**4.1.3 Production of velvet fabrics**

Velvet fabrics are a class of pile fabrics which are divided into two as warp pile fabrics and weft pile fabrics known as velveteen according to the pile direction. Warp pile fabrics, also known as velvet, can be produced with two weaving methods; wire weaving technique and face to face (a.k.a. double plush) weaving technique. The advantage of face to face weaving technology is two fabrics are effectively woven at the same time one above the other joined together by the pile warp ends which cross from top cloth to bottom cloth according to the design and during this weaving process a knife situated between the two cloths continuously traverses the width of the fabric cutting the pile warp threads to create two cloths each with a cut warp pile surface. It is important to appreciate that a surface pile tuft is formed only when a pile end crosses from the top cloth into the bottom cloth and is cut on the loom by the traversing knife, and it is in this way that the surface pile design and colour are created. When it is not required on the surface of the fabric the pile is woven or 'incorporated' into the ground structure either in the top or bottom cloth (Fung&Hardcastle, 2001). Therefore, two different pile structures such as cut pile or loop pile can be obtained based on the pile cut or not.

Weaving machines based on face to face weaving technique are equipped with a 3 position shedding device (dobby or Jacquard machine), so as to form two overlapped and properly spaced out sheds and to permit to the pile warp to tie up the two fabrics together. Into each of the two shed a weft is inserted, usually by means of a pair of superimposed rods driven by the same gear (Castelli et al., 2000). With this technique, 3D woven spacer fabrics can also be easily woven.

harnesses in timed sequence with shuttle and reed movement is controlled with the shedding mechanism. Figure 12 represents the opened shedding for 21 and 22 warp yarns for weft insertion, shuttle (57). On the loom, totally three shuttles are used, one for each fabric ply. With arranging the fabric take-up motion in time sequenced with shedding

mechanism, this kind of fabric can be easily woven (Koppelman&Edward, 1963).

Fig. 12. Method of weaving a hollow 3D woven fabric on a conventional loom

Another design of 3D spacer fabric consisting of double ribs between the bottom and top layers or a 3D spacer fabric with an I shape can be produced on a conventional weaving machine (Rheaume, 1976). For the production of this type of fabric, the weaving loom has to have four separate shuttles and to include eight separate harnesses, each of which control different groups of warp yarns. Both of these two fabrics have the properties of foldability while being produced on the loom. When the fabrics are taken off the loom and get rid of the stresses, they open up and have the cross sections of V-shaped and I-shaped (Figure 13).

Fig. 11. Different views of spacer fabrics (Chen, 2011).

(Koppelman&Edward, 1963).

Fig. 10. Face to face weaving technique of producing velvet fabrics (Van De Wiele as cited in Chen, 2011).

In wire weaving technique, there is one set of ground warp, one set of ground weft and an extra set of warp yarns to form piles on the fabric. In order to produce a fabric with this technique, firstly a group of ground warps is raised according to the fabric pattern and the weft yarn is inserted to make its first interlacing with the ground warps. Then, pile warps are raised and a rod is inserted to the opened shed through the entire width of the fabric. To complete the weaving cycle, the remaining ground warps are raised and then again weft yarn is inserted. This weaving cycle is repeated several times; then the rods are slipped out by forming a loop pile. In order to produce cut pile velvet, rods equipped with knives can be used. In some special types of weaving machines with wire weaving techniques, for the production of velvet fabrics, weft yarn is inserted in the bottom shed of a double shed opening while steel rods or wires are inserted in the top shed to obtain piles. Pile yarns are supplied from a creel that all the ends come from a separate package utilising a negative system of yarn feed controlled by friction tension devices. Again in this method, during extraction of the wires, the piles can be cut or uncut or a combination of both. The weft insertion is performed with a rapier and weft insertion rates can be up to 200 rpm. However, the wire insertion reduces the speed of the weaving machine. Through the combination of ground warps and the weft the base fabric is obtained. The pile ends are woven over the wires and fixed into the base fabric in such a way that loops are being formed over the wires. A certain number of wires is woven into the fabric (10, 12, 16, 20 or 24 wires in total). Each wire is inserted into the shed between the weaving reed and the fabric border. The wires that are woven into the fabric are being extracted one by one from the fabric. For each insertion of a wire another wire is extracted. The wire that has been extracted is reinserted into the shed. Pile wires are specially made very fine steel rods rolled in several passages into the final dimension as requested for the specific pile height that one wants to obtain.

