Stress Conversion Experiments

Depending on the design of our machines, stress conversion, or the conversion of an applied stress from one direction to another plane can be achieved quite efficiently. Most constrained materials when subjected to a load, apply a small portion of this load in the other direction, due to displacement changes caused by Poisson's effects. However, MACs can be designed to not only transfer the load efficiently (1:1), but also in whatever direction the designer warrants. The degree of this stress conversion can also be tailored depending on the lay-up of the MAC composite.

Applications such as launch lock loads using MAC materials for space applications can therefore enable a low energy release of a system that normally would have a very high amount of stored energy prior to launch. Other potential applications are locking mechanisms, fasteners, gaskets, end fittings, joints, clutch systems, brakes and high performance tires.

In order to verify the behavior of our theoretical designs, we have designed a unique Instron test fixture that allows us to apply shear stresses on our macterial as we measure the compressive stress created perpendicular to the applied load. Our testing is performed on both prototype and extruded machine composites.

Instron test fixture was developed in order to measure vertical-to-lateral stress conversion. Photograph shows prototype being tested in a double lap configuration coverting shear to compressive stresses.	Graph shows the force-force behavior of a 5 celled prototype machine composite with a 20 lb preload. As shown, the stress conversion behavior of the MAC is approximately 1:1.