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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.

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... However, the prices of feedstock materials are significantly high, necessitating introducing more polymers, such as polypropylene [4]. Considerable research has focused on assessing the processing parameters, as well as the mechanical properties of printed parts to determine the applicability of new polymers in L-PBF [5,6,7,8]. However, limited research has focus on analysing the tensile fracture of printed parts [9]. ...
... Considerable research has focused on assessing the processing parameters, as well as the mechanical properties of printed parts to determine the applicability of new polymers in L-PBF [5,6,7,8]. Different process parameters affect the density and mechanical characteristics of components developed using L-PBF. Some of these factors include energy density/laser power, scan spacing, laser beam speed, and part orientation [8]. ...
... Different process parameters affect the density and mechanical characteristics of components developed using L-PBF. Some of these factors include energy density/laser power, scan spacing, laser beam speed, and part orientation [8]. Other aspects that influence mechanical properties of printed parts include the uniformity of feedstock, evolution of microstructure, refresh rate, layer thickness, and nature of the powder used (virgin or aged powder) [8]. ...
Conference Paper
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The failure edges of polymer laser sintered tensile specimens of two grades of commercial polypropylene powder (Laser PP CP 60 and Laser PP CP 75) were investigated in this study. The tensile test specimens printed using Laser PP CP 60 exhibited ductile fracture with fracture surfaces that were more jagged and fibrous, whereas those printed with Laser PP CP 75 were more brittle. The tensile specimens printed with Laser PP CP 75 powder, exhibited an increase of the ultimate strength up to the second re-use cycle, after which, the magnitude of the ultimate strength started to decrease with powder re-use cycles. This phenomenon can be attributed to the breakage of glass filler material in the Laser PP CP 75 powder, which might have led to a reduction in the packing density of the samples.
... With the technological advancement of AM over the last couple of decades, the quality of AM parts in terms of dimensional accuracy and strength is improving significantly [3]. This has led to the use of AM in real-time industrial applications in automotive, aerospace, electronics, construction, military, and biomedical sectors [4][5][6]. ...
... The automotive sector is facing challenges to develop manufacturing processes suitable to accommodate for shorter product lifecycles, increasing variety due to high levels of customization in case of luxury vehicles, saving time and cost for small and medium-scale production etc. [4,5]. Automotive manufacturing has large volumes of parts with over 1000 vehicles per line per day, where sheet metal forming becomes attractive due to its cost-effectiveness for large volume production. ...
... FDM parts have very large anisotropy in mechanical properties due to various factors such as layer thickness, raster orientation, presence of reinforcements, and different thermal histories within the part. Extrusion forces align the reinforcement fibers along the raster direction, making the part significantly stronger in raster direction compared to the transverse direction [5]. Another important factor contributing to the high anisotropy of FDM parts is the presence of voids or porosity. ...
Article
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3D printed polymer composite materials offer a cost-effective and rapid tooling option for prototyping, and low-cost, low-volume sheet metal forming applications. Due to the high anisotropy in mechanical properties of 3D printed composites, accurate characterization and finite element modeling of the material become paramount for successful design and application of these forming tools. This paper presents experimental characterization of 3D printed fiber–reinforced polymer composite material at various strain rates. A homogenized material model with orthotropic elasticity and the Hill 1948 anisotropic yield criterion were then calibrated based on these experimental data. Finite element simulations of the stamping of high-strength steel sheets using composite tooling were performed, and tool deformation was predicted and compared with experimental measurements. FE simulation results were in good agreement with stamping experiments performed with polymer tooling. It was found that the anisotropy and strain rate sensitivity of 3D printed polymer composites play a significant role in their performance as tooling materials.
... This study aimed to determine the mechanical properties of surgical guides that are commonly used for mini-implant placement after undergoing chemical disinfection and autoclave sterilization. The characterization of different materials from the point of view of their mechanical properties is extremely important to understand their behavior in a clinical situation and to understand how the different procedures that are applied before their clinical use (such as disinfection and sterilization) might affect their clinical performance [4,12,13,[39][40][41][42][43][44][45]. ...
... This can be explained by the differences in the material and printing method and can be clinically translated as the SLA-printed guides having higher strength [8][9][10]. The basic tensile strength and elastic modulus of printed components produced with SLA printers were investigated in several studies [27,40,41]. The results showed some distinctions between the tensile modulus of 3D prints and their base materials. ...
... The results showed some distinctions between the tensile modulus of 3D prints and their base materials. The tensile properties of specimens with edge build orientation are different compared with those of specimens with flat build orientation [41,52,53]. ...
