No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Mechanical Characterization of 3D-Printed Polymers
Abstract
3D printing, more formally known as Additive Manufacturing (AM), is already being adopted for rapid prototyping and soon rapid manufacturing. This review provides a brief discussion about AM and also the most employed AM technologies for polymers. The commonly-used ASTM and ISO mechanical test standards which have been used by various research groups to test the strength of the 3D-printed parts have also been reported. Also a summary of an exhaustive amount of literature regarding the mechanical properties of 3D-printed parts is included. Specifically, properties under different loading types such as tensile, bending, compressive, fatigue, impact and others. Properties at low temperatures have also been discussed. Effects of fillers as well as post-processing on the mechanical properties have been discussed. Lastly, several important questions to consider in the standardization of mechanical test methods have been discussed.
... The main disadvantage of FFF technology is the low mechanical properties of products [3,4,[12][13][14][15][16][17][18], which limits its use for printing functional products. At the same time, it is possible to have different orientations of the product on the printing platform [12,17,19,20], different strategies for filling the layer [17,18,21], and different directions or angles of laying the thermoplastic beads inside the layer [17,[19][20][21][22][23]. ...
... The main disadvantage of FFF technology is the low mechanical properties of products [3,4,[12][13][14][15][16][17][18], which limits its use for printing functional products. At the same time, it is possible to have different orientations of the product on the printing platform [12,17,19,20], different strategies for filling the layer [17,18,21], and different directions or angles of laying the thermoplastic beads inside the layer [17,[19][20][21][22][23]. If the quality of the welds is low and unstable, this leads to an increase in the anisotropy of the mechanical properties of the product. ...
An approach for improving and maintaining a consistent weld quality of the deposited material during the FFF printing process is proposed. The approach is based on the analysis of the printing process thermal cycle and the real-time nozzle temperature control. The mathematical model of the FFF printing process has been developed with the use of real-time control in the algorithm of numerical implementation. The successful solution of the thermal conductivity problem made it possible to determine segment-wise heating settings for use during the printing process, resulting in a high and stable quality of welding. Comparison of the results of modeling with other well-known mathematical models of the FFF printing process and experimental results showed the adequacy of the proposed model. A maximum deviation of 17.7% between the simulation results and the thermography data was observed. The proposed model was verified using rectangular 3D polylactide shapes printed with and without regulation of the power of the heat source according to the previously estimated settings. The overall quality of regulation, stability of the system, and the PI coefficients of the controller were evaluated using a simulated model of the control system. The results of the experiment fully correspond with the modeling results.
... Several materials have been studied as potential additions to photocurable resins to be used for these technologies, with a view to improving certain characteristics of the polymeric material such as mechanical, optical, and electrical properties. These include bioactive glass, zirconia, alumina, and calcium phosphates [16,[18][19][20]. Calcium phosphates have high mechanical resistance and good bioactivity, and for this reason, they have been used as reinforcements in biocompatible resins to increase cell proliferation and adhesion and promote bone repair [16,21]. ...
... Other calcium phosphates also present high biocompatibility and excellent biodegradability. The latter property is especially important as it allows the ceramic material to be absorbed and promotes the creation of new bone tissue [23,26], favouring the adhesion and proliferation of bone cells, in turn leading to mineralization of the surface [19,27]. ...
In the present work, scaffolds with gyroid TPMS geometry were obtained from a commercial resin of acrylic nature loaded with 0.5% and 1% w/V of calcium phosphate nanoparticles through DLP. The scaffolds obtained presented Young's Modulus between 300 and 400 MPa, which makes them suitable for bone applications. The surface treatment by oxygen plasma carried out on the scaffolds resulted in a notable improvement in the wettability of the surfaces, which favours cell adhesion on the surface of the materials. The in vitro bioactivity assay conducted on the resin/calcium phosphate particles composite material showed that an apatitic layer forms on the surface of the samples from the third day of exposure to simulated body fluid (SBF), indicating that the composite material has in vitro bioactive behaviour. Biological tests demonstrated that the material is not cytotoxic and favours cell adhesion and that the gyroid geometry promotes cell proliferation.
Graphical abstract
... According to ASTM standards there are seven different methods of AM, namely the Material Extrusion (MEX) process, Binder Jetting (BJ) process, powder-bed fusion (PBF) process, Material jetting (MJ) process, vat photo-polymerization (VP) process, direct energy deposition (DED) process, and the sheet-lamination process [2]. Out of these seven technologies, all but the DED and sheet-lamination processes, can be used to manufacture polymer 3-dimensional (3D) objects [3]. The overall work ow of all different AM processes includes several pre-processing, material processing/joining (the printing job), and post-processing steps. ...
This work addresses the issues of entrapment of polymer powder and the post-processing powder removal challenges in surface-based lattice structures 3D printed with powder-bed based additive manufacturing (AM) technology. A ventilation design approach has been proposed to enhance the powder removability from the widely researched three-dimensional gyroid and two-dimensional honeycomb lattice structure. The flow characteristics and mechanical behaviour of the designed lattices were analysed using computational fluid dynamics (CFD) and finite element analysis (FEA), respectively, followed by experimental powder flow and compression testing. HP jet fusion 4200® industrial 3D printer was used for printing the lattice structures for experimental validation. The results showed a 65–85% improvement in powder flowability, with a minimum to severe reduction in mechanical strength of different lattice structures. The study can be applied to designing products with multi-functional properties with surface-based lattice structures by employing the principle of design for additive manufacturing and post-processing (DfAM&PP).
... The printing process is also known as the additive method of manufacturing electronic applications by depositing electronic materials using functional inks along with the normal printing process [3]. As discussed earlier, this process thus eliminates the need for etching and masking and thereby involves environmentally friendly cleaner production compared to that of other traditional methods [4]. ...
In the modern era, smart devices play an important role in day-to-day life, and their
widespread applications are getting huge demand globally. Innovation in the field of
the Internet of Things paves new possibilities for future endeavors of mankind.
Printed electronics is a sustainable way for achieving the widespread popularity of
smart devices around the world and this technology is in its nascent stage. In the
current scenario, massive amounts of e-waste generated due to the digital revolution
and its disposal become a greater challenge for sustainability. Printed electronics are
composed in a process of registering thin functional material (ink) layer combina-
tions on a low-cost substrate that will degrade naturally. This article discusses the
possibilities of printed electronics and its ability to hurdle the limitations of
traditional high-cost electronics, based on rigid silicon, and the production of
different devices on flexible substrates. Efficient use of materials, optimized energy
consumption both in production and utilization, reduction in hazardous substances,
and enhanced recyclability are the several benefits associated with printed electronics
technology. The additive manufacturing method is used in printed electronics
technology and the rate of production is much improved as compared with other
processes. The materials used for printed electronics like ink and substrates are
derived from synthetic or natural polymers. The above-stated reasons make printed
electronics a technology for the future digital revolution. This article discusses
various fabrication techniques like lithographic process for the production of printed electronics and its application in a sustainable manner
... Polyurethane resins offer flexibility, toughness, impact resistance, and diverse mechanical properties for use in automotive parts, sports, and medical devices. Silicone resins are heat-or chemically cured, providing high flexibility, heat resistance, and biocompatibility for applications, such as prosthetics, molds, and gaskets [12][13][14][15][16]. ...
Advancements in 3D printing technologies have led to new implementations in rapid prototyping, microfluidics, tooling, dentistry, biomedical devices, drug delivery, and tissue engineering. Stereolithography techniques, which are photopolymerization-based processes, contribute to the optical, chemical, and mechanical properties of 3D printed materials using versatile polymer chemistry. This study used potassium titanate powder (K2Ti8O17) as an additive to enhance the mechanical strength of photocurable resins. PEG was selected as the stabilizer to optimize the dispersion and precipitation of potassium titanate. The flexural strength, hardness, and tensile strength were compared to assess the mechanical strength of the 3D printing resin. The flexural strengths of the printed specimens were in the range of 15–39 N/mm2. The measured surface hardness and tensile strength were 41–80 HV and 2.3–15 N/mm2, respectively. The output resolution of the potassium titanate/acrylate resin was tested using a line-pattern structure. 3D printing resin without stabilizers produced lines with a thickness of 0.3 mm, whereas 3D printing resin containing a stabilizer produced lines with a thickness of 0.2 mm. The flexural strength and pattern thickness results suggest that the potassium titanate/acrylate resin can be utilized as a 3D printer resin, suggesting new possibilities for potassium titanate materials.
... Mubarak et al. [45], as well as Feng et al. [47] insisted that VP technologies were considered as low-cost AM techniques. In contrast, Dizon et al. [48] mentions SLA techniques as being high energy consuming due to the usage of lasers that results into high heat losses, which is indirectly converted into money loss. Wu et al. referred to VP produced parts as being 'cost-effective' and emphasized on the importance of this factor for hearing aids, orthopedics and prosthetics, and surgical guides and models [49]. ...
Additive manufacturing has shown advantages for nanocomposite fabrication. Despite VAT-photopolymerization being one of the first developed 3D printing technologies, high device costs made it a technology that was difficult to access. The massive production of these devices in recent years has opened this technology to everyone. Stereolithography and Digital light processing are the most prominent technologies used in this field. This systematic review studied 217 articles regarding SLA and DLP for additive manufacture of nanocomposites. The main finding of this systematic review shows that further research on circular economy and life cycle assessment of the SLA and DLP technologies is urgently needed. Also, a deeper discussion on the technology and material costs is recommended in order to give a more detailed insight on the final cost of these 3D-printed nanocomposites.
... A wide variety of polymer materials are available for 3D printing, each having unique characteristics based on its molecular structure and treated differently for each printing method. Thermoplastics, which are melted during extrusion and subsequently hardened after deposition, are often used in extrusion processes for 3D printing [19]. For instance, compared to pure polystyrene, the popular thermoplastic acrylonitrile butadiene styrene (ABS) displays better chemical resistance and good impact strength [15]. ...
