Microscale modeling of unidirectional fiber-reinforced composites

Fiber-Reinforced Composites (FRCs) represent one important class of structural materials whose microstructures can be designed and tailored in order to meet specific requirements. To improve design as well as to reduce the manufacturing costs, a profound understanding of the process-structure-property relationships in FRCs is required. Motivated by this need, the present work is devoted to the computational modeling of unidirectional FRCs with disordered microstructures, with the emphasis placed on the microscale analysis. More specifically, two topics are treated from the point of view of classical continuum mechanics; they are: (1) elastic response of unidirectional FRCs under transverse tensile loading and (2) permeability of disordered fiber arrays.; The Boundary Element Method (BEM) is applied to the solution of linear elasticity and creeping flow problems in complex domains. To overcome the storage and computational limitations associated with the direct BEM formulation, a parallelized version of the BEM has been implemented for distributed-memory parallel computers. The parallelization is based primarily on exploiting the performance and scalability of an optimized dense-matrix linear solver, ScaLAPACK. As the solution phase becomes the dominant part for large problems, the resulting parallel performance based on this parallelization strategy is satisfactory. Validation examples are provided.; Hundreds of simulations have been carried out based on the microstructures generated in computer using a Monte-Carlo procedure. A number of spatial descriptors, namely, nearest-neighbor distance functions, the measure of randomness, the second-order intensity function, the pair distribution function and the measure of deviation, are applied to quantitatively distinguish between these computer-generated microstructures.; The effects of fiber distribution and constituent properties on the elastic response of FRCs under transverse loading have been investigated. The transverse Young's modulus is found to be only slightly affected by the microstructural variability in hardcore microstructures, while it is more sensitive to the change of constituent properties. Strong correlations between the microstructural variability and the variability of stresses (first principal stress, radial stress, tangential stress, etc.) at the fiber/matrix interfaces have been found. In general, the stress level rises with an increase of the degree of local fiber aggregation.; The transverse permeability data have been obtained for disordered fiber arrays with the porosity and the degree of local disorder varied. The results are compared to earlier theoretical predictions as well as some experimental data. Good agreement has been found in the relevant cases. In the porosity range of practical interest (&phis; ∈ [0.45, 0.70]), the mean permeability behavior is found to follow a power function. Strong correlations between the microstructural variability and the variability in permeability data have also been found.