**3.4. Effect of the draping start point**

3.4. Effect of the draping start point

3.3. Effect of nonwoven fabric orientation

50°

0°

20°

Very large shear angles

90°

35°

9

10

45° 90°

Defect

very excessive shear angles induce defects and superposition of the cross-ply in the composite part after

**Figure 7.** *Mold design and experimental nonwoven draping result* 

Fiber disentanglement

**Figure 8.** *CAD and mesh of the mold* 

*(a) Nonwoven fabric (b) Woven fabric*

Junction unraveling P

0°

25°

20°

23°

Fiber disentanglement

P

Junction unraveling

**3.3. Effect of nonwoven fabric orientation** 

ment and junction unraveling.

**3.3. Effect of nonwoven fabric orientation**

**Figure 10.** Shear angle of draped UD fabric and woven carbon fabric

50°

0°

Very large shear angles

90°

152 Non-woven Fabrics

35°

**Figure 9.** 3D geometrical draping using UD fabric and woven carbon fabric

20°

**0°**

**Figure 9.** *3D geometrical draping using UD fabric and woven carbon fabric*

**Figure 10.** *Shear angle of draped UD fabric and woven carbon fabric* 

90°

70°

The mechanical response of nonwoven fabrics exhibits an anisotropic response biased toward the direction of preferential alignment of constituent fibers. The deformation mechanisms governing the fabric response under bias-loads include textural evolution by means of reorientation of constituent

The mechanical response of nonwoven fabrics exhibits an anisotropic response biased toward the direction of preferential alignment of constituent fibers. The deformation mechanisms governing the fabric response under bias-loads include textural evolution by means of reorientation of constituent fibers, fiber stretch, relative fiber slip, as well as fiber disentangle‐

The proposed mold shape is now draped geometrically using three fiber orientations. Here, only the predicted fiber orientations on the mold shape are compared. Figures 11, 12, and 13 show the resulting 3D nonwoven fabric draping for the 0°, 90°, and 45° drape orientations, respectively, and the corresponding shaded contours interpolated from the map of the fiber orientation. From these figures it can be concluded that for the same initial contact point, the shear angle 80 localization is different and level is highly dependent on the mold geometry and the boundary conditions. Various defects such as unraveling of weaving and disentanglement of the fibers produced during the layup and may have effects on the quality of the final composite part after the injection of resin or polymerization.

The proposed mold shape is now draped geometrically using three fiber orientations. Here, only the predicted fiber orientations on the mold shape are compared. Figures 11, 12, and 13

**Figure 11.** *3D draping and iso-values of fiber angles of the 0° nonwoven draping*

**0°**

**55°**

**10° 15°**

**0° 6°**

fibers, fiber stretch, relative fiber slip, as well as fiber disentanglement and junction unraveling.

**Draping direction** Fiber disentanglement

Fibre interlacing **90°**

Junction unraveling

resin injection or polymerization.

To study the effect of the initial start point on the draping results, a surface double dome is draped by non-woven fabric (Fig. 14). The mold shape consists of two coinciding hemispheres with different radii (small sphere radius R = 75 mm and large sphere radius R = 100 mm). The

Excess fabric

To study the effect of the initial start point on the draping results, a surface double dome is draped by non-woven fabric (Fig. 14). The mold shape consists of two coinciding hemispheres with different radii (small sphere radius R = 75 mm and large sphere radius R = 100 mm). The initial start point P in the simulation was chosen as the top of the small (D1) or the large hemisphere part (D2). The initial ply orientation was perpendicular to the main axis of the mold (Fig. 15). Here, the predicted 3D draping,

1. At first glance, the results look very similar for the draping on the smaller sphere start point and on the large sphere start point (see Figs. 16 and 17). Both cases predict the same fiber directions

shear fiber orientations on the double dome shape, and the 2D flat pattern are compared [45].

along the main mold perpendicular axis and the same 2D fabric flat pattern (Fig. 19).

Figure 13. 3D draping and iso-values of fiber angles of the 45° nonwoven draping

70°

25°

20°

23°

90°

18°

55°

0°

10°

0°

6°

 Figure 13. 3D draping and iso-values of fiber angles of the 45° nonwoven draping **Figure 13.** 3D draping and iso-values of fiber angles of the 45° nonwoven draping

initial start point P in the simulation was chosen as the top of the small (D1) or the large hemisphere part (D2). The initial ply orientation was perpendicular to the main axis of the mold (Fig. 15). Here, the predicted 3D draping, shear fiber orientations on the double dome shape, and the 2D flat pattern are compared [45]. 3.4. Effect of the draping start point To study the effect of the initial start point on the draping results, a surface double dome is draped by non-woven fabric (Fig. 14). The mold shape consists of two coinciding hemispheres with different radii


This difference can be explained from the D1 draping, which starts from the top of the small hemisphere and extends outward from the highest point at the edge, resulting in gradually downward moving fibers and fiber disentanglement. When the fiber reaches the edge of the intersection fillet (position C), it will extend from that position onward (marked A), up and over the top of the larger hemisphere, resulting in a large fabric deformation at the outer area of the hemispheres and fiber interlacing.

