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Dr. Markos Petousis
Hellenic Mediterranean University

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0 Additive Manufacturing
0 Biomechanics
0 Computer Numerical Control (CNC)
0 Nanocomposites
0 Reverse Engineering

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Additive Manufacturing
Nanocomposites
Biomechanics
Reverse Engineering

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Journal article
Published: 17 August 2021 in Polymers
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In this work, strain rate sensitivity was studied for 3D-printed polycarbonate (PC) and thermoplastic polyurethane (TPU) materials. Specimens were fabricated through fused filament fabrication (FFF) additive manufacturing (AM) technology and were tested at various strain rates. The effects of two FFF process parameters, i.e., nozzle temperature and layer thickness, were also investigated. A wide analysis for the tensile strength (MPa), the tensile modulus of elasticity (MPa), the toughness (MJ/m3) and the strain rate sensitivity index ‘m’ was conducted. Additionally, a morphological analysis was conducted using scanning electron microscopy (SEM) on the side and the fracture area of the specimens. Results from the different strain rates for each material were analyzed, in conjunction with the two FFF parameters tested, to determine their effect on the mechanical response of the two materials. PC and TPU materials exhibited similarities regarding their temperature response at different strain rates, while differences in layer height emerged regarding the appropriate choice for the FFF process. Overall, strain rate had a significant effect on the mechanical response of both materials.

ACS Style

Nectarios Vidakis; Markos Petousis; Apostolos Korlos; Emmanouil Velidakis; Nikolaos Mountakis; Chrisa Charou; Adrian Myftari. Strain Rate Sensitivity of Polycarbonate and Thermoplastic Polyurethane for Various 3D Printing Temperatures and Layer Heights. Polymers 2021, 13, 2752 .

AMA Style

Nectarios Vidakis, Markos Petousis, Apostolos Korlos, Emmanouil Velidakis, Nikolaos Mountakis, Chrisa Charou, Adrian Myftari. Strain Rate Sensitivity of Polycarbonate and Thermoplastic Polyurethane for Various 3D Printing Temperatures and Layer Heights. Polymers. 2021; 13 (16):2752.

Chicago/Turabian Style

Nectarios Vidakis; Markos Petousis; Apostolos Korlos; Emmanouil Velidakis; Nikolaos Mountakis; Chrisa Charou; Adrian Myftari. 2021. "Strain Rate Sensitivity of Polycarbonate and Thermoplastic Polyurethane for Various 3D Printing Temperatures and Layer Heights." Polymers 13, no. 16: 2752.

Journal article
Published: 17 July 2021 in C
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Conductive Polymer Composites (CPCs) have recently gained an extensive scientific interest as feedstock materials in Fused Filament Fabrication (FFF) Three-dimensional (3D) printing. Polylactic Acid (PLA), widely used in FFF 3D printing, as well as its Carbon Black (CB) nanocomposites at different weight percentage (wt.%) filler loadings (0.5, 1.0, 2.5 and 5.0 wt.%), were prepared via a melt mixing filament extrusion process in this study and utilized to manufacture FFF 3D printed specimens. The nanocomposites were examined for their electrical conductivity. The highest loaded 3D printed CPC (5.0 wt.%) was tested as an electrothermal Joule heating device. Static tensile, flexural, Charpy’s impact and Vickers microhardness mechanical properties were investigated for the neat and PLA/CB 3D printed nanocomposites. Dynamic Mechanical Analysis (DMA) revealed a stiffening mechanism for the PLA/CB nanocomposites. Scanning Electron Microscopy (SEM) elucidated the samples’ internal and external microstructural characteristics. The PLA/CB 5.0 wt.% nanocomposite demonstrated also antibacterial properties, when examined with a screening process, against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). It can be envisaged that the 3D printed PLA/CB CPCs exhibited a multi-functional performance, and could open new avenues towards low-cost personalized biomedical objects with complex geometry, amongst others, i.e., surgery tools, splints, wearables, etc.

ACS Style

Nectarios Vidakis; Markos Petousis; Emmanuel Velidakis; Nikolaos Mountakis; Peder Fischer-Griffiths; Sotirios Grammatikos; Lazaros Tzounis. Fused Filament Fabrication Three-Dimensional Printing Multi-Functional of Polylactic Acid/Carbon Black Nanocomposites. C 2021, 7, 52 .

AMA Style

Nectarios Vidakis, Markos Petousis, Emmanuel Velidakis, Nikolaos Mountakis, Peder Fischer-Griffiths, Sotirios Grammatikos, Lazaros Tzounis. Fused Filament Fabrication Three-Dimensional Printing Multi-Functional of Polylactic Acid/Carbon Black Nanocomposites. C. 2021; 7 (3):52.

Chicago/Turabian Style

Nectarios Vidakis; Markos Petousis; Emmanuel Velidakis; Nikolaos Mountakis; Peder Fischer-Griffiths; Sotirios Grammatikos; Lazaros Tzounis. 2021. "Fused Filament Fabrication Three-Dimensional Printing Multi-Functional of Polylactic Acid/Carbon Black Nanocomposites." C 7, no. 3: 52.

