Circumferential shear test method and apparatus for a sandwich structure

A test fixture for characterizing circumferential shear properties of a sandwich structure test specimen having an arcuate shape, comprising:

• an outer fixture to which a test load is applied and configured to be coupled to an outer load plate having an arcuate shape and attached to an outer face sheet on an outer side of a test specimen including a core, an inner face sheet, and formed in an arcuate shape defining a center of curvature, the outer fixture being rotatably mounted on a central pin coaxial with the center of curvature, the outer fixture including a rocker arm extending outwardly;
• a side plate for mechanically coupling the side of the outer fixture to he side of the outer load plate and transferring the test load from the outer fixture to the outer load plate;
• a pair of load arms positioned on opposite sides of the outer fixture and being coupled to an inner side of the test specimen, the load arms extending in a direction opposite the rocker arm and being rotatably mounted on the central pin;
• and the load arms and the outer fixture being configured such that application of a test load to an end of each one of the rocker arm and the load arms causes rotation of the rocker arm and the load arm about the central pin producing circumferential movement of the inner face sheet and the outer face sheet relative to one another in response to rotating the rocker arm and the load arm, and inducing a circumferential shear load in the test specimen.

A method of determining circumferential shear properties of an arcuate test specimen, comprising the steps of:

• mechanically coupling a side plate to an end face of an outer load plate and an end face of an outer fixture having a rocker arm;
• the outer load plate having an arcuate shape and being attached to an outer side of a test specimen, the test specimen having an arcuate shape defining a center of curvature, the outer fixture being rotatably mounted on a central pin coaxial with the center of curvature;
• mechanically coupling an inner side of the test specimen to an inner fixture rotatably mounted on the central pin and having a load arm extending in a direction opposite the rocker arm;
• applying a test load to each end of the rocker arm and the load arm;
• rotating the rocker arm and the load arm in opposite directions about the central pin;
• transferring, using the side plate, the test load from the outer fixture to the outer load plate;
• producing circumferential movement of the inner side and the outer side relative to one another in response to rotating the rocker arm and the load arm;
• and inducing a circumferential shear load on the test specimen in response to producing circumferential movement.