Abstract
This study aims to examine the effect of rib set-out repeat on the structural characteristics and mechanical properties of double-knitted fabrics after dry relaxation and four washing cycles. The focus is on the behavior of the fabrics in terms of dimensional stability and stretch properties. Half Milano rib and nine variants of double weft knitted fabrics differed by the number of inactive needles in the rib set-out repeat were produced from a 25 × 2tex × 2 cotton/flax yarn on a 10-gauge flat-bed knitting machine. It was found that the rib set-out repeat affects dimensional changes in both directions: an increase in the number of inactive needles increases shrinkage. The rib set-out repeat also significantly influences the structural characteristics. As the number of inactive needles in the rib set-out repeat increases, the double-knitted fabric becomes denser, thicker, and heavier. The analysis of stretchability indicates that the repeat didn`t affect full lengthwise deformation but affected the full widthwise deformation. Fabrics with an identical percentage of inactive needles (50%) exhibit minimal differences in properties. The study results are particularly significant for a manufacturer to enhance the quality of knitted fabrics by understanding their dimensional stability and stretch performance.
Keywords
Introduction
Manufacturers continually search for novel textile materials with distinctive properties, encompassing surface, structural, and optical characteristics, to cater to the increasing demand for variety clothing aesthetics. The potential of a variety of weft-knitted structures remains untapped despite the availability of various base stitches: knit, miss (float), tuck, and purl. Mass production predominantly relies on weft-knitted structures such as single jerseys, rib patterns, interlock, and half and full cardigans. Additional stitches like jacquard, known for its colored effects; purl stitch, appreciated for its surface texture; and the open stitch, admired for its lace-like effect, are also popular.
The production and use of knitted fabrics and clothing are subject to multiple factors that can cause deformations and changes in appearance and structure, even with minor forces. To create knitted fabrics and clothing with suitable properties that retain their form and appearance over time, it is important to thoroughly examine the elements that help maintain fabric shape and stretchability. The properties of knitted fabric, such as dimensional stability and stretchability, are influenced by yarn type, knit structure, and relaxation type.1,2 Between these factors, knit structure plays a crucial role. 2 The interconnections between each stitch type (such as knit, miss, and tuck) in the structure determine the knitted fabric’s structural characteristics and main properties. To predict these defining traits, researchers use two approaches: theoretical, by creating geometric models, and experimental, by conducting research into the underlying relationship. Geometric models are particularly useful for understanding basic knit structures, such as plain and 1 × 1 rib.3–9 A relaxed state concept has been used to create geometric models that account for a range of knit structures, even those with missed stitches 10 and different rib structures. 11 However, three key issues still that need to be addressed to fully understand the knitted fabric: determining the type of knit structure, calculating stitch characteristics, and understanding yarn interactions.12,13
A large variety of knit structures with different physical and mechanical characteristics can be created using different stitch types (knit, miss or float, tuck) and their alternation.14–17 Research studies have proven that each knit structure has distinct qualities, and the selection of a structure depends on the fabric’s intended application and desired properties.16–21 It is important to understand how the stitch types influence specific characteristics to produce knitted fabric with suitable properties.
Rib structures, with their varied stitch combinations, offer versatility for decorative knitting and technical applications requiring elasticity and adaptable contours. 22 Comparing fabric properties between the 4 × 1 rib and 4 × 4 rib knitted fabrics 23 highlights a notable impact of the knit structures. From the study, 24 it was found that the rib knit structures (1 × 1, 2 × 1, 2 × 2, 3 × 1, and 3 × 3) impact properties as drape coefficient percentage, bending length, flexural rigidity, and tightness factor. The tensile behavior of rib structures is influenced by rib patterns. 25 The experiments indicate that combining different rib structures can yield better results. Using various rib knit in conjunction with a plain knit leads to creating a fabric with a wide range of characteristics. 26 To reduce stress in knitted fabrics, it is important to consider the ratio between loop length in the plain and rib courses in complex knit structures such as half Milano rib. Including missed stitches in the interloping repeat significantly affects the fabric`s properties, such as drape, widthwise extensibility, shrinkage, thickness, density, and low-stress mechanics.27,28 There is still a gap in research regarding using rib with different repeats as one of the components in complex knitted structures.
