielded carapace, whereas 36 % of new Ca incorporation persisted. When recently euthanized crabs were exposed, new Zn uptake into the carapace remained unchanged, whereas Ca and Ni uptake were reduced by 89 % and 71 %, respectively. We conclude that the carapace is a very important uptake and storage site for all three metals. All of the uptake of new Zn and new Ni, and most of the uptake of new Ca into this tissue comes directly from the external water. For Zn, the mechanism involves only physicochemical processes, whereas for Ca and Ni, life-dependent processes make the major contribution.

Dural Closure Training With Prototyped Model.

The hermetic closure of the dura mater is a critical step in neurosurgical training, often undervalued but crucial to preventing serious complications such as cerebrospinal fluid (CSF) leaks leading to meningitis and death. Inadequate closure, often due to insufficient training, can result in challenging complications, including prolonged hospitalization and reoperation. To address the deficiencies in dural closure training, this study aims to describe a 3D prototype for simulating post-craniotomy dura mater suturing. The objective is to reduce the incidence of CSF leaks and improve the training of neurosurgery residents. The study involves the creation of a 3D prototype based on magnetic resonance imaging and computed tomography scans. The additive manufacturing of structures is performed using ABS filament, and a silicone rubber membrane is used to simulate the meningeal dura mater. Neurosurgery residents undergo training using this model, and the effectiveness is evaluated. The study is conducted at the Institute of Neurology of Curitiba (Hospital INC), focusing on neurosurgery residents from the first to fifth year of residency. Seven residents participate in the study, with varying levels of experience in dural closure procedures. The training involves a simulated surgical environment using the 3D prototype. After training, residents show improvements in confidence and theoretical knowledge related to dural closure. Binary questions indicate a strong desire for more practical training on dural closure, with 85.7% believing in the essential role of 3D molds in their neurosurgery training. The study highlights the importance of adequate training for dural closure to prevent serious complications in neurosurgery. The use of 3D simulation models, despite some limitations, proves to be an effective educational strategy. The emerging technology of bioprinting holds promise for further enhancing simulation materials, bringing medical education closer to realistic tissue replication.

Sheet-coating mitigation for membrane penetration in undrained triaxial tests and evaluation of comprehensive liquefaction resistance of crushed gravel

In undrained cyclic triaxial tests on crushed gravel, it is difficult to maintain undrained conditions because of the penetration of the rubber membrane (MP: membrane penetration) into the rough surface of the test specimens. A method has been developed in the present research to physically mitigate the MP-effect wherein the rough surface of each specimen is coated and smoothed by a prefabricated fines-soil sheet. This mitigation measure has been found very effective in minimizing the CR (compliance ratio for an undrained system) to achieve more strict undrained conditions. It has been further clarified that this method prevents not only the overestimation of the strength of loose specimens, as has already been recognized, but also the underestimation of the strength of dense specimens with highly positive dilatancy. The undrained cyclic strength of dense crushed gravel, comprised of various grain sizes and gradations, has been summarized in a series of undrained cyclic triaxial tests by employing the MP-mitigation method to find that, in place of the relative density governing the liquefaction resistance of loose soils, the void ratio or absolute density is a key parameter for uniquely estimating the strength with a simple empirical formula.

Determination of the Shear Strength of Unsaturated Loess Samples from Conventional Triaxial Shear Tests Applying Rubber Membrane Correction

Determination of the Shear Strength of Unsaturated Loess Samples from Conventional Triaxial Shear Tests Applying Rubber Membrane Correction

Sound Absorption Characteristics of Integrated Membrane-Fabric Materials

Noise pollution has emerged as one of the most important environmental issues, particularly in developing countries. The use of sound absorption material has proven to be a successful approach for minimizing and controlling noise levels. Combining a membrane or panel with two or more porous materials is a practical approach for sound absorption. However, it often makes the absorber thicker, taking up more space and increasing production costs. This research proposes a new integrated sound absorber that combines a rubber membrane with a fabric to absorb sound at different frequencies. The new material eliminates bulky porous materials, saving space and production costs. By varying perforation sizes, percentages, and backed air gap distances, the study investigates the sound absorption characteristics of the integrated membrane-fabric material. The research has determined that the integrated membrane-fabric material exhibits exceptional sound absorption performance across a wide frequency range, which is influenced by several factors, including the diameter and ratio of perforations, and the depth of the air cavity. Furthermore, the investigation revealed that the positioning of the fabric also plays a crucial role in determining the material's absorption performance.

