Johannes Mitsch, Bastian Schäfer, Jan Paul Wank, Luise Kärger

In Material Forming: ESAFORM 2024; Materials Research Forum LLC, 2024; pp 457–466, Considering the viscoelastic material behavior in a solid-shell element for thermoforming simulation

Abstract:

To predict manufacturing effects in the thermoforming process for fiber reinforced
plastics the Finite Element Method is widely used. Most macroscopic simulation methods are
based on conventional two-dimensional shell elements which are not capable of modeling the
material behavior in thickness direction using constitutive equations. At the same time, standard
three-dimensional element formulations are not suitable for the forming simulation of thin textiles
due to numerical locking phenomena and the lack of a possible membrane-bending-decoupling.
Previous studies focused on a specialized solid-shell element formulation which provides
anisotropic but purely elastic material modeling. Since purely elastic approaches cannot accurately
describe the deformation behavior in the thermoforming process, the provided element formulation
is enhanced to rate-dependent viscoelastic material modeling. Numerical studies are carried out
that reveal that the membrane-bending-decoupling is preserved for the viscoelastic material model.
Virtual coupon tests demonstrate the rate-dependent material behavior in the solid-shell element.
The obtained results show that the general approach of the viscoelastic material behavior within
the solid-shell element is suitable to address out-of-plane phenomena in thermoforming
simulations.