The knitted fabrics and garments during production and use are subject to various stresses and loads, varying in magnitude, direction, and duration. These cyclic processes can significantly affect the fabric’s structure and lead to linear changes in dimensions or deformations in the garments. This can compromise the product’s appearance and negatively impact its functional properties.
The most significant changes in linear dimensions occur due to wet heat treatments, especially during washing and soaking. The dimensional changes from the dry-relaxed to the washing-relaxed state exhibit significant dependence on loop length rather than treatment level.29,31 In early Knapton work 30 it was stated that these changes are isotropic, indicating that the dimensions uniformly decrease during the relaxation process, both lengthwise and widthwise. However, the changes in thickness were not taken into account. Knitted fabrics have experienced the most significant dimensional changes after the first wash. Research 31 demonstrate that using miss stitches in the interlooping repeat (half Milano rib, crossmiss interlock) can significantly improve dimensional stability compared to fabrics made with only knit stitches (1 × 1 rib). Wet treatments primarily modify the loop structure of the fabric, with swelling-induced alterations in thread and fiber structures playing a secondary role. Examination of various relaxation techniques, such as knitting and dry relaxation, dye and dry relaxation, and dye and wash relaxation, revealed that the shape of the loop and stitch length are the key factors affecting the dimensional properties of cotton knitted fabrics. 31 Additionally, the dimensional properties of plain knitted fabrics depend on the laundering procedure and the quantity of the fabric.32–35 The dimensional changes of knitted fabrics after washing depend on their structural parameters 36 and the raw materials used. 37 Therefore, it is important to understand the material’s behavior after different relaxation processes and to identify the impact of interlooping repeats.
The main technological parameters, such as the linear density and preliminary tension of the yarn,38,39 type of knit structure,38,40 and structural parameters,41,42 are the most influential factors for the stretch properties of knitted fabrics. Missed stitches have a dual impact on the fabric’s elasticity, depending on the direction. 43 Their presence diminishes the fabric’s elasticity along the width and enhances it along the length. Extensive research on the influence of knit structure on stress relaxation in weft-knitted fabrics, specifically rib-knitted fabrics with varying repeats, has yielded significant insights. 44 As the number of inactive needles increases, the fabric exhibits higher levels of stress relaxation in both the course and wale directions. Furthermore, the study consistently observed that stress relaxation is more pronounced in the wale direction when compared to the course direction for all fabric structures. Such findings highlight the relationship between knit structure and stress relaxation in weft-knitted fabrics and the importance of its understanding.
The selection of yarns in the knit structure of textile materials plays an essential role in determining their properties. The increasing demand for eco-friendly, sustainable, and recycled textile materials presents significant opportunities for the utilization of natural fibers such as cotton and flax in the textile industry.45–47 These plant-based fibers are highly versatile and have a wide range of applications in the production of textiles. By using these materials, the textile industry can move towards a more sustainable and environment-friendly approach. Flax fiber has many benefits that make it suitable for producing various textile materials. These include its ability to absorb moisture, protect against UV radiation, and have good thermal properties. Flax fiber is also gentle on the skin and does not cause allergies. It has a unique texture that makes it pleasant to handle and exhibits suitable electrostatic properties.48,49 Flax fiber is less elastic, but this disadvantage can be overcome by combining it with other textile materials. 50 Researchers have explored opportunities by blending flax with other fibers to produce yarns with different blend ratios.51,52 This has opened up a promising market for flax fibers in the textile industry, especially in knitting production. Findings indicate that a blend ratio of 80:20 or 70:30 of cotton and flax fibers provides the most favorable results for the spinning process and physical yarn properties.53–57 Therefore, in this investigation, we have chosen to use a blend of 70% cotton and 30% flax that offers the optimal balance of softness, durability, and breathability. Cotton is known for its softness and smooth texture, making it comfortable to wear, while flax fibers offer excellent strength and absorbency. This particular combination of yarn is highly versatile in its application, providing an exceptional balance between functional efficacy and comfort. This fact had a decisive influence on the choice of raw materials for the current study.
