Material extrusion-based additive manufacturing of structurally controlled poly(lactic acid)/carbon nanotube nanocomposites

The mesostructure of additively manufactured nanocomposite parts can be tailored by the manipulation of process parameters to improve the properties of the final part. The effects of contributing process parameters and their interactions must be identified to be able to tune the properties of additively manufactured (3D-printed) nanocomposites based on their intended applications. Herein, we present the characterization of the effect of three major building parameters, namely layer thickness, infill percentage, and infill pattern, on mechanical and thermal properties of 3D-printed poly(lactic acid) (PLA)/carbon nanotube (CNT) nanocomposites. The characterization of printed parts showed that increasing layer thickness had a deteriorating effect on the mechanical properties regardless of the CNT concentration; however, the Young's modulus and tensile strength of parts were improved by increasing the CNT content in the same design of mesostructure. Moreover, the thermomechanical analysis showed that the residual thermal stresses of 3D-printed nanocomposites increased by increasing the layer thickness. Furthermore, it was shown that decreasing infill percentage resulted in a non-linear reduction of stiffness, strength, and dimensional stability. Moreover, a honeycomb-shaped infill pattern was introduced for the manufacturing of parts, which has shown more isotropic mechanical properties. The contributions of CNTs in enhancing mechanical properties of 3D-printed nanocomposites were investigated, by considering the induced reinforcing effects as well as the alteration of the crystallization behavior of PLA.