**2.1 Definition of 3D woven fabrics**

A basic common definition of 3D fabric is that these types of fabrics have a third dimension in the thickness layer. In 3D-fabric structures, the thickness or Z-direction dimension is considerable relative to X and Y dimensions. Fibres or yarns are intertwined, interlaced or intermeshed in the X (longitudinal), Y (cross), and Z (vertical) directions (Badawi, 2007).

3D fabrics can also be defined as "a single-fabric system, the constituent yarns of which are supposedly disposed in a three mutually perpendicular plane relationship" (Behera&Mishra, 2008). According to Chen, structures that have substantial dimension in the thickness direction formed by layers of fabrics or yarns, generally termed as the three-dimensional (3D) fabrics (Chen, 2011). Although all textiles have a 3D internal structure, macroscopically most can be regarded as thin 2D sheets. By 3D fabrics, (1) thick multilayer fabrics in a simple regular form or (2) made in more complicated 3D shapes, (3) hollow multilayer fabrics containing voids and (4) thin 3D shells in complex shapes are meant (Hearle&Chen, 2009). Khokar defined 3D woven fabrics as a fabric, the constituent yarns of which are supposed to be disposed in a three-mutually-perpendicular-planes relationship (Khokar, 2001).

#### **2.2 Classification of 3D woven fabrics**

When the classification of 3D woven fabrics are examined, it is observed that there are several classifications based on the shedding mechanisms, weaving process, geometries and configurations, interlacements and fibre axis according to the different researches (Khokar,1996 as cited in Soden&Hill, 1998; Chen, 2010; Soden&Hill, 1998;Bilisik, 2011).

Khokar classified the 3D fabrics as follows (Khokar, 1996 as cited in Soden&Hill, 1998);


which make them difficult to comprehend. Therefore, this chapter attempts to make a detailed overview of 3D woven fabrics, basic structure of 3D woven fabrics, definitions and

A basic common definition of 3D fabric is that these types of fabrics have a third dimension in the thickness layer. In 3D-fabric structures, the thickness or Z-direction dimension is considerable relative to X and Y dimensions. Fibres or yarns are intertwined, interlaced or intermeshed in the X (longitudinal), Y (cross), and Z (vertical) directions (Badawi, 2007).

3D fabrics can also be defined as "a single-fabric system, the constituent yarns of which are supposedly disposed in a three mutually perpendicular plane relationship" (Behera&Mishra, 2008). According to Chen, structures that have substantial dimension in the thickness direction formed by layers of fabrics or yarns, generally termed as the three-dimensional (3D) fabrics (Chen, 2011). Although all textiles have a 3D internal structure, macroscopically most can be regarded as thin 2D sheets. By 3D fabrics, (1) thick multilayer fabrics in a simple regular form or (2) made in more complicated 3D shapes, (3) hollow multilayer fabrics containing voids and (4) thin 3D shells in complex shapes are meant (Hearle&Chen, 2009). Khokar defined 3D woven fabrics as a fabric, the constituent yarns of which are supposed to be disposed in a

When the classification of 3D woven fabrics are examined, it is observed that there are several classifications based on the shedding mechanisms, weaving process, geometries and configurations, interlacements and fibre axis according to the different researches (Khokar,1996 as cited in Soden&Hill, 1998; Chen, 2010; Soden&Hill, 1998;Bilisik, 2011). Khokar classified the 3D fabrics as follows (Khokar, 1996 as cited in Soden&Hill, 1998);

1. The conventional 2D weaving process designed to interlace two orthogonal sets of threads (warp and weft). This produces *an interlaced 2D fabric* on a 2D weaving device. 2. The conventional 2D weaving process designed to interlace two orthogonal sets of yarns (warp and weft) with an additional set of yarns functioning as binder warps or interlacer yarns in the through-the-thickness or Z direction. This is referred to as multilayer weaving and produces *an interlaced 3D fabric* constituting two sets of yarns

3. The conventional 2D weaving process using three sets of yarns (ground warp, pile warp

4. The conventional 2D weaving process using three sets of yarns to produce a noninterlaced fabric with yarns in the warp, weft and through-the-thickness directions. This produces *a non-interlaced 3D fabric* with three sets of yarns on a 2D weaving device. 5. The 3D weaving process designed to interlace three orthogonal sets of yarns. The weaving shed operates both row-wise and column-wise. This produces *a fully interlaced 3D fabric* where all three sets of orthogonal yarns interlace on a specifically designed 3D

and pile weft) to produce pile fabrics, known as *2.5D fabrics*.

classifications of 3D woven fabrics in comparison with 2D woven fabrics.

three-mutually-perpendicular-planes relationship (Khokar, 2001).

**2.1 Definition of 3D woven fabrics** 

**2.2 Classification of 3D woven fabrics** 

on a 2D weaving device.

weaving machine.

**2. Definition, classification and weave structures of 3D woven fabrics** 

6. A non-woven, non-interlaced 3D fabric forming process designed to connect three orthogonal sets of yarns together with no interlacing (weaving), interloping (knitting), or intertwining (braiding). The fabric is held together by a special binding process.

However Soden and Hill added a new category as 4A to Khokar's classification for the fabrics that could be placed between categories 4 and 5 where the conventional 2D weaving process uses three sets of yarns to produce *an interlaced 3D fabric* with yarns in the warp, weft and through-the-thickness directions (Soden&Hill, 1998).

Regardless of the types of machines used, weaving technology is capable of constructing 3D fabrics with many different geometrical shapes. Chen studied the configurations and geometries of the 3D woven fabrics and classified 3D woven fabrics into four different categories, as listed in Table 1 (Chen, 2007 as cited in Chen et al., 2011).


Table 1. 3D textile structures and weave architectures (Chen, 2011).
