Improving the Impact Resistance Performance of STF Treated Kevlar Fabric Structures

Abstract

Abstract A continuous increase in the war-conflicts and development in the area of weapons challenges the research community to develop the body armor materials accordingly. The focus is on making the materials light weight and flexible yet improving its impact resistance performance to make the material compatible to use for a longer duration. Application of nano-materials such as nano-fibers, nano-fillers and nano-finishes are turning the concept into reality. Application of shear thickening fluid (STF) has been proved to increase the impact resistance performance of the textile structures to further use it as a body armor material. Present research deals within the same segment where nano-silica based STF was applied on Kevlar woven fabric to make the structure lightweight and flexible while improving its impact resistance performance. It was observed in the earlier studies by the authors that it is difficult to get a fair amount of add-on of STF on Kevlar fabric as it comes with a PTFE coating which hinders its absorbency. Hence, a novel method named as sequential padding is developed in the present study to improve the add-on of STF on Kevlar fabric. Contrary to the conventional process, where Kevlar fabric is treated with STF once using any one pressure, in sequential padding method, the Kevlar fabrics were treated twice using three levels of pressure (0.5, 1 and 2 bar) in various combinations and sequences. STF add-on % and dynamic Impact energy absorption on dynamic impact tester at a fixed velocity of 6 m/s were observed for sequentially padded fabrics and compared with untreated Kevlar fabric and fabrics treated with STF in single step. Low velocity bullet proof tests with 165 m/s were also performed to verify the results It was observed that both add-on% and impact energy absorption of Kevlar fabrics increases significantly with sequential padding process as compared to untreated as well as single step padding process. It was also noted that different combinations and sequences of padding pressures used for STF treatment of Kevlar fabric play a significant role in improving the impact resistance performance. It was noted that impact energy absorption of sequentially padded Kevlar fabric show almost 125% increase in ballistic impact energy absorption (40.62 J) as compared to untreated fabric (18.07 J). Therefore, it is concluded that sequential padding process opens up a new horizon for further improvement in impact performance of body armor materials based on STF treated Kevlar fabrics.