Tensile Characteristics of Dual Sheath Single Core Hybrid High-performance Yarn

Abstract

Graphical Abstract

The concept of hybrid yarn is gaining popularity for its potential for several protective aspects, such as thermal protection, cut protection and so forth. Twelve distinct varieties of hybrid yarns with a core and two continuous filament sheaths were spun in this instance. These twelve yarns were primarily divided into two sub-divisions, one with glass fiber and the other with stainless steel (SS) in the core. Ultra-high molecular weight polyethylene (HPPE) was regarded as the outer sheath, and polyester yarn was the inner sheath layer. Two distinct varieties of HPPE yarns were chosen for performance comparison: 200D and 400D HPPE and 300D hard particle-impregnated HPPE (HPI-HPPE). Different twist directions of the sheath layers were also kept under consideration. The linear densities of the core yarn and outer sheath yarn were varied to observe the final hybrid yarn tensile properties with a fixed twist density (400 twists per meter). ASTM D2256 was followed to evaluate the tensile performance on the Instron universal tensile strength tester. The breaking strength and tenacity for S-Z twisted hybrid yarns were higher than for S-S twisted yarns. SS core yarns were finer than glass core yarns, which showed higher tenacity, modulus, and load-bearing capacity. Conversely, the strain percentage at maximum load was higher for glass core yarns than for SS yarns because of multiple phase cracking of glass core yarn. The HPI-HPPE yarns showed much lower tensile values than HPPE yarns. The reason was revealed by the surface morphology and CV% of diameter as an extensive necking tendency due to hard particle impregnation in HPI-HPPE yarn.

Introduction

Extreme level protection against different adverse environments is getting additional attention globally. Extreme heat and cold, cut, ballistic, and many more protections are also becoming core concentration areas for policymakers and researchers. Conventional natural fibers do not perform up to the mark against extreme environmental conditions and sharp forced action. Overcoming these issues has become a concern for end users and researchers. Hybrid yarn made from high-performance fibers is widely used in research areas to address adverse environmental and mechanical issues. The final tensile properties of the hybrid yarn are supremely important phenomena as it needs to withstand multiple types of external threats.

The primary task for producing any technical textile products will be selecting fibers for specific purposes and later producing yarns and fabrics as end products. Several types of high-performance fibers, such as UHMWPE, ¹ carbon fiber, ² aramid fiber, ³ PBO, ⁴ PBI, ⁵ basalt, ⁶ and glass fiber, ⁷ are already being used to produce hybrid high performance yarn. UPMWPE with aramid fibers was used to produce a hybrid yarn for stab resistance products, ¹ waste carbon fiber was used with aramid yarn to manufacture cut-protective yarns, ² a TiO₂ coating was used on aramid fiber surfaces for enhanced tensile performance, ³ and PBI was used to produce fire protective textiles and compared with Kevlar^®. ⁵ It was confirmed in previous studies that the failure pattern for technical fibers depends on their molecular structure and anisotropic nature.^8,9 More oriented and crystalline fibers showed higher tensile performance than less oriented fibers. The hybrid yarn concept arises from the concept of overcoming the definite fibers’ limitations with other benefits. The hybrid yarn consists of several types of fibers or layers, and the functions of these fibers and layers are different. ¹⁰ The layers of the hybrid yarn are selected based on the specific functional requirements of each layer for the intended end-use applications. This phenomenon helps to balance the final properties such as strength, flexibility, durability, and so forth of the yarn and fabric as expected. ¹¹ As it is not possible to get all of the desired properties from a definite fiber or yarn, multi-component yarn comes into the scenario as a consequence. ¹² Combining different required properties, corresponding fibers are selected and converted into yarn and ultimate fabric to get the final outcome.^10,13