Silicone rubber membrane devices permit islet culture at high density without adverse effects.

Conventional culture conditions, such as in T-flasks, require that oxygen diffuse through the medium to reach the islets; in turn, islet surface area density is limited by oxygen availability. To culture a typical clinical islet preparation may require more than 20 T-175 flasks at the standard surface area density of 200IE/cm2. To circumvent this logistical constraint, we tested islets cultured on top of silicon gas-permeable (GP) membranes which place islets in close proximity to ambient oxygen. Oxygenation of individual islets under three culture conditions, standard low-density, non-GP high density, and GP high density, were first modeled with finite element simulations. Porcine islets from 30 preparations were cultured for 2days in devices with GP membrane bottoms or in paired cultures under conventional conditions. Islets were seeded at high density (HD, ∼4000IE/cm2, as measured by DNA) in both GP and non-GP devices. In simulations, individual islets under standard culture conditions and high density cultures on GP membranes were both well oxygenated whereas non-GP high density cultured islets were anoxic. Similarly, compared to the non-GP paired controls, islet viability and recovery were significantly increased in HD GP cultures. The diabetes reversal rate in nude diabetic mice was similar for HD GP devices and standard cultures but was minimal with non-GP HD cultures. Culturing islets in GP devices allows for a 20-fold increase of islet surface area density, greatly simplifying the culture process while maintaining islet viability and metabolism.

Acoustic Analysis and Experimental Validation of Acoustic Metamaterial

In this study, a unique sound insulation performance of a lightweight acoustic metamaterial consisting of a stiff honeycomb plate coated with a thin rubber membrane was experimentally demonstrated. An acoustic transmission measurement of the acoustic metamaterial showed that the sound insulation performance of the acoustic metamaterial exceeded the mass law predicted performance in three frequency ranges. An analysis of the acoustic-structure interaction revealed that these unique sound insulation phenomena were due to the cancellation between two high-order eigenmodes of the periodic structure or a high-order eigenmode of the periodic structure and an eigenmode of the membrane in each honeycomb cell. Subsequently, a prototype of this acoustic metamaterial was applied to a vehicle and its effectiveness on vehicle interior noise was investigated. The results show that such materials can further improve the level of quietness with weight reduction in vehicles and other transportation applications.

Gradation Influence on Crack Resistance of Stress-Absorbing Membrane Interlayer

Reflective cracking is a common distress of old pavement overlaid with an asphalt layer. The asphalt rubber stress-absorbing membrane interlayer can effectively mitigate and prevent reflective cracking. However, the existing test methods and evaluation indices for the crack resistance of the asphalt rubber stress-absorbing membrane interlayer are insufficient and unsystematic. They do not account for the significant effect of gradation parameters on the crack resistance in a comprehensive way. Therefore, this research aims to explore the impact of gradation parameters on the performance of the asphalt rubber stress-absorbing membrane interlayer. Based on the Chinese and U.S. standards, three kinds of 10 types of gradation were selected, forming a total of seven groups. The asphalt rubber stress-absorbing membrane interlayer was subjected to −10 °C and 15 °C beam bending test, low-temperature semi-circular bend test, crack expansion semi-circular bend test, and overlay test to evaluate its cracking resistance. The correlation and influence law between the key sieve hole method, graded fractal method, and Bayley method parameters of different grades and beam bending test, low-temperature semi-circular bend test, crack expansion semi-circular bend test, and overlay test indexes were quantitatively analyzed by the coefficient of variation and Pearson correlation analysis method. The results showed that the performance of the mixtures with different gradation ranges varied significantly in different tests, as indicated by the maximum difference of 56.07% in stress absorption. This implied that gradation is a critical factor that affects the stress absorption performance of mixes. The different sensitivities of different tests to the parameters of the key sieve method, the graded fractal method, and the Bailey method indicated that the stress absorption performance was affected by a combination of factors. Therefore, in order to evaluate and optimize the stress absorption performance, it was necessary to comprehensively consider the interactions among the parameters of the key sieve method, the graded fractal method, and the Bailey method. The stress absorption performance included crack resistance and crack expansion resistance, which were inversely related and needed to be balanced and optimized during design. The −10 °C beam bending test and crack expansion semi-circular bend tests were more suitable test methods for evaluating stress absorption performance, and maximum flexural–tensile strain, strain energy density, fracture energy, and flexibility index were recommended as evaluation indicators. This research provides a reference for the optimization of the grading design of asphalt rubber stress-absorbing membrane interlayers, and provides test methods and indicators for the evaluation of crack resistance.

