Static and dynamic puncture behaviors of compound fabrics with recycled high-performance Kevlar fibers

Static and dynamic puncture behaviors of compound fabrics with

recycled high-performance Kevlar fibers

Ting-Ting Li

, Rui Wang

, Ching-Wen Lou

, Jia-Horng Lin

a

School of Textiles, Tianjin Polytechnic University, Tianjin 300387, China

b

Institute of Biomedical Engineering and Material Science, Central Taiwan University of Science and Technology, Taichung 40601, Taiwan

c

Laboratory of Fiber Application and Manufacturing, Department of Fiber and Composite Materials, Feng Chia University, Taichung 40724, Taiwan

d

School of Chinese Medicine, China Medical University, Taichung 40402, Taiwan

e

Department of Fashion Design, Asia University, Taichung 41354, Taiwan

* Corresponding author. Tel.: + 886 4 24518661; fax: +886 4 24510871.

E-mail address: [email protected] (J.H. Lin).

ABSTRACT

An economical and flexible compound fabric was prepared using Kevlar fabric

and glass fabrics as well as recycled Kevlar/Nylon/low-T

polyester

nonwovens via needle-punching and thermal-bonding processes. Effects of

Kevlar staple fibers fraction, number of layers and inter-laminar bonding on the

static and dynamic puncture resistances were comparatively studied. Findings

indicate that increase of Kevlar staple fibers fraction improved static puncture

resistance more significantly, but inter-laminar shear effect influenced on

dynamic puncture resistance more evidently. With 20 wt% recycled Kevlar

fibers, static puncture resistance had linear relation to number of layers, but

dynamic puncture resistance showed a parabolic relationship. The contacting

pressure and friction strength of compound fabric to probe was to resist against

static puncture resistance, but mechanism for dynamic puncture resistance was

due to fiber elongation of fabric interlayer and compactness of compound

fabric. Yarn brittle-breakage was the main dynamic puncture resistance mechanism for G-CF, but pushing fiber apart was for K-CF, besides of contact pressure of probe to compound fabrics. The improved both of static and dynamic puncture resistances were attributed to cut resistance of Kevlar fibers and compactness of fiber assembles. Comparatively, cut resistance property of Kevlar fibers related to dynamic puncture behavior more significantly, but fiber compactness affected static puncture resistance obviously.

Keywords: A. Recycling, A. Fabrics/textiles, B. Mechanical properties, D.

Mechanical testing.

1. Introduction

Body armor, that is used to defend against threats from bullets, impacts, sharp weapons, knives and explosions, has been attracted by both of the individual and scientific researchers [1]. Many researchers have focused on studies about ballistic resistance body armor, ranging from experimental investigation [2-10], analytical model [11-17] and FEM simulations [18-23]

and their combinations. Comparatively, fewer studies have investigated on puncture resistance property of composites in the past years.

All over the world, most countries have take action to gun control to avoid personal injury. At the same time, puncture assault increases significantly along with gun control, consequently occurring higher risk [24, 25]. Moreover, it is reported that puncture weapons have sharper tip and thus contacts with composites smaller than bullets, making harder protection for puncture resistance [25]. Therefore, great interests from all over the world have been shown in puncture-resistance armor [26].

In early stage, some rigid materials such as metal sheet, ceramic plate, or titanium foil were inserted in armor interlayer to resist against puncture attacks.

But these are bulky, inflexible and uncomfortable to wearers, impossible to be

prevalent in police and military applications. As invention of Dupont’s Kevlar

fiber, its high-count and high-density fabrics were commonly used as soft body armor after multiple-layer lamination. But due to its cost, many researchers have devoted themselves to improve puncture resistance of fabric by windowing reduction, including resin impregnation [25, 27], and shear thickening fluid (STF) coating [28, 29]. However, rein impregnation leads to rigid armor, air impermeability and bad wearing performance. And STF coating is unapparent to resist against static puncture resistance. Therefore, the purpose of our study is to prepare a flexible, breathable and economical compound fabric with static and dynamic puncture resistance property.

