Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D6110-18 – Standard Test Method Technical Guide
ASTM D6110-18 outlines a standardized method for determining the resistance of plastics to breakage by flexural shock. Using a pendulum-type hammer, this test method measures the energy absorbed by a notched specimen during a single high-speed impact. The introduction of a milled notch creates a controlled stress concentration, promoting brittle fracture and reducing data scatter, which yields a reliable assessment of a material’s impact resistance.
📐 Specimen Geometry and Types
The standard specifies specimens with a fixed length and depth, while the width can vary within defined limits to accommodate different material behaviors. The most critical geometric element is the milled V-notch, which serves to concentrate stress and minimize plastic deformation during the break.
| 🟦 Specimen Type | 📏 Length (mm) | 📐 Depth (mm) | 🎯 Width (mm) |
|---|---|---|---|
| Type 1 | 80 ± 2 | 10 ± 0.2 | 4 ± 0.2 |
| Type 2 | 63.5 ± 2 | 12.7 ± 0.2 | 3.2 – 12.7 |
Notch Dimensions: The single allowed notch design features a 45° ± 1° included angle with a radius of 0.25 mm ± 0.05 mm at the base. The depth of the notch under the specimen is strictly maintained at 2.54 mm ± 0.05 mm. This precise machining is critical for consistent fracture propagation and minimizing scatter in the energy-to-break results.
⚙️ Test Procedure and Machine Requirements
The test is performed on a standardized pendulum machine. The hammer is released from a fixed height, ensuring a substantially constant impact velocity. For most Charpy tests, this standard velocity is 3.46 m/s.
⚠️ Caution: While the velocity is fixed, hammers with different initial energies are recommended for specimens with varying impact resistance. The user must select a hammer that results in a break using 10% to 80% of the available energy to ensure accurate results. Always record the hammer capacity and support span used.
Specimens are conditioned according to Practice D618. The test procedure involves placing the specimen flat on a support span (typically 60 mm for Type 1 specimens) with the notch located midway between the supports and facing away from the pendulum. A minimum of ten individual specimens is typically tested for each sample to account for material variability. The precise method of notching, speed of the notching tool, and time between notching and testing are documented alongside the results.
📊 Key Measured Properties
The primary result is the energy absorbed during the fracture. The standard reports impact resistance in terms of energy absorbed per unit of specimen width under the notch (J/m or ft·lb/in).
| ⚡ Parameter | 📊 Specification |
|---|---|
| Impact Resistance (J/m) | Energy absorbed divided by the width of the specimen under the notch. |
| Impact Velocity | 3.46 m/s (standard pendulum fall height). |
| Hammer Energies (Recommended) | 2.7 J, 5.4 J, 10.8 J, 21.6 J. |
💡 Interpreting Results: Caution is essential when comparing data. This standard shares a title with ISO 179 only; the content, specimen geometry, and calculations are significantly different. Be aware that factors such as method of fabrication, environmental conditioning, thermal treatment, and notch quality heavily influence the final impact resistance value.
❓ Frequently Asked Questions
🔍 What is the main difference between ASTM D6110 (Charpy) and ASTM D256 (Izod)?
The primary difference lies in the specimen support configuration. In the Charpy test (D6110), the specimen is supported at both ends and struck in the middle (three-point bending). In the Izod test (D256), the specimen is cantilevered vertically and struck at the free end. This results in different stress distributions and fracture mechanics.
💡 Why does the standard require a milled notch?
The notch acts as a stress concentrator. It forces the fracture to occur in a specified location behind the notch and promotes a brittle failure. This minimizes the energy lost to plastic deformation and reduces the scatter in the test results, providing a clearer measure of the material’s resistance to crack propagation under impact.
⚡ How is the impact resistance calculated from the test data?
The standard calculates the result by dividing the energy absorbed by the original width of the specimen under the notch (total depth minus notch depth). The formula is: Impact Resistance = Energy Absorbed / Specimen Width Under Notch. The result is typically expressed in joules per meter (J/m) or foot-pounds per inch (ft·lb/in).
📌 What is the significance of the fixed hammer velocity?
The fixed hammer fall height ensures a substantially constant velocity at the moment of impact (generally 3.46 m/s for the standard pendulum). This standardization is critical because the impact behavior of plastics is highly strain-rate sensitive. A consistent velocity allows test results from different laboratories and different materials to be directly compared.