This review research assesses the numerous 3D printing methods utilized in medical applications and the materials and design methods that are associated with the current and existing technology. The article thoroughly examines the advantages and disadvantages of various techniques and materials and the difficulties of applying 3D printing technology to the medical sector. Further research and development are required to overcome current challenges since the review highlights the importance of design strategies in achieving positive medical outcomes. Overall, the article provides a thorough overview of the state of 3D printing in medical applications today and its potential to revolutionize the industry.
... In this way, up to 20 mol% of ionic species are typically seen in ionomeric polymers because the ionomer polymers are made into chains containing ionic groups, and they enrich/add the polymer matrix with enough counterions by adjusting the ionic content; an ionomeric polymer with self-healing capabilities can have different properties [16,17]. Fused Deposition Modeling (FDM) Technology is a 3D-printing process used to manufacture novel materials [18]. Among its advantages are faster production and the freedom to customize the shapes and geometry of the produced samples at an affordable cost [19]. ...
This research work studies the self-healing ability, mechanical properties, and shape memory of the polymer Surlyn® 8940 with and without multiwall carbon nanotubes (MWCNTs) as a nanoreinforcement. This polymer comes from a partially neutralized poly(ethylene-co-methacrylic acid) (EMAA) ionomer copolymer. MWCNTs and the polymer went through a mixing process aimed at achieving an excellent dispersion. Later, an optimized extrusion method was used to produce a uniform reinforced filament, which was the input for the 3D-printing process that was used to create the final test samples. Various concentrations of MWCNTs (0.0, 0.1, 0.5, and 1.0 wt.%) were used to evaluate and compare the mechanical properties, self-healing ability, and shape memory of unreinforced and nanoreinforced materials. Results show an enhancement of the mechanical properties and self-healing ability through the addition of MWCNTs to the matrix of polymer, and the specimens showed shape memory events.
... in general, 3d-printed structures are mechanically weaker compared to their metal counterparts. A major issue with 3d-printed structures is mechanical anisotropy based on build orientation [56,57]. the simulations conducted in the current study used only constant force analysis. ...
Purpose
Steering a wheelchair while navigating through manual doors or against obstacles is challenging for some users. Previously, a low-cost, low-tech accessory made using off-the-shelf components, conventional manufacturing, and 3D-printed fasteners demonstrated the proof-of-concept for uncrossable positive obstacle pushing or gliding. Current work presents the fabrication and testing of an entirely 3D-printed prototype of the accessory.
Methods
The accessory was 3D-printed using ABS (10% fill density) in sections. A finite element stress analysis simulation was performed for the entire accessory. Prototype tests were done with the accessory installed on an unoccupied powered wheelchair against a door and an obstacle with ∼25 N and ∼50 N resistance forces, respectively.
Results
The maximum stresses in none of the crucial components exceeded the break strength of ABS. Test results demonstrate the ability and mechanical robustness of the fully 3D-printed accessory to push open manual doors, allowing easy navigation through doors, and to push or glide against obstacles. The current prototype improves over the previous prototype in terms of manufacturability, weight, design, and safety.
Conclusions
To the best of our knowledge, this is the first demonstration of an entirely 3D-printed wheelchair accessory that pushes or glides against uncrossable positive obstacles. Future studies would involve end-user satisfaction assessment and functionality evaluation in different scenarios under clinical supervision. The pushing or gliding ability of the accessory could be beneficial to wheelchair users with neuromuscular disorders or paraplegia.
... The research conducted to date has revealed that this industry holds a market share worth tens of billions of dollars. [1][2][3][4][5] While AM technology encompasses a range of techniques such as stereolithography (SL), polyjet, laminated object manufacturing (LOM), selective laser sintering (SLS), prometal, laminated engineered net shaping (LENS), and electron beam melting (EBM), the most widely employed method is fused deposition modeling (FDM). The reason behind the widespread use of FDM is its low equipment and material costs, compact and simple machine design, low energy requirement, and the absence of additional processes such as resin curing. ...
While 3‐dimensional (3D) printing technology is advancing rapidly, commonly used filament materials are struggling to meet growing expectations. Polyamide (PA) is a material with high potential to replace commonly used low‐performance filament materials, thanks to its cost‐effectiveness and optimal material properties compared to advanced engineering materials. To explore this potential, the thermal, thermomechanical, and mechanical properties (at different temperatures), as well as the wear characteristics, of PA, short carbon fiber reinforced‐PA (SCFR‐PA), and short glass fiber reinforced‐PA (SGFR‐PA) filaments were comparatively examined in this study. Differential scanning calorimeter analysis (DSC), Dynamic Mechanical Thermal Analysis (DMA), uniaxial tensile tests, and Shore D hardness tests were conducted on the 3D printed specimens. The yield strength decreased by 48% and 73%, respectively, for neat PA as compared to room temperature when tested at 40 °C and 60 °C, while for SCFR‐PA, it decreased by 40% and 60%, and for SGFR‐PA, it decreased by 33% and 48%, respectively. The findings obtained from wear tests conducted on both bottom and top surfaces have demonstrated that glass reinforcement yields better results than carbon reinforcement. The experimental findings have been compared with SEM images, revealing their consistency.
Highlights
This study focuses on the performance evaluation of 3D printed PA and its composites.
The mechanical properties of the materials at different temperatures were compared.
Adhesive wear behavior is not directly related to fiber type, wear surface or hardness.
Morphological analysis was conducted to elucidate the influence of fiber type on mechanical properties and wear behavior.
... Several other studies have investigated the effect of printer settings on mechanical properties of the final part. In addition to the work on modulus just discussed, the effect of changing layer thickness [13][14][15][16], nozzle diameter [14], raster angle [17], and print speed [15,18] on a part's mechanical properties is readily available in the literature. Sukindar et al. investigated the effect of porosity level on the performance of scaffold structures under compression [19]. ...
Fused deposition modeling (FDM) additive manufacturing (AM) printers frequently take significant trial and error to achieve desired dimensions, which has been fairly well investigated in the literature. What remains largely unexplored is the ability of a printer to match a desired primary natural frequency of a part. This can be critical when it comes to using printed parts as replacement parts in a moving system where a drastic change in a part’s natural frequency may appreciably change the dynamics of the system. This work uses iterative learning control (ILC) to create printed bars that match both desired dimensions and primary natural frequencies. Multiple case studies are presented and the best results were reprinted to investigate their repeatability and transferability. Dimensional error when using an ILC algorithm was comparable to that when deploying the default settings. Conversely, significant improvements in reducing warp and matching desired primary natural frequencies were found. These improvements were maintained when the output was printed on another machine in the same environment, indicating promise for deployment in a mass production setting. These results show that the presented ILC algorithm is capable of reducing error in both warp and desired primary natural frequency for simple parts on desktop FDM printers and lay the groundwork for further investigation with commercial grade and metal additive processes.
... There were various types of additive manufacturing processes such as binder jetting, direct energy deposition, material jetting, material extrusion, sheet lamination, powder bed fusion, and vat photopolymerization process. Over the other additive manufacturing processes, the fused filament fabrication (FFF) or fused deposition modeling (FDM) process demonstrated greater flexibility in the way of manufacturing feasibility of a range of material and part functionalities [5,6]. In this process, the part gets fabricated layer-by-layer steps extruded from a heated nozzle (Fig. 2) according to the set of coordinates derived from the targeted part standard tessellation language (STL) file [7]. ...
Manufacturing complex composite parts using the fused filament fabrication process has shown tremendous potential in terms of saving valuable manufacturing time and cost against conventional manufacturing processes. The use of nylon short carbon fiber composite has a wider range of applications, particularly in the development of impact-resisting structural parts in the aviation and automobile domain. In this investigation, the Izod impact characteristics of 3D printed nylon short carbon fiber with the combinational influence of layer thicknesses (0.1 mm, 0.15 mm, and 0.2 mm) and infill density (80%, 85%, 90% and 95%) are investigated and analyzed. Among the combination of various layer thicknesses and infill densities, the impact absorption of the composite specimen with 85% infill density and 0.2 mm layer thickness showed a maximum impact resistance value of 237.4 J/m. Scanning electron micrography is conducted to examine and analyze the fracture surfaces of the printed specimens. From micrograph analysis, it is confirmed that the interfacial gaps in the mesostructure, which enable fiber bridging and contribute to the highest impact resistance, are what cause the localized matrix deformation at the fracture zone.
... Recently, much research has been done on additive technologies. In articles [7,8], various materials and printing processes were investigated that can be used to produce car parts. The authors also discuss the quality and reliability of parts manufactured using 3D printing. ...
The article highlights the experience of using 3D printing at automotive enterprises manufacturing automotive wiring. The primary attention was paid to optimizing technologies and modernizing equipment in 3D printing in production conditions. This helped to improve the printing quality at the enterprise and reduce energy consumption during mass printing of parts. The article aims at improving quality and reducing energy consumption during 3D printing in serial production conditions. The technique’s novelty consists of a complex of production optimizations combined into a production rack to improve 3D printing. During the research, negative factors affecting print quality and their elimination were analyzed. An experimental setup for 9 printers was created. As a result, ways to increase energy efficiency according to environmental standards were implemented under the mass production of 3D parts. Overall, the applied technology allowed for reducing the time for the development of new prototypes. This made it possible to reduce the produced parts cost and allowed for implementing urgent changes in manufacturing enterprises.
... Tests were performed at a speed of 1 mm/min. Two batches of ten Type IV samples (33 mm of gauge length, 4 mm of thickness, and 6 mm of width) were fabricated following the parameters shown in Table 1 (rPC) and Table 2 (rPC/ABS) [71,72]. To avoid interlayer voids, the specimens were printed with a 100% rectilinear infill. ...
