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D5733-99 – Standard Test Method Technical Guide
📐 Specimen Geometry and Preparation
This test method employs a precisely defined trapezoidal specimen to ensure consistent stress concentration during tear propagation. The rectangular blank for the specimen must be cut to 150 mm in length and 75 mm in width. An isosceles trapezoid is then marked on the specimen, featuring a 25 mm base at the narrow end and a 100 mm base at the wide end. A precise 15 mm cut is made at the center of the narrow end to serve as the initiation point for the tear. The gauge length between the clamps of the tensile tester is set to 25 mm.
| 🟦 Parameter | 📐 SI Value | 📏 Inch-Pound Value |
|---|---|---|
| Specimen Length | 150 mm | 6 in |
| Specimen Width | 75 mm | 3 in |
| Narrow Edge Width | 25 mm | 1 in |
| Wide Edge Width | 100 mm | 4 in |
| Initiation Cut Length | 15 mm | 0.5 in |
| Gauge Length | 25 mm | 1 in |
| CRE Test Speed | 300 mm/min | 12 in/min |
⚠️ Critical Conditioning Requirement
Per ASTM D1776, all test specimens must be conditioned to moisture equilibrium in a standard atmosphere of 21 ± 1°C (70 ± 2°F) and 65 ± 2% relative humidity for a minimum of 4 hours prior to testing. Failure to properly condition specimens is a common source of variability in tearing strength results. Directionality (machine vs. cross direction) must be clearly tracked, as nonwovens may lack a visually distinct orientation pattern.
Per ASTM D1776, all test specimens must be conditioned to moisture equilibrium in a standard atmosphere of 21 ± 1°C (70 ± 2°F) and 65 ± 2% relative humidity for a minimum of 4 hours prior to testing. Failure to properly condition specimens is a common source of variability in tearing strength results. Directionality (machine vs. cross direction) must be clearly tracked, as nonwovens may lack a visually distinct orientation pattern.
⚙️ Test Procedure and Speed Selection
The trapezoid test is conducted by clamping the specimen along its non-parallel sides in a constant-rate-of-extension (CRE) tensile testing machine, operating at the standard speed of 300 mm/min. As the clamps separate, stress is concentrated at the apex of the pre-cut, propagating the tear. The machine records the force required to continue the tear across the fabric width. While the CRE apparatus is the preferred instrument, the standard recognizes that Constant-Rate-of-Traverse (CRT) machines are still in common use. If a CRT machine is employed, it must only be used by agreement between the purchaser and the supplier,