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Abstract

The aim of this study was to understand the stick–slip (Sk-Sp) properties of para-aramid woven fabrics. For this reason, pullout test was conducted on para-aramid Twaron CT^® 716 (CT716) and Twaron CT^® 716 (CT714) woven fabrics. The Sk-Sp region and accumulative retraction force region were defined based on the single- or multiple-yarn pullout force–displacement curve. It was found that Sk-Sp force and accumulative retraction force depend on the fabric density and the number of pulled ends in the fabric. Sk-Sp force in the multiple-yarn pullout test was higher than that of the single-yarn pullout test. Sk-Sp force in single- and multiple-yarn pullout tests in the dense CT716 fabric was higher than that of the loose CT714 fabric. In addition, long fabric samples showed high Sk-Sp force compared to that of the short fabric samples. On the other hand, the amount of Sk-Sp force was related to the number of interlacement points in the fabric, whereas the amount of accumulative retraction force was related to fabric structural response.

Keywords

Ballistic fabrics single- and multiple-yarn pullouts stick–slip force accumulative retraction force pullout fixture

Introduction

Ballistic fabrics with higher pullout force have been shown to perform favorably in impact loading.¹ Yarn pullout was defined by Kirkwood et al. as one end of the yarn being pulled out from the fabric structure by the motion of the penetrator. The force required to pull the yarn from the fabric structure was the sum of the frictional forces between the yarn sets at all intersecting points.^1
–3 The three distinct modes of fabric failure observed by Erlich et al. in slow penetration tests were yarn pullout, local yarn rupture and remote yarn failure.⁴ Ballistic performance depends upon friction, material properties, such as elastic modulus and strength of the yarn, fabric structure, multiple plies and far field boundary conditions.^5
–7 Another study revealed that very high interyarn friction could lead to premature yarn rupture during impact load and reduce the energy absorbing ability of the fabric. In addition, the crimp in the woven fabric could be considered as another factor.^8,9 On the other hand, the tribological behavior of woven fabric made from yarns of different linear densities was compared with the friction properties of their constituent yarns using different surface treatments. Both yarn texture and surface treatment were seen to have an influence on the friction coefficient. In addition, linear density and woven structure had the largest impact on friction.¹⁰ The softening treatment of fabric was shown to reduce interyarn adhesion and interyarn sliding friction.^11,12 Frictional processes within a fabric are important for both normal indentation and ballistic deformations because they control the effective stiffness of the material. It was found that fabrics with high friction and the lowest effective moduli dissipated larger amounts of energy relative to fabrics with lower friction. Relatively small changes in friction produced much greater changes in the deformational behavior of an assembly of crossover contacts.¹³ Recently, Gawandi et al. studied on the pullout properties on the polymer (ethylene/methy/acrylate copolymer)-coated plain woven Kevlar (KM2) fabric. It was demonstrated that the polymer-coated fabric showed higher pullout energy and loading rate dependence compared to the uncoated fabric.¹⁴

Modeling studies have shown that friction contributed to delaying fabric failure and increasing impact load thus allowing the fabric to absorb more energy. Also, it was reported that fabric boundary condition was a factor that influenced friction.¹⁵ Projectile–fabric friction delayed yarn breakage by distributing the maximum stress along the periphery of the projectile–fabric contact zone. The delay in yarn breakage substantially increased the fabric’s energy absorption during the later stages of impact. Yarn-to-yarn friction hindered the relative motion between yarns and thus resisted decrimping of fabric weave tightness. It induced the fabric to fail earlier during the impact process.¹⁶ The effect of yarn slippage at the crossover point as well as within the clamp was modeled and yarn fracture during impact in single ply woven fabric was determined using a kinetic energy relation.¹⁷

The fabric maximum pullout forces in para-aramid fabric structures have been investigated with regard to their ballistic performance. It was found that stitched ballistic-layered structures showed high pullout force that enhanced the ballistic resistance of the structures.¹⁸ The fabric displacement stage and crimp extension stage in single- and multiple-yarn ends pullout have been investigated. It was concluded that the fabric displacement stage could be utilized to determine fabric shear behavior^19,20 and the crimp extension stage could be used to explain the fabric failure under tensile loads.²¹ The stick–slip (Sk-Sp) phenomenon has been identified in nature and has been used to explain the seismic movement, the flow of glaciers²² and textile materials,²³ and even everyday life. The Sk-Sp phenomenon was considered during single- and multiple-yarn ends pullout in fabric.²¹ As seen in the literature, the friction in the Sk-Sp stage of pullout in fabric structure was an important energy absorption mechanism for soft ballistic. Therefore, the aim of this study was to understand the behavior of the Sk-Sp stage of para-aramid single woven fabric under single- and multiple-yarn pullouts.

Materials and methods

Para-aramid fiber and woven fabrics

The woven fabric was constructed with para-aramid type of fibers (Teijin Aramid BV Arnhem/Netherland is a subsidiary of the Teijin group/Japan). The fiber and fabric properties are presented in Table 1. Two types of fabrics were used. These were Twaron CT^® 716 (CT716) and Twaron CT^® 714 (CT714). They were both plain weave and the warp and filling yarn linear densities were 110 tex. The warp and filling densities of the CT716 and CT714 fabrics were 12.2 ends/cm and 8.5 ends/cm, respectively. The weights of the fabric unit areas were 280 g/m² and 190 g/m², respectively. Water repellent treatment was also applied to both fabrics. Crimp measurement was performed using a Tautex Digital Instrument (James H. Heal Co., Halifax/England) according to ISO 7211-3. Fabric thickness measurement was performed using a R&B cloth thickness tester (James H. Heal Co.) according to ISO 5084. Fabric weight measurement was performed based on ISO 6348. The fabric’s initial angle between warp and weft was measured using an optical microscope (Olympus SZ61-TR, Tokyo/Japan).

