Bearing behaviour of high-performance Thin-Ply fibre metal laminates
Final Report Abstract
Due to the excellent density-specific mechanical properties, carbon fibre-reinforced polymers (CFRP) are increasingly used as primary materials for lightweight structures. However, conventional CFRP laminates do not exploit the full potential of the carbon fibres used. To achieve the future target of decarbonisation, it is necessary to increase the composite performance. One way to improve the lightweight potential of CFRP is to reduce the ply thickness, so-called Thin- Ply. Thin-Ply laminates are characterized by layer thicknesses of less than 100 µm. They are produced by a tow-spreading process in which conventional tows are spread into a flat fibre band. The spreading process increases the quality of the prepreg layers. The layers exhibit a more homogeneous fibre distribution and fewer and smaller resin-rich regions. Furthermore, due to the thin layers and the resulting high number of layers, a higher flexibility is achieved concerning the laminate lay-up. Mechanical investigations have shown that the layer thickness directly influences the mechanical failure behaviour of the laminates. Thinner layers exhibit increased transverse tensile and shear strength (in-situ effect) and suppress delamination initiation. The failure mode changes from a delamination-dominated (Thick-Ply) to a brittle, fibre-dominated (Thin-Ply) failure behaviour, and the tensile and compressive strengths of quasi-isotropic laminates increase with decreasing layer thickness. Although adhesive bonding is being used more and more frequently, bolted connections are the most common method of joining two components. Due to the possible use of Thin-Ply as primary construction material, it is necessary to investigate the mechanical behaviour of bolted joints as a function of the layer thickness. The results of the mechanical tests show that reducing the layer thickness does increase the bearing strength, but not as much as the tensile and compressive strength. To increase the bearing performance within this study, 90° CFRP layers are locally substituted by stainless steel patches. Due to the isotropic and ductile material behaviour, metals have significantly higher bearing properties than composite materials. Experimental studies showed that due to the hybridisation, the bearing strength increased significantly, and the sensitivity of the mechanical properties to the laminate configuration and environmental effects decreased. To describe the mechanical behaviour and investigate different design parameters, the target of this project was to develop a numerical model of the bearing tests. Experimental tests showed that the Thin-Ply specimens failed due to fibre kinking. For this reason, a modelling strategy that includes 3D stress states and fibre kinking is chosen. To avoid high computational power, primarily micro-damages such as matrix cracks are not included. The results of the simulations of the Thin-Ply and the hybrid samples show a good agreement with the experimental results. It is shown that the modelling approach of not including micro-damage is well applicable for thinner plies but reaches its limits for thicker plies.
Publications
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Bearing Strength of High Performance Thin-Ply Fibre Metal Laminates; B. Koetter, K. Yamada, J. Koerbelin, K. Kawabe, M. Nishikawa, M. Hojo, F. Fiedler; US-Japan / EU- Japan Joint Conference on Composite Materials, Sendai, Japan, 2022
B. Koetter, K. Yamada, J. Koerbelin, K. Kawabe, M. Nishikawa, M. Hojo & F. Fiedler
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Effect of Gap Location on Impact Damage behaviour of Thin-ply CFRP Laminates; N. Takatsuka, B. Koetter, K. Yamada, M. Nishikawa; The 2nd Japan-China-Korea Joint Symposium on Composite Materials, Kanazawa, Japan, 2023
N. Takatsuka, B. Koetter, K. Yamada & M. Nishikawa
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Experimental Investigations and Finite Element Analysis of the Bearing Strength of High Performance Thin-Ply Fiber Metal Laminates; B. Koetter, K. Yamada, J. Koerbelin, K. Kawabe, M. Nishikawa, M. Hojo, F. Fiedler; APISAT 2023, Niigata, Japan, 2022
B. Koetter, K. Yamada, J. Koerbelin, K. Kawabe, M. Nishikawa, M. Hojo & F. Fiedler
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Numerical Simulation of the Bearing Behaviour of Thin-Ply Fibre Metal Laminates; B. Koetter, K. Yamada, N. Takatsuka, F. Fiedler, M. Nishikawa; JCOM2023 – Future Generation Symposium on Composite Materials 2023, Shodoshima, Japan, 2023
B. Koetter, K. Yamada, N. Takatsuka, F. Fiedler & M. Nishikawa
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Numerical Simulation of the Bearing Failure Mechanism of the Thin-Ply Metal Laminates; B. Koetter, K. Yamada, N. Takatsuka, F. Fiedler, M. Nishikawa; Twenty-Third International Conference on Composite Materials (ICCM23), Belfast, Ireland, 2023
B. Koetter, K. Yamada, N. Takatsuka, F. Fiedler & M. Nishikawa
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Numerical Simulation of the Bearing Strength of Thin-Ply Fibre Metal Laminates; B. Koetter, K. Yamada, N. Takatsuka, F. Fiedler, M. Nishikawa; 6th International Conference on Materials and Reliability, Yamaguchi, Japan, 2023
B. Koetter, K. Yamada, N. Takatsuka, F. Fiedler & M. Nishikawa
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Numerical investigation of the bearing performance of Thin- and Thick-Ply hybrid laminates. Composite Structures, 345, 118372.
Kötter, Benedikt; Yamada, Kohei; Takatsuka, Naoki; Fiedler, Bodo & Nishikawa, Masaaki
