OVERVIEW OF TEXTILES
Three-dimensional braids can be characterized as two-step, four-step, and multi-
step processes. The number of steps refers to the number of movements required for the
yarn carrriers to return to their original positions. The two-step process is illustrated in Fig.
2-4. The braider yarns move in opposite directions along alternating diagonals formed by
the axial yarns.
Axial Yarn
Figure 2-4. Two-step braiding process.
The four-step process is shown in Fig. 2-5. In the first step, alternate columns are
shifted a prescribed relative distance. The next step involves shifting alternate rows. The
third and fourth steps permute the columns and rows to return the device to its original
configuration (although an individual bobbin does not return to its original position in one
cycle). The 4-step process is a general term for processes that include Omniweave,
Magnaweave, SCOUDID, and Cartesian braiding. Multistep braiding is a generalization of
the four-step procedure which involves individual control over columns and rows.
The relative shifting distance of the rows and columns also controls the braid
pattern. In a 1x1 braid, the shifting distances of the rows and columns are equal. More
complex braid patterns are possible.
3D braiding machines use a beater to control compaction as the yarns interlace. The
degree of compaction is a process variable which affects the resulting fabric geometry.
2.1.2.4 Uniweaves
The uniweave concept combines the mechanical property potential of unidirectional
tape with the handling advantages and low-cost fabrication of a fabric. Uniweave consists
of primary yarns of strong, stiff fibers woven together with fine yarns of glass or polyester
