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In the aerospace industry, surface preparation of thermoplastic (TP) composites is a critical step in ensuring the reliability of structural bonding and paint adhesion. Unlike thermoset resin composites, which naturally accept coatings through chemical affinity, thermoplastics are chemically inert and require a textured surface to achieve mechanical interlocking. BAYAB's Abrasive Waterjet (AWJ) texturing transforms an inert surface into a high-performance bonding interface, consistently yielding cohesive failures in Single Lap Joint tests.


This article analyzes why Abrasive Waterjet (AWJ) texturing is becoming the new technological standard over traditional solutions like manual sanding, laser processing, or chemical treatments.


Pièce composites thermo-plastiques à géométrie 3D complexe texturée par jet d'eau abrasif
Complex geometry TP parts textured by AWJ

1. Thermal and Physical Integrity Preservation


Unlike laser treatments that generate a detrimental Heat Affected Zone (HAZ), BAYAB's AWJ is a strictly "cold" process. It fully preserves the physico-chemical properties of the substrate without altering the polymer matrix. This complete absence of thermal stress guarantees that both fibers and resin retain their nominal mechanical characteristics.

Furthermore, abrasive waterjet texturing ensures high processing homogeneity and isotropic adhesion, eliminating any preferential orientation (texture lay) typically caused by sanding.

Compared to manual sanding, AWJ is a non-contact process. It exerts extremely low stress on the component, preserving the structural integrity of the composite substrate with an applied force of less than 2N.


Finally, BAYAB's AWJ texturing is highly tolerant of complex geometries and variations in stand-off distance between the nozzle and the treated surface, drastically simplifying industrial automation.


2. Mechanical Performance: Achieving Cohesive Failure


The industrial standard for evaluating surface preparation before bonding or painting is the water drop test. As shown in the image below, the contact angle (wettability) test yields exceptional results following the AWJ treatment.


Wettability and contact angle test before and after abrasive waterjet surface preparation
Wettability and contact angle test before and after abrasive waterjet surface preparation

This high performance is further validated by mechanical lap shear tests conducted in partnership with ENSTA Bretagne. While untreated samples exhibit poor adhesion and adhesive failure, abrasive waterjet texturing creates an optimized mechanical interlock. The process simultaneously decontaminates the surface under the action of the waterjet and generates a specific micro-roughness via abrasive particle impacts, promoting optimal mechanical anchoring. Our studies prove that maximum joint strength can be achieved, resulting in true cohesive failure during Single Lap Joint testing.


"AWJ optimizes bonding strength compared to conventional methods through controlled, homogeneous roughness combined with deep surface decontamination."

Single lap joint mechanical test showing cohesive failure vs adhesive failure on composite
Single lap joint mechanical test showing cohesive failure vs adhesive failure on composite

3. Risk Assessment of Texturing Processes


The matrix below highlights the operational risks associated with each texturing method. Abrasive Waterjet stands out due to:


  • Environmental & Health Compliance: Composite dust is instantly confined and captured in the water before filtration.

  • Zero Thermal Risk: Absolutely no localized overheating or matrix degradation.

  • Seamless Scalability: High adaptability for robotic and automated industrial integration.


Industrial risk matrix comparing manual sanding, laser HAZ, and abrasive waterjet texturing
Industrial risk matrix comparing manual sanding, laser HAZ, and abrasive waterjet texturing

Conclusion: The Industrial Standard for High-Performance TP Composites



In conclusion, Abrasive Waterjet (AWJ) texturing stands out as the breakthrough technology for thermoplastic surface preparation. Where conventional methods like laser and sanding reach their thermal or mechanical limits, the BAYAB solution guarantees:

  • Maximum Adherence: Systematic cohesive failure in Single Lap Joint testing.

  • Total Structural Integrity: A cold process with zero HAZ and negligible mechanical stress ($<2\text{N}$).

  • Sustainable Operations: 100% chemical-free and a clean, dust-free work environment.

  • Process Homogeneity: Straightforward robotization, even on highly complex components.


Secure your next-generation structural assemblies with a repeatable, high-precision texturing process.

With the increasing share of composites in aircraft—projected at a 5.5% CAGR between 2021 and 2026—the maintenance, repair, and overhaul (MRO) of composite materials is becoming a critical challenge for the aerospace industry. Traditional repair methods, including bonded and riveted repairs, face significant technical hurdles.


In this article, we explore the benefits of Abrasive Waterjet Machining (AWJM) as an innovative solution for composites repair machining of aerospace composite structures.


Bonded Repairs: A Reliable Alternative


Aircraft composite structures can suffer various defects during production (lay-up issues, curing cycles, delamination) or in-service (impact damage, fatigue, corrosion). Repairing these flaws is vital to ensuring safety, structural integrity, and aerodynamic performance.


Bonded repairs require a strategic machining step—typically step-sanding or taper-scarfing—which is traditionally performed manually. However, manual sanding presents several drawbacks: it generates hazardous airborne dust, posing health risks to operators, and lacks the precision required, often leading to excessive material degradation and increased waste.


Abrasive Water Jet : A Breakthrough for Composite Repair Machining


Abrasive Waterjet Machining offers a superior alternative to conventional methods for aerospace composite repairs. Its key advantages include:


1. Precision and Versatility:

  • Complex Geometry: Ability to machine intricate shapes and difficult-to-access areas (e.g., lower wing skins).

  • Structural Integrity: A "cold" process that prevents thermal damage, preserving the fiber and matrix properties by eliminating any Heat Affected Zone (HAZ).


2. Environmental and Sustainability Standards:

  • Dust-Free Process: Composite dust is instantly confined and evacuated by the water recovery system, ensuring a clean workspace.