Morphology Control of Electrospun Brominated Butyl Rubber Microfibrous Membrane.

Brominated butyl rubber (BIIR) is a derivative of butyl rubber, with the advantage of high physical strength, good vibration damping performance, low permeability, aging resistance, weather resistance, etc. However, it is hard to avoid BIIR fiber sticking together due to serious swelling or merging, resulting in few studies on BIIR electrospinning. In this work, brominated butyl rubber membrane (mat) with BIIR microfiber has been prepared by electrospinning. The spinnability of elastomer BIIR has been explored. The factors influencing the morphology of BIIR microfiber membranes have been studied, including solvent, electrospinning parameters, concentration, and the rheological property of electrospinning solution. The optimal parameters for electrospinning BIIR have been obtained. A BIIR membrane with the ideal microfiber morphology has been obtained, which can be peeled from aluminum foil on a collector easily without being broken. Anti-bacterial property, the electrical conductivity of these membranes, and the mechanical properties of these samples were studied. The optimized BIIR electrospinning solution is Bingham fluid. The results of these experiments show that a BIIR membrane can be used in the field of medical prevention, wearable electronics, electronic skin, and in other fields that require antibacterial functional polymer materials.

Numerical simulation of biaxial undrained shear test based on fluid–solid coupling DEM method

The undrained shear test plays a crucial role in comprehending the deformation and failure mechanisms inherent in rock and soil. While the test offers a macroscopic perspective, numerical simulations can delve into the microscopic aspects of sample behavior, thereby compensating for this limitation. Drawing inspiration from the measurement sphere fluid–solid coupling method and the discrete element method, this paper proposes a tailored numerical simulation approach for the biaxial undrained shear test. This approach is implemented in the high-performance discrete element software MatDEM. In this study, a rapid division method for the fluid network is presented, along with a detailed explanation of the control equation governing excess pore water pressure and fluid–solid interaction during shear. Subsequently, A custom flexible boundary with a relatively smooth surface is introduced to simulate the constraint of the rubber membrane, which helps reduce simulation errors. Furthermore, the specific process of the numerical simulation is introduced, and an effective method for generating samples with high void ratios is proposed. Finally, three different cases are presented, involving varying confining pressures, different void ratios, and specific shear paths, respectively. The results indicate that the proposed method can effectively simulate the process of undrained shear tests and accurately capture the excess pore water pressure responses, and lateral deformation of the samples during shearing.

Modal and harmonic acoustical analysis of a circular rubber membrane and classification of resonant frequencies using deep learning

Mode shapes of a component or a structure can be determined by conducting Modal analysis. Chladni figures can also be used to determine the mode shapes of a plate. In this research comparison of these mode shapes using Chladni figures and ANSYS simulation has been carried out. Analysis systems used for ANSYS simulation are Harmonic Acoustic Analysis and modal analysis. With the help of wave equation, a mathematical formulation has been achieved. The experimental and simulation results are compared, and an error of not more than 9% for modal and 10% for harmonic acoustics is found. Classification of these Chladni figures which are obtained experimentally, using Deep Learning algorithms like Inception ResNetV2, VGG16 and Xception and have achieved 100 percent accuracy at different converging times.

