Search Results (510)

In this paper, the role of the accumulated surface charge on the surfaces of nanoparticles on breakdown strength for liquid and solid dielectrics is presented. The breakdown strengths of a nanofilled liquid dielectric and a solid dielectric are evaluated. The evaluation was conducted considering different nanoparticle material types with different nanofiller loadings. Accordingly, the preparation of transformer oil nanofluid and silicone rubber nanocomposites was performed with different nanofillers of the same average particle size. Breakdown voltage was measured for all the prepared samples, both liquid and solid. The interpretation of the obtained results is presented. Full article

Hydrogen is a dangerous gas because it reacts very easily with oxygen to explode, and the accumulation of hydrogen in confined spaces is a safety hazard. Composites consisting of polymers and catalysts are a common getter, where the commonly used catalyst is usually commercial Pd/C. However, it often shows poor compatibility with polymers, making it difficult to form a homogeneous and stable composite. In this work, palladium chloride (PdCl₂) was converted to palladium (Pd) nanoparticles by reduction reaction and supported on graphene oxide (GO) modified by silanization. Spherical Pd nanoparticles with a size of 2–36 nm were uniformly distributed over the Silanized graphene oxide (SGO) matrix. When mixed with Pd/SGO, polymethylvinylsiloxane can be cured to silicone rubber (SR) by B₂O₃. Afterwards, the vinyl in the polymer can interact with hydrogen under the catalysis of Pd through the addition reaction, thus achieving the purpose of hydrogen elimination. The polymer elastomers with excellent self-healing properties and improved hydrogen elimination performance were prepared and were superior to the commercial Pd/C. In addition, excellent environmental adaptability was also demonstrated. The new getter SR-Pd/SGO provides a new avenue for developing polymer getters with superior properties. Full article

In recent years, flexible continuum robots have been substantially developed. Absolute nodal coordinates formulation (ANCF) gives a feasible path for simulating the behavior of flexible robots. However, the model of finger-shaped robots is often regarded as a cylinder and characterized by a beam element. Obviously, this is short of characterizing the geometrical feature of fingers in detail, especially under bending conditions. Additionally, for the lower-order plate element, it is hard to characterize the bending behavior of the flexible finger due to fewer nodes; a higher-order plate element often requires an extremely long computing time. In this work, an improved ANCF lower-order plate element is used to increase the accuracy of the Yeoh model and characterize the geometrical structure of silicone rubber fingers, taking into particular consideration the effect of volume locks and multi-body system constraints. Since it is a kind of lower-order plate element, essentially, the computing time is nearly the same as that of conventional lower-order plate elements. The validity of this model was verified by comparing it with the results of the published reference. The flexible finger, manufactured using silicone rubber, is characterized by the novel ANCF lower-order plate element, whereby its mechanical deformation and bending behavior are simulated both efficiently and accurately. Compared to the ANCF beam element, conventional lower-order plate element, and higher-order plate element, the novel plate element in this paper characterizes the external contour of the finger better, reflects bending behavior more realistically, and converges in less computing time. Full article

The migration of low-molecular-weight components of polysiloxane (small molecules) to the surface of high-temperature-vulcanizing silicone rubber (HTV-SR) ensures its hydrophobicity and tends to coat the surface of pollutants, which would otherwise lower hydrophobicity. The transferability of hydrophobicity will ensure the insulator maintains its higher hydrophobicity after being coated with surface pollutants, thus providing the insulator with higher pollution flashover voltage. This migration process takes a certain time, and in this paper, the time characteristics of hydrophobicity transfer from HTV-SR coated with ten different inert materials were investigated. Ten different inert materials have different migration times and static contact angles, possibly due to the influence of pollution material characteristics on the characteristics of small-molecule migration. Thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FTIR), and gas chromatography–mass spectrometry (GC–MS) were used to analyze the migration of small molecules to the polluted surface. The evidence of small molecules migrating to the surface of the polluted material over time was found. Furthermore, the influence of pollution material characteristics on small-molecule migration was analyzed via SEM, specific surface area, and porosity. On that basis, the hydrophobicity migration characteristics of mixtures of kaolin and kieselguhr were also studied and compared to determine how best to simulate the behavior of natural pollution using artificial pollutants and their mixtures. Full article

The location of the electric motor (EM) inside the transmission in an electric vehicle requires the compatibility of the automatic transmission fluids (ATFs) with the materials of the EM and the transmission. This work studies the compatibility of four conventional ATFs with three elastomers: fluoroelastomer (FKM), ethylene-propylene-diene monomer (EPDM), and vinyl-methyl silicone rubber (silicone). Changes in volume, hardness, tensile strength, and elongation at break of the elastomers after aging in the ATFs were measured, and additional Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric and derivative thermogravimetric (TGA and DTGA) tests were performed. The four ATFs showed high or medium compatibility with FKM and silicone, and low compatibility with EPDM. This low compatibility was related to changes in the composition and crystalline structure of the elastomer. The non-compatibility of the EPDM with the oils from Group III was also proven. Full article

