This article aims to evaluate the effect of core geometry on flexural stiffness and transverse shear rigidity of corrugated core sandwich panels both experimentally and numerically. Using vacuum‐assisted resin transfer molding (VARTM) method, three composite sandwich panels reinforced with 3D weft knitted spacer fabric with rectangular, hat‐type (trapezoidal) and triangular cross‐sectional geometries were produced. In order to eliminate weight variation among the produced sandwich panel samples, the unit cell dimensions, core wall to skin angle, and the yarn count used to knit the core wall were carefully chosen. Results pointed to existence of statistically significant difference between the load‐carrying capacity and transverse shear rigidity in the direction of corrugation of the structures. It was concluded that triangular and rectangular structures have the highest and lowest load‐carrying capacity, transverse shear rigidity, and core shear modulus in the direction of corrugation, respectively.
This study deals with free vibration analysis of integrated and non-integrated corrugated core sandwich panels with rectangular core together with free vibration analysis of integrated corrugated core sandwich panels with hat-type and triangle core. Bonding of the core to skin in non-integrated sandwich panels was achieved by resin, while in the integrated sandwich panels that were reinforced with 3-D weft-knitted fabric bonding was achieved using yarns and resin. Results revealed that the integrated structures have higher natural frequency than the non-integrated structures. It was also found that the natural frequency of the triangular-core sandwich panels and the rectangular-core sandwich panels was the highest and the lowest, respectively. It was established that weft-knitting fabric technology is suitable for the production of both integrated and non-integrated corrugated core sandwich panels with a high degree of similarities in terms of geometry, weight, and characteristics.
This study deals with the investigation of flexural stiffness and transverse shear rigidity in the direction of corrugation of the integrated and non-integrated corrugated core sandwich panels with the rectangular core. The non-integrated sandwich panels were reinforced with conventional 2-D fabrics in which resin provides the bond between core and skins. The integrated sandwich panels were reinforced with 3-D weft knitted fabrics in which bonding of the core wall to skins was carried out by combined efforts of knitted loop and resin. Using weft knitting technical capabilities, samples of the integrated and non-integrated structures were manufactured with the uppermost degree of resemblance in terms of geometry and mass. Flexural stiffness and transverse shear rigidity of the structures based on the known and unknown facing modulus of ASTM D7250 standard and Nordstrand–Carlsson methods were calculated. The estimated elastic constants based on unknown facing modulus and the Nordstrand–Carlsson methods were found to be highly compatible. However, the unknown facing modulus method is prone to disclose the statistical significant differences between the elastic constants of the structures with fewer tests. Regarding the unknown facing modulus method, it was found that the flexural stiffness and transverse shear rigidity of the non-integrated structure in the direction of corrugation were higher than those of the integrated structure. Results also indicated that the load-carrying capacity in the direction of corrugation was significantly higher in case of the non-integrated rectangular core structure compared with that of the integrated structure.
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