Tailored design of epoxy / glass composites: micromechanical modelling and two-scale simulation

• Applicant: Professor Dr.-Ing. Michael Kaliske
• Subject Area: Mechanics ; Polymer Materials
• Term: from 2009 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 107764890

• Final Report Year: 2015

Final Report Abstract

Summarizing the main achievements and developments made while project handling leads to the conclusion that a fully coupled multi-physical and multi-scale description of heterogeneous materials, specifically of fiber reinforced composites including the consideration of interfacial and interphasial effects, is obtained. The following developments are important steps towards the fully coupled thermomechanical multi-scale modeling approach, which is applied in context of the project to epoxy/glass fiber composites. First, the bulk materials, namely epoxy and glass, are constitutively described in terms of microthermomechanics. A constitutive description of thermoplastics based on a consistent numerical finite thermoviscoelastic framework is developed and successfully validated at experimental data. The thermoelastic Neo-Hooke material model is successfully applied to glass fibers. Second, the transition zone (interphase) between the fiber reinforcement and the matrix bulk material is geometrically and physically described with gradually changing material properties over the interphase cross-section. The functional dependencies of the thermomechanical interphase properties on the distance to the fiber surface are determined and successfully validated on experimental results. Last, the designated failure layer (interface) between fiber and matrix is thermomechanically described, based on finite deformation kinematics of separation vectors and temperature differences between the opening crack surfaces. The developed fully coupled interface element and the constitutive descriptions are successfully verified numerically. These steps lead to the developed boundary value driven approach to computational homogenization (BVDH). BVDH is firstly applied on purely mechanical problems and compared to existing FE2 methods, where a significant improve of efficiency is achieved. A further verification of BVDH leads to reliable numerical solutions for different loading scenarios. Since BVDH is a general homogenization framework and applicable to different multi-physical and multiscale problems, it is extended to thermomechanics. Numerical verifications are successfully carried out. One possible application of BVDH is the multi-scale material modeling, which is also successfully carried out in terms of describing semicrystalline polymers. With the developments made while project execution, different models and numerical frameworks are achieved, which provide the means for numerical simulations of industrial or academical applications in terms of multi-physical heterogeneous composites.

Publications

• A constitutive model for finite deformation of amorphous polymers. International Journal of Mechanical Sciences 65 (2012), pp. 48-63
  Fleischhauer, R.; Dal, H.; Kaliske, M.; Schneider, K.
  
• Numerical aspects on computational homogenization of epoxy/glass composites. Proceedings of Applied Mathematics and Mechanics 12 (2012), pp. 425-426
  Fleischhauer, R.; Dal, H.; K Aliske, M.
  
• A thermomechanical interface element formulation for finite deformations. Computational Mechanics 52 (2013), pp. 1039-1058
  Fleischhauer, R.; Behnke, R.; Kaliske, M.
  
• A Homogenization Approach and its Application to Multi-Scale Material Modeling. Proceedings of the Twelfth International Conference on Computational Structures Technology, Paper 87 (2014), B.H.V. Topping and P. Iványi (Eds.), Civil-Comp Press, Stirlingshire, Scotland
  Fleischhauer, R.; Popa, C.M.; Kaliske, M.
  
• Boundary value driven approach to computational homogenization. Proceedings of Applied Mathematics and Mechanics 14 (2014), pp. 557- 558
  Fleischhauer, R.; Kaliske, M.
  
• Formulation and implementation of a constitutive model for semicrystalline polymers. International Journal of Plasticity 61 (2014), pp. 128-156
  Popa, C.M.; Fleischhauer, R.; Schneider, K.; Kaliske, M.
  
• A novel approach to computational homogenization and its application to fully coupled two-scale thermomechanics. Computational Mechanics, November 2016, Volume 58, Issue 5, pp 769–796
  Fleischhauer, R.; Božic, M.; Kaliske, M.
  
• Thermomechanical modeling of fiber reinforced material including interphasial properties and its application to epoxy/glass composites. Engineering Computations Vol. 33 Issue: 4, pp.1259-1281, 2016
  Božic, M.; Fleischhauer, R.; Kaliske, M.