A numerical study on the mechanisms of Dyneema® quasi-isotropic woven panels under ballistic impact

Quasi-isotropic (QI) fabric panels were recently found to have a promising performance against ballistic impact, compared with the aligned panels, since more areas in the followed plies are transversely deformed in the QI panels forced by the front plies. However, the ballistic mechanisms of QI panels have not been completely elucidated. This study aims to identify the ballistic mechanisms of QI woven fabric panels using finite element method (FEM), focusing on the interference from the back plies towards the front. A yarn-level Dyneema® woven fabric model was created, and then validated by the ballistic test results. 2-ply, 3-ply and 4-ply aligned and QI panels were investigated in terms of energy absorption, the initial time of yarn failure, penetration time of panels, and stress distribution within different plies. ImageJ® software was used to quantify the areas under stress in different scale ranges in different plies. It was found that QI panels absorbed 6%–8% more energy than aligned panels, and were less vulnerable to be perforated. Moreover, compared with the aligned panels, QI panels overall had approximately 10% larger areas stressed in the front plies. These results were attributed to the fact that QI panels have higher efficiency in stress distribution along the primary yarns in the front and middle plies. The higher efficiency afterwards was ascribed to the higher interference between plies in the QI panels. This study demonstrated the importance of interference in QI panels on stress distribution, and the findings are of great significance for guiding further designs of fabric and composite panels for the ballistic protection.