Prediction of material properties of biaxial and triaxial braided textile composites

Biaxial and triaxial braided composites are modeled using finite element methods to predict effective material properties: for biaxial braids, diamond pattern (1/1), regular pattern (2/2), and Hercules pattern (3/3) are modeled, while for triaxial braids, a regular pattern (2/2) is modeled. A micromechanical approach is adopted to calculate material properties of the tows, which are critical compositions of braided composites. By applying periodical boundary conditions (PBC), four representative unit cells (RUC) in correspondence to the four types of braids are analyzed and compared. Subsequently, effective material properties are obtained with the braiding angle varying from 15 degrees to 75 degrees with an increment of 5 degrees, from which the variation of the engineering constants with the braiding angle is studied. The prediction results are compared with the experimental values for two material systems, and good agreement is achieved.