Mechanical Properties Of Rubber Materials Research Articles

Enhancing mechanical properties and stabilising the structure of epoxide natural rubber using non-covalent interactions: Metal–ligand coordination and hydrogen bonding

Non-covalent interactions can enhance the mechanical properties of rubber materials diversifying potential applications. Epoxidized natural rubber (ENR), derived by modifying natural rubber (NR), can establish metal–ligand (M-L) coordination and H-bonding. In this research, ENR samples with non-covalent interactions were prepared by adding (i) sodium alginate (Alg) with FeCl3 and (ii) dopamine (D) with FeCl3. Both H-bonding and M-L coordination were detected by FTIR and Raman spectroscopy. The overall mechanical properties were increased due to non-covalent interactions, especially self-healing performance, which reached 60 %. From the mechanical stability data, storage hardening phenomenon of ENR was explained for the first time. These samples exhibited constant Mooney viscosity as a function of time. Furthermore, the effect of M-L coordination in dopamine modified samples were the strongest due to dopamine was grafted on ENR molecules. Therefore, this research provides a possible new way to stabilise the structure and enhance the mechanical properties of ENRs.

Temperature dependent tensile fracture strength model of rubber materials based on Mooney-Rivlin model

With the increasingly widespread application of rubber in many fields, the demand for quantitative characterization of temperature dependent mechanical properties in service environments over a wide temperature range is increasing. Tensile fracture strength is one of the most important mechanical properties of rubber materials, but its temperature dependent model without fitting parameters is still rarely reported. In this work, based on Mooney-Rivlin hyperelastic constitutive model, a strain energy expression that explicitly includes tensile fracture strength is derived, and a temperature dependent tensile fracture strength model for rubber materials without fitting parameters is further developed in combination with the Force-Heat Equivalence Energy Density Principle. The prediction results of the model in a wide temperature range are in good agreement with the experimental results. Furthermore, a quantitative analysis of the effect of elastic modulus on tensile fracture strength at different temperatures is conducted. Finally, based on the above conclusions, some useful suggestions on the selection of rubber materials for service in a wide temperature range are proposed.

Compressive stress-hydrothermal aging behavior and constitutive model of shield tunnel EPDM rubber material

The damage and aging of the ethylene-propylene-diene monomer (EPDM) rubber material significantly impact the attenuation of the shield tunnel's waterproof performance. Furthermore, the compressive stress acting on the rubber material will further exacerbate this consequence. Therefore, it is necessary to explore the time-dependent properties of rubber under compressive stress. In this study, the EPDM rubber was subjected to compressive stress-hydrothermal aging (CS-HA) test at different pre-compression strains, temperatures, and time according to the application environment of the shield tunnel. The rule of compression set (CS) and the variation rule of mechanical properties of rubber materials after aging were investigated, and the reasons for these rules were analyzed. According to the rule of rubber material performance degradation, a constitutive model of EPDM rubber for shield tunnel segment squeezing environment was proposed. Using compression set as the index of material performance deterioration degree, the time and temperature conversion relationship between laboratory aging and service environment aging of the EPDM rubber segment joint was obtained. Furthermore, based on the constitutive model and related parameter expressions proposed in this paper, the attenuation rule of rubber mechanical properties and residual properties was obtained. It was proposed that the service performance of EPDM rubber under compressive stress should be considered when setting the pre-tightening force during the construction of the shield tunnel, and a reasonable pre-compression force should be adopted. This work provides an effective test method and constitutive model for predicting the time-dependent characteristics of the mechanical properties of rubber materials under compressive stress.

Crack propagation behaviors in a nanoparticle‐filled rubber studied by in situ tensile electron microscopy

AbstractAlthough fracture resistance is critical for rubber materials, the fracture mechanisms are poorly understood from a microscopic perspective. In this study, a crack propagation process in rubber with silica nanoparticles, which is commonly used to enhance the mechanical properties of rubber materials, was successfully observed in situ with nanoscale resolution using transmission electron microscopy (TEM). The consecutive time‐sliced TEM images clarified that the crack tip propagated along the interfaces between the rubber matrix and aggregates of silica nanoparticles (rubber‐aggregate interfaces). Moreover, the path and propagation rate of the crack were significantly affected by the heterogeneous distribution of the silica aggregates, which resulted in a “stick–slip” propagation behavior of the crack tip. Detailed spatial strain analysis revealed that the local maximum principal strain () around the crack tip was nonuniform. The crack tip propagated through regions with large , delaminating the rubber‐aggregate interfaces. This study successfully demonstrated that the heterogeneous distribution of nanoparticles significantly affects the fracture behavior of nanoparticle‐filled rubbers.