Journal article
Published: 21 June 2021 in Polymers
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Utilization of advanced engineering thermoplastic materials in fused filament fabrication (FFF) 3D printing process is critical in expanding additive manufacturing (AM) applications. Polypropylene (PP) is a widely used thermoplastic material, while silicon dioxide (SiO2) nanoparticles (NPs), which can be found in many living organisms, are commonly employed as fillers in polymers to improve their mechanical properties and processability. In this work, PP/SiO2 nanocomposite filaments at various concentrations were developed following a melt mixing extrusion process, and used for FFF 3D printing of specimens’ characterization according to international standards. Tensile, flexural, impact, microhardness, and dynamic mechanical analysis (DMA) tests were conducted to determine the effect of the nanofiller loading on the mechanical and viscoelastic properties of the polymer matrix. Scanning electron microscopy (SEM), Raman spectroscopy and atomic force microscopy (AFM) were performed for microstructural analysis, and finally melt flow index (MFI) tests were conducted to assess the melt rheological properties. An improvement in the mechanical performance was observed for silica loading up to 2.0 wt.%, while 4.0 wt.% was a potential threshold revealing processability challenges. Overall, PP/SiO2 nanocomposites could be ideal candidates for advanced 3D printing engineering applications towards structural plastic components with enhanced mechanical performance.

ACS Style

Nectarios Vidakis; Markos Petousis; Emmanouil Velidakis; Lazaros Tzounis; Nikolaos Mountakis; Apostolos Korlos; Peder Fischer-Griffiths; Sotirios Grammatikos. On the Mechanical Response of Silicon Dioxide Nanofiller Concentration on Fused Filament Fabrication 3D Printed Isotactic Polypropylene Nanocomposites. Polymers 2021, 13, 2029 .

AMA Style

Nectarios Vidakis, Markos Petousis, Emmanouil Velidakis, Lazaros Tzounis, Nikolaos Mountakis, Apostolos Korlos, Peder Fischer-Griffiths, Sotirios Grammatikos. On the Mechanical Response of Silicon Dioxide Nanofiller Concentration on Fused Filament Fabrication 3D Printed Isotactic Polypropylene Nanocomposites. Polymers. 2021; 13 (12):2029.

Chicago/Turabian Style

Nectarios Vidakis; Markos Petousis; Emmanouil Velidakis; Lazaros Tzounis; Nikolaos Mountakis; Apostolos Korlos; Peder Fischer-Griffiths; Sotirios Grammatikos. 2021. "On the Mechanical Response of Silicon Dioxide Nanofiller Concentration on Fused Filament Fabrication 3D Printed Isotactic Polypropylene Nanocomposites." Polymers 13, no. 12: 2029.

Journal article
Published: 04 June 2021 in Materials
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Polypropylene (PP) is an engineered thermoplastic polymer widely used in various applications. This work aims to enhance the properties of PP with the introduction of titanium dioxide (TiO2) nanoparticles (NPs) as nanofillers. Novel nanocomposite filaments were produced at 0.5, 1, 2, and 4 wt.% filler concentrations, following a melt mixing extrusion process. These filaments were then fed to a commercially available fused filament fabrication (FFF) 3D printer for the preparation of specimens, to be assessed for their mechanical, viscoelastic, physicochemical, and fractographic properties, according to international standards. Tensile, flexural, impact, and microhardness tests, as well as dynamic mechanical analysis (DMA), Raman, scanning electron microscopy (SEM), melt flow volume index (MVR), and atomic force microscopy (AFM), were conducted, to fully characterize the filler concentration effect on the 3D printed nanocomposite material properties. The results revealed an improvement in the nanocomposites properties, with the increase of the filler amount, while the microstructural effect and processability of the material was not significantly affected, which is important for the possible industrialization of the reported protocol. This work showed that PP/TiO2 can be a novel nanocomposite system in AM applications that the polymer industry can benefit from.

ACS Style

Nectarios Vidakis; Markos Petousis; Emmanouil Velidakis; Lazaros Tzounis; Nikolaos Mountakis; John Kechagias; Sotirios Grammatikos. Optimization of the Filler Concentration on Fused Filament Fabrication 3D Printed Polypropylene with Titanium Dioxide Nanocomposites. Materials 2021, 14, 3076 .

AMA Style

Nectarios Vidakis, Markos Petousis, Emmanouil Velidakis, Lazaros Tzounis, Nikolaos Mountakis, John Kechagias, Sotirios Grammatikos. Optimization of the Filler Concentration on Fused Filament Fabrication 3D Printed Polypropylene with Titanium Dioxide Nanocomposites. Materials. 2021; 14 (11):3076.

Chicago/Turabian Style

Nectarios Vidakis; Markos Petousis; Emmanouil Velidakis; Lazaros Tzounis; Nikolaos Mountakis; John Kechagias; Sotirios Grammatikos. 2021. "Optimization of the Filler Concentration on Fused Filament Fabrication 3D Printed Polypropylene with Titanium Dioxide Nanocomposites." Materials 14, no. 11: 3076.

Case report
Published: 18 May 2021 in Vision
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The purpose of this case report is to present a new surgical technique for the treatment of large Subretinal Hemorrhage (SRH) secondary to Age-related Macular Degeneration (AMD). Considering the biomechanics of foam evolution theory, bubble coarsening effect, and gas–liquid biphasic absorption, an SRH due to an AMD case was treated with vitrectomy. The treatment was implemented by subretinal injection of air bubbles combined with rtPA followed by air fluid exchange. The air bubbles helped mess up and remove the blood from the macula area, and no complications occurred. Two weeks postoperatively, there was no sign of hemorrhage and the Central Macular Thickness (CMT) was sharply decreased from 443 μm to 317 μm. At the five-month follow-up, the CMT remained at 267 μm and the patient’s visual acuity improved from light perception to 20/70 according to the Snellen chart. The combination of injecting multiple air bubbles and submacular rtPA, followed by air fluid exchange, was able to displace more than (90%) of the subretinal blood just two weeks postoperatively. Our technique is a promising alternative surgical approach for the displacement of SMH due to AMD, with a clear visual and anatomical benefit seen in the early follow-up period.