This research focused on cotton/flax double weft knitted fabrics produced by alternating two courses: rib set-out and plain and aimed to investigate the effect of rib set-out repeat on fabric performance. As the relaxation of knitted fabric plays an important role in alleviating stresses, enabling the fabric to regain its intended shape and size, the effect of relaxation type (dry and washing) was also studied. Therefore, the main purpose of this research is to cover the gap and to improve our understanding of fabric properties by investigating the effects of rib set-out variants and fabric states on structural characteristics, dimensional stability, and stretch properties. A thorough study of the factors influencing fabric shape and stability is crucial for developing high-quality knitted fabrics and garments. This understanding is important for creating comfort and aesthetic knitwear that meets the consumer’s expectations.
Materials and methods
Materials
This research investigated the properties of the half Milano rib and nine different variants of double weft knitted fabrics (Table 1). These variants were created by alternating the rib set-out course and plain course within the repeat at the height (Rh). The manipulation of the number of active needles (m) and inactive needles (n) on the front bed of the knitting machine was used to achieve different repeat of rib set-out. The number of active (m) and inactive (n) needles on the front needle bed within the interlooping repeat at width (Rb) were ranged from 1 to 3.
Graphical representation and visual illustrations of the knitted fabrics.
Blue color – rib course, gray color – plain course.
The percentage of inactive needles in rib set-out repeat (X) on the front bed of the knitting machine was calculated as follows:
Detailed information about the fabric variants is presented in Table 1. The technical face of the fabric was knitted by needles of the front bed, and as such it is formed by loops of both rib and plain courses. The technical back of the fabric was knitted by needles of the back bed. It is formed by consists of rib loops only and is similar for all fabric’s variants.
Production
All fabrics were produced on a 10-gauge flat-bed knitting machine from a 25 × 2tex × 2 cotton/flax yarn (70% cotton, 30% flax). The cotton/flax yarn was produced using the rotor spinning system. 58 Before knitting, the yarn was waxed with 0.5% of wax. 59 The primary knitting parameters, including the stitch cams position (3.5 mm), yarn tension (10.8 cN), and fabric take-down load (17 cN/wale) remained constant. All stitch cams were set up at the same position.
After knitting, all fabrics were subjected for relaxation in accordance with the conditioning and stress recovery guidelines specified in ISO 139:2005. 60 After dry relaxation within 10 days all fabrics were the subjects for washing in accordance with the domestic washing and drying procedures outlined in ISO 6330:2021 61 using a household fully automatic washing machine with the cotton program. In total, four washing cycles (k = 1,2,3,4) were performed. Many knitwear manufacturers, especially those used flat knitting machines, skip the washing stage, so fabrics after dry relaxation are used as references.
Methods
Determination of dimensional changes in knitted fabrics
The changes in dimensions, covering both the lengthwise and widthwise of the knitted fabrics, were evaluated following four consecutive washing cycles (WR), as detailed in the “Materials” section. The dimensions of the samples were measured after each washing cycle, and the changes were calculated using the methodology outlined in ISO 5077:2007. 62
The lengthwise (DCl) and widthwise (DCw) dimensional changes (“−” shrinkage and “+” expansion) were calculated using the equation:
where “original measurement” refers to the measurement taken before the first washing; “final measurement” refers to the measurement taken after each washing cycle.
The analysis was conducted using the mean of five measurements for each fabric variant.
Determination of structural characteristics of the knitted fabrics
The structural characteristics of the knitted fabrics were measured according to the standard methods for knitted fabrics after a 10-day period of dry relaxation (DR) and four washing cycles (WR). The following standards were used in this study:
• EN 14971:2006
63
– for determining t
• EN 14970:2006
64
– for determining
• The average stitch length (la) in mm was calculated as follows:
where l1 – the stitch length of rib stitch in mm, l2 – the stitch length of plain stitch in mm; N1 and N2 – the number of loops in repeat for rib stitch and plain courses respectively.
