**3. Weaving**

Weaving is an ancient tradition which dates back over seven millenniums. In traditional weaving, there are two sets of yarns, perpendicular to each other, interlace to form a woven fabric. While one set of the yarns that run lengthwise along the weaving machine direction are called warp, the other set of the yarns that run transversely from one side to the other side of the machine are called weft (a.k.a. filling).

There are three basic motions in order to produce a fabric by ensuring the interlacing between warp and weft yarns. These three essential motions are; shedding, weft insertion and beat-up. For the continuation of weaving process, warp yarns have to be let-off and the produced fabric has to be taken-up. These necessary two motions are auxiliary movements that are warp let-off and fabric take-up.

Fig. 2. Basic motions on weaving machine (Lord&Mohamed, 1982).

In order to get different weave structures in traditional weaving, the movement of the warp yarns have to be controlled and changed before each weft insertion. To perform warp yarns movement on a loom, warps that follow the same interlacing pattern have to be grouped with the same frame called harness. In each harness, there are heddles that have an eye in the middle in which the warp yarns pass through. By lifting the harness up or down, the

weaving machine. Furthermore increasing the thickness of 3D woven fabrics while producing them with 2D weaving makes the costs more (Bogdanovich, 2007). Therefore, a new method of 3D woven fabric has been required and developed that is called 3D weaving. However, there is not only one method of 3D weaving. There are different methods of 3D weaving techniques according to the produced structure (angle interlock, orthogonal or fully interlaced 3D woven structures) and orientation of the yarn sets (uniaxial, multiaxial).

3D woven fabrics can be manufactured both with 2D and 3D weaving. The produced 3D fabrics are different from the properties point of view due to the differences in weaving methods. With 2D weaving, pleated or plissé fabric, terry fabrics, velvet fabrics and multilayer woven fabrics can be manufactured. Orthogonal 3D weave structures, fully interlaced 3D weave structures can be manufactured only by using special designed 3D weaving machines. In this section, manufacturing methods of different 3D woven fabrics

In the case of 2D weaving, two sets of perpendicular yarns are interlaced, irrespective of whether it is woven as single- or multi-layer. Another set of yarns, known as pile or binder yarns, can be introduced in the direction of fabric thickness. Fabrics could be produced by 2D techniques, with different sets of warp yarns in the ways mentioned below

2. By the use of multi-layer warp and weft or multi-layer ground warp, binder warp and

3. Conventional 2D process can also produce pile fabrics by utilising three sets of yarns,

Plissé or pleated material is a folded material, which can be achieved in different methods

i. Woven plissé: Produced by an additional device on a power loom; two warp systems of different tension achieve drape. Folding can also be achieved by suitable bindings. In

ii. Shrunk plissé is produced by the use of synthetic fibres with different shrinking

iii. Finishing plissé: The material is laid in folds, which are thermally fixed in so-called

Plissé or pleated woven fabrics can be produced on weaving machines equipped with two

Pleated woven fabric is produced on weaving machines equipped with a special pleated

warp beams in addition to a special pleated device or a variable beat up.

**4. 3D woven fabric production** 

(Gokarneshan & Alagirusamy; 2009):

**4.1.1 Production of Plissé or pleated fabrics** 

knit goods folds are created by stitching.

such as weaving, shrinking and finishing (Routte, 2002);

**4.1 Production of 3D woven fabrics with 2D weaving** 

1. By effective utilisation of warp and weft in single layer.

namely, single-layer ground warp, pile warp and weft.

will be mentioned.

weft.

properties.

device as follows:

pleating machines.

groups of warp yarns will move either upwards or downwards. Based on the pattern, there must be different harnesses for each group of warp yarns. In the case where each warp weaves a different pattern, a harness cord is provided for each heddle. There are four different shedding mechanisms to manipulate warp yarns; crank, cam, dobby and jacquard. Crank, cam or dobby mechanisms work together with harnesses. On the other hand in jacquard mechanism there are harness cords for each warp yarn, no harnesses. Thus patterning capability of jacquard mechanism is the highest among shedding mechanisms. By altering shedding motion, various weave structures such as plain, twill and satin can be produced.