ACS Style

George Pappas; Nectarios Vidakis; Markos Petousis; Vasiliki Kounali; Apostolos Korlos. An Innovatory Surgical Technique for Submacular Hemorrhage Displacement by Means of a Bioengineering Perspective. Vision 2021, 5, 23 .

AMA Style

George Pappas, Nectarios Vidakis, Markos Petousis, Vasiliki Kounali, Apostolos Korlos. An Innovatory Surgical Technique for Submacular Hemorrhage Displacement by Means of a Bioengineering Perspective. Vision. 2021; 5 (2):23.

Chicago/Turabian Style

George Pappas; Nectarios Vidakis; Markos Petousis; Vasiliki Kounali; Apostolos Korlos. 2021. "An Innovatory Surgical Technique for Submacular Hemorrhage Displacement by Means of a Bioengineering Perspective." Vision 5, no. 2: 23.

Journal article
Published: 23 April 2021 in C
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In this study, nanocomposites with polyamide 12 (PA12) as the polymer matrix and multiwalled carbon nanotubes (MWCNTs) and carbon black (CB) at different loadings (2.5, 5.0, and 10.0 wt.%) as fillers, were produced in 3D printing filament form by melt mixing extrusion process. The filament was then used to build specimens with the fused filament fabrication (FFF) three-dimensional (3D) printing process. The aim was to produce by FFF 3D printing, electrically conductive and thermoelectric functional specimens with enhanced mechanical properties. All nanocomposites’ samples were electrically conductive at filler loadings above the electrical percolation threshold. The highest thermoelectric performance was obtained for the PA12/CNT nanocomposite at 10.0 wt.%. The static tensile and flexural mechanical properties, as well as the Charpy’s impact and Vickers microhardness, were determined. The highest improvement in mechanical properties was observed for the PA12/CNT nanocomposites at 5.0 wt.% filler loading. The fracture mechanisms were identified by fractographic analyses of scanning electron microscopy (SEM) images acquired from fractured surfaces of tensile tested specimens. The nanocomposites produced could find a variety of applications such as; 3D-printed organic thermoelectric materials for plausible large-scale thermal energy harvesting applications, resistors for flexible circuitry, and piezoresistive sensors for strain sensing.

ACS Style

Nectarios Vidakis; Markos Petousis; Lazaros Tzounis; Emmanuel Velidakis; Nikolaos Mountakis; Sotirios Grammatikos. Polyamide 12/Multiwalled Carbon Nanotube and Carbon Black Nanocomposites Manufactured by 3D Printing Fused Filament Fabrication: A Comparison of the Electrical, Thermoelectric, and Mechanical Properties. C 2021, 7, 38 .

AMA Style

Nectarios Vidakis, Markos Petousis, Lazaros Tzounis, Emmanuel Velidakis, Nikolaos Mountakis, Sotirios Grammatikos. Polyamide 12/Multiwalled Carbon Nanotube and Carbon Black Nanocomposites Manufactured by 3D Printing Fused Filament Fabrication: A Comparison of the Electrical, Thermoelectric, and Mechanical Properties. C. 2021; 7 (2):38.

Chicago/Turabian Style

Nectarios Vidakis; Markos Petousis; Lazaros Tzounis; Emmanuel Velidakis; Nikolaos Mountakis; Sotirios Grammatikos. 2021. "Polyamide 12/Multiwalled Carbon Nanotube and Carbon Black Nanocomposites Manufactured by 3D Printing Fused Filament Fabrication: A Comparison of the Electrical, Thermoelectric, and Mechanical Properties." C 7, no. 2: 38.

Journal article
Published: 15 April 2021 in Nanomaterials
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The scope of this work was to create, with melt mixing compounding process, novel nanocomposite filaments with enhanced properties that industry can benefit from, using commercially available materials, to enhance the performance of three-dimensional (3D) printed structures fabricated via fused filament fabrication (FFF) process. Silicon Dioxide (SiO2) nanoparticles (NPs) were selected as fillers for a polylactic acid (PLA) thermoplastic matrix at various weight % (wt.%) concentrations, namely, 0.5, 1.0, 2.0 and 4.0 wt.%. Tensile, flexural and impact test specimens were 3D printed and tested according to international standards and their Vickers microhardness was also examined. It was proven that SiO2 filler enhanced the overall strength at concentrations up to 1 wt.%, compared to pure PLA. Atomic force microscopy (AFM) was employed to investigate the produced nanocomposite extruded filaments roughness. Raman spectroscopy was performed for the 3D printed nanocomposites to verify the polymer nanocomposite structure, while thermogravimetric analysis (TGA) revealed the 3D printed samples’ thermal stability. Scanning electron microscopy (SEM) was carried out for the interlayer fusion and fractography morphological characterization of the specimens. Finally, the antibacterial properties of the produced nanocomposites were investigated with a screening process, to evaluate their performance against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus).

ACS Style

Nectarios Vidakis; Markos Petousis; Emanuel Velidakis; Nikolaos Mountakis; Lazaros Tzounis; Marco Liebscher; Sotirios Grammatikos. Enhanced Mechanical, Thermal and Antimicrobial Properties of Additively Manufactured Polylactic Acid with Optimized Nano Silica Content. Nanomaterials 2021, 11, 1012 .