#### **4.1.4 Production of spacer fabrics**

Spacer fabrics can be produced both on conventional weaving and special 3D designed weaving machines. These fabrics are classified as even and uneven surfaces according to Chen (2011).

Spacer woven fabrics with even surfaces can be produced on conventional weaving machines with the weft insertion system of shuttle. The weaving loom has a conventional heddle harness (50) system comprising individual heddles 51 to 56 controlling warp yarn groups 11, 12, 21, 22, 31 and 32. As in all weaving looms, shedding and movement of the

In wire weaving technique, there is one set of ground warp, one set of ground weft and an extra set of warp yarns to form piles on the fabric. In order to produce a fabric with this technique, firstly a group of ground warps is raised according to the fabric pattern and the weft yarn is inserted to make its first interlacing with the ground warps. Then, pile warps are raised and a rod is inserted to the opened shed through the entire width of the fabric. To complete the weaving cycle, the remaining ground warps are raised and then again weft yarn is inserted. This weaving cycle is repeated several times; then the rods are slipped out by forming a loop pile. In order to produce cut pile velvet, rods equipped with knives can be used. In some special types of weaving machines with wire weaving techniques, for the production of velvet fabrics, weft yarn is inserted in the bottom shed of a double shed opening while steel rods or wires are inserted in the top shed to obtain piles. Pile yarns are supplied from a creel that all the ends come from a separate package utilising a negative system of yarn feed controlled by friction tension devices. Again in this method, during extraction of the wires, the piles can be cut or uncut or a combination of both. The weft insertion is performed with a rapier and weft insertion rates can be up to 200 rpm. However, the wire insertion reduces the speed of the weaving machine. Through the combination of ground warps and the weft the base fabric is obtained. The pile ends are woven over the wires and fixed into the base fabric in such a way that loops are being formed over the wires. A certain number of wires is woven into the fabric (10, 12, 16, 20 or 24 wires in total). Each wire is inserted into the shed between the weaving reed and the fabric border. The wires that are woven into the fabric are being extracted one by one from the fabric. For each insertion of a wire another wire is extracted. The wire that has been extracted is reinserted into the shed. Pile wires are specially made very fine steel rods rolled in several passages into the final dimension as requested for the specific pile height that one wants to obtain.

Spacer fabrics can be produced both on conventional weaving and special 3D designed weaving machines. These fabrics are classified as even and uneven surfaces according to

Spacer woven fabrics with even surfaces can be produced on conventional weaving machines with the weft insertion system of shuttle. The weaving loom has a conventional heddle harness (50) system comprising individual heddles 51 to 56 controlling warp yarn groups 11, 12, 21, 22, 31 and 32. As in all weaving looms, shedding and movement of the

Fig. 10. Face to face weaving technique of producing velvet fabrics

(Van De Wiele as cited in Chen, 2011).

**4.1.4 Production of spacer fabrics** 

Chen (2011).

harnesses in timed sequence with shuttle and reed movement is controlled with the shedding mechanism. Figure 12 represents the opened shedding for 21 and 22 warp yarns for weft insertion, shuttle (57). On the loom, totally three shuttles are used, one for each fabric ply. With arranging the fabric take-up motion in time sequenced with shedding mechanism, this kind of fabric can be easily woven (Koppelman&Edward, 1963).

Fig. 11. Different views of spacer fabrics (Chen, 2011).

Fig. 12. Method of weaving a hollow 3D woven fabric on a conventional loom (Koppelman&Edward, 1963).

