PSI - Issue 28

Manuel Sardinha et al. / Procedia Structural Integrity 28 (2020) 358–363 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 4. Example of tested specimens. (a) Test specimen without seam, sample NS_-_3; (b) Test specimen with a 10 mm seam, sample S_10_1.

Fig. 5. Example of the fractured surface of tested specimens. (a) Test specimen without seam, sample NS_-_3; (b) Test specimen with a 10 mm seam, sample S_10_1. 4. Conclusions In this work the influence of seams in the mechanical properties of PLA samples produced with two independent extrusion modules is evaluated. The existence of multiple independent extrusion modules imposes the existence of intersections areas in parts and these intersections are treated as seams. On average, tensile strength of specimens with a seam is 7 to 12 % lower than specimens without one. Samples manufactured with no seam continued to sustain the applied load undergoing plasticity while in samples with seam, rupture of the specimens is coincident with the elastic limit of the material. The seam dimensions show to have little influence on the tensile strength of specimens, with the average values varying between 49.16 MPa for samples with seam without overlap and 46.69 MPa in samples with a 10 mm overlap. Samples with 20 mm overlap have an average tensile strength of 48.99 MPa . The results suggest that in material extrusion, the seams act in a part by creating a localized fragility preventing it from entering a plastic domain and diminishing its tensile properties. Accordingly, seams could also be considerate in the design stage of a product since its location placement can act as a mechanical fuse. The results lay ground for further studies on the subject, which can be focused on seam properties, geometry and toolpath planning. Authors conclude that the development of multiple extrusion manufacturing, with the goal of reducing large parts manufacturing time without compromising geometrical accuracy is worthy of studying. Acknowledgements This work was supported by Fundação para a Cíência e Tecnologia, through IDMEC, under LAETA project, UIDB/EMS/50022/2020. Nuno Frutuoso and Carlos Vicente gratefully acknowledge their research grants and the funding of the BigFDM project, reference PTDC/EME-EME/32103/2017. Manuel Sardinha acknowledges the MOBILE-PRO-U/ADIST project, Reference 1802P.00306 for his research grant.