AMA Style

Nectarios Vidakis, Markos Petousis, Emanuel Velidakis, Nikolaos Mountakis, Lazaros Tzounis, Marco Liebscher, Sotirios Grammatikos. Enhanced Mechanical, Thermal and Antimicrobial Properties of Additively Manufactured Polylactic Acid with Optimized Nano Silica Content. Nanomaterials. 2021; 11 (4):1012.

Chicago/Turabian Style

Nectarios Vidakis; Markos Petousis; Emanuel Velidakis; Nikolaos Mountakis; Lazaros Tzounis; Marco Liebscher; Sotirios Grammatikos. 2021. "Enhanced Mechanical, Thermal and Antimicrobial Properties of Additively Manufactured Polylactic Acid with Optimized Nano Silica Content." Nanomaterials 11, no. 4: 1012.

Research article
Published: 31 March 2021 in Materials and Manufacturing Processes
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In this work, two typical surface characteristics, i.e., mean surface roughness and angle of the kerf during laser processing of 3D-printed Polylactic Acid (PLA) plates with 4.00 mm in thickness, are investigated. A carbon dioxide laser was utilized to separate 27 work pieces of rectangular shape. The governing laser parameters, speed of cutting and laser power, were varied according to full factorial experimental methodology. An orthogonal array (OA) having nine combinations was implemented, and nine specimens were cut with the same set-up and the same parameters three times (27 replicates in total). The experimental results were analyzed using descriptive statistical analysis, i.e., histograms, box plots, interaction charts and optimized using analysis of means (ANOM) plots as well as ANOVA analysis. The data analysis indicated that laser speed is the dominant parameter for the kerf angle, whilst both the laser velocity and power are important for mean surface roughness of the cut surface for PLA 3D-printed parts. The spread of the data is smaller in Y direction, which indicates that the weaving phenomenon affects the laser cut performance.

ACS Style

J.D. Kechagias; K. Ninikas; M. Petousis; N. Vidakis; N. Vaxevanidis. An investigation of surface quality characteristics of 3D printed PLA plates cut by CO2 laser using experimental design. Materials and Manufacturing Processes 2021, 1 -10.

AMA Style

J.D. Kechagias, K. Ninikas, M. Petousis, N. Vidakis, N. Vaxevanidis. An investigation of surface quality characteristics of 3D printed PLA plates cut by CO2 laser using experimental design. Materials and Manufacturing Processes. 2021; ():1-10.

Chicago/Turabian Style

J.D. Kechagias; K. Ninikas; M. Petousis; N. Vidakis; N. Vaxevanidis. 2021. "An investigation of surface quality characteristics of 3D printed PLA plates cut by CO2 laser using experimental design." Materials and Manufacturing Processes , no. : 1-10.

Journal article
Published: 02 March 2021 in Materials
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The continuous demand for thermoplastic polymers in a great variety of applications, combined with an urgent need to minimize the quantity of waste for a balanced energy-from-waste strategy, has led to increasing scientific interest in developing new recycling processes for plastic products. Glycol-modified polyethylene terephthalate (PETG) is known to have some enhanced properties as compared to polyethylene terephthalate (PET) homopolymer; this has recently attracted the interest from the fused filament fabrication (FFF) three-dimensional (3D) printing community. PET has shown a reduced ability for repeated recycling through traditional processes. Herein, we demonstrate the potential for using recycled PETG in consecutive 3D printing manufacturing processes. Distributed recycling additive manufacturing (DRAM)-oriented equipment was chosen in order to test the mechanical and thermal response of PETG material in continuous recycling processes. Tensile, flexure, impact strength, and Vickers micro-hardness tests were carried out for six (6) cycles of recycling. Finally, Raman spectroscopy as well as thermal and morphological analyses via scanning electron microscopy (SEM) fractography were carried out. In general, the results revealed a minor knockdown effect on the mechanical properties as well as the thermal properties of PETG following the process proposed herein, even after six rounds of recycling.

ACS Style

Nectarios Vidakis; Markos Petousis; Lazaros Tzounis; Sotirios Grammatikos; Emmanouil Porfyrakis; Athena Maniadi; Nikolaos Mountakis. Sustainable Additive Manufacturing: Mechanical Response of Polyethylene Terephthalate Glycol over Multiple Recycling Processes. Materials 2021, 14, 1162 .

AMA Style

Nectarios Vidakis, Markos Petousis, Lazaros Tzounis, Sotirios Grammatikos, Emmanouil Porfyrakis, Athena Maniadi, Nikolaos Mountakis. Sustainable Additive Manufacturing: Mechanical Response of Polyethylene Terephthalate Glycol over Multiple Recycling Processes. Materials. 2021; 14 (5):1162.

Chicago/Turabian Style

Nectarios Vidakis; Markos Petousis; Lazaros Tzounis; Sotirios Grammatikos; Emmanouil Porfyrakis; Athena Maniadi; Nikolaos Mountakis. 2021. "Sustainable Additive Manufacturing: Mechanical Response of Polyethylene Terephthalate Glycol over Multiple Recycling Processes." Materials 14, no. 5: 1162.

Conference paper
Published: 06 February 2021 in Transactions on Petri Nets and Other Models of Concurrency XV
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The goal of this project is to remotely analyze the gait of people walking with crutches. To that objective, the use of video analysis based on the open-source software OpenPose is compared with the data collected from a sensor mounted on a human subject. The results show that the average value of acceleration between the video analysis and the sensor differs by 0.05%. All steps are clearly identified and synchronized. As a consequence, it is possible to validate non-contact acceleration data from video analysis with an inexpensive setup described in this paper. The results show a promise that this non-contact method can be used to assess the gait of disabled people with assistive devices in remote locations.