Article
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Three-dimensional printed surgical guides increase the precision of orthodontic mini-implant placement. The purpose of this research was to investigate the effects of disinfection and of two types of autoclave sterilization on the mechanical properties of 3D printed surgical guides obtained via the SLA (stereolithography) and DLP (digital light processing) printing methods. A total of 96 standard specimens (48 SLA and 48 DLP) were printed to analyze the tensile and flexural properties of the materials. A total of 80 surgical guide (40 SLA and 40 DLP) specimens from each printing method were classified into four groups: CG (control group); G1, disinfected with 4% Gigasept (Gigasept Instru AF; Schülke & Mayer Gmbh, Norderstedt, Germany); G2, autoclave-sterilized (121 °C); and G3, autoclave-sterilized (134 °C). Significant differences in the maximum compressive load were determined between the groups comprising the DLP-(p < 0.001) and the SLA- (p < 0.001) printed surgical guides. Groups G2 (p = 0.001) and G3 (p = 0.029) showed significant parameter modifications compared with the CG. Disinfection with 4% Gigasept (Gigasept Instru AF; Schülke & Mayer Gmbh, Norderstedt, Germany) is suitable both for SLA- and DLP-printed surgical guides. Heat sterilization at both 121 °C and 134 °C modified the mechanical properties of the surgical guides.
... Three-dimensional printing is a unique technology that offers a high degree of freedom for customizing practical products in a short time at an acceptable price. In recent years, the improved and reliable 3D printers and 3D scanners custom-made for additive manufacturing technology are becoming an increasingly viable and cost-effective option for high-mix-low-volume manufacturing of customized parts and prototypes [1][2][3]. ...
... The FFF extrusion head operates in the X and Y axes while the platform is lowered in the Z-axis in order to form each new layer. Practically, the process draws the designed model one layer at a time [1][2][3][4][5]. ...
Article
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From a scientific point of view, heat transfer is different in solar furnaces compared with classical ones and the influence of direct concentrated solar radiation on sintered parts needs to be studied in detail to determine the feasibility of solar furnaces in manufacturing small workpieces. This study was performed on cylindrical samples with controlled morphology obtained by a powder metallurgy 3D printing technique. All samples were heated with a heating rate of 120 ± 10 °C/minute, with 0, 1, 2, 3, 4 and 5 min holding times at 900 °C and 930 °C. The morphology of the samples was analyzed microscopically, the microhardness was determined before and after sintering, and the results were correlated with the sintering parameters (temperature, heating rate and holding time). The best results were obtained at 930 °C with 5 min holding time from the microhardness value and microstructure point of view.
... II. MATERIAL STRUCTURE There are a wide range of polymers used for additive manufacturing, with proficiencies well-versed from their molecular construction, with polymers managed in diverse conducts for the individually printing process. During extrusion processes through the nozzle, thermoplastic resin is frequently used for 3D printing where they are liquefied for extrusion followed by toughening after deposition [6]. The Acrylonitrile styrene acrylate material is a substitute to Acrylonitrile butadiene styrene with better exceptional mechanical properties and heat resistance properties, while PLA is an additional common thermoplastic with biocompatibility but a lesser glass conversion temperature [7]. ...
Article
Full-text available
Polymer and biomaterial 3D printing is an innovative technology that can construct any 3D entity by depositing material layer by layer with current research interpreting towards enlarged use in the medical sector. The different materials like concrete, ceramic, metals, and polymers are usually used for 3D printing. With the purpose of making 3D printing sustainable, scholars are working on the use of diverse bio-derived materials for 3D printing. Polymer and biomaterial printing is beneficial in the medical sector because it empowers the 3D printing of affordable functional parts with good properties and proficiencies. In this review, we highlight current research developments for biomaterial and polymer printing using Fused Deposition Modeling (FDM) for the medical sector. Explicitly, the composition, characteristics, and properties of bio-polymers are discussed. Further, the application of bio-polymers in the medical sector like dental implants, drug delivery systems, and safety equipment and polymers containing bio-fillers are discussed too.
... Values of R 2 highlighted a highly linear correlation, which meant that data adjustment followed a suitable Hooke approximation in the proportional zone. Despite the linearity of the elastic region, in general, rubber-like PolyJet materials show the overall non-linear behavior and dependence on mechanical properties of the applied strain rate (viscoelastic) and build orientation as reported in several studies [26,41,72,73]. Finally, we found highly repeatable results across our entire mechanical tests performed driven by small standard deviations and CV% values ≤ 30%. ...
Article
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Present and future anatomical models for biomedical applications will need bio-mimicking three-dimensional (3D)-printed tissues. These would enable, for example, the evaluation of the quality-performance of novel devices at an intermediate step between ex-vivo and in-vivo trials. Nowadays, PolyJet technology produces anatomical models with varying levels of realism and fidelity to replicate organic tissues. These include anatomical presets set with combinations of multiple materials, transitions, and colors that vary in hardness, flexibility, and density. This study aims to mechanically characterize multi-material specimens designed and fabricated to mimic various bio-inspired hierarchical structures targeted to mimic tendons and ligaments. A Stratasys® J750™ 3D Printer was used, combining the Agilus30™ material at different hardness levels in the bio-mimicking configurations. Then, the mechanical properties of these different options were tested to evaluate their behavior under uni-axial tensile tests. Digital Image Correlation (DIC) was used to accurately quantify the specimens' large strains in a non-contact fashion. A difference in the mechanical properties according to pattern type, proposed hardness combinations, and matrix-to-fiber ratio were evidenced. The specimens V, J1, A1, and C were selected as the best for every type of pattern. Specimens V were chosen as the leading combination since they exhibited the best balance of mechanical properties with the higher values of Modulus of elasticity (2.21 ± 0.17 MPa), maximum strain (1.86 ± 0.05 mm/mm), and tensile strength at break (2.11 ± 0.13 MPa). The approach demonstrates the versatility of PolyJet technology that enables core materials to be tailored based on specific needs. These findings will allow the development of more accurate and realistic computational and 3D printed soft tissue anatomical solutions mimicking something much closer to real tissues.