Distributed recycling and additive manufacturing (DRAM) holds enormous promise for enabling a circular economy. Most DRAM studies have focused on single thermoplastic waste stream. This study takes three paths forward from the previous literature: 1) expanding DRAM into high-performance polycarbonate/ acrylonitrile butadiene styrene (PC/ABS) blends, 2) extending PC/ABS blend research into both recycled materials and into direct fused granular fabrication (FGF) 3-D printing and 3) demonstrating the potential of using recycled PC/ABS feedstocks for new applications in circular economy contexts. A commercial open source large-format FGF 3-D printer was modified and used to assess the different printability and accuracy of recycled PC and PC/ABS. The mechanical properties (tensile and impact) following the ASTM D638 and D6110–18 standards were quantified. A weather simulation test (ASTM D5071–06) was performed to assess outdoor performance. Finally, two applications in sporting goods and furniture were demonstrated. In general, better printability was achieved with recycled PC/ABS compared to recycled PC, as well as good dimensional accuracy at printing speeds of 30 and 40 mm/s. Minimal qualitative differences and discoloration were visible on the samples after accelerated weather exposure, with results in accordance with the state-of-the-art. The rPC/ABS results from tensile tests show similar values to those of rPC for elastic modulus (2.1 ± 0.1 GPa), tensile strength (41.6 ± 6.3 MPA), and elongation at break (2.8 ± 0.9%), which are also comparable with previous studied virgin 3-D printed filaments. Similarly, impact energy (115.78 ± 24.40 kJ/m2) and resistance values (810.36 ± 165.77 J/m) are comparable in the two tested formulations, reaching similar results compared to FFF 3-D printed filaments, as well as virgin materials for injection molding. Finally, the two demonstration products in the sporting goods and furniture sectors were successfully fabricated with rPC/ABS, achieving complex patterns and good printing speeds for recycled feedstocks. It is concluded rPC/ABS blends represent a potential high-performance feedstock for DRAM, validating its use in direct FGF 3-D printing systems and potential applications for a circular economy.
... Despite FFF's popularity, parts fabricated with FFF tend to be weaker and more brittle than those fabricated with traditional thermoplastic formative manufacturing (e.g., injection molding, extrusion) or other forms of thermoplastic AM (e.g., powder bed fusion/selective laser sintering). [1][2][3] Worse properties may be caused by poor interlayer welding, 4,5 the presence of voids, 6,7 extrudate shape, 8,9 compositional variation across the extruded road, 10 or a combination of factors. ...
Additive manufacturing offers reduced lead time between design and manufacturing. Fused filament fabrication, the most common form of material extrusion additive manufacturing, enables the production of custom‐made parts with complex geometry. Despite the numerous advantages of additive manufacturing, reliability, reproducibility, and achievement of isotropic bulk properties in part remains challenging. We investigated the tensile behavior of a model polycarbonate system to explore what leads to different tensile properties, including sources of ductile versus brittle fracture. We utilized a one factor at a time (OFAT) design of experiments (DOE), printed single road‐width boxes, and performed tensile tests on specimens from these boxes. Additionally, we characterized the cross‐sections of parts printed under different conditions and their subsequent fracture behavior. The results demonstrate that isotropic bulk properties are achievable by printing at high speeds, and provide mechanisms to explain why.
Highlights
Printing at high speeds leads to improved mechanical properties.
Printed samples undergo a mix of ductile and brittle failure.
Jagged fracture path is associated with superior adhesion.
High layer times lead to worse interfacial bonding.
... We analyzed the potential reasons to guide further improvements of the model. Regarding Q3, the relatively lower rating could be attributed to the inferior hardness and wear resistance of the resin compared to that of natural teeth [27]. For future enhancements, more durable 3D printing resins could be considered for model fabrication. ...
Ledge formation presents a significant challenge in endodontic treatment. Yet, there is still a lack of educational tooth models for hands-on practice. This study aimed to create and evaluate a tooth model for ledge management practice. A natural tooth with curved roots was collected for scientific use under ethics committee approval. Following initial root canal preparation, the tooth was scanned using micro-computed tomography (μCT) and 3D reconstructed. A K-file, created via computer-aided design (CAD), was partly inserted into the root canal wall of the 3D reconstructed tooth. By subtracting the K-file from the tooth, a tooth model with a root canal ledge was produced. The model was then 3D printed for a hands-on workshop. An eight-item Likert-scale questionnaire was administered to 20 postgraduate students and 10 endodontists to assess the model’s quality and training effectiveness. In addition, the success rate of bypassing and correcting the root canal ledge was documented. The feedback from both the students and experts was positive, and the results of the Mann–Whitney U test indicated no statistically significant differences found between the two groups (p > 0.05). The success rate of the students and the experts was 85% and 100%, respectively. In future applications, this novel tooth model is expected to address the existing gap in endodontic education and provide benefits for dental practitioners.
... By controlling the motor rotation speed, different levels of apparent gravity can be generated. Polylactic acid (PLA) is a popular thermoplastic material used in 3D printing 46,47 . The mechanical properties of the PLA filament used in this study are listed in Table 1. ...
Additive manufacturing (AM) has gained significant attention in recent years owing to its ability to quickly and easily fabricate complex shapes and geometries that are difficult or impossible to achieve with traditional manufacturing methods. This study presents the development of a high-gravity material extrusion (HG-MEX) system, which generates a high-gravity field through centrifugal acceleration. In this process, the material is dissolved by heating the nozzle and subsequently deposited on the construction platform. The primary objective of this research is to evaluate the positive effects of gravity on material extrusion (MEX), which is a key aspect of AM. To accomplish this, a combined machine comprising a MEX unit and centrifuge is constructed. This HG-MEX system is used to analyze and reflect the influence of gravity on the material extrusion. The experimental evaluations demonstrate that the application of high gravity is a promising approach to improve the shape accuracy and performance of the parts fabricated through MEX. Notably, our results confirm the feasibility of utilizing MEX under high gravity to enhance performance in AM processes.
... In contrast to traditional hot glue guns, 3D printers have a nozzle that is about 0.1 mm to 2.0 mm in diameter. Nowadays, FFF technology is one of the most popular 3D printing techniques [1]- [6]. However, post-processing is sometimes required for this type of technology to improve the layer adhesion strength and surface finish of 3D-printed parts [2]. ...
3D printing is an additive manufacturing method that turns digital design into an actual product. A 3D-printed part sometimes requires post-processing to enhance its physical and mechanical properties. Acetone vapor polishing is one of those techniques which is highly beneficial in smoothing 3D-printed parts made of acrylonitrile butadiene styrene (ABS). Previously, an acetone vapor polishing device using a mist maker was developed at the Bataan Peninsula State University. However, for a more efficient polishing method, an optimized vapor polishing device using heat has been developed in this study. Using a heating device, which is
an insulated nichrome coil, shows a more gradual and fine vaporization of acetone unlike the mist maker. To further assess the efficiency of the optimized device, the researchers tested the dimensional accuracy, surface roughness, tensile strength, and impact strength of polished and unpolished ABS 3D-printed specimens. The findings showed that the change in surface roughness of the polished cube specimens did not significantly alter their physical geometry. The tensile test reveals that the overall elasticity of the polished tensile specimens has increased noticeably. The impact test also shows that the polished specimen can absorb more impact from a swinging pendulum compared with unpolished specimen. Thus, all testing procedures indicated that post-processing using the optimized vapor polishing device improved the overall physical and mechanical properties of the polished ABS 3D-printed specimens.
... In laser-based AM processes, energy density can be considered as a special parameter which includes some of the most significant factors for SLS process and affects sintering directly; thus, several authors focused their studies mainly on this parameter [7]. Caulfield et al. [8] investigated the effect of energy density parameter and the build orientation in SLS process. ...
Additive manufacturing (AM) is now considered a reasonable alternative for fabricating polymer parts with sufficient strength, dimensional accuracy and surface quality, able to be used in demanding engineering applications. Selective Laser Sintering (SLS) is one of the most popular AM techniques for polymers able to produce complex geometries with acceptable quality. However, in order to meet the necessary requirements, process parameters need to be controlled. Thus, in the present study the effect of Volumetric Energy Density (VED) on mechanical properties of Polyamide-12 (PA12) specimens is investigated with a view to determine the necessary conditions for improved strength of produced parts. After comprehensive analysis of the results via statistical methods was carried out, it was found that increased VED leads generally to improved mechanical properties and that in most cases regarding Young’s Modulus and Ultimate Tensile Strength (UTS) laser power causes even higher mechanical properties, suggesting that concerning the mechanical properties the most preferable combination of process parameters is the 26 W laser power and 0.9 J/mm3 VED. On the other hand, the in-between VEDs of 0.5 and 0.7 J/mm3 tend to have lower Coefficient of Variation implying a higher degree of repeatability for the process.KeywordsSelective Laser SinteringPolyamide SpecimensVolumetric Energy DensityMechanical Properties
... Additive manufacturing (AM) is very used in rapid prototyping design. The AM is a more agile way to produce a given component (Dizon et al., 2018). It is a process that, allied to the market demands of creating and making products in a shorter period, helps designers and engineers materialize their ideas. ...
Purpose-Additive manufacturing (AM) has been one of the most highlighted processes of the last few years. AM prints complex parts and items from 3D files regarding different materials, such as polymers. Moreover, there are different AM techniques available for polymers, such as selective laser sintering. In the SLS technology, polyamides 11 and 12 lead 88% of the market. These materials are high-cost and use an average of 50% of virgin material at each printing. It is possible to use lower rates of virgin material, but at least 30% is recommended. Low rates of virgin material decrease mechanical properties.
