Tensile Strength

National Institute of Fashion Technology, Bangalore

TENSILE STRENGTH / BREAKING STRENGTH

National Institute of Fashion Technology, Bangalore

Tensile Strength (Breaking Strength)

PURPOSE AND SCOPE: Most of the textile raw materials, the property that is of prime importance, to determine their suitability for any particular application, is its tensile strength and elongation. It is therefore of utmost importance to determine these characteristics accurately. To determine the breaking strength of a woven, non-woven or coated fabric using the grab Method, raveled method and to determine the seam strength and seam slippage of fabric. Strength of a fabric is generally considered the most obvious indicator of the service life of a fabric. Also the strength of fabric indicates its ability to resist mechanical damage due to stress of normal wear and refurbishing.

PRINCIPLE: The instrument is works on the principle of Constant rate of Elongation (CRE) A continually increasing load is applied lengthwise or widthwise to the specimen, and the test is carried to fabric rupture. Values for the breaking load of the test specimen are obtained from machine scales, and digital indicator. Equipment is ergonomically designed equipment, which is based on the Constant rate of Elongation (CRE) principle. The sample is held between two jaws, the lower one is stationery jaw while other upper jaw is made to move at a preset speed with the help of geared motor and lead screw arrangement. The load is extended on the movable jaw is sensed by a sensitive sensor connected with load cell which directly indicates the load in digital form in Kilo gram Force (Kg.F)

National Institute of Fashion Technology, Bangalore

TECHNICAL DETAILS OF TENSILE TESTING INSTRUMENT

Capacity of the Tester

: 0 - 250 Kg.

Sensitivity

:100 Gms.

Speed of Machine

: 0 to 375 mm (Can be set by fine speed Regulator)

Minimum jaw separation

: 25 mm

Maximum jaw separation

: 450 mm

Motor

: HP, controlled by fine

Load measurement

: Digital display indicates the max. Load exerted on the load cell during the test with peak value & zero setting switch.

Elongation Measurement

: Digital Display Indicates the continues elongation in Millimeter.

Electric Controls

: By Rotary switch’s Controls load & unload movement and also stopping with the help of a frequency drive.

Power Supply

: 230 + 10 % volts AC, Single Phase, 50/60 Hz

Overload Protection

: Micro switches for over-travel protection.

Dimensions

: 700(L), 390(W), 1650(H) mm

Selecting the speed of the machine

National Institute of Fashion Technology, Bangalore The speed is selected by changing the belt on the groove of the pulleys. There are two set of pulleys. 300mm / Minute - Grab Test, Strip test 75mm/ minute – Seam Strength and seam Slippage

6 5

1 4 3 2

1.

Base of the Unit.

2.

Control Panel.

3.

Holding Bush for Lower Jaw.

4.

Specimen (Test Cloth).

5.

Holding Bush for Upper Jaw.

6.

Microprocessor Based Calibrated Load Cell Unit (Inside the cover).

Jaws for Seam Slippage Strength & Elongation

Jaws for Seam Slippage Testing (1” x 1”)

National Institute of Fashion Technology, Bangalore (4” x 1”)

S. Steel Pins for fixing the Lea Strength Testing Jaws S. Steel Pins for fixing the Jaws.

Gauge to Determine Seam Slippage (6mm)

RELATED STANDARD ASTM D 5035, ASTM D 1578 ASTM D 5034, ASTM D 434

REFFERENCE STANDARD BS EN 1002 – 3 BS 1610 DIN 51221

National Institute of Fashion Technology, Bangalore

GRAB TEST Grab test is applicable to woven and non-woven and felt fabrics this test method is not recommended for glan fabrics or knitted fabrics and some other fabrics which are having high strength (more than 11%) Sample Preparation: Cut each specimen with help of standard template size - 5 samples parallel to warp thread and 5 samples parallel to weft thread as per standard sampling method and mark accordingly as below Upper jaw

1.5”

1”

1.5”

s

1.5”

3.0” 6”

1.5”

Lower Jaw

cC

National Institute of Fashion Technology, Bangalore

Seam Slippage and Seam Strength Sample Preparation: Cut each specimen with help of standard template size - 5 samples parallel to warp thread and 5 samples parallel to weft thread as per standard sampling method and mark accordingly as below

Upper jaw

1.5” 1.5”

1”

1.5”

1”

1.5” 1.5”

1.5” Seam line ½” ½”

Seam depth

1”

Seam line 1.5”

cC

Lower Jaw

1.5”

National Institute of Fashion Technology, Bangalore

Note: During Testing •

Sample size : Upper portion: 1.5” Lower portion : 1.5” Seam (depth) : ½”

•

Stitch a seam ½” inch (13mm) away from fold using a needle approximately 0.030”(076mm) in diameter with approximately 39 Tex white mercerized cotton or 36 Tex polyester/ cotton core thread.

•

The stitch per inch should be 14±1/2 per inch a plain lock stitch

•

The stitch should be under uniform tension.

•

The movement of thread should not be restricted by knotting or back stitching at the end of the specimens.

•

Adjust the speed of the upper jaw at 300±10 mm / minute by speed adjustment knob

•

Sample is placed between the jaws in such way that seam should be at the center of two jaws.

