Nanomechanical Testing Journal Club

Multiscale mechanical and tribological characterizations of additively manufactured polyamide 12 parts with different print orientations

by Tyler Palmaa, Michael Munthera, Praveen Damasusa, Sepehr Salarib, Ali Beheshtib, Keivan Davamia

Journal of Manufacturing Processes, 2019, 40, pp. 76-83

Additive manufacturing (AM) presents a new paradigm in small-scale, on-demand manufacturing of complex components. Some forms that can be produced with AM may not even be possible to produce through traditional machining or cutting and joining operations. However, the rapid heating and cooling often result in microstructures and properties that differ drastically from the parent material.

This paper explores the mechanics of one simple change in the 3D printing process and the layer printing orientation in a tensile dogbone-shaped specimen. These two orientations involve a 90-degree rotation in the print layer, resulting in one specimen printed in the tensile direction and one perpendicular to the tensile direction. The resulting tensile tests show a large variation in properties, with apparent failure occurring in between the build layers. The effects of the build layers are then then further explored using a variety of nanomechanical and nanotribological techniques. Effectively, the build layer orientation produces regions of high-modulus and high-strength, which are attributed to a higher bonding density. Alternatively, the ‘in between’ layers that sandwich these build layers has lower strength and lower bond density. 

This is a great engineering study based on fundamental structure-property-processing relationships that highlights some of the requirements in manufacturing additively manufactured components.