http://www.revmaterialeplastice.ro MATERIALE PLASTICE ♦54♦No. 4 ♦2017 639 Experimental Research on the Triangular Lattice Type Polymer Based Composites Structures for Sandwich Panels Construction ADRIAN COSTIN DURBACA 1 , RADU IATAN 1 , ION DURBACA 1 *, ALIN DINITA 2 , MARIUS VASILESCU 3 1 University Politehnica of Bucharest, Faculty of Mechanical Engineering and Mechatronics, 313 Splaiul Independenei, 060042, Bucharest, Romania 2 Petroleum Gas University of Ploiesti, Faculty of Mechanical and Electrical Engineering, 39 Bucuresti Blvd., 100520, Ploiesti, Romania 3 University Politehnica of Bucharest, Faculty of Material Science and Engineering, 313 Splaiul Independenei, 060042, Bucharest, Romania 4 University Politehnica of Bucharest, Faculty of Biotechnical Systems Engineering, 313 Splaiul Independenei, 060042, Bucharest, Romania The paper presents experimental results on the mechanical behaviour for a polymer based composite sandwich panel tensile and bending tested, which uses, one by one, a cellular composite core fabricated by additive manufacturing of four different types of polymeric materials: ABS (acrylonitrile butadiene styrene), PC (polycarbonate), PLA (polylactide) and CF (polylactide + 40% carbon fibre), with the thickness of 3 and 5 m m . This research focuses on comparative analysis of the core thickness increase effect on the structure’s strength. Experimental tests carried out on standardized test-pieces with specialized laboratory equipment, are highlighting similar mechanical behaviour and are showing also an increase of composite stiffness with the increase of core thickness, at the same time, the arrangement of the cellular lattice structure has a significant effect on the structural strength. Keywords: composite structure, sandwich panel, cellular composite, additive manufacturing * email: ion.durbaca@yahoo.com.; Phone: 40723277389 Development of polymer composites sandwich lightweight and ultra-lightweight structures, used successfully in many industries (aeronautics, aerospace, Naval, railway, automotive etc.), represent a rising direction of scientific research. Cellular constructions made of polymer materials, metals and ceramics are now available, although prices are higher compared to standard products. Therefore, they continue to have a continuous introduction on the market, as a result of prosperous developments of manufacturing processes. Such mixes are used in a variety of applications: those from polymer and metal are used for sandwich panels, ranging from cheap doors up to advanced aerospace components; the metal was also used successfully for energy absorption (e.g., landing feet module of Apollo 11 orbiting station were made of aluminium composite sandwich panel with high compression properties) [1], and sandwich composites from ceramic materials have applications in processes involving high temperatures (for example, accelerators and catalytic heat exchangers) [2]. Also, many natural materials (such as wood) can be analysed as idealized honeycomb structures [3]. The word cell derives from the Latin cella , a small compartment or an enclosed space. In the case of groups of cells, which the Romans called cellarium , a less elegant translation is solid cells. After Gibson and Ashby [4], a cellular solid is composed of an interconnected system of solid ties or plates that form the edges and faces of cells. For the construction of a polymer composite sandwich panel are generally involved three main components (fig. 1): two polymer facings, with the same thickness, a rigid and strong structure, separated by a thick light cellular structure in comparison with outer facings [5-8]. In the literature, the structure of the cell is known as core, due to its location in an assembly comprising the sandwich core in two sheets disposed one on the either side of the cellular core. As part of the sandwich panel, can be considered the addition between core and facings, resulting from joining methods (example: bonding with adhesives in thin film layer and ultra-sticky). This additional ultra-thin layer forces the core and facings to behave as a whole structure, thus transferring axial and transverse loads to and from cellular core. Cellular core requires enough stiffness to keep a constant distance between the facings. From a structural point of view, the main function of the cellular core in the sandwich structure is to stabilize the facesheets to avoid buckling and deformation and to take the shear loading along its thickness. Facesheets are transferring the tension and compression stresses. Their main function is to offer higher bending stiffness and plane shear to the sandwich structure. The facesheets also carry a part of local stresses. Fig. 1. The layer’s structure of a composite sandwich panel [10, 23]