**6. Comparison of preforms produced from 2D and 3D woven fabrics**

3D woven preforms were first developed in 1970's in an attempt to replace expensive high temperature metal alloys in aircraft brakes (Mouritz et al., 1999). In order to produce the preform of the brake component that was produced with 3D weaving process, Avco Corporation developed a specialised 3D weaving loom that performs weaving of hollow cylindrical preforms in which carbon fibres were aligned in radial, circumferential and axial directions. Research and development of 3D woven preforms remained at a low level until the mid-1980s since problems of using traditional 2D laminates in aircraft structures were encountered. One of the main problems that was faced at that time by the aircraft manufacturers was preforms produced from traditional 2D laminates were expensive to produce complex structures. The second problem was the low impact resistance of the traditional 2D laminates since aircraft maintenance engineers complaint of damage impacts from dropped tools during maintenance. These problems led more research and development in the field of composites produced from 3D woven fabrics. Nearly thirty years of know-how in the field of 3D weaving makes the preforms produced from 3D woven fabrics have superior properties compared to those of the preforms produced from traditional 2D laminates.

While preforms produced from traditional 2D laminates can only be processed into relatively simple and slightly curved shapes, preform for a composite component with a complicated shape can be made to the near-net-shape with 3D weaving. This ability of 3D weaving producing near-net-shape preforms can reduce the production costs thanks to the reduction in material wastage, need for machining and joining, and the amount of material handled during lay-up.

The second advantage of 3D weaving is preforms can be produced on conventional weaving looms only by making minor modifications to the machinery. This minimises the investment cost of producing preforms made of 3D woven fabrics. However, a range of specialised looms have been developed that have higher weaving speeds and are capable of weaving more complex shapes than traditional looms which have been modified (Mouritz et al., 1999).

The production of 3D woven fabrics on conventional weaving machines is an inefficient process since conventional 2D weaving machine inserts weft yarns one at a time. Contrary to the aforementioned situation, 3D weaving looms that are special designed to produce 3D woven fabrics allow simultaneously insert multiple layers of warp yarns and weft yarns. The simultaneous insertion of an entire column of weft yarns makes the linear productivity

Another important distinction is that in 2-D weaving process, yarns in the warp direction are passed through heddles, and must be pulled past neighbouring warp yarns, above or below the filling insertion. Repeated motions through the heddles and through other planes of warp tend to abrade fibres, especially brittle technical fibres. In the 3-D Weaving process individual warp planes do not pass through heddles, and are not forced to repeatedly cross neighbouring warp planes; accordingly, weaving-induced fibre damage in this case is

3D woven preforms were first developed in 1970's in an attempt to replace expensive high temperature metal alloys in aircraft brakes (Mouritz et al., 1999). In order to produce the preform of the brake component that was produced with 3D weaving process, Avco Corporation developed a specialised 3D weaving loom that performs weaving of hollow cylindrical preforms in which carbon fibres were aligned in radial, circumferential and axial directions. Research and development of 3D woven preforms remained at a low level until the mid-1980s since problems of using traditional 2D laminates in aircraft structures were encountered. One of the main problems that was faced at that time by the aircraft manufacturers was preforms produced from traditional 2D laminates were expensive to produce complex structures. The second problem was the low impact resistance of the traditional 2D laminates since aircraft maintenance engineers complaint of damage impacts from dropped tools during maintenance. These problems led more research and development in the field of composites produced from 3D woven fabrics. Nearly thirty years of know-how in the field of 3D weaving makes the preforms produced from 3D woven fabrics have superior properties compared to those of the preforms produced from

While preforms produced from traditional 2D laminates can only be processed into relatively simple and slightly curved shapes, preform for a composite component with a complicated shape can be made to the near-net-shape with 3D weaving. This ability of 3D weaving producing near-net-shape preforms can reduce the production costs thanks to the reduction in material wastage, need for machining and joining, and the amount of material

The second advantage of 3D weaving is preforms can be produced on conventional weaving looms only by making minor modifications to the machinery. This minimises the investment cost of producing preforms made of 3D woven fabrics. However, a range of specialised looms have been developed that have higher weaving speeds and are capable of weaving more complex shapes than traditional looms which have been modified (Mouritz et al., 1999).

**6. Comparison of preforms produced from 2D and 3D woven fabrics** 

**5. Advantages of 3D weaving process** 

significantly reduced (Lienhart, 2009).

traditional 2D laminates.

handled during lay-up.

of the 3D weaving process independent of layers (Lienhart, 2009).

With the use of 3D weaving, fabrics having different through-thickness properties can be produced. Amounts and types of binder yarns such as carbon, glass, Kevlar and ceramic fibres in through-thickness can be used to tailor the properties of a composite for a specific application (Mouritz et al., 1999).

Composites produced from 3D woven fabrics have higher delamination resistance, ballistic damage resistance and impact damage tolerance. These aforementioned properties have been a major problem in composites produced with traditional 2D weaving used in military aircraft structures (Mouritz et al., 1999).
