Page 24 - 3D Fibre Reinforced Polymer Composites

Chapter 2

Manufacture of 3D Fibre Preforms

2.1 INTRODUCTION

In spite of the demonstrated advantages of 3D composites in their through-thickness and
impact performance, the use of these materials is not yet widespread. A major reason for
this limited use is related to the maturity of the manufacturing processes being used to
produce the preforms and the understanding and process control required to design and
cost-effectively manufacture a preform for a specific application. The manufacture of
3D fibre preforms for composite structures can be accomplished in a variety of ways,
however, all the processes that have been developed for composite applications are
essentially derived from one of the following four groups of traditional textile
procedures; Weaving, Braiding, Knitting and Stitching.
The aim of this chapter is not to give an exhaustive description of each
manufacturing process but rather to be a lay-persons introduction to the various
techniques being developed and used within the composites industry and to illustrate
their advantages and limitations.

2.2 WEAVING

Weaving is a process that is already used extensively within the composite industry as it
is the manufacturing method that produces the vast majority of the single-layer, broad-
cloth carbon and glass fabric that is currently used as a reinforcement material for
composite components. However, the same weaving equipment can also be used to
manufacture more intricate, net-shaped preforms that have a three-dimensional fibre
architecture. To understand how 3D preforms can be produced through weaving, it is
necessary to first understand the conventional 2D weaving process.

2.2.1 Conventional Weaving

Weaving is essentially the action of producing a fabric by the interlacing of two sets of
yarns: warp and weft. The basic weaving process is illustrated in Figure 2.1. The warp
yarns run in the machine direction, the 0" direction, and are fed into the weaving loom
from a source of yarn. This source can consist of a multitude of individual yarn
packages located on a frame (a creel), or as one or more tubular beams onto which the
necessary amount of yarn has been pre-wound (warp beams). The warp yarns may then
go through a series of bars or rollers to maintain their relative positioning and apply a
small amount of tension to the yarns, but are then fed through a lifting mechanism
which is the crucial stage in the weaving process. The lifting mechanism may be