Three-dimensional axial braided preforms: experimental determination of effects of structure-process parameters on unit cell

The aim of this study was to understand the effects of braid pattern and number of layers on 3D axial braided unit cell structures. Various unit cell based representative 3D axial braided preforms were developed. Data generated from these structures included unit cell dimensions, yarn angle and yarn length in the unit cell structures.It was shown that braid patterns affected the 3D axial braided unit cell structures. The 1 x 1 braid pattern made fully interconnected integral 3D axial braided unit cell structures, whereas the 2 x 1 braid pattern created disconnected braid layers which were connected to the structure edges. When the number of layers increased 3D axial braided unit cell thickness also increased. Braid pattern slightly affected the braided yarn angle. On the other hand, it was observed that the number of layers considerably affected the yarn length in the unit cell structure. Increasing the layer number from six to eight layers created a yarn path in the unit cell edge regions called the 'multilayer yarn length'. This yarn path was not observed below eight layer 3D axial braided unit cell structures. In jamming conditions, minimum jamming decreased the width of the unit cell structure but maximum jamming increased its width. In addition, minimum jamming decreased the surface angle of the unit cell structure, conversely, however, the maximum jamming increased the surface angle. Also, it was realized that jamming conditions influenced the density of the unit cell but did not affect the yarn length in the unit cell structures.