Graduation Year

2011

Document Type

Thesis

Degree

M.S.M.E.

Degree Granting Department

Mechanical Engineering

Major Professor

Autar Kaw, Ph.D.

Committee Member

Glen Besterfield, Ph.D.

Committee Member

Craig Lusk, Ph.D.

Committee Member

Woven Composites, Textiles, Impact, ANSYS, AUTODYN, Mechanical Energy Transfer

Keywords

Woven Composites, Textiles, Impact, ANSYS, AUTODYN, Mechanical Energy Transfer

Abstract

Current military-grade rifle body armor technology uses hard ballistic plates positioned on top of flexible materials, such as woven Kevlar® to stop projectiles and absorb the energy of the impact. However, absorbing the impact energy and stopping a rifle projectile comes at a cost to the wearer - mobility. In this thesis, a new concept for personal body armor is proposed - a semi-flexible hybrid body armor. This hybrid armor is comprised of two components that work as a system to effectively balance the flexibility offered by a soft fabric based armor with the protection level of hard plated armor. This work demonstrates techniques used to analyze and design the hybrid armor to be compliant with National Institute of Justice guidelines. In doing so, finite element analysis is used to simulate the effect of a projectile impacting the armor at various locations, angles, and velocities, while design of experiments is used to study the effect of these various impact combinations on the ability of the armor component(s) (including the wearer) to absorb energy.

The flexibility and protection offered by the two component armor system is achieved by the use of proven technique and innovative geometry. For the analytical design, the material properties, contact area(s), dwell duration, and energy absorption are all carefully considered. This yields a lightweight but yet effective armor, which is estimated to weigh 36% less than the current military grade hard body armor.

Using ANSYS, several simulations were conducted using finite element analysis, including a direct center impact, along with various other impacts to investigate possible weak points in the armor. In doing so, it is determined that only one of these impact locations is indeed a potential weak point. The finite element analysis continues to show that a rifle projectile impacting at an oblique angle reduces the energy transferred to the wearer by about 25% (compared to a direct impact).

A design of experiments approach was used to determine the influence of various input parameters, such as projectile impact velocity and impact location. It is shown that the projectile impact velocity contributes 36% to the ability of the wearer to absorb energy, whereas impact velocity contributes only 13% to the energy absorbed by the top armor component. Furthermore, the analysis shows that the impact location is a highly influential factor (with a 69% contribution) in the energy absorption by the top armor component.

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