136 research outputs found
Shape morphing Kirigami mechanical metamaterials
Mechanical metamaterials exhibit unusual properties through the shape and movement of their engineered subunits. This work presents a new investigation of the Poisson’s ratios of a family of cellular metamaterials based on Kirigami design principles. Kirigami is the art of cutting and folding paper to obtain 3D shapes. This technique allows us to create cellular structures with engineered cuts and folds that produce large shape and volume changes, and with extremely directional, tuneable mechanical properties. We demonstrate how to produce these structures from flat sheets of composite materials. By a combination of analytical models and numerical simulations we show how these Kirigami cellular metamaterials can change their deformation characteristics. We also demonstrate the potential of using these classes of mechanical metamaterials for shape change applications like morphing structures
Virtual Testing of Experimental Continuation
We present a critical advance in experimental testing of nonlinear
structures. Traditional quasi-static experimental methods control the
displacement or force at one or more load-introduction points on a structure.
This approach is unable to traverse limit points in the control parameter, as
the immediate equilibrium beyond these points is statically unstable, causing
the structure to snap to another equilibrium. As a result, unstable
equilibria---observed numerically---are yet to be verified experimentally.
Based on previous experimental work, and a virtual testing environment
developed herein, we propose a new experimental continuation method that can
path-follow along unstable equilibria and traverse limit points. To support
these developments, we provide insightful analogies between a fundamental
building block of our technique---shape control---and analysis concepts such as
the principle of virtual work and Galerkin's method. The proposed testing
method will enable the validation of an emerging class of nonlinear structures
that exploit instabilities for novel functionality
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