... In terms of mechanical behavior, Polycarbonate specimens were used as the gold standard and its mechanical behavior is preferred for producing corrective insoles [51]. This led to the need to evaluate the mechanical properties related to common materials, obtained with different manufacturing techniques to better match the mechanical behavior of the gold standard material. ...
Article
Full-text available
Background: In clinical practice, specific customization is needed to address foot pathology, which must be disease and patient-specific. To date, the traditional methods for manufacturing custom functional Foot Orthoses (FO) are based on plaster casting and manual manufacturing, hence orthotic therapy depends entirely on the skills and expertise of individual practitioners. This makes the procedures difficult to standardize and replicate, as well as expensive, time-consuming and material-wasting, as well as difficult to standardize and replicate. 3D printing offers new perspectives in the development of patient-specific orthoses, as it permits addressing all the limitations of currently available technologies, but has been so far scarcely explored for the podiatric field, so many aspects remain unmet, especially for what regards customization, which requires the definition of a protocol that entails all stages from patient scanning to manufacturing. Methods: A feasibility study was carried out involving interdisciplinary cooperation between industrial engineers and podiatrists. To that end: (i) For patient-specific data acquisition, 3D scanning of the foot is compared to traditional casting. (ii) a modelling GD workflow is first created to design a process permitting easy creations of customized shapes, enabling the end user (the podiatrist) to interactively customize the orthoses. Then, (iii) a comparison is made between different printing materials, in order to reproduce the same mechanical behavior shown by standard orthoses. To do this, the mechanical properties of standard materials (Polycarbonate sheets), cut and hand-shaped, are compared with four groups of 3D printed samples: poly(ethylene glycol) (PETG), poly(acrylonitrile-butadiene.styrene) (ABS), polycarbonate (PC) and poly(lactic acid) (PLA) obtained by Fused Filament Fabrication (FFF). Results: Differences found between the foot plaster model obtained with the plaster slipper cast in a neutral position and the model of the real foot obtained with 3D scanning in the same position can be ascribed to the non-stationarity of the patient during the acquisition process, and were limited by a locking system with which no substantial differences in the almost entire sole of the foot scan were observed. Conclusions: Using the designed GD workflow, podiatrists with limited CAD skills can easily design and interactively customize foot orthoses to adapt them to the patients' clinical needs. 3D printing enables the complex shape of the orthoses to be reproduced easily and quickly. Compared to Polycarbonate sheets (gold standard), all the printed materials were less deformable and reached lower yield stress for comparable deformation. No modifications in any of the materials as a result of printing process were observed.
... As a method based on forming principle of discrete-addition, additive manufacturing manufacture forms parts by accumulation material layer by layer. Nowadays, metal additive manufacturing technology has been popularized and applied in production [1][2][3]. Using additive manufacturing technology can directly reduce the mold processing cost in the trial production stage of parts; The rational use of additive manufacturing technology can greatly reduce the process difficulty and improve the material utilization for the production of parts with complex internal structures; The high flexibility of additive manufacturing greatly reduces the production cycle of customized parts such as artificial skull [4,5]. ...
Article
Based on the semi-solid forming technology, the semi-solid additive manufacturing platform was built in this study, and the forming process was carried out with Pb-Sn wire as raw material. The results showed that when z-axis moving distance of monolayer stacking is 4.2 mm, extruder head temperature reaches 240 °C and heating plate temperature reaches 160 °C, the microstructure is composed of spherical grains of Pb solid solution with average diameter of 13.4 μm and low melting point Sn phase distributed at the grain boundary, the corresponding overlap surface curvature is 0.429 mm⁻¹; The macro morphology also showed the best characteristics with forming effective degree of 0.869 and forming layer height ratio of 1.004. The mechanical properties of semi-solid additive manufacturing sample with optimized processing parameters were tested, the vertical and horizontal tensile strength of the sample are 44.2 and 47.8 MPa respectively, and the elongation in the vertical direction of sample (29.1 %) is significantly higher than that (20.1 %) in the horizontal direction because of double necking phenomena, this deformation mechanical can be explained by the existence of several bonding areas in gauge segment and soft of bonding areas due to enrich of Sn. Finally, Pb-Sn parts with different shapes were formed. This study provides a basis for the further development of semi-solid additive manufacturing for aluminum.
