Microstructural Characterization of 3D Printed Cementitious Materials

Three-dimensional concrete printing (3DCP) has progressed rapidly in recent years. With the aim to realize both buildings and civil works without using any molding, not only has the need for reliable mechanical properties of printed concrete grown, but also the need for more durable and environmentally friendly materials. As a consequence of super positioning cementitious layers, voids are created which can negatively affect durability. This paper presents the results of an experimental study on the relationship between 3DCP process parameters and the formed microstructure. The effect of two different process parameters (printing speed and inter-layer time) on the microstructure was established for fresh and hardened states, and the results were correlated with mechanical performance. In the case of a higher printing speed, a lower surface roughness was created due to the higher kinetic energy of the sand particles and the higher force applied. Microstructural investigations revealed that the amount of unhydrated cement particles was higher in the case of a lower inter-layer interval (i.e., 10 min). This phenomenon could be related to the higher water demand of the printed layer in order to rebuild the early Calcium-Silicate-Hydrate (CSH) bridges and the lower amount of water available for further hydration. The number of pores and the pore distribution were also more pronounced in the case of lower time intervals. Increasing the inter-layer time interval or the printing speed both lowered the mechanical performance of the printed specimens. This study emphasizes that individual process parameters will affect not only the structural behavior of the material, but they will also affect the durability and consequently the resistance against aggressive chemical substances.

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Investigations of process parameters during dissolution studies of drug loaded 3D printed tablets

Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine ◽

10.1177/0954411921993582 ◽

2021 ◽

pp. 095441192199358

Author(s):

Varun Sharma ◽

Khaja Moinuddin Shaik ◽

Archita Choudhury ◽

Pramod Kumar ◽

Prateek Kala ◽

...

Keyword(s):

Dissolution Rate ◽

Process Parameters ◽

Empirical Relation ◽

Three Dimensional ◽

Critical Parameters ◽

Fused Deposition Modelling ◽

Fused Deposition ◽

Rate Of Dissolution ◽

3D Printed ◽

Percentage Release

The present research paper attempts to study the effect of different process parameters on the dissolution rate during 3D printed tablets. Three-dimensional printing has the potential of serving tailored made tablets to cater personalized drug delivery systems. Fluorescein loaded PVA filaments through impregnation route was used to fabricate tablets based on Taguchi based design of experimentation using Fused Deposition Modelling (FDM). The effect of print speed, infill percentage and layer thickness were analyzed to study the effect on rate of dissolution. Infill percentage followed by print speed were found to be critical parameters affecting dissolution rate. The data analysis provided an insight into the study of interaction among different 3D printing parameters to develop an empirical relation for percentage release of the drug in human body.

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Mechanical Behavior of Printed Strain Hardening Cementitious Composites

Materials ◽

10.3390/ma13102253 ◽

2020 ◽

Vol 13 (10) ◽

pp. 2253

Author(s):

Stefan Chaves Figueiredo ◽

Claudia Romero Rodríguez ◽

Zeeshan Y. Ahmed ◽

Derk H. Bos ◽

Yading Xu ◽

...

Keyword(s):

Strain Hardening ◽

Mechanical Performance ◽

Three Dimensional ◽

Cementitious Materials ◽

Mechanical Tests ◽

Cementitious Composites ◽

Multiple Cracks ◽

Micro Computed Tomography ◽

Engineering Strain ◽

Strain Hardening Behavior

Extrusion based additive manufacturing of cementitious materials has demonstrated strong potential to become widely used in the construction industry. However, the use of this technique in practice is conditioned by a feasible solution to implement reinforcement in such automated process. One of the most successful ductile materials in civil engineering, strain hardening cementitious composites (SHCC) have a high potential to be employed for three-dimensional printing. The match between the tailored brittle matrix and ductility of the fibres enables these composites to develop multiple cracks when loaded under tension. Using previously developed mixtures, this study investigates the physical and mechanical performance of printed SHCC. The anisotropic behavior of the materials is explored by means of mechanical tests in several directions and micro computed tomography tests. The results demonstrated a composite showing strain hardening behavior in two directions explained by the fibre orientation found in the printed elements. Moreover, the printing technique used also has guaranteed an enhanced bond in between the printed layers.

