# Collapse of orthotropic spherical shells

## TL;DR

This study investigates how orthotropic elastic spherical shells buckle and collapse under volume and pressure control, revealing complex behaviors and morphologies influenced by material orthotropy, with implications for understanding natural shell shapes.

## Contribution

It provides the first comprehensive analysis of buckling and collapse in orthotropic spherical shells, extending beyond isotropic cases with new numerical and experimental insights.

## Key findings

- Three distinct morphological regimes identified
- Shell buckling pathways depend on orthotropy
- Natural shell shapes may be explained by material orthotropy

## Abstract

We report on the buckling and subsequent collapse of orthotropic elastic spherical shells under volume and pressure control. Going far beyond what is known for isotropic shells, a rich morphological phase space with three distinct regimes emerges upon variation of shell slenderness and degree of orthotropy. Our extensive numerical simulations are in agreement with experiments using fabricated polymer shells. The shell buckling pathways and corresponding strain energy evolution are shown to depend strongly on material orthotropy. We find surprisingly robust orthotropic structures with strong similarities to stomatocytes and tricolpate pollen grains, suggesting that the shape of several of Nature's collapsed shells could be understood from the viewpoint of material orthotropy.