Designation: D – 98 (Reapproved ) Standard Test Method for Peel Strength (“T” Method) of Hook and Loop Touch Fasteners1 This. ASTM D Standard Test Method for Peel Strength (“T” Method) of Hook and Loop Touch Fasteners. ASTM D – Peel Strength (T Method) of. Hook and Loop Touch Fasteners. Scope: This test measures the peel strength of 2 strips of Hook and Loop material .
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A number in parentheses indicates the year of last reapproval.
Scope This test method covers the measurement of the peel strength of hook and loop touch fasteners using a recording constant-rate-of-extension tensile testing machine CRE. The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Significance and Use This test method gives a measure of a key property of hook and loop touch fasteners which is of interest to users of such devices.
This is a means of determining the resistance to separation when forces are applied normal to the line of separation of the fastener.
The force registered in a peel test is irregular, and as a consequence, empirical methods have had to be developed to obtain usable values related to peel strength. In spite of the empirical nature of the reported values, it is believed they reflect comparative performance of similar touch fasteners tested and measured in the same way. Two optional methods of calculation are provided: Current edition approved June 1, Originally approved in Last previous edition approved in as D – 98 Generally, the integrator average will be lower than the average of the five highest peaks.
The highest peaks which reflect the force required to separate a hook and loop closure bear no simple relationship to the average force integrator average. The average of the five highest peaks better reflect performance but the integrator results may be used to characterize a closure and for quality control purposes.
The integrator average is relatively easy to calculate given the proper equipment. In the case of a dispute arising from differences in reported test results when using this test method for acceptance testing of commercial shipments, the purchaser and the supplier should conduct comparative tests to determine if there is a statistical bias between their laboratories.
Competent statistical assistance is recommended for the investigation of bias. As a minimum, the two parties should take a group of test specimens which are as homogenous as possible and which are from a lot of hook and loop of the type in question. The test specimens should then be randomly assigned in equal numbers to each laboratory for testing. If a bias is found, either its cause must be found and corrected or the purchaser and the supplier must agree to interpret future test results in the light of the known bias.
Apparatus Roller—consisting of a smooth steel surface, approximately 43? The weight of the roller including the handle is 11 6 1? The tester shall have two clamps with centers in the same plane, parallel to the direction of the motion of the stressing clamp, and so aligned that they will hold the specimen ends wholly in the same plane; a means of moving the stressing clamp at a uniform rate of The four specimens of hook and loop selected will be used to characterize the peel strength of each of the configurations.
Lay specimens flat with the functional side up so that the conditioning atmosphere has free access to them. Procedure An initial closure is made and separated to raise the loops that might have been compressed in packaging. Select from the four specimens of hook and loop, the first closure to be tested and referring to Fig. The instrument shall be calibrated to an accuracy of 1. Sampling Select the test samples so as to be as representative of the unit a shipment, a lot, and so forth as possible.
Lot—A lot shall consist of all the material of the same type, color and width, made at the same time from the same materials in no more than a two week period. It shall be expressed in linear units of 10 yards m. Sample Rolls—One roll shall be randomly selected from each linear unit 10 yards m. If the lot does not contain five units, additional rolls shall be selected from the lot to give a sample size of five rolls. For specification purposes, the material under test must be mated with material supplied by the manufacturer of the material being tested.
Specimen Preparation Hook and loop material for this test shall be in the width as supplied, not to exceed 1 in. For materials greater than 1 in. If material less than 1 in. Remove the outer layer of each roll before selecting the required number of strips, hook and loop, 8 in.
ASTM D – 98 Standard Test Method for Peel Strength (T Method) of Hook and Loop Touch Fasteners
This arrow is marked on the specimen on the leading end as it is unwound from the roll. Select a sample consisting of four contiguous specimens as described in 8.
Carefully align and superimpose the hook strip over the loop strip so that the hook strip covers the loop strip, and the marked ends are matched as shown in Fig. Place a flat steel plate 8 in. After 2 s remove the plate.
This initial mating of the closure is done to create just enough hook and loop engagement so as to be able to continue with the test procedure. Securely fasten the two ends of the mated hook and loop to a hard flat surface such as a metal plate, table top, etc. Push the roller without adding weight from the end of the closure to be separated by the tensile tester over the entire length of the joined strips and then pull it back over the entire length.
This constitutes one cycle; a continuous uninterrupted back and forth motion of the roller, without lifting it from the material.
Each cycle should take about 2 s. Remove the specimen from the holder, then hand separate this initial closure from the end indicated to be joined in the tester clamps as indicated in Fig.
Then, again make the closure as described in 8. Prepare the second closure specimen as described in 8. Prepare the third closure specimen as described in 8. Prepare the fourth closure specimen as described in 8. In the sequence in which the closure specimens were prepared, select them for testing in the tensile tester.
Preparing the Specimens
Gently separate approximately one inch of closure ashm the end to be placed into the clamps as indicated in Fig. This will create two free ends to be inserted into the tensile tester. Position the clamps of the tensile tester so they are 1 6 1?
Place the free ends of the specimen to be tested in the clamps of the tester with the hook strip in the moving clamp.
The d517 of separation should be approximately centered and aligned approximately parallel to the clamps. Use a clamp separation speed of atsm If an integrator is used, set it such that the first and last inches of separation are not included in the results. Observe the chart paper produced by the autographic recorder.
A jagged line having multiple peaks will be produced.
Make note on the recording chart of the test specimen number and sequence number from Fig. Mark five successive equal portions on the chart excluding the first and last inch of separation. Determine the highest peak value in each portion. Calculate the average of these five highest values for each of the four specimens. Calculate the average of the values from the four closures representing the four configurations.
Calculate the average of the integrator values from the four closures representing the four directions. Calculate the average of the values from each of the five samples. If specimens less than 1 in. Report Report the following information: Precision and Bias Precision—Based on limited testing from one laboratory using integrator averages, the within-laboratory or repeatability standard deviation is about 0.
Repeatability is dependent on the specific material being tested; some materials would be expected to be higher or lower than this. Between-laboratory reproducibility is being determined by the subcommittee. Bias—The procedure in Test Method D for measuring the peel strength of hook and loop touch fasteners has no bias because the value of the peel strength of hook and loop touch fasteners can be determined only in terms of a test method.
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