•Tensile Behaviour

Figure 8a shows the tensile properties of the two commingled fabrics and the two fabrics made from 100% hemp roving both in warp and weft direction. The tensile load is given in cN/yarn/Tex to remove the effects of the density and linear density of yarns and concentrate on the effect of the weave pattern and tenacity at the break of the roving. For the commingled satin 6 and twill 6 fabrics, a small difference in maximum tensile load is noted between the two directions. In terms of breaking strain, the weft direction of twill 6 is 55% higher than the warp direction, whereas the strain of satin 6 is similar for the two directions even if the crimp level is higher in the warp direction (Figure 8b). The high strain at break of twill 6 weft direction results from the higher crimp level of weft yarns as the warp yarns are under higher tension than weft yarns during the weaving process. Thus, the twill 6 fabric exhibits better tensile properties, both in warp and weft direction, than satin 6, and this difference can be explained by the difference of weave diagram between the structure and the arrangement of yarns inside the structure. In comparison to the previous study [42], it can be seen that twill 6 and satin 6 structures made from 100% hemp roving exhibit better maximum loads than twill 6 and satin 6 made from hybrid yarns, in the two directions for satin 6 structure and only in weft direction for twill 6 structure. That is mainly attributed to the low tenacity of these hybrid yarns (8 cN/Tex), compared to the

tenacity of 100% hemp roving (24 cN/Tex) [42]. Furthermore, the higher hairiness level of hemp roving conduces higher inter-roving friction, leading to higher maximum loads. Strain at maximum load of the woven fabrics is balanced between the two directions for these structures except for commingled twill 6 structure, which has a high strain at break in the weft direction in comparison with the other structure.

**Figure 8.** (**a**) The tensile load (in cN/yarn/Tex) of the woven fabrics; (**b**) the tensile strain at break of the woven fabrics.

• Flexural Behaviour

Figure 9 shows the flexural rigidity of the two fabrics. The two fabrics have the same warp density and differ only by their weft density and structure. Twill 6 exhibited better rigidity than satin 6 in the two directions, and this difference is mainly due to the high areal density of the fabric (42% higher than that of satin 6) and its yarn density in the weft direction. The flexural rigidity depends strongly on those two parameters. However, a high weft density and linear density result in a heavy fabric. The flexural rigidity also depends on the crimp level of yarns inside the structure. In the case of twill 6 fabric, the shrinkage of weft yarns is greater than warp yarns, and that led to higher rigidity in the weft direction of the fabric than in the warp direction. By contrast, for satin 6 fabric, the warp yarns exhibit higher crimp, which results in a higher rigidity in this direction than in the weft direction.

**Figure 9.** The flexural rigidity of the two fabrics.

#### *3.3. Composite Properties*

3.3.1. Composition of the Composite Plates

The obtained physical compositions of the two composite plates are summarised in Table 4. The two types of composites were produced by stacking two cross-plies. As a result, the thickness of twill 6 hemp/PA11 composite (C2) is 28% higher than composite made from satin 6 (C1). The weight of the two types of composites is the same and differs from that in the original (50% of hemp and 50% of PA11), which is explained by the loss of PA11 during the compression process. By contrast, the volume of fibre in the C2 is 22% greater than C1.

3.3.2. Tensile Properties of the Composite Plates

The tensile strength, strain at break, and modulus of the two types of composites are shown in Figure 10. For each structure, the properties are almost the same for both directions of the composite plates, while at the same time, the tensile properties differ slightly per composite. The tensile stress and modulus of C1 exceed those of C2, and the opposite is the case for strain. Even if the fibre content of C1 composites is lower than that of C2, their tensile properties are higher. At the fabric scale, the twill 6 fabric exhibited better properties, both in tensile and flexural rigidity, whereas this is no larger than the case at the composite scale.

**Figure 10.** (**a**) Tensile strength of composite materials; (**b**) strain at the maximum strength; (**c**) modulus.

3.3.3. Flexural Behaviour of the Composite Plates

The results of the flexural testing are shown in Figure 11. For the satin 6 composites (C1), direction 2 presents better properties than direction 1, while for twill 6 (C2) the opposite is the case. The flexural strength is not balanced between the two directions of the composite plates even if the stacking is balanced. This difference is explained by the arrangement and the orientation of the yarns inside the structure of the composite. In the case of satin 6 composite plates (C1), the float yarns of direction 2 are located outside the specimen, and that provides additional rigidity to this direction. The same phenomenon happens to direction 1 of the twill 6 composite plates (C2). This behaviour has been identified in previous work within the same project [8] and confirmed in this study. The arrangement of yarns inside the composite plates depends strongly on the nature of the fabric structure used and on the way of stacking the different layers.

**Figure 11.** The flexural strength of the two composite materials.