ACS Style

Achilles Vairis; Johnathan Boyak; Suzana Brown; Maurice Bess; Kyu Hyun Bae; Markos Petousis. Gait Analysis Using Video for Disabled People in Marginalized Communities. Transactions on Petri Nets and Other Models of Concurrency XV 2021, 145 -153.

AMA Style

Achilles Vairis, Johnathan Boyak, Suzana Brown, Maurice Bess, Kyu Hyun Bae, Markos Petousis. Gait Analysis Using Video for Disabled People in Marginalized Communities. Transactions on Petri Nets and Other Models of Concurrency XV. 2021; ():145-153.

Chicago/Turabian Style

Achilles Vairis; Johnathan Boyak; Suzana Brown; Maurice Bess; Kyu Hyun Bae; Markos Petousis. 2021. "Gait Analysis Using Video for Disabled People in Marginalized Communities." Transactions on Petri Nets and Other Models of Concurrency XV , no. : 145-153.

Journal article
Published: 19 January 2021 in Materials
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Plastic waste reduction and recycling through circular use has been critical nowadays, since there is an increasing demand for the production of plastic components based on different polymeric matrices in various applications. The most commonly used recycling procedure, especially for thermoplastic materials, is based on thermomechanical process protocols that could significantly alter the polymers’ macromolecular structure and physicochemical properties. The study at hand focuses on recycling of polyamide 12 (PA12) filament, through extrusion melting over multiple recycling courses, giving insight for its effect on the mechanical and thermal properties of Fused Filament Fabrication (FFF) manufactured specimens throughout the recycling courses. Three-dimensional (3D) FFF printed specimens were produced from virgin as well as recycled PA12 filament, while they have been experimentally tested further for their tensile, flexural, impact and micro-hardness mechanical properties. A thorough thermal and morphological analysis was also performed on all the 3D printed samples. The results of this study demonstrate that PA12 can be successfully recycled for a certain number of courses and could be utilized in 3D printing, while exhibiting improved mechanical properties when compared to virgin material for a certain number of recycling repetitions. From this work, it can be deduced that PA12 can be a viable option for circular use and 3D printing, offering an overall positive impact on recycling, while realizing 3D printed components using recycled filaments with enhanced mechanical and thermal stability.

ACS Style

Nectarios Vidakis; Markos Petousis; Lazaros Tzounis; Athena Maniadi; Emmanouil Velidakis; Nikolaos Mountakis; John D. Kechagias. Sustainable Additive Manufacturing: Mechanical Response of Polyamide 12 over Multiple Recycling Processes. Materials 2021, 14, 466 .

AMA Style

Nectarios Vidakis, Markos Petousis, Lazaros Tzounis, Athena Maniadi, Emmanouil Velidakis, Nikolaos Mountakis, John D. Kechagias. Sustainable Additive Manufacturing: Mechanical Response of Polyamide 12 over Multiple Recycling Processes. Materials. 2021; 14 (2):466.

Chicago/Turabian Style

Nectarios Vidakis; Markos Petousis; Lazaros Tzounis; Athena Maniadi; Emmanouil Velidakis; Nikolaos Mountakis; John D. Kechagias. 2021. "Sustainable Additive Manufacturing: Mechanical Response of Polyamide 12 over Multiple Recycling Processes." Materials 14, no. 2: 466.

Journal article
Published: 04 January 2021 in Recycling
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Polymer recycling is nowadays in high-demand due to an increase in polymers demand and production. Recycling of such materials is mostly a thermomechanical process that modifies their overall mechanical behavior. The present research work focuses on the recyclability of high-density polyethylene (HDPE), one of the most recycled materials globally, for use in additive manufacturing (AM). A thorough investigation was carried out to determine the effect of the continuous recycling on mechanical, structural, and thermal responses of HDPE polymer via a process that isolates the thermomechanical treatment from other parameters such as aging, contamination, etc. Fused filament fabrication (FFF) specimens were produced from virgin and recycled materials and were experimentally tested and evaluated in tension, flexion, impact, and micro-hardness. A thorough thermal and morphological analysis was also performed. The overall results of this study show that the mechanical properties of the recycled HDPE polymer were generally improved over the recycling repetitions for a certain number of recycling steps, making the HDPE recycling a viable option for circular use. Repetitions two to five had the optimum overall mechanical behavior, indicating a significant positive impact of the HDPE polymer recycling aside from the environmental one.

ACS Style

Nectarios Vidakis; Markos Petousis; Athena Maniadi. Sustainable Additive Manufacturing: Mechanical Response of High-Density Polyethylene over Multiple Recycling Processes. Recycling 2021, 6, 4 .

AMA Style

Nectarios Vidakis, Markos Petousis, Athena Maniadi. Sustainable Additive Manufacturing: Mechanical Response of High-Density Polyethylene over Multiple Recycling Processes. Recycling. 2021; 6 (1):4.

Chicago/Turabian Style

Nectarios Vidakis; Markos Petousis; Athena Maniadi. 2021. "Sustainable Additive Manufacturing: Mechanical Response of High-Density Polyethylene over Multiple Recycling Processes." Recycling 6, no. 1: 4.

