We present the derivation details necessary for simulation of thin shells with finite strains based on the Kirchhoff-Love assumptions. With an eye towards cloth simulation, we combine this with a nonlinear orthotropic constitutive model framework. We leverage a conforming spatial discretization using Catmull-Clark subdivision surfaces to ensure convergence under refinement, which we confirm by numerical experiments. The dynamics are handled in a fully implicit fashion to allow for large timesteps and solution of quasistatic problems.

Accurate constitutive modeling and parameter estimation for woven fabrics is essential in many fields. To achieve this we first design an experimental protocol for characterizing real fabrics based on commercially available tests. Next, we present a new orthotropic hyperelastic constitutive model for woven fabrics. Finally, we create a method for accurately fitting the material parameters to the experimental data. The last step is accomplished by solving inverse problems using our Catmull-Clark subdivision finite element discretization of the Kirchhoff-Love equations. Through this approach we are able to reproduce the fully nonlinear behavior corresponding to the captured data with a small number of parameters while maintaining all fundamental invariants from continuum mechanics. The resulting constitutive model can be used with any discretization and not just subdivision finite elements, which we demonstrate by providing an alternate implementation based on simple triangle meshes. We illustrate the entire process with results for five types of fabric and compare photo reference of the real fabrics to the simulated equivalents.