Seam Performance of the Inseam of a Military Trouser in Relation to Garment Fit

Transcription

1 Textiles and Light Industrial Science and Technology (TLIST) Volume 3, 2014 DOI: /tlist Seam Performance of the Inseam of a Military Trouser in Relation to Garment Fit A. Mukhopadhyay, A. Chatterjee and Taranjot Ahuja Department of Textile Technology, National Institute of Technology, Jalandhar (India) arunangshu@nitj.ac.in Received 17 February, 2014; Revised 3 March, 2014; Accepted 7 May, 2014; Published 25 June, Science and Engineering Publishing Company Abstract Tensile properties of fabrics and seams are often theoretically and experimentally investigated for principal directions but in actual garments the stress is applied at the non-principal directions which are defined according to the fit of the garment. This study attempts to find out the effect of change of garment fit on the seam qualities i.e. seam breaking strength and seam breaking elongation with reference to the angle of cut in the garment. The seam at the inner leg of a male military trouser was analysed as it is most prone to stress. The trouser was analysed for two fits, viz. a viz. regular fit and slim fit, and the results were compared with a straight cut fabric. It was observed that the breaking strength and elongation were maximum in the case of a slim fit followed by regular fit and it is lowest for a straight cut. It implies that test standard (based on straight cut seam) does not provide real seam strength in practice. It was found that the breaking strength and elongation were greater for lap felled than plain seam. In all the above cases, the twill fabric showed higher breaking strength and elongation than plain fabric. Keywords Garment Fit; Angle of Cut; Seam Breaking Strength; Seam Breaking Elongation; Military Trouser; Trouser Pattern Introduction There are vast range of requirements for military textiles (Wilusz, 2008), mechanical strength of textile fabric and seam is one of them. The primary function of a seam is to provide uniform stress transfer from one piece of fabric to another, thus preserving the overall integrity of the fabric assembly. The performance parameters of seams include strength, elasticity, durability, security and appearance. However, priority given to any of the characteristics will vary, depending on the end-use of the seamed product. For example, severe applications like military combat forces, very high seam strengths are required. During stress transfer, anisotropic behaviour of textile material with and without seam can play a major role in successful performance of fabric assembly. Due to the above, the impact of the direction of loading on tensile properties of the woven fabric can be enormous and is frequently examined (Hu, 2004). For arbitrary load direction, the values of tensile properties change and fabric deformation becomes more complex, often incorporating fabric shear and bend deformation. Although weave anisotropy is well known, tensile properties are usually theoretically and experimentally investigated for principal directions; the main reason is probably complexity of deformation and stress distribution when the load is put at non-principal direction. In actual garments the stress however is applied at the non-principal directions which are defined according to the fit of the garment. Basic understanding about the strategies to improve seam performance through judicious selection of material, setting of operating parameters at right levels and also by improving the design of sewing machine is available in the literature (Mukhopadhyay and Midha, 2013). In one of the previous studies it was found that the stances that caused the maximum stress in garments were crossing the arms in front with the hands on the opposite shoulders for the shirt and overall upper back and sitting with the knees and hips fully bent and the legs spread apart or squatting for the buttocks, crotch, and inner leg regions of the trousers and the overalls (Crow and Dewar, 1986). It was also seen that in the case of trouser the maximum stress was on the inner seam or the crotch area and the maximum skin strain was also observed in the crotch area to the extent of 45%. This explains the maximum chances of seam failure in this area. The problem is more acute in the case of military personnel as they are required to move, live, survive and fight in a hostile 29

2 Textiles and Light Industrial Science and Technology (TLIST) Volume 3, 2014 environment. In the case of the military garment the stress concentration is maximum at the seat seam of the trouser which calls for high performance requirement. The failure of the seam makes a trouser unsuitable even though the fabric may be in a good condition. Due to the above, the present study hasconcentrated on performance of inseam of military trouser. Crowther (1985) studied the comfort and fit of 100% cotton denim Jeans, which were characterized as body hugging or tight fitting and said that there was a possibility of body malfunctioning in the long run. Other medical reports have also suggested that tight clothing could act as effective tourniquet when the body assumes sitting and crouching position, leading to thrombosis. He concluded that the inherent property of fabric construction may be utilized to reduce skin strain and enhance body contouring. A military trouser not only needs to have the appropriate seam strength and elongation but also an appropriate fit, as loose fit will hamper their activity and a tight fit will restrict their movement. (a) Warp direction for trouser front (b) FIGURE 1 (A) FABRIC CUTTING PREPARATION, (B) YARN ORIENTATION FOR SAMPLES TESTED FOR ANGLED SEAMS Although there are much work related to seam tensile characteristics (Mukhopadhyay and Midha, 2013), but the work pertinent to impact of seam angle in relation to fabric is very limited. The study is more relevant in deciding the performance of seam, as in reality different garment fits involve cutting the fabric at various angles and then stitching it. In a study based on angled seams with respect to warp direction, maximum seam strength can be observed for the fabric sewn at bias direction to that of warp thread (Figure 1) (Citoglu, and Kaya, 2011). However, in the case of an inseam of a trouser, seam configuration and alignment of seam line is different with respect to direction of warp threads (Figure 2). Since, there is no information available on the performance of seam tested at such a configuration; it is therefore important to study the aforesaid aspect. Warp direction for trouser back Seam line Inseam FIGURE 2 YARN ORIENTATIONS AT THE INSEAM OF A TROUSER 30