Simultaneously exhibiting both a magnetic response and piezoelectric energy harvesting in magneto-rheological elastomers (MREs) is a win–win situation in a soft (hardness below 65) composite-based device. In the present work, composites based on iron oxide (Fe₂O₃) were prepared and exhibited a magnetic response; other composites based on the electrically conductive reinforcing nanofiller, graphite nanoplatelets (GNP), were also prepared and exhibited energy generation. A piezoelectric energy-harvesting device based on composites exhibited an impressive voltage of ~10 V and demonstrated a high durability of 0.5 million cycles. These nanofillers were added in room temperature vulcanized silicone rubber (RTV-SR) and their magnetic response and piezoelectric energy generation were studied both in single and hybrid form. The hybrid composite consisted of 10 per hundred parts of rubber (phr) of Fe₂O₃ and 10 phr of GNP. The experimental data show that the compressive modulus of the composites was 1.71 MPa (virgin), 2.73 (GNP), 2.65 MPa (Fe₂O₃), and 3.54 MPa (hybrid). Similarly, the fracture strain of the composites was 89% (virgin), 109% (GNP), 105% (Fe₂O₃), 133% (hybrid). Moreover, cyclic multi-hysteresis tests show that the hybrid composites exhibiting higher mechanical properties had the shortcoming of showing higher dissipation losses. In the end, this work demonstrates a rubber composite that provides an energy-harvesting device with an impressive voltage, high durability, and MREs with high magnetic sensitivity. Full article

This review considers the key advantages of using supercritical carbon dioxide as a solvent for systems with organosilicon compounds. Organosilicon polymeric materials synthesis as well as the creation and modification of composites based on them are discussed. Polydimethylsiloxane and analogues used as polymerization stabilizers and nucleation promoters in pore formation processes are analyzed as well. Full article

The development of environmentally benign silicone composites from sugar palm fibre and silicone rubber was carried out in this study. The mechanical, physical, and morphological properties of the composites with sugar palm (SP) filler contents ranging from 0% to 16% by weight (wt%) were investigated. Based on the uniaxial tensile tests, it was found that the increment in filler content led to higher stiffness. Via dynamic mechanical analysis (DMA), the viscoelastic properties of the silicone biocomposite showed that the storage modulus and loss modulus increased with the increment in filler content. The physical properties also revealed that the density and moisture absorption rate increased as the filler content increased. Inversely, the swelling effect of the highest filler content (16 wt%) revealed that its swelling ratio possessed the lowest rate as compared to the lower filler addition and pure silicone rubber. The morphological analysis via scanning electron microscopy (SEM) showed that the sugar palm filler was evenly dispersed and no agglomeration could be seen. Thus, it can be concluded that the addition of sugar palm filler enhanced the stiffness property of silicone rubber. These new findings could contribute positively to the employment of natural fibres as reinforcements for greener biocomposite materials. Full article

Materials that exhibit highly nonlinear behaviour are intricate to study. This is due to their physical properties, as they possess a very large deformation. Silicone rubber is among the materials that can be classified as possessing such characteristics, despite their being soft and frequently applied in medical applications. Due to their low mechanical properties, however, it is believed that a filler addition could enhance them. This study, therefore, aims to investigate the effect of the addition of bamboo cellulosic filler to silicone rubber in terms of its compressive properties in order to quantify its material constants using the hyperelastic theory, specifically the Neo-Hookean and Mooney–Rivlin models. The specimens’ compressive properties were also compared between specimens immersed in seawater and those not immersed in seawater. The findings showed that the compressive properties, stiffness, and compressive strength of the bamboo cellulosic fibre reinforced the silicone rubber biocomposites, improved with higher bamboo filler addition. Specimens immersed in seawater showed that they can withstand a compressive load of up to 83.16 kPa in comparison to specimens not immersed in seawater (up to 79.8 kPa). Using the hyperelastic constitutive models, the Mooney–Rivlin model displayed the most accurate performance curve fit with the experimental compression data with an R² of up to 0.9999. The material constant values also revealed that the specimens immersed in seawater improved in stiffness property, as the C₁ material constant values are higher than for the specimens not immersed in seawater. From these findings, this study has shown that bamboo cellulosic filler added into silicone rubber enhances the material’s compressive properties and that the rubber further improves with immersion in seawater. Thus, these findings contribute significantly towards knowledge of bamboo cellulosic fibre–reinforced silicone rubber biocomposite materials. Full article

