Compressive Strength of Sandwich Composite Plates with Trapezoidal Cells of Different Geometries, Manufactured by Additive Manufacturing

ABSTRACT In this study, the compressive strength of trapezoid composite sandwich structures with core cells made of polylactic acid filaments with three different cell widths (Dc) and cell wall thicknesses (tc) was investigated. The trapezoid composite sandwich structures were produced using a three-dimensional printer. The top and bottom surface plates were manufactured using an additive manufacturing method creating plates of composite material containing 15–20 % carbon fiber. The produced samples were assembled using epoxy adhesive. The compressive strengths of single- and double-layer sandwich composite plates were experimentally investigated. Four different parameters were identified: infill density, Dc, tc, and trapezoid base angle. The values used in fabrication for different parameters are as follows: speed (75/100/125 mm/s); infill density (70 %/85 %/100 %); Dc (6 mm/9 mm/12 mm); tc (0.8 mm/1.2 mm/1.6 mm); and finally, the trapezoid angle (55°/65°/75°). Trapezoidal cell geometries with these dimensions were used. Compression tests were performed on both single- and double-layer samples, and the Taguchi L27 experimental design was used to optimize the parameters. Signal-to-noise (S/N) ratios and analysis of variance were used for the numerical analysis of the experiments. The results of the experiments were compared based on the S/N ratios, and the parameter levels with the best results were determined. The base angle of the core cell had the largest effect on the experimental results, with a contribution of 60.46 %, followed by the base width of the core cell, which contributed 16.97 %. The lowest effect was observed for the printing speed (3.52 %) and infill rate (2.09 %). Additionally, the coefficient of determination was found to be R2 = 99.65 %.