Design/methodology/approach-This study aims to evaluate the influence on the mechanical properties of the percentage of reused PA12 in parts manufactured by the SLS process. The specimens of PA12 were manufactured with a percentage of virgin/reused polymer of 50/50, 40/60, 30/ 70, 20/80 and 10/90. We considered three distinct printing directions to compare the mechanical properties of the specimens: horizontal, perpendicular and vertical.
Findings-The results showed that when the percentage of reused material increases, the tensile strength limit (TSL), flexural strength limit and Shore D hardness decrease. Another aspect visualized was the fragile behavior presented in the vertical specimens. In addition, DSC analysis indicated a 2% reduction of crystallinity. Scanning electron microscopy images revealed spherical voids and unfused particles of PA12 at the fracture of tensile test specimens. The material thermal history and unfused particles could decrease the material properties.
Originality/value - We observed that the mechanical properties, such as the TSL, flexural strength limit and hardness, decrease as the percentage of reused material increases. In addition, the process presented a printing-direction dependence, where the vertical direction presented as the more brittle between the ones used.
Carbon fiber-reinforced composites (CFRCs) have been widely used in automotive, aerospace, sports equipment, and other industrial fields, due to the higher strength-to-weight ratio and modulus compared with metals and alloys. Innovations in additive-manufactured CFRCs have opened up new avenues for designing and manufacturing high-performance, low-cost complex composite structures. According to the structure and substrate type of carbon fiber, this paper firstly reviews the existing feasible technologies as well as their key elements and focuses on the research of additive manufactured CFRCs by fused deposition molding (FDM) and selective laser sintering (SLS). Furthermore, the typical applications and envisions of additive manufactured CFRCs were elaborated. Moreover, the existing challenges and problems are summarized from the aspects of materials, equipment, and software. In the future, more interdisciplinary research is needed on advanced materials, multiple processes, advanced equipment, and structural design, and there will be a broader research space for robot-assisted additive manufacturing and green manufacturing methods.
This study investigated the influence of specimen geometry on the mechanical properties of 3D‐printed parts by material extrusion (MEX). Four widely used technical standards were evaluated (ASTM D638, ASTM D3039/D3039M‐14, ISO 527/2, and ISO 37), and all possible geometries were tested. The specimens were subjected to uniaxial tensile loading using a universal testing machine to obtain the mechanical properties of ultimate tensile strength, yield strength, and Young modulus. Mean, , and values, as well as (number of specimens tested to reach at least 10 valid data) are geometry‐dependent. A critical analysis of these data allowed proposing the standard evaluation index () of the specimen geometry (standard) based on data variance and test efficiency to achieve valid data. The results indicate that ASTM D638 performed better than any other standard. For investigations involving the mechanical properties of tensile strength Types I and II (ASTM D638) are the most recommended specimens geometry (standard) for 3D MEX printing because it combines the lowest with the minimum . By following it, researchers and material suppliers can ensure accurate and reliable assessments of the mechanical properties of 3D‐printed parts, contributing to increased safety, reliability, and quality in additive manufacturing. Notes: MEX – Material Extrusion, ASTM – American Society for Testing and Materials, ISO – International Organization for Standardization, SD – Standard Deviation, CV – Coefficient of Variation, – Number of specimens tested to reach at least 10 valid data, – Standard Evaluation Index.
Additive manufacturing has emerged as a trending methodology for producing different simple to complex geometries in minimum lead time, which in turn gives better quality attributes when compared to conventional manufacturing procedures. Fabrication of polylactic acid-based porous scaffold prototypes by 3-dimensional printing has been extensively performed successfully by many researchers. The dimensional accuracy of the 3-dimensional printed part is a very crucial aspect of bone tissue engineering. Dimensional precision of 3-dimensional biomimetic scaffolds has been a response characteristic somehow less focused on by researchers, though it is essential as it acts as a stereotype for defect recuperation while consequently developing extracellular matrix and bone regeneration. The present paper fosters re-tuning the process parameters of a fused deposition modeling based 3-dimensional printer while considering the dimensional precision as a response parameter by the Taguchi optimization technique using a full factorial design L27 orthogonal array set of design of experiments. The crystallinity of the polylactic acid filament material was assessed using differential scanning calorimetry and X-ray diffraction. The thermal breakdown of filament material was investigated utilizing a thermogravimetric analyzer. According to Taguchi’s signal-to-noise ratios, the optimum values were 0.14 mm of layer thickness, 20 mm s ⁻¹ of printing speed, and 80 % of infill percentage. In order to justify the results, response surface methodology was employed. R -square values for Taguchi and the response surface models were 88.61 % and 68.71 %, respectively.
Fused filament fabrication (FFF) has become a de facto choice to fabricate complex-shaped polymer components. Recently, the potential of this technique has been explored in the fabrication of lightweight components due to its capabilities. Various articles have been reported based on the use of FFF process for the development of lightweight structures. In order to identify the current status, challenges, and research gaps in this domain, a thorough review of the existing articles is needed. Therefore, the present article aims to review the development of lightweight components through FFF. Different strategies adopted to develop lightweight components are highlighted with the challenges and research gaps. The outcome of the study may be useful in developing components for weight-sensitive applications using FFF process.
One of the most widely used 3D printers is the Fused Deposition Modelling (FDM) printer. However, it has a very long printing process which may encounter printing failure and cause wastage of resources. Therefore, in this study, an attempt to design and develop a home-made and simple automatic filament changing system that is compatible with FDM printers using Bowden tube extrusion system. The designed system is expected to refill filaments particular for overnight 3D printing process. Axiomatic Design and TRIZ are used in this study to systematically design and solve problems faced throughout this research project. Conceptual designs were derived, and the final conceptual design consists of Central Control Sub-System, Filament Guide Sub-System, Merger Sub-System, and Spool Rollers Sub-System. The most critical sub-systems are the Filament Guide Sub-System and Merger Sub-System, which allows filament to refill without human interaction and allow two filament inputs to pass through a merging component to enable one single output. For the Central Control Sub-System, Arduino programming language was used with a MAKER UNO board, an Arduino compatible low-cost microcontroller to control the refilling process. Three limit switches which act as 2 input sensors and 1 output sensor respectively working in tandem with and 2 stepper motors were used to actuate the refilling process. The design of the automatic filament changing system was successful and the testing of the system was successful on the sub-systems level.
Additive manufacturing technologies have become the focal point of research and development studies, thanks to their production flexibility, increasing material diversity, and ease of access. Additive manufacturing methods have superior advantages, especially in the manufacture of parts with complex geometry, produced in small numbers, and the possibility of rapid structural change. In areas where there is no project-based and mass production such as the aviation sector, it has started to be not preferred to a significant extent. The fused filament extrusion method is the process of combining thermoplastic materials in layers through a heated nozzle. This study produced propeller designs that allow an unmanned aerial vehicle (UAV) to be used in different missions by fused filament fabrication method using pure polymer and polymer matrix composite filaments. The mechanical properties and force generation performances of the produced propellers were tested. Propellers subject to bending, buckling, and centrifugal forces were manufactured using polyamide 6 and carbon fiber-reinforced polyamide 6 matrix composite filaments. The production of UAV propellers by additive manufacturing using engineering plastics and composite materials is an innovative method, and it is aimed to provide benefits in interaction with UAV and three-dimensional (3D) printers, the number of which is increasing day by day.
Nowadays new applications based on the 3D printing technique demand increasingly strict product quality requirements. The in-situ monitoring of variables associated with the manufacturing process through the application of different techniques could help to evaluate the process and ultimately to ensure product quality. In this regard, the acquisition and evaluation of variables and indexes derived from thermographic analysis during the process are key for an early defect detection and can contribute to quality estimation. In this work, a new methodology is proposed for the monitoring and analysis of the additive manufacturing process based on the processing of thermographic images from an LWIR (Long Wave Infrared) camera. The methodology and the suitability of the variables and indexes extracted during the monitoring of the manufacturing process are discussed for the case of a 3D fused filament fabrication of polymers.
Formulation of customized drug delivery systems is considered as an effective approach to fulfill the individualized needs of the patients.
In this study, differential release bilayer tablets containing clarithromycin (CAM) as sustained release (SR) and levofloxacin (LVX) as immediate release (IR) were fabricated by bridging the techniques of hot melt extrusion (HME) and fused deposition modeling (FDM). Both processes were optimized to minimize the drug degradation and to achieve the safe deposition of drugs in their respective layers. This design may offer better clinical efficacy, better patient compliance and may overcome side effects caused by the generalized dosing.
In vitro drug release studies confirmed that almost 100% of LVX was released within 1 h, while CAM showed sustained drug release for up to 24 h. The thermal stability of drugs and polymers was evident from the differential scanning calorimetry (DSC) result. Powder X-ray diffraction (PXRD) and DSC results showed a decrease in the crystalline behavior of drugs after FDM. The Fourier rransform infrared spectroscopy (FT-IR) data showed no significant interactions between drugs and polymers after incorporation in the final formulation.
This work illustrated the potential applications of HME and FDM in formulation of customized drug delivery systems to fulfil the individualized needs of the patients.
3D printing is a layer by layer deposition process, which results in highly anisotropic structures, and contain interfaces. Complex shapes manufactured by 3D printing carry defects. Complete elimination of these defects and interfaces is not possible, and these defects degrade the mechanical properties. In the present study, mechanical properties of printed dog bone samples are quantified as a function of building parameters, in particular, filling patterns, raster angle, and orientation of build direction with respect to that of loading, in polylactic acid (PLA). The tensile strength of 3D printed PLA is the same for hexagonal and linear pattern filling when build direction is along thickness and width, and failure was initiated at the defects in the structure, while better overall toughness is offered by hexagonal pattern filling. Build direction along specimen gauge length gives very low tensile strength and toughness, and failure happens between the printing layers. To minimize the defects especially near the grip section, cuboid sample were first deposited, and micro-machined by laser into dog bone shape to perform tension test. Tensile strength and elastic modulus of micro-machined samples are surprisingly lower, while failure strain is highest among line filling printed samples. Damage resistance was quantified in terms of work of fracture, and hexagonal filling provided better damage resistance than line filling patterns for conditions of 0º raster angle with respect to the crack whereas line filling with 45º and 90º raster angle tolerated damage better than hexagonal filling.
