Failure mode maps for composite anisogrid lattice sandwich cylinders under fundamental loads

A theoretical study was carried out to predict the failure load and mode of composite anisogrid lattice sandwich cylinder (LSC) under fundamental loads. Four failure modes were suggested for this structure under axial compression, uniform external pressure and torsion, including global buckling, skin monocell buckling, rib crippling and strength failure. For each failure mode, the load capacity of the composite LSC was predicted theoretically and corrected by finite element method (FEM) with proper correction coefficients. To instruct the design of the LSC, failure mode maps were constructed, showing the dependence of failure mode and load on the geometrical variables of the lattice and skins. The concept of a failure mode map is extended to give a useful design tool for anisogrid sandwich cylinder manufacturers and their customers.