Experimental analysis of the optimal selection of materials for car seat covers manufacture

The purpose of this experimental analysis is to select the most optimal basic materials used in car seat covers manufacture. According to our statistical research, we sampled three basic materials more commonly used in the manufacture of car seat covers:

1)          natural leather (NL),

2)          artificial leather (AL),

3)          flock (F).

Woven elastic tape (WET) was chosen as an auxiliary material according to the State Standard (GOST) 17–284–73.

The use of the elastic tapes is reasonable to provide the most optimal shape stability parameters and accurate tight fitting of car seat covers in such places as headrest and upper back. These tapes should be topstitched beneath the basic material so that, later, the cover being put on headrests, the tape is stretched and taken a complex shape of headrest and curved parts of the back.

To determine the technology of combinatorial effectiveness of each of the basic materials with an auxiliary one tests of breaking strength were carried out. The strength tests were aimed at the determination of thread seams elongation as well as fabric threads slippage in the joining seams. We carried out the tests which meet the State Standard (GOST) 28073–89 «Sewing Articles. Methods for the Determination of Breaking Load, Elongation of Thread Seams, Slippage of Fabric Threads in Seams. ".

What is Elongation? — The elongation of a yarn has an influence on the manufacturing process and the products made. It provides an indication of the likely stretch behavior of garment areas such as knees, elbows, or other points of stress. It also provides design criteria for stretch behavior of yarns or cords used as reinforcement for items such as plastic products, hose, and tires.

What is Breaking Strength? — The breaking strength of a yarn influences the breaking strength of fabrics made from the yarn, although the breaking strength of a fabric also depends on its construction and may be affected by manufacturing operations.

The breaking tenacity, calculated from the breaking force and the linear density, and the elongation are fundamental properties that are widely used to establish limitations on yarn processing or conversion and on their end-use applications. Initial modulus is a measure of the resistance of the yarn to extension at forces below the yield point. The chord modulus is used to estimate the resistance to imposed strain. The breaking toughness is a measure of the work necessary to break the yarn.

The single-strand method gives a more accurate measure of breaking force present in the material than does the skein method and uses less material. The skein-breaking force is always lower than the sum of the breaking forces of the same number of ends broken individually.

Most yarns can be tested by applicability test method. Some modification of clamping techniques may be necessary for a given yarn depending upon its structure and composition. To prevent slippage in the clamps or damage as a result of being gripped in the clamps, special clamping adaptations may be necessary with high modulus yarns made from fibers such as glass or extended chain polyolefin. Specimen clamping may be modified as required at the discretion of the individual laboratory providing a representative force-elongation curve is obtained. In any event, the procedure described in this test method for obtaining tensile properties must be maintained.

We used Universal tensile testing machine ER 5074–3 with the maximum limited force 3 kN and constant speed of the lower clamp descent as the experimental equipment for the determination of breaking strength and thread seams elongation.

A single-row strop seam was selected to join the samples. Its parameters meet State Standard (GOST) 16964–71 «Seams for Fabric Covers. Design and Dimensions».

The type, model, number, basic sizes of the needle as well as the shape of the needlepoint for connecting basic and auxiliary materials were selected as meeting State Standard (GOST) 22249–82 «Needles for Sewing Machines. Types and Basic Dimensions».

To join the samples we selected threads which conform to the State Standard (GOST) 30226–93 «Threads for Shoes. Cotton and Synthetic Threads».

Five samples were prepared for each type of the combination of basic and auxiliary material as meeting the State Standard (GOST) 28073–89 «Sewing Articles». (Fig. 1).

Fig. 1. Dimensions of Elementary Tested Samples, in mm

To perform the test we installed 100mm clamping length on our tensile testing machine. We inserted the short part of the sample (WET) into the upper clamp, and the long part of the sample into the lower clamp (Fig.2).

The thread seam was equidistant from upper and lower clamps of the tensile testing machine. The strength tests particulars and extensibility at break were recorded in accordance with the scales of the machine.

The traveling speed of the lower clamp was constant and equal to 100mm/min.

The moment of the injury of thread seam or sample material was fixed according to device stop or the sound of torn thread.

Fig. 2. Replacement of the Samples in Tensile Testing Machine Clamps

a) AL + WET b) NL + WET c) Flock + WET

The results of the fulfilled measurements of tensile strength and elongation of the samples are shown at the Table 1. We take average arithmetic value of 5 primary test results, rounded up to 1, 0H, as the actual tensile strength.

Table 1

The Indicators of Tensile Strength and Elongation

Graphical results of obtained strength tests are shown at fig 3.

Fig. 3. Graphical Results of Strength Tests

We calculated in percentage the value of thread seam elongation for all combinations using the formula:             l₁=l*100/A,                                         

where l is length change, mm;

A is clamping length, mm.

Comparative diagram of the results of breaking strength and elongation is shown at figure 4.

Fig. 4 — Diagram of the Laboratory Tests Results

According to laboratory tests results, the basic material injury occurs lengthwise the connecting seam line in the samples of AL + WET combination, but thread seam itself remains undamaged. Similar nature of the injury is observed in flock + WET combination.

But, in this case, the injury of the material happened in two cases out of five. Injury of the material did not occur in any of five cases for NL + WET combination.

The results of the experimental tests showed that «natural leather + elastic woven tape» composition should be considered the best one for the strength and shape stability of fabric for automobile seat covers.

References:

1.      GOST 28073–1989. Sewing Articles. Test methods of Breaking Force, Thread Seams Elongation, Slippage of Fabric Threads in the Seams [text]. — Enter. 1990–01–07. — Moscow: Publishing House of Standards, 1989. — pg. 10.

2.      GOST 16964–1971. Seams for Fabric Covers. Design and Dimensions [text]. — Enter. 1972–01–07. — Moscow: Publishing House of Standards, 1989. — pg. 8.

3.      GOST 22249–1982. Needles for Sewing Machines. Types and Basic Dimensions [text]. — Enter. 1973–01–07. — Moscow: Publishing House of Standards, 1989. –pg. 20.

4.      GOST 30226–1993. Threads for Shoes. Cotton and Synthetic Threads. [text]. — Enter. 1996–01–01. — Moscow: Publishing House of Standards, 1989. — pg. 19.