In our previous study, we have optimized the process parameters of Recycled Kevlar/Nylon/ Low-T

PET nonwovens [30], and confirmed the reinforcing effect of fabric on puncture resistance property [31]. This paper aims to use nonwoven whose fiber compositions is same as before, and fabric interlayer to form flexible compound fabrics via needle-punching and thermal- bonding process. Nonwoven fibers were penetrated into fabric interspace increasing fiber’s volume fraction, and bicomponent low- T

PET fiber produced bonding-point fixing fiber’s original position and simultaneously improving composite’s comfortability. Under effects of Thickness- reinforcement and thermal-bonding, the resulting compound fabrics had excellent static and dynamic puncture resistance. Present study focused on effects of recycled Kevlar fiber loading, number of layers and inter-laminar shear on static and dynamic puncture resistances of compound fabrics, and static and dynamic puncture resistance mechanisms of compound fabrics.

2. Experimental 2.1. Raw Materials

Recycled Kevlar fibers in length of 50 ～ 60 mm were acquired from

unidirectional selvages (provided by Dupont Company, USA). Nylon 6 fibers purchased from Taiwan Chemical Fiber Co. Ltd, Taiwan, had fineness of 6 D, length of 64 mm and tenacity of 10 g/d. The sheath-core low-T

PET fibers were offered by Huvis Chemical Fiber Corp., Korea. Their sheath material was low-T

PET with 110 ℃ melting point, and the core was PET with 265 ℃ melting point. KN2600N1 glass fabric composed of 1100 D glass yarn was acquired from Jinsor-Tech Industrial Corp., Taiwan. EK10 Kevlar fabric made by 1500 D yarn was provided by Formosa Taffeta Co. Ltd, Taiwan. The specifications of glass and Kevlar fabric are both shown in Table 1.

Table 1

Physical and mechanical properties of Glass and Kevlar fabric.

Fabric Structur e

Density (/inch)

Maximum Tensile Force (N)

Elongation (%)

Modulus (GPa) Glass Plain 34 × 26 606.10

, 514.45

5.26

,3.18

1.46

,2.05

Kevla

r Plain 28 × 28 2627.52 7.00 4.76

a

shows warp direction.

represents weft direction.

2.2. Compound Fabrics Preparation 2.2.1 Nonwoven manufacture

Kevlar/Nylon/Low-T

Polyester nonwoven was manufactured via opening, blending, carding, lapping and needle-punching process. The areal weight of nonwoven was 200±10 g/m

, and its needle-punched density was 100 needles/cm

. The blending ratios of recycled Kevlar fiber and nylon fibers ranged from 0/70, 10/60, 15/55 to 20/50 wt%. And low-T

polyester fiber was constant at 30 wt% as referred in [30]. After static and dynamic puncture evaluations, effect of recycled Kevlar fiber fraction on puncture properties was discussed and thus optimal blending fraction of fibers was determined.

2.2.2 Compound fabric manufacture

Double layers of nonwovens, and one layer of fabric interlayer (glass and

Glass fabric

G-CF (b) K-CF

(c) 1K/4G Compound Fabric

Nonwoven fabric Nonwoven fabric

K-CF

G-CF G-CF G-CF G-CF

Kevlar fabric

Kevlar fabric) were needle-punched together at 150 needles/cm

forming single-layer compound fabric. After that, compound fabric was thermo-bonded at 150 ℃ through 1.5-mm-gap Twin-roller Hot-presser with velocity of 0.5 m/min. Herein, nonwovens inter-layered with glass fabric or Kevlar fabric were respectively called as glass compound fabric (G-CF), and Kevlar compound fabric (K-CF) as shown in Fig. 1a and 1b. And then effects of number of layer, K-CF position and inter-laminar shear on static and dynamic puncture resistance behaviors of G-CF and K-CF was comparatively investigated. To confirm whether inter-laminar shear influenced on puncture behaviors of multi- layer compound fabrics, one-layer K-CF and four-layer G-CF were integrated together into 10-mm-thickness compound fabrics through Flat Hot-presser at 150 ℃ for 5 min , which considered as the control group. Composition structure of 1K/4G composite has shown in Fig. 1c. All samples and their codes are displayed in Table 2.