The use of metal yarn such as stainless steel (SS) is gaining popularity in the field of electronic textiles. It is also being used as a raw material for electromagnetic shield garments, which provides protection from magnetic radiation. ¹⁴ Metal yarn plays a vital role in producing superconductor fabrics. ¹⁵ However, SS yarn significantly influences cut resistance when it is wrapped with other organic fibers. SS yarn without wrapping cannot be used in garments due to its higher thermal conductivity. ¹⁶ Therefore, it needs to be covered with other staple or continuous filament yarns to limit its exposure to the surface of the fabric. On the other hand, glass fiber also exhibits very high tensile force, and it has more acceptance in composite, belts, rubber, or tarpaulin industries than in the garment industries. The reason for this is the skin’s sensitivity to it. Glass fiber is highly brittle and abrasive in nature and consequently, after getting broken, it imparts scratchiness and itchiness to the skin. ¹⁷ To overcome this issue, like SS yarn, glass fiber can also be kept in a core and wrapped with organic fibers to prevent its exposure at the fabric surface. However, practical data showed that even after wrapping, the glass fiber still could come out onto the fabric surface and initiate irritation to the wearer. So, a better solution is to use glass fiber fabric as the outer layer of a multi-layer fabric so that the protruding glass fiber cannot be exposed to the skin. ¹⁸ On the other hand, PTFE-coated glass is being used as the core so that the glass fiber exposure after breakage is stopped by the PTFE coating material. As PTFE is very costly and the coating needs an additional mechanism to perform, only for high-end products with heavy cost, PTFE coating can be performed. ¹⁹ In addition to that, glass fiber with 50–200D with multifilaments (5.5–9.0 µm) is used for protective textiles, whereas others are suitable for use in automobile and other technical industries. ²⁰ In this research, following permissible criteria, glass yarn linear density was considered.

Ultra-high molecular weight polyethylene (UHMWPE) is a highly crystalline form of polyethylene (PE) polymer with a very high degree of polymerization (71,000–214,000) and an ultra-high molecular weight (2–6 million g/mol). ²¹ The high-performance polyethylene (HPPE) fiber term is used when UHMWPE is produced through a gel spinning process from polyethylene. As a high-performance yarn, HPPE has very high resistance against cut performance and other superior properties, such as an excellent strength retention percentage in a normal atmosphere as well as under alkali and acid exposure. Whereas other aramid fibers lose their strength rapidly (70–80%) under strong alkali and acid exposure, HPPE loses only a maximum of 10% of its strength. It also consists of very high tenacity and modulus with a very smooth surface with a slippery nature that helps to protect against sharp knife actions. ²² There are very few studies conducted solely focusing on the tensile properties of hybrid yarn whereas the use of hybrid yarn hass increased in protective textiles.^23,24 Thus, scientists need to depend on the individual yarn tensile properties, which helps to get an idea about the final hybrid yarn tensile performance. For example, research was conducted on Zylon, Kevlar and Spectra yarns to evaluate their cut performance. ²⁵ Although there is no standard for yarn cut resistant test, researchers developed a self-method to evaluate the cut performance and concluded that Zylon has better cut resistance than Kevlar and Spectra. It also mentioned that slice angle dominates the cut resistance performance and cut resistance depends on the sharpness of the blade.^26,27 However, this study did not establish a correlation between the yarn cut resistance and its tensile performance. Since tensile properties determine the deformation of a yarn under force, they are expected to influence its cut resistance.

Bedeloglu et al. ²⁸ produced single core single sheath spun yarn using metal wire for core and cotton for a sheath layer for electromagnetic shielding purpose. The bending rigidity of the yarn was increased for metal wire incorporation. The tensile performance of the yarn was found variable for different metal percentages, and they suggested the need for future work on tensile performance. Another group of researchers produced spun hybrid yarn by using recycle carbon fiber (rCF) and polyamide 6 (PA6) fiber.^2,29 The authors verified the tensile performance of different yarns produced in several ratios of rCF and PA6 followed by composite preparation and correlated the tensile strength of the composite with the twist per meter of the yarn. The tensile strength of the composite was greatly affected by rCF fiber length, rCF content percentage and twist per meter. It provided an insight into the necessity of measuring tensile properties of hybrid yarn which widely depended on its component yarns. Similarly, there have a lot of research on cut-resistant clothing,^16,20–22 stab-resistant textiles,^23,24 and fire protective fabrics^25–27 where hybrid and blended yarns were used; however, in neither article was the yarn tensile performance measured. The tensile performance of hybrid yarn having two sheath layers and one core remains an untouched arena.

Therefore, this research project was conducted to prepare a kind of hybrid yarn where two sheath layers will be considered with a single-core filament yarn. As it is a combination of different types of yarn, the cumulative tensile properties of these different types of yarn need to be measured and the findings interpreted before final use to finalize the end-use category, for example, cut protective textiles.

