Search

A magnetorheological elastomer (MRE) is comprised of ferromagnetic particles aligned in a polymer medium by exposure to a magnetic field. The structures of the magnetic particles within elastomers are very sensitive to the external stimulus of either mechanical force or magnetic field, which result in multiresponse behaviors in a MRE. In this study, the sensing properties of MREs are investigated through experimentally characterizing the electrical properties of MRE materials and their interfaces with external stimulus (magnetic field or stress/strain). A phenomenological model is proposed to understand the impedance response of MREs under mechanical loads and magnetic fields. Results show that MRE samples exhibit significant changes in measured values of impedance and resistance in response to compressive deformation, as well as the applied magnetic field. [DOI: 10.1115/1.3160316]

Five composite ethylene propylene rubber/chlorosulfonated polyethylene (EPR/CSPE) insulated cables, a single composite cable with EPR/Neoprene, and a single Kerite insulated cable used in US nuclear power plants (NPP's) were evaluated. All of the cables had a CSPE outer jacket. To study the rate of degradation these cables were thermally aged at 110 and 120 [degrees]C until embrittlement of the composite insulation and /or outer jacket occurred. The degradation of the composite insulation and outer jackets was assessed by measuring elongation at break and indenter modulus. Both the indenter modulus and elongation values of the composite insulation and outer jacket exhibited excellent superposition when shifted using the time-temperature superposition principle. Regardless of whether or not the EPR insulation was bonded or non-bonded to the CSPE or Neoprene composite jacket thermal induced hardening and fusion of the composite jacket with EPR insulation was the cause for loss of flexibility of the composite wires. The aging rate of the composite insulated wires were not affected by the aging mode, namely, whether the composite wires were aged as a complete cable or with the jacket removed. However, the aging rate of the composite insulation and the outer jacket varied between different cables. Threshold indenter modulus values for successful Loss of Coolant Accident (LOCA) performance for each of the composite insulation and outer jacket was correlated with the thermal aging periods of the studies available in the literature. Close correlation was found between the thermal aging periods used for satisfactory LOCA performance and the time to reach 50% elongation of the composite insulation. Indenter modulus values of the composite insulation and outer jacket when the composite insulation decreases to 50% elongation is also provided. Index Terms--Hypalon, composite insulation, condition monitoring, cable indenter, elongation, thermal aging, LOCA performance.

A random resistor network (RRN) is used to study the electrical frequency response, including the unusual frequency dependent conductivity and multiple zero crossing of the dielectric function of highly conducting polymers. The negative values of epsilon and the low-energy structure of conducting polymers are described using RRN model and the calculated epsilon(omega) and sigma(omega) reproduce the main features of recent broadband optical experiments.

The wrinkled electrode was prepared through in situ deposition of polypyrrole onto the polyurethane elastomer film that was being uniaxially drawn. The bending actuation of the polyurethane film with the wrinkled electrode was improved more than twice that as compared with an unwrinkled one.

The article explains the development and the working of two microfluidic elastomeric autoregulatory devices, which are shown to act as a diode and a rectifier. The presence of the Newtonian fluids is shown to increase the density of these devices, hence making them useful for the various microfluidic logic circuitries.

The low frequency mechanical and dielectric behavior of three different elastomers is examined by dynamic mechanical analysis and dielectric spectroscopy in order to account for the frequency dependence of the characteristics of the corresponding dielectric elastomer actuators. The studies have shown that the frequency dependence of the actuator strain is dominated by that of the mechanical response of the elastomer and that the frequency dependence of the dielectric properties has a minor impact on the actuator performance.

An approach is described for designing dielectric elastomer actuators to optimize performance. The spring-roll actuator is used for the constructing the equations of state by modeling the actuator as a thermodynamic system of two degrees of freedom, identifying a set of design variables, and determining the region of allowable states according to many modes of failure.

A method is presented to laminate polymeric semiconducting films using an elastomeric support made of poly(di-methylsiloxane) (PDMS). These techniques have enabled the study of interfacial interactions in polymeric thin film transistors.