Modelling coupons at dome area of composite pressure vessels: from a 2D-shell to a 3D-solid formulation, with comparison to test results

This paper describes a methodology developed to accurately model the material properties in the dome area of composite overwrapped pressure vessels (COPV). First, a COPV is produced on a hexagonalshaped so-called “soccer ball” mandrel, which has cleverly-designed flat faces in the dome and in the cylindrical regions. Coupons with specific dimensions and stacking sequences are extracted from the cylindrical region of the COPV and are tested, in order to identify the parameters of an advanced intralaminar damage model for orthotropic plies. Coupons in the dome area are then extracted in longitudinal and circumferential directions. These coupons are flat on one side (the one in contact with the mandrel),
and non-flat on the other side. They present a (complex) variable thickness pattern. Starting from a shell model of the coupons developed in a previous paper, a 3D solid-elements model is here developed, in
which each layer is represented with its geometrical thickness. We then come up with a 3D model with variable thickness that represents the interlacements of the tapes resulting from the filament winding
process. Four-point bending physical tests are conducted on the coupons, and the corresponding FEM simulations are performed. A good agreement is obtained between simulations and tests in terms of stiffness and strength.