3 Textiles and Light Industrial Science and Technology (TLIST) Volume 3, In this study therefore, it has been attempted to find out the influence of garment fits on the behavior of seam at the inner leg area of a military trouser. It is noted that for the Regular and Slim Fit Male Trousers, the actual angle of cut lies between 0 to 15 in relation to the angle of warp. The seam has been analysed with respect to the breaking strength and breaking elongation. The effect of changing the seam type and fabric type on the above was also analysed. A comparison was also made with a straight cut fabric, i.e. sample cut at 0 in relation to the angle of warp, in all cases. It may be added that the test standard is based on straight cut seam which may not provide real seam strength in practice. Experimental Pattern Making and Sample Preparation Since the inner seam of a trouser was to be analysed, initially patterns were developed for the front and 5 0 back of a regular fit and slim fit trouser. The angles at the inseam for both the fits were observed. To make the test sample an exact replicate of the garment, the templates for fabric cutting were made in such a way that the back of the trouser was considered to be above the seam line and the front was considered to be below the seam line. The angle of cut for a regular fit trouser was 5 for the front panel and 8 for the back panel (Figure 3). Similarly for a slim fit trouser the angle of cut was 8 for the front panel and 14 for the back panel (Figure 4). Figure 5 shows the back and front of a trouser cut at 0 i.e. parallel to the warp for straight cut. The sample size for testing while following ASTM D1683/D1683M-11a) Standard has been shown in Figure 6. The template was made in such a way that the back of the trouser was considered to be above the seam line and the front was considered to be below the seam line. For the aforesaid purpose, the length of back and front template was 10 and 4 respectively. 8 0 (a) Seam line (1.3 cm /0.5" seam allowance) 25.4 cm (10") 10.2 cm (4") 10.2 cm (4") Warp line FIGURE 3 A - PATTERN FOR FRONT AND BACK FOR A REGULAR FIT TROUSER, B - TEMPLATE FOR SAMPLE PREPARATION (b) 31

4 Textiles and Light Industrial Science and Technology (TLIST) Volume 3, (a) (b) FIGURE 4 A- PATTERN FOR FRONT AND BACK FOR A SLIM FIT TROUSER, B-TEMPLATE FOR SAMPLE PREPARATION FIGURE 5 BACK AND FRONT OF A TROUSER CUT AT 0 I.E. PARALLEL TO THE WARP FOR STRAIGHT CUT Specimen used for fabric break 150 mm (6 in) Clamping position for fabric specimen Specimen used for seam break 200 mm (8 in) 80 mm Clamping position for seamed specimen 100 mm (4 in) FIGURE 6 DIMENSIONS FOR THE SEAMED SPECIMEN REMOVED FROM MANUFACTURED ITEM 32