• EN 12127:1997 standard
66
– for determining
• ISO 5084:1996 standard
67
– for determining
Determination of stretch properties of the knitted fabrics
The GOST 8847-85 standard test method 68 was used for determining the stretch characteristics of knitted fabrics namely full deformation and its parts as well as their contributions in full. A “rack” relaxometer was used for the “loading–unloading–rest” cycle. The research was carried out with a 6 N load for 60 min followed by unloading and 120 min of resting. The samples of 50 mm width and 200 mm length were used. The initial distance between clamps (L0) was set up 100 mm. The five parallel measurements were done for each fabric both lengthwise and widthwise.
The following equations were used for value calculations:
• full deformation (E):
where L0 – the initial length of the specimen in mm, L1 – the length of the specimen after 60 min of loading in mm.
• elastic deformation (E1):
where L2 – the length of the specimen just after unloading in mm.
• delayed deformation (E2):
where L3 – the length of the specimen after resting in mm.
• residual deformation (E3):
Future analysis is based on the mean values obtained from five measurements conducted on each fabric variant.
The contribution of the components of full deformation was calculated using the mean values of deformations as follows:
• elastic ∆1
• delayed ∆2
residual ∆3
Results and discussion
The dimensional change of the knitted fabrics after four washing cycles
The primary objective of this study was to investigate the impact of different rib set-out on the dimensional stability of the fabrics after washing. Specifically, the analysis focused on effect of the percentage of inactive needles on the front bed of the knitting machine (X). Understanding this behavior of knitted fabrics can potentially lead to significant improvements in their overall quality. The research results of dimensional changes lengthwise (DCl) and widthwise (DCw) of knitted fabrics after each of four washing cycles (k = 1,2,3,4) are presented in Table 2.
The experimental values of the dimensional change (DC) of the knitted fabrics after each of the four washing cycles (k).
The results demonstrate that knitted fabric variants 2–10 experience shrinkage in both lengthwise and widthwise dimensions. This is correlated to the statement highlighted in Knapton et al. 29 that the dimensions uniformly decrease during the relaxation process. However, variant 1, the half Milano rib, experiences lengthwise shrinkage and a fluctuating trend widthwise during the four washing cycles. Dimensional changes lengthwise (DCl) are much higher than widthwise (DCw). The difference in dimensional changes (DC) is attributed to the knitting process, which draws the fabric off lengthwise, leading to needle loop extension. The obtained results show that as was expected first washing has a major impact on the dimensional stability of fabric in both directions. It is consistent with findings for double-weft knitted fabric made from cotton/flax yarn.14,19,21 If fabrics are treated with moisture, there is a greater chance of significant alternations in the size and shape of the loops, as mentioned in the paper. 30 This has to be considered in knitwear manufacturing from cotton/flax yarn or similar. The washing stage should be implemented after knitting before assembling the final product.
The dimensional change (DC) during the washing cycles can be determined by the computational method based on experimental data. 69 This method is based on the determination of constants (a) and (b) in the following equation:
where k – the number of washings cycles; a and b – the constants.
The potential total dimensional change at k→∞ will be equal to the 1/b. The calculated values of (a) and (b) constants as well as potential total dimensional change (1/b) for all fabric variants, are presented in Table 3. The plots of calculated dependencies of lengthwise and widthwise dimensional changes for fabrics with equal active needle in the repeat of rib set-out are presented in Figure 1. Calculated dependencies are matching to experimental data and the value of potential total dimensional change (1/b) can be used for future fabric production.
The calculated values of a and b constants, the potential total dimensional change 1/b for knitted fabrics.

The experimental data (ex) and theoretical (t) dependence of the dimensional change lengthwise (DCl) and widthwise (DCw) on washing cycles (k) for fabrics with an equal percentage of inactive needle (X=50%): (a) – variant 2, (b) – variant 6, and (c) – variant 10.