Materials and Methods

Materials

Hybrid High-performance Yarn

For this research, three different micron thicknesses of stainless steel (SS; 30, 40, 50 µm) were selected, which were being manufactured and used most in terms of their diameter. For the purpose of making multicomponent hybrid yarn, ultra-high molecular weight polyethylene (HPPE) was chosen for its excellent strength-to-weight ratio, low density, outstanding tensile properties, and high crystallinity. The linear densities of 200D, 300D, and 400D HPPE were chosen for the final hybrid yarn. It should be mentioned that hard particle-impregnated HPPE (HPI-HPPE) is a special type of HPPE fiber, which was supplied by High-Performance Textiles Pvt Ltd, Panipat, Haryana, India, especially focusing on the cut resistance phenomenon. 300D HPI-HPPE yarn was selected to compare with 200D and 400D conventional HPPE yarns, which are commonly used in cut-resistant applications. Specifically, the 300D HPI-HPPE yarn was chosen to establish a correlation with its lower and higher linear density counterparts, enabling a comprehensive analysis of its mechanical behavior relative to traditional HPPE fibers. This selection also allowed for the evaluation of HPI-HPPE performance while minimizing sample preparation costs. The glass yarn linear density was selected as 100D, 200D, and 300D depending on its availability and suitability for use as a core in a multi-component yarn. All the multicomponent yarns were manufactured at High-Performance Textiles Pvt. Ltd, Panipat, Haryana, India.

Due to the crystallinity and manufacturing techniques, the surface of SS, glass, and HPPE fibers exhibits a very slippery nature. For this reason, it becomes difficult to incorporate HPPE fiber with SS and glass fiber using core spinning technology or yarn covering technology. This issue can be solved by using textured polyester multifilament yarn in between HPPE and SS or HPPE and glass filaments. ²² Polyester fiber has higher frictional resistance than HPPE, SS, and glass fibers, and for this reason, polyester can form some extra cohesion with these fibers through friction. Keeping all the fiber frictional properties in mind, two separate types of yarn samples were prepared following the wrap spinning technology shown in Figure 1(b). For one sample, SS was in the core as in Figure 1(c), and in another, the glass filament was considered in the core as in Figure 1(d). As polyester works as a cohesive material, for both the core yarns, polyester is kept in the middle layer; in other words, it can be mentioned as the first sheath layer or inner sheath layer. The outer layer was allocated for the HPPE fiber. Twists per meter for all the samples were taken as the same at 400 to avoid its effect. Figure 1(a) demonstrates the schematic diagram of both types of yarn.

Figure 1.

(a) Stainless steel/glass core hybrid yarn, (b) wrap spinning technique, (c) SS core yarn, and (d) glass core yarn.

Instron Universal Strength Tester

The Instron universal strength tester is widely used to analyze yarn strength. For this research, an Instron 3365, USA, was selected to perform the final yarn tensile performance. Before testing, the machine was calibrated with the proper jaw and a 2000 N load cell was selected and installed accordingly.

Yarn Diameter Verification

The diameter uniformity of yarn is crucial for its tensile properties. A thin place in the yarn means a weak place where the failure of the yarn occurs. Therefore, the CV% of the yarn diameter needs to be evaluated. In this research, a Leica DM 2700 M, Germany microscope was chosen to verify the required yarn diameter.

ANOVA Analysis and Effect Size Observation

Analysis of variance of means of different tensile properties was used to determine the significance of 12 different types of yarns. OriginLab 2020b software was selected to perform the ANOVA analysis. The effect size of the samples was calculated using the eta-squared method. The equation of eta squared is given below:

$${\eta }^2=\frac{\mathrm{Sum}\mathrm{squares}\mathrm{between}\mathrm{groups}(\mathrm{Model})}{\mathrm{Total}\mathrm{sum}\mathrm{of}\mathrm{squares}(\mathrm{Total})}$$

According to Cohen’s de criteria, the effect size can be declared as small effect ( ${\eta }^2=$  0.01−0.06), medium effect ( ${\eta }^2=$  0.06−0.14), and large effect ( ${\eta }^2>0.14$ ). ³⁰

Methods

Hybrid High-performance Yarn Manufacturing Procedure

A hollow spindle wrap spinning process was followed to produce the high-performance yarns in this research. Double-stage wrapping was carried out to manufacture dual sheath single core wrap spun yarn (Figure 1). As these yarns were produced at High-Performance Textiles Pvt. Ltd, Panipat, Haryana, India, industrial optimum speeds for glass and SS yarns were considered for each stage.

The final hybrid yarn consisted of three different components with different linear densities. Therefore, before attempting the tensile test, measuring the final yarn linear density was necessary. By using the conventional method, the linear density (in tex) of the yarns was calculated, and an average of ten values is tabulated in Table 1.

