# Testing

In order to evaluate Laminar Jamming Structures, we present some empirical tests that may help you quantify and characterize the performance of the jamming structure.

#### Bending Test

This test was performed in Narang et al (2018).

In 3-point bending testing done in a universal materials testing device (e.g. Instron), important comparisons between properties of Laminar Jamming Structures when vacuum is on or off can be drawn. The structures were placed on the fixture according to the setup (left image) and loaded until a maximum displacement was achieved. Force and displacement measurements were simultaneously recorded.

The mechanical behavior of LJS can be summarized by the image in the right. When vacuum is off, the structure has low bending stiffness, which is proportional to the slope of the curves. When vacuum is on, the structure has three deformation regimes. In pre-slip, the bending stiffness is maximal and constant. After the first critical load, the structure enters the transition regime, in which the layers begin to slip and the bending stiffness decreases. Note that the first critical load corresponds to the yield point. After the second critical load, the structure enters full-slip, in which the layers have slipped at all possible points along their interfaces. The bending stiffness is minimal and constant. When slip occurs, energy is dissipated to friction between the layers, and the structure behaves plastically.

In the experiment above, the effect of the number of layers and of vacuum pressure on the mechanical behavior of the LJS is also displayed, illustrating the different ways in which properties such as stiffness and maximum yield can be tuned.

The 3-point bending test can also be replicated in a classroom setting with calibration weights, for purposes of qualitatively assessing the changes in LJS's stiffness in a simple way. In the video below, you can see a demonstration of this easily replicable test.