The interlooping repeat has an insignificant impact on DCl, as shown in Figure 2. The correlation between the percentage of inactive needles (X) and the dimensional changes DCl after the fourth washing cycle is weak. The coefficient of determination (R 2 ) is only 0.40; the average value is 14.8%, ranging between 12.5% and 16.1%. However, the correlation between the percentage of inactive needles (X) and the dimensional changes DCw after the fourth washing cycle is quite high (R 2 =0.80). It can be stated that the rib set-out repeat affects the dimensional changes widthwise (DCw): the shrinkage increases with the increase of the number of inactive needles (X) (Figure 2). This is due to differences in the way the yarn is redistributed between parts of the loops in both directions. The lengthwise dimensional changes in knitted fabrics depend on the redistribution from sinker loops into the loop heads. The widthwise dimensional changes of the knitted fabrics depend on the redistribution of the yarn in the opposite way – from the loop heads to sinker loops.4,69

The dependence of dimensional change lengthwise (DCl) and widthwise (DCw) after the fourth washing cycle (k = 4) on the percentage of inactive needles (X).
A comparison of fabric variants with an equal percentage of inactive needles (variants 2, 6, and 10, X = 50%) shows the similarity in lengthwise shrinkage (DCl) and differences in widthwise shrinkage (DCw) (Table 2, Figure 1). Dimensional changes lengthwise are 15.3–15.8%. Variant 2 with rib set-out 2 × 1 (1 active needle and 1 inactive needle on front needle bed in repeat) has the smallest shrinkage widthwise: 4.5% after the first washing (k = 1) and 5.5% after the fourth washing (k = 4) (Figure 2). Variant 6 with rib set-out 4 × 2 (2 active needles and 2 inactive needles on front needle bed in repeat) has the highest shrinkage: 5.9 % after the first washing (k = 1) and 9.0 % after the fourth washing (k = 4).
The structural characteristics of the knitted fabrics
As outlined in the “Materials” section, the fabrics under investigation are created through the alternating arrangement of two courses: rib set-out and plain. The technical back of all fabrics is formed by extended loops of rib on the back needle bed of the knitting machine. The technical face of half Milano rib (variant 1) is formed by shortened loops of rib and loops of plain stitches on the front needle bed of the knitting machine (Figure 3(a)). The technical face of other fabrics (variants 2–10) has a different number of courses in different wales. If the needle on the front bed was active for the rib course, the formed wale is like variant 1 (half Mialno rib): two courses on the face correspond to one on the back (Table 1, Figure 3). If the needle on the front bed of the knitting machine was inactive during the formation of the rib course, only the wales of plain stitches remain. They are extended as well. It looks like two plain structures along with each other by the back side (“double plain”), thus there is a gap between them. With the increase of the number of inactive needles for the rib course the width Y of such “double plain” span increases (Figure 3(b)–(d).

The visual illustrations of the knitted structures: (a) – variant 1 the half Milano rib, (b) – variants 2 with m = 1 and n = 1, (c) – variants 6 with m = 2 and n = 2, and (d) – variants 10 with m = 3 and n = 3.
Variations in fabric structures influence both the structural parameters and the properties of fabrics. The structural characteristics such as stitch density, stitch length, and thickness of knitted fabric from natural yarn, are greatly dependent on relaxation.2,69 Therefore, in this study, the double-weft knitted cotton/flax fabric was tested after both dry relaxations (within 10 days) (DR) and after four washing cycles (WR). The research results are presented in Tables 4 and 5, respectively.
The structural characteristics of the knitted fabrics after dry relaxation (DR).
The structural characteristics of the knitted fabrics after four washings (WR).
The number of wales per centimeter (WPC) of knitted fabrics
It is important to emphasize that despite variations in the number of courses, the quantity of wales remains consistent for both the technical face and back of all fabrics, denoted as WPC = WPCf = WPCb. The study’s findings highlight the significant influence of both relaxation type and rib set-out repeat on WPC, as presented in Figure 4.

The dependence of the WPC on the percentage of inactive needles in repeat (X) after dry (DR) and fourth washing (WR).