Fig. 1. The constitution of G-CF (a), K-CF (b) and 1K/4G compound fabric (c).

1K/4G compound fabric was composed of single-layer K-CF and four layers of

G-CF.

Table 2

The samples’ codes and their descriptions.

Sample code

Total layers

Number of G-CF (layer)

Number of K- CF (layer)

K-CF position

5G 5 5 0 －

5K 5 0 5 1

, 2

, 3

, 4

, 5

1K/4G 5 4 1 1st

1G/1K/3

G 5 4 1 2

2G/1K/2

G 5 4 1 3

3G/1K/1

G 5 4 1 4

4G/1K 5 4 1 5

2.3. Static and dynamic puncture tests

Static puncture test was conducted by Instron 5566 Universal Tester (Instron, USA) according to ASTM F1342-05. Probe A (shaft radius of 0.25 mm and conical angle of 26°) was fixed on the load cell and moved at 508 mm/min. This puncture instrument has shown in Fig. 2a [31]. Samples were 100 mm × 100 mm and placed between two circular plates with 10 mm- diameter hole in the center. Six specimens were measured in each group.

Dynamic puncture test was carried out by Drop-Tower Machine (GuangNeng Machinery Co. Ltd, Taiwan) attached with PCD300A data acquisition (Sanlien Corp., Taiwan) according to NIJ Standard 0115.00. The testing equipment has shown in Fig. 2b [31]. In order to achieve Protection Level 1—E1 Strike Energy (24J), the spike (0.07 mm shaft radius and 24°

conical angle) loaded by 2.8 kg dropped from 284 mm height onto surface of

samples. Likewise, 100 mm × 100 mm samples were clamped between two

square plates with 40-mm-diameter hole in the center. Six specimens were also

measured in each group.

Fig. 2. Static (a) and dynamic (b) puncture instruments [31].

3. Results and discussion

3.1. Effect of recycled Kevlar fibers fraction

As mentioned in [32], puncture resistance was defined by multiplying puncture resistance force on the thickness and that on the areal weight. This means that puncture resistance property is closely related to areal weight and thickness of materials. With increase of recycled Kevlar fibers, the number of staple fibers among nonwovens was changed and thus thickness of compound fabrics was also variational. In other words, fraction of recycled Kevlar fibers influences on thickness of resultant compound fabrics. Therefore, in this study, puncture resistance is determined that puncture resistance force was divided by volume density, namely N/(g/cm

), in order to ignore thickness effect on puncture resistance property.

Fig. 3 shows static and dynamic puncture resistances of G-CF and K-CF as increase of recycled Kevlar fibers. As seen in Fig. 3a, static puncture resistance reinforced with recycled Kevlar loadings for both G-CF and K-CF.

But this reinforcement of Kevlar fibers was slighter for dynamic puncture resistance of G-CF compared to static puncture resistance as depicted in Fig.

3b. The improvement of static puncture resistance with recycled Kevlar fibers

(a) (b)

could be attributed to two reasons. Firstly, 1.2 D Kevlar staple fiber is marginally finer than 6 D Nylon fiber, and more fibers were included in compound fabrics at the same areal weight as recycled Kevlar fibers increased.

Therefore, fiber density of compound fabrics was improved, leading to larger pushing force and friction strength to probe during puncture process [33].