Another design of 3D spacer fabric consisting of double ribs between the bottom and top layers or a 3D spacer fabric with an I shape can be produced on a conventional weaving machine (Rheaume, 1976). For the production of this type of fabric, the weaving loom has to have four separate shuttles and to include eight separate harnesses, each of which control different groups of warp yarns. Both of these two fabrics have the properties of foldability while being produced on the loom. When the fabrics are taken off the loom and get rid of the stresses, they open up and have the cross sections of V-shaped and I-shaped (Figure 13).

Shell fabrics are a special class of 3D woven fabrics since the structure of these fabrics may have only one layer or multiple layers; however the end product is always three dimensional. The importance of these types of fabrics is increasing since these types of woven fabrics are widely used in helmets, bra cups in fashion and clothing, female body

Shell (a.k.a. doomed) fabrics can be produced with weaving, or cut and sew. Cut and sew technique has been the most commonly method used to produce shell fabrics but seams are a big disadvantage in technical applications, where the continuity of fibres is important. Seams definitely reduce the level of reinforcement and protection. Furthermore, cut and sew

Fig. 15. An example of a shell fabric woven with conventional weaving (Chen, 2011)

Fig. 15. An example of a shell fabric woven with conventional weaving (Busgen, 1999)

Fig. 16. Weave combination to produce shell fabric (redrawn from Chen&Tayyar, 2003)

In conventional weaving, shell fabrics can be produced with using discrete take up and combination of different weaves. In order to produce a shell woven fabric, one can use a mixture of weaves with long and short floats. For instance, the plain weave, the tightest, is arranged in the middle, where a 2/2 twill is used in middle ring, and a five-end satin, with the longest average float length which is the loosest weave of the three types, is used for the outer ring. In a fabric with constant sett (the same warp and weft densities), the areas woven with plain weave tends to occupy a larger area and therefore will grow out of the fabric plane; the part of the fabric with the five-end satin tends to be squeezed, thus enhancing the domed effect. Consequently, the height difference between the lower and higher planes forms a dome. This method is a quick, easy, and economical way to produce fabrics that require relatively small domed effects. However, it appears that for fabrics requiring larger domed effects, the weave combination method is not sufficient (Chen&Tayyar, 2003).

**4.1.5 Production of shell fabrics** 

armour and car door lining material (Chen&Tayyar, 2003).

creates extra waste of materials and labour (Chen&Tayyar, 2003).

Fig. 13. Method of weaving a hollow 3D woven fabric consisting of two ribs on a conventional loom and appearance of fabric cross section and I-shaped hollow fabric (Rheaume, 1976&1970).

Another type of 3D woven spacer fabric with double ribs connecting the upper and lower layers which is designed to be used in lightweight composite materials is given in Figure 14. However, the structure of this fabric is different compared to the others mentioned up to now. The double ribs connecting the top and bottom layers also constitute the upper and lower layers interchangeably. The weaving of this fabric is possible with warp-let off and fabric take up modifications of the narrow weaving machine. The weaving is performed in three stages; upper and lower ground fabrics weaving, wall-fabrics weaving, and backward movement of the floated tight yarns (formation of wall-fabric) (Badawi, 2007).

Fig. 14. The structure of 3D woven spacer fabric designed for lightweight composites (Badawi, 2007)

Fig. 13. Method of weaving a hollow 3D woven fabric consisting of two ribs on a conventional loom and appearance of fabric cross section and I-shaped hollow fabric

movement of the floated tight yarns (formation of wall-fabric) (Badawi, 2007).

Fig. 14. The structure of 3D woven spacer fabric designed for lightweight composites

Another type of 3D woven spacer fabric with double ribs connecting the upper and lower layers which is designed to be used in lightweight composite materials is given in Figure 14. However, the structure of this fabric is different compared to the others mentioned up to now. The double ribs connecting the top and bottom layers also constitute the upper and lower layers interchangeably. The weaving of this fabric is possible with warp-let off and fabric take up modifications of the narrow weaving machine. The weaving is performed in three stages; upper and lower ground fabrics weaving, wall-fabrics weaving, and backward

(Rheaume, 1976&1970).

(Badawi, 2007)
