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D6077-16 – Standard Test Method Technical Guide
ASTM D6077-16 (Reapproved 2023) provides a standardized test method for measuring the Trapezoid Tearing Strength of Leather. This method covers the determination of the tearing load using the trapezoid configuration, assessing the nonwoven structure of the material. Per the standard, the values stated in SI units are to be regarded as the standard.
📐 Specimen Geometry and Sampling
An outline of a trapezoid is marked on the test specimen. The nonparallel sides of the specimen are clamped in the jaws of a tensile testing machine. As the load is continuously increased, the tear propagates across the specimen width. The breaking load is determined from the autographically recorded load-elongation (stress-strain) curve.
Unless otherwise specified, ten test specimens are required (Section 7.1). Specimens must be cut parallel and perpendicular to the backbone or parallel and perpendicular to the cut part. Sampling must rigorously follow Practice D2813 for Physical and Chemical Tests.
⚙️ Test Procedure and Conditioning Requirements
The required apparatus is a constant-rate-of-traverse (CRT) tensile testing machine equipped with an autographic recorder. The clamps must have faces measuring 25 mm by 75 mm (1 in. by 3 in.), with the longer dimension perpendicular to the direction of the applied load. A template (dimensions per Fig. 1 of the standard) is optional. Pawls are bolted onto the machine to allow motion in only one direction for accurate peak load capture.
Proper conditioning per Practice D1610 is mandatory. Testing must be conducted in the standard atmosphere for testing, as identified in Section 9.1 of the standard.
⚠️ Material Exclusion: Per Section 1.1, this test method explicitly does not apply to wet blue leather.
💡 Technical Note: The machine pawls are critical as they ensure the crosshead moves in one direction only following complete specimen failure, allowing for an unambiguous reading of the recorded peak load from the autographic chart.
📊 Key Measured Properties and Significance
The trapezoid tearing load is fundamentally a tension test. The recorded test strength is primarily determined by the interlocking structure of the fibers, making it an excellent indicator for estimating the relative ease of tearing of leather (Section 4.1). Furthermore, this procedure can be used to detect appreciable differences in the relative strength of the leather when tested in the parallel and perpendicular directions relative to the backbone (Section 4.2).
| 🟦 Parameter | 📏 Requirement |
|---|---|
| Specimen Shape | Trapezoid |
| Number of Specimens | 10 (Default) |
| Sampling Standard | Practice D2813 |
| Conditioning Standard | Practice D1610 |
| Test Directions | Parallel & Perpendicular to backbone or cut part |
| Data Output | Load-Elongation (Stress-Strain) Curve |
| ⚙️ Apparatus Component | 🎯 Specification |
|---|---|
| Testing Machine | CRT Type with autographic recorder |
| Clamp Face Dimensions | 25 mm × 75 mm (1 in. × 3 in.) |
| Clamp Orientation | Longer dimension perpendicular to applied load |
| Template | Optional (see Fig. 1 of standard for dimensions) |
| Pawls | Allow motion in only one direction |
❓ Frequently Asked Questions
🔍 What does the trapezoid tearing test fundamentally measure?
It measures the tearing load of the leather. The derived test strength is primarily determined by the interlocking structure of the fibers, offering a reliable estimate of the material’s relative ease of tearing.
💡 How many test specimens are typically required for this standard?
Unless otherwise specified by the contracting parties, the standard specifies testing ten (10) test specimens (Section 7.1). These must be cut in both the parallel and perpendicular directions to the backbone.
⚡ What specific tensile testing machine setup is mandated?
The standard mandates a constant-rate-of-traverse (CRT) tensile testing machine equipped with an autographic recorder to register the applied load. Clamps must have 25 mm × 75 mm faces with the longer dimension perpendicular to the load.
📌 Is this test method applicable to wet blue leather?
No. Per the explicit scope exclusion in Section 1.1, this test method does not apply to wet blue. It is designed specifically for finished leather and nonwoven fabrics in leather forms.