Secondly, Kevlar staple fiber had superior modulus, impact resistance and anti- shearing properties to Nylon 6 fiber. Therefore, during puncture process, deformation energy of compound fabrics transferred along fibers and yarns quickly [33], and simultaneously puncture tip became passivity because of cut resistance to probe [34]. Based on above, static puncture resistances of G-CF and K-CF with 20 wt% Kevlar fibers were improved by 41.87% and 33.83%

respectively comparing with that with 0 wt% fibers loading. It is also found that with same areal weight, K-CF and G-CF with 20 wt% Kevlar fibers had improvement of sixty-two and twenty-three times respectively for static puncture resistance compared to Kevlar and glass fabrics as displayed in Table 3. This shows that thickness-reinforcement structure of compound fabric is effectively positive to resist against quasi-static puncture behaviors.

For K-CF, increased volume density, improved shear resistance and higher puncture wave velocity due to addition of Kevlar staple fibers insignificantly influenced on dynamic puncture resistance after 24 J puncture impact. Therefore, dynamic puncture resistance remained almost unchanged with increase in recycled Kevlar fibers as depicted in Fig. 3b, indicating that recycled Kevlar fibers insignificantly affected dynamic puncture resistance of K-CF.

Comparatively, K-CF had higher both static and dynamic puncture

resistances than G-CF at the same fractions of recycled Kevlar fibers. This is

because Kevlar fabric had higher cut resistance and larger wave velocity than

Glass fabric, and more transformed energy and anti-shearing energy were

produced to resist against puncture energy. And standard deviation of dynamic

puncture resistance showed higher for K-CF than G-CF. This can be explained that Kevlar fabric had lower yarn density than Glass fabric, and puncture probability that probe tip contacts with fiber of compound fabric was smaller for K-CF than G-CF.

0 10 15 20

0 50 100 150 200 250 300 350

400 G-CF K-CF

Recycled Kevlar Staple Fiber (wt%)

S ta ti c P u n ct u re R es is ta n ce ( N /( g/ cm 3) )

0 10 15 20

0 50 100 150 200 250 300 350

400 _{G-CF K-CF}

Recycled Kevlar Staple Fiber (wt%)

D yn am ic P u n ct u re R ei si st an ce ( N /( g/ cm 3) )

Fig. 3. Static (a) and dynamic (b) puncture resistances of single-layer G-CF and K-CF with different proportions of recycled Kevlar staple fibers (0, 10, 15, 20 wt%).

Table 3

(a)

Static puncture property of single-layer Kevlar and Glass fabric.

Fabric Area weight (g/m

)

Thickness (mm)

Static puncture force （N）

Static puncture resistance (N/(g/cm

)) Kevla

r 227 0.32 1.073  0.083 1.512  0.117

Glass 328 0.31 5.177  0.066 4.893  0.627

3.2. Effect of number of layers

As mentioned above, recycled Kevlar fiber fraction significantly related to static and dynamic puncture resistances of G-CF. Therefore, as number of layers increases, static and dynamic puncture resistances of G-CF with different recycled Kevlar fibers were revealed in Fig. 4. Apparently, whatever recycled Kevlar fibers contained in nonwoven, static and dynamic puncture resistance respectively showed a steady increase with number of layers. When number of layers reached five, G-CF with 20 wt% recycled Kevlar fibers had the highest static and dynamic puncture resistance, 833 N/(g/cm

) and 1589 N/

(g/cm

) respectively. Moreover, with more addition of recycled Kevlar fiber, climb slop that static puncture resistance related to number of layers displayed higher as shown in Fig.4a. And dynamic puncture resistance in Fig.4b also had linear dependence on numbers of layers when recycled Kevlar fibers increased from 0 wt% to 15 wt%. When recycled Kevlar fiber increased to 20 wt%, the fitting relations of static (Y

) and dynamic (Y

) puncture resistances of G-CF as regard to number of layers (X) is plotted in Figs. 5-6, respectively as:

1

186.25 132.50

Y   X (1)

2 2

137.93 97.90 37.23

Y   X  X (2)

As can be seen, static puncture resistance linear increased with number of

layers, but dynamic puncture resistance had a parabolic relation. This reflects

that inter-laminar interaction takes more significant effect on dynamic puncture

resistance when G-CF had five layers and included 20 wt% Kevlar fibers.

