An investigation into the fracture behaviour of honeycombs with density gradients

In this study we perform an experimental and computational investigation about the fracture behaviour of polymer honeycombs presenting gradients in terms of lattice density. Such lattice relative density variations are introduced with the aim of mimicking the micro-morphology encountered in some natural materials, such as several kinds of woods, which seems related to the ability of the corresponding macro-material to delay the propagation of fracture under certain conditions. Starting from the conclusions of previous computational analyses, we perform a few experimental tensile tests on ABS model honeycombs obtained by additive manufacturing, with the aim of getting insights into their fracture behaviour and assessing the effect of the density gradients on the failure process, with respect to the behaviour observed in baseline homogeneous lattices. Following the performed tests, novel finite element analyses are carried out, to help explain the observed failure processes and as preliminary calibration for further investigations addressed at maximising the lattice fracture toughness under tensile loading. With the emerging of more reliable and affordable additive manufacturing technologies, the present study contributes to exploring the possibility of modifying the effective properties of honeycombs and lattice materials through sensible small modifications of the micro-morphology.