Table 1.

Stainless steel/glass core hybrid high-performance yarns produced for tests.

Code	Fiber composition			Twists permeter	Twistdirection	Calculated finalcount (Tex)
	Core	Inner layer	Outer layer
Y1	SS-30 µm	100D(Polyester)	HPPE-200D	400	S-Z	40
Y2	SS-40 µm	HPI HPPE-300D	S-Z		65
Y3	SS-50 µm	HPPE-400D	S-Z		75
Y4	SS-30 µm	HPPE-200D	S-S		40
Y5	SS-40 µm	HPI HPPE-300D	S-S		65
Y6	SS-50 µm	HPPE-400D	S-S		75
Y7	Glass-100D	HPPE-200D	S-Z		50
Y8	Glass-200D	HPI HPPE-300D	S-Z		75
Y9	Glass-300D	HPPE-400D	S-Z		95
10Y	Glass-100D	HPPE-200D	S-S		50
Y11	Glass-200D	HPI HPPE-300D	S-S		75
Y12	Glass-300D	HPPE-400D	S-S		95

Tensile Properties Test

The ASTM D2256 method was followed to evaluate the tensile properties. Special care was taken while setting yarn on the machine jaw so that the testing yarn did not bend at any place on the test length. ³¹ Since SS yarn deforms and glass fiber breaks after bending, before testing, any bending on the test length might lead to a wrong interpretation of the yarn. The gauge length was considered as 250 mm, the elongation rate was taken as 300 mm per minute and a 2000 N load cell was selected; average values of 10 yarns were taken for further discussion. It was confirmed that there was no slippage during tensile force application. Slippage during tensile strength testing leads to wrong tensile results. The final tensile properties such as maximum force, initial modulus, strain at maximum load, tenacity and energy at break were measured and tabulated for further interpretation.

Morphology

Two end points of corresponding fibers like SS, glass fiber, HPPE, HPI-HPPE, and polyester were gummed onto a glass slide, maintaining uniform tension so that the yarn remained straight enough to be tested on its surface under a microscope. The microscope lens was set to capture HPPE images at a 75 µm scale, SS fiber images at a 50 µm scale, and a 10 µm scale for glass fiber and polyester fiber. The scale was selected according to the suitable visibility of the fiber. A total of 250 values of each fiber diameter were measured, and the average was tabulated for further discussion.

Results and Discussion

Properties of Materials

For both types of yarn, the inner sheath layer (polyester) kept the same S-twist direction. The outer sheath layer of 50% samples was twisted in the S-twist direction, and the rest of the samples were twisted in the Z-twist direction. A total of 12 samples were prepared at different combinations, as shown in Table 1. Samples were coded as 1Y–12Y, where 1Y–6Y yarns were made with stainless steel and 7Y–12Y yarns were made with glass fiber. More precisely, 1Y–3Y samples were made in inner sheath S-twist and outer sheath Z-twist and 4Y–6Y samples were made with same inner and outer sheath twist direction as the S-twist. Following the same procedure, 7Y–12Y samples were prepared with glass fiber in the core, 7Y–9Y with an S-Z twist direction for the inner and outer sheath, and 10Y–12Y with an S twist direction for both the inner and outer sheath layer. The final linear density of the yarns increases with increasing SS micron and HPPE linear density.

Tensile Property Evaluation

Maximum Force at Breaking of Hybrid Yarns

Figure 2 displays the maximum load-bearing capacity before breaking of each multi-component yarn. In every instance, hybrid yarn with SS in the core exhibited a better tensile strength than hybrid yarn with glass core. It was discovered that 400D HPPE comprising yarns (Y3, Y6, Y9, Y12) for both SS (80.23 N for Y3 and 59.39 for Y6) and glass core (63.08 N for Y9 and 58.76 for Y12) had the maximum force-bearing capability.

Figure 2.

Maximum force (N) of different types of hybrid yarn.

In contrast to 200D (Y1, Y4, Y7, Y10) and 400D HPPE yarns (Y3, Y6, Y9, Y12), the 300D HPI-HPPE yarns (Y2, Y5, Y8, Y11) demonstrated significantly reduced tensile force characteristics. It was assumed that higher linear density could indicate higher tensile qualities even though the SS, glass, and HPI-HPPE linear densities of Y2, Y5, Y8, and Y11 were higher than those for Y1, Y4, Y7, and Y10, respectively. In this instance, nevertheless, 300D HPI-HPPE had the opposite characteristics.

