Tensile Strength of Sandwich Constructions ASTM C297

Understanding the Ultimate Tensile Strength and Failure of Sandwich Core Materials Using ASTM C297 Test Method

Sandwich structures are widely used in various industries due to their excellent strength-to-weight ratio. The ASTM C297 test method provides important information on the bonding stability, load transfer, and flatwise tensile strength of sandwich core materials. This test method is applicable to both continuous and discontinuous bonded surfaces, such as foam and honeycomb materials, respectively. The data obtained from this test is used for material specification, design optimization, and quality control purposes.

To ensure that the physical properties of the materials are accurately represented in the test, it is sometimes necessary to test materials at temperatures that simulate their intended end-use environment. The ASTM C297 test method can also be conducted at elevated or reduced temperatures using a thermal chamber.

The test procedure involves cutting test specimens from sandwich panels and bonding their faces to aluminum blocks using an adhesive. The assembly is then pulled apart to failure using a universal test machine. The standard head displacement speed is set at 0.50 mm/min (0.020 in/min), or at a speed that produces failure within 3 to 6 minutes. Failure between the aluminum block and the sandwich structure is not an acceptable failure mode.

The specimen size for the test varies depending on the type of material being tested. For discontinuous cellular bonded surfaces, specimen geometry is based on cell size, while for continuous bonded surfaces, the minimum facing size is 625 mm2 (1.0 in2).

The data obtained from the test includes the ultimate flatwise tensile strength in MPa (psi), failure location, and modes of failure such as core failure, facing tensile failure and adhesive failure.