Journal article
Published: 29 December 2020 in Metals
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The aim of this work was to weld thin sheets (2 mm) of Al 7075 in a butt joint configuration using friction stir welding and to identify the appropriate tool geometry and optimum process parameters. Two tools were produced with heat treatable low alloy steel WNr 1.6582/DIN 34CrNiMo6 with a different pin diameter (3 mm and 4 mm). Welding was performed at a range of rotation speeds 1000–2500 rpm and various welding speeds 80–800 mm/min. The tensile strength was measured to evaluate mechanical properties. Results showed that despite the difficulties in friction stir welding thin plates, sound joints can be produced in a repeatable manner, without visible wear on the welding tool. The mechanical strength of the welds showed a decrease (33.75%) over that of the parent material. The mechanical strength was less affected by rotation speed than welding speed and there was a significant decrease in tensile strength compared to the parent material.

ACS Style

Andreas Dimopoulos; Achilles Vairis; Nectarios Vidakis; Markos Petousis. On the Friction Stir Welding of Al 7075 Thin Sheets. Metals 2020, 11, 57 .

AMA Style

Andreas Dimopoulos, Achilles Vairis, Nectarios Vidakis, Markos Petousis. On the Friction Stir Welding of Al 7075 Thin Sheets. Metals. 2020; 11 (1):57.

Chicago/Turabian Style

Andreas Dimopoulos; Achilles Vairis; Nectarios Vidakis; Markos Petousis. 2020. "On the Friction Stir Welding of Al 7075 Thin Sheets." Metals 11, no. 1: 57.

Journal article
Published: 25 December 2020 in Sustainability
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The recycling of polymeric materials has received a steadily growing scientific and industrial interest due to the increase in demand and production of durable and lightweight plastic parts. Recycling of such materials is mostly based on thermomechanical processes that significantly affect the mechanical, as well as the overall physicochemical properties of polymers. The study at hand focuses on the recyclability of Fused Filament Fabrication (FFF) 3D printed Polypropylene (PP) for a certain number of recycling courses (six in total), and its effect on the mechanical properties of 3D printed parts. Namely, 3D printed specimens were fabricated from non-recycled and recycled PP material, and further experimentally tested regarding their mechanical properties in tension, flexion, impact, and microhardness. Comprehensive dynamic scanning calorimetry (DSC), thermogravimetric analysis (TGA), Raman spectroscopy, and morphological investigations by scanning electron microscopy (SEM) were performed for the different 3D printed PP samples. The overall results showed that there is an overall slight increase in the material’s mechanical properties, both in tension and in flexion mode, while the DSC characterization indicates an increase in the polymer crystallinity over the recycling course.

ACS Style

Nectarios Vidakis; Markos Petousis; Lazaros Tzounis; Athena Maniadi; Emmanouil Velidakis; Nicolaos Mountakis; Dimitrios Papageorgiou; Marco Liebscher; Viktor Mechtcherine. Sustainable Additive Manufacturing: Mechanical Response of Polypropylene over Multiple Recycling Processes. Sustainability 2020, 13, 159 .

AMA Style

Nectarios Vidakis, Markos Petousis, Lazaros Tzounis, Athena Maniadi, Emmanouil Velidakis, Nicolaos Mountakis, Dimitrios Papageorgiou, Marco Liebscher, Viktor Mechtcherine. Sustainable Additive Manufacturing: Mechanical Response of Polypropylene over Multiple Recycling Processes. Sustainability. 2020; 13 (1):159.

Chicago/Turabian Style

Nectarios Vidakis; Markos Petousis; Lazaros Tzounis; Athena Maniadi; Emmanouil Velidakis; Nicolaos Mountakis; Dimitrios Papageorgiou; Marco Liebscher; Viktor Mechtcherine. 2020. "Sustainable Additive Manufacturing: Mechanical Response of Polypropylene over Multiple Recycling Processes." Sustainability 13, no. 1: 159.

Journal article
Published: 13 December 2020 in Nanomaterials
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We report on a versatile method for chemically grafting multiwalled carbon nanotubes (MWCNTs) onto the surface of conventional glass fibers (GFs), as well as depositing further silica (SiO2) or superparamagnetic (SPM) magnetite (Fe3O4) nanoparticles (NPs) creating novel hierarchical reinforcements. The CNT-grafted GFs (GF-CNT) were utilized further as the support to decorate nano-sized SiO2 or Fe3O4 via electrostatic interactions, resulting finally into double hierarchy reinforcements. SiO2 NPs were first used as model nano-particulate objects to investigate the interfacial adhesion properties of binary coated GFs (denoted as GF-CNT/SiO2) in epoxy matrix via single fiber pull-out (SFPO) tests. The results indicated that the apparent interfacial shear strength (IFSS or τapp) was significantly increased compared to the GF-CNT. Fe3O4 NPs were assembled also onto CNT-grafted GFs resulting into GF-CNT/Fe3O4. The fibers exhibited a magnetic response upon being exposed to an external magnet. Scanning electron microscopy (SEM) revealed the surface morphologies of the different hierarchical fibers fabricated in this work. The interphase microstructure of GF-CNT and GF-CNT/SiO2 embedded in epoxy was investigated by transmission electron microscopy (TEM). The hybrid and hierarchical GFs are promising multifunctional reinforcements with appr. 85% increase of the IFSS as compared to typical amino-silane modified GFs. It could be envisaged that, among other purposes, GF-CNT/Fe3O4 could be potentially recyclable reinforcements, especially when embedded in thermoplastic polymer matrices.

