Multi-Stage Consolidation Strategy to Improve Impregnation Quality in Thermoplastic UD Tapes

Incomplete impregnation is a remaining challenge in the production of thermoplastic unidirectional (UD) tapes, particularly for the melt impregnation. This study investigates an approach analogous to multi-stage die impregnation by re-calendaring partially impregnated UD thermoplastic tapes, where different closing forces under controlled processing conditions are used to enhance impregnation quality. In this work, polypropylene–carbon fiber (PP-CF) tapes with a width of 20 mm and a thickness of 400 µm were produced by using an Xplore UD Tape Line with a closed pultrusion die. As a model sample, these tapes were deliberately produced under conditions expected to result in partial impregnation by setting the die pressure and pultrusion rate accordingly. To improve impregnation, the tapes were subsequently subjected to calendaring with different nip force passes in a different line, thereby mimicking a staged or multi-die consolidation approach. Results show that calendaring induces pronounced geometric reconfiguration accompanied by improved impregnation quality. Tape thickness was reduced by up to approximately 65%, while tape width increased by up to approximately 70%, indicating effective lateral spreading under compressive and shear stresses. Optical microscopy of polished cross-sections revealed a reduction of dry fibre regions and improved resin continuity within inter-filament gaps at intermediate calendaring nip force. Density-based fiber volume fraction of the tape measurements showed only a slight increase in the range of 2–3%, suggesting that consolidation was governed primarily by fibre rearrangement and spreading rather than significant resin squeeze-out. The findings provide practical insights into how the calendaring unit of a thermoplastic tape manufacturing line can be adapted for multi-stage consolidation, offering improved impregnation quality in thicker thermoplastic tapes that are more prone to impregnation defects. This approach may also serve as a bridge solution when the pressure build-up is limited.

You have full access to the following eBook

Read eBook

Info:

Periodical:

Solid State Phenomena (Volume 387)

Pages:

85-93

DOI:

https://doi.org/10.4028/p-ol0WyU

Citation:

Cite this paper

Online since:

April 2026

Authors:

Oguz Eryilmaz, Onur Yuksel, Maissaloun El-Jakl, Nursel Karakaya, Guralp Ozkoc*, Baris Caglar

Keywords:

Multi-Stage Consolidation, Process Optimization, Thermoplastic Composites, UD Tape

Funder:

The publication of this article was funded by the Delft University of Technology 10.13039/501100001831

Export:

RIS, BibTeX

Permissions:

Creative Commons CC BY 4.0

Citation:

* - Corresponding Author

References

[1] Schaefer, Y.T., L. Raps, and A.R. Chadwick, Ultrasonic and micrograph-based quantification of material characteristics for in-situ AFP composite structures. Journal of Thermoplastic Composite Materials, 2024. 38(3): pp.933-949.

DOI: 10.1177/08927057241261339

Google Scholar

[2] Fricke, D., L. Raps, and I. Schiel, Prediction of warping in thermoplastic AFP-manufactured laminates through simulation and experimentation. Advanced Manufacturing: Polymer & Composites Science, 2022. 8(1): pp.1-10.

DOI: 10.1080/20550340.2021.2015212

Google Scholar

[3] Yassin, K. and M. Hojjati, Processing of thermoplastic matrix composites through automated fiber placement and tape laying methods: A review. Journal of Thermoplastic Composite Materials, 2017. 31(12): pp.1676-1725.

DOI: 10.1177/0892705717738305

Google Scholar

[4] Hopmann, C., et al., Investigation of the influence of melt-impregnation parameters on the morphology of thermoplastic UD-tapes and a method for quantifying the same. Journal of Thermoplastic Composite Materials, 2019. 34(9): pp.1299-1312.

DOI: 10.1177/0892705719864624

Google Scholar

[5] Moradi, A., et al., Technology for lateral spreading of fibre bundles for applications in manufacturing thermoplastic composites. Composites Part A: Applied Science and Manufacturing, 2023. 167: p.107422.

DOI: 10.1016/j.compositesa.2022.107422

Google Scholar

[6] Garofalo, J. and D. Walczyk, In situ impregnation of continuous thermoplastic composite prepreg for additive manufacturing and automated fiber placement. Composites Part A: Applied Science and Manufacturing, 2021. 147: p.106446.

DOI: 10.1016/j.compositesa.2021.106446

Google Scholar

[7] Talabi, S.I., et al., Fiber orientation and porosity in large-format extrusion process: The role of processing parameters. Composites Part A: Applied Science and Manufacturing, 2025. 194: p.108891.

DOI: 10.1016/j.compositesa.2025.108891

Google Scholar

[8] Wang, J., F. Song, and M. Yu, Unidirectional continuous fiber-reinforced polypropylene single-polymer composites prepared by extrusion–calendering process. Journal of Thermoplastic Composite Materials, 2019. 35(3): pp.303-319.

DOI: 10.1177/0892705719886898

Google Scholar

[9] Yuksel, O., et al., Saturated transverse permeability of unidirectional rovings for pultrusion: The effect of microstructural evolution through compaction. Polymer Composites, 2024. 45(7): pp.5935-5952.

DOI: 10.1002/pc.28171

Google Scholar

[10] Clancy, G., et al., In-line variable spreading of carbon fibre/thermoplastic pre-preg tapes for application in automatic tape placement. Materials & Design, 2020. 194: p.108967.

DOI: 10.1016/j.matdes.2020.108967

Google Scholar

[11] Kobler, E., et al., Modeling the anisotropic squeeze flow during hot press consolidation of thermoplastic unidirectional fiber-reinforced tapes. Journal of Thermoplastic Composite Materials, 2023. 37(8): pp.2775-2801.

DOI: 10.1177/08927057231214458

Google Scholar