Study on the Free Vibration of a Rubber Band Oscillator

Through theoretical analysis and experimental verification of the motion of a rubber band oscillator, this paper proves that the new model for describing the mechanical properties of rubber is effective. It is pointed out that there are both elasticforce related to deformation and viscoelastic force related to deformation process in rubber. Within a certain range of deformation, elastic force satisfies Hooke’s theorem, and viscoelastic force is proportional to fractional derivative of elongation with time. The mechanical properties of rubber materials can be described by static elastic modulus (elastic coefficient), viscoelastic degree and viscoelastic coefficient.

Research on dynamic performance and influence of new mesh-hole elastic pads for railway fasteners in an extremely cold environment

In order to research the dynamic properties of elastic pads for a new pattern mesh-hole in an extremely cold environment, a three-dimensional finite element model of a mesh-hole rail pad is established. The Mooney-Rivlin constitutive model is used to simulate the mechanical properties of rubber materials at different temperatures, and the temperature-dependent characteristics of dynamic stiffness and damping coefficients of the mesh-hole rail pads are analyzed. Based on the vehicle-track coupling dynamic theory, the driving safety and stability properties of the rail pads at extremely cold climate are calculated and analyzed, and the applicability of the mesh-hole rail pads in the extremely cold environment is further evaluated. The research conclusions are as follows. The mesh-hole rail pads have significant low-temperature sensitivity. Namely, above −10°C, the dynamic stiffness and damping coefficients of rail pads are stable, while below this temperature, the dynamic stiffness and damping coefficients of elastic pads increase rapidly. The mesh-hole rail pad has an obvious influence on the dynamic performance of a vehicle-track system when the temperature changes. Namely, the wheel-rail force and wheel load reduction rate increase rapidly with the decrease in temperature, while the vertical dynamic displacement of the rail decreases. Under the extremely cold climate, the wheel load reduction rate of a high-speed passenger vehicle increases sharply, so the method for reducing train speed should be adopted to ensure the safety of train operation.

Characterization method of mechanical properties of rubber materials based on in-situ stereo finite-element-model updating

The mechanical properties of rubber materials changes with the service time and the material parameters have a corresponding relationship with the aging time. In this paper, an in-situ non-destructive characterization technique of structural material parameters evaluation was developed, and the mechanical parameters for the silicone rubber during accelerated aging were measured by the developed method. This work combined the local indentation method to develop an in-situ stereo Finite element model updating method based on optical full-field deformation measurement, which realized constitutive parameters inversion of rubber. By comparing the inversion results with the test results, the validity and accuracy of the developed method were proved. Then, this method was applied to determine changes in the mechanical parameters during rubber aging. The proposed method is potential to predict the remaining lifetime of rubber material by using the parameter-aging time curve.

Degradation Behavior of Rubber Materials for Elevator Safety According to Hydrothermal Aging

The degradation behavior of vulcanized rubber in elevator cabins for reducing vibrations was investigated by morphological and spectroscopy analysis. Thermal (85℃) and hydrothermal aging (85℃ and 85% relative humidity) was performed to determine the effects of heat and humidity on the mechanical properties of rubber materials. The international rubber hardness degree (IRHD), tensile strength, and elongation percentage of rubber materials were measured to better understand the stiffening of the surface with the degradation time. The degradation mechanism of rubber materials was classified into two types: an increase in cross-links and chain scission. When rubber components were used for 96 hr under hydrothermal stress conditions, their mechanical characteristics deteriorated rapidly according to the results of the thermal aging test due to complex degradation behavior. Hydrothermal aging affects the increase in not only cross-links but also chain scission of the polymer segment. Fourier transform infrared (FT-IR) spectroscopy of the specimens of hydrothermal aging revealed improvement in C-H bonding at 2916 and 2848 cm?1, and an increase in the peak intensity in the 1080 cm?1 due to C-O-C bonding. The reduced C-C bonding was associated with the decomposition of cross-links and elastic modulus, which affected the degradation of the matrix near the surface. Therefore, the mechanical properties decreased more rapidly after hydrothermal degradation than after thermal degradation. (Received December 28, 2012).

Evaluation for Mechanical Properties of Laminated Rubber Bearings Using Finite Element Analysis

In this paper, improvements of evaluation method for mechanical properties of rubber materials and isolated rubber bearings are shown. The displacement/pressure mixed method of hyperelastic material considering the viscoelastic effect, compressibility and the softening effect for high damping rubber is formulated in the first place. Also, simple numerical model of the high damping rubber is proposed from experimental results. Mechanical properties of both high damping and natural rubber are calculated by developed finite element code. Next, an evaluation methods for mechanical properties (horizontal, vertical and horizontal-vertical coupled properties) of the natural rubber bearings is shown.