Local buckling modelling of anisogrid lattice structures with hexagonal cells: An experimental verification

Following the analytical modelling, the first experimental verification of the local buckling failure mode of anisogrid lattice structures with the system of hexagonal cells is here discussed. Such verification is based on a test-article extracted from the composite cylindrical prototype that was designed and manufactured at CIRA for a lightweight launch vehicle interstage. Therefore, the test-article consists of a curved anisogrid lattice panel (without skin) including multiple hexagonal cells (but with a limited cell periodicity) and subjected to an axial compressive load. Complementary mechanical tests on specimens of helical ribs extracted from the same prototype are conducted in order to evaluate the effective flexural stiffness (and strength) properties which are relevant in the bending mechanism. Finite-element models simulating the lattice cylindrical shell and the panel are constructed in order to corroborate the analytical buckling prediction. Finally, the axial compressive test on the panel demonstrates the buckling mode under investigation and the complete correspondence with theoretical and numerical evaluations.