3D-printed Samples Research Articles

Radiographic testing of 3D-printed thermoplastics using Am-241 as a gamma-ray source

The industrial production of 3D printing is known as additive manufacturing (AM), in which a computer controls the process of producing 3D objects. Although x-ray computed radiography (XCT) is extensively used in the quality control and testing of additive manufacturing products, the gamma-ray radiography capabilities for these applications still need to be investigated. This study aimed to evaluate the performance of gamma-ray radiography using americium-241 (Am-241) as the gamma source. Here, we inspected fused deposition three-dimensional (3D) modeling products produced from polylactic acid (PLA) as thermoplastic samples. Radiographic testing of 3D-printed thermoplastic samples was performed using Monte Carlo simulations and validated by experimental studies. We used Am-241 (gamma-ray source) to conduct simulations and experiments investigations; two simulations were used: one by using 59.6 keV energy of gamma-ray and the other using all gamma-ray energies, including 16.96 keV, 26.3446 keV% 2.31 up to 662.40 keV. Also, we performed the x-ray radiography test to be used as a standard. The results showed that the defect detectability in the 3D-printed PLA samples using Am-241 as a gamma-ray source is comparable to that of x-ray results. This study concluded that the Am-241 could be used as the gamma-ray source to perform the radiography test for the products produced by 3D-printed thermoplastics.

Digital Light Processing-3D Printing of Thermoset Materials with High Biodegradability from Amino Acid-Derived Acrylamide Monomers.

Six acrylamide resins, derived from l-phenylalanine and l-leucine, are designed for application in digital light processing (DLP) printers to obtain biodegradable thermoset polymers. The acrylamide copolymers are prepared under light irradiation at 405nm and thermal post-curing processes. Low molecular weight poly(ethylene glycol)diacrylate (PEGDA) and N,N-dimethylacrylamide (DMAM), both liquid resins, are used as co-monomers and diluents for the amino acid-derived acrylamide solubilization. The presence of two phenylalanine units and two ester groups in the acrylamide monomer accuses a fast degradation rate in hydrolytic medium in 90 days. The residual products leached in the aqueous media prove to be non-cytotoxic, when 3D-printed samples are cultured with osteoblast cells (MG63), which represents an advantage for the safe disposal of printer waste materials. The scaled-up pieces derived from l-phenylalanine and diethylene glycol, as amino acid-derived acrylamide (named compound C), PEGDA and DMAM, present high dimensional stability after DLP printing of complex structures used as testing samples. Layers of 50µm of thickness are well cohesive having isotropic behavior, as demonstrated with tensile-strain measurements performed in X-Y-Z (plane) directions. The compound C, which contains phenylalanine amino acid, reveals a promising potential to replace non-biodegradable acrylate polymers used in prototyping systems.

Tunable topological edge modes in Su–Schrieffer–Heeger arrays

A potential weakness of topological waveguides is that they act on a fixed narrow band of frequencies. However, by 3D printing samples from a photo-responsive polymer, we can obtain a device whose operating frequency can be fine-tuned dynamically using laser excitation. This greatly enhances existing static tunability strategies, typically based on modifying the geometry. We use a version of the classical Su–Schrieffer–Heeger model to demonstrate our approach.

Mechanical Performance of 3D-Printed Cornstarch–Sandstone Sustainable Material

The objective of this research is the improvement of the physical properties of artificial sandstone in order to obtain a printable construction material whose composition and structure is suitable for the design, study and construction of environmentally friendly architectural structures. To investigate the suitability of the researched material for 3D printing and determine the physical and mechanical properties of the starch-based sandstone 3D-printed material, both cylindrical and cellular samples were designed. The 3D-printed artificial starch–sandstone material was found to have satisfactory mechanical properties.

