EFFECTS OF HIGH ORDER DEFORMATIONS ON ELASTIC MODULUS AND COLLAPSE OF PLANAR LATTICE MATERIALS

摘要

Lattice materials have been attractive over the last decade for use as loadingcarrying structures,energy absorbing elements and heat exchanging structures fortheir superior mechanical properties and multifunctional characters.Thedeformation modes of perfect planar lattice materials show a rich diversityaccording to the magnitude of connectivity,including the bending and stretchingdominated modes.Noting that the quantitative influence of the high orderdeformations upon the elastic modulus and collapse of lattice materials which isimportant for their applications has been scarcely reported,an analyticalinvestigation of the elastic modulus and initial yield surface considering the highorder deformations is carried out for three typical planar lattice materials:hexagonal,Kagome and triangular lattices.The analytical results are validated bythe finite element (FE) simulations.Based on the analytical results,minimumweight designs of axially compressed hollow square columns made from planarlattice materials are performed,taking into account the failure mechanisms ofglobal column buckling,local plate buckling,local beam buckling and beamyielding.It is found that the effect of high order deformation on the elasticmodulus and yield strength increases with the relative density.The bending effectof the Kagome lattice is more obvious than that of the triangular one with thesame relative density and stress state.The yield strength of the Kagome latticecalculated by neglecting the bending effect overestimates the result by more than10% when the relative density is higher than about 11.1%.