Thickness increased with increment of number of layers, leading to longer distance to penetrate through compound fabrics and more chance to contact with compound fabrics. In dynamic puncture process, inter-laminar slippage occurred apparently and thus puncture spike underwent longer distance as compared to static probe at same thickness of compound fabric. Under the circumstances, dynamic puncture resistance presented parabolic relationship with number of layers. If inter-laminar sliding was not significant between layers of compound fabrics, there was linear relation between dynamic puncture resistance and number of layers, which is similar to relationship between puncture depth and number of layers as indicated in reference [35].

Besides static (Y

’) and dynamic (Y

’) puncture resistances of K-CF related to number of layers also exhibited in Figs.5-6, and their relations are respectively shown in the following:

1

' 73.90 192.59

Y   X (3)

2 2

' 315.024 92.95 72.04

Y   X  X (4)

Comparing with Eq. (1) and (3), it is found that K-CF had bigger linear slope than G-CF, indicating that number of layers more significantly influenced on static puncture resistance. But by contrast of Eq. (2) and (4), dynamic puncture resistance of K-CF changed faster than that of G-CF with number of layers. As a consequence, G-CF displayed higher dynamic puncture resistance while number of layers increased from one to four, and K-CF became bigger instead after exceeding five layers.

It is also discovered from Figs. 5 and 6 that K-CF with fiver layers and 20

wt% recycled Kevlar fibers had higher static and dynamic puncture resistances

than G-CF. However, it is not similar to that when compound fabrics ranged

from one to four layers. This is because cut resistance of Kevlar fibers largely

contributed to improvement of static puncture resistance, leading to bigger

probe tip and thus higher static puncture resistance for K-CF. But cut resistance

of Kevlar fibers and density of compound fabric compromised with each other thus resulting in nearly equivalent dynamic puncture resistance for G-CF and K-CF with one to four layers. The difference between static and dynamic puncture resistance was due to diverse puncture mechanism. Pushing force and friction strength of compound fabric to probe was to resist against static puncture property, but fiber breakage and fiber slippage could be devoted to dynamic puncture behavior, and dominated factor depends on fiber compactness.

1 2 3 4 5

0 200 400 600 800

1000 0 wt% Kevlar fiber 10 wt% Kevlar fiber 15 wt% Kevlar fiber 20 wt% Kevlar fiber

Number of G-CF Layers

S ta ti c P u n ct u re R es is ta n ce ( N /( g/ cm 3) )

1 2 3 4 5

0 200 400 600 800 1000 1200 1400 1600

1800

0 wt% Kevlar fiber 10 wt% Kevlar fiber 15 wt% Kevlar fiber 20 wt% Kevlar fiber

Number of G-CF Layers

D yn am ic P u n ct u re R es is ta n ce ( N /( g/ cm 3) )

Fig. 4. Static (a) and dynamic (b) puncture resistances of multiple-layer (from one to five layers) of G-CF with different fractions of recycled Kevlar fibers.

Fig. 5. Static puncture resistances of G-CF and K-CF as related to the number of layers. Each compound fabric was composed of 20 wt% Kevlar fibers.

Fig. 6. Dynamic puncture resistances of G-CF and K-CF as related to the

number of layers. Each compound fabric was composed of 20 wt% Kevlar fibers .

