In upholstery applications, it is common to use polyurethane (PUR) foam when flexibility is desired. However, as PUR is a carbon-based material produced using toxic isocyanates, it is environmentally beneficial to replace PUR with bio-based alternatives. The challenge, however, lies in finding suitable bio-based replacement materials, capable of mimicking the foam-like functionality of PUR since many are stiff and brittle. Therefore, instead of relying on the inherent material property, this paper explores the possibility of producing flexible foamlike structures from bio-based materials with additive manufacturing (AM) employed as the manufacturing technique. As one of the key design constraints associated with AM is the intrinsic material anisotropy in the build direction, this paper focuses on the effects of print orientation on the compressive behaviour of structure which is indicative of flexibility. Three open-celled strut-based lattice structures are chosen for this purpose and the effect of these cell topologies on the compressive behaviour of structures is studied. The scope of this work includes structures printed using selective laser sintering (SLS) in a bio-based polyamide material (PA 1101). The results show that material failure and deformation behaviour are affected by print orientation, while the amount of plastic deformation is more influenced by the lattice cell topology.
The as-built geometry and material properties of parts manufactured using Additive Manufacturing (AM) can differ significantly from the as-designed model and base material properties. These differences can be more pronounced in thin strut-like features (e.g., in a lattice structure), making it essential to incorporate them when designing for AM and predicting their structural behaviour. Therefore, the aim of this study is to develop a numerical model with realistic characteristics based on a thin strut-based test artefact and to use it accurately for estimating its compressive strength. Experiments on test samples produced by selective laser sintering in PA 1101, are used to calculate geometrical deviations, Young's modulus, and yield strength, which are used to calibrate the numerical model. The experimental and numerical results show that the numerical model incorporating geometrical and material deviations can accurately predict the peak load and the force-displacement behaviour. The main contributions of this paper include the design of the test artefact, the average geometrical deviation of the struts, the measured material data, and the developed numerical model.
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