Numerical modeling and experimental validation of axially loaded slender sandwich panels with soft core and various rib configurations

• Experimental and numerical studies on axially loaded sandwich panels with fiberglass skins.
• Model considers geometric non-linearity (P-Delta, out-of-straightness and end eccentricity).
• Excessive shear deformation of soft core and its effect on global buckling is accounted for.
• Model showed reasonable agreement, within ±20%, with test results for strength and stiffness.
• Effect of skin and core properties on axial stiffness and strength is demonstrated.

In this paper experimental and analytical investigations of axially loaded sandwich panels are presented. Large scale slender panels with and without ribs were tested. A robust analytical model applicable to panels of various slenderness ratios was developed. It accounts for geometric non-linearity through a rigorous P-Delta analysis, including the initial out-of-straightness profile and end eccentricities. The excessive shear deformation of the soft core and its effect on the overall stiffness and global buckling is accounted for. Additionally, the model detects localized skin wrinkling or crushing. The model showed reasonable agreement, within ±20%, with test results for strength and stiffness and was used in a parametric study. It was shown that the addition of a longitudinal rib connecting the skins at mid-width resulted in 180% increase in axial strength, by changing failure mode from skin wrinkling to global buckling. Adding longitudinal external ribs to the internal one changed failure mode to skin crushing and increased stiffness by 40% but did not enhance strength. Axial stiffness and strength also increased as skins or ribs became thicker, or their Young’s modulus increased, or as core shear modulus increased, however, failure mode varied depending on length. As the amplitude of out-of-straightness increased, failure load always reduced, weather governed by global buckling or skin wrinkling.