Investigation of mechanical and ballistic properties of multi-walled carbon nanotube bonded and shear thickening fluid impregnated fabrics and hybrid laminated composites

Our police officers and soldiers, who are obliged to protect and allocate peace and security in our country, face the danger of losing their lives as a result of an attack with a weapon, a sharp object or a bradawl at any moment. The design and production of lightweight, anti stab and flexible protective armor that protects lives of our police and soldiers who struggle in order to ensure the safety of life and property of citizens against various criminal organizations both at domestic and abroad have a vital importance. Therefore, in this thesis, it is aimed to produce armor with increased ballistic and mechanical strength by using nano-material (multi-walled carbon nanotube: MWCNT) and shear thickening fluid (STF) technology. This thesis project basically consists of three parts. . In the first part, shear thickening fluids (STF) with the silica loading of 5 w%, 10 w%, 15 w% and 20 w% were fabricated and then rheological measurements were carried out. As a result of rheological measurements, shear thickening behavior was observed in STFs with the silica loading of 10 w%, 15 w% and 20 w%. Then, kevlar, hybrid (kevlar / carbon) and carbon fabrics were impregnated with STF/ethyl alcohol suspension containing 20 w% silica. and the effect of STF on low velocity puncture and ballistic behavior of fabrics was investigated. Drop tower impact test results revealed that STF impregnation of carbon fabrics cause a reduction on the puncture resistance of the carbon fabrics, and an increase on puncture resistance of kevlar and hybrid fabrics. With the STF impregnation, for the drop height of 400 mm, penetration depth of kevlar and hybrid fabrics showed 65.4% and 19.2% decrease, and carbon fabric exhibited an increase of 33.2%. It was also observed that the ballistic resistance of all three fabrics increased with STF impregnation. In the second part of the project, multi-walled carbon nanotubes (MWCNT) were bonded to the surface of carbon fiber with the grafting technique, and these fabrics were impregnated with STF. Grafting of MWCNTs onto carbon fibers led to a decrease in drop weight impact and balistic resistance of the fabrics. As a result of grafting of MWCNTs onto carbon fibers, an increase of 33.3% was observed in the average penetration depth, and this increase was 59.6% for MWCNTs grafted-STF impregnated carbon fabrics compared to neat carbon fabrics. STF impregnation of MWCNT grafted fabrics caused an increase in their ballistic resistance. In the last part of the project, rigid armors were produced using Kevlar fabrics in order to pave the way for the use of STF not only in flexible protective body armors, but also in helmets, tanks, planes, and vehicles. Mechanical properties of these rigid armors were determined by applying three point bending, tensile and impact tests. As a result of the impact tests, there was an increase of 42.2% in the absorbed energy with STF impregnation on the fabrics.