This test gives a basis for evaluating the load-bearing capability of a sandwich structure when loaded in compression. The specimen should be at least 50 mm wide and the length should be at least eight times its thickness. The ends of the specimen need to be perfectly flat and are often mounted in resin to ensure absolute flatness.

Strain gauges should be bonded to the two composite skins of the sandwich structure and the strains should be within 10% of each other.

The compressive strength of the sandwich structure is determined using:

Where P is the maximum force and t is the skin thickness.