Coupled Electro-Thermal and Mechanical Simulation of Radio-Frequency Welding of ETPU Bead Foams : A Multiphysics Approach and Its Experimental Validation

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Dippold, Marcel ; Scheiber, Michael ; Ruckdäschel, Holger:
Coupled Electro-Thermal and Mechanical Simulation of Radio-Frequency Welding of ETPU Bead Foams : A Multiphysics Approach and Its Experimental Validation.
In: Macromolecular Theory and Simulations. Bd. 34 (2025) Heft 6 . - e00075.
ISSN 1521-3919
DOI: https://doi.org/10.1002/mats.202500075

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Abstract

Radio-frequency (RF) welding offers a promising, energy-efficient alternative to conventional steam-chest molding (SCM) for processing thermoplastic bead foams. This study presents a coupled electro-thermal and mechanical simulation model to predict the welding behavior and mechanical performance of expanded thermoplastic polyurethane (ETPU) bead foams. The model, implemented in COMSOL Multiphysics, incorporates temperature-dependent dielectric and mechanical properties. The electro-thermal simulation predicts spatial temperature distributions during RF welding and is validated by process-integrated temperature measurements and measured RF-generator power. These local temperatures are used to predict fusion quality at bead interfaces for subsequent mechanical simulation of tensile tests. The predicted stress distribution, crack formation, and failure behavior show good agreement with experimental results obtained via digital image correlation. The model reveals that surface cooling effects limit welding quality and mechanical strength despite sufficient core temperatures. The validated framework enables virtual process optimization and serves as a digital twin for predictive design of RF-welded foam parts. Future studies will extend the approach to other thermoplastic bead foams and integrate improved material models to enhance simulation accuracy.