Repairing impacted thermoplastic composites using ultrasonic welding to restore the compressive strength

Master thesis (2022)

Authors

J.A. Vreeken Aerospace Engineering

Contributors

J.A. Pascoe Structural Integrity & Composites - Aerospace Engineering (mentor)
I.F. Villegas Design for Sustainability - IDE (graduation committee member)
Faculty
Aerospace Engineering, Aerospace Engineering
Copyright: © 2022 Joost Vreeken
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Published Date

22-06-2022

Language

English

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Faculty

Aerospace Engineering

Abstract

This research project investigates the potential use of ultrasonic welding as a tool to repair impact damage inside thermoplastic composites to restore the compressive strength. Compared to the already existing method, hot-pressing, ultrasonic welding could offer faster processing times, no need for dedicated tooling, smaller and lighter machinery and a smaller (heat) affected zone.
It was shown that ultrasonic welding is able to melt and re-consolidate delaminations, decreasing the damaged area. However, even when using the same welding parameters, the process showed large variations between the welds. These variations should be minimized for the process to be usable as a repair process.
Compression after impact (CAI) testing showed that welded repairs are able to fully restore the CAI strength. The re-consolidated material inside the damaged area suppresses local buckling, which normally causes premature failure. However, it was also shown that repairs with little re-consolidated material can decrease the CAI strength.