Continued advancements in the design and manufacture of engineered composites has allowed composite materials to work their way into the products we use everyday. The most common modern advanced composites are fiber-matrix composites and they can be manufactured with polymer, carbon, metal, or ceramic matrix and an extremely wide range of reinforcement fiber including, carbon, boron, aramid, and glass. Since composites are anisotropic materials, care must be taken in setting up and conducting bearing response tests to ensure proper specimen alignment and load application to the test sample. Specimen alignment and orientation may not be as crucial for non-aligned short fiber composites, as many exhibit quasi isotropic behavior. However, non-aligned short fiber composites should still be carefully aligned and tested in multiple orientations to ensure that manufacture processes do not induce undesired fiber alignment. All aligned fiber composites will exhibit different mechanical properties in different orientations.

Bearing response tests of composite materials help address the real life application of composites. Although the manufacturing process of composite materials is inherently flexible, allowing components with a huge range of shapes and sizes, there is a practical limit due to machine size, manpower, and facility space. Composites are also often used in conjunction with non-composite or dissimilar composite materials. Both of these issues require components to be joined together, often using mechanical fasteners. Loading of mechanically fastened composite joints creates bearing stresses within the composite materials. Testing the bearing response of composite materials is conducted in both single and double shear, by both tensile and compressive loading, using one or multiple fasteners, and the test specimen can be mated to the same or a different material. The wide range of testing conditions helps to replicate the in-field bearing response of the composite material and helps ensure the desired properties are being tested.

ASTM has developed standard test methods for testing the bearing response of composite materials. The standards provide methods that can be recreated, ensuring materials are tested in the same manner and conditions and allowing test results validation between manufactures and customers. Popular bearing response test methods are ASTM D4762 for polymer matrix composites, ASTM D5961 for bearing response of polymer matrix composite laminates, ASTM D6873 for bearing fatigue response of polymer matrix composite laminates, and ASTM D7248 for bearing bypass interaction response of polymer matrix composites using two fastener specimens.

Applicable Testing Standards

Recommended Testing Accessories