Abstract:

 According to the 4-step braiding principle of preforms with complex rectangular cross section, the yarns paths in braided preforms with T section were analyzed. The spatial paths of yarns were speculated in accordance with the movenents of carriers. By the volume-control method, the special micro-structure model in the join region of composites with T section was established. Assuming the yarn coss-section is an ellipse and under other ideal conditions, the mathematical relationship between braiding parameters was deduced. The bending modulus was predicted by the MatLab program which was developed based on bending stiffness synthesis method. The results showed that bending modulus decreased with braiding angle increasing and increased with fiber volume increasing, and bending property of T beam of three dimensional five directional braided composites was superior to T beam of three dimensional four directional braided composites. Finally, compared with the experimental results, the validity of bending property predicted by this method was verified.

Key words: three-dimensional braideng, T section, micro-structure, bending property