Flow front monitoring in liquid composite molding on polymer tooling with ultrasonic sensors

Kurzfassung

Context: Polymer liners are widely used in type IV pressure vessels. Shape-Memory-Polymer (SMP) mandrels offer major advantages in demoulding in the production of one-piece type V hydrogen tanks. Reducing scrap rates and lead times by monitoring key process parameters such as the flow front can make a significant contribution to more environmentally and economically efficient processes. Objectives: The aim of this study is to show whether ultrasonic sensors can be used on polymer moulds, how their performance compares with use on conventional metal moulds, and how thickness and polymer type affect the measurement. This will help to monitor production processes and reduce scrap rates for type IV and V pressure vessels. Methods: Three polymer materials (polyamide-6 (PA6), polyethylene terephthalate (PET) and an epoxy tooling material) in three different thicknesses are investigated. Therefore, ultrasonic sensors are attached to sheets of these materials. The sensor data is monitored live during an open mould resin infusion process. Finally, the recorded data is analysed and compared with data obtained from a reference process on metallic moulds. Results: The sensors were able to track the flow front during the infusion process on all tool materials. The drop in signal amplitude for the polymer tooling is greater than for the metal reference, allowing for higher sensitivity. Conclusion: The ultrasonic sensors used are suitable for all the materials investigated. Due to the larger amplitude drop when the flow front is detected, the polymer materials allow a higher sensitivity than the metallic reference.