Study On Anti-Impact Performance Of Silly Putty-Kevlar Composites

In recent years,due to the continuous spread of international terrorism and regional conflicts,it has become one of the hot spots to develop the protective clothing with reliable protective and comfortable performance.Although some high-strength flexible fibers such as Kevlar and ultra-high molecular weight polyethylene have been widely used as protective materials,this type of protective clothing usually needs to combine many layers of fibers or combine fibers with metals or ceramics for meeting the bulletin resistance requirement.The methods damage the wearing comfort.Thus,there is an effective way to improve the protective performance and ensure the wearing comfort to combine the high-strength flexible fibers with unique smart materials.The shear-thickening material is one kind of the smart materials with special properties.The mechanical properties of the material are very sensitive to the strain rate.The material is soft and even will flow at low strain rate,but when the strain rate increases,such as affected by impact,the modulus and strength of the material will increase dramatically and the material will turn into a hard-solid state with the energy dissipation and protection effects.Silly Putty（SP）is one of them.Because of the advantages of easy preparation,stable performance,no need for strict sealing,and so on,SP has a good potential application as the reinforcing material for the high-strength flexible fibers.In this paper,based on Silly Putty and Kevlar,two kind of anti-impact composites were prepared and impact testing systems with different speed ranges were designed to study the anti-impact performance of these composites.The specific research content is as follows:1.The CaCO₃ reinforced SP-CaCO₃ composites with different content of CaCO₃ were prepared.And a Kevlar/SP/Kevlar sandwich composite by using the SP-CaCO₃ as the core and two layers of Kevlar as the panels was prepared.The function of the modulus of SP-CaCO₃ with shear frequency shows the significant shear-hardening property of SP.The anti-impact performance of samples was characterized through the low-speed drop weight impact and high-speed ballistic impact testing systems.The result shows the sandwich composite whose core is the SP-CaCO₃ with higher content of CaCO₃ can dissipate more impact energy.And due to the shear-hardening effect,the energy dissipation is higher under high-speed impact.2.Different layers of Kevlar/SP composites were prepared through a "dissolving and volatilizing" method.A multi-point force testing system was designed.The different layers of Kevlar and Kevlar/SP were testing through the low-speed drop weight impact and high-speed ballistic impact testing systems.The result shows that the Kevlar/SP with the same area density decreases the thickness and attenuates the impact force.When the center force was attenuated,the surrounding force increased,which declares the impact force can be dispersed and attenuated effectively.In addition,the pull-out force of the fiber and the deformation of the transverse fiber in the single-layer and three-layer Kevlar/SP were lager than Kevlar.It declares SP can strengthen the friction between fibers and layers,which leads to the dispersion and attenuation of the impact force.3.The Kevlar/SP/Kevlar and 2 layers of Kevlar/SP with same area density and same content of SP were prepared,respectively.The penetration test was conducted by using the high-speed ballistic impact system to compare the properties of the two kinds of Kevlar-SP composites.The result shows that the energy dissipation of Kevlar/SP/Kevlar is higher than Kevlar/SP.It declares that the protective property of Kevlar/SP/Kevlar is stronger than Kevlar/SP.In addition,the preparation process of Kevlar/SP/Kevlar is simpler and the SP can be strengthened by dispersing reinforced particles.Thus,it is a more effective combination method.