... In this process, the radiation of UV light leads to the crosslinking of polymeric molecule chains and the solidification of the photosensitive material. The final macroscopic mechanical properties like shear and bulk modulus, or relaxation time are affected by the molecular composition of the resin and the changes in the polymerization process on the micro-scale [27][28][29][30]. ...
Article
Grayscale masked vat photopolymerization (MSLA) 3D printing enables the fabrication of graded structures from a single material, overcoming a major limitation of vat photopolymerization methods. Two main parameters affecting the curing of the resin in vat photopolymerization , and thus the resulting material properties, are the exposure time per layer and the intensity of the ultraviolet light, which can be regulated in terms of the grayscale value of the mask. Here, the concept of grayscale MSLA is extended by combining these two easily adjustable parameters into a single parameter, which we call the grayscale exposure. Then, a parametric visco-hyperelastic constitutive model is formulated for the strain rate-dependent behavior of the resulting material in finite deformations, which depends on the grayscale exposure. Hyperbolic tangent functions are utilized to express the dependency of the material coefficients in terms of grayscale exposure. The advantage of expressing the material model in terms of grayscale exposure is not only the reduction of design parameters from two to one, but also the fact that the printing time can be reduced through the correlation of exposure time and grayscale. Furthermore, the grayscale exposure values are verified through a comparison of different couples of grayscale and exposure time. Finally, the constitutive model is validated against further experimental results, showing a good agreement. In summary, the main contributions of this manuscript are the systematic investigation of the correlation of process parameters with rate-dependent mechanical properties, the unification of light intensity and layer printing time into the grayscale exposure as a single adjustable design parameter, as well as the development of a parametric visco-hyperelastic constitutive model and its experimental identification and verification.
... Transport, medical and sports industries are on the way to integrate the FDM technique to design structural parts, aiming to take advantage of the versatility of the process and looking to achieve the best strength-to-weight ratio. FDM 3D-printing of engineering polymers is able to offer parts with low-scale production, presenting completely adapted solutions for final costumers [18]. ...
Article
This paper presents a procedure for the estimation of the effective thermo-viscoelastic behavior in fiber-reinforced polymer filaments used in high temperature fiber-reinforced additive manufacturing (HT-FRAM). The filament is an amorphous polymer matrix (PEI) reinforced with elastic short glass fibers treated as a single polymer composite (SPC) holding the assumption of thermo-rheologically simple matrix. Effective thermo-viscoelastic behavior is obtained by implementing mean-field homogenization schemes through the extension of the correspondence principle to continuous variations of temperature by using the time–temperature superposition principle and the internal time technique. The state of the fibers in the composite is described through the use of probability distribution functions. Explicit forms of the effective properties are obtained from an identification step, ensuring the same mathematical structure as the matrix behavior. The benchmark simulations are predictions of residual stress resulting from the cooling of the representative elementary volumes (REVs) characterizing the composite filament. The computation of the averaged stress in the benchmarking examples is achieved by solving numerically the stress–strain problem via the internal variables’ framework. Reference solutions are obtained from Fast Fourier Transform based full-field homogenization simulations. A comparative analysis is performed, showing the reliability of the proposed homogenization procedure to predict residual stress against extensive computations of the macroscopic behavior of a given microstructure.
... Additive manufacturing, also known as 3D printing, is gaining increasing interest from academic institutions as well as from industry [1][2][3]. Selective laser sintering (SLS) is an additive manufacturing process in which a build area is successively coated with plastic powder. The applied powder particles are spatially resolved and fused homogeneously through the energy input of a laser [4][5][6]. ...
Article
Full-text available
The successful use of components produced by selective laser sintering as a rapid manufacturing process requires a comprehensive understanding of the material. In this study, the effect of specimen build orientation on mechanical properties of selective laser-sintered polyamide 12 was investigated in detail. Samples were printed with an orientation of 0°, 15°, 45°, and 90° to the build platform. In addition to quasi-static tensile tests, creep tests under different loads (5 MPa, 10 MPa, 15 MPa, and 20 MPa) and for different times (10 h and 1000 h) with and without relaxation were performed. Creep behavior was analyzed using the Burgers model. Therefore, the elastic strain, the relaxant strain, the viscous strain, and the total deformation were determined. Results show that the build orientation has no significant influence on the long-term creep behavior, at small stresses. Short-term creep and relaxation tests show that the elastic and viscous strain are only slightly influenced by the build orientation. However, the viscoelastic strain is affected by the build orientation. Furthermore, the deformations resulting from creep and relaxation have no significant influence on the mechanical behavior as shown by tensile tests.
... Additive manufacturing (AM) is a production process that is growing day by day in use [1,2] for different kinds of applications. It consists of building objects with complex geometries without high burdens by depositing layers of material. ...