  • Waste Reduction: High-precision machining significantly minimizes scrap rates.


3. Cost-Efficiency and Turnaround Time (TAT):

  • Reduced Costs: Improved accuracy leads to fewer rejects and lower material costs.

  • Operational Readiness: AWJM is 3 to 9 times faster than manual methods, drastically reducing Aircraft on Ground (AOG) time.


4. Enhanced Working Conditions:

  • Health and Safety: Significant reduction in operator exposure to toxic composite particles.

  • Ergonomics: Automation reduces the physical strain associated with manual sanding.


A Qualified and Certified Process


Abrasive Waterjet Machining is an innovative and highly effective solution for aerospace maintenance. By offering enhanced precision, flexibility, and sustainability, it addresses the limitations of traditional repair techniques.

This technology is currently the only solution worldwide qualified and certified by AIRBUS for Carbon/Epoxy structures on the A350 (AIPI/AIPS 03-08-004 and SRM). It is also approved by the AIA (Clermont-Ferrand) for all carbon composite airframes within the French Air Force fleet.

Machine Reply de Bayab en cours d'usinage de réparation sur avion
Composites repair maching by REPLY.5 / RepairJet

The Future of Automated Composite Repair


As the utilization of composites continues to grow, the robotization of repair techniques will be a cornerstone of the future of aerospace maintenance. At BAYAB Industries, we innovate daily to lead this transformation and provide the industry with next-generation automated solutions.


Introduction


The benefits of using composite materials in numerous industrial sectors are well-established. Their advantages such as:

  • Strength,

  • Weight,

  • Durability,

  • Corrosion resistance,

make composite materials a prime choice for certain applications (Aeronautics, Wind Energy, Rail, Nautical, Space, etc.). However, their growing adoption raises a question: how to give them the desired geometry? How to machine them efficiently?



Traditionnal Machining Methods: Advantages and Limits

There are two main methods to date for machining composite materials. Depending on the application, whether in production or service, one or the other will be favored :


  • Manual Sanding : This method is very simple to impletment and adaptative with the human eye but has numerous limitations :

    • 🚫 Imprecise: Entirely dependent on the operator's skill

    • 🚫 Dangerous: Releases toxic dust

    • 🚫 Arduous: Physically demanding

    • 🚫 Inconsistent: Difficult to reproduce


  • Robotic Machining with Shaped Tooling : This method significantly overcomes the limitations of manual sanding by using a CNC machine but, in contrast to sanding, brings many new significant constraints:

    • 🚫 Costly : Each shape requires its own tooling for part conformity. This has a strong impact on small series or large volume parts.

    • 🚫 Not adaptive : Any variation in the shape of the piece requires a new program.



How to develop an intermediate solution that combines the advantages of each method while erasing their limitations ?


For a machining robot to adapt to a part not conformed by tooling, one must either:


  • Adapt the trajectory continuously with active compliance. Active compliance implies low travel speeds so that the system has time to react, and therefore is suited for extensive processes like sanding.

  • Adapt the trajectory to the actual geometry of the part by 3D scanning in the robot's frame of reference. For fine tools like milling, laser, or abrasive water jet, robotic machining assisted by 3D scanning is much more appropriate.



BAYAB Industries' Vision : Simplifying the Use of 3D Scanning to Optimize Tool-less Robotic Machining

BAYAB Industries has been innovating in the machining of composite materials since 2007. Indeed, the company developed and demonstrated the interest in abrasive water jet machining. The qualification/certification of this new process by AIRBUS and the French Air Force (AIA CF) for the bonded repair of composites proves its techno-economic relevance and robustness (read our article).


In 2020, BAYAB moved from 2-axis machining (without the need to adapt to the geometry of the part) to 6-axis machining (involving adapting the trajectory to the actual geometry).


BAYAB has therefore developed in-house the machines and software allowing for a complete system simple to use for scanning the actual part :


  • Simply : The part is first scanned from a distance by a fixed scanner that locates the part in the robot's environment and provides its overall shape to +/-20mm (Figure 1 and Figure 2)


  • Wide-angle 3D scanning of the robotic environment and the part
    Meshing of the robotic environment by SYASCAN

    Automatically : The global scan is used to automatically generate a precise scanning trajectory carried by the robot


 Recognition or selection of the part after 3D scanning of the robotic environment
Automatic recognition or selection of the aera of interest by SYASCAN

  • Quickly : The robot scans the part in 20min/m² (Figure 3)


Accurate 3D scanning with ARTEC carried by a Stäubli robot
Accurate robotic scanning controlled by SYASCAN

  • Consistency : The structured light projection scanner adapts well to all surfaces (matte or shiny, plain or textured, dark or light)

  • Accuracy : The accuracy reaching 0.03mm is sufficient to control the machining of composite plies

  • Intuitively: 3D scanners equipped with cameras capture color at the same time as geometry, simplifying the subsequent positioning of machinings (Figure 4)

    Digital display of the 3D scan with texture of the part
    Figure 4 : Display and processing of the textured digital twin of the part by SYASCAN


Examples of Use :


  • Repair machining of a wind turbine structure for ENGIE GREEN

Robotic cell assisted by 3D scanning for machining wind turbine blades


  • Repair machining of a removable part of a military aircraft

Machining of composite plies on a military part


  • Production machining to smooth the shape of a composite mold

Smoothing of a composite mold by abrasive water jet robotic machining

Conclusion


In conclusion, the world of composite material machining is on the brink of a revolution. BAYAB Industries innovation in robotic machining assisted by 3D scanning not only promises significant improvements in accuracy and efficiency but also ease of task execution for operators.


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