ASTM D7249 measures the tensile and compressive strength of various materials. A sandwich flexural test, generally used to determine the flexural strength or modulus of the material, comprises four-point flexure of flat sandwich constructions and is performed by using a universal testing machine.
Sandwich flexural test by ASTM D7249 measures the strength (tensile and compressive), stiffness, and shear modulus of a variety of materials. The core materials include multiple surfaces for different applications like continuous (foam) and non-continuous (honeycomb) materials.
Flexural tests are generally used to determine the flexural strength or modulus of the material. It is analogous to the tensile strength, however much more affordable with slightly different results. A sandwich flexural test comprises four-point flexure of flat sandwich constructions. The main aim is to produce the curvature of the sandwich plane.
The specimens are fitted with bonded strain gages (if applicable). The specimens are then placed in the Universal Test Machine with a 4-point test fixture. The specimen is perpendicularly aligned to the loading bars, and the loading bars are perpendicular to the plane of the specimen facing. A compressive force is started and it keeps going until it collapses. The basic loading configuration is four points.
Five specimens are measured for their thicknesses. Standard specimens are rectangular, with a width of 75 mm (3.0 inches) and a length of 600 mm (24.0 inches).
The following measurements can be made using 4-point flexure results
Force vs Displacement Ultimate stress limit Facing stress limit Effective tensile chord and compressive modulus Sandwich flexural stiffness Failure type