•

Provide uniform tension to specimen between the jaws.

•

Keep 6mm gauge ready with you for measuring the seam opening. It is advisable to keep it near the seam before the test starts for the accurate observation.

•

As soon as the seam opening matches the 6mm gauge. Stop the machine.

National Institute of Fashion Technology, Bangalore •

Observe the load on the digital indicator. It is the resistance to the warp / weft sliding over the weft / warp

•

Observe the load on the digital indicator. It is the resistance to the warp / weft sliding over the weft / warp.

•

Some times, before the seam opening the fabric breaks. In that case, stop the machine. Observe the load and it is the maximum, which the fabric can with stand, and seam strength is much higher than fabric strength.

Result interpretation of seam slippage STP - Seam Thread Problem FTS - Fabric Torn at Seam

Ravelled Strip Method It is a tension test on a strip of fabric in which the specified specimen width is secured by raveling away yarns. ¼”

¼” 1.5”

8”

1.5”

11”

National Institute of Fashion Technology, Bangalore

2”

Note: During Testing •

The specimen should be of width 2” inches and 8” inches test length.

•

Sample of 11” x 2.5” inches are cut, the bigger dimension is in the direction of testing

•

From the specimen, threads from the both edges are removed ( ¼” )until the width reduced to 2” exactly.

•

The rate of traverse for the top jaw is 12 inches/min (300mm/min) fixed.

Cut Strip Method It is a tension test a strip of fabric in which the specimen width is secured by cutting the fabric.

1.5”

11” 8”

1.5”

National Institute of Fashion Technology, Bangalore 2”

Note: During Testing •

This method of testing is identical to raveled strip method.

•

The sample width is 2” inches and the sample length is 8” inches.

•

The test specimens are cut for exact width and raveling of threads is necessary.

•

This method is used only for coated or heavy sized fabrics, where the raveling of the threads is difficult.

•

The procedure of doing the test is the same as that for raveled strip test.

Instrument - Standard Operating Procedure (SOP) •

Switch ON the machine by turning the main switch to ON position. Indicator will glow.

•

Switch ON the Digital Display panel by turning the display switch to ON position, wait for few seconds for stability. [(-) Negative sign on the display indicates unstable condition. Please wait till sign goes away]. Now the unit is ready for testing.

•

Two sets of jaws are supplied with the instrument, one set of jaws for Fabric strength testing and another one is for Seam Slippage Testing. Select the jaws depends upon the type of the test to be undertaken.

•

Fix the jaws to its respective position with the help of steel pin provided. Mount the test specimen to be tested between the jaws. Hold one end of the test specimen in the upper jaw. The test specimen should be locate centrally in the jaw. Similarly hold the lower end of

National Institute of Fashion Technology, Bangalore the specimen to the lower jaw. There should be slight tension in the specimen. The distance between the jaws is to be set as per the test requirement. •

Digital display should show “ 0 “ at the start of the test. When the sample is loaded. If the display does not show “ 0.00 “ press the button marked TARE / ZERO. The display will come to “ 0.00 “

•

Before exerting load on the specimen, push the HOLD / PEAK button Once. This is required to keep the maximum load on display as after the specimen breaks, load on display gradually comes to “ 0.00 “ automatically.

•

If you have not pushed the HOLD / PEAK button before exerting load, you can also find out the maximum load by pressing the HOLD / PEAK button after the test, as the maximum load automatically gets stored in the memory.

•

Push the LOAD switch to exert the load on the specimen, upper jaw start moving upwards and the jaws would stars separating, Rotate the Rotary to off position when test specimen breaks, note down the reading.

•

When specimen breaks stop the motor by pressing OFF switch. The breaking load (in Kegs . Force) will be displayed on the panel

•

For finding the elongation at break take the reading of the elongation scale immediately

[

after the specimen breaks Elongation at break = (Reading of the upper jaw pointer after

the specimen breaks) – (Reading of the upper jaw before the testing of the specimen) •

Press the UNLOAD switch for taking upper jaw downward.

]

National Institute of Fashion Technology, Bangalore •

Repeat the test with the number of samples are required.

Calculation and Result Sample No – Type of the sample EPC PPC GSM of sample Warp Count Weft Count

Breaking strength (Grab Test, strip test, cut strip method) Trial No 1 2 3 4 5 6 7 8 9 10 Average SD CV%

Breaking Strength in Kg.f

Elongation in Millimeter

Result : SI No 01 02 03

Description Breaking Strength % Of Elongation SD

Warp

Weft

National Institute of Fashion Technology, Bangalore 04

CV %

Sample No – Type of the sample EPC PPC GSM of sample Warp Count Weft Count

Stitches / inch Needle Number Needle Diameter Stitching Thread Count Needle Count Seam Type and Stitch Type

National Institute of Fashion Technology, Bangalore Seam strength and Slippage Trial No

Seam Strength in Kg.f

Seam Opening observation (At 6 mm Gauge)

1 2 3 4 5 6 7 8 9 10 Average SD CV% Result : SI No 01 02 03 04

Description Seam Strength Seam Opening at SD CV %

Warp

Weft