Article
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This experimental study investigates the effects of process parameters for 3D printing polylactic acid (PLA) samples on both the mechanical properties obtained and the energy consumption in the fused deposition modelling (FDM) process. The explained experimental activities provide an in-depth evaluation of all the strategies adopted in different temperatures and scan speed strategies. The results, extracted in tensile strength, ultrasonic inspection (UT), and specific energy consumption (SEC), highlight the printing parameters that mainly affect the mechanical characteristics of the final workpieces and the energy consumption to find an appropriate energy-saving energy strategy for the PLA additive manufacturing process. The results indicate a more excellent uniformity of the molded material, reducing the printing time and total energy consumption at high speeds (V = 110 mm/s) and one level of temperature (T = 215 °C). A new efficiency index has been introduced to release guidelines to pursue the best setup compromise.
... This layer-by-layer process enables a fast and cheap design cycle for the preparation of personalized medication [1]. The term 3D printing was coined as an umbrella term and encompasses a number of processes, and in many reviews the main types were described in detail [2][3][4][5]. Three-dimensional printing gave the means to the manufacture of a high-quality product within minutes in an easy manufacturing cycle. This on-demand manufacturing was time and material saving. ...
Article
Full-text available
Since the appearance of the 3D printing in the 1980s it has revolutionized many research fields including the pharmaceutical industry. The main goal is to manufacture complex, personalized products in a low-cost manufacturing process on-demand. In the last few decades, 3D printing has attracted the attention of numerous research groups for the manufacturing of different drug delivery systems. Since the 2015 approval of the first 3D-printed drug product, the number of publications has multiplied. In our review, we focused on summarizing the evolution of the produced drug delivery systems in the last 20 years and especially in the last 5 years. The drug delivery systems are sub-grouped into tablets, capsules, orodispersible films, implants, transdermal delivery systems, microneedles, vaginal drug delivery systems, and micro- and nanoscale dosage forms. Our classification may provide guidance for researchers to more easily examine the publications and to find further research directions.
... In contrast to conventional subtractive manufacturing, layers of materials are added to form the desired object with the help of energy sources such as laser, electron beam, and arc. The two most common materials utilized by industrial 3D printing service providers are polymers (51%) and metals (19.8%) (Dizon et al., 2018). Bioprinting, on the contrary, uses living cells, molecules, biomaterials, extracellular matrices, etc. as raw materials to produce complex living and non-living biological products and structures. ...
Article
Full-text available
Additive manufacturing (AM) offers the advantage of producing complex parts more efficiently and in a lesser production cycle time as compared to conventional subtractive manufacturing processes. It also provides higher flexibility for diverse applications by facilitating the use of a variety of materials and different processing technologies. With the exceptional growth of computing capability, researchers are extensively using machine learning (ML) techniques to control the performance of every phase of AM processes, such as design, process parameters modeling, process monitoring and control, quality inspection, and validation. Also, ML methods have made it possible to develop cybermanufacturing for AM systems and thus revolutionized Industry 4.0. This paper presents the state-of-the-art applications of ML in solving numerous problems related to AM processes. We give an overview of the research trends in this domain through a systematic literature review of relevant journal articles and conference papers. We summarize recent development and existing challenges to point out the direction of future research scope. This paper can provide AM researchers and practitioners with the latest information consequential for further development.
... Of all the AM techniques, Selective Laser Sintering (SLS) stands out because it allows the manufacture of parts from a wide family of materials including polymers, metals, and various types of composite materials. Within the field of polymeric materials, polyamide 12 (PA12) prevails as it is ideal for this technique due to the large separation between melting and crystallization temperatures, low melt viscosity and high surface tension [1][2][3][4][5][6]. In addition, it is a light thermoplastic with good impact resistance, excellent mechanical properties and high resistance to fatigue, coupled with a low cost. ...
Article
Full-text available
For the first time, the Failure Assessment Diagrams of Polyamide 12, PA12, processed via a conventional technique as injection moulding, IM, and an additive manufacturing technique as Selective Laser Sintering, SLS, were determined via Finite Element Analysis (FEA) using a stress-strain equation more appropriate to describe the mechanical behaviour of thermoplastics. These diagrams were compared with those computed from the options of the BS 7910 standard applied for metals. The diagrams of SLS PA12 were clearly above that of IM PA12, presenting almost constant fracture ratio values for all the load ratios. This indicates the brittle behaviour, with small deviation from linearity, of SLS PA12 in comparison with IM PA12 which exhibited plasticity effects. This trend was supported by the mechanical response shown by PA12 manufactured by the different processing techniques. On the other hand, the diagrams obtained via FEA showed significant differences with the options of the BS 7910 standard, employed for the determination of the failure diagrams in metals, particularly when a Ramberg-Osgood model is used to describe the mechanical behaviour.
... Additive Manufacturing (AM) as 3D printing forms a three-dimensional object by process of layering extruded material, most commonly polymer filament materials (7,8). The illicit use of AM print technology has been adapted to use a fusion of materials, such as metal components and factory firearms parts to produce functional firearms. ...