The aerospace industry has been the pioneer of human life with its high technology. The sector in which the developments in materials science find the first application area and where research and development studies are carried out intensively is the aerospace industry. Developments in materials science are at the primary point in realizing the current performance of aircraft. The developments in additive manufacturing technologies and the applications of these technologies also play an important role in the aerospace industry. Additive manufacturing technologies offer important opportunities in the sector where complex geometries, a low number of parts without mass production, and lightness are at the forefront. The use of additive manufacturing technologies in the manufacture of aircraft structural parts, components, and equipment, where polymer-based materials are increasingly used, offers sustainability, cost reduction, and topology optimization opportunities. In this study, short carbon fiber-reinforced thermoplastic matrix specimens were produced by the FFF method. The changes in the mechanical and thermal properties of short fiber reinforcement were investigated. Studies have been carried out to develop environmentally friendly materials that can be used in the aircraft cabin interior equipment.
Injection molded (IM) and additively manufactured (AM) selective laser sintered (SLS) Nylon-12 was irradiated with gamma irradiation to determine the damage mechanism. Modulated differential scanning calorimetry was used to separate the thermodynamic (reversible) and kinetic (non-reversible) heat flows and evaluate how manufacturing method and radiation dose impacted the thermodynamics of melting, along with thermogravimetric analysis (TGA) to investigate thermal stability. Tensile testing and fractography were utilized to evaluate mechanical behavior. The bulk crystallinity of SLS Nylon-12 was not significantly affected by gamma radiation and was estimated to be 38.2 ± 2.3% averaged over all doses. Ultimately, 20 MRad of exposure to SLS Nylon-12 reduced the samples’ early-stage thermal stability by ca. 14.3 °C as measured by TGA, suggesting that the radiation may have contributed to breaking chemical bonds and/or affecting chain entanglement within the polymer structure. The ultimate tensile strength (UTS) decreased with irradiation, suggesting that radiation exposure has a weakening effect (possibly due to chain scissioning) as well as degrading particle coalescence with sintered Nylon-12. SLS Nylon-12 is more susceptible to radiation; the average UTS of Nylon-12 SLS and IM decreased by 54% and 9%, respectively. Injection molding completely transforms \(\alpha\)-form to \(\gamma\)-form and results in a lower void volume than SLS.
The objective of the study was to fabricate tailored extended-release tablets of blood thinner Ticagrelor as once-daily dosing using additive manufacturing for better compliance in heart failure therapy. The solid work design of the tablet was printed using hot melt extrusion (HME) based 3D printing by optimized mixture of Eudragit RS-100, plasticizer and drug for producing extrudable and printable filaments. FTIR and TGA results showed no covalent interaction among ingredients and no decomposition during HME process, respectively. Friability, weight variation, assay and content uniformity tests met USP requirements, while the mean hardness of the tablets was calculated in a value between 40 and 50 kg. According to DSC and XRD results, the crystallinity state of the Ticagrelor was converted to an amorphous one in the tablet matrix. Smooth surfaces with multiple deposited layers were observed using SEM. In comparison, the maximum Ticagrelor release of 100% after 120 min from Brilinta® tablets was decreased to 97% in 400 min from the 3D tablet at infill of 90%. Korsmeyer-Peppas kinetic model showed the drug release mechanism is affected by diffusion and swelling. In general, fabrication of the extended-release 3D printed tablet of Ticagrelor using HME-based-additive manufacturing has the potential to provide specific doses with tailored kinetic release for personalized medicine, improving adherence at point-of-care.
Nowadays, the additive manufacturing of multifunctional materials is booming. The fused deposition modeling (FDM) process is widely used thanks to the ease with which multimaterial parts can be printed. The main limitation of this process is the mechanical properties of the parts obtained. New continuous-fiber FDM printers significantly improve mechanical properties. Another limitation is the repeatability of the process. This paper proposes to explore the feasibility of printing parts in continuous carbon fiber and using this fiber as an indicator thanks to the electrical properties of the carbon fiber. The placement of the fiber in the part is based on the paths of a strain gauge. The results show that the resistivity evolves linearly during the elastic period. The gauge factor (GF) increases when the number of passes in the manufacturing plane is low, but repeatability is impacted. However, no correlation is possible during the plastic deformation of the sample. For an equivalent length of carbon fiber, it is preferable to have a strategy of superimposing layers of carbon fiber rather than a single-plane strategy. The mechanical properties remain equivalent but the variation in the electrical signal is greater when the layers are superimposed.
Parts manufactured by additive manufacturing (AM) are criticized due to the high surface roughness. Roller burnishing is one of the post-processing processes which may be applied for reducing the roughness and asperities on surfaces of 3D printed parts. In this study, innovative zirconium oxide (ZrO2) reinforced acrylonitrile butadiene styrene (ABS) based composites have developed in filament form for 3D printing of roller burnishing rapid tools. The filaments of ABS-ZrO2 were extruded under the range of 230-240 °C of barrel temperature and 4-6 RPM of screw speed under heat treatment as per Taguchi L9 based experimentation. As per the mechanical properties concern of composite filament material, the combination of preheat treatment, 235 °C of barrel temperature, and 6 RPM of screw speed have been noted best setting (Young’s modulus: 886.00 MPa). The filament preparation has been supported with such as x-ray diffraction (XRD), Fourier transforms infrared (FTIR), and microstructural analysis using metallurgical image analysis software (MIAS). A machine learning (ML) approach based on classification and regression trees (CART) has been utilized to predict the tensile peak and break strength. Finally, the 3D printed roller burnishing tool has significantly reduced the surface roughness after burnishing.
3D printing functional parts with known mechanical properties is challenging using variable open source 3D printers. This study investigates the mechanical properties of 3D printed parts using a commercial open-source 3D printer for a wide range of materials. The samples are tested for tensile strength following ASTM D638. The results are presented and conclusions are drawn about the mechanical properties of various fused filament fabrication materials. The study demonstrates that the tensile strength of a 3D printed specimen depends largely on the mass of the specimen, for all materials. Thus, to solve the challenge of unknown print quality on mechanical properties of a 3D printed part a two step process is proposed, which has a reasonably high expectation that a part will have tensile strengths described in this study for a given material. First, the exterior of the print is inspected visually for sub-optimal layers. Then, to determine if there has been under-extrusion in the interior, the mass of the sample is measured. This mass is compared to the theoretical value using densities for the material and the volume of the object. This two step process provides a means to assist low-cost open-source 3D printers expand the range of object production to functional parts.
In this paper, 3D printing as a novel printing process was considered for deposition of polymers on synthetic fabrics to introduce more flexible, resource-efficient and cost effective textile functionalization processes than conventional printing process like screen and inkjet printing. The aim is to develop an integrated or tailored production process for smart and functional textiles which avoid unnecessary use of water, energy, chemicals and minimize the waste to improve ecological footprint and productivity. Adhesion of polymer and nanocomposite layers which were 3D printed directly onto the textile fabrics using fused deposition modelling (FDM) technique was investigated. Different variables which may affect the adhesion properties including 3D printing process parameters, fabric type and filler type incorporated in polymer were considered. A rectangular shape according to the peeling standard was designed as 3D computer-aided design (CAD) to find out the effect of the different variables. The polymers were printed in different series of experimental design: nylon on polyamide 66 (PA66) fabrics, polylactic acid (PLA) on PA66 fabric, PLA on PLA fabric, and finally nanosize carbon black/PLA (CB/PLA) and multi-wall carbon nanotubes/PLA (CNT/PLA) nanocomposites on PLA fabrics. The adhesion forces were quantified using the innovative sample preparing method combining with the peeling standard method. Results showed that different variables of 3D printing process like extruder temperature, platform temperature and printing speed can have significant effect on adhesion force of polymers to fabrics while direct 3D printing. A model was proposed specifically for deposition of a commercial 3D printer Nylon filament on PA66 fabrics. In the following, among the printed polymers, PLA and its composites had high adhesion force to PLA fabrics.
Digital light processing (DLP) is an accurate additive manufacturing (AM) technology suitable for producing micro-parts by photopolymerization. As most AM technologies, anisotropy of parts made by DLP is a key issue to deal with, taking into account that several operational factors modify this characteristic. Design for this technology and photopolymers becomes a challenge because the manufacturing process and post-processing strongly influence the mechanical properties of the part. This paper shows experimental work to demonstrate the particular behavior of parts made using DLP. Being different to any other AM technology, rules for design need to be adapted. Influence of build direction and post-curing process on final mechanical properties and anisotropy are reported and justified based on experimental data and theoretical simulation of bi-material parts formed by fully-cured resin and partially-cured resin. Three photopolymers were tested under different working conditions, concluding that post-curing can, in some cases, correct the anisotropy, mainly depending on the nature of photopolymer.
Today, Additive manufacturing (AM) is a well known technology for making real three dimensional object, with metal or ceramic or plastic or thereby combination, which may be subjected to various applications. Additive bio-manufacturing (ABM) techniques are highly in demand and researches have been going on for making these safer and more versatile. For more utilization and versatility, special attention is required to develop new materials which can help in increasing the service life, bioactivity, cell growth along with the desired mechanical properties. The present paper aims to review some of the most widely used AM techniques for biomedical applications. Special attention has been paid on Fused deposition modeling (FDM) based AM technique as it is economical, environmentally friendly and adaptable to flexible filament material. This review paper will be helpful to the researchers, scientists, manufacturers, etc., working in the field of ABM.
