Sample of Interim Report-1

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REYERSON UNIVERSITYFACULTY OF ENGINEERING, ARCHITECTURE AND SCIENCE

DEPARTMENT OF MECHANICAL AND INDUSTRIAL ENGINEERING

MEC 825 Mechanical Design

Interim Project Report

Friday, Feb. 16th

, 2007

Design of a Bulletproof Vest

MANK Engineering Consultants

Faculty Advisor: Dr. Habiba Bougherara

Team Members: Karthik Shetty XXX128067

Nishant Jauhari XXX165667Matthew Choi XXX128155

Andy Rodriguez XXX128144


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TABLE OF CONTENTS

1. Introduction............3

2. Methodology..5

3. Literature Review & Background Research

1. Dupont Kevlar 29/49/149.....7

2.

Dyneema Ultra High Molecular Weight Polyethylene Fiber ...8

3. Honeywell International Inc. - Spectra Fibers.8

4. CoorsTek, Inc. - Boron Carbide Plates............9

5. U.S. Military Interceptor Body Armor Aluminum Oxide Plates.10

4. Revised Timeline

1. Milestone Timeline..10

2. Gantt chart...13

5. References.14

6. Appendix...16

List of Figures

1. Figure 1 Typical Properties of KEVLAR 29 and 49 yarns[1].162. Figure 2 Comparative Properties of KEVLAR vs. other yarns [1]..173. Figure 3 Effect of Elevated Temperatures on the Tensile Strength of KEVLAR 29

[1].17 4. Figure 4 Comparative Effect of Elevated Temperatures on the Modulus of Various

Yarns [1]..18 5. Figure 5: Boron Carbide used for Dragon Skin body armor [4].....................................186.

Figure 6: Deltoid and Axillary Protectors (DAP) [5]..187. Figure 7 Boron Carbide Compound [15]......................................................................198. Figure 8 Honeywell Spectra Fibers

[12]...19

9. Figure 9: Area density of ceramic composite systems [14].....19

List of Tables

1.

Table 1: Performance requirements of various levels of protection for body armor.........62. Table 2: Desired Material Properties for Bulletproof Vest ...7

3. Table 3: Summary of properties for Kevlar..7

4. Table 4: Properties of Ultra High Molecular Weight Polyethylene Fiber 8

5. Table 5: Properties of Spectra Fiber .9

6. Table 6: Properties of Boron Carbide Plates 9

7. Table 7: Properties of Aluminum Oxide Plates..10


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1.

Introduction

Bulletproof vests have been around for a long time. With passing time come changes and newer

updates to make an existing product better. These vests are no different from other commercial

products, and the task of improving the quality, weight distribution, performance while reducing

the overall cost was assigned to our team. A bulletproof vest is designed to stop bullets and other

ammunition from piercing the users body. The main concept is that the energy of the bullet is

transferred throughout the layers and dissipated away from the user. The purpose of the project is

to find and research newer composite materials that can be used for the bulletproof vest to

increase its performance, structure, strength to weight ratio and while keeping all these effective,

also reduce cost wherever possible. The newer revised design made up of composites should

address these points.

The design is basically going to be a careful selection and combination of materials and layers

with a high strength to weight ratio. After thorough research and selection of the design

materials, simulations need to be run and finite element analysis will be conducted to see the

performance of the proposed design and how it would fare better when compared to existing

bulletproof vests. Additional calculations would also be performed to find out how many layers

of energy absorbing materials would be required to stop the majority of bullets before they reachthe ceramic layer. All these factors have to be kept in mind while redesigning the bulletproof

vest as the materials used have to be much more effective as compared to existing ones, and the

design should not cost more than current bulletproof vests.

Problems with the existing design:

The existing designs are either too expensive or too fragile for prolonged use. The core of the

outermost layer (made up of Kevlar 29) is a knitted structure, consisting of interlocking strands

of the material [1]. Upon impact with even a single bullet, these interlocks are broken to dissipate

the energy, resulting is more exposure and allowing the next bullet to penetrate further. If the

existing designs are subject to a flurry of rapid firing, the Kevlar is no longer as effective and

bullets seem to reach as far as the ceramic layering.


