Comparing the Impact Resistance of  Various Materials Struck by a Projectile

Photo of Jack at Mid Columbia Science Fair

Researched by Jack C.
2005-06




PURPOSE

The purpose of this experiment was to determine the impact resistance of various materials struck by projectile such as a paintball.

I became interested in this idea when I heard that body armor blocked bullets enough to keep from penetrating, although it would knock the wind out of you.

The information gained from this experiment could affect the designs of body armor for soldiers and police officers. It could show the government cost-effective materials to use in the future.



HYPOTHESIS

My first hypothesis was that the neoprene would protect the most when used alone.

My second hypothesis was that the Cordura nylon would protect the least when used alone.

My third hypothesis was that the combination of neoprene and the high-density foam would protect the most in combination.

My fourth hypothesis was that the combination of High Density Foam and Mylar would protect the least in combination.

I based my hypothesis on information from various Internet sites explaining that neoprene is used in a lot of paint ball armor.
 


EXPERIMENT DESIGN

The constants in this study were:
•    The area of the Styrofoam
•    The thickness of the Styrofoam
•    The amount of material used
•    Distance the paintball gun is from target
•    The type and size of paintballs
•    The type and power of the paintball gun

The manipulated variable was the type of materials used to cover the Styrofoam target.

The responding variable was the depth of the dent made in the Styrofoam target.

To measure the responding variable, I used a micrometer accurate to thousandths of an inch.



MATERIALS

QUANTITY
ITEM DESCRIPTION
2
2-by-4 sheets of Styrofoam that is 20cm thick
1
Spyder VL Lynx Paintball marker
100
Big Balls .68 caliber Paintballs
1
T-shirt
1
Sweatshirt
1
Jacket
1
Micrometer (Machinist’s Depth Gauge)
1
Neoprene Wetsuit
4
20cm by 20cm pieces a high density foam
4
20cm by 20cm sheets Mylar
1
1/2 yard by 60 in Cordura nylon
1
Sheet of plywood about 10cm thick
5
Wooden Stakes

                               
 


PROCEDURES


1.    Gather Materials

a.    Buy Paintball marker and paintballs.
b.    Pick up wet suit from dive shop.
c.    Buy 20cm by 20cm sheet of Mylar.
d.    Buy 500 X 152cm piece of1050 Denier Ballistics Cordura nylon.
e.    Buy 20cm by 20cm piece of high-density foam.
f.    Get 10cm thick piece of plywood and 5 wooden stakes
g.    Get one old sweatshirt, one old jacket, and one t-shirt.

2.    Setup Experiment

a.    Cut Styrofoam into equal sheets of 20cm by 20cm.
b.    Saw 1 stake in to two 8 1/8in pieces.
c.    Saw another stake into two 10in pieces.
d.    Then screw 1 of the 8 1/8in pieces vertically on to plywood in center.
e.    Then screw the other piece vertically 10in to the right.
f.    Then screw the 10in pieces on the top and bottom of the 8 1/8in pieces making a square  frame.
g.    Put one test material on each labeled separate sheet of Styrofoam.
h.    Create several combinations of protective materials. Use each of the following:
i.    Neoprene + High Density Foam
j.    Neoprene + Cordura Nylon
k.    Cordura Nylon + High Density Foam
l.    Mylar + High Density Foam
m.    Set the plywood upright against fence.
n.    Load paint ball marker.

3.    Conduct the Experiment

a.    Put each material in wooden frame.
b.    Fire at material on one Styrofoam sheet from 5 meters away three times.
c.    Repeat steps 1 on each material.
d.    Take material off.
e.    Take to Kelly Conolly at Smith inc. with the micrometer to measure the indent in the Styrofoam with micrometer.
f.    Record depth of craters on a chart.
 


RESULTS

The original purpose of this experiment was to determine the impact resistance of various materials struck by a projectile such as a paintball.

The results of the experiment were that Cordura Nylon protected best for the single materials. The combinations of Neoprene and Cordura Nylon, Neoprene and High Density Foam all protected completely. Out of the single materials Mylar protected the least. Out of the composites the combination of High Density Foam and Mylar protected the least.

See the table and graph below.
 


CONCLUSION

My first hypothesis was that the neoprene would protect the most alone. The results indicate that my first hypothesis should be rejected, because neoprene did not protect the best, Cordura Nylon did.

My second hypothesis was that the Cordura nylon would protect the least alone. The results indicate that my second hypothesis should be rejected because the Cordura Nylon did not protect the worst, Mylar did.

My third hypothesis was that the combination of neoprene and the high density foam will protect the most. The results indicate that my third should be accepted because the Neoprene/High Density Foam combination did protect the best. Although one other combination protected just as well.

