Fabric Flex

Grouping

Designers work in pairs (groups of 2).

Let’s get started!

1. Show the PowerPoint.

2. Each pair of young designers should have four 4” x 10” fabric strips. Have them identify the four fabrics as: woven (plain weave), T-shirt jersey knit, dancewear knit, and non-woven (Tyvek®).
3. Have young designers measure the un-stretched length of their first fabric by laying the fabric flat on a table. Have one partner hold the fabric flat while the other uses the measuring stick to read the length and record it on the handout as Initial Length (It should be 10 inches).
   

   Tip: You may want to instruct Young Designers to measure to the nearest ¼ of an inch and to express the result in decimal format for easier calculations, e.g. 11.25 inches.

4. Now have the young designers hold one end of the fabric in place while the partner stretches the fabric as far as possible. Record this as Stretched Length.
5. Let go of one end of the fabric and observe how the fabric behaves with the stress removed. Record on the handout whether it returns completely to its original state and whether it returns right away or slowly.
6. Repeat steps 2-4 measurements with each of the other three fabric strips.
7. Have the young designers calculate Percent Elongation as:

Stretched length – Initial length  x 100 = % Elongation

                Initial length…………………………………………….

VOCABULARY

Elongation: the amount a stressed fabric is extended, expressed as a percentage of the original length.

Discussion

1. ASK: Which fabric elongated least? Why do you think this fabric did not elongate? Would this fabric be a good choice for athletic apparel?
   • ANSWER: The response should be the non-woven. Fabric structure affects fabric elongation. A non-woven fabric structure locks the fibers in place with heat, glue, or tangling. There is no room for fiber movement in this structure. A rigid fabric does not conform to the body easily and can make movement more difficult.
2. ASK: Which fabric elongated the most? Why do you think this fabric elongated so much? Did you notice how this fabric snapped back to its original shape? How does this quick recovery make this fabric ideal for dancewear?
   • ANSWER: The answer should be the dancewear fabric. This fabricelongates very easily for two reasons: First, it is a knit, and the loops inknit fabrics flatten and stretch when pulled. Second, this fabric contains a fiber called spandex.
     

     VOCABULARY

     Recovery: Recovery is the ability of a material to return to its original state when a stress is removed.

     Spandex: Spandex is a manufactured fiber made of a combination of flexible and rigid segments of a polymer* called polyurethane. Spandex will stretch up to seven times in length and return to its original measurement! Clothing labels often list elastane, the international name for spandex, or LYCRA®, a prominent brand of spandex.

3. ASK: How did the recovery of the T-shirt knit compare to that of the dancewear fabric?
   • ANSWER: The T-shirt knit should have stretched easily, but not as much as the dancewear fabric, and it should have recovered slowly. Fabrics that do not recover well create baggy knees in pants.
   • ANSWER: The right angles of a woven fabric align yarns next to one another with little room for movement. A tightly woven fabric will not stretch easily in either warp or weft direction (unless the yarns themselves are stretchy), but will stretch in the bias direction (at a diagonal to the warp and weft).

Take it Further

1. Cut woven fabric in warp, weft, and bias directions. Compare elongation and recovery.
2. Cut strips of T-shirt jersey knit with the courses in the lengthwise and crosswise direction. Compare the elongation.  Jersey stretches much more in the course direction than in the wale direction.  It is important for a designer to orient a fabric correctly in a garment to make use of elongation properties.
   

   VOCABULARY

   Warp: Warp is the lengthwise direction of a woven fabric.  Warp yarns are threaded first onto a loom to give structure to a fabric.

   Weft: Weft is the crosswise direction of a fabric.  Weft yarns do not need to be as strong as warp yarns, and sometimes have a little bit of stretch.

   Bias: Bias is the diagonal direction of a woven fabric.  Warp and weft yarns are both stressed when fabric is pulled in the bias direction, so they will move out of place and the fabric will elongate. 

   Neckties are always cut “on the bias” so that they can curve around the neck easily with a little stretch. 

   Course: Courses are the horizontal loops across the width of jersey knit, seen easily on the fabric back.

   Wale:  The fine vertical ribs in a jersey fabric seen on the right side of the fabric.

3. Compare athletic mesh to a T-shirt knit. T-shirt knit is a weft knit  Athletic mesh is a warp knit, and will not stretch unless it contains spandex yarn.
   

   VOCABULARY

   Weft knit: one yarn traverses back and forth adding loops in each row.

   Warp knit: many yarns are linked together as they move vertically simultaneously.

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