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Effects of Layer-Interface Properties on Mechanical Performance of Concrete Elements Produced by Extrusion-Based 3D-Printing

10.20944/preprints201810.0067.v1 ◽

2018 ◽

Author(s):

Venkatesh Naidu Nerella ◽

Simone Hempel ◽

Viktor Mechtcherine

Keyword(s):

Flexural Strength ◽

Mechanical Performance ◽

Time Interval ◽

Self Healing ◽

Layer Interface ◽

Material Deposition ◽

Macro Scale ◽

3D Printed ◽

Pozzolanic Additives ◽

Concrete Elements

Interfaces between layers in 3D-printed elements produced by extrusion-based material deposition were investigated on both macro- and micro-scales. On the macro-scale, compression and bend tests were performed on two 3D-printable cement-based compositions (3PCs), namely C1 and C2. The influences of binder composition and time interval between layers on layer-interface strength were critically analyzed. In the context of additive manufacturing, the optimized composition C2, containing pozzolanic additives, exhibited mechanical performance superior to that of the mixture with Portland cement as the sole binder. In particular, Mixture C2 showed a less pronounced decrease in interface tensile strength. Even for time intervals between depositions of two layers as long as 1 day the loss in corresponding flexural strength was below 25%, as compared with C2 specimens tested in the perpendicular direction. In contrast, the decrease in flexural strength measured for C1 specimens amounted to over 90% for the same set of parameters. Higher porosity at the interfaces of the printed concrete layers was identified as the cause for the lower interface strengths of C1. Microscopic observations supported the findings of the macroscopic investigations. While a pronounced recovery (“self-healing”) of the porous, discontinuous interlayers was observed with increasing age for Mixture C2, in case of C1 the filling products grown in the porous interlayer were found to be non-strengthening.

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Silicate-Based Electro-Conductive Inks for Printing Soft Electronics and Tissue Engineering

Gels ◽

10.3390/gels7040240 ◽

2021 ◽

Vol 7 (4) ◽

pp. 240

Author(s):

Sadaf Samimi Gharaie ◽

Amir Seyfoori ◽

Bardia Khun Jush ◽

Xiong Zhou ◽

Erik Pagan ◽

...

Keyword(s):

Tissue Engineering ◽

Flexible Electronics ◽

Mechanical Performance ◽

Wearable Sensors ◽

Three Dimensional ◽

Tensile Tests ◽

Rheological Characterization ◽

Mechanical And Electrical Properties ◽

3D Printed ◽

Extrusion Printing

Hydrogel-based bio-inks have been extensively used for developing three-dimensional (3D) printed biomaterials for biomedical applications. However, poor mechanical performance and the inability to conduct electricity limit their application as wearable sensors. In this work, we formulate a novel, 3D printable electro-conductive hydrogel consisting of silicate nanosheets (Laponite), graphene oxide, and alginate. The result generated a stretchable, soft, but durable electro-conductive material suitable for utilization as a novel electro-conductive bio-ink for the extrusion printing of different biomedical platforms, including flexible electronics, tissue engineering, and drug delivery. A series of tensile tests were performed on the material, indicating excellent stability under significant stretching and bending without any conductive or mechanical failures. Rheological characterization revealed that the addition of Laponite enhanced the hydrogel’s mechanical properties, including stiffness, shear-thinning, and stretchability. We also illustrate the reproducibility and flexibility of our fabrication process by extrusion printing various patterns with different fiber diameters. Developing an electro-conductive bio-ink with favorable mechanical and electrical properties offers a new platform for advanced tissue engineering.

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Investigation of selected parameters effect on 3D printed sand mold properties through Taguchi method

Rapid Prototyping Journal ◽

10.1108/rpj-11-2019-0294 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Guili Gao ◽

Weikun Zhang ◽

Zhimin Du ◽

Qingyi Liu ◽

Yanqing Su ◽

...

Keyword(s):

