ANALYTICAL METHODS FOR TEXTILE COMPOSITES
the orientation of the yarns. The mandrel can vary in cross-section, with the braided fabric
conforming to the mandrel shape (as long as the perimeter is not re-entrant).
Figure 2-3. Maypole braider for production of 2D bias braid.
Fixed, straight axial yarns can also be introduced at the center of orbit of the braider
yarn carriers. The braider yarns lock the axial yarns into the fabric, forming a triaxial braid,
i.e. a braid reinforced in three in-plane directions.
A flat braided sheet can be formed by cutting the cylindrical sheet from the mandrel
and stretching it out flat.
2.1.2.3 3D Braiding
3D braiding can produce thick, net section preforms, in which tows are so
intertwined that there may be no distinct layers. In one process, the yarn carriers (bobbins)
are arranged in a two-dimensional grid, often in rectangular or annular patterns, sometimes
in the cross-sectional shape of the final component. Multiple rectangles can be concatenated
to form more complex cross-sections. Braiding proceeds by alternately exchanging rows
and columns of yarn carriers. While the tracks that move yarn carriers return to their
original positions after a small number of steps, the carriers themselves can follow complex
paths by passing from one track to another.
