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This article experimentally investigates the buckling strength of carbon fiber-reinforced polymer laminates. Samples were made with 16 layers of carbon fibers in four orientations of 0°, 30°, 60°, and 90°. Nano silica (SiO 2 ) and nano clay were used as fillers for enhancement of the buckling strength of carbon fiber-reinforced polymer laminates. The Taguchi method was used for design of experiments and optimizing the three input factors: nano silica, nano organoclay, and carbon fiber orientation. From the results, first, it was found that the most buckling strength belonged to the samples with the fiber orientation of 0°and the minimum strength belonged to the composite laminates with the 90°orientation of carbon fiber. Second, the use of two nano fillers in quaternary laminates (epoxy/carbon fiber/silica/clay) has increased the buckling strength of laminates about 45.5% and 22.5% in comparison with binary and ternary laminates, respectively. The binary laminates were made from carbon fiber/epoxy resin and the ternary laminates included carbon fiber/clay/epoxy. Third, the elastic modulus of laminates increased with an increase in the nano SiO 2 content. The most effective parameters according to the analysis of variance results were as follows: carbon fiber orientation, nano silica, and nano organoclay, with a probability value of 99%, 95%, and 90%, respectively. Finally, the analytical analysis was done according to the classical laminated plate theory for obtaining the buckling force and verifying and comparing the results with experimental buckling tests. The results obtained from classical laminated plate theory for two certain laminates were in excellent agreement with those obtained from experimental results.

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The present research has addressed the flexural and compressive strength of Kevlar fiber composite sandwich panels with novel lattice core, experimentally and numerically. The composite sandwich panels and corrugated cores have been made using the vacuum-assisted resin transfer molding method. Afterward, compressive and three-point bending loads were applied to the composite sandwich panels to determine mechanical performance during structural deformation. Scanning electron microscopy has been conducted on the specimens to evaluate the Kevlar-fiber distribution. In order to evaluate the experimental results, the corresponding testing process has been numerically simulated through finite element analysis. It has been figured out that the simulated model can predict the force–displacement response of the considered sandwich panels under bending and compressive loads. Finally, the effect of polyurethane foam on the composite sandwich panel's mechanical strength and energy absorption capacity has been investigated.

This research aims to design, manufacture, and determine the vibration characteristics of a composite sandwich panel with lattice cores. For this purpose, first, a glass fiber sandwich panel with lattice truss core has been fabricated in the laboratory. In this part, the vacuum-assisted resin transfer molding method has been used to achieve laminates without any porosity. Afterward, the modal tests have been performed to obtain the natural frequencies, shape modes, damping ratio, and frequency responses of the sandwich panel. In addition, a finite element analysis has been developed to calculate the natural frequencies, damping ratio, and mode shapes of the composite sandwich panel. Then the experimental data have been compared to numerical simulation, and good agreement has been found.