arXiv subjects

José Bico

Publications and source records attributed to José Bico.

4 recordsLinked to original sources

arXiv2026

Geometry and Mechanics of Ribbon Gridshells

Mechanical metamaterials exhibit anomalous properties induced from non-trivial mesoscopic constituents. Inspired from architectural and industrial structures, we introduce arrangements of long, narrow ribbons intersecting at prescribed angles as a model thin-sheet metamaterial. These ribbon gridshells are shown to display highly non-linear behavior driven by the geometric constraints, nonetheless unlike most complex mechanical systems, we are able to explicitly write out the coarse-grained governing equations and to classify their solutions in terms of the intersection patterns of the ribbons. It is shown that the structure can assume arbitrary, tunable Gaussian curvature distributions, allowing us to formulate an inverse design problem, solvable under a suitably defined local condition. An analysis of the soft modes, confirmed by experiment and numerics, reveals rich mechanics which may exhibit both a rigid and an anomalously soft behaviors.

cond-mat.soft↗

arXiv2026

Pressure and asymmetry govern the shape and stiffness of inflatables

Inflatables made of thin sheets constitute a lightweight, scalable alternative to conventional soft robots. Since sheets are essentially inextensible while offering low resistance to bending, the shape of a straight tube should be trivially set by volume maximization. We show that networks of parallel tubes made from two sheets differing in stiffness defy this expectation as their global shape is governed by the binding angle at the junctions of adjacent tubes. Through this angle, the stiffness asymmetry induces a pressure-dependent curling and stiffening of the networks. Modeling a tube cross-section as two coupled rods, we quantitatively describe the geometry and mechanics of this new class of inflatables. Our model captures unexpected mechanical features such as a stiffness scaling as the square root of pressure and a contact-induced stiffening between neighboring tubes -- challenging common assumptions on thin-sheet inflatables. Unlike prior work restricted to the high-pressure regime, the pressure-dependent description further enables multiprogrammable control over a continuous range of curvatures. Discussing a variety of examples, we finally show that networks of asymmetric tubes are a versatile platform for functional shape-morphing objects.

cond-mat.soft↗

arXiv2025

Asymmetric Bending Boundary Layer: the $λ$-test

We investigate the mechanics of two asymmetric ribbons bound at one end and pulled apart at the other ends. We characterize the elastic junction near the bonding and conceptualize it as a bending boundary layer. While the size of this junction decreases with the pulling force, we observe the surprising existence of the binding angle as a macroscopic signature of the bending stiffnesses. Our results thus challenge the standard assumption of neglecting bending stiffness of thin shells at large tensile loading. In addition, we show how the rotational response of the structure exhibits a non-linear and universal behavior regardless of the ratio of asymmetry. Leveraging the independence of the binding angle to the pulling force, we finally introduce the $λ$-test -- a visual measurement technique to characterize membranes through simple mechanical coupling.

cond-mat.soft↗

arXiv2020

Programming stiff inflatable shells from planar patterned fabrics

Lack of stiffness often limits thin shape-shifting structures to small scales. The large in-plane transformations required to distort the metrics are indeed commonly achieved by using soft hydrogels or elastomers. We introduce here a versatile single-step method to shapeprogram stiff inflated structures, opening the door for numerous large scale applications, ranging from space deployable structures to emergency shelters. This technique relies on channel patterns obtained by heat-sealing superimposed flat quasi-inextensible fabric sheets. Inflating channels induces an anisotropic in-plane contraction and thus a possible change of Gaussian curvature. Seam lines, which act as a director field for the in-plane deformation, encode the shape of the deployed structure. We present three patterning methods to quantitatively and analytically program shells with non-Euclidean metrics. In addition to shapes, we describe with scaling laws the mechanical properties of the inflated structures. Large deployed structures can resist their weight, substantially broadening the palette of applications.

cond-mat.soft↗