Effects of Curing on Photosensitive Resins in SLA Additive Manufacturing

Different mechanical properties characterise the materials of 3D printed components, depending on the specific additive manufacturing (AM) process, its parameters, and the post-treatment adopted. Specifically, stereolithography (SLA) uses a photopolymerisation technique that creates solid components through selective solidification. In this study, 72 specimens were 3D printed using 12 commercial-grade methacrylate resins and tested under uniaxial tensile loads. The resin specimens were evaluated before and after curing. The recommended cure temperature and time were followed for all materials. The stress-strain curves measured during the testing campaign were evaluated in terms of maximum tensile strength, Young’s modulus, ductility, resilience, and toughness. The results reveal that the curing process increases the material stiffness and resistance to tensile loads. However, it was found that the curing process generally reduces the plasticity of the resins, causing a more or less marked brittle behaviour. This represents a potential limitation to the use of SLA 3D printing for structural elements which require some plasticity to avoid dangerous sudden failures.

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Effect of Porosity on Mechanical Properties of 3D Printed Polymers: Experiments and Micromechanical Modeling Based on X-Ray Computed Tomography Analysis

Polymers ◽

10.3390/polym11071154 ◽

2019 ◽

Vol 11 (7) ◽

pp. 1154 ◽

Cited By ~ 27

Author(s):

Wang ◽

Zhao ◽

Fuh ◽

Lee

Keyword(s):

Computed Tomography ◽

Mechanical Properties ◽

Additive Manufacturing ◽

Fused Deposition Modeling ◽

Micromechanical Model ◽

Micromechanical Modeling ◽

X Ray ◽

Fused Deposition ◽

3D Printed ◽

X Ray Computed

Additive manufacturing (commonly known as 3D printing) is defined as a family of technologies that deposit and consolidate materials to create a 3D object as opposed to subtractive manufacturing methodologies. Fused deposition modeling (FDM), one of the most popular additive manufacturing techniques, has demonstrated extensive applications in various industries such as medical prosthetics, automotive, and aeronautics. As a thermal process, FDM may introduce internal voids and pores into the fabricated thermoplastics, giving rise to potential reduction on the mechanical properties. This paper aims to investigate the effects of the microscopic pores on the mechanical properties of material fabricated by the FDM process via experiments and micromechanical modeling. More specifically, the three-dimensional microscopic details of the internal pores, such as size, shape, density, and spatial location were quantitatively characterized by X-ray computed tomography (XCT) and, subsequently, experiments were conducted to characterize the mechanical properties of the material. Based on the microscopic details of the pores characterized by XCT, a micromechanical model was proposed to predict the mechanical properties of the material as a function of the porosity (ratio of total volume of the pores over total volume of the material). The prediction results of the mechanical properties were found to be in agreement with the experimental data as well as the existing works. The proposed micromechanical model allows the future designers to predict the elastic properties of the 3D printed material based on the porosity from XCT results. This provides a possibility of saving the experimental cost on destructive testing.

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EFFECT OF EXTRUSION PROCESS PARAMETERS ON MECHANICAL PROPERTIES OF 3D PRINTED PLA PRODUCT

Journal of Mechanical Engineering and Mechatronics ◽

10.33021/jmem.v6i2.1573 ◽

2021 ◽

Vol 6 (2) ◽

pp. 119

Author(s):

Nanang Ali Sutisna ◽

Rakha Amrillah Fattah

Keyword(s):

Mechanical Properties ◽

Additive Manufacturing ◽

Fused Deposition Modeling ◽

Extrusion Process ◽

Experimental Procedure ◽

Fused Deposition ◽

Novel Approach ◽

Deposition Modeling ◽

3D Printed ◽

3D Digital Models

The method of producing items through synchronously depositing material level by level, based on 3D digital models, is named Additive Manufacturing (AM) or 3D-printing. Amongs many AM methods, the Fused Deposition Modeling (FDM) technique along with PLA (Polylactic acid) material is commonly used in additive manufacturing. Until now, the mechanical properties of the AM components could not be calculated or estimated until they've been assembled and checked. In this work, a novel approach is suggested as to how the extrusion process affects the mechanical properties of the printed component to obtain how the parts can be manufactured or printed to achieve improved mechanical properties. This methodology is based on an experimental procedure in which the combination of parameters to achieve an optimal from a manufacturing experiment and its value can be determined, the results obtained show the effect of the extrusion process affects the mechanical properties.

