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D2261-13 – Standard Test Method Technical Guide
📐 Scope and Applicable Materials
ASTM D2261-13 (Reapproved 2024) describes the Standard Test Method for measuring the tearing strength of textile fabrics by the tongue (single rip) procedure using a recording constant-rate-of-extension (CRE) tensile testing machine. This method is applicable to most fabrics, including woven, knit, non-woven, air bag, blanket, napped, layered, and pile fabrics. The fabric can be untreated, heavily sized, coated, resin-treated, or otherwise treated.
| 🟦 Scope Element | 📋 Specific Details |
|---|---|
| Fabric Types | Woven, air bag, blankets, napped, knit, layered, pile, non-wovens. |
| Fabric Treatments | Untreated, heavily sized, coated, resin-treated, or otherwise treated. |
| Test Conditions | Specimens can be tested dry or wet. |
| Units | SI (N) or Inch-pound (lbf) values are regarded as standard. |
⚙️ Test Procedure and Equipment
The test utilizes a recording constant-rate-of-extension (CRE) tensile testing machine, which is the preferred apparatus. The standard requires that the tear be initiated before the testing force is applied, meaning the “tongue” of the fabric is cut prior to clamping. Specimens must be conditioned according to Practice D1776/D1776M.
⚠️ Alternative Apparatus: The CRE machine is preferred, but some Constant-Rate-of-Traverse (CRT) tensile testing machines continue to be used. These instruments are permitted when specifically agreed upon by the purchaser and the supplier, under the conditions detailed in Appendix X1.
| 🔧 Parameter | 📐 Requirement |
|---|---|
| Primary Machine | Recording Constant-Rate-of-Extension (CRE) per D76/D76M. |
| Alternative Machine | Constant-Rate-of-Traverse (CRT) per Appendix X1 (by agreement). |
| Test Initiation | Tear must be pre-initiated (single rip / tongue cut) prior to clamping. |
| Conditioning Standard | D1776/D1776M. |
💡 Key Technical Insight: As stated in Section 1.3, because the tear is initiated before the test, the reported value is not directly related to the force required to start or initiate a tear. It specifically measures the force required to propagate the tear.
📊 Key Measured Properties and Calculations
The standard provides two specific calculations for tongue tearing strength derived from the force-displacement record. These calculations offer different perspectives on the material’s resistance to tear propagation.
| 📐 Calculation Method | ⚡ Definition |
|---|---|
| Single-Peak Force | The highest single force value recorded during the tear of a specimen. |
| Average of Five Highest Peaks | The arithmetic mean of the five highest distinct peak forces recorded during the tearing process. |
❓ Frequently Asked Questions
🔍 Can this method test heavily coated or resin-treated fabrics?
Yes. The standard explicitly includes fabrics that are untreated, heavily sized, coated, resin-treated, or otherwise treated in its scope.
💡 Does this test measure the force needed to start a rip in the fabric?
No, the test requires that the tear is initiated before the test begins. The measurements represent the force required to propagate an existing tear.
⚡ What should I do if only a CRT tensile testing machine is available?
While the CRE type is preferred, the standard allows the use of CRT instruments when formally agreed upon between the purchaser and the supplier, following the guidelines in Appendix X1.
📌 How are the results reported in terms of units?
Per Section 1.5, the values stated in either SI units (Newtons) or inch-pound units (pounds-force) are to be regarded separately as the