Lauren Dreier | Searcharxiv

arXiv2024

Beaded metamaterials

From the pragmatic to the symbolic, textiles play a prominent role in some of the most demanding yet ubiquitous scenarios, such as covering the complex and dynamic geometries of the human body. Textiles are made by repeated manipulations of slender fibers into structures with emergent properties. Today, these ancient metamaterials are being examined in a new light, propelled by the idea that their geometric structures can be leveraged to engineer functional soft materials. However, per their inherent softness, textiles and other compliant materials cannot typically withstand compressive forces. This limitation hinders the transfer of soft matter's rich shape-morphing capabilities to broader research areas that require load-bearing capabilities. Here we introduce \textit{beading} as a versatile platform that links centuries of human ingenuity encoded in the world of textiles with the current demand for smart, programmable materials. By incorporating discrete rigid units, i.e. \textit{beads}, into various fiber-based assemblies, beadwork adds tunable stiffness to otherwise flaccid fabrics, creating new opportunities for textiles to become load-bearing. We select a shell-like bead design as a model experimental system and thoroughly describe how its mechanics are captured by friction, the material properties of the constituent elements, and geometry. The fundamental characterization in this study demonstrates the range of complex behaviors possible with this class of material, inspiring the application of soft matter principles to fields that ultimately demand rigidity, such as robotics and architecture.

cond-mat.soft↗

arXiv2021

Numerical modeling of static equilibria and bifurcations in bigons and bigon rings

In this study, we explore the mechanics of a bigon and a bigon ring from a combination of experiments and numerical simulations. A bigon is a simple elastic network consisting of two initially straight strips that are deformed to intersect with each other through a fixed intersection angle at each end. A bigon ring is a novel multistable structure composed of a series of bigons arranged to form a loop. We find that a bigon ring usually contains several families of stable states and one of them is a multiply-covered loop, which is similar to the folding behavior of a bandsaw blade. To model bigons and bigon rings, we propose a numerical framework combining several existing techniques to study mechanics of elastic networks consisting of thin strips. Each strip is modeled as a Kirchhoff rod, and the entire strip network is formulated as a two-point boundary value problem (BVP) that can be solved by a general-purpose BVP solver. Together with numerical continuation, we apply the numerical framework to study static equilibria and bifurcations of the bigons and bigon rings. Both numerical and experimental results show that the intersection angle and the aspect ratio of the strip's cross section contribute to the bistability of a bigon and the multistability of a bigon ring; the latter also depends on the number of bigon cells in the ring. The numerical results further reveal interesting connections among various stable states in a bigon ring. Our numerical framework can be applied to general elastic rod networks that may contain flexible joints, naturally curved strips of different lengths, etc. The folding and multistable behaviors of a bigon ring may inspire the design of novel deployable and morphable structures

cond-mat.soft↗