Three-dimensional Braided Composite Mechanical Properties Of Cae Technology Base

A new method of mechanical analysis has been presented for predicting the properties of textile composites with complex microstructure. And then, the elastic properties of three-dimensional (3-D) braided composites are obtained using the computer aided engineering(CAE) technology.In this thesis, a kind of geometrical model built by the least square approximation method is used, which is oriented in the same reference frame as the perform, and its height is equal to the braiding pitch, hi the unit-cell, the braiding yarns interlock with four different orientations, here Y is the braiding angle (between yarn and X-axis), and 4> is the horizontal angle ( between the projection of the braiding yarn into the Y-Z plane and Y-axis).Considering the geometrical model above, a local/global averaging method is proposed for analyzing the 3-D braided composites based on the assumptions of Voigt and Reuss, and the mechanical model fitting for local/global averaging method is constructed.. Firstly, in an infinitely small element, the stress-strain relations for each material can be expressed using the in-plane and the out-plane components. Assuming the iso-strain condition hi in-plane and iso-stress condition hi out-plane, then the local stiflhess matrix C* can be calculated by volume averaging along Z-direction. Secondly, assuming the iso-stress condition in in-plane and iso-strain condition hi out-plane, the global stiflhess matrix C can be obtained by volume averaging in the XOY plane. This method can be used to predict the mechanical properties of textile composites with complex microstructure.Furthermore, a CAE package is compiled by Visual Fortran to be applied in the prediction of the properties of 3-D braided composites. Inputting the braiding parameters required, the software can calculate the Young's Moduli quickly and accurately, which is hi a good agreement with the experimental results.hi addition, utilizing the finite element software MARC, the bending properties of I-shaped beam are analyzed. On the friendly graphic interface MENTAT, analytical process is taken according to finite element theory. Defining material properties in which is to link User Subroutine with MARC. Thus, it provides the way to developing other User Subroutine of MARC.