INVESTIGADORES
IDIART Martin Ignacio
congresos y reuniones científicas
Título:
On the overall dissipative response of two-phase ferroelectric composites
Autor/es:
M. I. IDIART
Lugar:
Mendoza
Reunión:
Congreso; XX Congreso sobre Métodos Numéricos y sus Aplicaciones; 2013
Institución organizadora:
Asociación Argentina de Mecánica Computacional
Resumen:
Ferroelectricity refers to the capacity of
certain polar dielectrics to sustain a spontaneous electrical polarization that
can be altered by application of an external electric field. Since this change
in polarization is usually accompanied
by a mechanical deformation, ferroelectrics are electro-deformable materials
which find applications as sensors and actuators, energy harvesters, material damping
enhancers, and other microdevices. Ferroelectric ceramics such as barium
titanate and lead zirconate titanate are probably the most prominent examples
among this class of materials.
The search for electro-deformable materials with
specific combinations of properties not found in monolithic ferroelectrics has
recently motivated the development of an increasing variety of two-phase
ferroelectric composites. Composites with different purposes have been
produced, for instance, by dispersing ferroelectric ceramic particles in a
nonpolar polymeric matrix, by dispersing metallic particles in a ferroelectric
ceramic matrix, and by dispersing ferroelectric ceramic inclusions in a
ferroelectric polymeric matrix. Ferroelectric ceramics with controlled porosity
have also been produced for certain acoustic applications. Now, under
sufficiently high electric fields, all these composites exhibit significant
electrical hysteresis and dissipation. The main contribution to that overall
dissipation comes from the change of spontaneous polarization in the
ferroelectric phase, and its precise amount depends on the dielectric response
of each of the constituents and their geometrical arrangement. The purpose of
this work is to estimate theoretically such dependence.
To that end, the ferroelectric behavior of the
constituent phases is described via a stored energy density and a dissipation
potential in accordance with the theory of generalized standard materials. An
implicit time-discretization scheme is used to generate a variational
representation of the overall response in terms of a single incremental
potential. Estimates are then generated by constructing sequentially laminated
microgeometries of particulate type whose overall incremental potential can be
computed exactly. Because they are realizable, by construction, these estimates
are guaranteed to conform with any material constraints, to satisfy all
pertinent bounds, and to exhibit the required convexity properties with no
duality gap. Predictions for two-dimensional composites and porous
ferroelectrics are reported and discussed in the light of existing experimental
data.