NCF--CAE: Simulation of Non-Crimp Fabrics based on Computational isogeometric shell elements, Analytical averaging and Experimental analysis

• Applicants: Professor Dr.-Ing. Thomas Gries; Professor Dr.-Ing. Mikhail Itskov, since 11/2019
• Subject Area: Mechanics ; Lightweight Construction, Textile Technology
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 408311698

• Final Report Year: 2022

Final Report Abstract

In our project, mechanics of textile reinforced composites in general and non-crimp fabrics in particular has been investigated thoroughly from both experimental and computational viewpoints. In the experimental part, various non-crimp fabrics with different structure parameters were produced and correlations between those parameters and mechanical properties of NCFs were detected by performing measurements at different length scales. In the computational part, a generalized Kirchhoff-Love shell theory capable of capturing in-plane bending of fibers embedded in the shell surface was developed. It overcame limitation of the classical approaches in describing initially curved fibers, in addition, all kinematic measures are second order tensors so that their invariants have interpretable physical meaning. Thus, the proposed model is advantageous to the existing second gradient shell theory. A nonlinear rotation-free isogeometric shell formulation of the proposed generalized Kirchhoff-Love shell theory was derived, which allows for simulation of large sheets of heterogeneous fibrous materials in addition to non-crimp fabrics. A combination of the developed shell formulation with the analytical averaging constitutive model can can capture well the in-plane shear behavior of fabrics up to moderate deformation in the bias extension test. In order to cure possible material instabilities due to fiber compression, additional stabilization term was proposed within the framework of the nonlinear rotation-free isogeometric shell formulation. Furthermore, the accuracy and robustness of the developed shell formulation were carefully verified with multiple benchmark tests with both homogeneous and inhomogeneous deformation. Nevertheless, both experiment and computational results revealed an important role of inter-ply and intra-ply sliding in the in-plane shear deformation of the fabrics, which could be a subject of future work.

Publications

• A general isogeometric finite element formulation for rotation‐free shells with in‐plane bending of embedded fibers. International Journal for Numerical Methods in Engineering, 123(14), 3115-3147.
  Duong, Thang X.; Itskov, Mikhail & Sauer, Roger A.
  
• A general theory for anisotropic Kirchhoff–Love shells with in-plane bending of embedded fibers. Mathematics and Mechanics of Solids, 28(5), 1274-1317.
  Duong, Thang X.; Khiêm, Vu N.; Itskov, Mikhail & Sauer, Roger A.
  
• Material characterisation of biaxial glass-fibre non-crimp fabrics as a function of ply orientation, stitch pattern, stitch length and stitch tension. Journal of Composite Materials, 56(26), 3971-3991.
  Quenzel, Philipp; Kröger, Hauke; Manin, Boris; Ngoc, Vu Khiêm; Duong, Thang Xuan; Gries, Thomas; Itskov, Mikhail & Sauer, Roger A.