Table 1.

Properties of high modulus para-aramid Twaron CT^® fibers²⁴ and fabrics.

Fiber type		Fiber diameter (μm)		Fiber density (g/cm³)		Tensile strength (GPa)	Tensile modulus (GPa)		Elongation at break (%)	Decomposition point (°C)
Twaron CT^®, Teijin		12		1.45		3.2	115		2.9	550
Fabric type	Weave type	Yarn linear density (tex)		Density (per cm)		Weight (g/m²)	Crimp (%)		Thickness (mm)	Treatment
Fabric type	Weave type	Warp	Filling	Warp	Filling	Weight (g/m²)	Warp	Filling	Thickness (mm)	Treatment
Twaron CT^® 714	Plain	110	110	8.5	8.5	190	1.38	1.98	0.30	Water repellent (wrt)
Twaron CT^® 716	Plain	110	110	12.2	12.2	280	6.36	1.96	0.40	Water repellent (wrt)

Pullout tests

Pullout tests were conducted to determine the yarn-to-yarn friction on single- or multiple-yarn ends in the frayed edge of the plain fabric structure. For this reason, a pullout fixture was developed. Figure 1 shows the fixture and the pullout test carried out in the testing instrument. Fabric from both edges was clamped under no pretension. To test this initial condition, tension meter (maximum load 1000 cN, SDL Atlas International Ltd., Cheshire/UK) was used to measure the initial tension on the ravel yarn. If there is any residual pretension on the ravel yarn, then the fabric was loosely clamped. In this setup, the fabric Sk-Sp stage was defined as “the end of one yarn set (either warp or weft) passes through from each of the consecutive intersecting points in the fabric during single- or multiple-yarn pullout after the maximum pullout force stage completed.” Figure 2 shows the schematic views of the fixture and pullout test during the Sk-Sp stage. In addition, “when the pulled yarn end in the fabric is released from each transverse yarn (normal to the pulled yarn direction), in here, the response of the remaining part of the pulled yarn in the fabric is defined as the accumulative retraction force.” Fabric crimp interchange during the pullout test was ignored. The residual tension on the fabric due to clamped fabric edges was also ignored. The yarn slippages and yarn flattening in warp and weft directions in the fabric interlacement regions were not considered for simplification purposes. The testing instrument used was the Instron 4411 and the testing speed was 100 mm/min.

Figure 1.

Pullout fixture with fabric on the tensile testing instruments.

Figure 2.

Schematic views of the fabric and yarn positions measured during pullout test. (a) Fabric position before pullout test and (b) Stick–slip stage of fabric position during pullout test.

Fabric dimensions for performing the pullout test were prepared as a fabric width of 360 mm for the total sample dimension and 300 mm for the sample dimension in the fixture. Fabric lengths ranged from 100 mm to 300 mm. The pullout direction was in the weft direction of the fabrics. The frayed yarn length of the sample was 150 mm and the total edge length holding the sample in the fixture edge was 60 mm. In the single-yarn pullout test, only one yarn was pulled from the middle of the fabric sample. In the multiple-yarn pullout test, 2, 3, 4 and 5 yarns were pulled from the middle of the each fabric sample. The Instron 4411 pull head drew individual yarn ends from the frayed edge of the single fabric. The force–displacement curve data obtained from single and multiple pullouts were analyzed by MATLAB-based algorithm,²⁵ and using this algorithm, the Sk-Sp forces and accumulative retraction forces were calculated. Yarn pullout test data were loaded for each sample in matrix form, which consists of the measured force and extension values. The built-in functions of MATLAB were used for detecting the local maxima (the local peaks) and corresponded locations of the peaks in the given data sequence. Loaded data were analyzed for local maxima and the corresponded extension values which were deduced from the location of the peak values in the data matrix. Local minimum load values were detected in the same way. But this time, the negative values of the data sequence were used so that the local minimum values were reversed and become local maximum values for temporarily detecting purpose. After detecting the local maximum and minimum load values of the measured samples, they were stored as vector forms of data for further analysis. Sk-Sp values were calculated by subtracting the first minimum from the first maximum and second minimum from the second maximum and so on. Accumulative retraction values were calculated by subtracting the first minimum from the second maximum and second minimum from the third maximum and so on. In addition, the Sk-Sp energy and accumulative retraction energy were calculated using the area in the yarn pullout force–displacement curve as seen schematically in Figure 3.

Figure 3.

Stick–slip stage of single-yarn pullout force–displacement curves of K29 fabric. (a) The number of the mesocells in the beginning of stick–slip stage at the bottom of the fabric edge, (b) the number of mesocells in the middle of the stick–slip stage at the center of the fabric and (c) the end of the stick–slip stage at the top of the fabric edge (fabric width: 300 mm and fabric length: 300 mm).

Results and discussion

Sk-Sp stage in the yarn pullout

Single- and multiple-yarn pullout tests on CT716 (dense fabric) and CT714 (loose fabric) samples were carried out. Single- and multiple-yarn pullout force–displacement curves were obtained. In the yarn pullout force–displacement curve, the Sk-Sp stages of the kinetic friction part, which was from the beginning of the maximum pullout force to the end of the yarn pullout test, were considered. The curve in the kinetic region has one maxima and one minima for each two crossing points where from maximum to minimum (one minima) is called stick–slip and from minimum to maximum (one maxima) is called accumulative retraction force due to fabric structure. Figure 3 shows the Sk-Sp stages of the single-yarn pullout force–displacement curve in which the six mesocells (MC-1, MC-2, MC-3, MC-4, MC-5 and MC-6) of para-aramid fabric in the bottom of the fabric edge (a) at the center of the fabric (b) were considered to investigate the Sk-Sp stage of the single- and multiple-yarn pullout force–displacements.

