Experimental study on the post-yield responses and crushing patterns of additively manufactured Rhombic Dodecahedron lattices in biaxial compression

The flexibility of additive manufacturing facilitates the design and characterisation of numerous lattice configurations for enhanced energy absorption. As lattices sustain complex loading conditions in protective applications, it is essential to ascertain the multi-axial compressive behaviours of lattice structures by experiments. In this study, a homemade biaxial testing machine equipped with customised testing rigs was employed to prescribe direct compression along two perpendicular axes of lattices. The compressive responses of the bending-dominated Rhombic Dodecahedron lattice, fabricated via Fused deposition modelling with polylactic acid filaments, were examined by uniaxial compression, uniaxial compression with lateral expansion constrained, and equi-biaxial compression. The stress-strain responses and crushing patterns of the RD lattices subjected to the three stress states are analysed. It is found that the plateau stress levels of the RD are enhanced by preventing it from lateral expansion. Furthermore, simultaneously augmented strengths along two perpendicular axes are attained by the lattice subjected to biaxial compression, with more deformation localisation bands emerging. In addition, the energy absorption capacity of the RD lattice is also evaluated under various loading conditions. It is concluded that a larger amount of energy can be dissipated under biaxial compression, attributed to the more plastic crushing zones observed during finite deformation. The experimental study can provide new insights into novel lattice designs for energy dissipation in practice.