Page 35 - 3D Fibre Reinforced Polymer Composites

24 30 Fibre Reinforced Polymer Composites

Figure 2.11 Illustration of Distance Fabric material

2.3.1 2D Braiding
The standard 2D braiding technique is illustrated in Figure 2.12, which demonstrates
how the counter-rotation of two sets of yarn carriers around a circular frame forms the
braided fabric. This movement of the yarn carriers is accomplished through the use of
“horn gears” which allow the transfer of the carriers from one gear to the next. The
fabric architecture produced by this process is highly interlinked and normally in a flat
or tubular form, as shown in Figure 2.13. The style and size of the braided fabric and its
production rate are dependent upon a number of variables (Soebroto et al., 1990),
amongst which are the number of braiding yarns, their size and the required braid angle.
The equations that relate these variables dictate the range of braided fabric that can be
produced on any one machine. Generally though, braiding is more suited to the
manufacture of narrow width flat or tubular fabric and not as capable as weaving in the
production of large volumes of wide fabrics. Typical large braiding machines tend to
have 144 yarn carriers, however, larger braiding machines, up to 800 carriers (A&P
Technology, 1997), are now coming into commercial operation and this will allow
braided fabric to be produced in larger diameters and at a faster throughput.
The braiding process can also be used with mandrels to make quite intricate preform
shapes (see Figure 2.14). By suitable design of the mandrel and selection of the braiding
parameters, braided fabric can be produced over the top of mandrels that vary in cross-
sectional shape or dimension along their length. Attachment points or holes can also be
braided into the preform, thus saving extra steps in the component finishing, and
improving the mechanical performance of the component by retaining an unbroken fibre
reinforcement at the attachment site. Thus, within the limitations of fabric size and
production rate, braiding is seen to be a very flexible process in the range of products