The Effect of Structural Integrity and Geometric Configurations of Corrugated Cores on Flexural Properties of Sandwich Panels: Experimental and Numerical Method

This research explores how the structural integrity and geometric configurations of corrugated cores impact the bending characteristics of sandwich panels. The 3-D knitted fabrics were produced on a flat knitting machine to form an integrated structure, while the non-integrated structure was manufactured by conventional 2-D fabrics in the identical parameters. The bonding of the core to the skin in the non-integrated structure was achieved by resin. The both integrated and non-integrated structures were fabricated with nearly identical mass and epoxy resin was injected through a vacuum assisted resin transfer method. The integrated 3D composite structures were manufactured in three distinct corrugated core designs: rectangular, hat-type, and triangular. The bending characteristics of the produced structures were measured in the transverse direction of corrugation by 3-point bending process. The results indicated that under equivalent load conditions for long beams, the 3D integrated structure displayed reduced bending deflections and enhanced bending stiffness compared to the non-integrated structure. Moreover, the non-integrated exhibited higher transverse shear rigidity than the integrated structure. It was also found that in long beams, the load-carrying capacity of the integrated structure is higher than that of the non-integrated structure. This comparison demonstrates some advantages of 3-D fabric as a sandwich panel reinforcement compared to lamination of 2-D fabric. Also, experimental results demonstrated that core geometry cannot significantly influence the flexural stiffness of the corrugated core sandwich panels. Finally, results demonstrated that the highest and the lowest transverse shear rigidity can be associated with the hat-type core sandwich panels and the triangular core sandwich panels, respectively. So, the hat-type corrugated core sandwich panel has the lowest deflection against bending force. Lastly, the experimental findings were evaluated against those from finite element analysis and showed a good correlation between experimental and numerical results.