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Fused filament fabrication (FFF) is a popular technique in rapid prototyping capable of building complex structures with high porosity such as cellular solids. The study of cellular solids is relevant by virtue of their enormous potential to exhibit non-traditional deformation mechanisms. The purpose of this study is to exploit the benefits of the FFF technology to fabricate re-entrant honeycomb structures using thermoplastic polyurethane (TPU) to characterize their mechanical response when subjected to cyclic compressive loadings.

Specimens with different volume fraction were designed, three-dimensionally printed and tested in uniaxial cyclic compressions up until densification strain. The deformation mechanism and apparent elastic moduli variation throughout five loading/unloading cycles in two different loading orientations were studied experimentally.

Experimental results demonstrated a nonlinear relationship between volume fraction and apparent elastic modulus. The amount of energy absorbed per loading cycle was computed, exhibiting reductions in energy absorbed of 12%–19% in original orientation and 15%–24% when the unit cells were rotated 90°. A softening phenomenon in the specimens was identified after the first compression when compared to second compression, with reduction in apparent elastic modulus of 23.87% and 28.70% for selected samples V₃ and H₃, respectively. Global buckling in half of the samples was observed, so further work must include redesign in the size of the samples.

The results of this study served to understand the mechanical response of TPU re-entrant honeycombs and their energy absorption ability when compressed in two orientations. This study helps to determine the feasibility of using FFF as manufacturing method and TPU to construct resilient structures that can be integrated into engineering applications as crash energy absorbers. Based on the results, authors suggest structure’s design optimization to reduce weight, higher number of loading cycles (n > 100) and crushing velocities (v > 1 m/s) in compression testing to study the dynamic mechanical response of the re-entrant honeycomb structures and their ability to withstand multiple compressions.

The purpose of this paper is to study the feasibility of the fabrication of circle arc curved-layered structures via conventional fused deposition modeling (FDM) with three-axis machines and to identify the main structural parameters that have an influence on their mechanical properties.

Customized G-codes were generated via a script developed in MATLAB. The G-codes contain nozzle trajectories with displacements in the three axes simultaneously. Using these, the samples were fabricated with different porosities, and their influence on the mechanical responses evaluated via tensile testing. The load-displacement curves were analyzed to understand the structure-property relationship.

Circled arc curved-layered structures were successfully fabricated with conventional three-axis FDM machines. The response of these curved lattice structures under tensile loads was mapped to three main stages and deformation mechanisms, namely, straightening, stretching and fracture. The micro-structure formed by the transverse filaments affect the first stage significantly and the other two minimally. The main parameters that affect the structural response were found to be the transverse filaments, as these could behave as hinges, allowing the slide/rotation of adjacent layers and making the structure more shear sensitive.

This paper was restricted to arc-curved samples fabricated with conventional three-axis FDM machines.

The FDM fabrication of curved-structures with controlled porosity and their relation to the resulting mechanical properties is presented here for the first time. The study of curved-lattice structures is of great relevance in various areas, such as biomedical, architecture and aerospace.