ACM 7

15:40 20 mins	Towards an Automated Circular Repair Workflow for Aerospace Composite Structures through Reverse Engineering and Digital Manufacturing Arjun Chandra Shekar, Redouane Zitoune, Benjamin Trarieux, Lucas A. Hof Abstract: In the aerospace field, the repair of composite structures remains among the least automated operations within the production and maintenance chain. This process is typically performed manually, relying on operator expertise, subjective inspection, and costly component replacement. Additionally, manual milling during material removal generates hazardous particulate matter, posing health risks to operators. With the growing adoption of digital manufacturing, there is a clear need to transition such repair operations toward greater automation. Addressing this need, the present study focuses on the bonded repair of continuous-fiber thermoplastic composites and introduces a reverse-engineering-driven circular repair framework designed to establish the foundation for progressive automation in composite maintenance. Following damage detection, the proposed workflow integrated robot-assisted damage removal, human-operated surface digitization, geometric reconstruction, and additive manufacturing within a digitally assisted environment, thereby enhancing repeatability, precision, and sustainability while aligning with circular manufacturing principles. The process began with controlled machining of the damaged region to remove the defect while maintaining the structural continuity of the surrounding laminate. The machined cavity was captured through high-resolution 3D scanning, and the acquired point-cloud data was processed through reverse engineering techniques to generate a precise digital model. This digital representation enabled the creation of a tailored repair patch that seamlessly matched the cavity geometry. With this original approach, the gap between the patch and the parent geometry, arising from machining of the damaged zone influenced by the residual stress was reduced. The patch was fabricated via material extrusion additive manufacturing (MEX) using continuous carbon fiber thermoplastic feedstock and subsequently adhesively bonded to the parent substrate using an epoxy film adhesive cured under controlled temperature and pressure conditions to restore geometric integrity and load-transfer capacity. The fabricated patches demonstrated precise geometric conformity with the parent structure, validating digital repair accuracy. Although the present workflow includes partial manual operations, its digitally linked stages establish a data-driven foundation for future automation in repair processes. By restoring damaged regions using customized MEX-fabricated patches instead of replacing entire components, the framework reduces waste and extends component life, offering a sustainable approach towards automated composite repair within a circular manufacturing framework.
16:00 20 mins	Polymer Cold Spray on Composite Substrates Patrick Bailey, Wout De Backer Abstract: Cold Spray is an additive manufacturing technique that relies on heated and pressurized gas to accelerate small particles. This resulting kinetic energy transforms into plastic deformation strain through a quasi-adiabatic process, causing the particles and substrate to locally deform at their interface and adhere. Cold Spray has primarily been used for metal powder applications on varying substrates, but there are few studies on the use of polymer powders. This paper focuses on the deposition tests of different polymer powders on composite substrates, and their effects. PEEK, and PEI powders are sprayed on thermoplastic carbon fiber composites to determine if the powders deposit on the surface. The deposition is parameterized based on spray offset distance, gas temperature, and powder flow rate to determine the best parameters for bonding powder to a composite substrate. Deposition results are quantified through measuring the material added to or eroded from the substrate during the process. Cross-sectional microscopy analysis is conducted to characterize powder-substrate bonding effects. Results showed that both PEEK and PEI powder can produce deposition on composite substrates, and PEEK has the best deposition results at a gas temperature of 450 °C, with an offset of 20 mm. The best PEEK deposition parameters were used to attempt the repair of damaged thermoplastic composite substrates to restore their residual strength. Results show the Cold Spray composite repair has a lower ultimate strength restoration compared to traditional scarf repairs, however it can be used to produce a cosmetic finish.
16:20 20 mins	Automated Scarf Repair for Composite Structures Patrick Bailey, Michael Cargill, Stephen Hilton, Yug Desai, Wout De Backer Abstract: Composite scarfing is the current industry standard in repair of thermoset composites. This process requires sanding the damaged or defective composite and epoxying an undamaged fiber patch in the removed area. This highly manual and costly process can require days to complete and is subject to manufacturing errors. This paper investigates an approach to piece-wise automation of the scarf repair process. The automated setup integrates a mobile KUKA 6-axis robotic manipulator with a multi-tool end effector to perform the process. The end effector performs composite removal using a router tool, followed by epoxy deposition on the composite interface, and it uses a vacuum to pick and place a pre-made carbon fiber patch. The design and characterization of each end effector tool for creating the patch repair is described. Automated patch repair trials are conducted, starting from composite milling and concluding with patch placement. Manual patch repairs are performed to produce a comparison in structural quality. These repairs are each tested to failure under compression based on ASTM D7137. Stress analysis shows the automated patch repair is 5% weaker than manual repair, but with a reduction of around costs, and a time savings of more than 2.5 man hours when compared to manual repair.
16:40 20 mins	Contact-Based Locating of Non-Native Workpieces for Automated Patch Repair. Wout De Backer, Jacob Walker, Patrick Bailey, Michael Cargill Abstract: Composite repair of aircraft structures remains a predominantly manual and labor-intensive process that demands high precision in locating damage, removing material, and applying repair patches. While much of the recent research in this area has focused on automated damage detection, the subsequent repair operations, particularly localization, surface preparation, and patch placement, remain challenging to automate. This work presents a robotic repair system designed to address those aspects in towards automated composite patch repair on aircraft surfaces, using a contact-based locating algorithm. A robot manipulator on a mobile cart is positioned near the damaged region and provided with the approximate defect location. Using an integrated touch-probe sensor, the system performs contact-based surface mapping to accurately locate the composite substrate geometry, and establish a local coordinate frame for the repair sequence. The mapped geometry is then used to generate toolpaths for automated milling of the damaged area, ensuring material removal that conforms to the complex curvature of aircraft surfaces. Following surface preparation, the robot automatically aligns, picks, and places a pre-formed composite patch onto the repaired area using an adhesive bonding process. The full workflow, including geometric localization, damage removal toolpath planning, and automated patch placement, is presented, emphasizing the integration of tactile sensing, motion control, and process automation. Experimental trials on curved composite aircraft panels demonstrate sub-millimeter accuracy and consistent patch adhesion, validating the feasibility of this contact-based approach for adaptive, field-deployable composite repair in aerospace maintenance environments.

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