11:00
Session 2: Trajectories for Automated Fiber Placement
11:00
20 mins
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Fibre Path Planning for Automated Fibre Placement on Doubly Curved Structures
Avyadhish Malladi, Christos Kassapoglou, Daniël Peeters
Abstract: Automated fibre placement (AFP) enables manufacturing of variable-stiffness laminates through continuous spatial variation of fibre orientations. To design variable-stiffness laminates, this work involves the three-step process developed at TU Delft: stiffness optimisation using lamination parameters, fibre angle retrieval to match the optimal stiffness distribution with discrete fibre angles, and fibre path generation to convert these angles into continuous, manufacturable courses. The last step is particularly challenging, as AFP paths must satisfy design angles while adhering to manufacturing constraints such as gaps, overlaps, steering limits, and tow kinking.
The streamline analogy from fluid dynamics has been successfully applied to fibre path planning on flat and singly curved surfaces by treating fibre angle distributions as velocity fields and tracing streamlines through them. This paper extends this approach to doubly curved structures with Gaussian curvature. The extension is enabled through energy-based reference frame assignment: reference frames are computed via energy minimisation to ensure gradual spatial transitions, then aligned with a user-defined reference direction, providing consistent interpretation of fibre angles across complex curved geometries. These frames are rotated by the design angles to obtain local fibre directions. A thickness distribution is then computed through optimisation that penalises gradients perpendicular to fibre directions, reducing overlaps whilst ensuring full coverage. Continuous fibre paths are extracted by tracing streamlines through this thickness-weighted fibre field.
The extracted streamlines are parameterised as B-splines, providing a compact representation that enables evaluation of AFP manufacturing constraints including steering radius limits, fibre angle deviations, and identification of tow drop/restart locations. The methodology is demonstrated on a doubly curved geometry, with results evaluated for fibre angle deviation, steering compliance, and surface coverage, showing that the approach efficiently produces manufacturable courses with strong adherence to design intent.
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11:20
20 mins
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Layup Strategies for in-situ Automated Fiber Placement of Complex Geometries
Lukas Raps, Ashley Chadwick, Heinz Voggenreiter
Abstract: With meticulous process control and the correct manufacturing parameters, autoclave-level mechanical properties have been proven to be achievable using in-situ Automated Fiber Placement (AFP). This long-awaited result at the coupon level has spurred the use of AFP for larger structural components for structures. However, the complex geometries, particularly double curvatures required for real part geometries, present additional obstacles to the already challenging process. Without post-consolidation in a hot press or autoclave, the severity of geometry-related deviations from the ideal ply composition, namely fiber angle defects or tow-drops, remains unquantified.
This work presents a systematic derivation of layup deviations which inevitably arise for tape placement on complex geometries. Ply layup simulation software and analytical Python scripts are used and the triangular correlation between the three deviation types (steering defects, gaps/overlaps and angle deviation) is demonstrated. Layup strategies are developed specifically for the characteristics of the in-situ AFP process. Three complex example geometries are investigated as case studies: A Variable Stiffness Panel (VSP), a spherical hydrogen tank structure and a complex double-curved fuselage section. A spherical hydrogen tank section is manufactured as a validation experiment (Figure 1).
The results of this study show that increasing the number of parallel tows generally elevates angle deviation and critical steering radii while reducing area related coverage defects; an optimal design can therefore be pursued by maximizing parallel tows within process dependent limits (e.g., ±3° angle deviation for thermoset AFP). Simulation reveals that steering radii can drop to as low as 100 mm for spherical domes and 500 mm for the investigated fuselage sections, with gaps and overlaps varying from 100 mm to several meters depending on geometry and layup.
This work presents detailed correlations between layup strategy parameters and the resulting layup deviations, providing algorithms for optimized layup strategies for in-situ AFP on complex geometries.
