(Modified ASTM D 4632 and DIN EN ISO 10319)
Significance
The GCL peel test provides a means of evaluating the needling strength of Bentofix® GCLs and is an index procedure which is used to monitor needle wear during production. Needles are changed as peel test results begin to approach the minimum acceptable strength. Additionally it can be used as an index for the internal shear strength of Bentofix®.
Description
Method ASTM D 4632 and DIN EN ISO 10319 are used as a basis for determining specimen size, testing equipment and the general test procedure subject to modifications in the rate of expansion, grip size as well grip orientation.
In the peel test, a Bentofix® specimen is partially de-laminated by cutting the needlepunched bonds between the geotextiles just enough to allow each geotextile to be separately inserted into the grips of the tensometer. The specimen is peeled at 300 mm per minute and the maximum peak resistance is recorded as the peel strength for that individual specimen. Several specimens are tested to determine the peel strength of a sample.
QC Test Frequency
Peel Testing is performed at a minimum frequency of one test series every 4,000 m2 of material produced. This frequency is typically increased when peel strengths approach the minimal acceptable level.
For each test, a Bentofix® roll is manufactured an extra 0.30 m long based on the interval of sampling required. A 0.30 m QC testing sample over the entire width is then cut off. Five (5) test specimens spaced across the width of the testing roll in production direction are obtained for examination.
Test Procedure
1. A 0.30 m long by full roll-width sample is cut from each designated production Bentofix® roll. This sample is termed the testing roll.
2. Using a template, five 10 cm x 300 cm specimens are cut from the testing roll with the longer length oriented in the machine direction. Specimens not exhibiting proper orientation are rejected and a new specimen is cut.
Test Procedure Continued:
3. A utility knife is used to slice the needlepunched bonds 0.05 m apart between the two geotextiles from the designated end of each specimen.
4. The grips are oriented so that the wide width of the grip (0.10 m width) is parallel to the four inch width of the test specimen and perpendicular to the applied stress. As mounted the grip will apply a four inch wide stress.
5. The specimen is mounted in the testing device such that the upper jaw contains the one geotextile flap and the lower jaw contains the second geotextile flap. As mounted the grip will apply a four inch wide stress.
6. The jaws should be set at a baseline distance of approximately one inch apart.
7. With the tensile testing device set to a constant rate of expansion of 300 mm/min., the specimens are peeled until full separation is achieved.
8. The peak bonding strength for each specimen is then recorded, rounded off to one digit after the decimal. The reported peel value is the average of five peak bonding values.
Acceptance Criteria
The average of the five peak values must be greater than or equal to the specified value (data sheet). Individual specimen results may fall below the specified value if the average of the five specimens is equal or greater than the specified value. If the average value falls below the specified value, the test is repeated on 5 additional specimens taken from adjacent locations on the same testing roll. If the average of the individual peaks of the 10 specimens exceeds the specified value, the roll and the representative production material is deemed to be acceptable.
If the average is less than the specified value, the roll is not accepted for shipment. The Bentofix® rolls manufactured immediately before and after the rejected roll are then sampled and tested as described above in steps 1 – 8 and the same acceptance/rejection criteria are applied to these rolls. This process is repeated until the acceptance criteria are achieved to isolate non-confirming rolls.
Bentofix® Specified Value
A minimum acceptable peel strength is used to qualify material as peel values will vary depending upon the sample roll's proximity to the last needleboard change. Bentofix® specifies a minimum index peel strength under the above test procedure as it not only aides in the manufacturing process but it also is a quick method of ensuring thorough needlepunching characteristics are maintained, and allows a judgement for the internal shear behavior of Bentofix® GCLs.