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Theoretical prediction of mechanical properties of 3D printed Kagome honeycombs and its experimental evaluation

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

10.1177/0954406219860538 ◽

2019 ◽

Vol 233 (18) ◽

pp. 6559-6576 ◽

Cited By ~ 2

Author(s):

Xuefeng Zhu ◽

Longkun Xu ◽

Xiaochen Liu ◽

Jinting Xu ◽

Ping Hu ◽

...

Keyword(s):

Mechanical Properties ◽

Shear Modulus ◽

Tensile Testing ◽

Elastic Moduli ◽

Uniaxial Tensile ◽

Anisotropy Ratio ◽

Young’S Moduli ◽

Analytical Formulas ◽

3D Printed ◽

Printed Materials

Kagome honeycomb structure is proved to incorporate excellent mechanical and actuation performances due to its special configuration. However, until now, the mechanical properties of 3D printed Kagome honeycomb have not been investigated. Hence, the objective of this work is to explore some mechanical properties of 3D-printed Kagome honeycomb structures such as elastic properties, buckling, and so on. In this paper, the analytical formulas of some mechanical properties of Kagome honeycombs made of 3D-printed materials are given. Effective elastic moduli such as Young's modulus, shear modulus, and Poisson's ratio of orthotropic Kagome honeycombs under in-plane compression and shear are derived in analytical forms. By these formulas, we investigate the relationship of the elastic moduli, the relative density, and the shape anisotropy–ratio of 3D-printed Kagome honeycomb. By the uniaxial tensile testing, the effective Young's moduli of 3D printed materials in the lateral and longitudinal directions are obtained. Then, by the analytical formulas and the experimental results, we can predict the maximum Young's moduli and the maximum shear modulus of 3D-printed Kagome honeycombs. The isotropic behavior of 3D-printed Kagome honeycombs is investigated. We also derived the equations of the initial yield strength surfaces and the buckling surfaces. We found that the sizes of the buckling surfaces of 3D printed material are smaller than that of isotropic material. The efficiency of the presented analytical formulas is verified through the tensile testing of 3D printed Kagome honeycomb specimens.

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DLP 3D Printing Meets Lignocellulosic Biopolymers: Carboxymethyl Cellulose Inks for 3D Biocompatible Hydrogels

Polymers ◽

10.3390/polym12081655 ◽

2020 ◽

Vol 12 (8) ◽

pp. 1655 ◽

Cited By ~ 4

Author(s):

Giuseppe Melilli ◽

Irene Carmagnola ◽

Chiara Tonda-Turo ◽

Fabrizio Pirri ◽

Gianluca Ciardelli ◽

...

Keyword(s):

Mechanical Properties ◽

Additive Manufacturing ◽

3D Printing ◽

Carboxymethyl Cellulose ◽

Biomedical Applications ◽

Digital Light Processing ◽

Chemically Modified ◽

Significant Step ◽

3D Printed ◽

Biomedical Field

The development of new bio-based inks is a stringent request for the expansion of additive manufacturing towards the development of 3D-printed biocompatible hydrogels. Herein, methacrylated carboxymethyl cellulose (M-CMC) is investigated as a bio-based photocurable ink for digital light processing (DLP) 3D printing. CMC is chemically modified using methacrylic anhydride. Successful methacrylation is confirmed by 1H NMR and FTIR spectroscopy. Aqueous formulations based on M-CMC/lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) photoinitiator and M-CMC/Dulbecco’s Modified Eagle Medium (DMEM)/LAP show high photoreactivity upon UV irradiation as confirmed by photorheology and FTIR. The same formulations can be easily 3D-printed through a DLP apparatus to produce 3D shaped hydrogels with excellent swelling ability and mechanical properties. Envisaging the application of the hydrogels in the biomedical field, cytotoxicity is also evaluated. The light-induced printing of cellulose-based hydrogels represents a significant step forward in the production of new DLP inks suitable for biomedical applications.