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Interceptor body armor, which was formerly used by the US military is a ballistic armor made of

Kevlar fibers and ceramic plates. Developed by Defense Advanced Research Projects Agency

(DARPA), the vest accomplishes the goal of stopping the 7.62x51 mm M80 ball rounds from

penetratingthe vest, but it also has a lot of problems. The interceptor vest weighs approximately3.8 kg and 1.8kg per plate, a total of 7.4 kg [2]. Other than weight, the interceptor vest also has

substantial backface deformation, which can cause blunt trauma to the body. The Small Arms

Protective Insert (SAPI) plates are able to stop rifle rounds from penetrating the vest, but have

low durability; if they are dropped they may crack from the impact. Moreover, the Interceptor

body armor is incapable of stopping .44 Magnum or 9mm bullets. Furthermore, the vest does not

cover the shoulder or the upper arm which resulted in 15% Marine deaths [2]. Unfortunately,

adding more area is a compromise. The shoulder and upper arm protection adds 10-16lbs more

weight and this could decrease the mobility of the user.

Another existing design is the Dragon Skin body armor by Pinnacle Armor [3]. It accomplishes

the goal of stopping the 7.62x51 mm M80 ball rounds from penetratingthe vest [4]. The Dragon

Skin vest has much greater stopping power than the Interceptor vest. The weight of the vest is

also significantly lower than the Interceptor; weighing in at 2.7 kg. The specially designed tiles

effectively absorb and disperse the energy if the impact while also effectively avoiding backface

deformation. Some other advantages of the Dragon Skin armor are: high repeat hit capability,

flexibility, Ergonomic capabilities, and better edge hit capability. However, when the US Army

tested this body armor, the bullet pierced the armor thirteen times proving that this type of armor

is not as effective as Interceptor even though its lighter [5].

Proposed design:

The objective of our design is to improve the existing vest by introducing another material in the

form of a sandwich layer while making sure the cost and the weight of the vest is low. Ballistic

bulletproof vest consists of two main parts, the external layer made up of Kevlar, and a much

harder inside layer composed of ceramic. Using composite materials ensures strength and

effectiveness that the vest requires. For this particular re-design of the ballistic vest, the material

selection will be a mixture of Kevlar, Ceramics and/or ultra-high molecular weight Polyethylene

fiber. Primary fiber material will most likely be Kevlar 29, 49 or 129 due to its high strength to


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weight ratio and synthetic polymer fiber properties but other materials like Spectra and Dyneema

will also be taken into consideration. Since our design is a ballistic armor, the different ceramic

plates will be compared and the best one will be chosen.

2.

Methodology

In order to perform performance index calculations and finite element analysis, we have to

develop a methodology to determine the right composite material needed for each of the layers.

The bulletproof vest is designed to protect the user from high velocity objects that can injure the

user. Therefore, constraints have to be taken into consideration when calculating for performance

index. The fiber material needs to have a high strength-to-weight ratio so that it is lightweight as

well as effective against high energy impacts. Moreover, the right material needs to maximize

energy dissipation and fracture toughness. The cost on the other hand needs to be minimized

since conventional bulletproof vests are very expensive.

There are different criterias that have to be considered in relation to the bulletproof vest. The

stiffness and strength limited design is called structural index. The index value for stiffness-

limited design at minimum mass (E1/3

/ ) and strength-limited design at minimum mass (1/2 / )

needs to be high. Minimizing material usage is optimal for any design of any size provided they

have the same structural index. Moreover, damage tolerant design (KIC2/ E ) has to also be high.

This ensures that the vest will resist fracture in the absence of a crack. Finally, the energy

absorption capability (C = (E/) which is the conversion of mechanical energy into internal

potential energy must be high to ensure that the energy generated from impact is uniformly

distributed. For each of the formulas, E is the modulus of elasticity, is density of the material,

is the tensile strength, KICis the fracture toughness and C is the speed at which stress waves and

their strain energy spread from the projectile impact point [6].

Once these constraints are met, the design will be constructed using ANSYS and impact

simulation will be performed. The results generated from these simulations will be compared to

common bulletproof materials like Kevlar 29 or Kevlar 49. In doing so, we can then see what


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type of level our vest is tailored to. Level I-IIIA is soft fibers and Level III and Level IV is

ballistic, which consist of soft fibers and ceramic plates. Table 1 shows the different levels of

body armor performance and its corresponding performance.

Table 1: Performance requirements of various levels of protection for body armor [7].


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3.