Combined effect of fly ash and fiber on spreadability, strength and water permeability of foam concrete

Strength and permeability are the two critical properties of interest for various applications of foam concrete (FC). These properties are well known to be highly dependent on parameters such as density, mix composition and microstructure of FC. Among various measures to enhance the strength and permeation characteristics of FC, incorporation of fly ash and polypropylene fiber has been proven to be effective solutions by various studies. In terms of permeability, though the measurement of air/water permeability has been suggested by various methods, usually such measurements are limited to a pressure of 3 bar. For higher pressures (as recommended in codal provisions) no to limited work is available. In this paper, variation in spreadability, permeability, compressive strength and split tensile strength of FC due to replacement of 50% of sand with Class F fly ash and incorporation of polypropylene fiber is investigated on a systematic basis. For the measurement of permeability at higher pressures (>3 bar), use of novel sealing mechanism using 5 mm thick rubber membrane as sealant with iron spiral cylinder and clamp as casing, is attempted in this work. The present study is first of kind of study using the above-mentioned sealing mechanism for measurement of permeability of FC at higher pressures. Further, only scanty literature is available on permeation behavior of FC with fly ash (as filler) and polypropylene fiber. As per the present findings, particularly in lower density mixes (say density 1000 kg/m3) tested at age of 56 days, replacement of 50% of fine aggregate (by weight) by Class F fly ash results in 114% enhancement in compressive strength and 69% reduction in permeability. In addition, mixes with 0.05% of total solids replaced with polypropylene fiber (by weight) show 25% reduction in compressive strength and 500% increase in permeability in comparison to FC mixes without fly ash and polypropylene fibers. Thirdly, considering mixes with addition of fly ash and polypropylene fibers both, it is found that the effect of fly ash is more predominant from strength perspective than fiber. From permeability perspective however, the fibers control the permeability significantly due to their higher impact on microstructure of FC.

Lightweight stiffness-dominated acoustic metamaterial barrier for low-frequency sound

In this study, we experimentally demonstrate a class of lightweight acoustic metamaterial barriers that block low-frequency sound. The acoustic metamaterial barrier is composed of a thin rubber membrane coated over a stiff honeycomb plate. Our findings, combined with high-fidelity finite element simulations, demonstrate that the sound insulation performance of the acoustic metamaterial surpasses the mass law in three distinct frequency ranges: (a) the stiffness law dominates insulation up to 140 Hz, (b) degeneracy and destructive superposition of high-order natural modes dominate within the frequency range of 300–500 Hz, and (c) destructive interference between high-order resonance and membrane resonance dominates in the frequency range of 800–1200 Hz. Notably, our study highlights the potential of high-order shear vibration of the periodic structure for the resonant bending waves of the honeycomb cell that coincide with the wavelengths of longitudinal sound waves in air, thereby offering new design guidelines for lightweight acoustic metamaterial barriers. This study reports for the first time the coincidence of high-order and membrane resonance modes within the honeycomb cell by employing an accurate finite element model and experimental validation.

Macro-fiber composite-based tactors for haptic applications.

Haptic technology is a critical component of human-computer interfaces. Traditional haptic actuators are often unable to provide the broad frequency range and latency that is required in many advanced applications. To address this problem, we propose a new type of tactor based on macro-fiber composites (MFCs), composites of piezoelectric fibers. We propose a physics-based model for the actuation of the tactors, calibrated and validated through experiments. As our tactors are intended for haptic applications, we consider the role of skin on their response, an aspect seldom analyzed in the literature. In our experiments, we simulate the presence of the skin with a rubber membrane in contact with the tactor, with varying pre-stretch, mimicking different indentations of the tactor on the skin. The MFC-based tactor can always generate vibration amplitudes higher than skin discrimination thresholds, over the range of frequencies of interest for haptics, with a latency much smaller than traditional actuators. We theoretically investigate the effect of the skin on tactor vibrations, highlighting the individual roles of skin stiffness and damping and their combined effect across a series of pre-stretches. Our tactor shows promise in haptic applications, including assistive technologies and real-time feedback systems for training, safety, and monitoring.