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D5587-15 – Standard Test Method Technical Guide
📐 Specimen Geometry and Types
The trapezoid tearing strength test utilizes rectangular specimens with an isosceles trapezoid marked on them. The smallest base of the trapezoid is slit to initiate the tear before clamping. This test method covers a wide range of fabrics.
| 🟦 Fabric Category | 📐 Typical Applications | ⚡ Treatment Examples |
|---|---|---|
| Woven fabrics | Apparel, industrial textiles | Sized, coated, resin-treated |
| Nonwoven fabrics | Filters, disposables, medical | Untreated, resin-treated |
| Knitted fabrics | Sportswear, medical textiles | Heavily sized, otherwise treated |
| Air bag fabrics | Automotive safety | Coated |
⚙️ Test Procedure and Speed Selection
The test procedure involves clamping the nonparallel sides of the marked trapezoid in a recording constant-rate-of-extension (CRE) tensile testing machine. While CRE is preferred, constant-rate-of-traverse (CRT) machines may be used by agreement. The specimen is slit at the center of the smallest base, and the tear is propagated, with tearing force recorded. Speed selection should follow the standard guidelines for accurate results.
💡 Tip: Condition specimens according to Practice D1776/D1776M before testing to ensure consistent moisture content and temperature.
📊 Key Measured Properties
The test method provides two calculations for tearing strength: the single-peak force and the average of five highest peak forces. Values are reported in SI units (standard) with approximate inch-pound units.
| 🟦 Calculation Method | 📏 Description | 🎯 Unit |
|---|---|---|
| Single-peak force | Maximum force during tear propagation | N (or lbf) |
| Average of five highest peaks | Average of five largest forces recorded | N (or lbf) |
For more details on the specific values and calculations, refer to the full standard.
⚠️ Warning: The tearing strength measured in this test is not directly related to the force required to initiate a tear; it represents the force to propagate an existing tear.
❓ Frequently Asked Questions
🔍 What is the difference between single-peak force and average of five highest peak forces?
The single-peak force captures the maximum tearing force during the test, while the average of five highest peak forces provides a more comprehensive measure by considering multiple tear events, reducing the impact of anomalies.
💡 Can this test method be used for wet specimens?
Yes, the standard provides instructions for testing specimens with or without wetting, allowing for evaluation of fabric performance under different conditions.
⚡ What types of fabrics are applicable for this test?
This test method applies to most fabrics, including woven, air bag, blankets, napped, knitted, layered, pile, and nonwoven fabrics, with various treatments like sizing, coating, or resin treatment.
📌 What is the purpose of slitting the specimen at the smallest base?
The slit initiates the tear before testing, ensuring that the tearing strength measured is for propagation rather than initiation, as specified in the method.