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11:40
20 mins
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Design for Manufacturing studies for AFP manufactured Thermoplastic CFRP components at an early development stage
Julian Schuster, Maximilian Holland
Abstract: Automated Fiber Placement (AFP) is a state-of-the-art manufacturing process widely used in the aerospace industry especially for structural applications with high geometrical complexity and requirements towards mechanical properties. In addition to its near-net shape fiber deposition capability, AFP technology is particularly suitable for these challenges due to its ability to place tows along curved paths, known as "fiber steering". Rendering load path optimized fiber architecture possible, fiber steering acts as a technology enabler to allow for complex design approaches with a highly automated and accurate manufacturing technology.
Graph-based design languages offer an efficient method of generating and mapping design information along the entire workflow, from component requirements to simulation of the manufacturing environment. Graph transformation rules can automatically generate and compare a large number of variants in a reproducible format.
The presented workflow utilizes a semantic graph exchange format to feed and retrieve information from thermoplastic AFP process simulation tools. It is possible to compare different configurations of the fiber placement head, and different design and distribution methods for the placement paths using typical KPIs such as la time, material waste, fiber angle deviations or cover ratio. In addition, the investigated process chain allows to be extended to include the simulation of the hot press forming of the 2D preform. This will enable greater accuracy in predicting component properties by feeding back the resulting fiber angles into CAD and structural simulation. It potentially reduces tolerances for inaccuracies in the manufacturing processes and provides a concrete basis for the decision-making processes in an early design stage. Furthermore, the automated workflows may eventually be integrated into domain-specific AI applications for thermoplastic AFP.
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12:00
20 mins
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Continuous Trajectory Generation for the Automated Manufacturing of Super-Ellipsoidal Composite Pressure Vessels
Gregorio Ferreira, Shahrzad Daghighi, Giovanni Zucco, Paul Weaver
Abstract: The need for lightweight, high-performance composites has driven the development of advanced automated fibre placement techniques. However, the manufacturing of doubly-curved structures with non-conventional tow trajectories presents significant challenges in terms of path planning and trajectory generation for robotic systems.
This work proposes a methodology for generating continuous robotic trajectories for the automated manufacturing of a super-ellipsoidal composite vessel with non-conventional tow trajectories using carbon-thermoplastic tape deposition. The proposed methodology addresses those challenges by establishing a systematic framework that converts structural design concepts into executable robotic trajectories for a 6-DOF industrial robot. The approach employs high-order interpolation spline functions combined with a local Darboux frame [1] to ensure smooth and continuous path generation across the curved surfaces of the vessel. Starting from the analytical design of super-ellipoidal geometries with non-conventional tow steering [2, 3], the algorithm generates continuous paths for each manufacturing layer, accounting for the complex curvature variations inherent to super-ellipsoidal geometries. The methodology accounts for tape width and examines critical manufacturing concerns through a literature-based analysis of common defects in automated tape laying processes. Feasibility evaluation of the generated steered trajectories identifies critical regions most susceptible to these manufacturing challenges. The methodology considers tape width, and critical manufacturing concerns are discussed based on existing literature through an analysis of common potential defects that may arise during the automated tape laying process. The feasibility of the generated steered trajectories is evaluated to identify critical regions where these manufacturing challenges are most likely to occur.
Keywords: Non-conventional composite vessels; Path planning; Darboux frame; Laser-assisted tape placement; Automated manufacturing.
[1] Cui, L., & Dai, J. S., 2010. A Darboux-frame-based formulation of spin-rolling motion of rigid objects with point contact. IEEE Transactions on Robotics, 26(2), 383-388.
[2] Daghighi, S and Weaver, PM. 2024. Nonconventional tow-steered Pressure Vessels for Hydrogen Storage, Composite Structures, 334.
[3] Daghighi, S, Zucco, G and Weaver, PM. 2023. Design methods for variable-stiffness super-ellipsoidal pressure vessels under thermomechanical loading. AIAA Journal 61 (1), 475-488.
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