1. Technical Seminar on, LIQUID ARMOR By- Gokul Raghunandan 1BM07ME036 Under the guidance of Dr. S. SRINIVAS

2. CONTENTS BODY ARMOR DILATANT BALLASTIC MATERIALS REQUIREMENT WORKING TESTING PROPERTIES REFERENCE

3. Body Armor Used to catch and deform projectiles and shrapnels, and spreading impact force over a larger portion Is of 2 types, 1)Laminated fabric 2)Fabric with metal/ceramic plates

4. Dilatant (STF) Non-newtonian fluid Its Viscosity increases with increase in rate of shear Coated on Kevlar fiber Ex-Glycerine

5. Working Mechanism The fluid has hard solid particles tightly packed with the liquid closing the gaps. The liquid acts as a lubricant between the particles hence behaving like a fluid at low shear rates. At high shear rates the liquid is unable to fill the gaps and lubricate them hence the STF acts like a solid.

6. Ballastic Material Containment fibers used to dissipate energy. Have high tensile strength and high tensile modulus. Are mainly, Aramid fibers High molecular weight polyethylene High molecular weight polypropylene High molecular weight poly vinyl alcohol

7. Requirement A material of, High strength Improved ability to dissipate the kinetic energy of a moving object Exhibiting Shear Thickening properties Improved flexiblity

8. Working of Liquid Armor Liquid Armor hardens when agitated to prevent any projectiles or shrapnels from penetrating it, a thin layer of this liquid is coated on Kevlar fabric.

9. Testing The test is performed on Slilca particles suspended in ethylene glycol (vol. factor 0.57) Avg particle diameter=446 micro m STF undergoes ST transition at shear rate of 10^2 to 10^3 s^(-1) (reversible) Kevlar fabric- 600 denier plain-woven Hexcel-Schwebel high performance fabric Style 706 composed of Kevlar KM-2 aramid fibres with an areal density of 180 g/m 2.

10. Target Preparation Equal volume of ethanol (22.0 dyne/cm) was added to the original ethylene glycol (surface tension=47.7 dyne/cm) Impregnated onto the fabric Heated to 80`C for 20min in a convection oven to remove ethanol

11. Ballistic test A-Target (Kevlar with STF per layer -2, 4, 8ml), placed between two aluminium foils) B-Unimpregnated Kevlar Helium gas gun was used *Velocity- 244m/s *22caliber *Bullet diameter-0.56cm Shear rate=(projectile velocity/projectile diameter)

12. Flexiblity and Thickness Test

13. Result of Testing Comparing targets A,B & C: 2 ml of STF impregnated into 4 layers of neat Kevlar, 10 layers of neat Kevlar, and 4 layers of neat Kevlar, respectively. It is found that, Sample target Description Sample weight (g) Impact velocity (m/s) Penetration Depth (cm) Bending angle (`) Sample thickness (mm) A 2ml STF impregnated in 4 layers of Kevlar 4.82431.23511.5 B10 layers of Kevlar4.72471.55133.0 C4 layers of Kevlar1.92442.12501.4

14. Cost Analysis Protection offered by 10 layers of kevlar can be achieved with 4 layers +STF This saves the cost of 6 layers of kevlar STF is made up of inexpensive materials like silica particles and ethylene glycol Cost is not a matter of concern when a few mm of penetration can mean the difference between life or death of the user.

15. Properties Light and flexible, very deformable material. Can withstand a wide range of temperatures. Hardens under sudden application of pressure Returns to a liquid form after pressure is released.

16. Conclusion Body armour as a whole has been significantly improved since the use of STF in it. There has been testing for variou other applications like brake pads etc

17. References http://www.ccm.udel.edu/ http://www.gizmag.com/go/5995/ http://science.howstuffworks.com/liquid- body-armor.htm http://science.howstuffworks.com/liquid- body-armor.htm http://www.crcind.com.au