Referring to Tables 4 and 5, the number of wales per centimeter (WPC) for all knitted fabric variants is notably affected by the fabric’s condition and the percentage of inactive needles (X) within the repeat at the width (Rb). This correlation between the number of wales per centimeter (WPC) and the percentage of inactive needles (X) within the repeat (Rb) is graphically presented in Figure 4.
The effect of washing on the number of wales per centimeter (WPC) refers to fabric shrinkage widthwise (DCw). The half Milano rib showed only a slight increase in the WPC after four washing cycles because the DCw was only −1.8%. The WPC for variant 4 fabric (X = 75%) increases from 5.5 to 6.1 loops (by 10%) with 6.8 % shrinkage.
The plots in Figure 4 clarify the effect of rib set-out repeat on the number of wales per centimeter (WPC). The increase in the percentage of inactive needles (X) leads to an increase in the fabric`s density. This is due to differences in the shape and size of loops knitted on the front needle bed as well as different relaxation mechanics of “double plain” and half Milano rib spans. The dependence is more observed after washing because the structure has an equilibrium state.
The number of courses per centimeter (CPC) of knitted fabrics
As mentioned earlier, the studied knitted fabrics display noticeable differences between their technical face and back sides due to differences in the working processes for needles of the front and back needle beds of the knitting machine. This leads to a different number of courses on the technical face (CPCf) and back (CPCb) of the knitted fabric. The research result (Tables 4 and 5) shows that the course number on the technical face (CPCf) surpassed the course number on the technical back (CPCb) following both dry relaxation (DR) and washing cycles (WR). The CPCf is two times higher than CPCb for half Milano rib (variant 1). The difference between CPCf and CPCb for other fabrics (variants 2–10) is less (45–55%) because they have different numbers of courses in different wales on the technical face. Therefore, the analyses were only done for courses per centimeter for technical back (CPCb) (Figure 5).

The dependence of the CPCb on the percentage of inactive needles in repeat (X) after dry (DR) and fourth washing (WR).
It was found that both the relaxation type (dry and washing) and the rib set-out repeat affect the number of courses per centimeter (CPC) similar to the number of wales per centimeter (WPC). The effect of washing on CPCb refers to fabric shrinkage lengthwise (DCl). The CPCb after WR is around 15% higher than after DR completely correlated to the 15% average shrinkage.
The increased percentage of inactive needles (X) leads to increased CPCb. This is due to differences in yarn redistribution between loops of both yarn feeds. In half Milano rib structure there is only redistribution between rib loops knitted on different needle beds. The loops on the back bed became longer, and the loops on the front bed became shorter when the plain course was knitted. All loops of plain course had the same shape and size. In the case of rib set-out, there is a redistribution between the plain loops. The plain loops on inactive needles became longer, and the loops on active needles became shorter when the rib course was knitted. With the increase in the percentage of inactive needles (X), the possibility of yarn redistribution decreases, which leads to a decrease in the size of held loops on both sides and, therefore, an increase in stitch density.
The comparison of the number of courses for the technical back (CPCb) of fabrics with the same percentage of inactive needles (variants 2, 6, and 10, X = 50%) in equilibrium state (WR) shows a remarkable similarity of CPCb = 6.3–6.5 loops/cm.
The stitch length of knitted fabrics
The length of stitches is a crucial aspect of knitted structures, affecting the fundamental characteristics and properties of fabrics. This factor is closely linked to various technological parameters such as stitch type, machine gauge, stitch cam depth, yarn tension, take-down load, and yarn type. As shown in Tables 4 and 5, demonstrates that a consistent stitch length was maintained across all fabric variations due to production under identical conditions. Any slight differences within a 5% margin can be attributed to measurement errors.
The stitch length in the rib course (l1) demonstrates a 10% increase compared to the stitch length in the plain course (l2) for both conditions – after dry relaxation (DR) as depicted in Table 4 and following washing cycles (WR) as shown in Table 5. This difference arises from the way adjacent needle loops are connected. In the case of plain stitches, the adjacent loops are formed on the same needle bed, while rib stitches are knitted on different needle beds (front and back), resulting in longer junctures due to the distance between the beds.
