C. J. G. Plummer

Frequency dependent dielectric and mechanical behavior of elastomers for actuator applications

The low frequency mechanical and dielectric behavior of three different elastomers has been investigated by dynamic mechanical analysis and dielectric spectroscopy, with the aim of accounting for the frequency dependence of the characteristics of the corresponding dielectric elastomer actuators. Satisfactory agreement was obtained between the dynamic response of the actuators and a simple model based on the experimental data for the elastomers, assuming that the relatively large prestrains employed in the actuators to have little influence on the frequency dependence of their effective moduli. It was thus demonstrated 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 relatively minor influence on the actuator performance.

Effect of substrate crystalline morphology on the adhesion of plasma enhanced chemical vapor deposited thin silicon oxide coatings on polyamide

The influence of the surface morphology of semicrystalline polyamide 12 (PA12) on the adhesion of thin silicon oxide coatings is analyzed by means of uniaxial fragmentation tests and scanning local-acceleration microscopy (SLAM). Two types of PA12 substrates are investigated, namely, as-received PA12, which contains large spherulites, and quenched PA12, which has a relatively smooth, homogeneous surface structure. The adhesion of the coating is found to be identical for the two types of PA12. This indicates that plasma deposition of the oxide leads to an equivalent functionalization of the two types of surfaces. Nonetheless, localized delamination is observed at spherulite boundaries, and is argued to result from strain concentrations in the corresponding soft zones, revealed by SLAM measurements.

Dynamic Properties of Materials for Alpine Skis

The aim of the present research has been to quantify the influence of different materials on the global dynamic response of a ski. The properties of the individual constituent materials were characterized as a function of temperature and frequency using dynamic mechanical analysis. At the same time, the dynamic behavior of skis with different designs was investigated in a cold room at between −15 and 25 °C using specially developed apparatus. The results indicated the overall behavior to be influenced significantly by the polymeric topsheet, which showed a strong damping peak at about 0 °C. Elasticity-based FEA accounted well for the experimental results for the two first flexural vibrational modes of the skis. For higher modes, however, the viscoelastic nature of the polymeric components led to significant discrepancies between the predicted and observed behaviors.

Improved Materials for Dielectric Elastomer Actuators

Dielectric elastomers are an emerging class of electroactive polymers for electromechanical transduction. A broad application of dielectric elastomer actuators (DEA) is limited by the high voltage necessary to drive such devices. The development of novel elastomers offering better intrinsic electromechanical properties is one way to solve the problem. Therefore we prepared composites from thermoplastic or thermoset silicone elastomers and organic fillers as phthalocyanines or doped polyaniline (PANI). We studied the mechanical properties of silicones, synthesized, modified and characterized phthalocyanines and doped PANI. The influence of humidity onto the dielectric properties of CuPc(COOH)8 and ZnPc(COOH)8 was analyzed in detail. First measurements of silicone/PANI blends results in a hundredfold increase for the dielectric constant and an electromechanically strain of 8.5%.Copyright