One mesocell (MC) is composed of one stick region and one slip region as shown in Figure 4. In the stick region, there is pressure between the warp and weft yarns either in the front face or in the back face of the fabric during the pulling of the warp yarn as shown schematically in Figure 5. In the slip region, there is pressure between the warp and weft yarns where the warp is crossed during the pulling of the warp yarn as shown in Figure 5. The amount of pressure is proportional, as given in the following relationships

F_{1} = cos θ \cdot F

F_{2} = sin θ \cdot F

Figure 4.

The schematic views of slip–stick stage in the mesocells of para-aramid fabric structures, (a) before pullout force is applied and (b) after pullout force is applied.

Figure 5.

The schematical views of pullout force components in stick–slip stage of the para-aramid fabric.

where F is the pullout force, θ is the initial crossing angle, F ₁ is the in-plane direction pullout force component and F ₂ is the out-of-plane direction pullout force component.

The initial crossing angle (θ) depends on directional fabric density and directional crimp ratio. Under the pullout force on warp yarn, fabric displacement and crimp extension stages occurred first.¹⁹ This causes straightening of the pulled warp yarn and θ is decreased from its initial value. The measured average initial θ values for CT716 and CT714 fabrics were 10.37° and 4.41°, respectively. If we use equations (1) and (2), we get F ₁ = 0.984 × F and F ₂ = 0.175 × F for CT716, and F ₁ = 0.996 × F and F ₂ = 0.087 × F for CT714. As seen in the relations, the out-of-plane direction pullout force, F ₂ is very small and the in-plane direction pullout force and F ₁ is very high for both fabric structures. In the stick regions, the in-plane direction pullout force component (F ₁) is most similar to main force to generate pressure on the yarn in the fabric structure. In slip regions, out-of-plane direction pullout force component (F ₂) is most similar to main force to generate pressure on the crossing part of the yarn in the fabric structure as shown in Figures 4 and 5. However, more research is required to define the yarn pressure in the slip region of the fabric during pullout.

When we look at the MCs in the Sk-Sp stages of the single-yarn pullout force–displacement curve in Figure 3, there is an exponential function which has periodic decrease and increase lines. It is most likely that the decreasing line corresponds to each Sk-Sp region, whereas the increasing line corresponds to each accumulative retraction force by fabric structure (Af) as shown in Figure 6. After the maximum pullout force stage was completed, the first decreasing line occurred due to the first yarn Sk-Sp region. When the first yarn (warp) was released from the fabric structure, the first increasing line occurred due to accumulative retraction force by fabric structure coming from the remaining five yarns in the end of the pulled yarn (weft) as shown in Figures 5 and 6. When the pullout phenomena was repeated, the second decreasing line occurred due to the second yarn Sk-Sp region. Immediately afterward, the second yarn was released from the fabric structure and the second increasing line occurred due to accumulative retraction force by the fabric structure coming from the remaining four yarns in the end of the pulled yarn. This phenomenon was repeated until the sixth yarn was released from the pulled yarn.

Figure 6.

The schematic views of stick–slip stage in the representative pullout force–displacement curve of para-aramid fabric during pullout.

Sk-Sp force in single-yarn pullout

The Sk-Sp force and accumulative retraction force obtained from the single-yarn pullout force–displacement curve of CT716 and CT714 fabrics for six MCs are presented in Tables 2 and 3, respectively. Tables 2 and 3 also present calculated normalized Sk-Sp and accumulative retraction forces in single-yarn pullout forces. Figure 7(a) and (b) shows the relationship between the Sk-Sp force and the number of MCs in the single-yarn pullout test of CT716 and CT714 fabrics, respectively. As seen in Figure 7(a) and (b) and Tables 2 and 3, the weft directional single-yarn Sk-Sp force in the MC-1 to the MC-6 of CT716 and CT714 fabrics in fabric edges decreased for short and long fabric lengths, whereas no significant differences were obtained in the MC-1 to the MC-6 of CT716 and CT714 fabrics in fabric centers. The single-yarn Sk-Sp force in the MC-1 to MC-6 of CT716 fabric in fabric edge slightly increased when the fabric length increased due to the increasing number of crossing points. But no significant differences were obtained for those in the CT714 fabric. The single-yarn Sk-Sp forces in the MC-1 of CT716 and CT714 fabrics in the fabric edge were higher than those in the MC-6 of CT716 and CT714 fabrics due to the remaining crossing points in the fabric during pullout. In addition, the single-yarn Sk-Sp forces in the MC-1 to MC-6 of CT716 and CT714 fabrics in the fabric edge were higher than those in the fabric center. On the other hand, the single-yarn Sk-Sp forces in CT716 fabric were higher than those in CT714 fabric due to fabric density. Fabric length considerably affected the Sk-Sp forces of dense CT716 fabric and loose CT714 fabric due to the increasing number of crossing points. The position of the MCs also affected the Sk-Sp forces of CT716 and CT714 fabrics.

Table 2.

Sk-Sp force and accumulative retraction force obtained from the single- and multiple-yarn pullout force–displacement curves of CT716 fabric for six MCs in the fabric edge and center regions.