An experimental investigation of screw-based material extrusion 3D printing of metallic parts

With the introduction of additive manufacturing (AM) methods, processes with the capability of 3D printing of metal materials were noticed. In general, AM processes with the ability to 3D print metals are more complex and costly in terms of equipment than processes that 3D print other materials (polymers and ceramics). Therefore, the use of 3D printing devices with less complexity and cost, such as extrusion-based 3D printers, for metal printing has attracted the attention of researchers. In this research, an extrusion-based 3D printer, equipped with a direct granule extruder system, was used for 3D printing of the feedstock of the metal powder injection molding (MPIM) process (with 93.7 % by weight of 440 C stainless steel metal powder). The optimal parameters of printing including linear speed (10 mm/s), temperature at the beginning (140 ℃) and end of the barrel (180 ℃), chamber's temperature (60 ℃), and nozzle diameter (0.5 mm) were determined experimentally. The debinding and sintering process was performed on 3D-printed samples. The samples are brittle after the sintering process, in such a way that the failure of the samples occurs by applying a small amount of force to them. According to the scanning electron microscope (SEM) micrograph of the fracture cross-section of the sintered samples, the number of cavities and defects in the samples was negligible and the presence of residual carbon can be seen in the sintered samples. According to the results of X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDAX), the oxidation of iron and chromium elements as well as the presence of residual carbon (7.8 %), are the main factors for the incomplete sintering of the 3D printed samples.

Experimental and numerical modeling of deformation-cracking mechanics of 3D-printed rock samples with single fracture

The analysis of mechanical response and deformation-cracking behavior contributes to the high-efficiency extraction of geo-energy and long-term safety of underground engineering structures. Compared to natural cores, the mechanical properties of 3D-printed samples made from quartz sand as raw material are relatively homogeneous, and can be used for quantitative studies on the influence of natural defects on the mechanical properties of rocks. In this work, 3D-printed samples with single fractures of different crack angles, lengths and widths were fabricated and used for uniaxial compression tests. Adopting the digital image correlation method, the stress-strain distribution during uniaxial compression tests were visualized, and the influence of prefabricated fracture characteristics (dip angle, length, and width) on the deformation-failure process were studied. An extended finite element method subroutine for ABAQUS® software was modeled and used for the uniaxial compression simulation, which was validated by experiments. Then, the influence of mechanical parameters (Young’s modulus, Poisson’s ratio, cohesion, and internal friction angle) on the deformation-cracking mechanics were simulated and studied. The results indicate that, compared to the intact sample, fractures reduce the sample strength. With the extension of fracture length and width, or the decline of fracture angle, both the peak strain and strength of the 3D-printed samples decrease. The splitting tensile failure, or shear failure, or both were determined for the 3D-printed samples with different fracture angles. For the same axial strain, the extension length of the new crack increases linearly with rising Young’s modulus and decreases linearly with increasing Poisson’s ratio. The initial strain of new cracks decreases linearly with increasing Young’s modulus, while little variations are found in samples with different Poisson’s ratio. For the same axial displacement load, the peak stress increases linearly with growing internal friction angle and cohesion. Cited as: Song, R., Tian, J., Wu, M., Liu, J. Experimental and numerical modeling of deformation-cracking mechanics of 3D-printed rock samples with single fracture. Advances in Geo-Energy Research, 2023, 8(2): 126-135. https://doi.org/10.46690/ager.2023.05.06

Influence of infill density on the dynamic behavior of 3D-printed CF-PEKK composites using split Hopkinson’s pressure bars

The dynamic mechanical behavior of 3D-printed CF-PEKK composites has been studied using the split Hopkinson pressure bar (SHPB). Three sets of samples with different infill densities (20, 50, and 100%) were impacted at different impact pressures (1.4, 1.7, 2.0, 2.4 bar) to characterize their dynamic behavior in terms of strain rate, stress, and strain performance. Moreover, the samples’ dynamic response and failure behavior are cross-referenced with each infill density sample's microstructural behavior and physical parameters, which can give an excellent dynamic response under different strain rate ranges. The results showed that dynamic stress and strain behavior are proportional to the infill density with a maximum dynamic stress of approximately 90 MPa with 100% infill density. In addition, the behavior of the transmitted wave during the dynamic impact showed that a sample with less infill density could attenuate/absorb dynamic impact. These results obtained under this impact pressure indicate the high precision and repeatability of the SHPB approach for the tested 3D composites under dynamic loading and prove that the striker bar velocity significantly impacts the amplitudes of different recorded waves to understand the behavior in detail. In addition, high-speed camera images also showed that the 3D-printed composite sample showed that using a higher infill density enhanced both the damage performance and the impact resistance of the three-dimensionally printed composites at each impact pressure because of the minimized intensity and the amount of final macro damage. This study is useful and helpful for design engineers to study the influence of the process parameter of infill on the dynamic behavior of printed composite materials and confirms the growing interest in 3D printing of composite materials to be employed in different engineering applications which are not limited to static or quasi-static loading circumstances but mainly include dynamic loading conditions.

