Abstract
The influence of the microstructural arrangement of 3D-printed polylactic acid (PLA) on its mechanical properties is studied using both numerical and experimental approaches. Thermal cycling during the laying down of PLA filament is investigated through infra-red measurements for different printing conditions. The microstructure induced by 3D printing is determined using X-ray micro-tomography. The mechanical properties are measured under tensile testing conditions. Finite element computation is considered to predict the mechanical performance of 3D-printed PLA by converting the acquired 3D images into structural meshes. The results confirm the leading role of the printing temperature on thermal cycling during the laying down process. In addition, the weak influence of the printing temperature on the stiffness of 3D-printed PLA is explained by the relatively small change in porosity content. However, the influence of the printing temperature on the ultimate properties is found to be substantial. This major influence is explained from finite element predictions as an effect of pore connectivity which is found to be the control factor for tensile strength.
Highlights
Polylactic acid (PLA) is by far the most studied biosourced feedstock material for polymer-based additive manufacturing [1,2,3]
The method considered in this study provides an estimated correction of the proper evaluation of the mechanical properties of the interlayer bonding can be attempted to derive material based on finite element computation
The laying down process of PLA filament in a typical Fused DepositionModelling (FDM) process occurs with rapid thermal cycling and cooling rates as large as 8 ◦ C/s
Summary
Polylactic acid (PLA) is by far the most studied biosourced feedstock material for polymer-based additive manufacturing [1,2,3]. PLA exhibits a remarkable ability for thermo-forming under low processing temperatures compared to other feedstock polymers The thermal kinetics during printing especially the consequent crystallisation behaviour of PLA is significantly affected by its tacticity and chemical composition. In this regard, the influence of the glass transition, the degree of crystallinity, and melting temperature were investigated. It is well known that printing parameters that influence the thermal cycling during the printing process have a significant effect on the polymer relaxation trend This is true when the semi-crystalline nature of feedstock PLA leads to slower crystallization behavior compared to the rapid thermal cycling undertaken during the laying down process [4]
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