التحقيقات النظرية والتجريبية لألواح الطباقية المطبوعة ثلاثية الأبعاد المستخدمة في هيكل الطائرة

Theoretical and Experimental Investigations of 3D-Printed Sandwich Panels Used in Aircraft Structure

Abstract

Sandwich panels, which often consist of two face sheets attached to a honeycomb or foam core. Sandwiches have been utilized in a variety of applications, such as wind energy systems, ships, and aircraft. In this study, the regular hexagonal honeycomb core type is studied utilizing the available analytical solutions that involve finding the relation between core density and the total deflection of sandwiches under bending loads. Whereas, in a practical study, sandwich samples with various core densities were manufactured in regular hexagonal, triangular, and overlapped octagonal core configurations, utilizing 3D printing technology with the PLA (polylactic acid) material by adjusting the core density value to three magnitudes (105 kg/m3, 132 kg/m3, and 160 kg/m3) using cell size as the sole governing parameter in density value. These samples are subjected to a flexural test according to the standard (ASTM C393-00) to find deflection, stiffness, and consequently the effect of variation in core density for each type. Then, the theoretical conclusions, followed by experimental test results, are compared with the numerical results generated by the simulation software “Ansys” to provide a clear idea of how the density of the core will impact the mechanical characteristics of the sandwich and reveal the superior core type. Additionally, impact resistance is significantly influenced by core density variation, so to explore that, samples with different core densities were subjected to the simulation of a tower drop test. Moreover, a numerical evaluation was carried out to determine the effect of core density on natural frequencies and explore the behavior of sandwiches under repeated loads. Finally, the experimental results demonstrate that an increase in core density by 25.7% and 52.4% leads to more stiffness by 8.14% and 16.75% in a hexagonal core, 8.43% and 28.1% in a triangular core, and 10.94% and 19.04% in an octagonal core. Besides, the overlapped octagonal and triangular cores are more stiff than hexagonal. Regarding impact exploration, it can be deduced that increasing the density of the core increased the sandwich’s resistance to impacts and that the regular hexagonal core has greater impact resistance than the triangular core. Additionally, the results show that increases in core density of 25.7% and 52.4% lead to a slight drop in the value of natural frequencies, at least in the first mode.