Deformation of auxetic structures under bending load

V diplomskem delu se poglobimo v področje avksetičnih celičnih materialov. Opisane so lastnosti avksetičnih celičnih struktur, deformacije pri osni obremenitvi in pri upogibni obremenitvi. Navedenih in opisanih je več vrst avksetičnih struktur. Namen naloge je ugotoviti deformiranje avksetičnih struktur pri upogibni obremenitvi v primerjavi s konvencionalnimi strukturami, ki izkazujejo pozitivno Poissonovo razmerje. V ta namen smo pripravili modele treh avksetičnih struktur: vbočeno satovje, kiralno strukturo in strukturo manjkajočih reberter dve konvencionalni geometriji s šestkotno (satovje) in štirikotno (rešetka) strukturo. Vsem smo določili enake materialne lastnosti in jih v programskem paketu Abaqus CAE, upogibno obremenili ter analizirali po metodi končnih elementov. Določili smo ustrezno velikost mreže in preverili vpliv anizotropije ter debeline sten na rezultate simulacije. V rezultatih simulacij smo sledili pomike neobremenjenih delov strukture in jih primerjali med strukturami. Ugotovili smo, da se avksetične strukture obnašajo drugače od konvencionalnih kadar jih upogibno obremenimo. Le-te izkazujejo bolj sinklastično deformiranje kot konvencionalne strukture in izrazito pokažejo vpliv avksetičnosti na deformiranje pri upogibni obremenitvi.In the diploma work, we focus on the field of auxetic cellular materials. Properties of the auxetic cell structures and the deformation mechanism sunder axial load, as well as under bending load are described. Several types of auxetic structures are presented. The purpose of this assignment is to determine the deformation of the auxetic structures under bending load, compared to the conventional structures with positive Poisson\u27s ratio. To this end, we prepared models of three auxetic structures: auxetic honeycombs, chiral structure and missing rib structure, aswell as two conventional geometries with hexagonal (honeycomb) and square (grid) structure. We defined the same material properties for each of them and subjected them to bending load. Simulations are performed and analysed in software package Abaqus CAE based on the finite elements method. We determined the suitable size of the mesh of finite elements and observed the influence of anisotropy and wall thickness on the simulation results. We focused on the displacement of the unloaded corners of the structure and we compared different structures. We have found that auxetic structures behave differently from the conventional when structures are exposed to bending load. The former express more synclastic deformation than conventional structures and show the influence of the auxetic properties on deformation under bending load