Experimental and numerical analysis of the shear nonlinear behaviour of Nomex honeycomb core: Application to insert sizing

Abstract

numerical analysis of the shear nonlinear behaviour of Nomex honeycomb core: Application to insert sizing. Composite Structures, Elsevier, 2018, vol. 193, pp. 121-139. 10.1016/j.compstruct.2018 A B S T R A C TThis work is a contribution to the understanding of the nonlinear shear behaviour caused by cell postbuckling in Nomex honeycomb cores. First, an experimental benchmark study was made of different designs for the shear testing of honeycomb cores. Then, several test specimens were fabricated and tested, a 3D DIC system being used to measure and record the displacements. An Artificial Neural Network (ANN) was also used to identify the onset of bucking and collapse of the cells. The influence of the overall boundary conditions of shear tests on the buckling of the cells is presented both experimentally and numerically. The reversibility and test procedure results suggest that it may be possible to allow the shear strength to be increased by up to 35% under certain conditions.

Damage Mechanics Modelling of the shear nonlinear behavior of Nomex honeycomb core. Application to sandwich beams

“…In this section, the main aspects of the phenomenological description of the honeycomb core presented in [1] are discussed. When the honeycomb structure is subjected to shear loads, the overall nonlinear response of the structure can be explained by two different phenomenological stages: an initial buckling and the final collapse of the cells.…”

“…This is shown in Figure 2, where the percentage of cells that were about to buckle increases gradually with gamma. These curves were determined in [1] where an Artificial Neural Network (ANN) was developed to detect the collapse of the cells from the data collected by a 3D-DIC that was used to record the experiments. This collapse stage takes place once the cells have buckled due to geometric imperfections, for example, variations in the thickness of the walls or the size and localization of deformations on the wall.…”

“…In [1], it was stated that buckling and collapse of the cells were two different stages. In this work, it is considered that a superposition of the two stages should describe the complete behavior of the honeycomb core for the W and L directions.…”

“…Nevertheless, recently, a detailed study of the shear behavior of the HRH-78 Nomex honeycomb core was made through experimental and numerical modeling [1]. The authors described the general behavior of the honeycomb core and the shear buckling of the cells and it was proved that the nonlinear response of the honeycomb core and the buckling evolution of the cells were strongly influenced by the boundary conditions.…”

“…Considering all the information mentioned above, the purpose of the present research is to provide a simple but accurate strategy for modeling the honeycomb core for the shear case, starting from the observations made in [1] as they are very helpful to understand the general aspects of the structural behavior of hexagonal cells under shear forces.…”