It is done by applying force to a material that enters it from the opposite side and causes the material to be compressed, crushed or flattened. When performing this test, the test specimen is generally placed between two plates that distribute the applied load over the entire surface of the two opposite faces, which are joined by a universal testing device that flattens the specimen. The compressed test specimen generally shortens in the direction of the applied forces and expands in the direction perpendicular to the force. Compression testing is basically the opposite of normal tension testing.

The main purpose of compression tests is to determine the behavior and response of a material under compression pressure by measuring basic variables such as stress and deformation. Using the compressive force applied to the material, the elastic modulus of the material is determined between compressive strength, yield strength, ultimate strength, elastic limit and other parameters. By understanding these various parameters and the values ​​associated with a particular material, it is possible to understand whether the material is suitable for specific applications or whether it will fail under certain stresses.

In general, a compression test for a material requires at least two mutual forces applied to compress the sample on the surface of the sample. However, apart from this basic requirement, there are many different programs that include a combination of different variables. For example, common compression tests include forces applied in different axes of the sample and test the sample at high and low temperatures. The main examples of compression tests are uniaxial, biaxial, triaxial, cold temperature, high temperature, fatigue and creep tests.

The materials to be tested in compression tests are those that generally have high compressive strength and tensile strength that take into account lower values. In fact, any material may experience some form of compressive forces depending on the area to which it is applied. For example, these tests are applied to composites, concrete, wood, stone, brick, mortar, polymer, plastic, flooring and metals.

There are a number of compression test methods developed by the American Society for Testing and Materials (ASTM) and the International Organization for Standardization (ISO). Some of these standards are as follows:

• ASTM D575-91 (2018) Standard Methods for Testing Rubber Properties in Compression
• ASTM D6641/D6641M Standard Test Method for Compressive Properties of Polymer Matrix Composite Materials Using the Combined Load Compression Compression (CLC) Test Fix
• ASTM D695-15 Standard Test Method for Compressive Properties of Hard Plastics
• ASTM E9-19 Standard Methods of Compression Testing of Metallic Materials at Room Temperature
• TS EN ISO 14126 Fiber reinforced plastic composites – Determination of aircraft compressive properties
• TS EN ISO 1856 Porous and porous polymeric materials – Determination of crushing under pressure
• TS EN ISO 844 Rigid porous plastics – Determination of compression properties

In summary, the compression test is one of the most important tests to determine the behavior of composite materials. By applying load, the mechanical properties of these materials can be changed, but measuring the compression properties is a difficult task because the material design is related to the compression properties of the material due to the applied load. It is necessary to calculate the relationship between stress and strain and use this value to determine the compressive strength and tensile modulus of the material