  The use of integrated MicroElectroMechanical systems (MEMS) is recently
spread thanks to their improved sensitivity, accuracy and reliability. Accurate
preliminary computations born from the need of high precision in the
manufacturing process of such devices. Piezoelectric materials are broadly
employed in this field as direct converters between mechanical and electrical
signals and some of these piezoelectric materials show pyroelectric features,
which involve thermo-electrical interactions. Pyroelectric bending actuators
are analyzed in the present study in plane conditions. They consists of active
PZT layers with in-plane polarization and a microstructured composite layer
characterized by a periodic microstructure where PZT fibers with an out of
plane polarization are immersed in a polymeric matrix. The constitutive law of
the composite layer at the macroscale has been determined by means of a
multi-field asymptotic homogenization technique, recently developed for
thermo-piezoelectric materials. Overall constitutive equations characterizing
the behavior of the microstructured layer at the macroscale have been derived
and the closed form of the overall constitutive tensors has been provided for
the equivalent first-order (Cauchy) homogenized continuum. Deflection of
unimorph and bimorph bender actuators has been investigated in relation to
their geometrical features, exploiting the out of plane piezoelectric
properties of the composite layer, which modify the stiffness of the entire
bender. An accurate description of benders behavior at the structural length
scale is of fundamental importance in order to design devices with high
performances. In this regard, the influence of the microstructure on the global
response of the actuator is investigated in the present study in order to
understand how the composite material can be tailored to meet specific design
requirements.
