Page 28 - 3D Fibre Reinforced Polymer Composites

Manufacture of 30 Fibre Preforms 17

Such a multilayer weaving loom is described by Yamamoto et a1 (1995). Examples of
such weave architectures that are currently capable of being manufactured using
multilayer weaving are illustrated in Figure 2.5. It should be noted that the illustrations
in Figure 2.5 show idealised architectures and often these can be very different from the
resultant preform architecture (Bannister et a1 1998). Tension within and friction
between the yarns, together with the initial weave parameters (yam size and twist, yarn
spacing, number of layers, etc) can all affect the final architecture and thus the
composite performance. As with conventional weaving, multilayer weaving is only
capable of producing fabrics with 0" and 90" in-plane yams, although the binder yarns
can be oriented at an angle. This tends to limit the use of these preforms as their shear
and torsional properties can be relatively low. Various 3D weaving techniques can
produce preforms with yarns at other angles although this requires the use of highly
specialised equipment, which will be discussed later.

Figure 2.4 Illustration of multilayer weaving

Figure 2.5 Typical multilayer yarn architectures