This paper is based on the “Fast Pneumatic Mesh Driver” (FPN) used to couple a silicone rubber soft body with a rigid skeleton. A rigid-flexible coupling soft-body human-like finger design scheme is proposed to solve the problem of low load on the soft-body gripping hand. The second-order Yeoh model is used to establish the statics model of the soft humanoid finger, and the ABAQUS simulation analysis software is used for correction and comparison to verify the feasibility of the soft humanoid finger bending. The thickness of the driver cavity and the confining strain layer were determined by finite element simulation. The mold casting process is used to complete the preparation of human-like fingers and design a pneumatic control system for experiments combined with 3D printing technology. The experimental results show that the proposed rigid-flexible coupling soft body imitating the human finger structure can realize the corresponding actions, such as the multi-joint bending and side swinging, of human fingers. Compared with the traditional pure soft-body finger, the fingertip output force is significantly improved. The optimal design and simulation analysis of the human gripper and the feasibility of the application have practical guiding significance. Full article

Adaptive structures based on fiber-rubber composites with integrated Shape Memory Alloys are promising candidates for active deformation tasks in the fields of soft robotics and human-machine interactions. Solid-body hinges improve the deformation behavior of such composite structures. Textile technology enables the user to develop reinforcement fabrics with tailored properties suited for hinged actuation mechanisms. In this work, flat knitting technology is used to create biaxially reinforced, multilayer knitted fabrics with hinge areas and integrated Shape Memory Alloy wires. The hinge areas are achieved by dividing the structures into sections and varying the configuration and number of reinforcement fibers from section to section. The fabrics are then infused with silicone, producing a fiber-rubber composite specimen. An existing simulation model is enhanced to account for the hinges present within the specimen. The active deformation behavior of the resulting structures is then tested experimentally, showing large deformations of the hinged specimens. Finally, the simulation results are compared to the experimental results, showing deformations deviating from the experiments due to the developmental stage of the specimens. Future work will benefit from the findings by improving the deformation behavior of the specimens and enabling further development for first applications. Full article

To reduce the material costs as well as the density of Liquid Silicone Rubber (LSR), LSR foams can be produced in an injection molding process. Expandable thermoplastic microspheres can be used as blowing agents. This publication deals with the analysis of the cell structure of these LSR foams. For this purpose, cylindrical disks are injection molded and examined for their cell structure as a function of different proportions of microspheres using a scanning electron spectroscope. In addition, the density of the samples is determined. It was found that a very homogeneous cell structure is produced in this process, that heat transport has a significant influence on the expansion of the microspheres, and that the formation of a filler network limits the expansion at higher proportions of blowing agent. Full article

In this study, we present a systematic scheme to identify the material parameters in constitutive model of hyperelastic materials such as rubber. This approach is proposed based on the combined use of general regression neural network, experimental data and finite element analysis. In detail, the finite element analysis is carried out to provide the learning samples of GRNN model, while the results observed from the uniaxial tensile test is set as the target value of GRNN model. A problem involving parameters identification of silicone rubber material is described for validation. The results show that the proposed GRNN-based approach has the characteristics of high universality and good precision, and can be extended to parameters identification of complex rubber-like hyperelastic material constitutive. Full article

In recent years, soft and flexible strain sensors have found application in wearable devices for monitoring human motion and physiological parameters. Conductive textile-based sensors are good candidates for developing these sensors. However, their robust electro-mechanical connection and susceptibility to environmental factors are still an open challenge to date. In this work, the manufacturing process of a silicone-textile composite resistive strain sensor based on a conductive resistive textile encapsulated into a dual-layer of silicone rubber is reported. In the working range typical of biomedical applications (up to 50%), the proposed flexible, skin-safe and moisture resistant strain sensor exhibited high sensitivity (gauge factor of −1.1), low hysteresis (maximum hysteresis error 3.2%) and ease of shaping in custom designs through a facile manufacturing process. To test the developed flexible sensor, two applicative scenarios covering the whole working range have been considered: the recording of the chest wall expansion during respiratory activity and the capture of the elbow flexion/extension movements. Full article

Pollution flashover occurs when soluble and nonsoluble materials cover the surface of an insulator, and this may ultimately cause a reduction in its performance. In this paper, the common type of sodium chloride (NaCl) was used as a soluble pollutant (ESDD) and kaolin as a nonsoluble pollutant (NSDD). Samples of silicone rubber (SiR) insulators were selected for this study and fabricated at the Advanced High Voltage Engineering Research Centre (AHIVEC) at Cardiff University. The samples were preconditioned and polluted according to standard specifications. Additionally, the AC voltage ramp technique was used to achieve flashover (FOV) voltage with different pollution levels. The aim of this work was to investigate the effect of nonsoluble materials on flashover characteristics to understand their interaction with dry-band arcs by using FOV electrical equations and experimental data. The test results show that the FOV voltage of the silicone rubber insulator substantially decreased with the increase in both ESDD and NSDD values. It was also identified from these results that the dry-band arcs were considerably influenced by both ESDD and NSDD levels. This impact can be quantified by determining the variation of discharge parameters (N, n). Based on the FOV equations and experimental data, a mathematical model was suggested, taking into account the effect of both ESDD and NSDD. Full article