Fabric length (mm)	Ends of yarn	Fabric edge
		MC-1				MC-2				MC-3				MC-4				MC-5				MC-6
		Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia
100	1 yarn	4.03	0.04	1.34	0.01	2.28	0.02	1.61	0.02	2.15	0.02	1.61	0.02	2.01	0.02	1.74	0.02	2.01	0.02	1.61	0.02	2.01	0.02	1.61	0.02
	2 yarns	7.92	0.08	2.28	0.02	5.10	0.05	2.42	0.02	4.04	0.04	2.16	0.02	3.50	0.04	1.75	0.02	3.09	0.03	1.21	0.01	3.36	0.03	2.28	0.02
	3 yarns	9.26	0.09	0.27	0.00	8.86	0.09	2.68	0.03	6.17	0.06	1.34	0.01	6.58	0.07	2.82	0.03	6.85	0.07	3.35	0.03	6.84	0.07	3.75	0.04
	4 yarns	91.30	0.91	0.40	0.00	16.64	0.17	0.26	0.00	6.72	0.07	0.94	0.01	7.38	0.07	0.13	0.00	8.05	0.08	2.42	0.02	13.44	0.13	2.02	0.02
	5 yarns	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
300	1 yarn	4.97	0.02	2.42	0.01	3.49	0.01	2.55	0.01	3.36	0.01	2.96	0.01	3.22	0.01	2.95	0.01	3.22	0.01	2.82	0.01	3.36	0.01	2.95	0.01
	2 yarns	10.34	0.03	1.21	0.00	6.72	0.02	2.01	0.01	5.77	0.02	2.28	0.01	5.50	0.02	2.68	0.01	5.37	0.02	3.22	0.01	5.50	0.02	2.69	0.01
	3 yarns	32.89	0.11	0.13	0.00	10.74	0.04	0.53	0.00	9.66	0.03	0.94	0.00	8.59	0.03	1.61	0.01	7.39	0.02	1.21	0.00	6.85	0.02	1.75	0.01
	4 yarns	481.80	1.61	0.40	0.00	9.80	0.03	0.26	0.00	12.21	0.04	0.54	0.00	2.15	0.01	0.54	0.00	7.12	0.02	0.27	0.00	2.01	0.01	0.40	0.00
	5 yarns	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–

Fabric length (mm)	Ends of yarn	Fabric center
		MC-1				MC-2				MC-3				MC-4				MC-5				MC-6
		Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia
100	1 yarn	1.47	0.01	1.88	0.02	1.75	0.02	1.75	0.02	2.29	0.02	1.88	0.02	1.74	0.02	1.07	0.01	0.94	0.01	1.08	0.01	1.61	0.02	1.07	0.01
	2 yarns	4.02	0.04	3.35	0.03	4.03	0.04	3.36	0.03	3.89	0.04	3.35	0.03	3.89	0.04	3.49	0.03	4.16	0.04	2.82	0.03	3.49	0.03	3.09	0.03
	3 yarns	3.35	0.03	3.09	0.03	4.30	0.04	2.42	0.02	4.30	0.04	3.22	0.03	4.29	0.04	3.08	0.03	4.70	0.05	3.36	0.03	5.11	0.05	4.44	0.04
	4 yarns	5.11	0.05	2.29	0.02	5.64	0.06	1.20	0.01	6.30	0.06	3.75	0.04	6.71	0.07	3.63	0.04	5.91	0.06	1.88	0.02	5.91	0.06	2.82	0.03
	5 yarns	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
300	1 yarn	1.87	0.01	2.14	0.01	3.08	0.01	2.55	0.01	1.61	0.01	1.74	0.01	2.68	0.01	2.14	0.01	1.07	0.00	1.21	0.00	2.28	0.01	2.41	0.01
	2 yarns	6.31	0.02	5.77	0.02	6.59	0.02	5.65	0.02	5.92	0.02	4.98	0.02	4.84	0.02	3.50	0.01	3.37	0.01	1.89	0.01	1.75	0.01	0.13	0.00
	3 yarns	6.86	0.02	1.35	0.00	4.57	0.02	3.49	0.01	3.76	0.01	2.42	0.01	5.50	0.02	2.95	0.01	3.76	0.01	0.54	0.00	3.49	0.01	0.94	0.00
	4 yarns	3.76	0.01	0.67	0.00	2.01	0.01	0.94	0.00	2.02	0.01	0.68	0.00	3.49	0.01	0.13	0.00	1.61	0.01	0.80	0.00	2.01	0.01	0.81	0.00
	5 yarns	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–

MC: mesocell; Sk-Sp: stick–slip; Af: accumulative retraction force due to fabric structure; Is: normalized Sk-Sp force (N/mm); Ia: normalized accumulative retraction force (N/mm).

Table 3.

Sk-Sp force and accumulative retraction force obtained from the single- and multiple-yarn pullout force–displacement curves of CT714 fabric for six MCs in the fabric edge and center regions.

Fabric length (mm)	Ends of yarn	Fabric edge
		MC-1				MC-2				MC-3				MC-4				MC-5				MC-6
		Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia
100	1 yarn	2.01	0.02	1.48	0.01	1.48	0.01	1.34	0.01	1.74	0.02	1.48	0.01	1.75	0.02	1.21	0.01	1.61	0.02	1.34	0.01	1.61	0.02	0.94	0.01
	2 yarns	5.37	0.05	3.23	0.03	4.31	0.04	2.95	0.03	4.16	0.04	3.09	0.03	4.03	0.04	2.69	0.03	2.82	0.03	1.74	0.02	3.49	0.03	2.42	0.02
	3 yarns	12.75	0.13	6.97	0.07	8.32	0.08	4.16	0.04	7.65	0.08	4.84	0.05	6.59	0.07	4.3	0.04	5.78	0.06	4.17	0.04	5.24	0.05	3.90	0.04
	4 yarns	20.15	0.20	8.07	0.08	11.29	0.11	6.44	0.06	9.66	0.10	5.1	0.05	8.05	0.08	4.02	0.04	9.66	0.10	6.58	0.07	7.12	0.07	4.16	0.04
	5 yarns	25.11	0.25	2.01	0.02	17.04	0.17	6.71	0.07	13.96	0.14	10.2	0.10	15.04	0.15	5.64	0.06	8.6	0.09	5.25	0.05	10.21	0.10	5.1	0.05
300	1 yarn	3.22	0.01	0.94	0.00	2.01	0.01	1.07	0.00	1.75	0.01	1.08	0.00	1.49	0.00	1.09	0.00	1.62	0.01	1.07	0.00	1.34	0.00	0.94	0.00
	2 yarns	8.19	0.03	1.47	0.00	5.24	0.02	1.75	0.01	4.30	0.01	2.15	0.01	4.16	0.01	2.41	0.01	4.02	0.01	2.41	0.01	3.89	0.01	2.55	0.01
	3 yarns	20.41	0.07	0.94	0.00	12.08	0.04	2.95	0.01	9.26	0.03	3.63	0.01	8.33	0.03	3.36	0.01	7.8	0.03	3.64	0.01	6.99	0.02	4.03	0.01
	4 yarns	76.27	0.25	0.26	0.00	20.27	0.07	4.17	0.01	16.79	0.06	6.04	0.02	15.57	0.05	5.9	0.02	14.37	0.05	6.32	0.02	13.03	0.04	6.44	0.02
	5 yarns	244.91	0.82	3.76	0.01	15.58	0.05	2.41	0.01	14.22	0.05	4.02	0.01	16.12	0.05	4.43	0.01	16.24	0.05	4.97	0.02	16.12	0.05	5.38	0.02