Technical Report
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Firearm regulations do not constrain the use of 3D printing technology to produce or contribute to the design and construction of illicit firearms and firearm components. Nor do illicit manufacturers consider the longevity or build quality of the items they produce in the same sense that commercial manufacturers do. The methodology of the firearm trafficker based upon my own experiences are simple and easy to understand, 'go with guns and designs which give the best profit for the least effort and risk'. This is accomplished by combining and exploiting the existing technologies of 3D printing in ways which may be difficult for police agencies to trace, using information which is shared in firearm and 3D printing blogs, e-journals, and businesses promoting the use of 3D printing. Heemsbergen states (1), “It [3D printing] is an innovative and interactive social practice of learning, sharing, and economy”. The prolific sharing of information designs and data files relating to the 3D printing of firearm components and accessories is a commonly observed practice on firearm blog sites. Barton (2) states that as mainstream social media platforms, such as Reddit, Twitter and YouTube ban or restrict the sharing of plans for 3D-printed guns, new websites and chat servers (which can be potentially encrypted) are created to continue the distribution and development of 3D firearm design files. This study is divided into four areas that are intended to explore the current state of 3D-print technology as it applies to illicit firearm manufacturing; 1. Develop an understanding of 3D print technology and its adaption and use within illicit firearms manufacturing. 2. Examine national and international trends involving the licit and illicit use of 3D print technology in firearms manufacturing. 3. Determine and discuss current legislative aspects of licit and illicit production of 3D print technology in firearms manufacturing. 4. Determine and discuss possible future methodologies of organised crime groups utilising 3D print technology to facilitate firearm trafficking and illicit manufacture to evade detection and prosecution.
... Moreover, the FFF technique is a complex process with a large number of parameters influencing product quality and material properties, and the effects of combined parameters is often difficult to assess (Chac on et al., 2017;Song et al., 2017;Zaldivar et al., 2017;Dizon et al., 2018;Braconnier et al., 2020). The previous findings have revealed that the analysis and identification of the process parameters controlling the 3D printing stage of the PDS process are crucial for the stability of this step, and for the mechanical and geometric performance of the green and sintered parts. ...
Article
Purpose The extrusion-based additive manufacturing method followed by debinding and sintering steps can produce metal parts efficiently at a relatively low cost and material wastage. In this study, 316L stainless-steel metal filled filaments were used to print metal parts using the extrusion-based fused filament fabrication (FFF) approach. The purpose of this study is to assess the effects of common FFF printing parameters on the geometric and mechanical performance of FFF manufactured 316L stainless-steel components. Design/methodology/approach The microstructural characteristics of the metal filled filament, three-dimensional (3D) printed green parts and final sintered parts were analysed. In addition, the dimensional accuracy of the green parts was evaluated, as well as the hardness, tensile properties, relative density, part shrinkage and the porosity of the sintered samples. Moreover, surface quality in terms of surface roughness after sintering was assessed. Predictive models based on artificial neural networks (ANNs) were used for characterizing dimensional accuracy, shrinkage, surface roughness and density. Additionally, the response surface method based on ANNs was applied to represent the behaviour of these parameters and to identify the optimum 3D printing conditions. Findings The effects of the FFF process parameters such as build orientation and nozzle diameter were significant. The pore distribution was strongly linked to the build orientation and printing strategy. Furthermore, porosity decreased with increased nozzle diameter, which increased mechanical performance. In contrast, lower nozzle diameters achieved lower roughness values and average deviations. Thus, it should be noted that the modification of process parameters to achieve greater geometrical accuracy weakened mechanical performance. Originality/value Near-dense 316L austenitic stainless-steel components using FFF technology were successfully manufactured. This study provides print guidelines and further information regarding the impact of FFF process parameters on the mechanical, microstructural and geometric performance of 3D printed 316L components.
... Basic principles of additive manufacturing(Dizon et al., 2018) ...
Article
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Fused deposition modelling (FDM) and digital light projection (DLP) technologies have been used for three-dimensional (3D) printing of tensile and tribology test specimens. Several print parameters were examined during the process of utilised methods. The performance of the two employed 3D printers in the present work was evaluated according to the production speed, materials used, properties of the printed pieces, and geometrical and economical aspects. These assessed sides were based on the observations meanwhile the experiment. Further, the operation procedures, as well as the options of print settings of both methods, have also been detailed. Lastly, all important considerations of the tested methods have been compared.
... While FDM is an easily understood and adopted technique, its main flaw arises from significant anisotropy in finished prints. Although this nonuniformity in properties often leads to large part-to-part and inter part variations, [11] still many commodity polymer filaments including acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), polyamide (e.g., Nylon), polycarbonate (PC), thermoplastic polyurethane (TPU), and polyethylene terephthalate (PET) and its copolymers, can be printed with good dimensional fidelity via FDM. ...
