Inter-ply friction in unidirectional fiber-reinforced thermoplastics

Inter-ply friction in unidirectional fiber-reinforced thermoplastics: With a focus on the influence of temperature

Geschiere, Joran (TU Delft Mechanical, Maritime and Materials Engineering)

Bessa, M.A. (mentor)
Sinke, J. (mentor)
Pierik, Rens (mentor)
Krämer, Erik (graduation committee)

Delft University of Technology

Materials Science and Engineering

2022-10-24

The accuracy of hot press forming process simulations with unidirectional fiber reinforced thermoplastics is not at the desired level. Fundamental knowledge about the interactions between adjacent plies is needed to enhance predictive quality. Several mechanisms can be distinguished during hot press forming of composites. This thesis focuses on the inter-ply friction behaviour which is the resistance against inter-ply slip. The main variable investigated in this study is temperature.

In this research, an extensive friction characterization with UD C/LM-PAEK is conducted at temperatures ranging from 300 to 365 ◦C. The neat matrix material has been studied with DSC and rheometry experiments. In general, a peak response can be seen during start-up in a friction characterization experiment. This peak, or overshoot, progresses towards a steady state friction response after a slip distance of several mm. Reducing the temperature showed similar effects to increasing the sliding velocity in a ply-ply slip system. The peak during start-up increases in magnitude while the steady state response remains approximately constant. Indications of flow induced crystallisation have been observed during friction characterization around the melting point of the material. The timetemperature-superposition principle has been applied to experimental friction data. This enabled to predict the duration of the transition of peak friction response towards a steady state. Several modelling efforts have been compared to the experimental data. The accuracy of the model predictions is similar between 315 and 365 ◦C. Influences of flow induced crystallisation impede the reliability of the specific models around and below the melting point.

The research lead to useful insights in the friction behaviour at relatively low temperatures. Further research is required on the field of flow induced crystallisation for a better understanding of its role in the friction response. Further study with other materials is needed to validate the application of the time-temperature-superposition principle to predict the speed of the transition of peak friction response towards steady state.

friction
hot press forming
thermoplastic composites
temperature

http://resolver.tudelft.nl/uuid:a6503b51-75d9-47f2-80ac-b85c77a56376

2024-11-01

Student theses

master thesis

© 2022 Joran Geschiere