Layer Thickness ◽

Process Parameters ◽

Bending Strength ◽

Three Dimensional ◽

Sand Mold ◽

Optimal Process ◽

Content Type ◽

Three Point Bending ◽

Boundary Properties ◽

3D Printed

Purpose The major concern technologies during the processing through three-dimensional printing (3DP) are the mechanical and boundary properties of sand models. The parameters such as activator content, resolution X, layer thickness and re-coater speed play a vital role in 3DP sand components. The purpose of this paper is to recommend the optimal process parameters for the best sand mold properties. Design/methodology/approach In this paper, taking the parameters of the activator content, resolution X, layer thickness and re-coater speed as the influence factors, an orthogonal test of L16(44) was designed to discuss the influences of those parameters on the mechanical and boundary properties. Three-point bending (3PB) test was used to characterize the actual bending strength, and the boundary accuracy was assessed by the deviation of the three-point bending samples compared with its design scale. Findings The experimental results showed that the resolution X and layer thickness are the main parameters affecting sand mold properties. The strength will attain its maximum when the resolution X and layer thickness are the minimum. The optimal parameters were screened and verified by the confirmation test. The optimal process parameters for best strength and less gas evolution are the activator of 0.19%, resolution X of 0.1 mm, layer thickness of 0.28 mm and re-coater speed of 210 mm/s. Originality/value The novelty of this paper is the select of significant parameters on 3D-printed sand model properties. A mathematical model was built to analyze the effect of these parameters. The optimal process parameters for the best properties were got.

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Optimization of FDM process parameters for tensile properties of polylactic acid specimens using Taguchi design of experiment method

Journal of Thermoplastic Composite Materials ◽

10.1177/0892705720964560 ◽

2020 ◽

pp. 089270572096456

Author(s):

M Heidari-Rarani ◽

N Ezati ◽

P Sadeghi ◽

MR Badrossamay

Keyword(s):

Mechanical Properties ◽

Tensile Properties ◽

Layer Thickness ◽

Polylactic Acid ◽

Process Parameters ◽

Design Of Experiment ◽

Taguchi Design Of Experiment ◽

Experiment Method ◽

3D Printed ◽

Printing Speed

Fused deposition modeling (FDM) is the most common method for additive manufacturing of polymers, which is expanding in various engineering applications due to its ability to make complex parts readily. The mechanical properties of 3D printed parts strongly depend on the correct selection of the process parameters. In this study, the effect of three important process parameters such as infill density, printing speed and layer thickness were investigated on the tensile properties of polylactic acid (PLA) specimens. Taguchi design of experiment method is applied to reduce the number of experiments and find the optimal parameters for maximum mechanical properties, minimum weight and minimum printing time. Experimental results showed that the optimum process parameters for the modulus of elasticity and ultimate tensile strength were infill density of 80%, printing speed of 40 mm/s and layer thickness of 0.1 mm, while for the failure strain were the infill density of 80%, printing speed of 40 mm/s and layer thickness of 0.2 mm. Finally, the accuracy of the Taguchi method was assessed for prediction of mechanical properties of FDM-3D printed specimens.

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Mechanical Properties of 3D-Printed Acrylonitrile–Butadiene–Styrene TiO2 and ATO Nanocomposites

Polymers ◽

10.3390/polym12071589 ◽

2020 ◽

Vol 12 (7) ◽

pp. 1589 ◽

Cited By ~ 2

Author(s):

Nectarios Vidakis ◽

Markos Petousis ◽

Athena Maniadi ◽

Emmanuel Koudoumas ◽

Marco Liebscher ◽

...

Keyword(s):

Mechanical Properties ◽

Mechanical Performance ◽

Sno2 Nanoparticles ◽

Three Dimensional ◽

Acrylonitrile Butadiene Styrene ◽

International Standards ◽

Fused Filament Fabrication ◽

Melt Mixing ◽

3D Printed ◽

Butadiene Styrene

In order to enhance the mechanical performance of three-dimensional (3D) printed structures fabricated via commercially available fused filament fabrication (FFF) 3D printers, novel nanocomposite filaments were produced herein following a melt mixing process, and further 3D printed and characterized. Titanium Dioxide (TiO2) and Antimony (Sb) doped Tin Oxide (SnO2) nanoparticles (NPs), hereafter denoted as ATO, were selected as fillers for a polymeric acrylonitrile butadiene styrene (ABS) thermoplastic matrix at various weight % (wt%) concentrations. Tensile and flexural test specimens were 3D printed, according to international standards. It was proven that TiO2 filler enhanced the overall tensile strength by 7%, the flexure strength by 12%, and the micro-hardness by 6%, while for the ATO filler, the corresponding values were 9%, 13%, and 6% respectively, compared to unfilled ABS. Atomic force microscopy (AFM) revealed the size of TiO2 (40 ± 10 nm) and ATO (52 ± 11 nm) NPs. Raman spectroscopy was performed for the TiO2 and ATO NPs as well as for the 3D printed nanocomposites to verify the polymer structure and the incorporated TiO2 and ATO nanocrystallites in the polymer matrix. The scope of this work was to fabricate novel nanocomposite filaments using commercially available materials with enhanced overall mechanical properties that industry can benefit from.

