The 3rd Conference of the National Campaign for Textile Industries NRC, Cairo; 9th – 10th March 2015 “Recent Manufacturing Technologies and Human and Administrative Development”
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Performance of Weave Structure Multi-Layer Bulletproof Flexible Armor Magdi El Messiry and Shaimaa El-Tarfawy Textile Department, Faculty of Engineering, Alexandria University, Alexandria, Egypt
Abstract
B
ody armor is the most critical piece of protective equipment for police officers for soldiers in the battlefield as well as the civilian subjected to fragments of materials in the working place. The design of the soft armor must insure the protection, the flexibility and the comfort. These requirements may be contradicting. The soft armor usually made of multi-layer high performance Synthetic fibers designed to prevent high-velocity ballistic impacts of projectiles high-powered rifles. The increase of the weight of the armor reduces its comfort and increases its protection ability. In this work several designs of armor are suggested.The protective power of typical ballistic fabrics, when assembled into multi-layered designed to absorb high velocity ballistic impacts, are improved by different ways. Copyright_AGA©2015 TRD, NRC, All Rights Reserved.
1. Introduction In the field of protective clothing, many different materials are used to provide bullet proof, tear and puncture resistance where high levels of stiffness and shear resistance are important for designed vests for protection; moreover, a soft vest should provide comfort for the user, a light weight, and cost-effectiveness. The ballistic personal protective equipment design is made of multiple layers of fabric. The inside padding is made of multiple layers fabric of antiballistic high performance fibers. They are high-modulus, hightenacity (HM-HT) fibers. Needle punching nonwoven antiballistic fabric structure allows greater compressibility than woven fabrics and therefore more impact protection. Also, the fiber orientation can be controlled and aligned to improve strength, while still maintaining flexibility. For soft body armor requiring fewer anti-ballistic layers in manufacturing, the vests are less costly than other anti-ballistic armor, and they weigh less, about 3.5 kg, which improves comfort. Vests for Police officers, helps protect from death or serious injury with an ever-growing line of products designed to help defend against ballistic projectiles. Bulletproof
materials at the moment are designed to spread the force. Most anti-ballistic products, like bullet-proof jackets are currently made of multiple layers of Kevlar, fibers which stop bullets from penetrating by spreading the bullet's force. The suggested innovation of this project is to design the multilayer fabric in such composite form that will use between layer materials helping to absorbed more energy with lower fabric deformation. New bullet proof material will actually rebound the force of a bullet. In order to improve the bullet resistance of protective fabric, multi-layer pad, highly preformed woven net, and traixial fabrics are used as supporting layers . Protective materials gain large acceptance in defense related areas. One of these areas is the personal protection where a soft vest is used. The basic requirements for the soft vest are ballistic performance, providing comfort for the user, a light weight, and cost-effectiveness. To fulfill these requirements, the important factors are highperformance fiber, fabric formation and layered structures (1–6). It is necessary to understand the mechanism of yarn pull-out and the role of yarn pull-out friction
*Corresponding author: Magdi El Messiry Address: Textile Department, Faculty of Engineering, Alexandria University, Alexandria, Egypt E-mail address:
[email protected]
Magdi El Messiry et al
in the fabric to enhance ballistic performance. Yarn pull-out is defined as one end of the yarn pulled out of the fabric structure by the motion of the bullet penetrates. The force required to pull the yarn from the fabric structure is the sum of the frictional forces between the yarns sets at all the intersecting points (7-10). Some studies demonstrate that 3D composites have high ballistic impact damage resistance and low velocity impact protection.(11–13) A higher performance of 3D structural composites compared to 2D laminates has also been revealed.(14) Taking into account the impact studies achieved on 3D woven composites,(15-18) high performance has been revealed due to their resistance to delaminating.(19,20) The 3D angle interlock fabric displays high strength and damage resistance as a consequence of the interlaced structure of the warp and weft between the adjacent layers.(21) Low velocity impact properties of 3D woven composites are important for their various applications. This type of loading can occur when tools are dropped on the surface of a composite or when the material is impacted by debris, fragments, or projectiles. In a recent study, two types of 3D woven Basalt/Aramid hybrid composites with similar fiber volume fraction and dimension have recently been tested. Postmortem photographic analysis indicated that inter-ply hybrid failed in a layer-by-layer mode, leading to much larger energy absorption, while intra-ply composite showed a brittle mode, resulting in significantly lower energy absorption.(22) It can also be noticed that 3D textile structural composites are much tougher between layers because many reinforcing yarns exist in the through-thickness direction.
