Abstract
Poly(lactic acid) is not only one of the most often used materials for 3D printing via fused deposition modeling (FDM), but also a shape-memory polymer. This means that objects printed from PLA can, to a certain extent, be deformed and regenerate their original shape automatically when they are heated to a moderate temperature of about 60–100 °C. It is important to note that pure PLA cannot restore broken bonds, so that it is necessary to find structures which can take up large forces by deformation without full breaks. Here we report on the continuation of previous tests on 3D-printed cubes with different infill patterns and degrees, now investigating the influence of the orientation of the applied pressure on the recovery properties. We find that for the applied gyroid pattern, indentation on the front parallel to the layers gives the worst recovery due to nearly full layer separation, while indentation on the front perpendicular to the layers or diagonal gives significantly better results. Pressing from the top, either diagonal or parallel to an edge, interestingly leads to a different residual strain than pressing from front, with indentation on top always firstly leading to an expansion towards the indenter after the first few quasi-static load tests. To quantitatively evaluate these results, new measures are suggested which could be adopted by other groups working on shape-memory polymers.
Highlights
The most frequently used 3D printing materials for the fused deposition modeling (FDM) technique, i.e., acrylonitrile butadiene styrene (ABS), poly(lactic acid) (PLA) and a few others, often cannot reach the desired mechanical properties and the low surface roughness and waviness which are necessary in some applications [7,8,9]
We investigated the influence of the infill pattern and degree on the mechanical properties of 3D-printed cubes under a quasi-static load [23,24] and found the so-called gyroid infill to show promising recovery properties
Square specimens 3D-printed from the shape-memory polymer PLA were subjected to repeated pressure tests, using a modified three-point bending test
Summary
The most frequently used 3D printing materials for the fused deposition modeling (FDM) technique, i.e., acrylonitrile butadiene styrene (ABS), poly(lactic acid) (PLA) and a few others, often cannot reach the desired mechanical properties and the low surface roughness and waviness which are necessary in some applications [7,8,9].
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