3.3. Effect of inter-laminar bonding

In order to confirm inter-laminar slippage effect, static and dynamic puncture resistances of fiver-layer compound fabrics composed of one-layer G- CF and four-layer K-CF are presented in Figs. 7-8. Separated compound fabrics had higher static and dynamic puncture resistance than the integrated (control group), indicating that inter-laminar bonding effect is positive to static and dynamic puncture resistances. Comparatively speaking, the difference of dynamic puncture resistance between compound fabric and control group displayed bigger than that of static puncture resistance. This shows that inter- laminar shear effect affected dynamic puncture property more obviously, which corresponds with tendency in Fig.6. When subjected to dynamic puncture impact, inter-laminar shear effect easily occurred and interlayer sliding distance simultaneously become longer due to higher impact energy than static puncture impact. The damage area was elongated consequently and became larger after dynamic puncture. And more fractured fibers were to resist against dynamic puncture energy as reference in [27]. This has verified by the fact that the irregular and longer dynamic damage region as well as regular and quadrilateral static damage area have found in Fig. 9.

Compared to different positions of K-CF, 3G/1K/1G compound fabric had

highest static puncture resistance, and 1K/4G owned the optimized dynamic

puncture resistance. It is thus clear that K-CF placed at lower location had

better static puncture resistance property, but that at upper place showed better

dynamic puncture resistance. This reflects that cut resistance of Kevlar fabric

influenced on dynamic puncture resistance more significantly than static

puncture resistance property.

1K/4G 1G/1K/3G 2G/1K/2G 3G/1K/1G 4G/1K 5G 5K 0

200 400 600 800 1000

1200 5-layer compound fabric 5-layer control group

Compound Fabric Composition

S ta ti c P u n ct u re R es is ta n ce ( N /( g/ cm 3) )

Fig. 7. Static puncture resistances of 5-layer compound fabric and control group with different positions of K-CF. Each compound fabric was composed of 20 wt% Kevlar fibers.

1K/4G 1G/1K/3G 2G/1K/2G 3G/1K/1G 4G/1K 5G 5K

0 400 800 1200 1600

2000 5-layer compound fabric 5-layer control group

Compound Fabric Composition

D yn am ic P u n ct u re R es is ta n ce ( N /( g/ cm 3) )

Fig. 8. Dynamic puncture resistances of 5-layer compound fabric and control group with different positions of K-CF. Each G-CF and K-CF was comprised of 20 wt% Kevlar fibers.

3.4. Puncture damage observations

Figs. 9a and b display SEM observations of thickness-direction G-CF and K-CF after static puncture damage. Fiber pushing aside has both found in SEM observations of G-CF and K-CF, and such that contact pressure and friction strength of probe to fiber assembles became main mechanism for static puncture resistance. For dynamic puncture, glass fiber breakage had discovered in the center of Fig.9c. However, there is an opening but not fiber breakage in Fig.9d. This is due to the fact that Kevlar fiber in fabric had higher tenacity and elongation than Glass fiber, and the former fabric possessed lower yarn density.

Therefore, when K-CF suffered dynamic puncture, probe easily penetrated through fiber interstices or yarn gap, separating apart Kevlar fibers alone. But glass fabric instead had higher fiber density and lower fiber strength, leading to glass fiber breakage. It is visible that fiber strength of fabric interlayer and compactness of compound fabrics determined the mechanism for dynamic puncture resistance.

Fig. 9. Static puncture observations of thickness-direction G-CF (a) and K-CF (b), and dynamic puncture observations of in-plane G-CF (c) and K-CF (d)

(c) Fiber breakage (d)

(a) (b)

4. Conclusions

This study successfully prepared an economical and flexible compound fabric for resisting against static and dynamic puncture attacks. The effect of recycled Kevlar fibers affected static and dynamic puncture resistances. The influencing tendency depended on fabric type. With constant recycled Kevlar fibers, number of layers had linear relation to static puncture resistance but polynomial correlation with dynamic puncture resistance. The final result revealed that inter-laminar shear influenced on relationship between puncture resistance and number of layers, and it affected on dynamic puncture resistance more significantly than on static puncture resistance.

