Failure mechanisms of fluted-core sandwich composite panels under uniaxial compression

Fluted-core sandwich composite structures are major load-bearing components used in launch vehicles. Herein, analytical models were proposed to investigate the failure mechanisms of fluted-core sandwich composite panels, including global buckling, local buckling, and material failure. Failure mode maps of fluted-core sandwich panels were constructed to analyze the intrinsic impact mechanism of geometric parameters on failure behavior. Integrated fluted-core sandwich composite panels were then fabricated by adopting the integrated forming process and co-cured method. Uniaxial compression tests and finite element simulation were also conducted to verify the analytical predictions with good consistency. The effects of the geometric variable on both load-bearing capacity and failure modes of the structures were explored. The results indicated the occurrence of global buckling at small distances between the top and bottom face sheets, resulting in undesired load-carrying capacities. The decrease in width of short span or increase in thickness of face sheets prevented such local-buckling behavior, resulting in material failure. The triangular-shaped core with zero short spans was identified as a better option for material failure as dominant failure mode for designing load-bearing sandwich panels. These findings look promising for lightweight and load-carrying applications, providing a reliable reference for the initial design of such sandwich structures.