Optimization of 3D Printing Parameters of Polylactic-Co-Glycolic Acid-Based Biodegradable Antibacterial Materials Using Fused Deposition Modeling.

A high incidence of ureteral diseases was needed to find better treatments such as implanting ureteral stents. The existing ureteral stents produced a series of complications such as bacterial infection and biofilm after implantation. The fused deposition modeling (FDM) of 3D printing biodegradable antibacterial ureteral stents had gradually become the trend of clinical treatment. But it was necessary to optimize the FDM 3D printing parameters of biodegradable bacteriostatic materials to improve the precision and performance of manufacturing. In this study, polylactic-co-glycolic acid (PLGA), polycaprolactone (PCL), and nanosilver (AgNP) were mixed by the physical blending method, and the 3D printing parameters and properties were studied. The relationship between printing parameters and printing errors was obtained by single-factor variable method and linear fitting. The performance of 3D printing samples was obtained through infrared spectrum detection, molecular weight detection, and mechanical testing. The printing temperature and the printing pressure were proportional to the printing error, and the printing speed was inversely proportional to the printing error. The 3D printing has little effect on the functional groups and molecular weights of biodegradable antibacterial materials. The addition of AgNP increases the compressive strength and breaking strength by 8.332% and 37.726%, which provided ideas for regulating the mechanical properties. The parameter range of biodegradable bacteriostatic materials for thermal melting 3D printing was precisely established by optimizing the parameters of printing temperature, printing pressure, and printing speed, which would be further applied to the advanced manufacturing of biodegradable implant interventional medical devices.

Mechanical characterization of thermoplastic elastomers based on olefin processed through material extrusion

Thermoplastic elastomeric materials are processable through 3D printing. These materials demonstrate excellent mechanical properties, along with good flexibility. A better understanding of the creation of bonds between the filaments of these copolymers is still needed. When extruded, these materials have shown to have a different behavior compared to commonly known thermoplastic materials. The methodology, hereby presented, relies on the tensile tests of 3D-printed samples of two thermoplastic elastomers based on olefin: TPO 90A and TPO 96A. In order to study the effect of printing parameters on the mechanical behavior of the samples, these have been manufactured following a full factorial design of experiments. Statistical influences were evaluated with an analysis of variance. Layer height and fill density were the variable parameters. Eventually, these two parameters were shown to have a significant effect on the mechanical properties studied (Young’s modulus and yield strength). Once all the results were analyzed, the presented methodology was applied to another set of specimens. These had been manufactured with a different printer and with the same material but colored. The analysis of variance showed that, although the mechanical properties were affected by the color pigments, the trends of this analysis and the recommended manufacturing values did not vary. The results showed that when working with thermoplastic elastomers and in order to maximize Young’s modulus and yield strength, a 0.3-mm layer height and a 75% fill density should be selected.

Optimizing the Rheological and Thermal Behavior of Polypropylene-Based Composites for Material Extrusion Additive Manufacturing Processes.

In this study, composites based on a heterophasic polypropylene (PP) copolymer containing different loadings of micro-sized (i.e., talc, calcium carbonate, and silica) and nano-sized (i.e., a nanoclay) fillers were formulated via melt compounding to obtain PP-based materials suitable for Material Extrusion (MEX) additive manufacturing processing. The assessment of the thermal properties and the rheological behavior of the produced materials allowed us to disclose the relationships between the influence of the embedded fillers and the fundamental characteristics of the materials affecting their MEX processability. In particular, composites containing 30 wt% of talc or calcium carbonate and 3 wt% of nanoclay showed the best combination of thermal and rheological properties and were selected for 3D printing processing. The evaluation of the morphology of the filaments and the 3D-printed samples demonstrated that the introduction of different fillers affects their surface quality as well as the adhesion between subsequently deposited layers. Finally, the tensile properties of 3D-printed specimens were assessed; the obtained results showed that modulable mechanical properties can be achieved depending on the type of the embedded filler, opening new perspectives towards the full exploitation of MEX processing in the production of printed parts endowed with desirable characteristics and functionalities.

