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Review Articles

# Ballistic Resistant Body Armor: Contemporary and Prospective Materials and Related Protection Mechanisms

[+] Author and Article Information
N. V. David

Department of Mechanical Engineering, Texas A&M University, 3123 TAMU, College Station, TX 77843-3123

X.-L. Gao1

Department of Mechanical Engineering, Texas A&M University, 3123 TAMU, College Station, TX 77843-3123xlgao@tamu.edu

J. Q. Zheng

Program Executive Office – Soldier, U.S. Army, Haymarket, VA 20169

Denier is a measure of linear density (mass per unit length) of a yarn. The Industrial Fabrics Association International defines this measurement based on grams per 9000 m of fiber or yarn. Another measure of linear density of fabric fibers is known as Tex and is measured in g/km. Tenacity is the amount of force (in grams) required to break a yarn, normalized with respect to the denier, and hence the ‘g/denier’ quantity. Tenacity thus reflects the strength of a fabric.

Coating Spectra 900® with vinylester and polyurethane resins couples the yarns and prevents yarn mobility. This produces a more uniform stress state in the resin coated fabric via stiffening effect of the resin. The inward deflection of the composite panel is therefore restricted, which makes the penetrator engage and break more yarns, resulting in enhanced energy absorption.

Kevlar 29® plates, made from prepreg fabrics impregnated with a vinyl ester resin (a copolymer of polyethylene), at a curing temperature of $125°C$, with eleven plies each having a thickness of 1.8 mm, showed an increased bending stiffness.

1

Corresponding author.

Appl. Mech. Rev 62(5), 050802 (Jul 09, 2009) (20 pages) doi:10.1115/1.3124644 History: Received October 26, 2008; Revised March 23, 2009; Published July 09, 2009

## Abstract

Modern military operations, technology-driven war tactics, and current on-street weapons and ammunition necessitate the development of advanced ballistic protection body armor systems that are damage-resistant, flexible, lightweight, and of great energy absorbing capacity. A number of studies related to new concepts and designs of body armor materials (including those derived from or inspired by nature) have been conducted in the past two decades to meet the new demands. Ballistic fabrics, ceramics, and laminated composites are among the leading materials used in modern body armor designs, and nano-particle and natural fiber filled composites are candidate materials for new-generation body armor systems. Properties and ballistic resistance mechanisms of such materials have been extensively investigated. Based on a comprehensive and critical review of the advances and findings resulting from these investigations, a comparative study on design, protection mechanisms, and performance evaluation of various types of anti-ballistic body armor is presented in this paper. Body armor systems made from different materials and exhibiting distinct ballistic energy absorption mechanisms are discussed, and key factors that influence the ballistic performance and energy absorbing mechanisms of the body armor systems are identified.

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## Figures

Figure 1

Comparison of the energy absorption of four different material systems

Figure 2

(a) Compound body armor design and (b) penetration of a projectile followed by the deflection of its trajectory (after Ref. 48)

Figure 3

(a) Material configuration and (b) performance comparison (V50) of Sentinel® woven fabric/non-woven fabric systems (after Ref. 49)

Figure 4

Damage zones in the ceramic tile, backing plate and a projectile (bullet)

Figure 5

Composite structure of ALGLA-2S42 (after Ref. 79)

Figure 6

Composite armor for blunt trauma reduction (after Ref. 20)

Figure 7

Elongation at failure and tensile strength of NFs, GFs, and ballistic fibers

Figure 8

V50 performance of different ballistic fabric armor systems

Figure 9

Ballistic limits of selected laminate and hybrid composite systems (areal density shown inside bar)

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