# Energy minimising configurations of pre-strained multilayers

## TL;DR

This paper studies the optimal configurations of pre-strained thin multilayer structures, revealing a phase transition from cylindrical to spherical shapes depending on the pre-strain strength, through theoretical analysis and numerical experiments.

## Contribution

It introduces a family of von Kármán functionals interpolating between linearised regimes and rigorously analyzes the phase transition in optimal configurations.

## Key findings

- Identification of a critical pre-strain level causing shape transition.
- Rigorous convergence results for minimizers in asymptotic regimes.
- Numerical evidence of a sharp transition at a specific parameter value.

## Abstract

We investigate energetically optimal configurations of thin structures with a pre-strain. Depending on the strength of the pre-strain we consider a whole hierarchy of effective plate theories with a spontaneous curvature term, ranging from linearised Kirchhoff to von K\'arm\'an to linearised von K\'arm\'an theories. While explicit formulae are available in the linearised regimes, the von K\'arm\'an theory turns out to be critical and a phase transition from cylindrical (as in linearised Kirchhoff) to spherical (as in von linearised K\'arm\'an) configurations is observed there. We analyse this behavior with the help of a whole family $(\mathcal{I}^{\theta}_{\rm vK})_{\theta \in (0,\infty)}$ of effective von K\'arm\'an functionals which interpolates between the two linearised regimes. We rigorously show convergence to the respective explicit minimisers in the asymptotic regimes $\theta \to 0$ and $\theta \to \infty$. Numerical experiments are performed for general $\theta \in (0,\infty)$ which indicate a stark transition at a critical value of $\theta$.