# Limitations of curvature--induced rigidity: How a curved strip buckles under gravity

## TL;DR

This paper investigates how finite thickness and gravity influence the buckling behavior of a curved strip, revealing limitations of curvature-induced rigidity and providing quantitative thresholds for buckling prevention.

## Contribution

It offers a detailed analysis of the limitations of curvature-induced rigidity in finite-thickness sheets under gravity, including critical curvature thresholds and buckled shape descriptions.

## Key findings

- Finite thickness limits the effectiveness of curvature-induced rigidity.
- Gravity causes long strips to deform downward, reducing rigidity.
- Critical curvature depends on geometrical and material parameters.

## Abstract

The preference of thin flat sheets to bend rather than stretch, combined with results from Geometry, mean that changes in a thin sheet's Gaussian curvature are prohibitively expensive. As a result, an imposed curvature in one principal direction inhibits bending in the other: so-called curvature-induced rigidity. Here, we study the buckling behaviour of a rectangular strip of finite thickness held horizontally in a gravitational field, but with a transverse curvature imposed at one end. The finite thickness of the sheet limits the efficacy of curvature-induced rigidity in two ways: (i) finite bending stiffness acts to `uncurve' the sheet, even if this costs some stretching energy, and (ii) for sufficiently long strips, finite weight deforms the strip downwards, releasing some of its gravitational potential energy. We find the critical imposed curvature required to prevent buckling (or, equivalently, to rigidify the strip), determining the dependence on geometrical and constitutive parameters, as well as describing the buckled shape of the strip well beyond the threshold for buckling. In doing so, we quantify the intuitive understanding of curvature-induced rigidity that we gain from curving the crust of a slice of pizza to prevent it from drooping downwards as we eat.