Analytical Process

Testing Results

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

According to tensile data collected, contrary to the initial hypothesis, increasing UHMWPE led to a decrease in tensile strength.

 

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The above results of the impact testing were inconclusive due to multiple variables. The Izod test required a different sample geometry and the Charpy test was limited by machine precision. Sample size was also restricted by material and budget constraints.

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Several forms of analyses are required for a working helmet prototype. The ones pertinent to the project involve calculating the energy present in a bullet of varying velocities at the point of contact, the energy required to penetrate a thin layer of armor and Finite Element Analysis.

   

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Figure 1: Bullet Velocity and Respective Energy at Varying Ranges

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Figure 1 shows how bullet velocity ranges from different bullet types in commonly used rifles. The energy associated with this velocity is reduced over larger ranges and is significant to armor penetration.

 

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Figure 2: Penetrating Sloped Armor (Helmet)

 

The forces F1 and F2, depicted in Figure 2, resist penetration and creates an asymmetrical pressure field against the impacting projectile. The asymmetry causes the projectile to be tilted away from the armor plating. This is substantial as this causes the armor to be more effective than just the thickness of hitting a plate head-on [1]. This leads to the energy from the bullet to dissipate more than it otherwise would have in a straight collision with the helmet.

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Citation

[1] Holkko, Niko. “Mechanisms of Armor Penetration.” LinkedIn SlideShare, 24 Apr. 2016, www.slideshare.net/NikoHolkko/bachelors-61286856.