Test of the Impact Resistance of
Water Containing Various Additives
Alan Weiner
Guilford High School
Abstract
The described research tests the feasibility of the application of liquid solutions in body armor that would allow an increase in the mobility of the user when compared to traditional body armor. I tested the impact of a golf-ball projectile into 10 inches of clay that was immersed in various depths of either water alone or water containing various additives. I tested salt, flour and corn starch. I wanted to determine what I could do to water to increase its impact resistance. In the end a thixotropic (a material that gets hard when pressure is applied to it) mixture (in my example cornstarch and water) resisted impact the most.
Problem
This experiment tested the feasibility of using liquids in the application of body armor to increase the mobility of the user without sacrificing protection when compared to traditional body armor. Potentially the application of liquid body armor could be used in the military, construction industry, or anywhere that mobility and protection is required, thus saving lives. I intend to prove that the application of liquids as a protective barrier is feasible.
Hypothesis
If the four water mixtures (bleached flour/water, corn starch/water, salt/water, water) are tested for resistance to impact, then the thixotropic mixture (corn starch and water) will perform the best (defined by resisting the impact with the least amount of cratering).
Materials:
- 5 gal buckets (5)
- water source
- two-liter graduated cylinder
- 4540 grams bleached flour (Stop and Shop brand, Guilford, CT)
- 4540 grams corn starch (Stop and Shop brand)
- 2936 grams salt (Stop and Shop brand)
- 50 pounds of Laguna white clay (Laguna Clay Company, CA)
- 77” high wooden platform
- 3 Cinder blocks
- Pneumatic spud cannon
chamber = 1573 inches
valve used was a 1 inch modified Orbit Water Master sprinkler valve
barrel = 58 inch schedule 21 PVC pipe
- 2 x 4 plank (2)
- 13 golf balls
- 13 coffee stirrers
- ruler
- bike pump and/or air compressor
- wire tool (used to cut the clay)
- Sharpie pen
- pencil
- electric drill and wall-paste liquid mixing attachment for drill
Procedure
1) Preparation of firing area:
- Lay the two planks parallel to each other about 6” apart over the 77” high plat form.
- Lay all three cinder blocks on the platform sides of the planks
- With barrel off, set the spud gun off the platform, aiming down supported by the two planks.
- Set up the air compressor so that the spud gun can be pressurized without the necessity of taking the gun off its platform.
2) Mixing of test solutions:
- Take one of the 5 gal buckets, fill it with 8000 ml water, 2936 g salt (this is the maximum amount of salt that can be dissolved into the given amount of water)
- Take a second 5 gal bucket, fill with 2500 ml water, dissolve into the water 4540 g corn starch
- Work the water and corn starch until they are of uniform consistency.
- Take a third 5 gal buckets, fill it with 3500ml water, 4540 grams flour.
- Work until uniform consistency is established. Liquid mixer made for electric drills is optional (I used one, and it helped a lot)
- Take the fourth 5 gal bucket and fill ¾ with water.
- Note; Let all solutions cool to room temperature.
3) Preparation of clay:
- Cut the 25 lbs of clay into blocks 10” by 6” by 6” (approximately 16 lbs) each.
4) Testing:
- Put one block of clay into a center of a 5 gal bucket, on the 6” by 6” surface.
- Using a ruler mark points, 1”, 3”, and 5” above the top of the clay slab.
- Pour one of the liquids into the bucket until it fills the bucket up to the highest mark.
- Wearing face protection, pressurize the spud gun to 30psi
- Load golf ball into barrel and attach to gun
- Take the bucket to the spud gun, line up the center of the barrel with the center of the bucket.
- With gun primed, quickly grab the valve’s trigger, move to a safe spot at least 10 feet away, and fire.
- Quickly pour water + additive mixture back into its original bucket.
- Take clay slab out.
- From the bottom of the clay slab, poke pencil through the clay, pushing the golf ball out the open end.
- Take a coffee stirrer, put one end at the bottom of the crater and mark on the stirrer with a pencil how deep the crater is from the bottom of the crater to the top of the clay slab.
- Measure the mark on the coffee stirrer with a ruler
- Record depth
- Repeat with depths 1”, and 3”
- Repeat with the three other substances
6) Testing the penetration depth, without water (just air as a protection):
- Cut a block of clay 15” by 6” by 6”
- Put block of clay into center of the fifth, 5 gal bucket, on the 6” by 6” surface
- Wearing a face mask pressurize the spud gun to 30 psi
- Load golf ball into barrel and attach to gun
- Take the bucket to the spud gun, line up the center of the barrel with the center of the bucket.