5 Textiles and Light Industrial Science and Technology (TLIST) Volume 3, (a) (b) FIGURE 7 (A) LAP FELLED SEAM AND (B) PLAIN SEAM It may be noted that for the measurement of unseamed fabric, fabric portion corresponding to back template was used. The samples were stitched on a single needle lock stitch machine (SNLS-Juki DDL ), with a stitch density of 5 stitches per cm and a seam allowance of 1.3 cm (0.5 inches). Two types of seams i.e. plain and lap felled seams were used on two different military trouser fabrics (Figure 7). The sewing thread used was 100% polyester, 40 tex core spun yarn. The particulars of the military fabric and the sewing thread used for sample preparation are shown in Table 1 and Table 2. Weave 2/1 Twill TABLE 1 CHARACTERISTICS OF THE MILITARY FABRICS USED Fabric weight (gsm) 195 Plain 208 Warp Yarn 20 s Air Vortex Yarn (80% Cotton 20% Polyester) 20 s Cotton Open End Yarn Weft Yarn 20 s Air Vortex Yarn (80% Cotton 20% Polyester) 16 s Cotton Open End Yarn Ends per cm / Picks per cm 244/ /142 TABLE 2 PHYSICAL CHARACTERISTICS OF THE SEWING THREAD Fineness (tex) 40 Spinning Method Core spun Characteristics of the sewing thread Tenacity (cn) Fibre Type 100% Polyester Breaking Elongation (%) Initial modulus (cn/tex) 21.24% TABLE 3 LAYOUT OF THE EXPERIMENT IN STANDARD ORDER Fabric type Fit Type Seam Type Plain Straight Cut Plain Plain Regular Plain Plain Slim Plain Plain Straight Cut Lap Felled Plain Regular Lap Felled Plain Slim Lap Felled Twill Straight Cut Plain Twill Regular Plain Twill Slim Plain Twill Straight Cut Lap Felled Twill Regular Lap Felled Twill Slim Lap Felled TABLE 4 READINGS FOR BREAKING STRENGTH AND ELONGATION FOR THE SETS DESCRIBED Sl. No. Fabric type Fit Seam Type 1 Plain Straight Cut Plain 2 Plain Regular Plain 3 Plain Slim Plain 4 Plain Straight Cut Lap Felled 5 Plain Regular Lap Felled 6 Plain Slim Lap Felled 7 Twill Straight Cut Plain 8 Twill Regular Plain 9 Twill Slim Plain 10 Twill Straight Cut Lap Felled 11 Twill Regular Lap Felled 12 Twill Slim Lap Felled Mean breaking strength, N (SD) (9.97) (9.95) (6.81) (9.11) (9.87) (4.34) (12.83) (5.49) (7.21) (10.61) (11.13) (10) Unseamed Mean Elongation, mm (SD) (0.95) (0.76) (1.87) (0.78) (0.82) (1.22) (0.43) (0.36) (1.22) (0.54) (0.52) (1.48) Elongation % Mean breaking strength, N (SD) (9.36) (8.23) (8.63) (8.51) (4.49) (14.4) (7.62) (6.85) (7.94) (7.2) (8.27) (10.73) Seamed Mean Elongation mm (SD) (0.59) (0.96) (0.88) (0.61) (0.79) (0.72) (1.04) (0.83) (0.9) (0.45) (0.71) 25.8 (0.68) Elongation %

6 Textiles and Light Industrial Science and Technology (TLIST) Volume 3, 2014 Methods Breaking strength and breaking elongation of fabric were measured using Titan - Universal Strength Tester Model 910 by James H. Heal & Co. Ltd. A layout of the experiment is shown in Table 3. For each case 15 samples were tested. Results and Discussion Based on the readings obtained for the various sets described in Table 3, an analysis is made as to how the angle of cut or the fit is affecting the values obtained for breaking strength and breaking elongation for both seamed and unseamed fabric. The readings are tabulated in Table 4. Effect of Fit (type of cut) on the Breaking Strength of an Unseamed Fabric It is known that back of the trouser is primarily exposed to high level of stress, and the direction of stress could be different from principle direction. Since unseamed fabric is cut for the regular and slim fit (8 and 14 respectively), therefore comparison between 0, 8 and 14 is made based on the sample preparation as shown in Figure 6. It may be noted that the above angle is with respect to perpendicular direction to that of direction of stress during testing. As can be seen from Figure 8, the breaking strength for plain fabric is lowest at 14, higher at 8 and highest at 0. However for twill fabric the breaking strength is higher when the angles of cut is changed from 0 to 8 and lower as the angle of cut is changed from 8 to 14. In a physical model proposed by Tsui et al. (1984), it was assumed that the strength of the sample was dependent upon the number of yarns gripped at the jaw that transferred load either through direct load transfer (yarns gripped at both ends) or through indirect load transfer (yarns gripped at one end ). In the case of plain fabric, decrease in breaking strength with increase in angle of cut may be due to predominant effect of decreased number of yarns gripped at both the jaws. However in the case of twill, the initial increase is probably due to indirect load transfer by the yarns influenced by grouping of the yarns in the twill weave. It could also be due to the twill direction and other factors that need to be explored further. In all cases, the strength of twill fabric is higher than plain fabric in spite of possessing slightly lower mass per unit area in the former case. Effect of Fit (type of cut) on the Breaking Strength of a Seamed Fabric For the seamed fabric, the breaking strength comparison was done with the breaking strength of an unseamed fabric cut at 0. The breaking strength is observed to be maximum for slim fit. This trend was observed for both the fabrics and seam types. A probable reason for the increase in strength from straight cut to regular fit and to slim fit could be due to a very unusual yarn position. The yarns above and below the seam line are in opposite directions and at different angles. For the regular fit, the angle above the seam line is 8 and below the seam line is 5 whereas for the slim fit the angle above the seam line is 14 and below the seam line is 8. This particular orientation may be contributing to the increase in strength. FIGURE 9 BREAKING STRENGTH FOR THE PLAIN AND TWILL FABRIC USING THE TWO DIFFERENT SEAM TYPES FOR THE THREE DIFFERENT FITS FIGURE 8 BREAKING STRENGTH OF AN UNSEAMED FABRIC, CUT AT DIFFERENT ANGLES FOR TWILL AND PLAIN FABRIC It can also be seen from Figure 9 that the breaking strength using a lap felled seam is always higher in comparison with a plain seam. This is because the number of fabric layers being stitched together in the lap felled seam is more than that of layers in the plain seam which contributes to greater thread and fabric interaction which in turn leads to the higher seam strength in lap felled seam. Also in the lap felled seam, there are two stitch lines as against one in plain seam; therefore the load required to break lap felled seam is 34

