An improved finite-element model for simulating microwave processing of polymers and polymer-composites in a cylindrical resonant cavity
Abstract
A two-dimensional axisymmetric finite-element model
developed to simulate the microwave processing of polymers
and polymer-matrix composites in a cylindrical resonant cavity
was improved. The model consists of two submodels: the
electromagnetic submodel and the heat transfer submodel.
These two models are coupled together by the heat generation
term arising due to the microwave energy. A single finiteelement
program was written to implement the two submodels.
The heat generation term arising due to exothermic chemical
reactions was added to the heat conduction equation. The
model can now handle thermosetting resins as well as amorphous
thermoplastic polymers.
The governing equations for the electromagnetic submodel
are the complex, time-harmonic Maxwell's equations. Since an
axisymmetric model was developed, the material needs to be
axisymmetric and centered in the cavity. The material can
have anisotropic conductivity and permittivity. A separate
eigenvalue code was developed to compute the resonant
frequency for given cavity dimensions. This eigenvalue code
can account for non-homogenous material properties. The heat
transfer model is governed by the unsteady heat conduction
equation with the addition of heat generation terms
accounting for exothermic reactions and microwave energy.
All three types of heating: microwave only, convection only,
and combined microwave and convection heating can be
simulated by the electromagnetic and the heat transfer
models.
Several test cases were run to validate the programs.
The results of the eigenvalue code were compared to those
published in the literature. Simple test cases for which
analytical expressions are available were run to verify the
electromagnetic and heat transfer submodels. Excellent
agreement was obtained in all of the comparisons. Once the
programs were validated, several simulations were done to
study microwave processing and/or convective heating of
polymers and polymer-matrix composites. The materials
considered were nylon 66, S-glass/polycarbonate composite,
and S2-glass/epoxy composite. To study the advantages and
disadvantages of microwave processing over conventional
processing, comparisons were'made between the simulations of
the two processes.
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- Masters Theses [19644]