ASTM C297 Tensile Strength of Sandwich Constructions

Scope:

The ASTM C297 test method provides information on flatwise tensile strength, core-to-face bonding stability, and load transfer of sandwich core materials. It tests discontinuous bonded surfaces, such as honeycomb materials, and continuous bonded surfaces, such as foams. The test results help select materials for designing parts that can withstand application force and ensure quality control of the materials chosen.

Test Procedure:

ASTM C297 test specimens are incised from sandwich panels, and their faces are bonded to aluminum blocks using an adhesive. The adhesive used is allowed to undergo appropriate conditioning before testing. Out of the two aluminum blocks, one is mounted in a fixture on the moving side of the universal test machine, and the second is mounted in a fixture on the fixed side of the universal test machine. The resulting assembly is then pulled apart at the recommended standard head displacement rate of 0.50 mm/min (0.020 in/min) until failure occurs. Sometimes, a speed that produces failure within 3 to 6 minutes may also be set. If a failure occurs between an aluminum block and the sandwich structure, then that is not accepted as a failure mode.

Elevated or Reduced Temperature Test Procedure:

The universal test machine has a thermal chamber installed. The chamber allows the test mounts from the base and crosshead of the testing machine to move through the top and bottom of the chamber. Standard test fixtures are fitted in the chamber, and Tensile Strength of Sandwich construction testing is carried out inside the controlled thermal environment to match the ambient temperature. The chamber has internal electric heaters to maintain high temperatures and uses external CO₂ gas to cool lower temperatures.

Specimen Size:

Various specimen sizes can be used to conduct a tensile strength test according to ASTM C297. Specimen geometry is based on the cell size for discontinuous cellular bonded sides. For continuous bonded surfaces, the least facing size is 625 mm2 (1.0 in2).

Data:

Tensile strength of sandwich constructions ASTM C297 test results determine the following:

• Core Failure
• Ultimate Flatwise Tensile Strength MPa (psi)
• Failure Location and Failure Modes:
• Cohesive Failure of Core-Facing Adhesive
• Adhesive Failure of Core-Facing Adhesive
• Facing Tensile Failure

Conclusion:

The ASTM C297 test method measures the flatwise tensile strength for structural design properties, material specifications, and research and development applications.