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Microstructure and Mechanical Properties of TiB2/ Al-Si Composites Fabricated by TIG Wire and Arc Additive Manufacturing

Materials Science Forum ◽

10.4028/www.scientific.net/msf.944.64 ◽

2019 ◽

Vol 944 ◽

pp. 64-72

Author(s):

Qing Feng Yang ◽

Cun Juan Xia ◽

Ya Qi Deng

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Tensile Strength ◽

Additive Manufacturing ◽

Yield Strength ◽

Filler Wire ◽

T6 Heat Treatment ◽

Microstructure And Mechanical Properties ◽

Before And After

Bulky sample was made by using TIG wire and arc additive manufacturing (WAAM) technology, in which Ф1.6 mm filler wire of in-situ TiB2/Al-Si composites was selected as deposition metal, following by T6 heat treatment. The microstructure and mechanical properties of the bulky sample before and after heat treatment were analyzed. Experimental results showed that the texture of the original samples parallel to the weld direction and perpendicular to the weld direction was similar consisting of columnar dendrites and equiaxed crystals. After T6 heat treatment, the hardness of the sample was increased to 115.85 HV from 62.83 HV, the yield strength of the sample was 273.33 MPa, the average tensile strength was 347.33 MPa, and the average elongation after fracture was 7.96%. Although pore defects existed in the fracture, yet the fracture of the sample was ductile fracture.

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Superior Mechanical Behavior and Fretting Wear Resistance of 3D-Printed Inconel 625 Superalloy

Applied Sciences ◽

10.3390/app8122439 ◽

2018 ◽

Vol 8 (12) ◽

pp. 2439 ◽

Cited By ~ 8

Author(s):

Yong Gao ◽

Mingzhuo Zhou

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Wear Resistance ◽

Additive Manufacturing ◽

High Hardness ◽

Fretting Wear ◽

Inconel 625 ◽

3D Printed ◽

Inconel 625 Superalloy ◽

Electron Beam Selective Melting

Additive manufacturing (AM) nickel-based superalloys have been demonstrated to equate or exceed mechanical properties of cast and wrought counterparts but their tribological potentials have not been fully realized. This study investigates fretting wear behaviors of Inconel 625 against the 42 CrMo4 stainless steel under flat-on-flat contacts. Inconel 625 is prepared by additive manufacturing (AM) using the electron beam selective melting. Results show that it has a high hardness (335 HV), superior tensile strength (952 MPa) and yield strength (793 MPa). Tribological tests indicate that the AM-Inconel 625 can suppress wear of the surface within a depth of only ~2.4 μm at a contact load of 106 N after 2 × 104 cycles. The excellent wear resistance is attributed to the improved strength and the formation of continuous tribo-layers containing a mixture of Fe2O3, Fe3O4, Cr2O3 and Mn2O3.

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Additive Manufacturing of Bone Scaffolds Using PolyJet and Stereolithography Techniques

Applied Sciences ◽

10.3390/app11167336 ◽

2021 ◽

Vol 11 (16) ◽

pp. 7336

Author(s):

Shummaila Rasheed ◽

Waqas Akbar Lughmani ◽

Muhannad Ahmed Obeidi ◽

Dermot Brabazon ◽

Inam Ul Ahad

Keyword(s):

Mechanical Properties ◽

Additive Manufacturing ◽

Dimensional Accuracy ◽

Human Bone ◽

Compression Tests ◽

3D Scaffold ◽

Bone Scaffolds ◽

3D Printed ◽

Printing Direction ◽

Printing Techniques

In this study, the printing capability of two different additive manufacturing (3D printing) techniques, namely PolyJet and micro-stereolithography (µSLA), are investigated regarding the fabrication of bone scaffolds. The 3D-printed scaffold structures are used as supports in replacing and repairing fractured bone tissue. Printed bone scaffolds with complex structures produced using additive manufacturing technology can mimic the mechanical properties of natural human bone, providing lightweight structures with modifiable porosity levels. In this study, 3D scaffold structures are designed with different combinations of architectural parameters. The dimensional accuracy, permeability, and mechanical properties of complex 3D-printed scaffold structures are analyzed to compare the advantages and drawbacks associated with the two techniques. The fluid flow rates through the 3D-printed scaffold structures are measured and Darcy’s law is applied to calculate the experimentally measured permeability. The Kozeny–Carman equation is applied for theoretical calculation of permeability. Compression tests were performed on the printed samples to observe the effects of the printing techniques on the mechanical properties of the 3D-printed scaffold structures. The effect of the printing direction on the mechanical properties of the 3D-printed scaffold structures is also analyzed. The scaffold structures printed with the µSLA printer demonstrate higher permeability and mechanical properties as compared to those printed using the PolyJet technique. It is demonstrated that both the µSLA and PolyJet printing techniques can be used to print 3D scaffold structures with controlled porosity levels, providing permeability in a similar range to human bone.