Fabric length (mm)	Ends of yarn	Fabric center
		MC-1				MC-2				MC-3				MC-4				MC-5				MC-6
		Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia	Sk-Sp (N)	Is	Af (N)	Ia
100	1 yarn	0.94	0.01	0.67	0.01	0.94	0.01	0.81	0.01	0.81	0.01	0.81	0.01	0.94	0.01	0.81	0.01	0.68	0.01	0.54	0.01	0.54	0.01	0.54	0.01
	2 yarns	1.75	0.02	1.61	0.02	2.01	0.02	1.88	0.02	1.48	0.01	1.21	0.01	1.61	0.02	1.34	0.01	0.94	0.01	0.94	0.01	1.34	0.01	1.08	0.01
	3 yarns	1.88	0.02	1.47	0.01	2.55	0.03	2.28	0.02	2.01	0.02	1.61	0.02	2.41	0.02	2.14	0.02	2.01	0.02	1.74	0.02	2.14	0.02	1.88	0.02
	4 yarns	2.96	0.03	2.55	0.03	3.76	0.04	2.96	0.03	3.49	0.03	2.68	0.03	3.09	0.03	2.69	0.03	2.95	0.03	2.14	0.02	1.88	0.02	1.75	0.02
	5 yarns	6.19	0.06	4.97	0.05	4.83	0.05	4.02	0.04	5.37	0.05	4.3	0.04	4.97	0.05	3.63	0.04	3.49	0.03	2.82	0.03	2.15	0.02	1.74	0.02
300	1 yarn	0.54	0.00	0.54	0.00	0.8	0.00	0.67	0.00	0.81	0.00	0.67	0.00	0.67	0.00	0.67	0.00	0.67	0.00	0.67	0.00	0.53	0.00	0.4	0.00
	2 yarns	1.88	0.01	1.74	0.01	1.74	0.01	1.61	0.01	2.28	0.01	1.88	0.01	2.29	0.01	1.88	0.01	1.88	0.01	2.02	0.01	1.75	0.01	1.61	0.01
	3 yarns	3.09	0.01	2.69	0.01	3.63	0.01	2.82	0.01	3.62	0.01	3.08	0.01	3.35	0.01	3.35	0.01	3.08	0.01	2.95	0.01	3.22	0.01	2.55	0.01
	4 yarns	4.31	0.01	3.10	0.01	4.84	0.02	2.95	0.01	4.43	0.01	3.36	0.01	4.30	0.01	3.76	0.01	4.16	0.01	3.09	0.01	4.43	0.01	2.95	0.01
	5 yarns	4.97	0.02	1.07	0.00	4.70	0.02	2.15	0.01	5.10	0.02	3.22	0.01	5.37	0.02	2.42	0.01	4.43	0.01	2.28	0.01	5.64	0.02	2.69	0.01

MC: mesocell; Sk-Sp: stick–slip; Af: accumulative retraction force due to fabric structure; Is: normalized Sk-Sp force (N/mm); Ia: normalized accumulative retraction force (N/mm).

Figure 7.

Relationship between stick–slip force and the number of mesocells in single-yarn pullout test of para-aramid fabric in the fabric edge and center regions. (a) CT716 woven fabric and 9b) CT714 woven fabric.

Accumulative retraction force due to fabric structure in single-yarn pullout

The accumulative retraction forces obtained from the single-yarn pullout force–displacement curves of CT716 and CT714 fabrics for six MCs in the fabric edge and center are presented in Tables 2 and 3, respectively. Figure 8(a) and (b) shows the relationship between accumulative retraction force due to fabric structure and the number of MCs in the single-yarn pullout test of CT716 and CT714 fabrics, respectively. As seen in Figure 8(a) and (b) and Tables 2 and 3, the single-yarn accumulative retraction forces in CT716 fabric varied from 1.34 N to 1.74 N in MC-1 to MC-6 for short fabric and from 2.42 N to 2.95 N in MC-1 to MC-6 for long fabric in fabric edge region, whereas the single-yarn accumulative retraction forces in CT716 fabric varied from 1.07 N to 1.88 N in MC-1 to MC-6 for short fabric and from 1.21 N to 2.55 N in MC-1 to MC-6 for long fabric in fabric center region.

Figure 8.

Relationship between accumulative retraction force due to fabric structure and the number of mesocells in single-yarn pullout test of para-aramid fabric in the fabric edge and center regions. (a) CT716 woven fabric and (b) CT714 woven fabric.

The single-yarn accumulative retraction forces in CT714 fabric varied from 0.94 N to 1.48 N in MC-1 to MC-6 for short fabric and from 0.94 N to 1.09 N in MC-1 to MC-6 for long fabric in fabric edge region, whereas the single-yarn accumulative retraction forces in CT714 fabric varied from 0.54 N to 0.81 N in MC-1 to MC-6 for short fabric and from 0.40 N to 0.67 N in MC-1 to MC-6 for long fabric in fabric center region.

