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Experimental Characterization and Modeling of Bending Properties of Woven Fibrous Preforms

The properties of final composite parts depend on properties of dry preforms often being formed over doubly-curved shapes. In this case the fibrous preforms exhibit intricate large deformations, including shear, tension, and bending modes. Although the bending stiffness of fibrous materials is small, in shaping of preforms, when wrinkling occurs, its influence is important, not negligible and responsible for the wrinkles shape. Because of the structural and mechanical peculiarities, the experimental determination of bending properties of fibrous materials is rather complex, and there is no unique generally adopted test. A set of cantilever tests was chosen to be carried out in this study, in the form of sequence of different loading cases for one material that permits to reveal the eventual non-linear and non-elastic behavior of the material in bending. The tests were realized for glass fabrics with different types of weaving patterns and different areal weights. The effect of these parameters on the bending response is studied. The analysis of the data on bending of fabrics and bending of yarns, extracted from fabrics with the preserved undulated shape, is performed as well. The regions of the deformed specimens characterized by the largest scatter of experimental data are identified and analyzed. Besides, the analytical model based on corrugated plates theory, taking into account the undulated architecture of fabrics, is employed to characterize its bending properties, and to make a future comparison with the test results.