Additive manufacturing of nylon composites with embedded multi-material piezoresistive strain sensors for structural health monitoring

A hybrid additive manufacturing process is proposed to incorporate piezoresistive sensors into a polyamide matrix for real-time structural health monitoring. 3D-printed samples were tested under tensile, flexural, and indentation testing using various sizes, numbers, and locations of the sensors, while the electrical resistance was recorded in real-time. Under uniaxial tensile loading, strength reached 36 MPa, and the resistance values linearly increased by up to 105% at ∼150% of strain. During flexural testing, the sensor had higher resistance when it was located above the supports rather than under the loading roller. The conductive paths were placed near the plate's top, middle and bottom sections to localise the damage during indentation testing. The energy absorbed during indentation testing reached 34–36 J. Resistance readings of sensors with 1 cm width showed better linearity and sensitivity than their wide (10 cm) counterparts. Three 2D sensors were interconnected to make a 3D sensor. The resistance values gradually increased after each strike during repeated indentation, but the overall strength remained similar. In summary, this work demonstrates a novel approach toward customisable 3D-printed piezoresistive sensors for detecting global or local damage.

Effects of washing solution temperature on the biocompatibility and mechanical properties of 3D-Printed dental resin material

The use of digital manufacturing, particularly additive manufacturing using three-dimensional (3D) printing, is expanding in the field of dentistry. 3D-printed resin appliances must undergo an essential process, post-washing, to remove residual monomers; however, the effect of the washing solution temperature on the biocompatibility and mechanical properties remains unclear. Therefore, we processed 3D-printed resin samples under different post-washing temperatures (without temperature control (N/T), 30 °C, 40 °C, and 50 °C) for different durations (5, 10, 15, 30, and 60 min) and evaluated the degree of conversion rate, cell viability, flexural strength, and Vickers hardness. Increasing the washing solution temperature significantly improved the degree of conversion rate and cell viability. Conversely, increasing the solution temperature and time decreased the flexural strength and microhardness. This study confirmed that the washing temperature and time influence the mechanical and biological properties of the 3D-printed resin. Washing 3D-printed resin at 30 °C for 30 min was most efficient to maintain optimal biocompatibility and minimize changes of mechanical properties.

Optimizing the Rheological and Thermomechanical Response of Acrylonitrile Butadiene Styrene/Silicon Nitride Nanocomposites in Material Extrusion Additive Manufacturing.

The current research aimed to examine the thermomechanical properties of new nanocomposites in additive manufacturing (AM). Material extrusion (MEX) 3D printing was utilized to evolve acrylonitrile butadiene styrene (ABS) nanocomposites with silicon nitride nano-inclusions. Regarding the mechanical and thermal response, the fabricated 3D-printed samples were subjected to a course of standard tests, in view to evaluate the influence of the Si3N4 nanofiller content in the polymer matrix. The morphology and fractography of the fabricated filaments and samples were examined using scanning electron microscopy and atomic force microscopy. Moreover, Raman and energy dispersive spectroscopy tests were accomplished to evaluate the composition of the matrix polymer and nanomaterials. Silicon nitride nanoparticles were proved to induce a significant mechanical reinforcement in comparison with the polymer matrix without any additives or fillers. The optimal mechanical response was depicted to the grade ABS/Si3N4 4 wt. %. An impressive increase in flexural strength (30.3%) and flexural toughness (47.2%) was found. The results validate that these novel ABS nanocomposites with improved mechanical properties can be promising materials.

Preparation of Polylactic Acid/Calcium Peroxide Composite Filaments for Fused Deposition Modelling.