Although, we did not find any significant differences in the MC-1 to MC-6 of various fabric lengths of CT716 and CT714 fabrics in the fabric edge and fabric center regions, the single-yarn accumulative retraction forces in long CT716 fabric were higher than those of short CT716, whereas the single-yarn accumulative retraction forces in short CT714 fabric were slightly higher than those of long CT716. In addition, the single-yarn accumulative retraction forces in CT716 fabric were higher than those of CT714 due to fabric density.

Figure 9(a) and (b) shows the relationship between normalized Sk-Sp force (Is) and normalized accumulative retraction force (Ia), and the number of MCs in the single-yarn pullout test of CT716 and CT714 fabrics, respectively. As seen in Figure 9(a) and (b), the weft directional Is and Ia in the MC-1 to the MC-6 of CT716 and CT714 fabrics in fabric edges decreased, whereas no significant differences were obtained in the MC-1 to the MC-6 of CT716 and CT714 fabrics in fabric centers. The Is in the MC-1 to MC-6 of CT716 and CT714 fabrics in the fabric edge and center was generally high compared to those of Ia. In addition, the Is and Ia in the MC-1 to MC-6 of CT716 and CT714 fabrics in the fabric edge were higher than those in the fabric center. On the other hand, the Is and Ia in CT716 fabric were higher than those in CT714 fabric due to fabric density.

Figure 9.

Relationship between normalized stick–slip force (Is) and normalized accumulative retraction force (Ia) due to fabric structure and the number of mesocells in single-yarn pullout test of para-aramid fabric in the fabric edge and center regions. (a) CT716 woven fabric and (b) CT714 woven fabric (fabric length: 100 mm).

Figure 10(a) and (b) shows the relationship between Sk-Sp energy and accumulative retraction energy (pullout energy), and the number of MCs in the single-yarn pullout test of CT716 and CT714 fabrics, respectively. As seen in Figure 10(a) and (b), the weft directional single-yarn Sk-Sp energy and accumulative retraction energy in the MC-1 to the MC-6 of CT716 and CT714 fabrics in fabric edges decreased, whereas no significant differences were obtained in the MC-1 to the MC-6 of CT716 and CT714 fabrics in fabric centers. The single-yarn Sk-Sp energy in the MC-1 to MC-6 of CT716 fabric in fabric edge and center were slightly higher than those of accumulative retraction energy, whereas the single-yarn accumulative retraction energy in the MC-1 to MC-6 of CT714 fabric in fabric edge and center were slightly higher than those of Sk-Sp energy. The single-yarn Sk-Sp and accumulative retraction energies in the MC-1 to MC-6 of CT716 and CT714 fabrics in the fabric edge were higher than those in the fabric center. On the other hand, the single-yarn Sk-Sp energies in CT716 fabric were higher than those in CT714 fabric due to fabric density. Fabric density and the position of the MCs affected the Sk-Sp energy and accumulative retraction energy of CT716 and CT714 fabrics.

Figure 10.

Relationship between pullout energy in stick–slip and accumulative retraction force due to fabric structure and the number of mesocells in single-yarn pullout test of para-aramid fabric in the fabric edge and center regions. (a) CT716 woven fabric and (b) CT714 woven fabric (fabric length: 100 mm).

Sk-Sp force in multiple-yarn pullout

The Sk-Sp force and accumulative retraction force obtained from the multiple-yarn pullout force–displacement curves of CT716 and CT714 fabrics for six MCs in fabric edge and center are presented in Tables 2 and 3, respectively. Tables 2 and 3 also present calculated normalized Sk-Sp and accumulative retraction forces in multiple-yarn pullout forces. Figure 11(a) and (b) shows the relationship between Sk-Sp force and the number of MCs in the multiple-yarn pullout test of CT716 and CT714 fabrics, respectively. As seen in Figure 11(a) and (b) and Tables 2 and 3, the weft directional multiple-yarn Sk-Sp forces in the MC-1 to the MC-6 of CT716 and CT714 fabrics in fabric edges decreased sharply for short and long fabric lengths, whereas no significant differences were obtained in the MC-1 to the MC-6 of short and long CT716 and CT714 fabrics in fabric centers. The multiple-yarn Sk-Sp forces in the MC-1of CT716 and CT714 fabrics in fabric edge were the highest, whereas the multiple-yarn Sk-Sp forces in the MC-6 of CT716 and CT714 in fabric edge were the lowest. In addition, the multiple-yarn Sk-Sp forces in the MC-1 to MC-6 of CT716 and CT714 fabrics in the fabric edge were higher than those in the fabric center. On the other hand, the multiple-yarn Sk-Sp forces in CT716 fabric were higher than those in CT714 fabric due to fabric density. The number of the pullout ends and the position of the MCs affected the Sk-Sp forces of CT716 and CT714 fabrics. Also, the fabric length slightly affected the multiple-yarn Sk-Sp forces of the dense CT716 fabric and loose CT714 fabric except MC-1.

Figure 11.

Relationship between stick–slip force and the number of mesocells in multiple-yarn pullout test of para-aramid fabric. (a) CT716 woven fabric (pulled yarn ends: 4) and (b) CT714 woven fabric (pulled yarn ends: 5).

