694 research outputs found
The shape and mechanics of curved fold origami structures
We develop recursion equations to describe the three-dimensional shape of a
sheet upon which a series of concentric curved folds have been inscribed. In
the case of no stretching outside the fold, the three-dimensional shape of a
single fold prescribes the shape of the entire origami structure. To better
explore these structures, we derive continuum equations, valid in the limit of
vanishing spacing between folds, to describe the smooth surface intersecting
all the mountain folds. We find that this surface has negative Gaussian
curvature with magnitude equal to the square of the fold's torsion. A series of
open folds with constant fold angle generate a helicoid
Toughening mechanisms and damage propagation in Architected-Interfaces
We investigate fracture properties of architected interfaces and their
ability to maintain structural integrity and provide stable damage propagation
conditions beyond the failure load. We propose theoretical and numerical
frameworks to evaluate the fracture properties of architected interfaces
sandwiched between two (face) materials. The microscopic geometries of these
interfaces are chosen as 2D cells--pillar, tetrahedron, and hexagon--as well as
their 3D counterparts--namely, pillar array, octet truss, and Kelvin cell. Our
model, both numerical and analytical, exhibits a high level of accuracy in
predicting the compliance before failure and failure loads. Novel results are
obtained during the damage propagation regime, indicating fulfilment of the
so-called fail-safe design. Some of the cell geometries unfold during fracture,
thus increasing the failure load and ensuring stable and controlled damage
propagation conditions
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