## 3 Results and Discussions
### Ballistic Performances of the 3D Warp Interlock Fabrics
#### 3.1.2 Energy Absorption Capabilities of 3D Warp Interlock Fabrics  
Enhancing a fiber-based textile made soft body armor panel performance requires a full understanding of its different ballistic impact mechanisms during the ballistic impact process. Understanding exactly the energy absorbing mechanisms of the material is one of the methods to know the ballistic impact phenomenon of the panel target. Normally, the impact energy of ballistic fabric panels with high-speed projectile will be converted into various forms mainly to kinetic energy. Such converted kinetic energy will be then either absorbed by the fabric panels or transmitted to the back of the material which could create some trauma indentations. Enhancing the energy absorbing capability of the fabric could ultimately reduce the trauma and injury created at the back of  
Figure 11: Measured averaged BFS diameter for different 3D warp interlock variants and 2D plain weave para-aramid fabrics at different shoot locations. (* All shots were penetrated for 3D-40-4B:8S,* shot 6 penetrated sample 2D-35 and * shot 1 & 4 penetrated sample 3D-40-8/0).  
the panels. Considering material type, fabric structure, fabric finishing, fabrics areal density, panel arrangement areal density, etc. are some of the major parameters that could influence and enhance the energy-absorbing capabilities of the final fabric panels. Besides, shock wave propagations on the panel surface could be also generated by the impact energy. Such dynamic impact mechanisms bring the probability of destructing different fabric elements including filaments, fibers, and yams.  
So far, various techniques have been involved to derive the constitutive relations and model the overall fabric ballistic mechanisms against impacts to better understand, improvement, and use in different applications. Generally, two types of yarn are involved in the fabric during projectile impacts. The first are primary yarns which is in direct contact with the projectile, whereas, secondary yarns are those yarns that are not in direct contact with projectile [8].  
For fully penetration testing conditions, the energy absorbed capacity by the fiber-based woven fabrics will be calculated as follows:  
\[\mathrm{E_{m}}\ =\ \frac{1}{2}\ \mathrm{m}\ \mathrm{\left({v_{i}}^{2}-\ v_{e} ^{2}\right)},\ \mathrm{if}\ \mathrm{v_{i}}>\ v_{p} \tag{1}\]  
\[\mathrm{E_{m}}\ =\ \frac{1}{2}\ \mathrm{m}\ {v_{i}}^{2}\,\ \mathrm{if}\ \mathrm{v_{i}}<\ v_{p} \tag{2}\]  
where,  
m is the projectile mass (kg);  
\(\mathrm{v_{i}}\) is the impact velocity of the projectile (m/s);  
\(\mathrm{v_{e}}\) is the exit velocity of the projectile (m/s);  
\(\mathrm{v_{p}}\) is the penetration velocity of the projectile (m/s);  
\(\mathrm{E_{m}}\) is the projectile energy loss (joule).  
Such an equation is normally used to determine the ballistic limits of soft body armor panels. However, in the current research study, the non-penetration ballistic testing condition has been carried out to investigate the overall ballistic performances of the 3D warp interlock fabric structures. Besides, unlike the penetrated testing approach, the non-penetrated testing conditions could use different BFS measurements to compute the panel's energy-absorbing capabilities. For instance, according to the NIJ standard, the BFS volumes of each shot on the backing material could help to compute the ballistic targets absorbed and transmitted energy values at the corresponding shot points. In general, the higher back face signature volume at the back of the ballistic panel target, the higher amount of energy could be transmitted to the back of the ballistic panels and vice-versa.  
Based on the investigation, Figure 12a, b shows the energy absorbed and transmitted values respectively for various 3D warp interlock panels and 2D plain weave p-aramid fabrics.