Accumulative retraction force due to fabric structure in multiple-yarn pullout

The accumulative retraction force obtained from the multiple-yarn pullout force–displacement curves of CT716 and CT714 fabric for six MCs in fabric edge and fabric center are presented in Tables 2 and 3, respectively. Figure 12(a) and (b) shows the relationship between accumulative retraction force due to fabric structure and the number of MCs in the multiple-yarn pullout test of CT716 and CT714 fabrics for fabric edge and fabric center. As seen in Figure 12(a) and (b) and Tables 2 and 3, the multiple-yarn (four yarns) accumulative retraction forces in CT716 fabric varied from 0.13 N to 2.42 N in MC-1 to MC-6 for short fabric and from 0.26 N to 0.54 N in MC-1 to MC-6 for long fabric in fabric edge region, whereas the multiple-yarn (four yarns) accumulative retraction forces in CT716 fabric varied from 1.20 N to 3.75 N in MC-1 to MC-6 for short fabric and from 0.13 N to 0.94 N in MC-1 to MC-6 for long fabric in fabric center region. The multiple-yarn (five yarns) accumulative retraction forces in CT714 fabric varied from 2.01 N to 10.20 N in MC-1 to MC-6 for short fabric and from 2.41 N to 5.38 N in MC-1 to MC-6 for long fabric in fabric edge region, whereas the multiple-yarn (five yarns) accumulative retraction forces in CT714 fabric varied from 1.74 N to 4.97 N in MC-1 to MC-6 for short fabric and from 1.07 N to 3.22 N in MC-1 to MC-6 for long fabric in fabric center region. The multiple-yarn accumulative retraction forces in the MC-1 to MC-6 of short CT716 and CT714 fabrics in the fabric edge and fabric center regions were higher than that of long CT716 and CT714 fabrics. In addition, the multiple-yarn accumulative retraction forces in the MC-1 to MC-6 of short and long CT716 fabrics in the fabric edge and fabric center regions were lower than those of short and long CT714 fabrics. These were not expected, but it could be related to fabric structural response. On the other hand, it was found that the multiple-yarn accumulative retraction forces in short and long CT716 and CT714 fabrics in fabric edge and center regions were slightly higher than those of the single-yarn retraction forces of CT716 and CT714 fabrics.

Figure 12.

Relationship between accumulative retraction force due to fabric structure and the number of mesocells in multiple-yarn pullout test of para-aramid fabric. (a) CT716 woven fabric (pulled yarn ends: 4) and (b) CT714 woven fabric (pulled yarn ends: 5).

Figure 13(a) and (b) shows the relationship between normalized Sk-Sp force (Is) and normalized accumulative retraction force (Ia), and the number of MCs in the multiple-yarn pullout test of CT716 and CT714 fabrics, respectively. As seen in Figure 13(a) and (b), the weft directional multiple Is and Ia in the MC-1 to the MC-6 of CT716 and CT714 fabrics in fabric edges decreased sharply, whereas no significant differences were obtained in the MC-1 to the MC-6 of CT716 and CT714 fabrics in fabric centers. The multiple Is in the MC-1of CT716 and CT714 fabrics in fabric edge were the highest, whereas the multiple Is in the MC-6 of CT716 and CT714 in fabric edge were the lowest. In addition, the multiple Is and Ia in the MC-1 to MC-6 of CT716 and CT714 fabrics in the fabric edge were higher than those in the fabric center. On the other hand, the multiple Is in CT716 fabric were higher than those in CT714 fabric due to fabric density. It was also observed that the multiple Is in CT716 and CT714 fabrics were higher than Ia. The number of the pullout ends and the position of the MCs affected the Is and Ia of CT716 and CT714 fabrics.

Figure 13.

Relationship between normalized stick–slip force (Is) and normalized accumulative retraction force (Ia) due to fabric structure and the number of mesocells in multiple-yarn pullout test of para-aramid fabric in the fabric edge and center regions, (a) CT716 woven fabric and (b) CT714 woven fabric (fabric length: 100 mm and pulled yarn ends: 4).

Figure 14(a) and (b) shows the relationship between Sk-Sp energy and accumulative retraction energy (pullout energy), and the number of MCs in the multiple-yarn pullout test of CT716 and CT714 fabrics, respectively. As seen in Figure 14(a) and (b), the multiple-yarn Sk-Sp energy and accumulative retraction energy in the MC-1 to MC-6 of CT716 and CT714 fabrics in the fabric edge were higher than those in the fabric center. On the other hand, the multiple-yarn Sk-Sp energy and accumulative retraction energy in CT716 fabric were higher than those in CT714 fabric due to fabric density. It was also observed that the multiple accumulative retraction energy in CT716 and CT714 fabrics were higher than Sk-Sp energy due to displacement. Mainly, the number of the pullout ends and fabric density and also the position of the MCs affected the Sk-Sp energy and accumulative retraction energy.

Figure 14.

Relationship between pullout energy in stick–slip and accumulative retraction force due to fabric structure and the number of mesocells in multiple-yarn pullout test of para-aramid fabric in the fabric edge and center regions. (a) CT716 woven fabric and (b) CT714 woven fabric (fabric length: 100 mm, pulled yarn ends: 3).

Conclusions

It was found that the decreasing line in the single- and multiple-yarn pullout force–displacement curves corresponds to each Sk-Sp region, whereas the increasing line in the single- and multiple-yarn pullout force–displacement curve corresponds to each accumulative retraction force by fabric structure (Af).

The weft directional single- and multiple-yarn Sk-Sp forces in the MC-1 of CT716 and CT714 fabrics were generally higher than those in the MC-6 of CT716 and CT714 in the fabric edges. The single- and multiple-yarn normalized Sk-Sp forces and normalized accumulative retraction forces also showed similar results. The MC-1 was found to be the most critical cell due to the starting point of the yarn pulling region and it was related to fabric boundary. The amount of Sk-Sp force and accumulative retraction force in multiple-yarn pullout were extremely nonlinear compared to that of the single-yarn pullout. On the other hand, the amount of Sk-Sp force was related to the number of interlacement points in the fabric, whereas the amount of accumulative retraction force was related to fabric structural response.

