Saturday, July 18, 2009

Tensile Tests



Tensile (breaking) strength
Fabric samples are clamped in the jaws of a tensile tester and pulled apart until they break. Three samples are tested across the warp and three across the weft and the average breaking strength established is expressed in Newtons. BS 2543 states that tensile strength should be as follows for the different grades of intended duty

Breaking Strength and Elongation of
Textile Fabrics (Grab Test) ASTM D5034


The grab and modified grab tests determine breaking
strength and elongation of wet or dry textile fabrics. A grab
test is a tensile test where the center of the specimen width
is gripped in the clamps. The modified grab test is similar -
lateral slits are made mid-length of the specimen severing
all yarns bordering that portion of the specimen held
between the two clamps.
The grab test applies to woven, non-woven, and felted
fabrics, while the modified grab test is used for woven
fabrics. The method is not used for glass fabrics, knitted
fabrics or high stretch fabrics.
The grab test determines the effective strength of the
fabric: the strength of the yarns in a specified width with
fabric assistance from the adjacent yarns. It doesn’t reflect
yarn strength actually gripped between clamps. The
modified grab test determines the breaking force of fabrics
with constructions in which the application of tensile stress
on ravel strip specimens produces further unraveling. It
applies to high-strength fabrics.
Grab test: front grip face measures 1 inch by 1 or 2 inches,
the longer dimension along the vertical.
Modified grab test: front grip face measures 1 inch by 2
inches, with the longer dimension along the vertical.

Overall Test System Requirements
• Size System to generate highest expected load
• Select load cells for sample breaks at 10 to 90% of
load cell range
• Define Jaws - Grab Test or Modified Grab Test
with either rubber coated or smooth surfaces

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