Investigation of the mechanical properties of sandwich composite plates produced by additive manufacturing method

Trapezoidal composite sandwich structures are preferred due to their lightweight nature and high flexural and compressive strength. In addition, their resistance to chemicals and water—depending on the materials from which they are manufactured—provides versatility for applications such as screwing, drilling, joining, and repair. These advantages have led to their widespread use across various industries, including automotive, aerospace, light commercial vehicles, marine, high-speed trains, construction, packaging, wind energy, and solar panels. Sandwich structures are composite elements composed of a core structure bonded between upper and lower face sheets. The face sheets are typically thin, stiff, and high in density, whereas the core is relatively thicker and made of low-density materials. Such structures are the subject of extensive research and development, particularly aimed at achieving high mechanical performance under compressive and flexural loading. In the scope of this thesis, three different levels were defined for the parameters of cell width and cell wall thickness, and core structures were fabricated from polylactic acid (PLA) filament using a three-dimensional (3D) printer. The top and bottom face sheets were manufactured using an additive manufacturing method from a composite material called PLA/CF, which contains 15–20% carbon reinforcement. The produced specimens were assembled using an epoxy-based adhesive. Sandwich composite plates were fabricated in both single- and double-layer configurations, and their mechanical properties were investigated through experimental methods. In the study, five process parameters were selected: printing speed, infill density, cell width (Dc), cell wall thickness (tc), and trapezoidal base angle. The respective parameter values were defined as follows: speed: 75/100/125 mm/s, infill: 70/85/100%, Dc: 6/9/12 mm, tc: 0.8/1.2/1.6 mm, and trapezoidal base angle: 55/65/75 degrees. Based on these values, trapezoidal cell geometries were produced. Compressive and three-point bending tests were performed on both single- and double-layer specimens. Comparative tests were subsequently conducted with sandwich plates manufactured using 100% carbon fiber-reinforced plates, based on the optimum results obtained from the initial experiments. The experimental data were evaluated using the TAGUCHI design of experiments method, and the results were statistically analyzed using analysis of variance (ANOVA). This study is one of the few that examines the holistic effect of production parameters in sandwich structures with trapezoidal cell geometry. The comparative analysis of single- and double-layered structures adds novelty to the literature. The use of PLA/CF material with 3D printing is a unique application for additive manufacturing. The findings directly contribute to structural design and optimization processes.