Fused Deposition Modelling (FDM) 3D printers have gained significant popularity in the pharmaceutical and biomedical industries. In this study, a new biomaterial filament was developed by preparing a polylactic acid (PLA)/calcium peroxide (CPO) composite using wet solution mixing and extrusion. The content of CPO varied from 3% to 24% wt., and hot-melt extruder parameters were optimised to fabricate 3D printable composite filaments. The filaments were characterised using an X-ray diffraction analysis, surface morphology assessment, evaluation of filament extrudability, microstructural analysis, and examination of their rheological and mechanical properties. Our findings indicate that increasing the CPO content resulted in increased viscosity at 200 °C, while the PLA/CPO samples showed microstructural changes from crystalline to amorphous. The mechanical strength and ductility of the composite filaments decreased except for in the 6% CPO filament. Due to its acceptable surface morphology and strength, the PLA/CPO filament with 6% CPO was selected for printability testing. The 3D-printed sample of a bone scaffold exhibited good printing quality, demonstrating the potential of the PLA/CPO filament as an improved biocompatible filament for FDM 3D printing.

Manufacture and Characterization of Polylactic Acid Filaments Recycled from Real Waste for 3D Printing.

This paper studies the thermal, morphological, and mechanical properties of 3D-printed polylactic acid (PLA) blends of virgin and recycled material in the following proportions: 100/0, 25/75, 50/50, and 75/25, respectively. Real waste, used as recycled content, was shredded and sorted by size without a washing step. Regular dog-bone specimens were 3D printed from filaments, manufactured in a single screw extruder. Thermogravimetric analysis indicated that adding PLA debris to raw material did not significantly impact the thermal stability of the 3D-printed samples and showed that virgin and recycled PLA degraded at almost the same temperature. Differential scanning calorimetry revealed a significant reduction in crystallinity with increasing recycled content. Scanning electron microscopy showed a more homogenous structure for specimens from 100% pure PLA, as well as a more heterogeneous one for PLA blends. The tensile strength of the PLA blends increased by adding more recycled material, from 44.20 ± 2.18 MPa for primary PLA to 52.61 ± 2.28 MPa for the blend with the highest secondary PLA content. However, this study suggests that the mechanical properties of the reprocessed parts and their basic association are unique compared with those made up of virgin material.

Effect of Short Carbon Fiber Reinforcement on Mechanical Properties of 3D-Printed Acrylonitrile Butadiene Styrene.

The effect of short carbon fiber (SCF) filler on the mechanical properties of 3D-printed acrylonitrile butadiene styrene (ABS) was investigated. The fused filament fabrication (FFF) method was used for the manufacturing of samples. Elastic properties and strength characteristics of samples made of conventional ABS and SCF-reinforced ABS were compared in tensile and bending tests. Fracture toughness and critical strain energy release rate were also determined. In addition, 3D-printed monofilament SCF-reinforced samples were fabricated, the internal structure of which was analyzed using microcomputed tomography (micro-CT). Based on the tomography data, finite-element (FE) models of representative volume elements (RVEs) of the reinforced material were created and used for the numerical calculation of effective characteristics. Numerical and experimental results for the effective elastic properties were compared with the Mori-Tanaka homogenization technique. The ABS samples filled with SCF showed considerably higher mechanical characteristics than those of the conventional ABS. Finally, the dependence between the strength characteristics and elastic properties of the samples on the diameter of the nozzle used for 3D printing was established. 3D-printed ABS reinforced with SCF demonstrated a gain in tensile strength and fracture toughness by 30% and 20%, respectively. Interlayer adhesion strength in flexure tests showed an increase of 28% compared to pure ABS samples.

Analysis of the Mechanical Properties of 3D-Printed Plastic Samples Subjected to Selected Degradation Effects.

The Fused Filament Fabrication (FFF) method is an additive technology that is used for the creation of prototypes within Rapid Prototyping (RP) as well as for the creation of final components in piece or small-series production. The possibility of using FFF technology in the creation of final products requires knowledge of the properties of the material and, at the same time, how these properties change due to degradation effects. In this study, the mechanical properties of the selected materials (PLA, PETG, ABS, and ASA) were tested in their non-degenerate state and after exposure of the samples to the selected degradation factors. For the analysis, which was carried out by the tensile test and the Shore D hardness test, samples of normalized shape were prepared. The effects of UV radiation, high temperature environments, high humidity environments, temperature cycles, and exposure to weather conditions were monitored. The parameters obtained from the tests (tensile strength and Shore D hardness) were statistically evaluated, and the influence of degradation factors on the properties of individual materials was assessed. The results showed that even between individual manufacturers of the same filament there are differences, both in the mechanical properties and in the behavior of the material after exposure to degradation effects.