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Property Analysis of Photo-Polymerization-Type 3D-Printed Structures Based on Multi-Composite Materials

Applied Sciences ◽

10.3390/app11188545 ◽

2021 ◽

Vol 11 (18) ◽

pp. 8545

Author(s):

So-Ree Hwang ◽

Min-Soo Park

Keyword(s):

Mechanical Properties ◽

Additive Manufacturing ◽

Composite Materials ◽

3D Printing ◽

Bending Test ◽

3D Printer ◽

Complex Structures ◽

Photo Polymerization ◽

Anisotropic Structures ◽

3D Printed

Additive manufacturing, commonly called 3D printing, has been studied extensively because it can be used to fabricate complex structures; however, polymer-based 3D printing has limitations in terms of implementing certain functionalities, so it is limited in the production of conceptual prototypes. As such, polymer-based composites and multi-material 3D printing are being studied as alternatives. In this study, a DLP 3D printer capable of printing multiple composite materials was fabricated using a movable separator and structures with various properties were fabricated by selectively printing two composite materials. After the specimen was fabricated based on the ASTM, the basic mechanical properties of the structure were compared through a 3-point bending test and a ball rebound test. Through this, it was shown that structures with various mechanical properties can be fabricated using the proposed movable-separator-based DLP process. In addition, it was shown that this process can be used to fabricate anisotropic structures, whose properties vary depending on the direction of the force applied to the structure. By fabricating multi-joint grippers with varying levels of flexibility, it was shown that the proposed process can be applied in the fabrication of soft robots as well.

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Comparison between Tests and Simulations Regarding Bending Resistance of 3D Printed PLA Structures

Polymers ◽

10.3390/polym13244371 ◽

2021 ◽

Vol 13 (24) ◽

pp. 4371

Author(s):

Dorin-Ioan Catana ◽

Mihai-Alin Pop ◽

Denisa-Iulia Brus

Keyword(s):

Mechanical Properties ◽

Additive Manufacturing ◽

3D Printing ◽

Process Parameters ◽

Bending Stress ◽

Test Results ◽

Printing Process ◽

Simulation Process ◽

Bending Resistance ◽

3D Printed

Additive manufacturing is one of the technologies that is beginning to be used in new fields of parts production, but it is also a technology that is constantly evolving, due to the advances made by researchers and printing equipment. The paper presents how, by using the simulation process, the geometry of the 3D printed structures from PLA and PLA-Glass was optimized at the bending stress. The optimization aimed to reduce the consumption of filament (material) simultaneously with an increase in the bending resistance. In addition, this paper demonstrates that the simulation process can only be applied with good results to 3D printed structures when their mechanical properties are known. The inconsistency of printing process parameters makes the 3D printed structures not homogeneous and, consequently, the occurrence of errors between the test results and those of simulations become natural and acceptable. The mechanical properties depend on the values of the printing process parameters and the printing equipment because, in the case of 3D printing, it is necessary for each combination of parameters to determine their mechanical properties through specific tests.

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Graphite Modified Polylactide (PLA) for 3D Printed (FDM/FFF) Sliding Elements

Polymers ◽

10.3390/polym12061250 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1250 ◽

Cited By ~ 2

Author(s):

Robert E. Przekop ◽

Maciej Kujawa ◽

Wojciech Pawlak ◽

Marta Dobrosielska ◽

Bogna Sztorch ◽

...

Keyword(s):

Mechanical Properties ◽

Fracture Stress ◽

Low Cost ◽

Chemical Properties ◽

Spare Parts ◽

The Other ◽

Graphite Content ◽

Before And After ◽

3D Printed ◽

And Chemical Properties

With the development of 3D printing technology, there is a need to produce printable materials with improved properties, e.g., sliding properties. In this paper, the authors present the possibilities of producing composites based on biodegradable PLA with the addition of graphite. The team created composites with the following graphite weight contents: 1%, 2.5%, 5%, 7.5%, and 10%. Neat material was also subjected to testing. Tribological, mechanical, and chemical properties of the mentioned materials were examined. Measurements were also made after keeping the samples in ageing and climatic ovens. Furthermore, SEM observations of samples before and after friction tests were carried out. It was demonstrated that increasing graphite content caused a significant decrease in wear (PLA + 10% graphite had a wear rate three times lower than for a neat material). The addition of graphite did not adversely affect most of the other properties, but it ought to be noted that mechanical properties changed significantly. After conditioning in a climatic oven PLA + 10% graphite has (in comparison with neat material) 11% lower fracture stress, 47% lower impact strength, and 21% higher Young’s modulus. It can be certainly stated that the addition of graphite to PLA is a step towards obtaining a material that is low-cost and suitable for printing sliding spare parts.

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