ACS Style

Markos Petousis; Lazaros Tzounis; Dimitrios Papageorgiou; Nectarios Vidakis. Decoration of SiO2 and Fe3O4 Nanoparticles onto the Surface of MWCNT-Grafted Glass Fibers: A Simple Approach for the Creation of Binary Nanoparticle Hierarchical and Multifunctional Composite Interphases. Nanomaterials 2020, 10, 2500 .

AMA Style

Markos Petousis, Lazaros Tzounis, Dimitrios Papageorgiou, Nectarios Vidakis. Decoration of SiO2 and Fe3O4 Nanoparticles onto the Surface of MWCNT-Grafted Glass Fibers: A Simple Approach for the Creation of Binary Nanoparticle Hierarchical and Multifunctional Composite Interphases. Nanomaterials. 2020; 10 (12):2500.

Chicago/Turabian Style

Markos Petousis; Lazaros Tzounis; Dimitrios Papageorgiou; Nectarios Vidakis. 2020. "Decoration of SiO2 and Fe3O4 Nanoparticles onto the Surface of MWCNT-Grafted Glass Fibers: A Simple Approach for the Creation of Binary Nanoparticle Hierarchical and Multifunctional Composite Interphases." Nanomaterials 10, no. 12: 2500.

Journal article
Published: 06 December 2020 in Polymers
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In this study, the strain rate sensitivity of five different thermoplastic polymers processed via Fused Filament Fabrication (FFF) Additive Manufacturing (AM) is reported. Namely, Polylactic Acid (PLA), Acrylonitrile-Butadiene-Styrene (ABS), Polyethylene Terephthalate Glycol (PETG), Polyamide 6 (PA6), and Polypropylene (PP) were thoroughly investigated under static tensile loading conditions at different strain rates. Strain rates have been selected representing the most common applications of polymeric materials manufactured by Three-Dimensional (3D) Printing. Each polymer was exposed to five different strain rates in order to elucidate the dependency and sensitivity of the tensile properties, i.e., stiffness, strength, and toughness on the applied strain rate. Scanning Electron Microscopy (SEM) was employed to investigate the 3D printed samples’ fractured surfaces, as a means to derive important information regarding the fracture process, the type of fracture (brittle or ductile), as well as correlate the fractured surface characteristics with the mechanical response under certain strain rate conditions. An Expectation–Maximization (EM) analysis was carried out. Finally, a comparison is presented calculating the strain rate sensitivity index “m” and toughness of all materials at the different applied strain rates.

ACS Style

Nectarios Vidakis; Markos Petousis; Emmanouil Velidakis; Marco Liebscher; Viktor Mechtcherine; Lazaros Tzounis. On the Strain Rate Sensitivity of Fused Filament Fabrication (FFF) Processed PLA, ABS, PETG, PA6, and PP Thermoplastic Polymers. Polymers 2020, 12, 2924 .

AMA Style

Nectarios Vidakis, Markos Petousis, Emmanouil Velidakis, Marco Liebscher, Viktor Mechtcherine, Lazaros Tzounis. On the Strain Rate Sensitivity of Fused Filament Fabrication (FFF) Processed PLA, ABS, PETG, PA6, and PP Thermoplastic Polymers. Polymers. 2020; 12 (12):2924.

Chicago/Turabian Style

Nectarios Vidakis; Markos Petousis; Emmanouil Velidakis; Marco Liebscher; Viktor Mechtcherine; Lazaros Tzounis. 2020. "On the Strain Rate Sensitivity of Fused Filament Fabrication (FFF) Processed PLA, ABS, PETG, PA6, and PP Thermoplastic Polymers." Polymers 12, no. 12: 2924.

Journal article
Published: 22 October 2020 in Biomimetics
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Myopic macular foveoschisis maculopathy is an eye disease that is treated, in most cases, with surgical intervention, in which a macular buckle is applied to restore eye anatomy and functionality. A macular buckle is a type of exoplant that comes in various designs and sizes. Often, they are difficult to apply or they do not fit properly in the eye geometry since they have a generic form. In this work, the effort to develop the most suitable tailor-made macular buckle for each individual patient for treating myopic traction maculopathy is studied. Pattern recognition techniques are applied to the patient’s Computed Tomography (CT) data to develop the exact 3D geometry of the eye. Using this 3D geometry, the trajectory of the buckle is fitted and the buckle is formed, which is then 3D-printed with biocompatible polymer materials. It is expected that the power of technology will be used to activate the most precise approach for each individual patient. Considering the possible complications and technical difficulties of other surgical methods, the customized macular buckle is an appropriate, easy-to-use, and most precise piece of medical equipment for the treatment of myopic traction maculopathy.

ACS Style

George Pappas; Nectarios Vidakis; Markos Petousis; Athena Maniadi. Individualized Ophthalmic Exoplants by Means of Reverse Engineering and 3D Printing Technologies for Treating High Myopia Complications with Macular Buckles. Biomimetics 2020, 5, 54 .

AMA Style

George Pappas, Nectarios Vidakis, Markos Petousis, Athena Maniadi. Individualized Ophthalmic Exoplants by Means of Reverse Engineering and 3D Printing Technologies for Treating High Myopia Complications with Macular Buckles. Biomimetics. 2020; 5 (4):54.

Chicago/Turabian Style

George Pappas; Nectarios Vidakis; Markos Petousis; Athena Maniadi. 2020. "Individualized Ophthalmic Exoplants by Means of Reverse Engineering and 3D Printing Technologies for Treating High Myopia Complications with Macular Buckles." Biomimetics 5, no. 4: 54.