While SS 30 µm and HPPE 200D hybrid yarns (Y1, Y4) showed better maximum force, being finer (51.69 N for S-Z twist and 53.56 N for S-S twist), SS 40 µm and HPI-HPPE 300D hybrid yarns (Y2, Y5) demonstrated maximum forces of 43.03 N for S-Z twist yarns and 34.53 N for S-S twist yarns. Glass core yarn showed the same phenomenon. While 100D glass and 200D HPPE yarns (Y7, Y10) showed significantly better tensile force (47.05 N for S-Z twist and 45.76 N for S-S twist), 200D glass with 300D HPI-HPPE hybrid yarns (Y8, Y11) exhibited much lower maximum force values, like 33.18 N for S-Z twist and 32.80 N for S-S twist.

Figure 2 also shows the effect of the twist direction of the outer sheath layer. The tensile force of finer hybrid yarns (40 tex SS core and 50 tex glass core) was slightly lower in the S-Z outer sheath twisted yarn compared to course hybrid yarns. As the linear density of the hybrid yarn increased, the maximum force at breaking for S-Z twisted yarns was significantly greater than for S-S twisted yarns. This occurred because S-Z twisted yarns had more surface cohesion and load distribution possibilities than S-S during application of tensile force in the testing machine. Tensile forces can be divided in more directions by inversely twisted hybrid yarns than by twisted yarns oriented in the same direction. As a result, the load-carrying capability of S-Z yarns was increased. However, with lower hybrid yarn linear density, this characteristic was seen less due to the diameter of the yarn, resulting in less cohesion and load distribution.

The maximum load-bearing capacity of the hybrid yarns showed a statistically significant difference at the p < 0.05 level: F (11:108) = 71.16585, p = 2.77E – 44 in Table 2. Cohen’s d indicated a very high mean difference between the groups, and the effect size of the samples was determined using eta squared, which came out as 0.88 (>0.14).

Table 2.

ANOVA analysis and effect size of maximum force (N).

Source of variation	Degree of freedom (DF)	Sum of squares	Mean square	F value	Prob > F	Effect size ( ${\eta }^2$ )
Model	11	21,800.49	1981.863	71.16585	2.77E – 44	0.88
Error	108	3007.639	27.84851
Total	119	24,808.13

Tenacity of Hybrid Yarns

In Figure 3, the tenacity of each hybrid yarn is displayed. Glass core yarns were found to have lower overall tenacity than SS core hybrid yarns. Y1 (1.29 N/Tex) and Y4 (1.34 N/Tex) hybrid yarns have more tensile force-bearing capacity (tenacity) than Y2 (0.66 N/Tex), Y5 (0.53 N/Tex), Y3 (1.07 N/Tex), and Y6 (0.79 N/Tex) SS core hybrid yarns. In a similar vein, Y8 (0.44 N/Tex), Y11 (0.44 N/Tex), Y9 (0.62 N/Tex), and Y12 (0.62 N/Tex) glass core hybrid yarns showed less tenacity than Y7 (0.94 N/Tex) and Y10 (0.92 N/Tex) glass core hybrid yarns.

Figure 3.

Tenacity of different types of hybrid yarns.

In addition, 300D HPI-HPPE samples for glass core and SS yarns (Y2, Y5, Y8, Y11) showed lower tenacity than 200D (Y1, Y4, Y7, Y10) and 400D (Y3, Y6, Y9, Y12) HPPE yarns. Except for 40 tex SS core yarns (Y1, Y4), higher hybrid yarn linear density demonstrated a higher yarn tenacity of S-Z twisted yarns than for S-S twisted yarns in most cases. The reason already mentioned in the tensile force discussion is less cohesion and lower load distribution capacity due to the smaller yarn diameter.

Table 3 shows that the tenacity of the hybrid yarns differed statistically significantly at the p < 0.05 level: F (11:108) = 90.42, p = 3.10E – 49. Cohen’s d indicated a significant mean difference between the groups, and the effect size of the samples was determined using eta squared, which came out as 0.90 (>0.14).

Table 3.

ANOVA analysis and effect size of tenacity.

