TLDR
Overcoming Wrinkle and Overlap Defects in Automated Fiber Placement for Composite Pressure Vessels
Composite pressure vessels have been widely used for decades in various industries such as aerospace, military, and marine applications due to their lightweight and high-strength properties. However, the automated fiber placement (AFP) process, which is a cutting-edge technology for fabricating composite pressure vessels, faces significant challenges in terms of wrinkle and overlap defects.
Key issues with AFP for composite pressure vessels:
Out-of-plane buckling and wrinkling of thermoplastic prepreg tows during steering, especially on dome sections
Gaps and overlaps between adjacent prepreg tows, leading to non-uniform thickness and dimensional inaccuracies
Reduced mechanical properties and potential damage/failure in areas with defects
Lower production efficiency due to increased shearing and re-feeding of prepreg tows
Recent research has focused on addressing these problems through advanced placement path planning algorithms. Some notable approaches include:
Optimizing prepreg trajectories considering shell geometry and wrinkle formation mechanisms
Developing layup quality evaluation criteria based on prepreg deformability
Generating continuous, collision-free placement paths for complex surfaces using computational methods
However, there is still a need for a comprehensive solution that can generate wrinkle-free and defect-free placement paths for the entire pressure vessel structure, including the challenging dome sections. This is critical for improving the quality, performance, and efficiency of AFP-manufactured composite pressure vessels.
Wrinkle and Overlap Defects Impeding Quality and Efficiency in Automated Fiber Placement of Composite Pressure Vessels
The presence of wrinkle and overlap defects in AFP-manufactured composite pressure vessels can have severe consequences on their structural integrity and performance.
Wrinkle defects, caused by out-of-plane buckling of prepreg tows during steering operations, can lead to:
Resin-rich areas and voids
Reduced load-carrying capacity
Potential delamination and failure initiation sites
Overlap defects, resulting from gaps between adjacent prepreg tows, can cause:
Non-uniform thickness distribution
Dimensional inaccuracies and shape distortions
Increased weight and material waste
These defects not only compromise the mechanical properties and reliability of the composite pressure vessel but also hinder the efficiency and productivity of the AFP process. Key pain points include:
Increased downtime for manual inspection and repair of defects
Higher scrap rates and material consumption
Longer production cycles and lower throughput
Difficulty in achieving consistent quality, especially for complex geometries like domes
The impact of wrinkle and overlap defects extends beyond the manufacturing process. End-users of composite pressure vessels, such as aerospace and marine industries, face increased risks and costs associated with:
Premature failure and reduced service life
More frequent maintenance and replacement
Potential safety hazards and liability issues
Addressing these defects is paramount for manufacturers to deliver high-quality, reliable, and cost-effective composite pressure vessels. This requires advanced placement path planning solutions that can minimize or eliminate wrinkle and overlap defects while optimizing production efficiency.
Novel Path Planning Approach Integrating Wrinkle-Free Criterion and Defect-Free Algorithms for Ellipsoidal Dome and Cylinder Sections
To address the challenges of wrinkle and overlap defects in AFP of composite pressure vessels, the authors propose a novel path planning approach that integrates a wrinkle-free criterion and defect-free algorithms specifically tailored for the ellipsoidal dome and cylinder sections.
Key features of the approach:
Wrinkle-free placement path equations for ellipsoidal dome section
Derived from wrinkle defect criterion based on prepreg deformation characteristics
Considers shell geometry, geodesic curvature, and minimum steering radius
Enables calculation of wrinkle-free laying angle range and fiber paths
Defect-free placement path planning algorithm for ellipsoidal dome section
Achieves gap-free, overlap-free, and wrinkle-free placement
Determines optimal laydown angles based on prepreg width and dome geometry
Ensures uniform fiber distribution and full coverage
Wrinkle-free placement path equations for cylinder section
Analytically derived based on constant cross-section and zero Gaussian curvature
Provides a theoretical foundation for variable-angle placement without wrinkles
Allows calculation of laying angle range and fiber paths
Full coverage simulation and verification
Models the continuous placement process with multiple circuits and offset
Determines the required number of circuits and mandrel rotation angles
Validates the uniform coverage and defect-free placement paths
The approach leverages advanced computational methods and geometric analysis to generate optimized placement paths that minimize defects and maximize efficiency. Key advantages include:
Direct generation of laying angle ranges and fiber paths, reducing trial-and-error
Adaptability to different prepreg materials and pressure vessel geometries
Compatibility with optimization algorithms for further refinement
Potential for integration with AFP machine control systems
Simulated Verification of Wrinkle-Free, Defect-Free, and Full Coverage Placement Paths with Optimized Motion Control Parameters for High-Quality and Efficient Automated Fiber Placement of Composite Pressure Vessels
The proposed path planning approach has been rigorously validated through simulations and experimental verification, demonstrating its effectiveness in generating
high-quality, defect-free placement paths for composite pressure vessels.
Simulation results:
Wrinkle-free placement paths for ellipsoidal dome section
Generated fiber paths within the calculated wrinkle-free laying angle range
Verified reduction of wrinkle formation compared to conventional geodesic paths
Defect-free placement paths for ellipsoidal dome section
Achieved uniform fiber distribution without gaps or overlaps
Demonstrated adaptability to different dome geometries and prepreg widths
Wrinkle-free placement paths for cylinder section
Validated the analytical equations for variable-angle placement
Confirmed the elimination of wrinkle defects in the cylinder region
Full coverage simulation
Verified the complete and uniform coverage of the pressure vessel with optimal number of circuits
Determined the required mandrel rotation angles for seamless transitions
Experimental verification:
Implemented the generated placement paths on an AFP machine
Analyzed the laid-up prepreg samples for wrinkle, gap, and overlap defects
Confirmed the significant reduction of defects compared to conventional paths
Validated the improved mechanical properties and dimensional accuracy of the composite pressure vessel
Optimized motion control:
Developed algorithms for coordinated motion of the AFP machine's axes
Generated control inputs based on the optimized placement paths and laying angles
Achieved smooth and precise laying of prepreg tows with minimal vibration and disturbance
Demonstrated improved production efficiency and reduced cycle times
The simulation and experimental results confirm the effectiveness of the proposed approach in delivering wrinkle-free, defect-free, and full coverage placement paths for composite pressure vessels. The optimized motion control ensures the reliable and efficient execution of these paths on AFP machines.
Key benefits:
Improved structural integrity and performance of composite pressure vessels
Reduced scrap rates, material waste, and manual rework
Increased production throughput and cost-effectiveness
Potential for automation and industrial implementation
References
We would like to express my sincere gratitude to the authors Bo Wang, Lihua Wen, Jinyou Xiao, Shiyu Wang, Ping Ren, Liqiang Wang, Lei Zu, and Xiao Hou for their valuable contributions in writing this blog post. Their research paper, "Automated Fiber Placement Path Planning and Analysis of Pressure Vessels," served as the foundation for the content presented here.
Their innovative approach to optimizing automated fiber placement for composite pressure vessels, which integrates wrinkle-free criteria and defect-free algorithms, has the potential to revolutionize the manufacturing process. The comprehensive simulations and experimental validations conducted by the authors demonstrate the effectiveness of their method in reducing defects, improving quality, and increasing efficiency.
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