Marzio Grasso

TL;DR: In this paper, the authors quantify the ultimate tensile strength and nominal strain at break of printed parts made from polylactic acid (PLA) with a Replicating Rapid prototyper (Rep-Rap) 3D printer, by varying three important process parameters: layer thickness, infill orientation and the number of shell perimeters.

TL;DR: In this article, a full mechanical characterisation of three types of 3-D printed lattice cores was performed to evaluate the feasibility of using additive manufacturing of lightweight polymer-based sandwich panels for structural applications.

TL;DR: In this paper, the technical pathways for DRAM of complex polymer composites using a case study of windshield wiper blades were explored and a successful pathway for fabricating new products was found and the mechanical properties of the resultant components were quantified.

Abstract: Purpose Recent advancements of 3D printing technology have brought forward the interest for this technique in many engineering fields. This study aims to focus on mechanical properties of the polylactic acid (PLA) feeding material under different thermal conditions for a typical fusion deposition of 3D printer system. Design/methodology/approach Specimens were tested under static loading within the range 20oC to 60oC considering different infill orientations. The combined effect of temperature and filament orientation is investigated in terms of constitutive material parameters and final failure mechanisms. The difference between feeding system before and post-3D printing was also assessed by mechanical test on feeding filament to verify the thermal profile during the deposition phase. Findings The results in terms of Young’s modulus, ultimate tensile strength (UTS), strain at failure (ef) and stress at failure (σf) are presented and discussed to study the influence of process settings over the final deposited material. Fracture surfaces have been investigated using an optical microscope to link the phenomenological interpretation of the failure with the micro-mechanical behaviour. Experimental results show a strong correlation between stiffness and strength with the infill orientation and the temperature values. Moreover, a relevant effect is related to deformed geometry of the filament approaching glass transition region of the polymer according to the deposition orientation. Research limitations/implications The developed method can be applied to optimise the stiffness and strength of any 3D-printed composite according to the infill orientation. Practical implications To avoid the failure of specimens outside the gauge length, a previously proposed modification to the geometry was adopted. The geometry has a parabolic profile with a curvature of 1,000 mm tangent to the middle part of the specimen. Originality/value Several authors have reported the stiffness and strength of 3D-printed parts under static and ambient temperature for different build parameters. However, there is a lack of literature on the combination of the latter with the temperature effects on the mechanical properties which this paper covers.

TL;DR: In this paper, the Accepted Manuscript version of this paper has been published in Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, December 2016, doi: https://doi.org/10.1177/0954409716682629.