Table (1) material specifications Fabric no
1
Several materials are used in form of woven fabrics, knitted fabrics and triaxial fabrics. In this work several samples were made of the following fabrics with the specifications given in Table (1):
Materi al
Weave Yarns per cm
Yarn count tex
Fabric weight (gm/m2 )
100% Cotton
20ends/c m, and 20picks/c m
Warp =11.8 Weft =19.5
85
kevlar
15ends/c m, and 15picks/c m
200
385
Polyest er texture d contin uous filame nt yarn
15 wales/cm 16.2 courses/c m
20
200
Polyest er
Open Basic 3.6 X3.6 X 3.6
144
166
Paraaramid ® 29
Open Basic 3.6 X3.6 X 3.6
167
196.7
victran
Open Basic 3.6 X3.6 X 3.6
140
199
Contin uous filame nt Carbon fibers
( type M46JB)(1 200050B)
Plain weave
2 Plain weave
3
Single Jersey knitted 16% LYCRA
4
Triaxial Basic Weave
5
6
Triaxial Basic Weave
Triaxial Basic Weave
7 fibres
-
Para-aramid Kevlar 29, the yarn counts 167 tex, tenacity 203 cN/tex, and breaking elongation 3.6%.
-
Polyester, the yarn counts 144 tex, tenacity 80 cN/tex, and breaking elongation14.5%.
2. Experimental 2.1. Materials
Fabric Type
- Vectran filament, the yarn counts 140 tex, tenacity 233 cN/tex, and breaking elongation 3.8%.
2.2. Armor design The armor samples were designed in order to test the behavior during bullet shooting. a circular fabric sample with diameter (20 cm) was fixed on the apparatus .It was used different fabrics woven fabrics, knitted fabric, and tri-axial fabrics, and carbon fibers shown in tables (2). Multi layers of different fabrics were prepared to catch the bullet in flight and disperse the energy of its impact.
•
Woven fabric of cotton from warp yarns 11.8 tex and weft yarns 19.5 tex , ends/cm 20, and picks/cm 20.
•
Woven fabric of Kevlar from warp and weft yarns 200 tex, ends/cm 15, and picks/cm 15.
•
Single jersey knitted fabrics made of textured polyester multi- filament of count 20 tex with 16% Lycra.
2.3. Experimental setup
Triaxial woven fabrics from different types of fibers. Triaxial pattern is basic with a count of 9 yarns/inch (3.6 yarns/cm) in all three axes.
The test stand shown in figure (1) consists of gun to shoot the bullets; holder to fix the sample on it with 20 cm diameter, bullet protector shield, the distance between the gun and the frame is 50cm, and a can to catch the bullet.
•
Figure (1) shows the setup constructed to test the different armor samples.
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Figure (1) Experimental setup
11
Table (2) armor designs Sampl e Code
Armor design
1
2 layers of fabric 1
2
1 layer of fabric 1 1 layer of fabric 3
3
1 layer of fabric 1 Particles of rubber 1 layer of fabric 3
4
3 layers of fabric 4
1 layer of fabric 6 1 layer of carbon fibers 7 1 layer of fabric 6
12
1 layer of fabric 4 with stitches using fibers 7 1 layer of fabric 4
13
1 layer of fabric 5 with stitches using fibers 7 1 layer of fabric 5
14
1 layer of fabric 6 with stitches using fibers 7 1 layer of fabric 6
Armor designs
3. Results and Discussion
5
3layers of fabric 4 1 layer of fabric 3
6
1 layer of fabric 2 Particles of rubber 2 layers of fabric 4 1 layer of fabric 3
7
8
9
10
1 layer of fabric 2 2 layers of fabric 4 1 layer of fabric 3 1 layer of fabric 1 Particles of rubber 1 layer of carbon fibers 7 1 layer of fabric 1 1 layer of fabric 4 1 layer of carbon fibers 7 1 layer of fabric 4 1 layer of fabric 5 1 layer of
Analyses of the penetration mechanisms Punching mechanism observed in our experimental work indicated the following possible situations illustrated in figure (2),
Figure (2) trajectory of the bullet through the fabric.
Case A: Bullet tip punches the fabric between the threads, hence sufficient space allows it to pass, as in the case of fabric with low density in weft and warp, so that the yarns will move in different directions permitting bullet tip to pass through without fiber or yarn damage. Case B: Bullet tip punches the fabric between the threads without cutting matrix, pushing the yarns aside without cutting it. The bullet will subjected to the friction between the yarns and the bullet body pressing the yarns with the increase of the pressure on the bullet increasing the friction. If force created by the bullet on the fabric is less than the breaking strength, fabric will form cone. Increasing in the size till the total bullet kinetic energy is less than the fabric deformation energy. Otherwise, the yarns will break and the bullet will pass through. The absorption energy depends on the stretch of the fabric.