Improvement of the Surface Properties of Polyether Ether Ketone via Arc Evaporation for Biomedical Applications.

Polyether ether ketone is a bioinert polymer, that is of high interest in research and medicine as an alternative material for the replacement of bone implants made of metal. The biggest deficit of this polymer is its hydrophobic surface, which is rather unfavorable for cell adhesion and thus leads to slow osseointegration. In order to address this drawback, 3D-printed and polymer extruded polyether ether ketone disc samples that were surface-modified with titanium thin films of four different thicknesses via arc evaporation were investigated and compared with non-modified disc samples. Depending on the modification time, the thickness of the coatings ranged from 40 nm to 450 nm. The 3D-printing process does not affect the surface or bulk properties of polyether ether ketone. It turned out that the chemical composition of the coatings obtained did not depend on the type of substrate. Titanium coatings contain titanium oxide and have an amorphous structure. Microdroplets formed on the sample surfaces during treatment with an arc evaporator contain a rutile phase in their composition. Surface modification of the samples via arc evaporation resulted in an increase in the arithmetic mean roughness from 20 nm to 40 nm for the extruded samples and from 40 nm to 100 nm for the 3D-printed samples, with the mean height difference increasing from 100 nm to 250 nm and from 140 nm to 450 nm. Despite the fact that the hardness and reduced elastic modulus of the unmodified 3D-printed samples (0.33 GPa and 5.80 GPa) are higher than those of the unmodified extruded samples (0.22 GPa and 3.40 GPa), the surface properties of the samples after modification are approximately the same. The water contact angles of the polyether ether ketone sample surfaces decrease from 70° to 10° for the extruded samples and from 80° to 6° for the 3D-printed samples as the thickness of the titanium coating increases, making this type of coating promising for biomedical applications.

Thermal analysis and experimental verification on double-layer microchannel heat sinks with impact jet nested arrays

The present study investigate a novel combined features which make use of impingement jet nested arrays (IJNAs) to strength the thermal performance of double-layer microchannel heat sinks (DMCHS) based on 3D printing technologies. The IJNAs are firstly introduced into the DMCHS to enhance the thermal characteristics compared with the traditional straight and impact jet straight arrays DMCHS. Three 3D-printed test samples were manufactured for experiments, and it is found that the numerical simulations are in line with the experimental measurements. The thermal control of the substrate temperature by introducing IJNAs is very effective, and the reduction in peak temperature on substrate is more than 20 K lower than that of traditional DMCHS. The experimental study and numerical simulation both show that the heat transfer enhancement of the impingement jet and nested structure is very pronounced. Besides, the average Nusselt number of IJNA-DMCHS is 5.33% higher than that of IJSA-DMCHS. Even though the proposed structure of IJNA yields higher pressure drop penalty, the overall thermal performance factor that balances the influence of heat transfer augmentation and pressure drop penalty still favors the proposed IJNA-DMCHS with nested channels, and it outperforms considerably that of IJSA-DMCHS with straight channels.

Numerical predictions and experimental validation on the effect of material properties in filament material extrusion

The numerical prediction of dimensional accuracy and mechanical performance of 3D-printed structures can eliminate or reduce the need to perform trial-and-error experimentation to achieve the desired part quality quickly and at a reduced cost. Therefore, this study focuses on experimental and numerical investigations of the effect of material properties on dimensional control of the material extrusion additive manufacturing process. A thermomechanical model is utilized, validated, and used to predict the part deflections, warpages, and residual stresses in 3D-printed components for two different materials (i.e., polyamide-6 (PA6) and acrylonitrile butadiene styrene (ABS)). In addition, numerical simulations for mechanical testing were performed and validated through experimental investigations. The numerical model considered the effect of material on final product quality and was in close agreement with experimental results. It was concluded that the materials with a lower thermal expansion coefficient (CTE) would provide better dimensional accuracy of 3D-printed parts. In addition, the lower thermal conductivity and temperature variations within the 3D-printed part will further produce precise parts. The controlled ambient environment using a closed chamber can also assist in maintaining desired thermal gradient and avoid non-uniform cooling during the process. Finally, the numerical model accurately predicted the mechanical behavior of 3D-printed samples as validated via experimentation.