A Study on Through-the-Thickness Heating in Continuous Ultrasonic Welding of Thermoplastic Composites

Continuous ultrasonic welding is a promising technique for joining thermoplastic composites structures together. The aim of this study was to gain further insight into what causes higher through-the-thickness heating in continuous ultrasonic welding of thermoplastic composites as compared to the sta...

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Bibliographic Details
Published in:Materials 2021-11, Vol.14 (21), p.6620
Main Authors: Jongbloed, Bram C P, Teuwen, Julie J E, Benedictus, Rinze, Villegas, Irene Fernandez
Format: Article
Language:English
Subjects:
Adhesive bonding
Aerospace industry
Composite materials
Conduction heating
Energy
Experiments
Heat
Heat flux
Heat generation
Heat transfer
Polymers
Temperature
Thermocouples
Thermoplastic composites
Thickness
Ultrasonic welding
Vibration
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Summary:Continuous ultrasonic welding is a promising technique for joining thermoplastic composites structures together. The aim of this study was to gain further insight into what causes higher through-the-thickness heating in continuous ultrasonic welding of thermoplastic composites as compared to the static process. Thermocouples were used to measure temperature evolutions at the welding interface and within the adherends. To understand the mechanisms causing the observed temperature behaviours, the results were compared to temperature measurements from an equivalent static welding process and to the predictions from a simplified heat transfer model. Despite the significantly higher temperatures measured at the welding interface for the continuous process, viscoelastic bulk heat generation and not thermal conduction from the interface was identified as the main cause of higher through-the-thickness heating in the top adherend. Interestingly the top adherend seemed to absorb most of the vibrational energy in the continuous process as opposed to a more balanced energy share between the top and bottom adherend in the static process. Finally, the higher temperatures at the welding interface in continuous ultrasonic welding were attributed to pre-heating of the energy director due to the vibrations being transmitted downstream of the sonotrode, to reduced squeeze-flow of energy director due to the larger adherend size, and to heat flux originating downstream as the welding process continues.
ISSN:1996-1944
1996-1944
DOI:10.3390/ma14216620