CRACK PROPAGATION BEHAVIOR OF LATERALLY CONSTRAINED POLYMERS USED AS DIELECTRIC ELASTOMERS

Abstract

ABSTRACT Dielectric elastomer-based transducers are rapidly gaining importance with the syntheses of new polymers that can potentially be used as dielectric materials. However, these materials are always prone to fracture in the presence of cracks and flaws. Failures originate from flaws (or notches), and a complete fracture may take place due to the propagation of cracks. The present work investigates the crack propagation behavior of two popular polymers, VHB 4910 and Ecoflex, that are widely used as dielectric elastomers. In this case, tensile loadings in laterally constrained boundary conditions are considered. The average crack propagation speed for Ecoflex is higher than that for VHB, implying that Ecoflex will fail earlier than that of VHB under similar conditions. Moreover, with increasing notch lengths at a fixed strain rate, the average crack propagation speed decreases appreciably but becomes constant for comparatively larger notches. The results also conclude that the average crack propagation speed and normalized crack tip diameter remain higher for VHB than for Ecoflex for larger normalized notch lengths. It is observed that the average crack propagation speed increases with strain rates, whereas the normalized crack tip diameter is independent of strain rates. Experimental results obtained here will provide a useful comparative insight to understand the failure behavior of two polymers widely used as dielectric elastomers.