For the first time, nested sub-modeling approach and Finite Element Analysis have been used to analyze the structural mechanical of 3D Printed part, whereas the details of 3D printing patterns included in sub-model. The results present a general tool which can improve the quality of 3D printed parts, which have multidisciplinary application in various fields. It is found that the Maximum Principle stress is highly concentrated at 3D printed layers. For a specific 3D printing pattern, the stress intensity factor has been calculated to have the value of 4. Results have been discussed from theoretical, simulation and experimental observation point of view.
This work investigates the influence of powder size/shape on selective laser sintering (SLS) of a thermoplastic polyurethane (TPU) elastomer. It examines a TPU powder which had been cryogenically milled in two different sizes; coarse powder (D50∼200μm) with rough surfaces in comparison with a fine powder (D50∼63μm) with extremely fine flow additives. It is found that the coarse powder coalesces at lower temperatures and excessively smokes during the SLS processing. In comparison, the fine powder with flow additives is better processable at significantly higher powder bed temperatures, allowing a lower optimum laser energy input which minimizes smoking and degradation of the polymer. In terms of mechanical properties, good coalescence of both powders lead to parts with acceptable shear-punch strengths compared to injection molded parts. However, porosity and degradation from the optimum SLS parameters of the coarse powder drastically reduce the tensile properties to about one-third of the parts made from the fine powders as well as those made by injection molding (IM).
Additive Manufacturing (AM), the relatively young manufacturing technology of layer-based automated fabrication process for making three-dimensional physical objects directly from 3D CAD data set was originally called Rapid Prototyping (RP) when the first commercial process – Stereolitography was entered the market in 1987. This technology is still frequently called Rapid Prototyping. The main objective of research was to determine the impact of sample's structure on the tensile strength of 3D printed samples. Test samples were prepared on a Z Corporation's 3D printer model Z310, with variations of internal geometrical structure. Results of tensile test revealed that the honeycomb structured samples exhibit the highest strength.
In contrast to conventional subtractive manufacturing methods which involve removing material to reach the desired shape, additive manufacturing is the technology of making objects directly from a computer-aided design model by adding a layer of material at a time. In this study, a comprehensive effort was undertaken to represent the strength of a 3D printed object as a function of layer thickness by investigating the correlation between the mechanical properties of parts manufactured out of acrylonitrile butadiene styrene (ABS) using fused deposition modeling and layer thickness and orientation. Furthermore, a case study on a typical support frame is done to generalize the findings of the extensive experimental work done on tensile samples. Finally, fractography was performed on tensile samples via a scanning digital microscope to determine the effects of layer thickness on failure modes. Statistical analyses proved that layer thickness and raster orientation have significant effect on the mechanical properties. Tensile test results showed that samples printed with 0.2 mm layer thickness exhibit higher elastic modulus and ultimate strength compared with 0.4 mm layer thickness. These results have direct influence on decision making and future use of 3D printing and functional load bearing parts.
Nanofilled polymeric matrices have demonstrated remarkable mechanical, electrical, and thermal properties. In this article we review the processing of carbon nanotube, graphene, and clay montmorillonite platelet as potential nanofillers to form nanocomposites. The various functionalization techniques of modifying the nanofillers to enable interaction with polymers are summarized. The importance of filler dispersion in the polymeric matrix is highlighted. Finally, the challenges and future outlook for nanofilled polymeric composites are presented.
Rapid prototyping procedures make it possible to produce relatively complicated geometries based on the computer 3D model of products in relatively short time. This requires that the respective product features have good quality, good mechanical properties, dimensional accuracy and precision. However, the number of available materials that can be used for prototyping is limited and their properties can differ significantly from the properties of the finished product. However, RP parts are not inexpensive and sometimes it is difficult to decide which procedure to use to manufacture them in order to obtain their maximal usability. The Laminated Object Manufacturing (LOM) procedure can be used to produce low cost polymeric products (from poly(vinyl chloride)) that have to meet certain mechanical properties, especially if they are used to perform functional tests. Past studies in LOM procedure have been carried out mainly with paper, and a few on metal. The paper deals with testing the influence of the position of products in the machine working area on the mechanical properties (tensile and flexural properties) of the product.
In Additive Manufacturing (AM), parts are manufactured layer-upon-layer. This strategy affects the mechanical properties of AM parts, since they cannot just be assimilated to those of parts manufactured by traditional methods. The PolyJet AM technology uses UV energy to cure layers of photopolymer that are stacked one on top of the following. The amount of energy that reaches each layer is related to several aspects of the manufacturing procedure, such as jetting head displacement strategy or UV irradiation pattern. This work aims to analyse the relative influence of configuration parameters on the relaxation modulus E(t) of flat parts manufactured using PolyJet technology and orientated on the XY plane. Evolution of material properties with respect to time has been used since parts shall present viscoelastic behaviour. Four factors have been evaluated: part spacing along X axis (Δx) and along the Y axis (Δy), orientation of the part within the tray (φ) and surface quality (Q). Influence of Q has been included since material properties could be modified by UV shielding effect. Experimental results have pointed out that Y-spacing and orientation φ both affect E(t).
Additive Manufacturing (AM) is starting to replace conventional manufacturing processes where complex parts with small lead-time and lot sizes are needed. As conventional test methods are not suitable for AM parts, new standard specimens and test procedures have to be defined. This work undertakes some efforts to progress the design of specimens for mechanical tests. A methodology for tensile tests of AM specimens made from one layer is proposed and verified on an example. It identifies challenges during the design and manufacturing of Fused Layer Modeling single layer specimens.
Advances in additive manufacturing technology have made 3D printing a viable solution for many industries, allowing for the manufacture of designs that could not be made through traditional subtractive methods. Applicability of additive manufacturing in cryogenic applications is hindered, however, by a lack of accurate material properties information. Nylon is available for printing using fused deposition modeling (FDM) and selective laser sintering (SLS). We selected 5 SLS (DuraForm® EX, DuraForm® HST, DuraForm® PA, PA 640-GSL, and PA 840-GSL) and 2 FDM (Nylon 12, ULTEM) nylon variants based on the bulk material properties and printed properties at room temperature. Tensile tests were performed on five samples of each material while immersed in liquid nitrogen at approximately 77 Kelvin. Samples were tested in XY and, where available, Z printing directions to determine influence on material properties. Results show typical SLS and FDM nylon ultimate strength retention at 77 K, when compared to (extruded or molded) nylon ultimate strength.
Insulating materials for use in cryogenic boundary conditions are still limited to a proved selection as Polyamid, Glasfiber reinforced resins, PEEK, Vespel etc. These materials are usually formed to parts by mechanical machining or sometimes by cast methods. Shaping complex geometries in one piece is limited. Innovative 3D printing is now an upcoming revolutionary technology to construct functional parts from a couple of thermoplastic materials as ABS, Nylon and others which possess quite good mechanical stability and allow realizing very complex shapes with very subtle details. Even a wide range of material mixtures is an option and thermal treatments can be used to finish the material structure for higher performance. The use of such materials in cryogenic environment is very attractive but so far poor experience exists. In this paper, first investigations of the thermal conductivity, expansion and mechanical strength are presented for a few selected commercial 3D material samples to evaluate their application prospects in the cryogenic temperature regime.
Polyether ether ketone (PEEK) is introduced as a material for the
additive manufacturing process called fused filament fabrication
(FFF), as opposed to selective laser sintering (SLS)
manufacturing. FFF manufacturing has several advantages over
SLS manufacturing, including lower initial machine purchases
costs, ease of use (spool of filament material vs powder
material), reduced risk of material contamination and/or
degradation, and safety for the users of the equipment. PEEK is
an excellent candidate for FFF due to its low moisture absorption
as opposed to other common FFF materials, such as Acrylonitrile
Butadiene Styrene (ABS).
PEEK has been processed into a filament and samples have been
manufactured using several build orientations and extrusion
paths. The samples were used to conduct tensile, compression,
flexural, and impact testing to determine mechanical strength
characteristics such as yield strength, modulus of elasticity,
ultimate tensile strength and maximum elongation, etc. All tests
were conducted at room temperature. A microscope analysis
was also conducted to show features on the failures surfaces.
The mechanical property results from this study are compared to
other published results using traditional thermo-plastic
manufacturing techniques, such injection molding.
Tensile testing was conducted at three raster orientations, 0°, 90°
and alternating between 0° and 90°. Average ultimate tensile
stresses were determined to be 73 MPa for 0° orientation, and 54
MPa for 90° orientation, with alternating 0°/90° orientations of
66.5 MPa. Compression testing was conducted at two raster
orientations, 0° and alternating between 0° and 90°. Average
ultimate strength for the single orientation direction was 80.9
MPa with the alternating orientations at 72.8 MPa. Flexural
testing was conducted at three raster orientations, 0°, 90° and
alternating between 0° and 90°. Ultimate flexural stress was
determined to be 111.7 MPa for 0°, 79.7 MPa for 90°, and 95.3
MPa for orientations alternating between 0° and 90°. Finally,
impact testing was conducted at three raster orientations, 0°, 90°
and alternating between 0° and 90°. Average impact energy
absorbed was determined to be 17.5 Nm in the 0° orientation, 1.4
Nm in the 90° orientation, and 0.7 Nm for the alternating 0° and
90° orientations.
