14:00
Session 3: Thermoplastic Tapes
14:00
20 mins
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Relevance of deconsolidation on the porosity of thermoplastic cfrp tubes wound with direct electrical resistance heating
Jonas von Heusinger, Yannis Grohmann, Mihai Fetecau, Jonas Naumann, Daniel Stefaniak, Clemens Dransfeld
Abstract: The Continuous Resistance Heating Technology (CoRe HeaT) is being developed at ZLP Stade by the German Aerospace Center. This heating technology enables significantly higher deposition rates during the winding process and automated fiber placement of carbon fiber (cf) reinforced thermoplastic tapes. By combining rapid material deposition with subsequent effective post-consolidation, the process aims to enhance overall productivity while obtaining high-quality composite structures. By using the Joule effect, cf tapes are being heated intrinsically in the heating zone. When the material reaches the melting point of the matrix, its morphology undergoes changes due to deconsolidation. Internal stresses are released, allowing voids within the material to expand. The aim is to create a preform with minimal porosity during the deposition of the tape onto the mold or substrate. This paper examines the effects of deconsolidation occurring during the layup process. First, a static test setup is being used to mimic the effect of Joule heating in the heating zone of an automated high rate manufacturing process. Moreover, test tubes are wound with a CoRe HeaT assisted winding machine. To assess the porosity of micrographs of static testing samples and wound tubes, a machine learning model is trained for semantic segmentation enabling void detection and characterizing void instances. Void contents of deconsolidated tapes and wound tubes are compared and the properties of voids in the wound tubes are investigated. It was observed that in wound tubes voids are more commonly found between the layers (interlaminar) rather than within the layers themselves (intralaminar). This suggests that deconsolidation has a lesser impact on the overall porosity of CoRe HeaT wound preforms compared to the voids trapped during layup at the nip point between the newly deposited tape and the substrate. The findings imply why investigating the effectiveness of compactors, supporting the high rate deposition, on preform porosities are relevant for the development of a stable CoRe HeaT winding process for the production of defect free preforms.
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14:20
20 mins
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A Quantified Comparison of Commercial CF-LMPAEK Tapes
Ashley Chadwick, Yannick Schäfer, Clara Thaldorf, Stefan Fliescher
Abstract: The desire for high-speed additive manufacturing, both Automated Fibre Placement (AFP) and 3D printing, has launched CF-LMPAEK from its release approximately five years ago to become one of the most widely-utilised materials in the development of new thermoplastic composites parts for the aviation industry. While the base polymer is currently procured from a single supplier, its conversion to a composite prepreg by any one of several manufacturing companies yields drastically different products. Commercial entities and research institutes alike must therefore ask poignant questions regarding the quality and applicability of these prepregs: How well do supplier datasheets represent their products? Are commercial tapes equivalent? Can they be substituted for one another if the need arises?
In this work, six CF-LMPAEK prepregs from four well-known suppliers are measured using different techniques and compared to one another as well as their own manufacturer-supplied datasheets. Optical microscopy is used to assess the fibre distribution, porosity, and overall homogeneity of the composite material. Measurements of prepreg width, thickness, and other properties are also performed using the TAPESCAN facility from TEXTECHNO. This facility measures properties continuously over the full length of the material spool, providing parameter resolution of 0.1m and therefore thousands of datapoints over the spool length. The prepreg spools measured in this study yielded between 1400 and 4900 datapoints.
The results of this investigation highlight that prepregs can deviate significantly from their target values and indeed each other. Nominal 59% fibre volume prepregs were recorded to exhibit vastly different median values and distributions, with some falling as low as 50%. The prepreg width was also seen to vary between products, with 12.7mm (1/2”) unidirectional tapes displaying concentrations between 12.6mm and 13.0mm. While such systematic offsets can be accounted for, it is essential to obtain accurate information on the product on hand.
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14:40
20 mins
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Flax to the Future: Processing–Structure Relationships in Continuous Natural Fiber Thermoplastic Tapes
Dimitrios Apostolidis
Abstract: This study investigates continuous manufacturing of flax fiber-reinforced thermoplastic tapes using polypropylene and polyamide 11 matrices. The effects of processing parameters on impregnation quality, microstructure, and thermal stability are analyzed, establishing correlations between resin chemistry and process conditions to optimize bio-based tape production for lightweight structural applications.
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15:00
20 mins
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Pulsed Flashlamp (HUMM3) Heating of Thermoplastic Composite Tape in In-Situ Automated Fiber Placement: Thermal Response and Physical Changes
Kasahun Niguse Asfew, Julie Teuwen, Daniël Peeters
Abstract: Thermoplastic Automated Fiber Placement (AFP) requires rapid and reliable heating to achieve proper bonding during in-situ consolidation. While laser heating is commonly used, its safety and cost drawbacks motivate interest in alternative heat sources. The HUMM3 pulsed broadband flashlamp offers a relatively safer solution, yet its effectiveness in AFP remains insufficiently studied.
This work investigates the thermal response and resulting physical changes in CF/LM-PAEK unidirectional tape subjected to HUMM3 heating. A static setup replicating AFP conditions was designed, with the HUMM3 head positioned at 34.5° and a thermal camera capturing temperature evolution of the composite tape. A full factorial Design of Experiments was used to explore three voltage levels (160, 170, and 180 V) and three pulse width–frequency combinations (3 ms–60 Hz, 2 ms–90 Hz, and 1.5 ms–120 Hz), each delivering the same energy over a heating time of 1.2 s.
Results show that, contrary to trends reported in earlier studies, pulse width and frequency do not significantly influence the tape’s thermal response when total delivered energy is held constant. Voltage is the dominant parameter influencing the thermal response. Physical-state analysis revealed a strong correlation of surface roughness and waviness, thickness change, and void content with local temperature. These changes are believed to be driven by polymer softening, fiber decompaction, internal gas pressure buildup, and local thermal gradients across the tape width.
Compared with laser heating, HUMM3 produces less severe deconsolidation, likely due to its broadband UV–VIS–NIR spectrum, which promotes partial matrix absorption and reduces temperature gradients across the tape width. This indicates that pulsed flashlamp heating may help maintain relatively smoother tape surfaces before compaction in AFP, potentially improving intimate contact and consolidation quality.
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