The blog article is a summary of the work "Optimizing the lay-up of composite tapes based on an improved geodesic strategy for automated tape placement" by wonderful authors Peng Zhang, Zhenhua Zhou, Gengbiao Chen, and Shuhan Chen
What did the research find?
The commercial software (TORLAY for TORRESLAYUP) brought about excessive gaps between tapes in the 0° layer. This was demonstrated through an engineering case.
The improved geodesic strategy was adopted to optimize the relationship between successive tapes in the 0° layer. This was validated through computer simulation in MATLAB 7.0.
The lay-up trajectories of the 12th tape to the 18th tape needed to be improved. The improved geodesic strategy was used to ensure a uniform gap between these tapes.
The improved lay-up trajectories and their corresponding values of Ratio were acquired. The values of the Ratio of the improved lay-up trajectories are recorded in Table 5.
The gaps between the successive tapes along the improved lay-up trajectories were examined.
The placement temperature was set as 33 °C and the roller pressure was set as 500 N.
These findings suggest that the improved geodesic strategy can effectively optimize the ATP process, reducing gaps and preventing wrinkling in the composite tapes.
What is the problem with present planning strategies with the ATP process?
The present planning strategies with Automated Tape Placement (ATP) process face several challenges:
Due to the complex contour of the mold surface, the lay-up paths of contiguous tapes are not parallel along their lengths, which eventually introduces gaps or overlaps between the edges of the tapes. Overlaps and excessive gaps are undesirable as they decrease the strength of the resulting composite member.
Most of the existing approaches for optimizing the lay-up paths are classified as the first type, which takes care of the distortion of composite tape to prevent wrinkling. However, none of these methods could conveniently specify the distortion of tape while it follows the improved lay-up trajectories. Considering that the in-plane deformation capacity of the composite tape is very small, wrinkles could still appear.
The relationship between adjacent tapes could be optimized by adjusting the values of initial distance and lay-up angle. However, due to the requirements of ATP, only minor adjustments of the initial conditions are allowed. These limitations might result in an unsatisfactory optimization result: large gaps could still emerge on substrates with large curvatures even after optimization.
The centerline trajectories of composite tapes generally follow natural paths, as defined by mathematical geodesics. Although geodesics minimize the distortion of composite tape, they might lead to overlaps and excessive gaps.
How does the author approach this problem?
The authors approach the problem with the Automated Tape Placement (ATP) process by proposing an improved geodesic strategy. Here are the main steps of their approach:
Improved Geodesic Strategy: The authors propose a simple trajectory planning method, called the improved geodesic strategy for ATP. The aim of this method is to optimize the relationship between successive tapes while suppressing the appearance of wrinkles. This strategy is accurate as it is performed directly on the original mold surface.
Deflection Curve: The authors propose the concept of a deflection curve for the trajectory planning of ATP. This curve enables them to conveniently predict the local distortion and specify whether wrinkling will appear in the composite tapes during the optimization.
Numerical Solution: The authors present a numerical approach for deriving the deflection curve. The feasibility of the deflection curve for adjusting the relationship between adjacent tapes is validated through computer simulation.
Upper Limit of Deflection: Based on the formation mechanism of wrinkling in the composite tape, the authors derive the upper limit of the deflection. The optimization is performed within this upper limit, ensuring that their method will not lead to wrinkling in the placement of the composite tape.
Computer Simulation: The authors validate their improved geodesic strategy through computer simulation. The simulation shows that the improved geodesic strategy has successively eliminated excessive gaps in the 0° layer of an airfoil, without causing wrinkling in the laid composite tapes.
What's the new Algorithm?
the algorithm for the improved geodesic strategy for Automated Tape Placement (ATP) planning could be outlined as follows:
Initialize Parameters: Set the initial parameters for the ATP process, including the initial distance and lay-up angle. These parameters should be set within the constraints of the ATP process.
Define Mould Surface: Define the complex contour of the mold surface. This could be represented as a mathematical function or a 3D model.
Calculate Geodesic Path: Calculate the geodesic path for the tape placement. This path minimizes the distortion of the composite tape but may lead to overlaps and gaps.
Calculate Deflection Curve: Calculate the deflection curve for the tape placement. This curve predicts the local distortion of the tape and indicates whether wrinkling will occur.
Optimize Tape Placement: Adjust the parameters of the deflection curve to optimize the tape placement. The aim is to minimize gaps and overlaps between tapes and prevent wrinkling. This optimization should be performed within the upper limit of deflection to ensure that wrinkling does not occur.
Validate Results: Validate the results of the optimization through computer simulation. The simulation should show that the improved geodesic strategy successfully eliminates excessive gaps without causing wrinkling.
Iterate if Necessary: If the results are not satisfactory, adjust the initial parameters or the deflection curve and repeat the optimization process.
Finalize ATP Plan: Once the results are satisfactory, finalize the ATP plan. The final plan should specify the lay-up trajectories for the tapes and the corresponding values of the initial distance and lay-up angle.
Please note that this is a high-level outline and the actual implementation of the algorithm would involve more detailed steps and complex mathematical calculations.
Conclusion
The article discusses the challenges in the Automated Tape Placement (ATP) process, particularly the issues of gaps and overlaps between tapes, and the potential for wrinkling due to the complex contour of the mould surface and the limitations of existing optimization methods. To address these issues, the authors propose an improved geodesic strategy for ATP.
This strategy introduces the concept of a deflection curve for trajectory planning, which allows for the prediction of local distortion and the prevention of wrinkling in the composite tapes during the optimization process. The authors also present a numerical approach to derive the deflection curve and establish an upper limit for deflection to prevent wrinkling.
The effectiveness of this improved geodesic strategy is validated through computer simulations, which show that it successfully eliminates excessive gaps in the 0° layer of an airfoil without causing wrinkling. The authors suggest that this strategy will be increasingly effective for more complex mould surfaces as the range of deflection increases. Future research is recommended to examine the influence of process parameters on the allowable in-plane deformation capacity of the composite tape.
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