In this part, we are going to make mechanical metamaterials from kirigami. Kirigami is simply a sheet folding in which there are cuts. When the 2D structure is stretched, it deforms in a particular way: It can expand, retract, rotate, move out of plane,...
Here, we will make auxetics materials that are bistable.This means that the structure can take different stable structural geometries.
In the following videos, some researchers have found kirigami patterns that allow this bistability.
The challenge here, is to find an efficient way to parametrically design all these kind of structures. During Fab Academy 2018, Nicolas Decoster has developped a Vig Flex Wood Pattern Generator during week 3. We wanted to push it further and make a kirigami mechanical metamaterial pattern generator.
Carefully analysing these bistable auxetic mechanical metamaterials, we find that there is a beautiful logic behind this puzzle.
They are made of
In the figures below, here are 2 parametric designs that we would like to make. For these 2 building blocks, there are 4 parameters: l, the length of the building block, t the hinge gap, a the size of the cut, theta the cut angle.
Using a laser cutter and laserable rubber sheets (2.3 mm in thickness), we managed to make the following bistable auxetic structures: