Cracking me softly - the mechanics of hyperelastic Kirigami structures

Kirigami (from the Japanese kiru = to cut, kami = paper) is the ancient Japanese art of paper sculptures, and it consists of cutting and stretching a single sheet of paper. The stretch causes the cracks to open and display the decorative pattern. From the mechanical point of view, because of the cracks, a kirigami metamaterial will have lower strength than a pristine sheet. Nonetheless, the cracks will render the sheet more stretchable, hence tougher. The question is then: is there then a crack pattern that can achieve both high strength and high toughness? In this talk, I will show simulation tools that can help answer this question, based on my previous works on meshfree methods. In particular, I will present an arc-length solver able to handle very sudden snap-backs occurring in cracks propagating in soft materials under large strains. I will also show some attempts to manufacture kirigami structures with the corresponding experimental uniaxial stress-strain curves.