The thickness of knitted fabrics
The thickness (t) of knitted fabrics is influenced by various factors, with the type of stitches and the relaxation process playing crucial roles.27,28 It was found that the thickness of all studied knitted fabric increases by up to 20 % and depends on the interlooping repeat after four washing cycles. When the percentage of inactive needles (X) had increased, the thickness (t) increased as well after both dry relaxation (DR) and washing (WR), as shown in Figure 6. The thickness of variant 4 fabric (X = 75%) is 2.22 mm compared to 1.80 mm for half Milano rib (X = 0) after four washing cycles (WR) when the structure is in an equilibrium state.

The dependence of the thickness t on the percentage of the inactive needles in repeat (X) after dry (DR) and fourth washing (WR).
The weight (GSM) of knitted fabrics
The weight (GSM) of knitted fabrics is influenced by many factors, mainly the interlooping repeat and stitch types, stitch density and stitch length, yarn type, and linear density. For studied knitted fabrics produced at the same technological conditions, interlooping repeat had the most impact on GSM. Figure 7 clearly illustrates that increasing the percentage of inactive needles (X) up to 75% results in a substantial 28.9% increase in the weight (GSM) of knitted fabrics due to the increasing stitch density of both courses and wales per centimeter (Figures 4 and 5).

The dependence of the weight GSM on the percentage of the inactive needles in repeat (X) after the fourth washing (WR).
Determination of stretch properties of the knitted fabrics
The stretchability of the knitted fabrics was assessed both lengthwise and widthwise after undergoing four washing cycles. The calculated values using equations (4–10) of full deformation and its different parts and their corresponding contributions are presented in Tables 6 and 7.
The stretch characteristics lengthwise of the knitted fabrics.
The stretch characteristics widthwise of the knitted fabrics.
It is clear that full deformation widthwise is 2–4 times more than lengthwise (Figure 8).

The full deformation E of knitted fabrics from cotton/flax yarn.
Within lengthwise stretching, the legs of the loop are subject to stress, and get an extension in the stretch direction. Thus, the stretchability of fabric depends on yarn stretching first, and the redistribution of yarn from the loop head and sinker loop into the loop legs secondarily. 69 In this case, when studied fabrics are made from the same cotton/flax yarn with the same stitch length, the fabric stretchability lengthwise is similar and ranges from 18% to 25%.
During widthwise stretching, the loop head and sinker loop are subjected to stress and are displaced in the stretching direction, followed by the redistribution of yarn from the loop’s legs into them. This is the primary stretching mechanic for the plain structure. In the case of the rib structure, first the face and reverse loops are moved in the stretching direction, followed by the widening of the loop. Thus, the stretchability of the studied fabric depends on the interlooping repeat, namely of “double plain” span size, not only because of the differences in stretching mechanics but also the possible friction between two plain structures. There is a reduction in full deformation widthwise with the increase in the number of inactive needles (X) from 1 to 3 (Figure 8).
The full deformation contributions lengthwise (a) and widthwise (b) are presented in Figure 9.

The full deformation contributions lengthwise (a) and widthwise (b).
Elastic deformation (E1) arises from stress realignment in the loops and changes in their shape just after fabric unloading. Research results show that elastic deformation has the greatest contribution (Δ1) to full deformation. The values are 0.78–0.92 for lengthwise stretching (Figure 9(a)) and 0.62–0.73 for widthwise stretching (Figure 9(b)). It can be stated that studied double-knitted fabrics are less stable widthwise and this property has to be taken into account in application areas.
The presence of delayed deformation (E2) results in gradual changes in the dimensions and shape of the fabric during use. The contribution of delayed deformation in the full deformation (Δ2) for all fabric variants of the knitted fabrics shows minor variations, ranging from 0.08 to 0.11 lengthwise and from 0.10 to 0.14 widthwise (Table 5). This trend aligns with the findings of a previous study. 43
The residual deformation affects the total fabric`s performance and its quality. The residual deformation of studied fabrics (Figure 10) lengthwise is relatively small, the maximum value just 2.5% (Table 5). At the same time, the residual deformation widthwise is quite high, and for some fabric variants (5 and 9) the value reaches over 15%. This can be a problem when using such a structure under a load over 6 N.

The residual deformation E3 of knitted fabrics from cotton/flax yarn.
The comparative analysis of fabric variants with an equal percentage of inactive needles (variants 2, 6, and 10, X = 50%) showed similarities in all types of deformations (E, E1, E2, and E3) and their ratios (Δ1, Δ2, and Δ3) at widthwise stretching.
Conclusion
This study makes contributions to understanding structural, dimensional, and stretch properties of double weft knitted fabrics made from a 25 × 2tex × 2 cotton/flax yarn formed by alternation of two courses: rib set-out and plain. The research focused on investigating the effect of repeat rib set-out by varying the number of active (m) and inactive needles (n) on the front bed of the 10-gauge flat-bed knitting machine, ranging from 1 to 3. Valuable insights were gained into how interlooping repeat, namely the percentage of inactive needles on the front bed of the knitting machine (X), influenced the fabric’s dimensional stability during four washing cycles, their structural characteristics after dry relaxation (DR) and washing (WR), as well as stretch properties.
The research results show the following:
The first washing has a major impact on the dimensional stability of cotton/flax fabric. The washing stage should be implemented after knitting before assembling the final product in the knitwear manufacturing on flat knitting machine.
The dimensional changes of studied fabrics lengthwise (DCl) are much higher than widthwise (DCw) and mainly occurred after the first washing cycle. The mean value lengthwise is 14.6, and it was not affected by the interlooping repeat.
The dimensional changes of studied fabrics widthwise (DCw) were increased by 3 % on average within four washing cycles. The potential total dimensional change (1/b) was calculated, and the value ranged from 0.3% to −11.7%. The dimensional changes increase (DC) with the increase in the number of inactive needles (X) in the rib set-out repeat (Rb). The regression dependence equation was found to calculate the value with high accuracy.
The rib set-out repeat affects structural characteristics, namely the number of wales and courses per centimeter, thickness, and weight of fabrics. With the increase of the number of inactive needles (X) in rib set-out repeat (Rb) the double-knitted fabrics became denser, thicker, and heavier. The appropriate regression dependence equations were found to calculate the respective values with high accuracy.
The full lengthwise deformation of studied fabrics ranges from 18 to 25% and was not influenced by the interlooping repeat. The elastic deformation is the main part in this direction, with a contribution of over 0.8. The maximum residual deformation is 2.5%.
The full widthwise deformation (E) of studied fabrics is up to four times more than that of the lengthwise, and it depends on the interlooping repeat. The contribution of elastic deformation ranges from 0.62 to 0.73 which limits the fabric’s application. The residual deformation widthwise is quite high and should be taken into account for future usage.
The fabrics with the same percentage (X = 50%) of inactive needles on the front bed of the knitting machine showed only insignificant differences in properties.
In summary, this analysis demonstrates the significant effect of rib set-out repeats on the properties of knitted fabrics. The findings shed light on dimensional changes, fabric weight, and deformations, providing valuable insights for designers and manufacturers to optimize fabric performance for specific applications. The findings contribute to the optimization of knitted fabric properties, improving their dimensional stability and stretch performance, which can be crucial for various application areas.
Highlights
• Ten variants of double weft knitted cotton/flax fabrics were developed by alternation of two courses: rib set out and single jersey in order to extend the structures variety and future knits diversity.
• The effect of rib set-out repeat on the dimensional, structural and stretch properties of knitted fabric was investigated.
• The theoretical dependencies of dimensional changes on washing cycles were established on the experimental results and the potential total dimensional change was calculated.
• The equations were established to predict with high accuracy the fabric’s structural characteristics (the number of wales and courses per centimeter, thickness and weight) in case of changing rib set-outs.
Footnotes
Acknowledgements
The authors express their gratitude to the Philipp Schwartz Initiative of Alexander von Humboldt Stiftung for providing a fellowship F-007470-533-009-3580000 to continue research at Dresden University of Technology
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