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Case C: For tight fabric near the jamming condition, the yarns start to be cut by bullet tip. If the strike energy is higher than fabric resisting energy, the bullet will pass completely though the
fabric. In this case, the absorption energy of the fabric will be a function of sonic speed of the yarns(23). 5. EJ: Energy to overcome friction between bullet body and yarns. 6. EM: Energy to deform the fabric during impact. Therefore, the total absorbed energy by the fabric is expressed as
Figure (3) sketch of the fabric deformation under bullet impact
The deformation of the fabric in the zone of bullet contact with the fabric into three zones illustrates in figure (3); in zone I contact with the tip of the bullet, zone II around the tip of the bullet zone III, the fabric deformation zone forming the fabric cone. The propagation of the strain in the yarns determines the fabric absorption energy to stop bullet . 3.1 Energy balance for fabric under impact by bullet The straight way to evaluate the impact performance of a fabric is to calculate its energy absorption. Hence, the kinetic energy Ebefore impact before impact of the bullet before impact will be equal to the sum of the kinetic energy Eabsorbed absorbed by the fabric and kinetic energy Eafter impact of the impactor after impact. Therefore Eabsorbed = Ebefore impact + Eafter impact (1) The energy lost during impact Eabsorbed is given by (24) Eabsorbed
=
M (2)
(V12
-
V22)
Where Eabsorbed is the kinetic energy absorbed by the fabric, V1 is the velocity of the impactor before impact, V2 is the velocity of the impactor after impact, and M is the mass of the impactor. Kinetic energy absorbed by the fabric Eabsorbed is defined by the following six different components (23) : 1. ES: Energy to shear the yarns. 2. ED: Energy to deform all other yarns. 3. ET: Energy to tensile failure of directly impacted yarns. 4. EF: Energy to overcome friction between fabrics layers and energy absorption layers (multi-layer armor)
Eabsorbed = ES +ED + ET + EF + EJ + EM (3) During the interval of impacting time, the value of punching force will increase till full penetration, and then it will gradually decline and vanish after bullet pass through fabric.to increase EJ several designs is used to add absorbing media between the layers of the fabric in the armor vest, while most of the designed tending to use high tenacity yarns with high value of young’s modulus and low density (23). EF is depends on the fabric tightness as well as the coefficient of friction between the bullet and yarns. In order to increase the absorption energy of the fabric, it is expected evolving each component of the fabric absorption energy, if it is possible, such as use a multilayer fabric energy absorption layers , ‘‘EF,’’ the yarns with high cutting resistance ‘‘ES,’’ increasing the friction between the blade and the yarns ‘‘EJ.’’ Moreover, the application of fibrous pads, as a friction media, will increase the contact area between the bullet and fibers (25). This will lead to the rise of the energy components ‘‘EJ’’ and ‘‘EF.’’ The use of yarns which can propagate the strain at higher velocity will attain the increase in the resisting energy component ‘‘ED’’ value. These components of the absorbed energy will depend on fabric structure and specifications as well as yarn properties (26). The velocity of strain propagation can be calculated by the following equation (27)
V = √E/ ρ (4) Where: V longitudinal wave speed in m/s, E fiber modulus in Pa, and ρ the yarn bulk density in g/m3 . In impact, faster moving longitudinal waves help to scatter the impact energy through the yarns intricate at the impact area (26). 3.2 Effect of armor design As mentioned earlier, the mechanism of failure of the fabric under bullet impact is different; it depends on cutting resistance of the fiber by the penetrating bullet, which is proportional to the tensile properties, shear modulus, and on the yarn work of rupture. El Messiry (23) introduced, a new index (equation 5) for evaluation of the fiber impact capacity was suggested in order to rank the fibers
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energy absorption capacity index (FEACI) to be the product of fiber tenacity and strain wave velocity. FEACI
=
(T
* (5)
V)
(N/m
s
)
From the above analysis of the basic requirement of the flexible bullet prove armor the following parameter should be considered; 1.
Where, T is the fiber tenacity in ‘‘GPA’’ and V is the longitudinal wave speed ‘‘m/s’’
2. 3.
