Degradation in Cellular Core Mechanical Properties due to Transverse Compression

Abstract

Manufacturing defects, which occur often in cellular cores of sandwich structures, lead to buckled cells in the core and thus to degraded constitutive core properties. Defects in the core cells may occur due to unintentional tool impacts onto the panel during manufacturing, handling processes, or defects in the manufactured core itself. The degraded constitutive properties of the core lead to local stiffness degradations of the sandwich panel, which in turn may impact the capability of nearby inserts; inserts are often used for component mounting to the panel or as joints used for joining the sandwich panel with another panel. The aim of this paper is to: a) Understand the effect of core density on the critical buckling load/buckling capability of the unit cell for each of the three core shapes: hexagonal, square and triangular, b) Understand the effect of core height (core thickness within the sandwich panel) on the critical buckling load/buckling capability of the unit cell for each of the three core shapes, and c) Investigate the degradation in the constitutive properties of the cellular core due to permanent deformation resulting from transverse compression. Detailed finite element models for five cell sizes and twenty one core densities were created for each of the following cellular core shapes: hexagonal, square and triangular. The critical buckling load is calculated for all twenty one core densities and the five cell sizes under consideration for the hexagonal, square and triangular cellular cores. Additionally, the critical buckling load is calculated for four core heights from 0.25" to 1.00" core height with 0.25" increments to study the effect of the core height on the critical buckling load of the unit cell. The degradation of constitutive properties of the hexagonal, square and triangular cellular cores due to buckling under transverse compression loading for the 1/8″ cell size and core density of 3.1 pcf is studied for the 0.5″ core height cells. All cellular cores are assumed to be manufactured of corrugated Al-5056.

Effect of varying core density and material on the quasi‐static behaviors of sandwich structure with 3D‐printed hexagonal honeycomb core

“…Certain factors, including the fabrication techniques for the structure, the kind of structural design, and the type of materials used, can significantly alter the mechanical behavior of sandwich panel with cellular core. 9,10 In order to effectively utilize the AM method for sandwich structures, it is critical to comprehensively assess these factors and systematically perform rigorous evaluations of mechanical behavior, as highlighted in previous research. 11 Recent advances in AM technologies, including as selective laser melting (SLM) and fused deposition modeling (FDM), have made it possible to manufacture honeycomb structures with reduced feature and cell sizes.…”

“…The mechanical properties of these structures are a key factor in the development and manufacture of efficient sandwich structures. Certain factors, including the fabrication techniques for the structure, the kind of structural design, and the type of materials used, can significantly alter the mechanical behavior of sandwich panel with cellular core 9,10 . In order to effectively utilize the AM method for sandwich structures, it is critical to comprehensively assess these factors and systematically perform rigorous evaluations of mechanical behavior, as highlighted in previous research 11 …”

Comparative and parametric study of aluminium honeycomb sandwich composites and GRP

“…[11][12][13] Stefan et al 14 estimated the out of plane shear modulus of honeycomb core by using the finite element. Soliman and Kapania 15 and Soliman 16 found the elastic properties of different shapes of honeycomb by using a detailed finite element model of representative unit cells applying the displacement approach and proposed empirical relations. Studies on the failure modes of sandwich composites can be found in the literature.…”