Thick Thermoplastic Composite Machining: No Easy Task!
By Sébastien Louvel, composite machining expert at Daher
Making aircraft lighter is essential. But some processes should never be taken lightly.
04/30/2026
My name is Sébastien Louvel, head of the Machining Center at the Shap’in tech center, and #ExpertByDaher in composite machining.
Today, I would like to share a major milestone in our roadmap aimed at reducing aircraft weight to lower fuel consumption—and, more specifically, explain the role machining plays in this achievement.
This year, Daher’s R&D teams finalized the development of welded thermoplastic (TP) ribs. These are key structural components in wing design. Their optimized design, combined with the use of composite materials, significantly reduces weight.
These ribs consist of a large L‑shaped section and an angle bracket. Assembling them through welding eliminates the need for metallic fasteners while maintaining the required mechanical performance. Thermoplastic resin is particularly well suited to this configuration, as it can be reheated multiple times to be reworked—and welded.
The results speak for themselves: the welded TP ribs developed at Daher are around 20% lighter than their metallic counterparts. At aircraft level—on a platform such as the A320, with around thirty ribs per wing—this represents nearly 100 kg saved per aircraft.
The innovative and highly technical nature of these parts was recognized this year with a JEC Innovation Award.
Today, we are getting to the heart of the matter: machining these ribs. But this is only part of the story. We will soon show how other disciplines contributed to overcoming this technological challenge. Stay tuned.
I had already discussed thick thermoplastic machining in a previous post. The development of these welded ribs, however, brought with it a new set of very concrete challenges.
These parts can be locally up to five times thicker than standard components. We are machining a thermoplastic resin that tends to melt and clog cutting tools, and we need to re‑machine the parts after welding, which introduces additional constraints related to accessibility, clamping and vibration behavior.
To address these challenges, we had to completely rethink the entire machining process.
Cutting Tools: changing the paradigm
While thermoplastics are ideal for welding when they return to a viscous state, machining is a completely different story. Abrasive tools—widely used for thermoset composites—are not an option here. Only sharp cutting tools allow proper control of the cutting process.
Another specific feature is that machining does not generate dust, but chips that must be evacuated efficiently to prevent tool clogging and rapid process degradation.
And when machining thicknesses ranging from 12 to 24 mm, small‑diameter cutters are no longer suitable. We move to tools with diameters of 12 or 16 mm. These tools are more heavily loaded and more expensive, making monitoring absolutely essential to ensure tool life and process stability.
Different tool technologies were therefore evaluated—CVD‑coated carbide, PCD inserts, veined PCD—by analyzing their performance against several criteria: cutting conditions, vibration behavior, part quality and durability over time.
With the support of our academic partner ENSAM Angers, we also assessed the impact of various cutting assistance methods: pulsed air, water‑based lubrication, minimum quantity lubrication, and cryogenic assistance (supercritical CO₂).
In a context of thick parts and high production rates, these choices directly determine process stability, repeatability of operations and the ability to reliably industrialize these innovative products.
Tooling: challenging composite machining standards
Conventional solutions are no longer sufficient. Forget tooling systems that rely solely on vacuum clamping. Here, cutting forces can reach up to 1,000 N, requiring a robust mechanical design conceived from the outset for demanding industrial conditions.
Even with significant thickness, the parts remain highly sensitive to vibrations. Poor clamping quickly leads to degraded machining quality or even tool breakage. Vibration control becomes even more critical when targeting high‑rate production.
Every detail matters: accessibility to machining areas, tool length, tilt limits during trimming, the balance between rigidity and freedom of movement—all parameters that must be taken into account to ensure both part quality and cycle reliability.
On welded TP ribs, one of the most complex areas even has a telling name: the “mouse holes.” A concentration of geometric and vibratory constraints—and a real stress test for the process.
We naturally explored simpler or more economical tooling solutions. The results were clear‑cut: vibrations, instabilities, tool breakage.
Our industrial projection today is based on a proven tooling design, validated on numerous prototypes, guaranteeing reliability, stability and repeatability, without vibration issues or tool failures.
A machining system specifically sized for the challenge
Finally, the machining equipment itself had to be specifically sized. Standard composite machines do not offer the rigidity required to withstand such forces, nor mechanical components adapted to these constraints.
Thick thermoplastic machining requires a holistic process approach: cutting assistance, chip management, instrumentation and data collection.
Based on physical measurements taken during preliminary trials, we specified the equipment now installed at Shap’in, which is fully instrumented to prepare for future production monitoring.
There is little doubt that future commercial aircraft will incorporate an ever‑greater share of composite materials. By working on thick structural components, Daher is not taking the easy path, but actively supporting an ambitious decarbonization trajectory with concrete, robust and fully controlled industrial solutions.
👉 This type of project is a strong reminder of one essential truth: aerospace innovation is always the result of collective effort, where every discipline matters—down to the finest details of the industrial process.
Proud of the journey achieved with the Shap’in and Daher teams.
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