ISO 24281:2021 pdf free download – Textiles一Biaxial tensile properties of woven fabric – – Determination of maximum force and elongation at maximum force using the grab method.
8.2 Dimensions
The length and width of each test specimen shall be 400 mm ± 2 mm.
8.3 Preparation of test specimens
One each test specimen, a line shall be drawn a distance of 170 mm from one end of the warp and weft direction and drawn the direction of the warp by an arrow. Example of test specimens is illustrated in Annex B.
9 Procedure
9.1 Gauge length
Set the gauge length of the biaxial tensile-testing machine to 200 mm within ±1 mm.
9.2 Rate of extension
Set the rate of extension of the biaxial tensile-testing machine to 50 mm/mm.
9.3 Mounting of test specimens
Mount the test specimen by aligning one side of the clamp with the two lines drawn parallel to the warp and weft direction and refer to illustrated in Annex B. Zones “4-1” and “4-3” are mounted on the warp direction, and zones “4-2” and “4-4” are mounted on the weft direction.
The extension necessary to reach the pretension shall be added to the gauge length, thus determining the initial length needed for the calculation of the elongation at maximum force.
Apply the appropriate pretension specified as follows:
— for all fabrics with stretch characteristics: 0,5 N;
— for fabrics without stretch characteristics according to mass per unit area:
If all the results are jaw breaks, or if five “normal” breaks cannot be obtained, then the individual results shall be reported without the coefficient of variation or confidence limits. Jaw break results shall be indicated as such in the report, and the results discussed between the interested parties.
10 Calculation and expression of results
For each specimen, the average of the two maximum force values calculated for each direction is used as the result in that direction.
Calculate the arithmetic mean of the maximum force of five specimens by two directions, in newtons.
Round the results for values.
— <100 N to the nearest 1 N; — 100 N to < 1 000 N to the nearest 10 N; — 1 000 N to the nearest 100 N. For each specimen, the average of the two elongations at maximum torce values calculated tor each direction is used as the result in that direction. Calculate the arithmetic mean of the elongation at maximum force of five specimens by two direction and round it to the nearest: — 0,2 % for elongations <8 %; — 0,5 % for elongations 8 % to75 %; — 1 % for elongations > 75 %.
If required, calculate the coefficient of variation to the nearest 0,1 % and the 95 % confidence limits
rounded to the same precision as the mean value.
11 Test report
The test report shall include the following information:
a) reference to this document, i.e. Iso 24281:2021;
b) date of test;
c) identification of the test sample and sampling procedure, if required;
d) number of test specimens, including the number of tests rejected and reasons for this;
e) gauge length in millimetre;
f) rate of extension in mm/mm;
g) pretension applied, in newtons;
h) preconditioning, conditioning and testing atmosphere;
i) arithmetic mean of the maximum force, in newtons;
j) arithmetic mean of the elongation at maximum force, in percent;
k) coefficient of variation of the mean value, in percent, if required;
1) 95 % confidence limits of the mean value, in newtons, and of the relevant elongation, in percent, if required;