Multi-scale mechanical modelling of braided composites including process induced defects
Materials in Sintering Processes and Generative Manufacturing Processes
Mechanical Properties of Metallic Materials and their Microstructural Origins
Final Report Abstract
In the research project Multi-Scale the influence of process-induced variability on the mechanical behaviour of braided carbon fibre structures was investigated. In addition to the purely experimental investigation, the focus was placed primarily on the numerical representation of process-induced defects and the investigation of its influence on the mechanical properties of braided composite materials. The approach to achieve this goal was to extend existing methods in order to describe in detail the braiding process. Furthermore, new methods were developed that make use of the information obtained in the process for use in mechanical analysis. To make these investigations possible a comprehensive test program to manufacture braided preforms with different process parameters was first carried out. From these preforms specimens were extracted and used to determine the influence of the process parameters on the braid quality. It was shown that a higher speed and an increased yarn tension lead to a reduction in braid quality. The best braid quality was achieved for a medium machine configuration of 100 rpm and 3.5 N yarn tension. This was also reflected in results of coupon mechanical tests, with this configuration showing the least amount of scatter in mechanical performance. Furthermore, a significant drop in the shear properties was observed for the most severely damaged specimens. The most influential parameter was identified to be the braid angle, followed by roving width and the resulting coverage. The variation of these three main influencing factors was considered in the simulation studies. For this purpose, explicit process simulations were performed with different solvers (Abaqus, PAM-Crash, LS-Dyna), all of which were able to describe the variations occurring with respect to braid angle. The variation of the roving width and the resulting degree of coverage was realized by a thermal expansion method. The comparison of micrographs showed a very good agreement. Two different methods were used to determine the mechanical properties. ITA relied on the use of CT measurement data with subsequent reconstruction and transfer into a numerical model. This enabled an exact recording of the real braided architecture to be obtained. However, this method is limited to rather small test specimens. IFB, on the other hand, pursued a purely virtual approach, whereby the results of the process simulation were used to generate a three-dimensional description of a varying braided architecture. Effects such as handling cannot be captured, but this method is suitable for the analysis of larger structures. The developed methods are being applied to other ongoing research projects.
Publications
- Influence of process induced defects for biaxial carbon fiber braids, In: IOP Conference Series: Materials Science and Engineering, Vol. 406, Conference 1: 13th International Conference on Textile Composites (TEXCOMP-13), Milan, Italy, 17-19 September 2018
Czichos, R.; Bareiro, O.; Pickett, A. K.; Middendorf, P.; Gries, T.
(See online at https://doi.org/10.1088/1757-899X/406/1/012047) - Characterization of manufacture inducted fibre damage by optical diffraction and influence on mechanical properties of braided composites, In: Proceedings of 5th International Conference on Mechanics of Composites (MECHCOMP 2019), Lisboa, Portugal, 1 – 4 July 2019
Bareiro, O.; Czichos, R.; Pickett, A. K.; Middendorf, P.; Gries, T.
- Effect of manufacture induced damage on braid architecture and fibre damage of braided preforms, In: Proceedings of 4th International Conference on Materials Technology and Applications (ICMTA 2019), Kyoto, Japan, October 11 – 14, 2019
Bareiro, O.; Czichos, R.; Pickett, A. K.; Middendorf, P.; Gries, T.
- Meso-scale finite element simulation of the braiding process, In: Proceedings of 12th International Conference on Composite Science and Technology, Sorrento, Italy, 8 – 10 May, 2019
Bareiro, O.; Czichos, R.; Pickett, A. K.; Middendorf, P.; Gries, T.
- Numerical modelling of biaxial carbon fiber braids considering process variabilities, In: Proceedings of the 22nd International Conference on Composites Materials (ICCM22), Melbourne, Australia, 2019
Czichos, R.; Bareiro, O.; Pickett, A. K.; Middendorf, P.; Gries, T.
- Experimental and numerical studies of process variabilities in biaxial carbon fiber braids, In: International Journal of Material Forming, 2020
Czichos, R.; Bareiro, O.; Pickett, A. K.; Middendorf, P.; Gries, T.
(See online at https://doi.org/10.1007/s12289-020-01541-4)
