ASTM C297 is a testing specification that determines the flatwise tensile strength of the core, the core-to-facing bond, or the facing of an assembled sandwich panel. This test method can be used to provide information on the strength and quality of core-to-facing bonds and to produce flatwise tensile strength data for the core material.
A universal testing machine and the uniquely designed ASTM C297 fixture should be used to perform this test. Uniaxial tensile force is applied on a sandwich core or sandwich panel parallel normal to the plane of its faces. The force is transmitted through the specimen through thick loading bonds that are bonded to the sandwich faces or directly to the core.
Before conducting ASTM C297, it is important to read the entire specification in the relevant ASTM publication.
Note that there are slight variations depending on the type of sample selected.
Prepare at least five test specimens as described in the method. The standard specimen thickness should be equal to the thickness of the sandwich. The required minimum specimen facing areas varies for different types of core materials; follow the instructions in the standard. Measure and record the specimen length, width (or diameter), and, thickness.
Bond the specimen to the bonding blocks. Install the specimen/loading plates assembly into the test machine.
Apply a tensile force to the specimen. The suggested crosshead displacement rate is found in the testing standard.
Record force versus crosshead displacement continuously, or at frequent regular intervals.
Terminate test at rupture. Record the maximum force, the failure force, and the displacement at the moment of rupture.
Record the mode and location of failure for each specimen. The acceptable failure modes are: core failure, cohesive failure of core-facing adhesive, adhesive failure of core-facing adhesive, and facing tensile failure.