Seminar Announcement

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Midwest Mechanics Seminar Series
Seminar Announcement Wednesday, October 26, 2005,
110 PM Alliant Energy-Lee Liu Auditorium, 1140
Howe Hall
Pedro Ponte Cantañeda Professor Department of
Mechanical Engineering and Applied
MechanicsUniversity of Pennsylvania
Effective behavior, microstructure evolution and
macroscopic instabilities in elastomeric
composites
Abstract This talk will present the application
of a recently developed second-order
homogenization method to generate estimates for
effective behavior, microstructure evolution and
loss of ellipticity in hyperelastic composites
with random and periodic microstructures that are
subjected to finite deformations. Two extreme
cases are considered that are illustrative of the
physics of the problem porous elastomers and
fiber-reinforced elastomers. The main concept
behind the method is the introduction of an
optimally selected linear comparison composite,
which can then be used to convert standard linear
homogenization estimates into new estimates for
the nonlinear hyperelastic composite. Explicit
results are provided for materials with isotropic
and strongly elliptic constituents. It is found
that their overall behavior may lose ellipticity
at sufficiently large deformations, which
corresponds to the possible development of shear
band-type instabilities. The reasons for this
result have been linked to the evolution of the
microstructure, which, under appropriate loading
conditions, can induce geometric softening
leading to the overall loss of ellipticity.
Coffee and casual discussion with the speaker
following the seminar Questions? Contact Ashraf
Bastawros (bastaw_at_iastate.edu)