Evaluation of the influence of design in the mechanical properties of honeycomb cores used in composite panels

Abstract

The aerospace, automotive, and marine industries are heavily reliant on sandwich panels with cellular material cores. Although honeycombs with hexagonal cells are the most commonly used geometries as cores, recently there have been new alternatives in the design of lightweight structures. The present work aims to evaluate the mechanical properties of metallic and polymeric honeycomb structures, with configurations recently proposed and different in-plane orientations, produced by additive and subtractive manufacturing processes. Structures with configurations such as regular hexagonal honeycomb (Hr), lotus (Lt), and hexagonal honeycomb with Plateau borders (Pt), with 0°, 45°, and 90° orientations were analyzed. To evaluate its properties, three-point bending tests were performed, both experimentally and by numerical modeling, by means of the finite element method. Honeycombs of two aluminum alloys and polylactic acid were fabricated. The structures produced in aluminum were obtained either by selective laser melting technology or by machining, while polylactic acid structures were obtained by material extrusion using fused filament fabrication. From the stress distribution analysis and the load–displacement curves, it was possible to evaluate the strength, stiffness, and absorbed energy of the structures. Failure modes were also analyzed for polylactic acid honeycombs. In general, a strong correlation was observed between numerical and experimental results. The results show that the stiffness and absorbed energy increase in the order, Hr, Pt, Lt, and with the orientation through the sequence, 45°, 90°, 0°. Thus, Lt structures with 0° orientation seem to be good alternatives to the traditional honeycombs used in sandwich composite panels for those industrial applications where low weight, high stiffness, and large energy-absorbing capacity are required.

Experimental and numerical study of transverse shear modulus for bioinspired glass fiber‐reinforced polymer sandwich core

“…Miranda et al [ 20 ] investigated the stress distributions and failure modes of the conventional hexagonal honeycomb (Hr) and lotus (Lt) structure. Lt structure with 0 0 orientation has a sizeable energy‐absorbing capacity than traditional honeycombs.…”

“…Achieved results show that some of the proposed geometries may be promising alternatives to the more traditional structures. Schwingshackl et al [20] Present…”

Functionally graded cellular cores of sandwich panels fabricated by additive manufacturing

“…5 However, the use of foams is limited as they possess an irregular random microstructure due to the fabrication procedures. Thus, honeycomb and truss based lattices become attractive for the cores of the panels 9-15. Among the honeycomb type, periodic hexagonal cellular structures are dominant 2,16 although new core designs have been recently proposed to compete with the conventional hexagonal 1 ones 8,[17][18][19] particularly in attempting to improve the in-plane properties. 20,21 In the continuous search for achieving advanced materials with enhanced properties, a new class, known as functional gradient materials (FGMs) has emerged based on the characteristics of natural materials.…”

“…47 Material extrusion allows printing several materials, being one of the most used polymers the polylactic acid, which is a biodegradable aliphatic polyester. 48 Recently, the lotus (Lt), hexagonal honeycomb with Plateau borders (Pt) structures proposed by Ronan et al, 49 were adapted by Araújo et al, 8 Miranda et al 18 and Araújo et al, 50 to the core of sandwich panels and compared with the regular hexagonal honeycomb (Hr), as exemplified in Figures 1 and 2.…”

Assessing the influence of DMLS production process factors on fatigue resistance of Maraging steel MS1 in the finite life domain using ANN prediction abilities

“…The key advantage of additive manufacturing (AM) technologies for mechanical designers is their ability to manufacture functionally graded parts 1 and products with internal open spaces, 2 which enables topology optimization of product shape 3 and, consequently, design of lightweight components 4 and products with shape-integrated functionality. 5 Direct Metal Laser Sintering (DMLS), as the AM technology capable of manufacturing metal products, is increasingly used to implement the advantages of AM in automotive and aerospace industry.…”