Cut resistance of Kevlar fibers and compactness of fiber assembles improved both of static and dynamic puncture resistances. Comparatively, cut resistance property of fibers related to dynamic puncture behavior more significantly, but fiber compactness affected static puncture resistance obviously. The contacting pressure and friction strength of compound fabric to probe was to resist against static puncture resistance, but mechanism for dynamic puncture resistance was due to fiber elongation of fabric interlayer and compactness of compound fabric. As a result, different dynamic puncture mechanism was shown as: yarn brittle-breakage (glass compound fabric) or fiber apart (Kevlar compound fabric) besides of contact pressure between compound fabrics and puncture probe. This study only shows experimental investigations of static and dynamic puncture resistance. In the following, we will deeply discuss on the role of cut resistance and volume density on puncture resistance property of compound fabrics.

References

1. Fang XL, Zhang YP. Effect of resin on bullet-proof and stab-resistant properties

of Kevlar UD cloth. Hi-Tech Fiber Appl 2009; 34: 21-3. (in Chinese)

2. Prevorsek DC, Kwon YD, Harpell GA, Li HL. Spectra composite armour:

dynamics of absorbing the kinetic energy of ballistic projectiles. 34th International SAMPE Symposium 1989:1780-91.

3. Goldsmith W, Dharan CKH, Chang H. Quasi-static and ballistic perforation of carbon

fibre laminates. Int J Solids Struct 1995; 32(1): 89-103.

4. Almohandes A A, Abdel-Kader M S, Eleiche A M. Experimental investigation of the ballistic resistance of steel-fiberglass reinforced polyester laminated plates.

Compos Part B-Eng 1996; 27(5): 447-458.

5. Mouritz A P. Ballistic impact and explosive blast resistance of stitched composites. Compos Part B-Eng 2001; 32(5): 431-439.

6. Lee YS, Wetzel ED, Wagner NJ. The ballistic impact characteristics of Kevlar woven fabrics impregnated with a colloidal shear thickening fluid. J Mater Sci 2003; 38: 2825-33.

7. Chocron S, Pintor A, Gálvez F, Roselló C, Cendón D, Sánchez-Gálvez V.

Lightweight polyethylene non-woven felts for ballistic impact applications:

Material characterization. Compos Part B-Eng 2008; 39(7): 1240-46.

8. Yungwirth CJ, Radford DD, Aronson M, Wadley HN. Experiment assessment of the ballistic response of composite pyramidal lattice truss structures. Compos Part B-Eng 2008; 39(3): 556-569.

9. Walter TR, Subhash G, Sankar BV, Yen CF. Damage modes in 3D glass fiber epoxy woven composites under high rate of impact loading. Compos Part B-Eng 2009; 40(6): 584-89.

10. Muhi RJ, Najim F, De Moura M. The effect of hybridization on the GFRP behavior under high velocity impact. Compos Part B-Eng 2009; 40(8): 798-803.

11. Morye SS, Hine PJ, Duckett RA, Carr DJ, Ward IM. Modeling of the energy absorption by polymer composites upon ballistic impact. Compos Sci Technol 2000; 60: 2631-42.

12. Gu B. Analytical modeling for the ballistic perforation of planar plain-woven

fabric target by projectile. Compos Part B-Eng 2003; 34(4): 361-71

13. Rao MP, Duan Y, Keefe M, Powers BM, Bogetti TA. Modeling the effects of yarn material properties and friction on the ballistic impact of a plain-weave fabric. Compos Struct 2009; 89: 556-66.

14. Krishnan K, Sockalingam S, Bansal S, Rajan SD. Numerical simulation of ceramic composite armor subjected to ballistic impact. Compos Part B-Eng 2010;

41(8): 583-93.

15. Feli S, Namdari Pour MH. An analytical model for composite sandwich panels with honeycomb core subjected to high-velocity impact. Compos Part B-Eng 2012; 43(5): 2439-47.