- With gun primed, quickly grab the valves trigger, move to safe spot, and fire.
- Take clay slab out.
- From the bottom of the clay slab, poke pencil through the clay, pushing the golf ball out.
- Take coffee stirrer, put one end at the bottom of the crater and mark with a pencil how deep the crater is.
- Measure coffee stirrer mark with ruler
- Record depth
Factors controlled
- Impact velocity was controlled through having the same amount of air pressure propelling the golf ball each time.
- Impact velocity was also controlled through the application of a fast opening valve (1 inch modified Orbit Water Master sprinkler valve)
- Hardening of clay (by temperature) was controlled by maintaining both the clay and liquid substances at room temperature. All clay was the same kind and from the same place.
- Projectile to clay resistance was held constant though the use of identical, mass produced, golf balls, a new one for each shot.
Independent variable
- Various depths (1”, 3” and 6” above the clay surface) of flour/water mix, corn starch/water mix, salt/water mix.
Dependant variable
- Crater depth
Controls:
- Air
- Water without any additives
The Spud Gun Spec and Muzzle Velocity. This shows the specifications for the spud gun that was used in the experiments (from:
http://www.thehalls-in-bfe.com/GGDT/).
Experimental Data:
Discussion
My research supports the concepts other places such as MIT, and the military were developing. My research supports my hypothesis that liquid substances can effectively be used as armor without giving up mobility/flexibility. The salt/water solution, which was chosen to illustrate what making the water denser would do, contradicted accepted concepts by allowing greater penetration as compared to plain water. I say the salt/water mixture contradicted accepted concepts because usually someone would think in similar terms to this: what is harder to push your hand through, sand or Jello?
Validity
I believe the validity of my data is accurate. Impact velocity was controlled through having the same amount of air pressure propelling the golf ball each time. Impact velocity was also controlled through the application of a fast opening valve (the 1 inch modified Orbit Water Master Sprinkler valve). Hardening of clay (by temperature) was controlled by maintaining both the clay and liquid substances at room temperature. Projectile to clay resistance was held constant though the use of identical, mass produced golf balls. I used a new golf ball for each shot.
Improvements
One variable not held constant was the distance between the barrels end to the surface of the liquid substance. This varied because the barrel was held constant so that when the depths of the liquid substances changed from 1 inch to 6 inches, there was a 5 inch difference in the barrel to liquid substance distance. However I don’t believe this made a noticeable difference, as the amount of energy lost due to 5” of air resistance (at most) is very minuscule. I also could have taken multiple shots for each depth to increase the accuracy, although I found that the water plus additives did maintain their slopes closely.
Conclusion
Liquid armor is worth researching, as the concept is proven valid in this experiment. The data illustrates that the thixotropic material increases the water’s resistance to impact greatly (if I were to put it in a percent it would be misleading). At a 1 inch (2.54 mm) deep solution, water penetration was 8.8 cm whereas the corn starch mixture had a penetration of less than half of that (4.1 cm). With the 7.62 mm deep solutions, water slightly improved at 7.3 cm, a 1.5 cm improvement. At the same depth the thixotropic solution went to zero penetration. That means that at less than 7.62 mm cornstarch/water penetration was zero. The flour solution was an improvement upon water alone but is not an avenue worth looking into. Surprisingly the salt/water solution performed worst than water alone.
Final thoughts
This experiment proved that liquid armor is an option that should be further researched. I do not have access to the exotic/unfamiliar chemicals/materials that a specialized scientist might, but seeing what I have done with only house hold materials I can only imagine that there are thixotropic substances that I don’t know about, that can resist much higher impacts.
Literature Report
(Attached)
Figure Legends
Experimental Materials
• 1-4, Golf ball and golf ball holder at the top of barrel
• 5-11, Measuring chamber volume
• 12-17, Chamber dimensions, barrel and sprinkler valve
Experimental Set-up
• 1-6, Setting up the spud-gun set-up
• 7, Blocks of clay
• 8-9, Shot barrel (and clay in bucket)
• 10-12, penetration of clay through air, air crater
• 13-17, Measuring water craters at various water depths
• 18-19, Mixing corn starch solutions
• 20, 1 inch of water + corn starch above clay
• 21, 3 inch water + salt crater
• 22-25, water + flour experiment
Golf ball impact into clay through air