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Green Composites Based on PLA and Agricultural or Marine Waste Prepared by FDM

Polymers ◽

10.3390/polym13091361 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1361

Author(s):

Roberto Scaffaro ◽

Andrea Maio ◽

Emmanuel Fortunato Gulino ◽

Giuseppe Alaimo ◽

Marco Morreale

Keyword(s):

Mechanical Performance ◽

Low Cost ◽

Three Dimensional ◽

Posidonia Oceanica ◽

Positive Influence ◽

Green Composites ◽

3D Printed ◽

And Performance ◽

Marine Waste ◽

Natural Fillers

Three dimensional-printability of green composites is recently growing in importance and interest, especially in the view of feasibility to valorize agricultural and marine waste to attain green fillers capable of reducing bioplastic costs, without compromising their processability and performance from an environmental and mechanical standpoint. In this work, two lignocellulosic fillers, obtained from Opuntia ficus indica and Posidonia oceanica, were added to PLA and processed by FDM. Among the 3D printed biocomposites investigated, slight differences could be found in terms of PLA molecular weight and filler aspect ratio. It was shown that it is possible to replace up to 20% of bioplastic with low cost and ecofriendly natural fillers, without significantly modifying the processability and the mechanical performance of the neat matrix; at the same time, an increase of surface hydrophilicity was found, with possible positive influence on the biodegradability of such materials after disposal.

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Influences of Air-Voids on the Performance of 3D Printing Cementitious Materials

Materials ◽

10.3390/ma14164438 ◽

2021 ◽

Vol 14 (16) ◽

pp. 4438

Author(s):

Yujun Che ◽

Shengwen Tang ◽

Huashan Yang ◽

Weiwei Li ◽

Mengyuan Shi

Keyword(s):

3D Printing ◽

Mechanical Performance ◽

Cementitious Materials ◽

Strength Analysis ◽

Void Content ◽

Air Voids ◽

Void Structure ◽

3D Printed ◽

Air Void ◽

Air Void Content

This paper focuses on inspecting the influences of anti-foaming agent (AFA) on the performance of 3D printing cementitious materials (3DPC). The mini-slump, spreading diameter, yield stress, and strength of 3DPC were evaluated. Additionally, the air-void content, air-void morphology, and air-void size distribution of mortar with and without 0.05% AFA were assessed through image analysis. The mechanical performance and air-void structure of 3D printed samples were also investigated and compared to that of conventionally mould cast samples. Test results show that an optimal AFA content enables 3DPC to achieve favorable workability and mechanical performance. The addition of AFA exhibits lower air-void content in 3DPC than that of the sample without the AFA addition. This reduction in air-void content is further strengthened by the results of strength analysis. Electron microscope analysis shows that the use of AFA results in the suppressed formation of large air-voids during the process of fresh 3DPC. Moreover, the air-void morphology substantially influenced the mechanical performance of hardened 3DPC.

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Evaluation of Tensile Properties and Damage of Continuous Fibre Reinforced 3D-Printed Parts

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.774.161 ◽

2018 ◽

Vol 774 ◽

pp. 161-166 ◽

Cited By ~ 8

Author(s):

Octavio Andrés González-Estrada ◽

Alberto Pertuz ◽

Jabid E. Quiroga Mendez

Keyword(s):

3D Printing ◽

Tensile Properties ◽

Mechanical Performance ◽

Volume Fraction ◽

Three Dimensional ◽

Tensile Tests ◽

Fused Deposition Modelling ◽

Printing Process ◽

Fused Deposition ◽

3D Printed

Three-dimensional (3D) printing technology has been traditionally used for the production of prototypes. Recently, developments in 3D printing using Fused Deposition Modelling (FDM) and reinforcement with continuous fibres (fiberglass and carbon fibre), have allowed the manufacture of functional prototypes, considerably improving the mechanical performance of the composite parts. In this work, we characterise the elastic tensile properties of fibre reinforced specimens, considering the variation of several parameters available during the printing process: fibre orientation, volume fraction, fill pattern, reinforcement distribution. Tensile tests were performed according to ASTM D638 to obtain Young’s modulus and ultimate strength for different material configurations available during the printing process. We also perform a fractographic analysis using Scanning Electron Microscopy (SEM) to give an insight of the failure mechanisms present in the specimens.

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