Joining mechanisms and mechanical properties of PA composites obtained by selective laser sintering

Abstract

Purpose-Additive manufacturing is today a viable industrial solution alongside traditional processes. Techniques like selective laser sintering (SLS) address the issues of digital production and mass customization in a variety of materials. Composite parts can be obtained with specific functional and mechanical properties. Building orientation during additive manufacturing often causes anisotropy of parts' properties that is still unspecified in technical information. The purpose of this paper is to investigate the mechanical performances and failure mechanisms of an aluminium-filled polyamide and of a new alumina-polyamide composite produced by SLS, in comparison with unfilled PA. Design/methodology/approach-A specific focus is set on the evaluation of primary and secondary anisotropy in the case of metal or ceramic filler, as well as on the specific contribution of powder distribution modes and joining phenomena. Macroscopic mechanical tests and the observation of joining and failure micro-mechanisms are integrated. Findings-The results prove the absence of relevant anisotropy amongst specimens that are produced with the axis parallel to the plane of powder deposition. Samples whose axis is parallel to the growth direction Z, instead, reveal a significantly different response with respect to other orientations. Originality/value-An original explanatory model is assumed and validated, based on an anisotropic distribution of the reinforcing particles during parts' production, which determines the efficacy of the strengthening mechanisms during crack propagation.

Process for reinforcing SLS parts by epoxy resin

“…Similar conclusions related to anisotropy in the growth direction (z axis) are observed in the research carried out by Berti et al (2010) applied to PA-Al2O3 composite for selective laser sintering (SLS) and in the work carried out by E. Bassoli et al (2012) in the case of metal or ceramic filler. In conclusion either the design or the material of SLS part has to be changed if this technology is wanted to be used for this kind of clutch pedal.…”

Structural characterization of biomedical Co–Cr–Mo components produced by direct metal laser sintering

“…The "M&M" and "Results" parts should be organized in subunits, each used technique has to be described separately and consequently numbered. A: "e tio Materials a d ethods a d "e tio Results are di ided i su se tio s. The results obtained by each different characterisation technique are reported separately (p. [6][7][8][9][10][11][12][13][14][15][16][17].…”

“…Direct metal laser sintering (DMLS) is an AM process that uses the heat of a solid state laser to sinter metal powder particles [5]. In this case, a distribution mechanism pre-places successive layers of powder on a suitable substrate, while a laser beam controlled by a scanning system locally sinters the powder in accordance with the CAD model [6]. This technology, like other AM procedures, is highly rewarding in medicine where a high degree of personalization is required [7][8][9].…”

Modeling of selective laser sintering/selective laser melting

“…This is one of the major barriers to prevent the broader adoption of SLS as a truly dependable manufacturing process. For example, same design with different build orientations can cause significant differences in mechanical properties and failure mode because of the anisotropy of SLS process [9]. This also contributes to the high manufacturing cost of SLS parts because equipment, processing recipe and material were controlled by a limited number of companies.…”