Examination of isotropy assumption in isogrid structures through analysis and experimentation on four isogrid variations

Abstract

An isogrid is a lattice structure with a high strength to weight ratio making it an ideal structure for spacecraft. Isogrids were originally designed to yield isotropic properties; however, recent finite element analyses show that isogrids do not exhibit isotropic behavior. Isogrids are theorized to be isotropic because of the equal distribution of stresses induced by the structure’s geometry. To determine the isotropy of an isogrid, truss and finite element analyses are executed to predict failure among four various isogrid specimens. The isogrid specimens are 3D printed and vary in geometry to determine the effect of geometric parameters on the isotropy of the structure. In addition, experimental tests are conducted by applying compressive loads to the specimens using a universal testing machine (UTM) with digital image correlation (DIC) to measure strain. The analyses indicate that isogrids are not isotropic because of the observed unequal load distributions.