The D2 draping starts from the top of the large hemisphere and extends outward from the lower point at the edge, resulting in gradually downward moving fiber and fiber disentan‐

12

13

13

glement. When the fiber reaches the edge of the intersection fillet, it will extend from that position onward (marked B), up and over the top of the larger hemisphere, resulting in a large fabric deformation at the outer area of the hemispheres and fiber interlacing. hemispheres and fiber interlacing. The D2 draping starts from the top of the large hemisphere and extends outward from the lower point at the edge, resulting in gradually downward moving fiber and fiber disentanglement. When the fiber reaches the edge of the intersection fillet, it will extend from that position onward (marked B), up and over the top of the larger hemisphere, resulting in a large fabric deformation

at the outer area of the hemispheres and fiber interlacing.

intersection fillet (position C), it will extend from that position onward (marked A), up and over the top of the larger hemisphere, resulting in a large fabric deformation at the outer area of the

2. With the geometrical simulation, large fabric deformations occur (up to 80°) for the D1 draping; however, smaller fabric deformations occur (up to 60°) for the D2 draping (Fig. 18). 3. For the inner areas on the two domes, the geometrical draping method predicts smaller nonwoven fabric shear angles for the two case draping D1 and D2 (marked with E, F, G, and H)

4. For the outer areas, both cases predict different fiber orientations in regions A, B, and C (see Fig. 18). The main differences occur in the concave area between the two hemispheres (region B) and outer areas of the large hemisphere (region A) and small hemisphere (region C). With the geometrical simulation, on both, the larger and the smaller hemispheres, large fabric

Figure 14. Schematic view of the double dome **Figure 14.** Schematic view of the double dome

(see Fig. 18).

deformations occur (up to 70°).

initial start point P in the simulation was chosen as the top of the small (D1) or the large hemisphere part (D2). The initial ply orientation was perpendicular to the main axis of the mold (Fig. 15). Here, the predicted 3D draping, shear fiber orientations on the double dome

Excess fabric

Figure 13. 3D draping and iso-values of fiber angles of the 45° nonwoven draping

70°

25°

90°

18°

55°

0°

20°

10°

0°

6°

23°

Figure 12. 3D draping and iso-values of fiber angles of the 90° nonwoven draping

**1.** At first glance, the results look very similar for the draping on the smaller sphere start point and on the large sphere start point (see Figs. 16 and 17). Both cases predict the same fiber directions along the main mold perpendicular axis and the same 2D fabric flat pattern

shear fiber orientations on the double dome shape, and the 2D flat pattern are compared [45].

To study the effect of the initial start point on the draping results, a surface double dome is draped by non-woven fabric (Fig. 14). The mold shape consists of two coinciding hemispheres with different radii (small sphere radius R = 75 mm and large sphere radius R = 100 mm). The initial start point P in the simulation was chosen as the top of the small (D1) or the large hemisphere part (D2). The initial ply orientation was perpendicular to the main axis of the mold (Fig. 15). Here, the predicted 3D draping,

**2.** With the geometrical simulation, large fabric deformations occur (up to 80°) for the D1 draping;however, smallerfabricdeformationsoccur(upto60°)fortheD2draping(Fig.18).

along the main mold perpendicular axis and the same 2D fabric flat pattern (Fig. 19).

1. At first glance, the results look very similar for the draping on the smaller sphere start point and on the large sphere start point (see Figs. 16 and 17). Both cases predict the same fiber directions

**3.** For the inner areas on the two domes, the geometrical draping method predicts smaller nonwoven fabric shear angles for the two case draping D1 and D2 (marked with E, F, G,

11

**4.** For the outer areas, both cases predict different fiber orientations in regions A, B, and C (see Fig. 18). The main differences occur in the concave area between the two hemispheres (region B) and outer areas of the large hemisphere (region A) and small hemisphere (region C). With the geometrical simulation, on both, the larger and the smaller hemi‐

This difference can be explained from the D1 draping, which starts from the top of the small hemisphere and extends outward from the highest point at the edge, resulting in gradually downward moving fibers and fiber disentanglement. When the fiber reaches the edge of the intersection fillet (position C), it will extend from that position onward (marked A), up and over the top of the larger hemisphere, resulting in a large fabric deformation at the outer area

The D2 draping starts from the top of the large hemisphere and extends outward from the lower point at the edge, resulting in gradually downward moving fiber and fiber disentan‐

shape, and the 2D flat pattern are compared [45].

**Figure 13.** 3D draping and iso-values of fiber angles of the 45° nonwoven draping

3.4. Effect of the draping start point

spheres, large fabric deformations occur (up to 70°).

(Fig. 19).

154 Non-woven Fabrics

and H) (see Fig. 18).

of the hemispheres and fiber interlacing.

 Figure 15. Initial start point on the top of the small sphere (draping D1) and on the large sphere (draping D2) **Figure 15.** Initial start point on the top of the small sphere (draping D1) and on the large sphere (draping D2) Figure 15. Initial start point on the top of the small sphere (draping D1) and on the large

sphere (draping D2)

Figure16. 3D draping results of nonwoven fabric on double dome

Figure16. 3D draping results of nonwoven fabric on double dome (a) Draping D1 on small sphere (b) Draping D2 on large sphere

 **Figure 16.** 3D draping results of nonwoven fabric on double dome

**Figure17.** *Predicted fiber orientation of the nonwoven fabric on double dome* **Figure 17.** Predicted fiber orientation of the nonwoven fabric on double dome C

**E**

**A**

Figure 18. Shear angle of draped nonwoven fabric of drape D1 and drape D2

(a) Draping D1 on small sphere (b) Draping D2 on large sphere Figure17. Predicted fiber orientation of the nonwoven fabric on double dome

**A**

**E**

C

14

14

**Figure 18.** Shear angle of draped nonwoven fabric of drape D1 and drape D2

15

Figure 19. 2D Flat pattern results of drape D1 and drape D2

**Figure 19.** 2D Flat pattern results of drape D1 and drape D2