Literature Review and Background Research

There are many different designs for bulletproof vests on the market today; each with their

benefits and problems. Bulletproof vests are commonly composed of two parts: the soft armor

component and the hard armor component. The level of protection provided by certain body

armor is described under the standard tests performed by the National Institute of Justice (NIJ).

The protection levels range from I to IV, with increasing levels of protection. For levels I to

IIIA, only soft armor component is used; levels III to IV use both soft and hard armor

components [7]. The soft component, usually fabricated from an aramid or an ultra high

molecular weight type fiber, while the hard armor component is usually a ceramic or composite.

The standard or common design for body armor is aramid with ceramic/composite layer. The

material selection for bulletproof vest is based on the following material properties. Table 1

outlines desirable characteristics of bulletproof vests.

Performance Characteristic: Performance Index:

High Stiffness / Lightweight (E1/3/ )High Strength / Lightweight (1.2/ )

High Fracture Toughness (KIC2/ E )

High Energy Absorption

Capability(C = (E/)

Table 2: Desired Material Properties for Bulletproof Vest [6]

2.1 Dupont Kevlar 29/49/149

Kevlar is the registered trademark aramid fiber that is widely used in the area of body armor for

its excellent combination of properties; such as high strength, high stiffness and toughness, and

stability at high temperatures; it can be noted that Kevlar has a strength to weight ratio five times

greater than steel [8]. The properties for the different versions of Kevlar are summarized in the

following table.

Material Tensile Modulus (E)Gpa

Tensile Strength ()GPa

Density ()(g/cm3)

Kevlar 29 83 3.6 1.44

Kevlar 49 131 4.1 1.44

Kevlar 149 186 3.4 1.47

Table 3: Summary of properties for Kevlar[9]


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For soft armor component in existing bulletproof vests, Kevlar/Epoxy is the most common

material used. The purpose of the soft layer in high level protection armor is too absorb and

dissipate some of the energy of the bullet; energy absorbance properties of Kevlar is extremely

important. Depending on the volume fraction between Kevlar and epoxy defines the overall

property of the soft armor layer.

2.2 Dyneema Ultra High Molecular Weight Polyethylene Fiber

Dyneema, a thermoplastic material, can also be chosen due to its high degree of polymerization

which can effectively transfer the load resulting in high impact strength vest. Furthermore,

polyethylene fiber is a soft layer sheet that lies between the two strong materials (i.e. ceramic or

Kevlar), allowing for maximum absorption of energy. It can also cover the entire surface of the

vest, giving extra protection to the shoulder and the sides of the torso, thus eliminating the

problems caused by existing designs. The benefit of using Dyneema along the shoulders and side

torso is that it is not a hard material and does not restrict the movement of the arms/shoulders of

the user [10]. The following table shows the properties of Dyneema. We can see that it has a high

Youngs Modulus which is a good indication that this is an idea material to use for our vest.

Youngs Modulus 55,000-172000 MPa

Tensile Strength 1400 3090 MPa

Yield Strength 1400-3090 MPa

Density 970 kg/m3

Elongation 2.7-4.5%

Table 4: Properties of Ultra High Molecular Weight Polyethylene Fiber [11]

2.3 Honeywell International Inc. - Spectra Fibers

The Honeywell Company created unique composition of fiber that boasts to be one of the

world's strongest and lightest fibers [12]. This bright white polyethylene compound is said to befifteen times stronger than steel and more durable than any polyester combination as seen in

figure 8. Mainly known for its ballistic-resistance strength and stopping power while being

lightweight at the same time. The beauty of spectra fibers can be seen when applied to the SAPI

armor plates. Mainly used in the military, the ceramic plates in SAPI are being fabric-covered

which results in a ceramic strike face that is bonded to a panel made of multiple layers of Spectra


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Shield material. Hence with the ceramics designed to shatter the bullets into pieces, the Spectra

Shield material will limit the penetration of the bullet fragments, reducing the effects of blunt

trauma. Spectra Shield can easily be moulded into a variety of shapes. It is also resistant to

moisture and greatly excels in meeting the specifications of ballistic resistance and trauma

reduction. Furthermore studies suggest that the SAPI plates covered with Spectra Shield materialwill be 50% lighter than the average medium size plates, thus reducing the weight of the user

without compromising performance and quality [12]. Further applications of this revolutionary

technology include usage in ballistic riot shields and vehicle armament. The following tables

shows some properties of Spectra fibers. Sp

Density 0.970 g/cc

Tensile Strength, Ultimate 3000 MPa

Modulus of Elasticity 172 GPa

Elongation at Break (%) 2.7-3.5

Table 5: Properties of Spectra Fiber [13]