Source of variation	Degrees of freedom (DF)	Sum of squares	Mean square	F value	Prob > F	Effect size ( ${\eta }^2$ )
Model	11	10.42	0.95	90.42	3.10E–49	0.90
Error	108	139.73	1.29
Total	119	1455.5

Initial Modulus

The initial modulus of the hybrid yarns is plotted in Figure 4. Likewise, the initial modulus of the yarns exhibited a trend similar to the tenacity performance of the hybrid yarns. The SS core hybrid yarn exhibited higher modulus values than glass core yarns.

Figure 4.

Initial modulus of different types of hybrid yarns.

For most of the cases, the S-Z twisted yarn showed higher modulus values than the S-S twisted yarn. Moreover, finer hybrid yarns (Y1, Y4 for SS and Y7, Y10 for glass core) showed higher initial modulus values (around 372 N for SS and 222–247 N for glass) than courser yarns’ modulus values (244–278 N for SS and 162–192 N for glass). However, in this case also, the 300D HPI-HPPE yarns for both SS and glass core hybrid yarns (Y2, Y5, Y8, Y11) showed much lower initial modulus values than 200D (Y1, Y4, Y7, Y10) and 400D (Y3, Y6, Y9, Y12) HPPE yarns in both the S-Z and S-S twist directions.

Table 4 explores how the initial modulus of hybrid yarns differed significantly at the p < 0.05 level: F (11:108) = 67.95, p = 2.41E – 43. Using eta squared, the effect size of the samples was determined to be 0.87 (>0.14), and Cohen’s d indicated that there was a significant mean difference between the groups.

Table 4.

ANOVA analysis and effect size of initial modulus.

Source of variation	Degrees of freedom (DF)	Sum of squares	Mean square	F value	Prob > F	Effect size ( ${\eta }^2$ )
Model	11	6056.89	550.63	67.95	2.41E – 43	0.87
Error	108	112,348.5	1040.26
Total	119	889,864.4

Strain-percent at Maximum Load

The deformation against load is known as strain and has been plotted in Figure 5 in terms of percentage.

Figure 5.

Strain-percent at maximum load of different types of hybrid yarns.

In general, SS core hybrid yarns had of lower strain-percent values (5.72–7.51%) than glass fibers (7.62–9.80%). In S-Z and S-S twisted yarns of 300D HPI-HPPE (Y2, Y5, Y8, Y11), S-S twisted yarns exhibited higher strains for both SS (Y5) and glass (Y11) core yarns. For 200D and 400D HPPE yarns, mostly S-S twisted yarns experienced higher strain-percent values at maximum load except for the 200D glass core yarns (Y7, Y10).

It was evident from Figures 2–4 that the glass core hybrid yarns had lower initial modulus, tensile force, and tenacity than the SS core yarns. The deformation rate of glass core yarns was higher because of the brittleness of the glass fibers. Glass fibers are more brittle than SS fibers and glass fibers show less extensibility than SS yarns. That is why glass fiber breaks at its start, and the rest of the HPPE and polyester yarns extend more. But SS yarn is ductile in nature that is why it can extend under tensile force and SS core yarn breaks at a time within a lower strain-percent than glass core yarn. For this reason, glass core hybrid yarn showed higher extensibility than SS core yarn. Figure 9(a) provides a graphical explanation of this phenomenon.

Table 5 depicts the strain-percent at maximum load, showing a statistically significant difference at the p < 0.05 level for 12 hybrid yarn samples: F(11,108) = 20.56058, p = 8.68E – 22. The effect size of the mean difference was measured by eta squared, and the value was 0.68 (>0.14), which indicates that the effect size of the mean difference was very high. The p-value also indicates that it is far less than 0.05.

Table 5.

ANOVA analysis and effect size of the strain-percent at maximum load.

Source of variation	Degrees of freedom (DF)	Sum of squares	Mean square	F value	Prob > F	Effect size ( ${\eta }^2$ )
Model	11	208.2413	18.93103	20.56058	8.68E – 22	0.68
Error	108	99.44036	0.92074
Total	119	307.6817

Energy at Breaking

Figure 6 showed how hybrid yarns failed in terms of energy. Figure 9(a) provides insight into the energy at breaking of the hybrid yarns. Interestingly, glass core hybrid yarns had more energy at breaking than SS core hybrid yarns did. The greater strain percentage of glass core hybrid yarns was the cause of this. More areas under the load elongation curve, which represented the breaking energy, was the result of a higher strain percentage at maximum load. For Y3 and Y6 SS core hybrid yarns, the maximum energy at break was found to be 0.37 J for S-S twisted yarn and 0.516 J for S-Z twisted yarn.

Figure 6.

