Skip to Content

Winding vs. Placement: Why the Same Machine Produces Fundamentally Different Results

Winding vs. Placement in thermoplastic composites: Same machine, fundamentally different process
June 30, 2026 by
Alformet GmbH, Lucas Ciccarelli

the theory 

At first glance, Laser-Assisted Tape Winding (LATW) and Automated Fiber Placement (AFP) for surface structures look almost identical. The end effector – laser, compaction roller, tape feed – is the same. The motion control software shares the same kinematic logic. A flat plate is mathematically simply a tube with an infinite mandrel radius. One process is somewhat a geometric limit case of the other.

In practice, however, the quality gap between the two processes is significant, consistent – and crucially – physically justified, not due to lack of execution. Understanding why winding performs reliably better in thermoplastic in-situ consolidation than surface placement is not only academically interesting. It has direct consequences for where these technologies can be used without post-processing and what is necessary to close this gap.

The common basis – and where it ends

Both LATW and AFP in-situ consolidation operate on the same principle: A laser heats the incoming tape and the substrate surface to melt the thermoplastic matrix at the nip point, and a compaction roller immediately presses the tape onto the substrate to achieve adhesion. Heat, pressure, and speed define the process window.

The kinematics are interchangeable. The systems of AFPT – the technology platform behind Alformet's manufacturing – operate both winding and placement configurations on the same machine architecture. Process engineers program both variants with equivalent path logic. Tape material, fiber architecture, and matrix chemistry can be identical.

What changes is the geometry of the workpiece – and this one geometric difference leads to fundamentally different consolidation physics.

The winding axis: An inherent consolidation advantage

In LATW, the tape is wound under tension onto a rotating mandrel. This tension is not a side effect – it is a primary consolidation mechanism. With each deposited layer, the circumferential tension in the tape acts as a continuous, distributed compacting force that presses the freshly laid layer against the substrate and all underlying layers. The mandrel provides a rigid reaction surface. The result is a consolidation state that is active, geometrically constrained, and self-reinforcing – with each additional layer.

This is the physical core difference. In AFP surface placement, there is no winding axis. The tape is laid onto a stationary tool, and the only consolidation force comes from the compaction roller at the nip point – a brief, localized pressure event that lasts only milliseconds at typical process speeds. Once the roller has passed, the tape is left to its own devices.

The practical consequence is measurable. Research by DLR and other institutions has documented significant mechanical property losses in in-situ AFP-consolidated flat laminates compared to press-consolidated reference samples. In contrast, winding can achieve press-comparable quality without post-processing. A porosity of less than 1% is routinely achieved in LATW; in AFP surface placement, even achieving less than 2% pore content requires careful optimization of roller pressure, temperature, and speed – and published data show that even at 2,000 N compaction force and 11 m/min placement speed, 2% pore content represents more of a threshold than a comfortable baseline.

Opposite reactions to the same parameter

Perhaps the clearest example of the physical divergence of both processes is how each responds to the consolidation pressure.

In AFP surface placement, the relationship between roller pressure and laminate quality is fundamentally positive: More pressure tends to reduce porosity and improve interlaminate adhesion, as the roller force is the primary consolidation mechanism. DLR research confirms this and shows improved consolidation with increased nip-point pressure in placement configurations.

In LATW, the relationship reverses. Higher roller pressure during winding can degrade quality – it disrupts the tape tension distribution, can cause local fiber misalignments, and introduce internal stresses that affect the laminate. The winding tension already provides the necessary consolidation force. Additional roller pressure over-consolidates the system. The optimum in winding lies at significantly lower compaction loads than AFP practitioners would typically expect.

This is not a minor difference in parameter sensitivity. It reflects a structural difference in the consolidation mechanism itself. Process engineers switching between both configurations cannot simply transfer their AFP optimization logic to Winding – and vice versa – without reassessing the underlying physics.

The material issue: UD tapes were not designed for surface placement

Current commercial UD thermoplastic prepreg tapes have largely been developed and validated for Winding and autoclave-based AFP processes. In Winding, the initial void content of the tape plays a lesser role, as the mandrel tension and compaction from subsequent layers gradually eliminate the porosity throughout the winding cycle. In AFP in-situ surface placement, there is no such correction mechanism.

Research findings published in Journal of Composite Materials (Raps et al., 2024) show that the tape composition has a disproportionate impact on the AFP in-situ consolidation quality – unfavorable prepreg compositions led to up to 74% loss of interlaminar shear strength compared to the best in-situ consolidated laminates and significant losses compared to press-consolidated references. The study found that high initial porosity in the unprocessed tape – voids between densely packed fibers – cannot be reliably collapsed by a single roll pass during AFP surface placement. The fibers themselves bear the load and protect the voids from the compaction pressure.

The consequences are far-reaching: To achieve press-comparable quality from the AFP in-situ consolidation of flat laminates, not only process optimization may be required, but also a fundamental rethinking of the tape architecture – lower initial porosity, modified surface topography to improve laser energy absorption, and fiber volume contents calibrated to the short consolidation time window of a single roll pass. Some researchers are already investigating textured tape surfaces (transverse V-groove geometries) that improve laser energy absorption by up to 25%, directly addressing the thermal side of the consolidation deficit.

What this means for the manufacturing of thermoplastic composites

Can the AFP in-situ consolidation of flat thermoplastic laminates achieve the quality of press or autoclave consolidation? The current evidence suggests otherwise – at least without post-processing. Mechanical property losses of 20–30% compared to press-consolidated references are well documented in the literature and attributed to residual porosity, lower crystallinity, and the absence of the sustained consolidation pressure available during winding or in the autoclave. Winding, on the other hand, achieves in-situ press-comparable quality because the mandrel tension provides a continuous, geometrically driven compaction force that the surface deposition cannot replicate.

For structural applications – primary aerospace structures, drive shafts, pressure vessel overwraps – this distinction is crucial. LATW is a mature, validated method for high-quality thermoplastic composite pipes and profiles without autoclave or press post-processing. AFP in-situ consolidation remains a powerful technology for complex geometries, but the quality gap compared to consolidated references must be considered in the structural allowables.

At Alformet, LATW is the core process because the physics of winding supports the quality levels required for structural series production. The mandrel is not just a forming tool – it is an active participant in the consolidation. This is a process advantage that no amount of sophisticated roll pressure optimization in AFP surface placement can fully replicate.

Conclusion

The convergence of winding and placement hardware has been a true engineering achievement – it allows a machine platform to cover a wide range of geometries and applications. However, hardware convergence should not be confused with process equivalence. The winding axis introduces a consolidation mechanism – inherent tape tension against a rigid mandrel – that the surface placement fundamentally does not possess. The result is a consistent, physically justified quality advantage in LATW, reflected in porosity data, mechanical property retention, and the inverted response to consolidation pressure, which separates the two process categories.

When thermoplastic composites transition from aerospace prototype development to series production, understanding these process boundaries – not just the possibilities, but also the limitations – is what distinguishes serious manufacturing partners from technology demonstrators.

Learn how Alformet's LATW process can support your next structural composite project – get in touch.


📚 SOURCES USED:

The Airbus MFFD and the future of manufacturing thermoplastic composite materials in aviation
From Prototype to Doctrine: What the MFFD Reveals About the Future of Thermoplastic Fuselage Manufacturing (Photo Source: DLR)