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D5937-96 – Standard Test Method Technical Guide
📐 Specimen Geometry and Types
ASTM D5937-96 is technically identical to ISO 527-2 and specifies the use of standardized test specimens to ensure reproducible results. The standard applies to rigid and semirigid thermoplastic and thermosetting materials, including those filled with short fibers, rods, plates, or granules. The multipurpose test specimen (ISO 3167 / D5936) is the preferred geometry, allowing for the determination of multiple mechanical properties from a single molding.
| 🟦 Dimension | 📏 Type 1A (Injection Moulded) | 📐 Type 1B (Machined) |
|---|---|---|
| Overall Length | ≥ 150 mm | ≥ 150 mm |
| Width at Ends | 20.0 ± 0.2 mm | 20.0 ± 0.2 mm |
| Width at Narrow Section | 10.0 ± 0.2 mm | 10.0 ± 0.2 mm |
| Gauge Length (L₀) | 50.0 mm | 50.0 mm |
| Thickness | 4.0 ± 0.2 mm | 4.0 ± 0.2 mm |
💡 Key Recommendation: The multipurpose test specimen (D5936 / ISO 3167) is strongly preferred. Specimens may be directly injection molded into the chosen dimensions, or machined, cut, or punched from compression-molded or injection-molded plates.
⚙️ Test Procedure and Speed Selection
The choice of test speed is critical and must be selected based on the material’s brittleness or ductility. The standard classifies test speeds to ensure the strain rate is appropriate. Testing must be conducted at standard laboratory atmosphere (23°C ± 2°C, 50% ± 10% RH) unless otherwise specified by the material standard.
| ⚡ Speed Class | 🏃 Test Speed | 🎯 Recommended Application |
|---|---|---|
| Speed A | 1 mm/min | Tensile Modulus determination (all materials) |
| Speed C | 5 mm/min | Low elongation materials (εb ≤ 10%) |
| Speed F | 50 mm/min | Medium elongation materials |
| Speed I | 500 mm/min | High elongation materials |
⚠️ Critical Distinction: While ASTM D5937 is comparable to ASTM D638, the two standards must not be substituted for one another. Differences in specimen dimensions, conditioning procedures, equipment, and testing conditions may yield different results. Always cite the specific standard used.
📊 Key Measured Properties
The tensile test according to D5937 generates a stress-strain curve from which several fundamental mechanical properties are calculated. An extensometer must be used to accurately record the strain data for modulus calculations.
- Tensile Modulus (Et): The ratio of stress to strain in the initial linear region, measured precisely using Speed A (1 mm/min). This is a critical measure of material stiffness.
- Yield Stress (σy): The stress at the first point on the stress-strain curve where an increase in strain occurs without an increase in stress.
- Stress at Break (σb): The maximum tensile stress recorded at the moment of specimen rupture.
- Strain at Break (εb): The increase in gauge length relative to the initial gauge length at the moment of rupture. Nominal strain at break is frequently reported for ductile materials.
❓ Frequently Asked Questions
🔍 What is the difference between ASTM D5937 and D638?
ASTM D5937 is technically identical to ISO 527-2, making it the preferred standard for international compliance. While both standards measure tensile properties of plastics, D638 is the traditional ASTM method. The standards differ in specimen dimensions conditioning, and test speed selection, so results are not interchangeable.
💡 What is the preferred test specimen for ASTM D5937?
The standard explicitly recommends the multipurpose test specimen specified in ISO 3167 (ASTM D5936). Type 1A (direct injection molding) and Type 1B (machined) are the most common. This geometry provides a standardized method for testing multiple properties.
⚡ Which test speed should I use for modulus determination?
Speed A (1 mm/min) is the designated speed for the accurate determination of the tensile modulus. An extensometer is mandatory for this measurement. After the modulus test is complete, the speed may be increased to the appropriate rate for the specific material to determine strength and elongation.
📌 Is this standard suitable for fiber-reinforced plastics?
Yes, for materials reinforced with short fibers, small rods, plates, or granules. However, it is not suitable for materials reinforced with textile fibers (continuous or woven), rigid cellular materials, or sandwich structures containing cellular materials.