... If we only want to differentiate the processes according to the used raw material, there are 3D printing processes for plastics (FDM, SLS, SLA), for metals (DMLS), for ceramics, for biomaterials etc [1]. The aim of all these processes is to use the advantages provided by the 3D printing e.g., the possibility of implementing complex geometries and the reduction of waste [2]. By the expansion of 3D printing, there is a user demand not only for newer and newer 3D printing processes but for printing materials for the existing processes that are as perfect as possible, and which can meet as many expectations as possible [3]. ...
Article
Full-text available
The aim of this study is to investigate the effect of different additives on the average impact strength and on its standard deviation of the in FDM 3D printing widely used polylactic acid (PLA) by using UNI EN ISO 180 unnotched specimens. During the study, PLA based printing materials were investigated containing different types of additives. All specimens were produced by using the same printing parameters to prevent their impact strength modifier effect. The purpose of the research was to determine the extent to which the value of average impact strength, and its standard deviation can be influence using different additives. In the study it plays a key role to find out whether an additive can be used to optimize the researched mechanical property or not. Furthermore, to prove that there is a great, hidden potential in development of printing materials with different additives.
... Finally, some methods and algorithms used in the robotic arm are described. [20], also known as Additive Manufacturing (AM), is already being adopted for rapid prototyping and manufacturing. Recently, cheaper and faster AM techniques have been developed for high-quality printing. ...
Article
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The evolution of information technology and the great advances in artificial intelligence are leading to a level of automation that has never been reached before. A large part of this level of automation is due to the use of robotics, which in turn ends up both hindering and accelerating the process of Industry 4.0. Industry 4.0 is driven by innovative technologies that have an effect on production systems and business models. Although technologies are the driving motors of production within Industry 4.0, many production systems require collaboration between robotics and humans, and safety is required for both parties. Given the need for robots to collaborate with humans simultaneously or in parallel, a new generation of robots, called cobots, “Collaborative Robots”, are gaining prominence to face these challenges. With cobots, it is possible to overcome security barriers and envisage working safely side-by-side with humans. This paper presents the development and testing of a low-cost, within standards, 6-axis collaborative robot that can be used for educational purposes in different task-specific applications. The development of this collaborative robot involves the design and 3D printing of the structure (connections and parts), sizing and selection of circuits and/or electronic components, programming, and control. Furthermore, this study considers the development of a user interface application with the robotic arm. Thus, the application of technological solutions, as well as of the scientific and educational approaches used in the development of cobots can foster the wide implementation of Industry 4.0.
... With the different AM technologies, printing parameters and considerations, test standards are crucial to guide mechanical tests in any application. To set a foundation to make the products more reproducible and reliable, test standards need to be in place [28]. ...
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The manufacturing landscape is ever-changing, and one of the most significant driving forces is the emergence of additive manufacturing (AM), which enables cost-effective and small-scale production towards sustainability. To better align AM with manufacturing in suitable applications, this study proposes a business model in terms of the cost pattern and scaling production supported by three key concepts: standardisation, localisation and collaboration. The ambiguity of the cost calculation is one of the key factors slowing down AM progress, and a lack of a cost pattern affects decision-making when applying AM to appropriate applications. The business model in this study is focused on applying the data collected from previous research, the collection-recycling-manufacturing (CRM) model, to discover the implications of AM processes on the road to sustainable manufacturing. The novel business model envisions the nature of AM characteristics and their linkages to cost patterns, so AM applications can be integrated into a cost-effective process. This study contributes qualitative analysis to the cost patterns’ integration. Through this integration, the business model mediates the gap between technologies and applications via the formulas of cost patterns, so AM can perform its appropriate role in the industry mainstream. The cost modelling proposed in this study derives generic formulas via the unit cost of tooling, moulding, machine, materials, design, miscellaneous cost and the batch size. The business model applies the “divide-and-conquer” concept, convergence effect and data analysis to support quantitative analysis. The model can calculate the total cost per unit, and its accuracy is close to 100%. Through the novelty of this model, AM and conventional manufacturing (CM) cost benchmarking and decision support functions are enabled to aid in stakeholder decision-making. Eventually, appropriate AM technologies and processes can synchronise with localisation, standardisation and collaboration and, ultimately, the impact of AM towards sustainable manufacturing.
... However, the formation of various defects, such as microcracks (5-20 μm) even large interlayer cracks (over 100 μm), due to the considerable brittleness of ceramic materials prepared through AM that is similar to or higher than that of their traditionally cast counterparts causes certain technical problems that require attention such as obtaining samples with less cracks to improve the high-T mechanical properties [5][6][7][8]. The formation of the defects strongly depends on the quality of the ceramic composite, sintering conditions, printing direction, and type of the AM technique [9][10][11][12][13][14][15][16][17][18][19]. Bae et al. [10] prepared ceramic samples with 60 vol % silicon through stereolithography 3D printing (SLA-3DP). ...
