Abstract

Automated Fiber Placement (AFP) has demonstrated significant advantages in manufacturing large composite aerospace structures; however, its application to medium-scale, geometrically complex components remains limited by process planning and manufacturability constraints. This study presents a manufacturing feasibility investigation of AFP for doubly curved wind tunnel blade structures, conducted using a full-scale aerospace production cell. The work integrates reverse-engineered geometry reconstruction, process planning using virtual programming and simulation tools, staged tooling development, and physical layup validation. Particular emphasis is placed on head accessibility, heater collision avoidance, and robotic kinematic constraints, which are identified as primary limiting factors in complex geometries. A two-stage tooling strategy—combining low-cost prototype validation and high-performance production tooling—is implemented to reduce development risk. Results demonstrate that AFP can successfully produce structurally viable blade segments when process planning is treated as a system-level integration problem rather than a purely geometric exercise. The study establishes a practical workflow for transitioning legacy hand layup components to AFP manufacturing.

Keywords

Automated Fiber Placement; AFP Process Planning; Composite Manufacturing; Wind Tunnel Blades; Tooling Strategy; Heater Collision; Robotic Kinematics; Aerospace Manufacturing; Reverse Engineering

1. Introduction

Automated Fiber Placement (AFP) has become a critical enabling technology in modern aerospace manufacturing, particularly for large-scale composite structures such as fuselage barrels, pressure vessels, and launch vehicle components. Its ability to place narrow tows with high precision enables weight reduction, material efficiency, and repeatable manufacturing. However, the extension of AFP to medium-scale, geometrically complex components remains a significant challenge.

Wind tunnel blades represent a class of structures that combine moderate size with complex curvature, including twist, concavity, and variable cross-section geometry. Traditionally, these components have been manufactured using hand layup techniques, which are labor-intensive, time-consuming, and difficult to reproduce consistently. Furthermore, operational environments such as transonic wind tunnels require frequent replacement of damaged blades, making manufacturing efficiency a critical concern.

The central challenge is not whether AFP can deposit material onto such geometries, but whether the entire process chain—including geometry preparation, tool design, path planning, machine accessibility, and execution—can be successfully integrated within the constraints of existing AFP systems.

This study investigates the feasibility of applying AFP to wind tunnel blade structures using a production-scale aerospace cell. The work focuses on process planning and manufacturing validation, emphasizing the practical constraints that govern successful implementation.

2. Literature Review

AFP research has largely focused on large, relatively smooth geometries where machine accessibility and process stability are well understood. In these contexts, path generation strategies such as parallel and geodesic placement have been successfully applied.

For more complex geometries, research has identified several critical defect mechanisms, including gaps, overlaps, fiber angle deviation, and wrinkles. These defects are often linked to geometric constraints and steering limitations. While simulation tools enable prediction of some defect types, their integration into process planning remains limited.

Manufacturability studies have shown that geometric feasibility alone is insufficient to guarantee successful AFP implementation. Machine kinematics, head configuration, and tooling constraints must also be considered. In particular, head accessibility and collision avoidance have been identified as major challenges for concave and highly curved surfaces.

Tooling strategies for AFP have also evolved, with increasing use of additive manufacturing for rapid prototyping and cost reduction. However, the integration of prototype validation and production tooling remains an area requiring further development.

Overall, existing literature lacks comprehensive studies that integrate reverse engineering, process planning, tooling strategy, and full-scale manufacturing validation within a single workflow.

3. Methodology

3.1 Geometry Reconstruction

The blade geometry was reconstructed from a physical component using coordinate measurement techniques. Multiple cross-sectional profiles were captured and used to generate spline-based surface representations. A continuous tool surface was created through swept-blend modeling, with additional runout regions incorporated to support AFP path termination.

3.2 Subsection Selection

To reduce implementation risk, a representative subsection of the blade was selected for initial feasibility assessment. This approach isolates critical geometric features while maintaining manageable process complexity.

3.3 Process Planning

Process planning was conducted using virtual programming tools, focusing on:

• Layup strategy selection
• Starting point definition
• Fiber path propagation
• Boundary coverage
• Off-part motion

Special attention was given to heater orientation and clearance, as head geometry was identified as a primary constraint in concave regions.

3.4 Kinematic Validation

Machine simulation was performed to verify:

• Robotic joint limits
• Collision avoidance
• Safe motion paths
• Head accessibility

This step ensured that geometrically valid paths were also executable within the machine’s kinematic envelope.

3.5 Tooling Strategy

A two-stage tooling approach was implemented:

Prototype Tool

A low-cost additive manufacturing tool was produced to validate machine positioning and accessibility through dry runs.

Production Tool

A high-temperature tool was developed using structural analysis to withstand AFP compaction forces and curing conditions.

3.6 Manufacturing Execution

Material placement was conducted using slit tape on a multi-tow AFP system. The layup process included:

• Dry run validation
• Controlled placement with monitored process parameters
• Inspection and repair of local defects
• Autoclave curing

4. Results

The study demonstrates that AFP can successfully produce a doubly curved blade subsection with acceptable geometric fidelity and surface quality. The final cured structure maintained the intended shape, and no major surface defects were observed.

Process planning results indicate that heater collision and robotic joint limits were the dominant constraints, requiring iterative adjustments to path definition and head orientation.

The two-stage tooling strategy proved effective in reducing development risk, allowing early validation of machine interaction before committing to high-cost tooling.

The manufacturing workflow was executed successfully, confirming the feasibility of AFP for this class of geometry.

5. Discussion

The results highlight that AFP feasibility is governed by system-level integration rather than isolated process steps. Geometry, machine capability, and tooling must be considered simultaneously during process planning.

Head accessibility, particularly heater clearance, emerges as a critical limiting factor. This constraint is often more restrictive than fiber placement considerations, especially in concave regions.

The distinction between geometric validity and kinematic feasibility is also significant. Paths that appear correct in a geometric sense may still fail due to machine limitations, emphasizing the need for integrated simulation.

The use of staged tooling represents a practical strategy for reducing development risk. By separating geometric validation from structural tooling requirements, the approach enables faster iteration and cost control.

Finally, the study suggests that hybrid manufacturing approaches—combining AFP with manual layup in localized regions—may provide an optimal balance between automation and feasibility.

6. Conclusion

This study presents a comprehensive feasibility investigation of Automated Fiber Placement for complex wind tunnel blade structures. By integrating reverse engineering, process planning, kinematic validation, staged tooling, and manufacturing execution, the work demonstrates that AFP can be successfully applied to geometrically complex, medium-scale components.

The key contributions include:

• Establishing a practical workflow for AFP feasibility assessment
• Identifying head accessibility and kinematic constraints as primary limiting factors
• Demonstrating the effectiveness of staged tooling strategies
• Validating AFP manufacturing through full-scale execution

The findings confirm that AFP adoption for complex legacy components requires a system-level approach, where process planning serves as the central integration point between design and manufacturing.

Future work should focus on integrating defect-aware optimization and adaptive planning methods to further improve efficiency and scalability.

References

1. Harik, R., Halbritter, J. A., Jegley, D., Grenoble, R., Mason, B. (2019). Automated Fiber Placement of Composite Wind Tunnel Blades: Process Planning and Manufacturing. SAMPE Conference Proceedings.
2. Halbritter, J. A. (2023). Defect-Aware AFP Process Planning Framework. University of South Carolina.
3. CGTech. VERICUT Composite Programming Documentation.
4. NASA Langley Research Center AFP Technical Reports.