Title page for ETD etd-10132005-152550
|Type of Document
||Finite element micromechanics modeling of inelastic deformation of unidirectionally fiber-reinforced composites
|Griffin, Odis Hayden Jr.
|Barker, Richard M.
|Hyer, Michael W.
|Reddy, Junuthula N.
|Reifsnider, Kenneth L.
- Fibrous composites Models
- Micromechanics Models
- Deformations (Mechanics)
|Date of Defense
Part I (Efficient Endochronic Finite Element Analysis: an Example of a Cyclically Loaded
Boron/Aluminum Composite): A convenient and efficient algorithmic tangent matrix approach
has been developed for 3-D finite element (FE) analysis using the endochronic theory without
a yield surface. The underlying algorithm for integrating the endochronic constitutive equation
was derived by piecewise linearization of the plastic strain path. The approach was employed
to solve a micromechanics boundary value problem of a cyclically loaded unidirectional
boron/6061 aluminum composite. All the FE results consistently demonstrate superior numerical
stability and efficiency of the proposed method. Extensions of the method to
endochronic plasticity with a yield surface and to the plane stress case are also presented.
Part II (Simple and Unified Finite Element Formulation for Doubly Periodic Models: Applications
to Boron/Aluminum Composites): A simple and unified weak formulation and its convenient
FE implementation have been proposed. The weak formulation is valid for any doubly
periodic model under uniform 3-D macro-stress, and serves as a common rational foundation
of different FE approaches. The algorithmic tangent matrix approach for the endochronic
theory has been incorporated into the FE formulation to model isothermal, rate-independent
plastic macro-deformation of unidirectional fibrous composites with idealized two-phase
micro-structure and backed-out inelastic matrix properties. Methods for determining inelastic
material parameters of the matrix have been established. Numerical results for a B/6061 AI
composite subjected to on-axis and off-axis monotonic tensile loadings are in good agreement
with experimental data. The micromechanics model also shows the potential for quantitative
characterization of complicated cyclic behavior. Finally, some effects of model geometry on
overall plastic response of the B/6061 AI composite are discussed from the viewpoint of
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