An assessment of the new LS-DYNA layered solid element: basics, patch simulation and its potential for thick composite structure analysis

One major component of fuel cell vehicles is the hydrogen storage system. A promising and nowadays mostly used approach is to store hydrogen in wet wound carbon fiber reinforced plastic (CFRP) vessels manufactured by filament winding process with an operating pressure of up to 70 MPa (hereafter referred as H2 vessel). Due to the inherent complexity and 3-dimensional nature, accurate behavior of such thick composite structures in impact simulations needs an adequate representation of the composite plies. Modeling thick composite structures with 2-dimensional elements will produce inaccurate results in transverse normal direction. Thus 3D modeling should be used but to model each ply with one solid element leads to undesirably big models and is impractical for large structures. Thus representation of several plies in one solid element and more such elements across thickness is desired. Also, solid elements are needed to represent the 3-dimensional state of stress and impact direction normal to the outer vessel surface. A new layered solid element formulation is implemented in LS-DYNA® Version 971 R4 allowing the definition of multiple integration points through the thickness in combination with arbitrary material orientation. The above new element formulation is presented in this paper describing different patch simulation results and simulation results for thick composite structures such as hydrogen storage H2 vessels.