Experimental characterization and numerical simulation of the automated fiber placement (AFP) process for thermoplastic fiber-reinforced plastics

• Applicants: Professor Dr.-Ing. Klaus Drechsler; Professor Dr.-Ing. Alexander Popp
• Subject Area: Plastics Engineering ; Materials in Sintering Processes and Generative Manufacturing Processes ; Mechanics
• Term: from 2016 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 325153381

• Final Report Year: 2023

Final Report Abstract

The project aimed at the experimental characterization and numerical simulation of the Automated Fiber Placement (AFP) process for thermoplastic fiber reinforced composites in order to generate knowledge and prediction methods for the AFP process. Driven by the high and steadily increasing interest in TP-AFP with a simultaneous lack of reliable scientific statements on its process and targeted control, the process understanding and simulation-based prediction of component properties should be improved in order to bring TP-AFP closer to the industrially required maturity level. In particular, the correct selection of appropriate process windows for key parameters such as laser power, deposition speed, and contact pressure will determine consistently high part quality for different material systems and deposition shapes. However, so far the prediction capabilities, for example for residual stresses and warpage, are insufficient for practical applications. The reasons for this discrepancy between low prediction accuracy and high industrial demands lie in unexploited possibilities of process characterization and modeling and simulation. Therefore, the goal of the applicants was to improve the process understanding in the field of TP-AFP at the fundamental level of material-process interaction, which requires a deep understanding of all components and steps of the TP-AFP process. To this end, experimental and numerical characterizations of various components of an AFP system were carried out. In addition to determining and describing the material processing of the semi-finished product, a tape made of thermoplastic fiber composite, the consolidation roll in particular, which is directly involved in the depositing process, was investigated in detail. On the experimental side, material properties were determined, and on the numerical side, the contact behavior of the consolidation roll with the tape and the deposit table was examined. To improve the numerical simulation methods, efficiency and robustness improvements were sought and achieved, in particular through newly developed dynamic load distribution algorithms and improved nonlinear solution methods for contact problems. In order to be able to measure distortion states in finished components, fiber optic sensors (fiber Bragg lattices) were first individually characterized with respect to their mechanical and optical properties and then introduced into the component during the TP-AFP process. Although a comprehensive investigation of the overall TP-AFP process could not be achieved, a deep understanding of individual components and steps of the TP-AFP process was generated. Results, such as efficient algorithms for contact simulation, are relevant for science and users beyond the present project.

Publications

• Solving computational contact problems efficiently at large scale, 8th GACM Colloquium on Computational Mechanics, Kassel, Germany, August 28 - 30
  Mayr, M. & Popp, A.
  
• Solving computational contact problems efficiently at large scale, In: Proceedings of the 8th GACM Colloquium on Computational Mechanics, T. Gleim, S. Lange (Eds.), Kassel University Press, Germany
  Mayr, M. & Popp, A.
  
• Advanced Non-Linear Solution Techniques for Computational Contact Mechanics, Doktorarbeit, Technische Universitat München
  M. Hiermeier
  
• Laser-assisted thermoplastic tape placement: Effects of the consolidation roller diameter on the wedge peel strength of CF/PA6 SAMPE Europe 20 Conference, Amsterdam, The Netherlands, September 30 - October 1
  V. Zinnecker, V. Backmann, C. Stokes-Griffin, K. Drechsler
  
• Dynamic load balancing for large-scale mortar contact formulations, 91st GAMM Annual Meeting, Kassel, Germany, March 15 - 19, 2021
  M. Mayr & A. Popp
  
• Dynamic load balancing for large‐scale mortar contact formulations. PAMM, 20(1).
  Mayr, Matthias & Popp, Alexander
  
• Influence on the strain rate at room temperature of a silicone rubber used as fiber placement roller jacket, SAMPE Europe 21 Conference, Baden/Zurich, Switzerland, September 28 - 30
  V. Backmann, J. Klingenbeck, A. Popp & K. Drechsler
  
• Dynamic load balancing for contact mechanics at large scale, 15th World Congress on Computational Mechanics (WCCM 2022) & 8th Asian Pacific Congress on Computational Mechanics (APCOM 2022), Yokohama, Japan, July 31 - August 5, 2022
  M. Mayr, C. Steimer & A. Popp
  
• An Edge-Filtered Optical Fiber Interrogator for Thermoplastic Polymer Analysis. Sensors, 23(6), 3300.
  Backmann, Vincent; Dorner, Felix & Drechsler, Klaus
  
• Scalable computational kernels for mortar finite element methods. Engineering with Computers, 39(5), 3691-3720.
  Mayr, Matthias & Popp, Alexander