2.4 CoorsTek, Inc. - Boron Carbide Plates

Boron Carbide plates are used in Level III and Level IV body armor. These are called ballistic

armor as they consist of fibers and ceramic plates. Boron Carbide is an extremely hard ceramic

material that is commonly used as tank armor and bulletproof vests. Boron carbide is so hard that

is measures 9.3 in the hardness test on the Mohs scale. Furthermore because of its low density

property, boron carbide is the perfect material to use as body armor. It is 20% lighter than silicon

carbide and even 37% lighter than aluminum oxide (alumina) - the other materials commonly

used in body armor [14]. Aside from the physical toughness, boron carbide has a black solid

appearance as seen in figure 7 and can be fabricated using high-temperature powder metallurgy

[15]. These plates are commonly found in Interceptor Armor along with Kevlar KM2 fiber.

Density 2.48 g/cm3

Tensile Strength 460-500 MPa

Yield Strength 320-400 MPa

Elongation at Break 0.9-1.7%

Hardness 30 GPa

Table 6: Properties of Boron Carbide Plates [16]


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2.5 U.S. Military Interceptor Body Armor Aluminum Oxide Plates

Interceptor Body Armor used by the US military mainly consists of two modular components:

outer tactical vest and small-arms protective inserts. The outer tactical vest is made up of Kevlar

weave while small-arms protective inserts are made of aluminum oxide ceramic plates.

Additionally, the inserts can also be made of boron carbide ceramics. Aluminum Oxide has ahigh temperature capability and high strength and stiffness. It has a low relative cost and

provides a good thermal conductivity [17]. The following table shows the properties of

Aluminum Oxide. We can see that it the plate has a high hardness value and this is idea because

we dont want the plate to initiate a crack. Moreover, the fracture toughness, which is the

materials ability to resist fracture in the presence of a crack, is 4 MPa m1/2

.

Density 3.89 gm/cc

Flexural Strength 379 MPa (lb/in2x10

3)

Elastic Modulus 375 GPa (lb/in2x10

6)

Shear Modulus 152 GPa (lb/in2x10

6)

Hardness 1440 Kg/mm2

Fracture Toughness KIC 4 MPa m1 2

Table 7: Properties of Aluminum Oxide Plates[18]

4.

Revised Timeline

Initiate Project time line January 15 2010

Initial meeting with Dr. Habiba Bougherara January 20 2010

Defining team member responsibilities January 20 2010

Initial Design Sketches January 22 2010

Background Research February 02 2010

Assign individual report tasks February 02 2010

Edit Interim Report February 08 2010

Interim Report February 12 2010

Material Properties research (meeting with group to discuss

findings and proper selection) February 22 2010

Meeting with Dr. Habiba Bougherara regarding project status February 25 2010

Group meeting sketches and final concept March 01 2010


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Compare final concept with existing ideas/designs March 04 2010

Preliminary design drawings/flowcharts March 09 2010

Performance index calculations March 19 2010

Meeting with Dr. Habiba Bougherara regarding sketches,

calculations and material selection March 22 2010

Impact testing/simulation using Granta CES and ANSYS 12 March 25 2010

Meeting with Dr. Habiba Bougherara regarding final material

selection and simulation results March 30 2010

Assign individual tasks for final engineering report and

conference paper March 30 2010

Meeting with Dr. Habiba Bougherara regarding final engineering April 03 2010

report and conference paper

Final engineering report April 05 2010

Conference paper April 05 2010

Conference presentation April 27 2010

Blue- Milestones completed

Red- Milestones behind schedule

Milestones in blue indicate that they have been completed. These have been discussed

with the group on the due date and the next milestone was looked at. An initial meeting was held

with Dr. Bougherara after the proposal was accepted to see what the requirements for the project

were. Once the requirements for the project were laid out, the group met together to decide howtheir skills and experience will be an asset to this project. Since Nishant and Andy are in the

Mechatronics field and have a good amount of experience in ANSYS, they can perform design,

impact testing and simulations. Additionally, Karthik and Matthew are in the Solid State field

and this will help in choosing the right material selection using proper material selection charts

using performance index calculations. The next step was to assign different parts for the interim

report. Each member was assigned a different task to ensure all the requirements for the report

was met. In doing so, every category could be handled at once and not one would be forgotten.

