ASTM D6068 Standard Test Method for Determining J-R Curves of Plastic Materials

Get Certified ASTM D6068 Testing for Reliable Plastic Fracture Evaluation

Cracks can form on plastic parts under mechanical loading or in service. Fracture tests give engineers insight into how a plastic material responds when a crack forms and propagates. ASTM D6068 is an established standard method for the determination of J-R curve data. These results can be used for material comparison, product development, structural evaluation, and quality control.

• Measures J-R curves of plastic materials.
• Assesses resistance to crack initiation.
• Assesses stable crack growth.
• Works with precracked or notched specimens.
• Measures load and displacement in a test.
• Helps in characterizing fracture behavior.
• Compares plastic materials.
• Supplies information for engineering fracture analysis.

What are the Uses of ASTM D6068 Testing?

ASTM D6068 testing helps laboratories characterize the fracture resistance of plastic materials. Engineers use the results to understand how plastics respond to crack growth under mechanical loading. This standard-

• Determines J-R curves.
• Assesses resistance to initiation of cracks.
• Describes steady crack growth.
• Assists in comparing plastic formulations.
• Helps research into fracture mechanics.
• Assists in assessing material performance.
• Assists in plastic parts & plastic products development.

Which materials can be tested under ASTM D6068?

ASTM D6068 is applicable to plastic materials that can be formed into fracture-test specimens. The material chosen should exhibit a measurable response to the loading and crack-growth conditions. The choice of test configuration should account for the type of plastic, specimen geometry, thickness, notch condition, and the anticipated fracture behavior.

Why is ASTM D6068 Important?

ASTM D6068 is a standard method for assessing the resistance of plastic materials to crack initiation and growth. J-R curve data can provide more information about fracture behavior than a simple strength measurement. The results are used to compare materials and assess plastics for use in components in which resistance to crack growth is a concern.

ASTM D6068 Testing Process and Data Collection

The analyst selects a representative plastic specimen and prepares the required notch or precrack. Afterward, the specimens are measured and properly placed in the testing machine. The operator then applies controlled mechanical loading, and the system records the force and displacement. Technicians monitor the specimen response and the extent of crack extension during the test. Finally, the appropriate values of J are computed, and the J-R curve is created. The resulting relationship is used in laboratories to identify the resistance of the material to crack initiation and stable crack growth.

Common Challenges and Troubleshooting

The quality of the ASTM D6068 results depends on proper specimen preparation, notch or precrack quality, machine alignment, and reliable crack-growth measurements. Specimen geometry may influence fracture calculation results. They should check specimen dimensions and machine alignment before testing. Consistent J-R curve data can also be achieved by accurate load and displacement measurements in the lab.

• ASTM D6068 yields J-R curve data and not an overall material value.
• The J-integral values are often expressed in units of kJ/m² or N/mm.
• Crack extension can be measured in mm or inches.
• The J-R curve represents a change in fracture resistance with crack extension.
• Results can be used to determine crack initiation and stable crack-growth behavior.
• Laboratories can achieve reliable results by using consistent specimen preparation and accurate crack measurements.

Link to ASTM D6068