Mechanical properties of dense polylactic acid structures fabricated by three dimensional printing

This paper reports properties of four different filaments prepared from (i) virgin polylactic acid, (ii) polylactic acid reinforced with polyvinyl chloride, (iii) polylactic acid reinforced with wood powder, and (iv) polylactic acid with reinforcement of Fe3O4 prepared with twin-screw extrusion for possible multimaterial three-dimensional printing. The results suggest that the melt flow rate of composite increases with the increase in reinforcements except for wood powder, which has shown a negative trend. Mechanical properties were also reduced with the loading but with the increase in the Fe3O4 content, these properties were improved. It has been observed that with reinforcement of polyvinyl chloride from 10 wt% to 25 wt% peak elongation and break elongation were reduced by 47.61% and 50%, respectively. Further, thermal analysis suggests that all samples were stable but for reinforced samples, the integral energy has decreased significantly in successive cycles. The vibration sample magnetometery of samples suggested that magnetic properties were dependent on the content of Fe3O4 present in the composite.

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Effect of Three-dimensional Printing with Nanotubes on Impact Resistance

10.21203/rs.2.13707/v1 ◽

2019 ◽

Author(s):

Anne Schmitz

Keyword(s):

Mechanical Properties ◽

Lower Limb ◽

Impact Resistance ◽

Three Dimensional ◽

Three Dimensional Printing ◽

Impact Tester ◽

The Impact ◽

Dimensional Printing ◽

Pendulum Impact ◽

Pendulum Impact Tester

Abstract The types of biomedical devices that can be three-dimensional printed (3DP) is limited by the mechanical properties of the resulting materials. As a result, much research has focused on adding carbon nanotubes (CNT) to these photocurable polymers to make them stronger. However, there is little to no data on how CNTs affect the impact resistance of these polymers, an important property when designing and manufacturing lower limb prosthetics. The objective of this study was to expand the use of 3DP to prosthetics by testing the hypothesis that adding CNTs to a stereolithographic (SLA) photocurable resin will result in a cured polymer with increased impact resistance. Twenty-six total specimens: 13 with nanotubes and 13 without nanotubes, were printed on a Form2 SLA printer. Once all the specimens were printed, washed, and cured, the impact resistance was quantified using a pendulum impact tester in a notched Izod configuration. Contrary to the hypothesis, the specimens with SWCNTs (0.312 ± 0.036 ft*lb/in) had a significantly lower impact resistance compared to the non-SWCNT specimens (0.364 ± 0.055 ft*lb/in), U = 34.0, p = 0.004. This decreased impact resistance may be due to voids in the printed polymer around the aggregated nanotubes. Thus, SLA polymers still do not have the impact strength needed to be used for a full lower limb prosthetic.

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Remanufacturing of end-of-life glass-fiber reinforced composites via UV-assisted 3D printing

Rapid Prototyping Journal ◽

10.1108/rpj-01-2019-0011 ◽

2019 ◽

Vol 26 (6) ◽

pp. 981-992

Author(s):

Andrea Mantelli ◽

Marinella Levi ◽

Stefano Turri ◽

Raffaella Suriano

Keyword(s):

