Sandwich-walled cylindrical shells with lightweight metallic lattice truss cores and carbon fiber-reinforced composite face sheets

We manufactured sandwich-walled cylindrical shells with aluminum pyramidal truss core of constant curvature employing an interlocking fabrication technique for the metallic core. The skins were made of carbon-fiber reinforced composites and co-cured with the metallic truss core. Thereafter, we carried out axial compression tests on some representative samples to investigate the failure modes of these structures and compared with an analytical failure map developed to account for Euler buckling, shell buckling, local buckling between reinforcements and face-crushing. The experimental data closely matched the analytically predicted behavior of the cylinders. In particular, we found that local buckling and face crushing modes can exist together and are the most important modes of failure of the fabricated structure. Cellular structures have well-known advantages over their traditional homogenous counterparts ranging from higher strength-weight ratio to exceptional buckling resistance in addition to effective energy absorption, shock mitigation, dynamic resistance and heat insulation [1–8]. However, sandwich panels traditionally made from foam and honeycomb cores with close-cells [9] cannot accommodate free fluid movement through them. Therefore, this limit on flow circulation imposes significant restrictions in their thermal and transport properties, preventing their deployment as functional structures. Therefore, fabrication of sandwich panels having open-cell cores with interconnected void spaces have been suggested for extending structures for functional applications [10]. In this context, fiber reinforced composite sandwich panels with lattice core construction are of particular interest for aerospace and marine applications [11,12]. Significant advances in the manufacturing of the low-density lattice structures themselves, such as aluminum alloys [13–15], steel wires [16], polymers [17], self-propagating polymers [18], hollow-tube micro lattices [19] as well as fiber reinforced composites [20,21] have given even greater flexibility in adapting these structures to various operating conditions and design restrictions. There impressive advances must be contrasted with the fact that many structural components used in aerospace applications involve a curved geometry such as fuselage gloves, barrel sections, fuel tanks, some types of landing gear doors in space exploration vehicles and airplane fuselage [22]. Therefore, the flat topology of lattice truss core constructions is one of the key factors limiting their application in such structures underscoring the need for greater geometric flexibility. The current work extends the envelope of research by describing a novel yet practical manufacturing technique for fabricating cylindrical metallic lattice truss-core sandwich structures along with axial compression tests on some representative specimens. Sun et al. [23] investigated the response of carbon fiber composite sandwich …