Finite Element Analyzing of the Effect of Crack on Mechanical Behavior of Honeycomb and Re-entrant Structures

Abstract

Developments in technology require the new materials, lighter and more efficient structures and also new manufacturing methods. In this study, after doing researches about topology optimization, regular honeycomb and re-entrant structures; the regular honeycomb and re-entrant structures were designed, and then Ti-6Al-4V material was chosen for these structures in finite element (FE) analyzing. The three different rib thickness values (t) of 1 mm, 1.5 mm and 2 mm were assigned for honeycomb and re-entrant structures in FE analyses. Also, the crack was created on the models, and then 2-D FE analyses were done for both cracked and un-cracked honeycomb and re-entrant structures under tensile forces through y axis. Afterwards, the effect of crack on stress intensity factor, stresses, strains and displacement were obtained and characterized the auxetic behavior of the regular honeycomb and re-entrant structures. Furthermore, increase in rib thickness decreases stress and strains for each structure. Moreover, re-entrant structures have negative Poisson's ratio due to their geometric properties and the notable effect of crack on the equivalent stress in re-entrant was emerged in comparison with honeycomb structure. As a result, the only possible fracture in honeycomb for thickness of 1 mm might be observed owing to stress intensity factor obtained from analyses bigger than fracture toughness of honeycomb structure.