Energy at break of different types of hybrid yarns.

Likewise, for glass core hybrid yarns, the maximum energy upon breaking was found at Y9 and Y12 yarn linear density, or more precisely, at 0.602 J for S-Z twisted yarn and 0.5 J for S-S twisted yarn. Conversely, the hybrid yarns with 300D HPI-HPPE (Y2, Y5, Y8, Y11) showed the lowest energy upon breaking for both glass core and SS yarns. Glass core HPI-HPPE hybrid yarns (Y8, Y11) had a higher energy at breaking than SS core HPI-HPPE yarns (Y2, Y5) due to their higher strain-percent at maximum load.

In Figure 6, the effect of twist direct was also noted. Higher energy at breaking for S-S twisted yarn was found in finer hybrid yarn counts, compared to S-Z twisted yarns. S-Z twisted yarns exhibited more energy at breakage than the other yarns. It could be claimed that S-Z twisted courser hybrid yarns showed higher energy upon breaking.

For the 12 hybrid yarn samples in Table 6, the energy at break revealed a statistically significant difference at the p < 0.05 level: F(11,108) = 33.43721, p = 8.02E – 30. Eta squared was used to calculate the effect size of the mean difference, and the result was 0.77 (>0.14), indicating a very high effect size. Because it is far smaller than 0.05, the p-value likewise shows the same thing.

Table 6.

ANOVA analysis and effect size of energy at break.

Source of variation	Degrees of freedom (DF)	Sum of squares	Mean square	F value	Prob > F	Effect size ( ${\eta }^2$ )
Model	11	1.60319	0.14574	33.43721	8.02E – 30	0.77
Error	108	0.47074	0.00436
Total	119	2.07393

Tensile Properties Evaluation of HPPE and HPI-HPPE Yarns

Figures 2–6 demonstrate that, in each instance, the 300D HPI-HPPE yarns (Y2, Y5, Y8, Y11) had some surprising outcomes compared to the HPPE yarns. Since no other types of yarns were utilized in the SS, glass, or polyester cases, it was assumed that HPPE and HPI-HPPE yarns were the source of the odd results. To verify the reason for this case, the tensile performance of all the component yarns was performed separately, and the same kind of result was seen (Table 7). With the increment of yarn linear density, the maximum load at break was increased for all yarns except the HPPE and HPI-HPPE yarns.

Table 7.

Tensile properties of HPPE and HPI-HPPE yarns.

Yarn type	Filamentdiameter (µm)	Number offilaments	Maximumload (N)	Tenacity (N/Tex)	Strain atmaximumload (%)	Modulus(N/Tex)	Energy atbreaking (J)
SS-30 µm	30	1	0.54	0.11	18.518	13.85	0.003
SS-40 µm	40	1	1.44	0.14	20.169	18.55	0.008
SS-50 µm	50	1	1.71	0.11	28.046	15.31	0.013
G-100D	5.5	200	9.22	0.83	3.609	28.07	0.006
G-200D	5.5	400	15.11	0.68	3.811	22.94	0.009
G-300D	9.5	200	18.61	0.56	3.737	18.61	0.012
HPPE 200D	25	90	59.16	2.66	5.204	54.74	0.339
HPI-HPPE 300D	30	90	38.54	1.16	4.734	27.15	0.174
HPPE 400D	15	180	91.11	2.05	6.214	42.87	0.528
PE-100D	15	36	4.41	0.40	17.048	5.18	0.02

Table 7 clarifies the whole situation and explains the underlying issue of the earlier discussion. Compared to HPPE 200D and 400D linear density yarns, HPI-HPPE 300D had a much lower maximum force before the break. From then on, the primary cause of this type of outcome was the surface morphology of the HPI-HPPE and HPPE yarns, which were examined using Leica DM 2700 M, Germany.

The images of individual fiber diameters are illustrated in Figure 7. Measured diameter values of HPPE and HPI-HPPE are accumulated, and the CV% is calculated and demonstrated in Figure 8.

Figure 7.

Microscopic view of: (a) 30 µm SS, (b) 40 µm SS, (c) 50 µm SS, (d) filament of 100D glass yarn, (e) filament of 200D glass yarn, (f) filament of 300D glass yarn, (g) filament of 200D HPPE, (h) filament of 300D HPI-HPPE, (i) filament of 400D HPPE, and (j) filament of 100D polyester yarn.

Figure 8.

Fiber diameter of HPPE and HPI-HPPE with CV%.