Journal article
Published: 13 October 2020 in Mathematics
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An experimental investigation of the surface quality of the Poly-Jet 3D printing (PJ-3DP) process is presented. PJ-3DP is an additive manufacturing process, which uses jetted photopolymer droplets, which are immediately cured with ultraviolet lamps, to build physical models, layer-by-layer. This method is fast and accurate due to the mechanism it uses for the deposition of layers as well as the 16 microns of layer thickness used. Τo characterize the surface quality of PJ-3DP printed parts, an experiment was designed and the results were analyzed to identify the impact of the deposition angle and blade mechanism motion onto the surface roughness. First, linear regression models were extracted for the prediction of surface quality parameters, such as the average surface roughness (Ra) and the total height of the profile (Rt) in the X and Y directions. Then, a Feed Forward Back Propagation Neural Network (FFBP-NN) was proposed for increasing the prediction performance of the surface roughness parameters Ra and Rt. These two models were compared with the reported ones in the literature; it was revealed that both performed better, leading to more accurate surface roughness predictions, whilst the NN model resulted in the best predictions, in particular for the Ra parameter.

ACS Style

Nectarios Vidakis; Markos Petousis; Nikolaos Vaxevanidis; John Kechagias. Surface Roughness Investigation of Poly-Jet 3D Printing. Mathematics 2020, 8, 1758 .

AMA Style

Nectarios Vidakis, Markos Petousis, Nikolaos Vaxevanidis, John Kechagias. Surface Roughness Investigation of Poly-Jet 3D Printing. Mathematics. 2020; 8 (10):1758.

Chicago/Turabian Style

Nectarios Vidakis; Markos Petousis; Nikolaos Vaxevanidis; John Kechagias. 2020. "Surface Roughness Investigation of Poly-Jet 3D Printing." Mathematics 8, no. 10: 1758.

Journal article
Published: 02 September 2020 in Biomimetics
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In this study, an industrially scalable method is reported for the fabrication of polylactic acid (PLA)/silver nanoparticle (AgNP) nanocomposite filaments by an in-situ reduction reactive melt mixing method. The PLA/AgNP nanocomposite filaments have been produced initially reducing silver ions (Ag+) arising from silver nitrate (AgNO3) precursor mixed in the polymer melt to elemental silver (Ag0) nanoparticles, utilizing polyethylene glycol (PEG) or polyvinyl pyrrolidone (PVP), respectively, as macromolecular blend compound reducing agents. PEG and PVP were added at various concentrations, to the PLA matrix. The PLA/AgNP filaments have been used to manufacture 3D printed antimicrobial (AM) parts by Fused Filament Fabrication (FFF). The 3D printed PLA/AgNP parts exhibited significant AM properties examined by the reduction in Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) bacteria viability (%) experiments at 30, 60, and 120 min duration of contact (p < 0.05; p-value (p): probability). It could be envisaged that the 3D printed parts manufactured and tested herein mimic nature’s mechanism against bacteria and in terms of antimicrobial properties, contact angle for their anti-adhesive behavior and mechanical properties could create new avenues for the next generation of low-cost and on-demand additive manufacturing produced personal protective equipment (PPE) as well as healthcare and nosocomial antimicrobial equipment.

ACS Style

Nectarios Vidakis; Markos Petousis; Emmanouel Velidakis; Marco Liebscher; Lazaros Tzounis. Three-Dimensional Printed Antimicrobial Objects of Polylactic Acid (PLA)-Silver Nanoparticle Nanocomposite Filaments Produced by an In-Situ Reduction Reactive Melt Mixing Process. Biomimetics 2020, 5, 42 .

AMA Style

Nectarios Vidakis, Markos Petousis, Emmanouel Velidakis, Marco Liebscher, Lazaros Tzounis. Three-Dimensional Printed Antimicrobial Objects of Polylactic Acid (PLA)-Silver Nanoparticle Nanocomposite Filaments Produced by an In-Situ Reduction Reactive Melt Mixing Process. Biomimetics. 2020; 5 (3):42.

Chicago/Turabian Style

Nectarios Vidakis; Markos Petousis; Emmanouel Velidakis; Marco Liebscher; Lazaros Tzounis. 2020. "Three-Dimensional Printed Antimicrobial Objects of Polylactic Acid (PLA)-Silver Nanoparticle Nanocomposite Filaments Produced by an In-Situ Reduction Reactive Melt Mixing Process." Biomimetics 5, no. 3: 42.

Journal article
Published: 17 July 2020 in Polymers
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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.

ACS Style

Nectarios Vidakis; Markos Petousis; Athena Maniadi; Emmanuel Koudoumas; Marco Liebscher; Lazaros Tzounis. Mechanical Properties of 3D-Printed Acrylonitrile–Butadiene–Styrene TiO2 and ATO Nanocomposites. Polymers 2020, 12, 1589 .

AMA Style

Nectarios Vidakis, Markos Petousis, Athena Maniadi, Emmanuel Koudoumas, Marco Liebscher, Lazaros Tzounis. Mechanical Properties of 3D-Printed Acrylonitrile–Butadiene–Styrene TiO2 and ATO Nanocomposites. Polymers. 2020; 12 (7):1589.

Chicago/Turabian Style

Nectarios Vidakis; Markos Petousis; Athena Maniadi; Emmanuel Koudoumas; Marco Liebscher; Lazaros Tzounis. 2020. "Mechanical Properties of 3D-Printed Acrylonitrile–Butadiene–Styrene TiO2 and ATO Nanocomposites." Polymers 12, no. 7: 1589.