Abstract: This paper investigates the influence of various
parameters on the behaviour of water droplets on polymeric surfaces
under high electric fields. An inclined plane test was carried out to
understand the droplet behaviour in strong electric field. Parameters
such as water droplet conductivity, droplet volume, polymeric
surface roughness and droplet positioning with respect to the
electrodes were studied. The flashover voltage is affected by all
aforementioned parameters. The droplet positioning is in some cases
more vital than the droplet volume. Surface damages were analysed
using Scanning Electron Microscopy (SEM) studies and by Energy
dispersive X-ray Analysis (EDAX). It is observes that magnitude of
discharge have direct influence on amount of surface da
Abstract: The breakdown strength characteristic of Low Density
Polyethylene films (LDPE) under DC voltage application and the
effect of water absorption have been studied. Mainly, our experiment
was investigated under two conditions; dry and heavy water
absorption. Under DC ramp voltage, the result found that the
breakdown strength under heavy water absorption has a lower value
than dry condition. In order to clarify the effect, the temperature rise of
film was observed using non contact thermograph until the occurrence
of the electrical breakdown and the conduction current of the sample
was also measured in correlation with the thermograph measurement.
From the observations, it was shown that under the heavy water
absorption, the hot spot in the samples appeared at lower voltage. At
the same voltage the temperature of the hot spot and conduction
current was higher than that under the dry condition. The measurement
result has a good correlation between the existence of a critical field
for conduction current and thermograph observation. In case of the
heavy water absorption, the occurrence of the threshold field was
earlier than the dry condition as result lead to higher of conduction
current and the temperature rise appears after threshold field was
significantly increased in increasing of field. The higher temperature
rise was caused by the higher current conduction as the result the
insulation leads to breakdown to the lower field application.
Abstract: New nondestructive technique, namely an inverse technique based on vibration tests, to characterize nonlinear mechanical properties of adhesive layers in sandwich composites is developed. An adhesive layer is described as a viscoelastic isotropic material with storage and loss moduli which are both frequency dependent values in wide frequency range. An optimization based on the planning of experiments and response surface technique to minimize the error functional is applied to decrease considerably the computational expenses. The developed identification technique has been tested on aluminum panels and successfully applied to characterize viscoelastic material properties of 3M damping polymer ISD-112 used as a core material in sandwich panels.