*5.2.1. Non-interlaced fabric structures*

Bilisik and Yolacan [132] investigated the mechanical properties of non-interlaced/non-z single layer and multilayered uniaxial, biaxial and multiaxis E-glass/polyester composites. They reported that the number of layers as well as yarn orientation greatly affects the mechanical properties. An increment in packing density led to higher tensile and flexural strength which was attributed to increase in fiber volume fraction. All samples experienced mode-I delami‐ nation and subsequent failure under tensile loading due to layer/layer separation. This was attributed to the lack of z-yarns and the resulting weakness in out-of-plane direction. Bilisik [133] carried out the experimental determination of ballistic performance of novel composite structures with soft backing aramid fabric. It was reported that specific energy absorption of non-interlaced/non-z E-glass/polyester composite plate with para-aramid soft layered dense woven fabric structure is higher than that of the 3D woven carbon/epoxy and non-interlaced/ non-z E-glass/polyester composite plates with para-aramid soft layered loose woven fabric structure. Damage propagation in the 3D woven structure is smaller than that of the noninterlaced/non-z multiaxis structure, and impact damage was restricted by the z-fiber. Carbon fiber shows brittle behavior during energy absorption, but E-glass fiber shows high extension and distributes the energy around the impacted zone.

## *5.2.2. Multistitched fabric structures*

Warp and weft directional specific tensile strength and modulus of unstitched structure were higher than those of the four- and two-directional light and dense multistitched structures. Stitching causes minor filament breakages as well as creating stitching holes throughout the structure which reduces the in-plane properties of the stitched composite. Accordingly, when the number of stitching directions, and stitching density increased, their warp and weft directional tensile strength and modulus decreased. These results indicated that stitching yarn type, stitching directions and stitching density generally influenced the warp and weft directional tensile properties of multistitched E-glass/polyester woven composites. On the other hand, the damage tolerance performance of the multistitched structures was enhanced due to stitching (in particular, four-directional stitching) [134]. In addition, stitching yarn type, stitching directions, stitching density, and amount of nano materials generally influenced the bending properties of multistitched E-glass/polyester woven composites [135].

#### *5.2.3. Fully interlaced woven fabric structure*

are greatly influenced by the fiber strength and modulus, knitted structure, stitch density, prestretch parameters and incorporation of inlays [36]. The deformation behavior of knitted preforms can be predicted by initial load-elongation properties of knitted fabrics. The knitting process parameters influence the knitted preform during fabrication. Loop formation during the knitting process imposes dramatic bends and twists on fibers that cause fiber/machine element failures when working with high modulus/brittle fibers. It was shown that the knittability of these fibers depends on frictional properties, bending strength, stiffness, and fiber/yarn strength [49]. The knittability of a given yarn can be improved by certain machine parameter adjustments including low tension application during yarn input, fabric take down tension setting, and loop length control which is adjusted by stitch cam settings [109]. Also, the knittability of high performance yarns mainly depends on yarn-to-metal friction charac‐ teristics. Positive yarn feeding control and tension compensator improve the dimensional stability of the knitted preform. It was demonstrated that yarn bending rigidity and inter-yarn coefficient of friction are very important determinants for loop shape while the loop length of high performance yarns, glass yarns in particular, was found to vary with needle diameter,

Bilisik and Yolacan [132] investigated the mechanical properties of non-interlaced/non-z single layer and multilayered uniaxial, biaxial and multiaxis E-glass/polyester composites. They reported that the number of layers as well as yarn orientation greatly affects the mechanical properties. An increment in packing density led to higher tensile and flexural strength which was attributed to increase in fiber volume fraction. All samples experienced mode-I delami‐ nation and subsequent failure under tensile loading due to layer/layer separation. This was attributed to the lack of z-yarns and the resulting weakness in out-of-plane direction. Bilisik [133] carried out the experimental determination of ballistic performance of novel composite structures with soft backing aramid fabric. It was reported that specific energy absorption of non-interlaced/non-z E-glass/polyester composite plate with para-aramid soft layered dense woven fabric structure is higher than that of the 3D woven carbon/epoxy and non-interlaced/ non-z E-glass/polyester composite plates with para-aramid soft layered loose woven fabric structure. Damage propagation in the 3D woven structure is smaller than that of the noninterlaced/non-z multiaxis structure, and impact damage was restricted by the z-fiber. Carbon fiber shows brittle behavior during energy absorption, but E-glass fiber shows high extension

Warp and weft directional specific tensile strength and modulus of unstitched structure were higher than those of the four- and two-directional light and dense multistitched structures. Stitching causes minor filament breakages as well as creating stitching holes throughout the structure which reduces the in-plane properties of the stitched composite. Accordingly, when

stitching cam setting and machine setting [49, 79, 109].

and distributes the energy around the impacted zone.

*5.2.2. Multistitched fabric structures*

**5.2. Three-dimensional fabric**

120 Non-woven Fabrics

*5.2.1. Non-interlaced fabric structures*

Geometrical properties of the representative 3D fully interlaced woven preforms were analyzed and the results are shown in Figure 53. Crimps in the 3D fully-interlaced and semiinterlaced representative woven preform structure were calculated based on the structure dimensions and the uncrimped representative yarn lengths [60]. The following relations can be used:

*cw lw Sl Sl* % ( ) = -´ ( ) 100 / (5)

$$cf\left(\begin{array}{c}\%\\\end{array}\right) = \left(\left|f - Sw\right|\right) \times 100 / Sw\tag{6}$$

$$c\varpi \left( \begin{array}{c} \emptyset \end{array} \right) = \left( l\natural t - St \times 100 \right) / St \tag{7}$$

where, *cw* is the warp crimp (%), *lw* is the uncrimped warp length (cm), *Sl* is the structure length (cm), *cf* is the filling crimp (%), *lf* is the uncrimped filling length (cm), *Sw* is the structure width (cm), *cz* is the z-yarn crimp (%), *lzt* is the uncrimped total z-yarn length (cm) and *St* is the structure thickness. In addition, crimps in the 3D fully-interlaced representative circular woven preform structure were calculated based on the structure dimensions and the un‐ crimped representative yarn lengths [61]. The following relations can be used:

$$\text{Ca} \left( \text{ @} \right) = \left( la - SI \right) \times 100 \text{ / } Sl \tag{8}$$

$$\text{Csc} \left( \text{\%} \right) = \left( \text{lc} - \text{Ssl} \right) \times 100 \text{ /Ssl} \tag{9}$$

$$\text{Cr} \left( \begin{array}{c} \% \end{array} \right) = \left( \text{l}rt - \text{St} \times \text{100} \right) \text{ / } \text{ St} \tag{10}$$

where, *Ca* is the axial crimp (%), *la* is the uncrimped axial length (cm), *Sl* is the structures length (cm), *Cc* is the circumferential crimp (%), *lc* is the uncrimped circumferential length (cm), *Ssl* is the structures outside surface length (cm), *Cr* is the radial crimp (%), *lrt* is the uncrimped total radial length (cm) and *St* is the structures wall thickness.