When the shedding is opened based on the patterning, weft insertion takes place. Considering the weft insertion system of the weaving machine, weft insertion can be performed in different ways. In single-phase weaving machines, the weft yarn is carried from one side of the machine to the other side transversely by shuttle, projectile, rapier or jet systems. After the weft insertion, the reed beats up the last inserted weft and the produced fabric is taken up. For the next cycle, warp yarns have to be let off in order to open a shed. This cycle of operations are continued repeatedly to obtain the woven fabric in a sequence. This weaving process is called 2D weaving. Even this fabric production process is two dimensional (warp yarns are moved through fabric thickness and weft yarn is inserted at the open shed, consequently two orthogonal sets of yarns are interlaced), it is also possible to weave 3D woven fabrics known as multilayer structures. However, producing 3D woven fabrics with conventional weaving (2D weaving) does not mean that the process can be named 3D weaving. Because, the arrangement of the weaving motions unchanged whether a single warp sheet is used to produce sheet-like 2D fabrics or multiple warp sheets are used to produce multilayer 3D fabrics (Stig, 2009).

Fig. 3. Fabric production on conventional weaving machine (Khokar, 2001).

As previously mentioned, multilayer and angle interlock weave structures can be produced with 2D weaving. Unfortunately, composites made of 3D woven fabrics produced with 2D weaving have low in-plane stiffness and strength properties due to high crimp levels (Bogdanovich, 2007; Mohamed&Bogdanovich, 2009). A 3D woven fabric produced with 2D weaving is costly because only one weft insertion can take place during one cycle of

groups of warp yarns will move either upwards or downwards. Based on the pattern, there must be different harnesses for each group of warp yarns. In the case where each warp weaves a different pattern, a harness cord is provided for each heddle. There are four different shedding mechanisms to manipulate warp yarns; crank, cam, dobby and jacquard. Crank, cam or dobby mechanisms work together with harnesses. On the other hand in jacquard mechanism there are harness cords for each warp yarn, no harnesses. Thus patterning capability of jacquard mechanism is the highest among shedding mechanisms. By altering shedding motion, various weave structures such as plain, twill and satin can be

When the shedding is opened based on the patterning, weft insertion takes place. Considering the weft insertion system of the weaving machine, weft insertion can be performed in different ways. In single-phase weaving machines, the weft yarn is carried from one side of the machine to the other side transversely by shuttle, projectile, rapier or jet systems. After the weft insertion, the reed beats up the last inserted weft and the produced fabric is taken up. For the next cycle, warp yarns have to be let off in order to open a shed. This cycle of operations are continued repeatedly to obtain the woven fabric in a sequence. This weaving process is called 2D weaving. Even this fabric production process is two dimensional (warp yarns are moved through fabric thickness and weft yarn is inserted at the open shed, consequently two orthogonal sets of yarns are interlaced), it is also possible to weave 3D woven fabrics known as multilayer structures. However, producing 3D woven fabrics with conventional weaving (2D weaving) does not mean that the process can be named 3D weaving. Because, the arrangement of the weaving motions unchanged whether a single warp sheet is used to produce sheet-like 2D fabrics or multiple warp sheets are used

produced.

to produce multilayer 3D fabrics (Stig, 2009).

Fig. 3. Fabric production on conventional weaving machine (Khokar, 2001).

As previously mentioned, multilayer and angle interlock weave structures can be produced with 2D weaving. Unfortunately, composites made of 3D woven fabrics produced with 2D weaving have low in-plane stiffness and strength properties due to high crimp levels (Bogdanovich, 2007; Mohamed&Bogdanovich, 2009). A 3D woven fabric produced with 2D weaving is costly because only one weft insertion can take place during one cycle of weaving machine. Furthermore increasing the thickness of 3D woven fabrics while producing them with 2D weaving makes the costs more (Bogdanovich, 2007). Therefore, a new method of 3D woven fabric has been required and developed that is called 3D weaving. However, there is not only one method of 3D weaving. There are different methods of 3D weaving techniques according to the produced structure (angle interlock, orthogonal or fully interlaced 3D woven structures) and orientation of the yarn sets (uniaxial, multiaxial).
