Mechanical analysis of 3D braided and woven composites using fiber-based continuum analysis

A numerical method was developed to reflect the microstructural changes of 3D textile composites and to predict their mechanical behavior based on continuum mechanics framework. The first step of the new method is to define the yarn orientation at every point of 3D textile composites and to update the yarn orientation using the deformation gradient. 3D textile composites are assumed as a combination of several uni-directional layers, each of which represents continuous distribution of fibers in the yarn direction. The tangent stiffness of each layer is then computed considering the yarn undulation, followed by calculation of the stress increment. Damage initiation is then evaluated using Puck's criterion and its propagation is implemented using modified ply discount method. The proposed numerical method was incorporated into commercial finite element software through a user material subroutine. The mechanical behavior of 3D braided and 3D woven composites was then predicted and compared with experimental to demonstrate the validity of the developed method.