| A micromechanics model for the analysis of heterogeneous media containing elastic-plastic phases has been developed. This model is the result of the reconstruction of a recently developed micromechanics model called high-fidelity generalized method of cells (HFGMC) which, in turn, is superseded by this development. The reconstruction provides justification for the newly coined name finite-volume direct averaging micromechanics (FVDAM) model. The FVDAM model's theoretical framework is simplified by eliminating the two-level discretization employed in HFGMC's construction, and the definition of surface-averaged field quantities at the subdomain boundaries which makes possible the implementation of the local/global stiffness matrix approach. This approach eliminates the redundant continuity conditions employed in HFGMC, thereby reducing the size of the final system of equations by sixty percent which facilitates the accurate prediction of micro- and macro-level responses of composites with realistic microstructures. The theory is validated by a second look into architectural effects of fiber distribution and shape in unidirectional metal-matrix composites. Strengthening effects due to fiber clustering, previously documented for particulate composites, are recovered for unidirectional composites as well. Orientational effects in unidirectional composites are studied by performing the micromechanical analysis of unit cells, representative of a square array of fibers, in various coordinate systems obtained through rotation by an angle about the fiber axis. Comparison of the effective moduli, the average stress-strain response, and the stress fields with the corresponding results obtained using the generalized method of cells (GMC) extensively highlights GMC's shortcomings for a certain class of unidirectional composites. An experimental-analytical correlation involving off-axis loading of a unidirectional boron/aluminum composite shows that the residual stresses induced during processing and the concomitant material property and internal microstructure alterations substantially affect the subsequent mechanical response. Finally, the FVDAM model is employed to study the extent of deterioration in properties and behavior caused by two different damage modes in a SiC/Titanium composite. It is shown that fabrication induced radial fiber cracks which were earlier shown to be detrimental do not deteriorate composite mechanical response as much as interfacial debonding. |
