An adaptive shell element for explicit dynamic analysis of failure in laminated composites Part 1: Adaptive kinematics and numerical implementation. (December 2020)

• Record Type: Journal Article
• Authors: Främby, Johannes; Fagerström, Martin; Karlsson, Jesper
• Is Part Of: Engineering fracture mechanics. Volume 240(2020)
• Publication Date: 2020-12
• Subjects: Adaptivity -- Shell elements -- Crash simulations -- Composites -- LS-DYNA; Fracture mechanics -- Periodicals; Rupture, Mécanique de la -- Périodiques; Fracture mechanics; Periodicals; 620.112605
• DOI: 10.1016/j.engfracmech.2020.107288
• Languages: English
• ISSNs: 0013-7944

Abstract

Highlights: Adaptive refinement technique for analysis of progressive failure in laminates. Shell element refined with arbitrary number of weak and strong discontinuities. Implementation in commercial explicit dynamic solver LS-DYNA. Stabilisation of unphysical oscillations from refining in dynamic solver. Abstract: To introduce more fibre-reinforced polymers in cars, the automotive industry is strongly dependent on efficient modelling tools to predict the correct energy absorption in crash simulations. In this context, an adaptive modelling technique shows great potential. However, as the critical energy absorption in a crash occurs over a very short period of time, and since the deformation behaviour is very complex, car crash simulations are usually performed using explicit dynamic finite element solvers. Therefore, any practical adaptive technique must be adapted to an explicit setting in a software available to the automotive companies. In this paper, we propose an adaptive method for explicit finite element analysis and describe its implementation in the commercial finite element solver LS-DYNA. The method allows for both so-called weak discontinuities (discontinuities in strain), which are crucial for accurate stress and intralaminar damage predictions, and strong discontinuities (discontinuities in displacements), needed for a proper representation of growing delamination cracks. In particular, we detail the implementation of the proposed method into LS-DYNA and also how we propose to remedy the non-physical oscillations arising from the implementation of the adaptive scheme in a explicit dynamic setting. The paper is concluded with numerical examples where we demonstrate the potential for the adaptive approach and also perform a detailed study on its accuracy and stability.