Mechanical Properties ◽

Circular Economy ◽

Three Dimensional ◽

Fiber Reinforced Composites ◽

Reinforced Composites ◽

Content Type ◽

Three Dimensional Printing ◽

Glass Fiber Reinforced ◽

Complex Shapes ◽

Dimensional Printing

Purpose The purpose of this study is to demonstrate the potential of three-dimensional printing technology for the remanufacturing of end-of-life (EoL) composites. This technology will enable the rapid fabrication of environmentally sustainable structures with complex shapes and good mechanical properties. These three-dimensional printed objects will have several application fields, such as street furniture and urban renewal, thus promoting a circular economy model. Design/methodology/approach For this purpose, a low-cost liquid deposition modeling technology was used to extrude photo-curable and thermally curable composite inks, composed of an acrylate-based resin loaded with different amounts of mechanically recycled glass fiber reinforced composites (GFRCs). Rheological properties of the extruded inks and their printability window and the conversion of cured composites after an ultraviolet light (UV) assisted extrusion were investigated. In addition, tensile properties of composites remanufactured by this UV-assisted technology were studied. Findings A printability window was found for the three-dimensional printable GFRCs inks. The formulation of the composite printable inks was optimized to obtain high quality printed objects with a high content of recycled GFRCs. Tensile tests also showed promising mechanical properties for printed GFRCs obtained with this approach. Originality/value The novelty of this paper consists in the remanufacturing of GFRCs by the three-dimensional printing technology to promote the implementation of a circular economy. This study shows the feasibility of this approach, using mechanically recycled EoL GFRCs, composed of a thermoset polymer matrix, which cannot be melted as in case of thermoplastic-based composites. Objects with complex shapes were three-dimensional printed and presented here as a proof-of-concept.

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Multimaterial printing and characterization for mechanical and surface properties of functionally graded prototype

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406219867984 ◽

2019 ◽

Vol 233 (19-20) ◽

pp. 6741-6753 ◽

Cited By ~ 11

Author(s):

Sudhir Kumar ◽

Rupinder Singh ◽

TP Singh ◽

Ajay Batish

Keyword(s):

Polylactic Acid ◽

Surface Properties ◽

Fused Deposition Modeling ◽

Mechanical Performance ◽

Three Dimensional ◽

Surface Hardness ◽

Functionally Graded ◽

Three Dimensional Printing ◽

Fused Deposition ◽

Dimensional Printing

In this work, an effort has been made for multimaterial three-dimensional printing of functionally graded prototypes of polylactic acid matrix (tensile specimens as per ASTM D638 type IV) followed by characterization of mechanical and surface properties. The work is an extension of previous reported studies on twin-screw extrusion process for the preparation of multimaterial wires as feedstock filaments in possible three-dimensional printing applications. The results of the study suggest that the highest peak strength (46.28 MPa) and break strength (41.65 MPa) was obtained for multimaterial three-dimensional printed samples at infill density 100%, infill angle 45°, and infill speed of 90 mm/s on commercial open source fused deposition modeling setup. Further surface hardness measurements performed on two extreme surfaces (top surface comprising magnetite (Fe3O4)-reinforced polylactic acid and bottom with polylactic acid without any reinforcement) revealed that the hardness for the bottom layer was more than the hardness for the top layer. From fractured surface analysis (using photomicrographs), it has been observed that the three-dimensional printed samples with low infill density resulted into more void formation due to which the performance while mechanical testing was poor in comparison to samples printed with higher infill density. The results are also supported by rendered images of photomicrographs, which revealed that high roughness value of samples printed with low infill density was also one of the reasons for poor mechanical performance of multimaterial three-dimensional printed functionally graded prototypes.

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Metallurgical Affects of Three Dimensional Printing Based Rapid Casting Solution

Materials Science Forum ◽

10.4028/www.scientific.net/msf.701.1 ◽

2011 ◽

Vol 701 ◽

pp. 1-8

Author(s):

Rupinder Singh

Keyword(s):

Heat Transfer ◽

Mechanical Properties ◽

Surface Finish ◽

Dimensional Stability ◽

Transfer Rate ◽

Three Dimensional ◽

Three Dimensional Printing ◽

Rapid Casting ◽

Black Art ◽

Dimensional Printing

Three dimensional printing (3DP) as rapid casting (RC) solutions has transformed over centuries from black art to science, but the metallurgical impinge on the process responsible for change in mechanical properties (like: surface finish, hardness, dimensional stability etc.) are still disputed. The purpose of the present research paper is to review metallurgical affect of 3DP based RC solution. The result of study suggests that prominent reason found to be responsible for improving the mechanical properties of RC is control of heat transfer rate while solidification (thus reducing dendrite formation).

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