Once this was successful, the next milestone could be carried out.

Milestones highlighted in red show that they have not been completed and hence behind

schedule. This could be because of a number of factors. Since the main focus of the project was

selecting the right materials for the bulletproof vest, Initial Design Sketches was not completed


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on January 22nd

. Any standard bulletproof vest usually covers the torso, shoulder blades and

sides. Therefore, a design was not immediately needed. Hence a conventional bulletproof vest

design was used. Moreover, Background Research could not be completed on February 2nd

because each group member had another project from a different course to work on and so the

milestone had to be delayed for at least a week. Since the milestone was just preliminaryresearch, it did not hold back on any other milestones. Furthermore, most the research was

already conducted when the initial proposal was submitted. Once tasks were assigned to each

individual in terms of writing the report, each group member did a fair amount of research and

finally the report was edited by the team leader.


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5.

References

1. Technical Information. DuPont Kevlar. Dupont.com, Web. 5 Feb 2010.

.

2. "Interceptor Body Armor." Mi li tary. GlobalSecurity.org, Web. 5 Feb 2010.

.

3. "Dragon Skin." Pinnacle Armor, Web. 11 Feb 2010.

.

4. Crane, David. "Dragon Skin Flexible Scalar Body Armor Defeats Rifle

Threats."16/12/2004. Defense Review, Web. 8 Feb 2010.

5. Crane , David. "DefRev Sees Test Data: Dragon Skin Hands-Down Superiorto Armys Interceptor." Defense Review, Web. 8 Feb 2010.

http://www.defensereview.com/defrev-sees-test-data-dragon-skin-hands-

down-superior-to-armys-interceptor/

6. Ashby, M.F.Materials selection in mechanical design. 3rd ed. England: Elsvier

Butterworth-Heinemann, 2005. 103. Print.

7. "Body Armor." 16/12/2004. njlawman.com, Web. 8 Feb 2010.

.

8. Comet, Marc, Loc Schmidlin, Benny Siegert, and . "Nanoscale deposition of Kevlar by

sublimation."Elsevier B.V.63.2 (2009): 279. Web. 11 Feb 2010.

.

9. AFSHARI, MEHDI, DOETZE SIKKEMA, KATELYN LEE, and MARY BOGLE.

"High Performance Fibers Based on Rigid and Flexible Polymers." Taylor & Francis

Group48.2 (2008): 230-274. Web. 11 Feb 2010.

.

10. "BodyArmor 101." BodyArmor.com, Web. 11 Feb 2010.

.


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11."Dyneema." Matbase, Web. 11 Feb 2010.

.

12.Spectra Fiber. Honeywe ll . Honeywell.com, Web. 5 Feb 2010.

.

13.

"Fiber Properties." Bally Ribbon Mills, Web. 11 Feb 2010.

.

14. "WEIGHT-MINIMIZED CERAMIC BODY ARMOR." ESK, Web. 11 Feb 2010.

.

15.Boron Carbide. de.academic.ru, Web. 5 Feb 2010.

.

16.

Vogt, R.G., Z. Zhang, T.D. Topping, E.J. Laverniaa, and J.M. Schoenung. "Cryomilledaluminum alloy and boron carbide nano-composite plate."Journal of Materials

Processing Technology. 209.11 (2009): 5046-5053. Print.

17."Alumina Oxide Used in Rods & Tubes." TQ Abrasive Machining, Web. 11 Feb 2010.

.

18."Aluminum Oxide." Accuratus, Web. 11 Feb 2010.

.


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6.

Appendix

Figure 1 Typical Properties of KEVLAR 29 and 49 yarns [1]


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Figure 2 Comparative Properties of KEVLAR vs. other yarns [1]

Figure 3 Effect of Elevated Temperatures on the Tensile Strength of KEVLAR 29[1]


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Figure 4 Comparative Effect of Elevated Temperatures on the Modulus of Various Yarns [1]

Figure 5: Boron Carbide used for Dragon Skin Figure 6: Deltoid and Axillary Protectorsbody armor [4] (DAP) [5]


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Figure 7 Boron Carbide Compound [15]

Figure 8 Honeywell Spectra Fibers[12]

Figure 9: Area density of ceramic composite systems [14]

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