ASTM D3039 describes the standard method for tensile testing polymer matrix composites. It covers test methods for a wide range of specimen dimensions as well as many different testing configurations. In this application we tested carbon fiber specimens. The specimens were prepared with tabbed ends that allowed for a secure grip on the specimen and ensured that breaks occurred within the gauge length and not in the jaw face. Testing was performed at both high (85° C) and low (-60° C) temperatures.
For this test, we used a 5985 floor model system because it is designed for tensile testing applications. To test the specimens at the required temperatures, we used an environmental chamber with a range from -80° C to 350° C. This chamber allowed us to run tests at 85° C using the internal heating coils and then at -60° C by piping in liquid nitrogen. Before starting the test we placed the specimen in 250 kN precision mechanical wedge grips, attached our clip-on extensometer, and waited for the chamber to reach the set temperature. When testing far below or above ambient temperatures, polymer composites will often expand or contract, putting the specimen in tension or compression as the temperature changes. The 5900 Series frames used with Bluehill® 3 Software come with a specimen protect feature that allows you to set a load threshold that won't be exceeded until the test is started. Additionally, we used the optional specimen alignment device to ensure optimal alignment of the specimen in the jaw faces, since offset loading can greatly effect tests results.
We successfully tested the specimens using this setup and Bluehill 3 software calculated the modulus, maximum load, tensile strength, and strain at break.