DYCOMP - ECCCS – 3 2024

Efficient modelling of dynamic delamination growth using large and distorted elements

  • Daniel, Pierre (btechc - Barcelona Technical Centert)
  • Främby, Johannes (ANSYS Sweden)
  • Fagerström, Martin (Chalmers University of Technology)
  • Maimí, Pere (University of Girona)

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Detecting and modelling dynamic out-of-plane failure of laminates in finite element simulations requires high spatial resolution through the thickness, leading to excessive computational time for large structures. Additionally, using traditional cohesive zone elements for modelling propagating delaminations limits in-plane element size due to the quasi-brittle nature of delamination failure. This necessitates dense discretisations, resulting in long computational times. Here we propose a computational method for efficient delamination modelling, combining accurate recovery of transverse stress variation through the thickness [1] with an adaptive shell modelling approach. This approach allows new delaminations to form as displacement discontinuities adaptively introduced during the simulation [2]. To facilitate the use of larger in-plane shell element dimensions, keeping the critical time step for explicit analysis larger, we employ an energy release rate-based cohesive method [3,4], enabling predictive delamination modelling with in-plane element sizes significantly larger than the damage process zone. Adaptive crack propagation [2] is determined using the energy release rate estimated by the virtual crack closure technique. To progressively open newly formed crack segments, a novel nodal cohesive law is introduced, allowing smooth interface release while dissipating the appropriate energy under mixed mode conditions. Numerical results demonstrate the capability to accurately simulate double cantilever beam, end-notched flexure, and mixed-mode bending tests with regular and irregular meshes for element lengths up to 8 mm [3]. Recently, this method has been extended to handle in-plane irregular meshes [4], capturing the evolving delamination front shape. [1] P. Daniel et al: Complete transverse stress recovery model for linear shell elements in arbitrarily curved laminates, Composite Structures, 2020. [2] J. Främby and M. Fagerström: An adaptive shell element for explicit dynamic analysis of failure in laminated composites Part 2: Progressive failure and model validation, Engineering Fracture Mechanics, 2021. [3] P. Daniel et al: An efficient ERR-Cohesive method for the modelling of delamination propagation with large elements, Composites Part A: Applied Science and Manufacturing, 2023. [4] P. Daniel et al: A method for modelling arbitrarily shaped delamination fronts with large and distorted elements, Engineering Fracture Mechanics (accepted).