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UBC Theses and Dissertations

Mechanical behavior of woven fabric composites under meso-level uncertainties : modeling and sensitivity analysis Komeili, Mojtaba


Unit cell modeling of the woven fabric composites is a strong tool for studying fabric behavior at meso-level. Among the suggested methods the three-dimensional finite element analysis is found to be promising and of greater interest to researchers in the field. However, due to the multi-scale nature and particular behavior of fibrous yarns, numerical procedures applicable to woven fabrics differ from conventional finite element routines. Moreover, from a practical point of view, most of the models in the literature focus on the ideal unit cells and excludes the meso-level uncertainty factors. On the other hand, experimental measurements indicate non-repeatability of test data which is a result of embedded inherent uncertainties. In this study, a finite element model capable of defining the representative volume element of a plain weave under homogenous loading has been created. Because of particular behavior of dry fabrics, a special constitutive material behaviour is defined via user-defined subroutines, which links to the solver of a finite element package (Abaqus). Material properties of yarns for dry glass fabrics are extracted by fitting their numerical responses to results of experiments. Subsequently, geometrical and material meso-level uncertainty factors are studied separately using two-level factorial designs. The output of runs are inserted into a commercial design package (Design Expert) for producing results in terms of probability plots, effects and percentage contribution of each factor and their interactions. Result shows that depending on the loading type, there are factors that show significant contribution toward the final response, whereas others are quite negligible. More elaboration on the design results provides informative conclusions regarding modeling of unit cells, as well as their behavior during different loading steps. These conclusions can be used in more comprehensive unit-cell homogenization formulations, as well as for defining appropriate tolerances for meso-level defects in woven fabric composites.

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