Sk-Sp force and accumulative retraction force depended on fabric density and the number of pulled yarn ends. In general, the Sk-Sp force and accumulative retraction force of CT716 and CT714 fabrics obtained from the multiple-yarn pullout test were higher than those of the single-yarn pullout test. On the other hand, the Sk-Sp forces of CT716 were higher than those of CT714 fabrics due to fabric density. It was also found that the Sk-Sp forces of long fabrics were higher than those of short fabrics due to the increasing number of crossing points.

The single- and multiple-yarn Sk-Sp and accumulative retraction energies in the fabric edge were higher than those in the fabric center. The single- and multiple-yarn Sk-Sp energies in dense fabric were higher than those in loose fabric. It was also seen that the multiple-yarn accumulative retraction energy in dense and loose fabrics was higher than Sk-Sp energy due to displacement. Mainly, the number of the pullout ends and fabric density and also the position of the MCs affected the Sk-Sp energy and accumulative retraction energy.

Future research should be conducted to find the analytical relation among Sk-Sp force, accumulative retraction force and yarn–fabric structural parameters. This could result in a multiaxially interlaced fabric with improved frictional properties, which could be used in soft ballistic applications.

Footnotes

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

References

Dong

Sun

. Testing and modeling of yarn pull-out in plain Kevlar fabrics. Compos Appl Sci Manuf 2009; 40(12): 1863–1869.

Kirkwood

Lee

. Yarn pull-out as a mechanism for dissipating impact energy in Kevlar KM-2 fabric. Part I: quasi-static characterization of yarn pull-out. Text Res J 2004; 74(10): 920–928.

Kirkwood

Lee

. Yarn pull-out as a mechanism for dissipating impact energy in Kevlar KM-2 fabric. Part II: predicting ballistic performance. Text Res J 2004; 74(11): 939–948.

Erlich

Shockey

Simons

. Slow penetration of ballistic fabrics. Text Res J 2003; 73(2): 179–184.

Rao

Duan

Keefe

. Modeling the effects of yarn material properties and friction on the ballistic impact of plain-weave fabrics. Comps Struct 2009; 89: 556–566.

Cheeseman

Bogetti

. Ballistic impact into fabric and compliant composite laminates. Compos Struct 2003; 61: 161–173.

Cunniff

. A semiempirical model for the ballistic impact performance of textile based personnel armor. Text Res J 1996; 66(1): 45–59.

Tan

VBC

Shim

VPW

Zeng

. Modeling crimp in woven fabrics subjected to ballistic impact. Int J of Impact Eng 2005; 32: 561–574.

Zeng

Tan

VBC

Shim

VPW

. Modeling inter-yarn friction in woven fabric armor. Int J Numer Meth Eng 2005; 66: 1309–1330.

10.

Rebouillat

. Tribological properties of woven para-aramid fabrics and their constituent yarns. J Mater Sci 1998; 33: 3293–3301.

11.

Sebastian

SARD

Bailey

Briscoe

. Effect of a softening agent on yarn pull-out force of a plain weave fabric. Text Res J 1986; 56(10): 604–611.

12.

Bilisik

. Pull-out properties of polyester woven fabrics: effects of softening agent and interlacement on single and multiple yarn pull-out forces and analysis by statistical model. Fiber Polym 2011; 12(8): 1106–1118.

13.

Briscoe

Motamedi

. The ballistic impact characteristics of aramid fabrics: the influence of interface friction. Wear 1992; 158: 229–247.

14.

Gawandi

Thostenson

Gillespie

Jr . Tow pullout behavior of polymer-coated Kevlar fabric. J Mater Sci 2011; 46: 77–89.

15.

Duan

Kefe

Bogetti

. Modeling the role of friction during ballistic impact of a high-strength plain-weave fabric. Compos Struct 2005; 68: 331–337.

16.

Duan

Kefe

Bogetti

. A numerical investigation of the influence of friction on energy absorption by a high-strength fabric subjected to ballistic impact. Int J Impact Eng 2006; 32: 1299–1312.

17.

Termonia

. Impact resistance of woven fabrics. Text Res J 2004; 74(8): 723–729.

18.

Bilisik

Korkmaz

. Multilayered and multidirectional stitched aramid woven fabric structures: experimental characterization of ballistic performance by considering yarn pull-out test. Text Res J 2010; 80(16): 1697–1720.

19.

Bilisik

Korkmaz

. Single and multiple yarn pull-outs on aramid woven fabric structures. Text Res J 2011; 81(8): 847–864.

20.

Bilisik

. Experimental determination of fabric shear by yarn pull-out method. Text Res J 2012; 82(10): 1050–1064.

21.

Bilisik

. Experimental determination of yarn pull-out properties of para-aramid (Kevlar^®) woven fabric. J Indust Text 2012; 41(3): 201–221.

22.

Sergienko

MacAyeal

Bindschadler

. Stick–slip behavior of ice-streams: modeling investigations. Ann Glaciol 2009; 50(52): 87–94.

23.

Gupta

. Friction in textile materials. Cambridge, UK: Woodhead Publishing Limited, 2008, pp. 95–105.

24.

Hearle

JWS

. High performance fibers. Cambridge, UK: Woodhead Publishing Limited and CRC Press LLC, 2001, pp. 69–70.

25.

MathWorks. MATLAB R2008a, Version 7.0, Computer program. Natick, MA: The MathWorks Inc., 2008.

Weft directional stick–slip force of yarn pullout in para-aramid fabric for ballistics

Abstract

Keywords

Introduction

Materials and methods

Para-aramid fiber and woven fabrics

Pullout tests

Results and discussion

Sk-Sp stage in the yarn pullout

Sk-Sp force in single-yarn pullout

Accumulative retraction force due to fabric structure in single-yarn pullout

Sk-Sp force in multiple-yarn pullout

Accumulative retraction force due to fabric structure in multiple-yarn pullout

Conclusions

Footnotes

Funding

References