In this study, a preliminary effort was undertaken to represent the mechanical properties of a 3D printed specimen as a function of layer number, thickness and raster orientation by investigating the correlation between the mechanical properties of parts manufactured out of ABS using Fused Filament Fabrication (FFF) with a commercially available 3D printer, Makerbot Replicator 2x, and the printing parameters, such as layer thickness and raster orientation, were considered. Specimen were printed at raster orientation angles of 0°, 45° and 90°. Layer thickness of 0.2 mm was chosen to print specimens from a single layer to 35 layers. Samples were tested using an MTS Universal Testing Machine with extensometer to determine mechanical strength characteristics such as modulus of elasticity, ultimate tensile strength, maximum force and maximum elongation as the number of layers increased. Results showed that 0° raster orientation yields the highest mechanical properties compared to 45° and 90° at each individual layer. A linear relationship was found between the number of layers and the maximum force for all three orientations, in other words, maximum force required to break specimens linearly increased as the number of layers increased. The results also found the elastic modulus and maximum stress to increase as the number of layers increased up to almost 12 layers. For samples with more than 12 layers, the elastic modulus and maximum stress still increased, but at a much slower rate. These results can help software developers, mechanical designers and engineers reduce manufacturing time, material usage and cost by eliminating unnecessary layers that do not increase the ultimate stress of the material by improving material properties due to the addition of layers.
Additive Manufacturing (AM) received a lot of attention in the last years. Organizations are using AM systems for a range of applications such as prototypes for fitting an assembly, tooling components, patterns for prototype tooling, functional parts and many more. Nearly a third is applied for functional parts [1][2]. Hence, the SL method provides a smoother surface finish than other AMT[3]. Not only is the smoother surface a benefit but the good precision is also a positive feature. The ongoing development of new material systems and applications make them suitable alternatives for conventional series production like injection molding or machined-core fabrication for foundry use. Small to middle series cores for faucets with quantities from around 50,000 pieces produced using AM methods are already a reality [1]. From the economical point of view, the SL is a cheap and fast process in comparison to AM systems. The SL technology used in this work is based on an active mask exposure, the digital light processing (DLP). The term DLP refers to the digital mirror devices which are used for selectively tuning individual mirrors on and off in order to selectively expose a photosensitive resin with visible or ultraviolet light. The resin contains a photoinitiator which triggers radical polymerization when irradiated with light. The polymerization process leads to a solidification of the resin, leading finally to a solid polymer part [4]. A digital Mirror Device (DMD) chip acts as a dynamic mask to expose a defined area on the bottom of a transparent material vat above the optical system. The generated picture enables layer-wise polymerization of the photosensitive resin resulting in a 3-dimensional object. The light source radiates light with a wavelength of 460 nm which means blue visible light. At this wavelength the curing takes place. At the Institute of Materials Science and Technology at the Vienna University of Technology six generations of these Blueprinter machines have been developed and built to date. The largest parts that a Blueprinter can currently generate are 110 x 110 x 80 mm3 with a resolution of 25 x 25 x 25 μm3. The wall thickness can go down to four pixels which means one tenth of a millimetre.
Additive manufacturing (AM) is still underutilized as an industrial process, but is quickly gaining momentum with the development of innovative techniques and materials for various applications. In particular, stereolithography (SLA) is now shifting from rapid prototyping to rapid manufacturing, but is facing challenges in parts performance and printing speed, among others. This review discusses the application of SLA for polymer nanocomposites fabrication to show the technology's potential in increasing the applicability of current SLA‐printed parts. Photopolymerization chemistry, nanocomposite preparation, and applications in various industries are also explained to provide a comprehensive picture of the current and future capabilities of the technique and materials involved.
Purpose
This paper aims to present the methodology and results of the experimental characterization of three-dimensional (3D) printed ABS and polycarbonate (PC) parts utilizing digital image correlation (DIC).
Design/methodology/approach
Tensile and shear characterization of acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) 3D-printed parts was performed to determine the extent of anisotropy present in 3D-printed materials. Specimens were printed with varying raster ([+45/-45], [+30/-60], [+15/-75], and [0/90]) and build orientations (flat, on-edge, and up-right) to determine the directional properties of the materials. Tensile and Isopescu shear specimens were printed and loaded in a universal testing machine utilizing 2D digital image correlation (DIC) to measure strain. The Poisson’s ratio, Young’s modulus, offset yield strength, tensile strength at yield, elongation at break, tensile stress at break, and strain energy density were gathered for each tensile orientation combination. Shear modulus, offset yield strength, and shear strength at yield values were collected for each shear combination.
Findings
Results indicated that raster and build orientation had a negligible effect on the Young’s modulus or Poisson’s ratio in ABS tensile specimens. Shear modulus and shear offset yield strength varied by up to 33% in ABS specimens signifying that tensile properties are not indicative of shear properties. Raster orientation in the flat build samples reveals anisotropic behavior in PC specimens as the moduli and strengths varied by up to 20%. Similar variations were also observed in shear for PC. Changing the build orientation of PC specimens appeared to reveal a similar magnitude of variation in material properties.
Originality/value
This article tests tensile and shear specimens utilizing DIC, which has not been employed previously with 3D-printed specimens. The extensive shear testing conducted in this paper has not been previously attempted, and the results indicate the need for shear testing to understand the 3D-printed material behavior fully.
High shape fixity, shape recovery, and prolonged shape memory cycle life are desirable aspects of 4D printed parts; however, the durability of 4D printed parts is rarely investigated. Here, we demonstrated a photopolymer printable by stereolithography apparatus (SLA) which uses a tBA-co-DEGDA network based on dual-component phase switching mechanism to build parts of complex geometries and exhibit shape memory behavior. The material can achieve a high curing rate and precise printing that are highly desired for SLA process. The mechanical strength of the printed parts is comparable statistically to industrial SMPs and shape memory tests showed excellent shape memory performance with higher durability of > 20 shape memory cycles as compared to current 4D printed parts. This work is believed to enable the use of SLA technology to fabricate responsive components of high performance, which also significantly advances the 3D printing technology for more robust applications.
3D printing is emerging as an enabling technology for a wide range of new applications. From fundamentals point of view, the available materials, fabrication speed, and resolution of 3D printing processes must be considered for each specific application. This review provides a basic understanding of fundamentals of 3D printing processes and the recent development of novel 3D printing materials such as smart materials, ceramic materials, electronic materials, biomaterials and composites. It should be noted that the versatility of 3D printing materials comes from the variety of 3D printing systems, and all the new printers or processes for novel materials have not gone beyond the seven categories defined in ISO/ASTM standard. However, 3D printing should never be seen as a standalone process, it is becoming an integral part of a multi-process system or an integrated process of multiple systems to match the development of novel materials and new requirements of products.
Fully dense PLA blocks were manufactured by 3D-printing, depositing a polymer filament in a single direction via the fusion deposition method (FDM). Specimens were cut from printed blocks using conventional machining and were used to perform tension, compression and fracture experiments along different material directions. The elasto-plastic material response was found to be orthotropic and characterised by a strong tension-compression asymmetry; the material was tougher when loaded in the extrusion direction than in the transverse direction. The response of the unidirectional, 3D-printed material was compared to that of homogeneous injection-moulded PLA, showing that manufacturing by 3D-printing improves toughness; the effects of an annealing thermal cycle on the molecular structure and the mechanical response of the material were assessed.
The weak thermomechanical properties of commercial 3D printing plastics have limited the technology's application mainly to rapid prototyping. In this report, we demonstrate a simple approach that takes advantage of the metastable, temperature-dependent structure of graphene oxide (GO) to enhance the mechanical properties of conventional 3D-printed resins produced by stereolithography (SLA). A commercially available SLA resin was reinforced with minimal amounts of GO nanofillers and thermally annealed at 50 °C and 100 °C for 12 hours. Tensile tests revealed increasing strength and modulus at an annealing temperature of 100 °C, with the highest tensile strength increase recorded at 673.6% (for 1wt% GO). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) also showed increasing thermal stability with increasing annealing temperature. The drastic enhancement in mechanical properties, rarely seen to this degree in 3D printed samples reported in literature, is attributed to the metastable structure of GO, polymer-nanofiller crosslinking via acid-catalyzed esterification and removal of intercalated water, thus improving filler-matrix interaction as evidenced by spectroscopy and microscopy analyses.
Fused deposition modeling (FDM) is a powerful additive manufacturing process, becoming, in the past years, more exciting for the academic and industrial researchers. With the growing number of available additive manufacturing technologies and newer materials, the effect of processing conditions on the material behavior and functionality of manufactured products need to be investigated. This study establishes the relationships between FDM process conditions and time-dependent mechanical properties using definitive screening design. Results from this study will help in a clear understanding and design outcome for the academic and industrial community for real world applications.
Additive manufacturing (AM) has been used in aerospace applications from the beginning. It not only plays a role as a rapid prototyping technology for saving capital and time during the product development period but also brings profound influences on product design, direct part fabrication, assembly, and repair in the aerospace industry. Because of recent developments, AM has rapidly become a strategic technology that will generate revenues throughout the aerospace supply chain. In this chapter, we analyze the characteristics of aerospace components favoring AM, discuss different aerospace applications benefit from different AM processes, and describe the repair applications for aerospace components. Examples of aerospace applications both from commercial and academia areas are also analyzed. Finally, this chapter discusses the challenges of applying AM to the aerospace industry and potential future aerospace applications.
Polyamide 11 (PA11) is widely used in selective laser sintering (SLS), but it has poor thermal, electrical, and flame-retardant properties. This research introduces two types of SLS PA11 nanocomposites: one possesses enhanced thermal and electrical properties and one possesses enhanced thermal and flammability properties. PA11 was twin-screw extruded with multiwall carbon nanotubes and nanographene platelets and was cryogenically ground into SLS powders. SLS processing parameters were optimized to obtain overall material properties. The multiwall carbon nanotubes were effective at increasing the material's electrical conductivity, with minimal losses of mechanical properties. This approach was extended to study an FR SLS polymer. The results indicate that although modified PA11 shows an effectively reduced flammability, it suffers a significant loss in elongation at the break. PA11 with intumescent FR additives toughened by a maleic anhydride-modified elastomer were melt-compounded and injection molded into specimens for property characterizations. The best candidate will be used to fabricate SLS test specimens.
