Compression tests for determination of the compression modulus and compressive strength characteristic values via
- End loading compression method to ASTM D695, DIN EN 2850 Type B, Boeing BSS 7260 Type III and IV
- Shear loading compression method to ISO 14126 Method 1, ASTM D3410, DIN EN 2850 Type A
- Combined loading compression method to ISO 14126 Method 2, ASTM D6641, Airbus AITM 1.0008
Notched compression tests for determination of the open hole compression (OHC) and filled hole compression (FHC) strength to ASTM D6484, ASTM D6742 and AITM 1.0008
Composite materials have characteristic and very different failure modes in the various loading directions. The compressive strength in the direction of the fibers is normally much lower than the corresponding tensile strength, and therefore often represents the more design-critical characteristic value. Compression tests for the characterization of material properties such as compression modulus and compressive strength of unidirectional laminates, fabrics and and fibers, as well as multidirectional laminates, therefore play an important role and mechanical testing of composites.
A wide variety of test methods and test standards are available, whereby a distinction is made among three load application principles:
- End loading compression test to ASTM D695, DIN EN 2850 Type B or Boeing BSS 7260 Type III and IV
- Shear loading compression test to ISO 14126 Method 1, ASTM D3410 or DIN EN 2850 Type A
- Combined loading compression test to ISO 14126 Method 2, ASTM D6641 and Airbus AITM 1.0008
Compression tests on composite materials place high demands on specimen preparation, the lab staff who perform the tests, and on the testing technology itself. During load application on the laminate, stress peaks and bending deformations must be avoided to be able to determine the actual compression characteristics. To detect superimposed bending deformations, many compression test standards require strain measurement on both sides in the load direction, for which strain gauges are normally used.
In addition to tests on undamaged laminates for determination of the compression modulus and compressive strength, methods for characterizing the influence of damage are used in the form of a hole.Notched compression tests such as open hole compression (OHC) to ASTM D6484 and filled hole compression (FHC) tests using an inserted screw or bolt to ASTM D6742 simulate the conditions of a composite structure with a screw or rivet. Notched compression tests are further described in industry standards Airbus AITM 1.0008 and Boeing BSS 7260 Type I.