Using fabrics with high value of sonic velocity Multi-layers design Using energy absorption material
Table (3) analysis of the different designs Sample Code
Behavior of the armor design
1
Penetrated layers 1and 2
2
penetrated layer 1 .The knitted fabric (3) made it reversed in the opposite direction
3
penetrated layer 1 after that the particulars of rubber decreased the velocity of bullet and stopped it
4
penetrated layers 1, 2 and 3 pulling some yarns outside the fabric structure
Shape of deformation after shooting
Result
Full Penetration
Figure (4) FEACI index for different types of fibers
Figure (4) presents values of ‘‘FEACI’’ for different high performance fibers. For armor design the equation (5) may be modified to be =
K
(
T
*
V ) (6 )
(N/m
s
)
No Penetration
Where, K armor design coefficient. The design K reflecting the number of layers of fabric used as well as the fabric structure. In the case of multi-layer armor the total fabric areal density N the total absorption energy will be =
N*
K
(T
*
V)
(7) Some designs of the armor using energy absorption materials between fabrics. Consequently deformation of such material will absorb part of the built energy as shown in figure (5) increasing the total material Eabsorbed.
No Penetration
Penetration
E absorbed
Bullet trajectory through absorption materials
5
penetrated layers 1, 2, and 3 after that knitted fabric(3) stopped the bullet not be penetrated
6
penetrated layer 1difficulty then The bullet stopped at particulars of rubber
No Penetration
No Penetration
Figure (5) effect energy absorption material on the total E absorbed
3.3 Analysis of the different designs The 3rd Conference of the National Campaign for Textile Industries
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7
8
penetrated layers 1, 2, and 3 after that The bullet stopped at knitted fabric(3)
penetrated layer 1 and The bullet stopped at the fibers and particulars of rubber
14 No Penetration
The pullet penetrated the 2 layers of fabrics making long loop after penetration
Penetration
Fourteen samples used to verify the above vision (1 gm) bullet is used with speed and the trajectory of the bullet was analyzed. Table (3) gives the analysis in each case. No Penetration
4.
General Remarks 1. The bullet did not penetrate samples No (2, 3, 5, 6, 7, and 8).
9
10
11
12
13
The pullet penetrated the 2 layers of fabrics making small loop after penetration
The pullet penetrated the 2 layers of fabrics making small loop after penetration
The pullet penetrated the 2 layers of fabrics making small loop after penetration
The pullet penetrated the 2 layers of fabrics making long loop after penetration
The pullet penetrated the 2 layers of fabrics making long loop after penetration
2. It is illustrated that in sample No (2) the bullet penetrate the first layer only, it is because the fabric was light with 85 gm/m2 .In the other side, the single jersey knitted fabric with 16% lycra absorbed the kinetic energy the didn’t be penetrated.
Penetration
3. Using particles of rubber had a great effect in Sample no (3).It is due to the friction between the particles and the bullet during its penetration decreased the velocity of the bullet and absorbed it kinetic energy. Penetration
4. Polyester Triaxil structure allowed the bullet to penetrate in sample no (5) because of its open spacing and light weight 166 gm/m2 but the single jersey knitted fabric with 16% lycra stopped the bullet. 5. Sample No (6) was the most effective once of the samples. The bullet passed difficulty in the Kevlar fabric because of it high strength, closed spacing, and heavy fabric weight 385 gm/m2 after that the layer of carbon fibers caught the bullet and stopped it.
Penetration
6. Kevlar fabric in sample No (7) was penetrated difficulty but using the polyester triaxial fabric structure with its open spacing allowed to continuous the penetration after that the single jersey knitted fabric with 16% lycra stopped the bullet.
Penetration
7. Using carbon fibers with particles of rubber absorbed the kinetic energy of the bullet in sample No (8) so the multi layers fabric not be penetrated.
Penetration
5. Conclusions Using Particulars of rubber and knitted fabrics with 16% lycra increased the absorption of the kinetic energy of the bullet. Using Kevlar in plain
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weave structure gives better results than traxial weave structure, because the fabric was tighter to decrease the velocity of bullet. Using Kevlar pain weave fabric structure with a layer of carbon fiber was the most effective sample.