My fourth hypothesis was that the combination of High Density Foam and Mylar would protect the least. The results indicate that my fourth hypothesis should be accepted because the combination of High Density Foam/Mylar did protect the least.

After thinking about the results of this experiment, I wonder if there would be a way to make an inflatable or “bubble wrap” style composite that used air bag materials perhaps bonded to thin ceramic plates.

If I were to conduct this project again I would make bigger targets, and find a flatter material to shoot at. I would do more trials and use a more powerful projectile.
 


RESEARCH REPORT

Introduction

 Humans need protection from physical harm. Soldiers and police need effective protection from bullets and other projectiles. This safety is very important. It could mean life or death.

Soft and Hard Body Armor

The two main materials used in soft body armor are Kevlar and Polyethylene. These two materials are designed to stop bullets that soften on impact. They supply little protection against sub machine guns. The protection needed to stop these bullets is in hard body armor. This body armor has two ceramic plates. It is difficult to move in hard body armor.

New materials have come out that have high impact resistance and soft bullet protection. They are made from the synthetic polymers. They make it impact resistant and penetration resistant. The secret is the ethylene based thermoplastic that makes a net. It takes 22 layers of this to stop a bullet or prevent injury.

Blunt Trauma

Impact is when two objects collide and energy and momentum are transferred. The energy is called impact. The higher the velocity of the object, the greater the impact. Body armor must absorb or distribute the impact across a large part of the body to minimize injury.

Kevlar does not stretch so when hit with a bullet the energy from impact is transferred through the weavings and into the body. The body can only stand so much of this.

Aramids

Aramids are like nylon, but are strong as steel, and heat resistant. Its chemical compounds are made up of amides. These form chainlike molecules called polymers. The amides are connected by two aromatic rings. This is what makes Aramid very heat resistant.

Aramids are used in tires, parachutes, reinforced tape, and bulletproof vests. They also reinforce boat hulls and the bodies of airplanes. Trade names include Nomex, Kevlar, Twaron, and Technora.

Polymer

A polymer is a substance consisting of large molecules made out of smaller molecules called monomers or mers. The number of units in the large molecules is called its degree of polymerization. Materials with a high degree of polymerization are called high polymers. A polymer with one repeating unit is called a homo- polymer. Copolymers have several repeating units.

Polymers are divided into 3-4 different structural groups. Molecules in linear polymers consist of chains made by rigid degree bonds. Monomers cannot rotate with each other. Polyethylene is an example. Branched polymers have side chains attached to the main chain molecule. Branching is caused by impurities or monomers in reactive groups. Chain polymers are composed of monomers with side groups that are part of the monomer. Cross linked polymers are two or more chains joined by side chains. A small degree of cross linking makes a 2-D object. High cross linking makes a 3-D object. 

Ethylene

Ethylene is the simplest member of a class of aliphatic compounds called alkenes. They all have at least one carbon-carbon double bond. It is produced by cracking and fractional distillation of petroleum and natural gases.

Neoprene

Neoprene is a synthetic rubber. It is abrasion resistance, chemical resistant, waterproof, buoyant, and stretchable. It is in everything from wetsuits to protective gear. The most common use of neoprene is in wetsuits. A neoprene wetsuit traps water containing heat from the wear’s skin. Neoprene wetsuits are used in scuba diving and surfing. Neoprene is used out of water for its chemical resistance in gloves and other protective gear.

Mylar

Mylar is a strong polyester film. It grew out of the development of Dacron in the 1950’s. In the 1960’s Cellophane gave way to Mylar because of its strength, heat resistance, and insulating properties. Mylar is used in the magnetic audio and video tape, packaging, and battery industries.
 

BIBLIOGRAPHY


“Body Armor” Protective Equipment and Body Armor http://www.azom.com/details/ArticleID=1663#_Protective_Equipment

Gregory V. Richard. “Aramid.” World Book Encyclopedia. 2004.

Griskey G. Richard. “ Polyethylene. ” Microsoft Encarta. 2001

“Mylar.” Mylar: 1952  http://heritage.dupont.com/touch/

“Neoprene” What is Neoprene Rubber?
  http://www.wisegeek.com/what-is-neoprene-rubber.htm

Richardson L. Terry.  “Polymers.” Microsoft Encarta. 2001.



ACKNOWLEDGEMENTS


I would like to thank the following people for helping make my project possible:
•    My parents for always reminding me to get on topic and suggesting and buying the items for my experiment.
•    I would like to also thank Dan and Sherlie White for giving me a wet suit for my project.
•    I would like to thank Conner, Scotty, Lyndsey and Mary for keeping me on task.
•    I would also like to thank Mr. Newkirk for giving me material ideas and advice for the      experiment.
•    I would also like to thank Mrs. Viernes for fixing problems on the computers I was using and helping me with my graphs.
•    I would Like to thank Kelly Connoly for letting me use his micrometer.


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