7 Textiles and Light Industrial Science and Technology (TLIST) Volume 3, expected to be higher (Figure 7). It is further observed that the impact of lap felled seam is much greater in twill fabric. Looking at the strength of unseamed fabric, it appears that strength realization is quite high in case of lap felled seam. shows a greater breaking elongation in comparison to a lap felled seam. This is because the lap felled seam provides much better binding and does not allow enough Elongation. Effect of Fit (type of cut) on the Breaking Elongation of an Unseamed Fabric It can be seen from Figure 10 that the breaking elongation for unseamed fabric is higher as the angle of cut changed from 0 to 8, and 8 to 14 for both the fabrics. Similar trend is also observed in case of breaking strength of material. This can be explained by the fact that as the angle increases (0 to 14 ), the no. of yarns in the sample that are held only at one jaw will increase thereby help the yarns to elongate to a higher extent resulting in a higher breaking elongation. The higher breaking elongation in twill fabric is due to the reason that in twill fabric there are more floated yarns as compared to plain thus decreasing the binding force at the crossing over yarns resulting in greater breaking elongation. It may be added that the role of twill angle is also important while considering stress-strain behavior of material in different direction. FIGURE 11 BREAKING ELONGATION FOR THE PLAIN AND TWILL FABRIC USING THE TWO DIFFERENT SEAM TYPES FOR THE THREE DIFFERENT FITS Conclusions In the case of seamed fabric, the breaking strength and elongation are progressively higher from straight cut to regular fit, and regular fit to slim fit. It implies that test standard (based on straight cut seam) does not provide real seam strength in practice. Additionally it is observed that the breaking strength and elongation is greater for lap felled than plain seam. In all the above cases, the twill fabric shows higher breaking strength and elongation than plain fabric. With respect to garment fit, it has been observed that a slim fit trouser will show better performance at the inseam in comparison to a regular fit trouser. Further using a twill fabric with a lap felled seam will give better results. The work thus provides the direction of making seam for improved performance of the inseam of a military trouser. It also highlights the lacuna in predicting seam strength following test standard. FIGURE 10 BREAKING ELONGATION FOR UNSEAMED FABRIC Effect of Fit (type of cut) on the Breaking Elongation of a Seamed Fabric Figure 11 shows that the breaking elongation of seamed fabric is greater than unseamed fabric and in case of seamed fabric it is maximum for slim fit fabric. This trend is observed for both fabrics and seams and their combinations. The reason behind higher breaking elongation in seamed fabric can be explained as follows. In the case seamed fabric, the yarns are held in the seam thread in between jaws, allowing easier movement of threads. It can also be seen from Figure 11 that for both twill and plain fabric, the Plain seam REFERENCES Citoglu, F, Kaya G, (2011) The effects of different sewing threads and stitch density on seam resistance at different angles, Marmara University, Department of Textile Studies, İstanbul, Turkey, accessed on Crow R. M. and Dewar M. M. (1986) Stresses in clothing as related to seam strength, Text. Res. J., 56, Crowther E. M. (1985) Comfort and fit in 100% cotton-denim jeans, J. Text. Inst., 76, Hu J. (2004) Structure and mechanics of woven fabrics, 35

8 Textiles and Light Industrial Science and Technology (TLIST) Volume 3, 2014 Cambridge, Woodhead Publishing Ltd. Mukhopadhyay A and Midha V (2013) Factors that affect sewn seam performance in Joining textiles: principles and applications, Eds. I Jones and G Stylios, Woodhead Publishing Limited, Cambridge, ISBN Tsui, W.C., Burtonwood, B., Burnip, M.S. and Estekhrian, H.V.A., (1984) Aspects of seam strength prediction - Part 1, Journal of Textile Institute, 75 (6), Wilusz, E., (2008) Military Textiles, Woodhead Publishing Limited, Cambridge, ISBN