Unmanned aerial vehicles (UAV) are gaining popularity due to their application in military, private and public sector, especially being attractive for fields where human operator is not required. Light-weight UAVs are more desirable as they have better performance in terms of shorter take-off range and longer flight endurance. However, light weight structures with complex inner features are hard to fabricate using conventional manufacturing methods. The ability to print complex inner structures directly without the need of a mould gives additive manufacturing (AM) an edge over conventional manufacturing. Recent development in composite and multi-material printing opens up new possibilities of printing lightweight structures and novel platforms like flapping wings with ease. This paper explores the impact of additive manufacturing on aerodynamics, structures and materials used for UAVs. The review will discuss state-of-the-art AM technologies for UAVs through innovations in materials and structures and their advantages and limitations. The role of additive manufacturing to improve the performance of UAVs through smart material actuators and multi-functional structures will also be discussed.
The use of 3D printing for rapid tooling and manufacturing has promised to produce components with complex geometries according to computer designs. Due to the intrinsically limited mechanical properties and functionalities of printed pure polymer parts, there is a critical need to develop printable polymer composites with high performance. 3D printing offers many advantages in the fabrication of composites, including high precision, cost effective and customized geometry. This article gives an overview on 3D printing techniques of polymer composite materials and the properties and performance of 3D printed composite parts as well as their potential applications in the fields of biomedical, electronics and aerospace engineering. Common 3D printing techniques such as fused deposition modeling, selective laser sintering, inkjet 3D printing, stereolithography, and 3D plotting are introduced. The formation methodology and the performance of particle-, fiber- and nanomaterial-reinforced polymer composites are emphasized. Finally, important limitations are identified to motivate the future research of 3D printing.
The composites industry has a tendency to get caught off-guard by metals as they make progress into more applications. 3D printing is an area where metals have taken the lead, but a number of developing technologies could put composites back on top.
This work points out the role of process induced anisotropy on damage development in 3D printed acrylonitrile butadiene styrene (ABS) polymer subject to severe compression. Blocks of dense ABS are printed using fusion deposition modelling. Severe compression condition are attempted to highlight anisotropy induced by printing under different building orientations. X-ray μ-tomography and finite element computation are used to interpret damage occurring during loading. Results show significant inter-filament debonding that occurs during loading due to lateral expansion. Overall behaviour reveals contrasted damage in the plasticity stage, which depends on printing orientation.
Additive manufacturing (AM) is a class of manufacturing processes where material is deposited in a layer-by-layer fashion to fabricate a three-dimensional part directly from a computer-aided design model. With a current market share of 44%, thermoplastic-based additive manufacturing such as fused deposition modeling (FDM) is a prevailing technology. A key challenge for AM parts (especially for parts made by FDM) in engineering applications is the weak inter-layer adhesion. The lack of bonding between filaments usually results in delamination and mechanical failure. To address this challenge, this study embedded carbon nanotubes into acrylonitrile butadiene styrene (ABS) thermoplastics via a filament extrusion process. The vigorous response of carbon nanotubes to microwave irradiation, leading to the release of a large amount of heat, is used to melt the ABS thermoplastic matrix adjacent to carbon nanotubes within a very short time period. This treatment is found to enhance the inter-layer adhesion without bulk heating to deform the 3D printed parts. Tensile and flexural tests were performed to evaluation the effects of microwave irradiation on mechanical properties of the specimens made by FDM. Scanning electron microscopic (SEM) images were taken to characterize the fracture surfaces of tensile test specimens. The actual carbon nanotube contents in the filaments were measured by conducting thermogravimetric analysis (TGA). The effects of microwave irradiation on the electrical resistivity of the filament were also reported.
Copyright © 2016 by ASME Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
Additive manufacturing (AM), more commonly referred to as 3D printing, has become increasingly popular for rapid prototyping (RP) purposes by hobbyists and academics alike. In recent years AM has transitioned from a purely RP technology to one for final product manufacturing. As the transition from RP to manufacturing becomes an increasingly accepted practice it is imperative to fully understand the properties and characteristics of the materials used in 3D printers. This paper presents the methodology and results of the mechanical characterization of acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) 3D printed parts to determine the extent of anisotropy present in 3D printed materials. Specimens were printed with varying raster ([+45/−45], [+30/−60], [+15/−75], and [0/90]) and build orientations (flat, on-edge, and up-right) to determine the directional properties of the materials. Reduced gage section tensile and Isopescu shear specimens were printed and loaded in a universal testing machine utilizing 2D digital image correlation (DIC) to measure strain. Results indicated that raster and build orientation had a negligible effect on the Young’s modulus or Poisson’s ratio in ABS tensile specimens. Shear modulus and shear yield strength varied by up to 33 % in ABS specimens signifying that tensile properties are not indicative of shear properties. Raster orientation in the flat build samples reveal anisotropic behavior in PC specimens as the moduli and strengths varied by up to 20 %. Similar variations were also observed in shear for PC. Changing the build orientation of PC specimens appeared to reveal a similar magnitude of variation in material properties.
3D printers allow researchers to produce parts and concept models rapidly at low-cost and allow rapid prototyping of many designs from the comfort of their desk. 3D printing technologies have been explored for a wide range of applications including robotics, automobile components, firearms, medicine, space, etc. Owing to lower costs and increased capabilities of 3D printing technologies, unprecedented opportunities in the world of oceanography research are being created. Some examples include 3D printed components being employed in autonomous underwater (or surface) vehicles; 3D printed replicas of marine organisms being used to study biomechanics, hydrodynamics, and locomotion; and 3D printed coral reef replicas being used to restore damaged coral reefs. To the author’s knowledge, currently there is no review covering the different 3D printing technologies applied in oceanography studies. Therefore, this review presents a summary of the different 3D printing technologies that have been used in fundamental studies or real-life applications related to oceanography. The diverse range of 3D printing applications in oceanography covered in this review has been categorized under the following sub-topics: Ecological Monitoring & Sample Collection, Hydrodynamics, Biomechanics & Locomotion, Tracking & Surface Studies, and Tangible Coral Props & Coral Reef Restoration. A detailed overview of the 3D printing technologies referred to within this review has been presented, and categorized under the following four general topics: Material Extrusion, Photopolymerization, Powder Bed Fusion, and Construction Printing. The broad impact of plastics on oceans and the specific impact of 3D printing materials on ocean life are also discussed. It is anticipated that this review will further promote the 3D printing technologies to oceanographers for a better understanding and restoration of fragile marine ecosystems.
A study of the cyclical fatigue behavior of additive manufactured components, fabricated by the fused deposition modeling (FDM) process, is presented. Experimentation was designed to focus on the effect of deposition strategy or specimen mesostructure on tensile fatigue life and effective stiffness. Testing included consideration of unidirectional laminates with parallel plies having fiber orientations ranging from θ = 0° to θ = 90°, and bidirectional laminates with alternating orthogonal plies that form a layering pattern of θ°/(θ - 90°) fiber orientations. Results highlight the orthotropic behavior of FDM components and suggest that tensile performance is improved by aligning fibers of unidirectional laminae more closely with the axis of applied stress. The bidirectional laminae display incrementally improved tensile fatigue performance from what appears to be an offsetting effect associated with alternating orthogonal layers. An empirical model of effective elastic modulus and an analytical model of the accumulated damage state, as defined on the basis of stiffness degradation during cyclical loading, are presented as functions of specimen mesostructure. The actual damage accumulation due to cyclical loading is compared with the model predictions, and the coefficient of determination R² indicates reasonable agreement for each factor combination.
Three dimensional (3D) printing is a technique conventionally used to manufacture prototypes. Commercial desktop 3D printers have become available which produce functional 3D printed parts. The MarkOne by Mark Forged manufactures printed structures reinforced with continuous Carbon, Fiberglass or Kevlar fibers. The aim of this study is to evaluate the elastic properties of the fiber reinforced 3D printed structures and predict elastic properties using an Average Stiffness (VAS) method. Samples evaluated in this study were produced by varying the volume fraction of fibers within the 3D printed structures (4.04, 8.08 and 10.1% respectively). The experimentally determined elastic modulus was found to be 1767.2, 6920.0 and 9001.2 MPa for fiber volume fractions of 4.04, 8.08 and 10.1% respectively. The predicted elastic moduli were found to be 4155.7, 7380.0 and 8992.1 MPa. The model results differed from experiments by 57.5, 6.2 and 0.1% for the 4.04, 8.08 and 10.1% fiber volume fractions. The predictive model allows for the elastic properties of fiber reinforced 3D printed parts. The model presented will allow for designers to predict the elastic properties of fiber reinforced 3D printed parts to be used for functional components which require specific mechanical properties.
Organically modified nanofillers, including nano SiO2, montmorillonite and attapulgite were loaded to stereolithography resin (SLR). The surface of nanofillers were modified using organic modifier of 3-(trimethoxysilyl)propyl methacrylate (γ-MPS) and (1-hexadecyl)dimethyl allyl ammonium chloride (C16-DMAAC), and were characterized by FTIR and small angle XRD analysis. The morphology of nanocomposites were observed by TEM. Viscosity and curing speed of SLR nanocomposites at increasing nanofillers loading were also studied. The mechanical properties of printed samples fabricated by a home-made stereolithography apparatus (SLA) 3D printer were tested. The influence of nanoparticles on the accuracy was measured and discussed. It was found that addition of 5% w/w of nano SiO2 increased the tensile strength and modulus by 20.6% and 65.1% respectively, and the printed accuracy was not significantly influenced. This study opens the way to the application of nanocomposites in the desktop level SLA 3D printing.