16. Yashiro S, Ogi K, Oshita M. High-velocity impact damage behavior of plain- woven SiC/SiC composites after thermal loading. Compos Part B-Eng 2012;

43(3): 1353-62.

17. Chen X, Zhu F, Wells G. An analytical model for ballistic impact on textile based body armour. Compos Part B-Eng 2013; 45(1): 1508-14.

18. Gu B, Xu J. Finite element calculation of 4-step 3-dimensional braided composite under ballistic perforation. Compos Part B-Eng 2004; 35(4): 291-7.

19. Abu Al-Rub RK, Kim SM. Predicting mesh-independent ballistic limits for heterogeneous targets by a nonlocal damage computational framework. Compos Part B-Eng 2009; 40(6): 495-510.

20. Sun B, Liu Y, Gu B. A unit cell approach of finite element calculation of ballistic impact damage of 3-D orthogonal woven composite. Compos Part B-Eng 2009;

40(6): 552-60.

21. Grujicic M, Arakere G, He T, Bell WC, Glomski PS, Cheeseman BA. Multi- scale ballistic material modeling of cross-plied compliant composites. Compos Part B-Eng 2009; 40(6): 468-82.

22. Jin L, Hu H, Sun B, Gu B. A simplified microstructure model of bi-axial warp- knitted composite for ballistic impact simulation. Compos Part B-Eng 2010;

41(5): 337-53

23. Fei S, Asgari MR. Finite element simulation of ceramic/composite armor under

ballistic impact. Compos Part B-Eng 2011; 42(4): 771-80.

24. Henderson JP, Morgan SE, Patel F, Tiplady ME. Patterns of non-firearm homicide. J Clin Forensic Med 2005; 12: 128-32.

25. Kim H, Nam I. Stab resisting behavior of polymeric resin reinforced p-aramid fabrics. J Appl Polym Sci 2012; 123: 2733-42.

26. National Law Enforcement and Corrections Technology Ctr (NLECTC). Taking the stab out of stabbings. Tech Beat; Spring: 2000.

27. Mayo Jr JB, Wetzel ED, Hosur MV, Jeelani S. Stab and puncture characterization of thermoplastic-impregnated aramid fabrics. Int J Impact Eng 2009; 36: 1095-105.

28. Decker MJ, Halbach CJ, Nam CH, Wagner NJ, Wetzel ED. Stab resistance of shear thickening fluid (STF)-treated fabrics. Compos Sci Technol 2007; 67(3–4):

565-78.

29. Kang TJ, Kim CY, Hong KH. Rheological behavior of concentrated silica suspension and its application to soft armor. J Appl Polym Sci 2012; 124: 1534- 41.

30. Li TT, Wang R, Lou CW, Lin JH. Evaluation of high-modulus, puncture -resistance composite nonwoven fabrics by response surface methodology. J Ind Text 2012. http://jit.sagepub.com/content/early/2012/07/04/1528083712452900 . 31. Li TT, Wang R, Lou CW, Huang CH, Lin JH. Mechanical and physical

properties of puncture-resistance plank made of recycled selvages. Fibers Polm 2013; 14(2): 258-65.

32. Tien DT, Kim JS, Huh Y. Stab-resistant property of the fabrics woven with the aramid/cotton core-spun yarns. Fibers Polym 2010; 11(3): 500-6.

33. Termonia Y. Puncture resistance of fibrous structures. Int J Impact Eng 2006; 32:

1512-20.

34. Mayo Jr JB, Wetzel ED. Cut resistance and fracture toughness of high performance fibers dynamic behavior of materials. Conference Proceedings of the Society for Experimental Mechanics Series 99 2011: 167-73.

35. Tien DT, Kim JS, Huh Y. Evaluation of anti-stabbing performance of fabric

layers woven with various hybrid yarns under different fabric conditions. Fibers

Polym 2011; 12(6): 808-15.