Sawant, Sourabh P. (2008-12). A Multi-scale Framework for Thermo-viscoelastic Analysis of Fiber Metal Laminates. Doctoral Dissertation.
Fiber Metal Laminates (FML) are hybrid composites with alternate layers of
orthotropic fiber reinforced polymers (FRP) and isotropic metal alloys. FML can exhibit
a nonlinear thermo-viscoelastic behavior under the influence of external mechanical and
non-mechanical stimuli. Such a behavior can be due to the stress and temperature
dependent viscoelastic response in one or all of its constituents, namely, the fiber and
matrix (within the FRP layers) or the metal layers. To predict the overall thermoviscoelastic
response of FML, it is necessary to incorporate different responses of the
individual constituents through a suitable multi-scale framework. A multi-scale
framework is developed to relate the constituent material responses to the structural
response of FML. The multi-scale framework consists of a micromechanical model of
unidirectional FRP for ply level homogenization. The upper (structural) level uses a
layered composite finite element (FE) with multiple integration points through the
thickness. The micromechanical model is implemented at these integration points.
Another approach (alternative to use of layered composite element) uses a sublaminate model to homogenize responses of the FRP and metal layers and integrate it to
continuum 3D or shell elements within the FE code. Thermo-viscoelastic constitutive
models of homogenous orthotropic materials are used at the lowest constituent level, i.e.,
fiber, matrix, and metal in the framework. The nonlinear and time dependent response of
the constituents requires the use of suitable correction algorithms (iterations) at various
levels in the multi-scale framework. The multi-scale framework can be efficiently used
to analyze nonlinear thermo-viscoelastic responses of FML structural components. The
multi-scale framework is also beneficial for designing FML materials and structures
since different FML performances can be first simulated by varying constituent
properties and microstructural arrangements.