Deformation behaviour, limitations in design, applications, and additive manufacturing of hierarchical honeycombs

Abstract

Hierarchical honeycombs are particularly useful in aerospace industries because of their capability to overcome challenges related to bend-dominated behaviour. These structures are ideal for aeronautical applications because of their capacity to integrate lightweight design, good mechanical properties, and efficient load distribution. However, the efficacy under applied loads is influenced by the type of polygon cell typically introduced to the parent hollow structure. The current literature has gaps in knowledge regarding the highest order of hierarchy that can practically be achieved for hierarchical honeycombs with different cell shapes at the vertices or for the walls. This review paper documents work carried out on hierarchical honeycombs to examine their mechanical behaviour and how they can be efficiently designed. The first section of the paper highlights the deformation behaviour of hierarchical honeycombs in use today. The next section contains a discussion on the constraints in determining the order of hierarchy attainable for hierarchical honeycombs, particularly the geometric parameters. This is followed by a review of relevant applications for hierarchically built honeycomb parts in aerospace industries. The efficacy, as well as challenges related to using additive manufacturing in building hierarchical honeycombs, are then highlighted. Alternatives for future studies and advances in hierarchical honeycombs applied in the aerospace sector are addressed in the last section of the paper.