10:50
Session 9: Modelling and Characterisation of AFP
Chair: Paul Weaver
10:50
20 mins
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Generative Geometric Approach for Structured Meshing of AFP‑Manufactured Composite Parts: Geometry‑Driven Modeling and Validation
Willian dos Santos Pinto, Juan Manuel Garcia, Christian Fagiano, Cédric Huchette, Alain Rassineux
Abstract: Automated fiber placement (AFP) is a manufacturing process widely employed on aeronautical sector. This process involves a robotic arm that lays down pre-impregnated tows, thereby enhancing automation, accuracy and repeatability in manufacturing of composite parts. In addition, AFP allows a bigger possibility of design, including components with non-conventional placement path. Nevertheless, despite these advantages, two types of singularities are inherently generated during the AFP manufacturing process: gaps and overlaps. These singularities must be considered on the part design since they impact the mechanical performance of the final product. Consequently, modeling strategies to predict the behavior of structures with the presence of singularities is needed in order to optimize the AFP part design. This work aims to develop a strategy to mesh the AFP composite parts based on the placement path. The mesh method, called Generative Geometric Approach, uses the coordinates of robot trajectory to reconstruct the AFP structure mesh resulting in a structured and conformal mesh. Some geometric aspects intrinsically emerge from this method, such as ply waviness, void regions and local thickness variation. This method, which is purely based on the geometric path, leads to discrepancies between the mesh geometry and the final AFP part, as thermo-mechanical effects are not considered. Therefore, a geometric validation is carried out on the model by comparing it with imaging technique observations. This comparison reveals whether the model over- or underestimate ply waviness and/or local thickness variation, allowing the model to be adapted to best represent the AFP composite geometry. Conversely, finite‑element analysis highlights how the geometry influences the kinematic response induced by ply waviness and local thickness variations, emphasizing the need to use an accurate geometric model to obtain a representative mechanical behavior.
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11:10
20 mins
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Effects of Toolpath Direction on Temperature Gradients in Automated Fiber Placement
Rowen Burney, Ben Francis, Matthew Godbold, Ramy Harik
Abstract: Automated Fiber Placement (AFP) is an advanced composite manufacturing process that enables efficient fabrication of high-precision structures. Optimizing process parameters to enhance layup consistency and reduce defects remains challenging. Heating influences key material characteristics such as tack, void content, crystallinity, and mechanical performance. Although detailed AFP heating models exist, few address the combined effects of surface geometry and toolpath direction on heat application. This work examines how surface curvature and layup direction together shape temperature gradients during deposition. By quantifying surface curvature magnitude and direction relative to the layup path, representative temperature gradients are derived. These gradients inform the selection of optimal layup paths. The chosen paths are then integrated into an existing surface temperature prediction model. This integration achieves more uniform heating and minimizes thermal inconsistencies. The resulting method enhances part uniformity and reduces temperature-related defects such as bridging and wrinkling. By minimizing these defects, manual rework time is significantly lowered, reducing layup cycle time and improving process repeatability across components.
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11:30
20 mins
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Localised Toughening of AFP Gaps in Cryogenic Hydrogen Tanks
Jonas Appels, Daniel Stefaniak, Clemens Dransfeld
Abstract: During automated fibre placement in dome regions of hydrogen tanks, tow drops lead to triangular gaps, forming resin-rich regions that are prone to microcracking under cryogenic cycling. This research investigates a microscale toughening concept for linerless Type V cryogenic hydrogen tanks based on filling AFP gaps with polyetherimide (PEI). Tensile specimens made from HexPly 8552 with simplified gap regions showed that PEI/epoxy interphases formed around the insert, but the feature dimension depended on fibre packing and resin availability. The tensile properties did not improve, which is attributed to microstructural limitations of the gap and PEI arrangement. The results indicate that insert geometry and local contact conditions must be controlled more precisely before proceeding to a cryogenic validation of PEI-based gap filling.
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11:50
20 mins
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Enhancing Pressure Uniformity and Dwell Time Control on Complex Moulds Using Adjustable-Stiffness Compaction Rollers
Amir Hafez Yas, Mehdi Hojjati
Abstract: Automated Fiber Placement (AFP) has advanced composite manufacturing to a higher level of automation by enabling the production of large and geometrically complex structures with high repeatability and reduced waste. However, the fabrication of thermoset composites using this method is highly dependent on process parameters such as compaction pressure, contact width, and temperature, which must be precisely controlled to ensure consistent laminate quality. Insufficient bonding between layers can result in the formation of defects such as tape folding, bridging, and wrinkles. When manufacturing on complex moulds with concave or convex geometries, process parameters can vary significantly due to changes in surface curvature and roller conformity. This study aims to minimize the alteration of process parameters during AFP layup over curved molds by varying the stiffness of the compaction roller along its length through modifications to its shaft. In the first stage, finite element (FEM) simulations were conducted to determine the optimal shaft dimensions and depth levels for concave and convex mould configurations, enabling the roller to maintain uniform pressure under various curvature conditions. Based on the numerical results, polyurethane rollers with corresponding shaft geometries were manufactured to experimentally validate the numerical predictions. Pressure-sensitive films were employed to capture the pressure distribution over flat, concave, and convex surfaces, and the results were compared against the FEM outcomes. The findings demonstrate that adjusting roller stiffness by the design of its shaft geometry, pressure uniformity, and formability of the roller can be enhanced. This study highlights the crucial role of compaction roller stiffness on its formability over complex moulds and how certain designs can provide better uniformity of pressure distribution and formability of the roller.
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