From Figure 7(h), it is clear that there was a serious necking tendency in HPI-HPPE yarn due to the thick and thin places produced by hard particle impregnation on it, whereas all other filaments of yarn showed a much more uniform diameter. Figure 8 clarifies the diameter variation range at the error bar, where the coefficient of variation of HPI-HPPE fibers is much higher than that of HPPE yarns. It signifies that the HPI-HPPE fiber consists of more thick–thin places, which causes the decline in tensile-related properties.

HPI-HPPE was supplied by High-Performance Textiles Pvt Ltd, Panipat, Haryana, India, and the specialty of this yarn was superior cut protection compared with other HPPE or convention-similar types of fibers. HPI-HPPE is embedded with micro-hard particles, which work to blunt the sharp edges. However, for the impregnation of these micro hard particles into the fiber, the diameter of the fiber surface became rougher and uneven, resulting in a non-uniform fiber surface. This eventually led to the thick–thin places in the final yarn, causing a greater drop in maximum force at breaking.

It was also seen that the diameter of HPPE 400D fibers was much less than that of other HPPE fibers, and that may be another factor contributing to the significantly higher maximum force at breaking of 400D HPPE compared to other HPPE and HPI-HPPE yarns.

Load Elongation Curve

The tensile performance of all hybrid yarns (Figure 9(a)) and their component yarns (Figure 9(b)) is illustrated through the load–elongation curves presented in Figure 9. In Figure 9(a), the tensile behavior of the hybrid yarns reveals a distinctive phenomenon of multiple-phase cracking, particularly observed in hybrid yarns with glass cores. This behavior is notably absent in hybrid yarns with stainless steel (SS) cores. The underlying reason for this phenomenon can be explained by the data in Figure 9(b), which shows that the breaking elongation of the glass yarn is significantly lower than that of the SS yarn. As a result, in glass-core hybrid yarns, the glass yarn reaches its breaking point earlier during tensile loading, whereas the SS yarn in SS-core hybrid yarns exhibits greater elongation before failure.

Figure 9.

Some load elongation curves of: (a) hybrid yarns and (b) component yarns.

Conclusion

This paper shows the detailed tensile properties of multi-component hybrid yarns made with SS, glass, polyester, HPPE, and HPI-HPPE yarns, which may be used in cut protective garments items. SS (30, 40, 50 µm) and glass yarn (100D, 200D, 300D) were considered the core material for two separate combinations of outer sheath layers. For both types of core yarns, polyester (100D) was kept in the first or inner layer, and HPPE (200D, 400D)/HPI-HPPE (300D) yarn was kept in the outer sheath. For verifying the twist direction influence of outer sheath layers, an outer and inner sheath layer combination was made in S-Z and S-S directions. Following the standard of tensile property evaluation, the final results were obtained. Courser hybrid yarn for both SS core and glass core showed higher tensile force than other hybrid yarns and SS core hybrid yarn’s maximum force at break was higher than that of glass core hybrid yarns. The ductility of SS yarn, which is higher than that of glass yarn, was the possible reason for this result. However, the tenacity and initial modulus value of finer hybrid yarns were higher than those for courser yarns for both SS and glass core yarns. On the other side, the strain-percent at maximum load was higher for glass core yarns than for SS core yarns and the courser yarns exhibited higher strain-percent values than finer yarns. The brittleness of glass fiber is responsible for this kind of finding, where glass yarn breaks far earlier than sheath layers. Therefore, the strain occurs from the sheath layers. The combination of maximum force at break and strain-percent influenced the energy at breaking value of the yarns. For higher force at breaking of course yarns, the energy at breaking of course yarns was found to be higher, and for higher strain-percent values of glass core hybrid yarns, the energy at the break of glass core yarns was higher than that for SS core yarns. HPI-HPPE yarn showed lower tensile force at breaking, tenacity, modulus, and energy at breaking than HPPE-containing hybrid yarns. Due to the impregnation of micro metal particles in HPI-HPPE for improved cut performance, the thick–thin place in the fiber increases, and that causes early breakage of yarn during tensile force application. The microscopic images and CV% deviation of the fiber diameters confirm the thick–thin place of the HPI-HPPE fibers. For this reason, HPI-HPPE yarns are being suggested for use only in low-stress wearable cut protective garments, and other HPPE yarns can be used in high load bearing cut protective articles. In contrast, HPI-HPPE yarn is not suitable for those kinds of technical textiles where higher load-bearing capacity is required.