6. References 1. Bilisik, A. K., Design of Multifunctional Ballistic Structures, in “Land Force Symposium, Istanbul” (Language: Abstract: English), 1998. 2. Yildiray, T., “Design of Ballistic Fabrics”, MSc Thesis, University, BorNova-Izmir (Language: Turkish, Abstract: English), 1999. 3. Bilisik, A. K., Structure-property Relations to the Structures, in “I. National Textile Symposium, Denizli” Language: Turkish, Abstract: English), 1997. 4. Babcock, W., and Rose, D., Composite Preforms, AMPTIAC Newsletter, 5(1), 7– 11 (2001). 5. Stein, W., and Zhan, H., Construction and Action Resistant Vests, Melliand Textilberichte, 6, 463–468 (1981). 6. Lane, R. A., High Performance Fibers for Personnel and Vehicle Armor Systems, AMPTIAC Quarterly, 9(2), 3–9 (2005). 7. Wilde, A. F., Roylance, D. K., and Rogers, M., Photographic Investigation of HighSpeed Missile Impact upon Nylon Fabric, Part I: Energy Absorption and Cone Radial Velocity in Fabric, Textile Res. J., 43, 753– 761 (1973). 8. Kirkwood, K. M., Kirkwood, J. E., Lee, Y. S., Egres, R. G., Wetzel, E. D., and Wagner, N. J., Yarn Pull-out as a Mechanism for Dissipation of Ballistic Impact Energy in Kevlar KM- 2 Fabric, Part I: Quasi-static Characterization of Yarn Pull Out, Army Research Laboratory ARL-CR-537 (2004). 9. Kirkwood, K. M., Kirkwood, J. E., Lee, Y. S., Egres, R. G., Wetzel, E. D., and Wagner, N. J., Yarn Pull-out as a Mechanism for Dissipation of Ballistic Impact Energy in Kevlar KM- 2 Fabric, Part II: Prediction of Ballistic Performance, Army Research Laboratory ARL-CR-538 (2004). 10. Mulkern, T. J., and Raftenberg, M. N., Kevlar KM2 Yarn and Fabric Strength under Quasi-static Tension, Army Research Laboratory ARL-TR-2865 (2002). 11. Miravete A. 3D textile reinforcements in composite materials. Cambridge (UK): Woodhead Publishing Limited, 1999. 12. Bahei-El-Din YA and Zikry MA. Impactinduced deformation fields in 2D and 3D woven composites. Composite Sci TechNo l; 63: 923- 942, (2003). 13. Chou S, Chen HC and Chen HE. Effect of weave structure on mechanical fracture
The 3rd Conference of the National Campaign for Textile Industries
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
behavior of three-dimensional carbon fiber fabric reinforced epoxy resin composites. Composite Sci TechNol; 45: 23–35, (1992). Baozhong S, Bohong G and Xin D. Compressive behavior of 3-D angle interlock woven fabric composites at various strain rates. Polymer Testing; 24: 447–454, (2005). Khalid AA. The effect of testing temperature and volume fraction on impact energy of composites. Material Design 2006; 27: 499– 506. Baucom J and Zikry M. Low-velocity impact damage progression in woven E glass composite systems. Composite: Part A; 3: 658–664, (2005). Chou S, Chen H-C and Wu C-C. BMI resin composites reinforced with 3D carbon-fibre fabrics. Composite Sci TechNol; 43: 117– 128, (1992). Naik NK and Sekher YC. Damage in wovenfabric composites subjected to low-velocity impact. Composite Sci TechNol ; 60: 731– 744 (2000). Chou TW and Ko FK. Textile structural composites. Amsterdam: Elsevier Science Publishers B.V., pp.140–142, (1989). Mouritz AP, Baini C and Herszberg I. Mode I interlaminar fracture toughness properties of advanced textile fibreglass composites. Composites Part A: Appl Sci Manufacturing; 30(7): 859–870, (1999). Ko FK. Three-dimensional fabrics for composites. Textile structural composites. Amsterdam: Elsevier Science Publishers B.V., 1989, pp.129–171. Wang X, Hu B, Feng Y, Liang F, Mo J, Xiong J, et al. Low velocity impact properties of 3D woven basalt/ aramid hybrid composites. Composites Sci Tech No l; 68: 444–450, (2008). El Messiry M. and Eltahan E. , Stab resistance of triaxial woven fabrics for soft body armor, Journal of Industrial Textiles, : (1–21), 2014. Dhakal HN, Zhang ZY, Richardson MOW, et al. The low velocity impact response of Non-woven hemp fibre reinforced unsaturated polyester. Composites 2007; 81: 559–567, (2007). El Messiry M. ,Investigation of puncture behavior of flexible silk fabric composites for soft body armor. Fibres Text Eastern Eur J ; 22, 5(107): 71–76, (2014). Sun D and Chen X. ,Plasma modification of Kevlar fabrics for ballistic applications. Text Res J. Epub ahead of print 11. DOI: 10.1177/0040517512450765, (July 2012). Tan VBC, Shim VPW and Zeng X. ,Modeling crimp in woven fabrics subjected to ballistic impact. Int J Impact Eng; 32: 561–574(2005).
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