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D5379 – Standard Test Method Technical Guide
📐 Material Forms and Specimen Scope
The standard, designated as D5379/D5379M −19´1, specifically addresses shear testing of composite materials reinforced by high-modulus fibers. The scope is limited to continuous-fiber or discontinuous-fiber composites in the following forms:
| 🟦 Material Form (Per Sections 1.1.1–1.1.4) | 🎯 Fiber Orientation Specification |
|---|---|
| Unidirectional Fibrous Laminae | Parallel or Perpendicular to loading axis |
| Woven Fabric Filamentary Laminae | Warp direction parallel or perpendicular to loading axis |
| Cross-Ply (0/90) Laminae (balanced & symmetric) | 0° direction parallel or perpendicular to loading axis |
| Short-Fiber Composites | Majority of fibers randomly distributed |
As noted in the standard’s Note 1, this V-notched beam concept was originally developed for isotropic materials without specific reference to fiber direction.
⚙️ Test Procedure and Key References
The V-notched beam (Iosipescu) test method relies heavily on supporting ASTM standards for proper execution. Force verification follows Practices E4, and strain measurement techniques adhere to Test Methods E251 and Guide E1237. Material conditioning for polymer matrix composites is performed per D5229/D5229M.
| ⚡ Procedural Element | 📏 Governing Standard Reference |
|---|---|
| Force Verification of Testing Machines | E4 |
| Strain Gage Installation | E1237 |
| Moisture Conditioning | D5229/D5229M |
| Constituent Content Analysis | D3171, D2584 |
🔄 Unit System Independence: Per Section 1.2, SI and inch-pound values are not exact equivalents. Each system shall be used independently of the other to ensure conformance with the standard. Combining values from the two systems is prohibited.
📊 Key Measured Properties and Reporting
The test method allows for the determination of critical shear properties, including shear strength and shear chord modulus (per E111). Terminology and statistical practices follow E6 and E177/E456. Proper reporting of constituent content (D3171) and density (D792) is essential for full material characterization.
💡 Material Characterization: Determining fiber/resin content and void volume (D2734) is often correlated with shear performance. This standard is under the jurisdiction of Committee D30 on Composite Materials, Subcommittee D30.04.
❓ Frequently Asked Questions
🔍 What is the exact designation of the V-Notched Beam standard?
The full designation is D5379/D5379M −19´1, with an editorial correction noted in March 2021.
💡 Does this standard apply to discontinuous fiber composites?
Yes, Section 1.1.4 explicitly includes short-fiber-reinforced composites where the majority of fibers are randomly distributed.
⚡ Why must SI and inch-pound units be used independently?
According to Section 1.2, the values stated in each system are not necessarily exact equivalents; thus each system must be used separately to maintain accuracy and conformance.
📌 Which ASTM standards are referenced for verifying test forces and installing strain gages?
Practices E4 (Force Verification of Testing Machines) and Guide E1237 (Installing Bonded Resistance Strain Gages) are the definitive references for these procedures in the context of D5379.