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Ceramic cores are applied in electronics, aerospace, medicine, military, automotive, and other fields. However, the effects of the build direction, along with the shrinkage of the green body and thermal stress, on the mechanical properties of 3D ceramic cores have not been elucidated. To reveal the optimum conditions for crack resistance in a high-solid-loading ceramic core, a silicon-based ceramic core with a solid content of 60 vol% was fabricated through stereolithography 3D printing and analyzed in terms of its microstructure-level crack initiation and propagation. The green bodies were initially 3D printed in different build directions (length-directed, width-directed, and height-directed) and then sintered at different temperatures (1100 °C-1250 °C). Higher sintering temperatures generally produced more cracks, and the synergistic effects of the sintering temperature and build direction induced crack initiation and propagation. The width-directed sample sintered at 1200 °C, in particular, exhibited effectively controlled crack growth without sacrificing strength.
... El método de fabricación de las probetas se realizó por modelado por deposición fundida. Inicialmente se realizó un diseño asistido por computador (CAD) como el mostrado en la (Fig 1), con la geometría de la probeta según las condiciones de la norma ASTM 638 -10 para ensayos de tracción de polímeros, como en el estudio realizado por J. R. C. Dizon et al. (Dizon et al., 2018) Tabla 1 El proceso de fabricación se realizó con la ayuda de una impresora MakerBot Replicator Z-8, apoyado con el CAD y la configuración de los parámetros de deposición para el material PLA. ...
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El modelado por deposición fundida representa un avance significativo comparado con otros procesos de producción, debido a la reducción en el tiempo de fabricación de piezas con geometrías complejas. Sin embargo, las propiedades mecánicas del material se ven afectadas a causa de la dirección de deposición, influyendo en el funcionamiento de la pieza en servicio. Por tanto, en la siguiente investigación se analizó las propiedades mecánicas a tracción del poliácido láctico (PLA), en diferentes ángulos de impresión. Se evidencio un comportamiento de carácter anisotrópico, en el cual, la mejor conducta mecánica se mostraba cuando los hilos están orientados en la misma dirección de la fuerza. En consecuencia, se empleó un análisis microscopia electrónica de barrido, donde se detectó una buena adherencia entre las áreas de los filamentos fundidos y una conducta frágil propia de un material elástico lineal. Por último, se realizó un estudio comparativo entre un modelo de elementos finitos y los resultados experimentales, donde se aprecia un comportamiento mecánico similar al obtenido de manera experimental.
... The problem during the processing of the natural filler in the polymer matrix is in-homogeneity of filler dispersion in the polymer matrix, 11 porosity, 12 void formation, 13 and varying fiber diameter. 14 So, the dispersion of natural fillers can be carefully studied before extruding the filaments from the extruder. There are a limited number of studies on the development of natural filler reinforced thermoplastic composites using FDM processes. ...
Article
In the fused deposition modelling technique, various type of thermoplastic is printed layer by layer. Among those biopolymers, Poly Lactic Acid occupies a massive space due to their excellent biodegradability. The present work concentrates on using almond shell particles as potential reinforcement in making Poly Lactic Acid (PLA) filaments by a filament extrusion process using a double screw extruder. The extruded filaments of 1.75 ± 0.5 mm diameter is used to make PLA/almond shell composite. This study distillates the effective process parameters for the 3D printing of PLA/almond shell composite and its compressive strength were evaluated. Design of Experiments is followed for the optimization process. The experiment was conducted by varying the five factors (infill pattern, infill density, printing orientation, printing temperature, and printing speed) and three levels. L27 orthogonal array is developed for the experimental procedure, and Taguchi optimization technique is employed for the optimization process for obtaining maximum compressive strength for the produced PLA/almond shell composite. The experimental results show that the infill density and printing orientation have a higher impact than the other printing process parameters with respect to the compressive properties. The mathematical models are developed from the optimization results for the compressive strength analysis of the PLA/almond shell composites. Based on the regression analysis results, the proposed mathematical model has an error percentage of 3.70% and has a good fit with the experimental results. Fractured samples clearly show that the higher infill density of PLA/almond shell samples doesn’t undergo premature buckling failure under the compressive loading.
... On the contrary, faster degradation, which may result in lower mechanical strength over time, is ideal for tissue regeneration, as the persistence of biomaterials implanted in the host tissue may trigger physical impairment [187]. Furthermore, the fatigue behaviour of 3D-printed polymeric materials is also of great importance for medical devices [188,189]. Therefore, the choice of materials and their combinations to obtain properties suitable for targeted medical devices is challenging. ...
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Additive manufacturing (AM, also known as 3D printing) is an advanced manufacturing technique that has enabled progress in the design and fabrication of customised or patient-specific (meta-)biomaterials and biomedical devices (e.g., implants, prosthetics, and orthotics) with complex internal microstructures and tuneable properties. In the past few decades, several design guidelines have been proposed for creating porous lattice structures, particularly for biomedical applications. Meanwhile, the capabilities of AM to fabricate a wide range of biomaterials, including metals and their alloys, polymers, and ceramics, have been exploited, offering unprecedented benefits to medical professionals and patients alike. In this review article, we provide an overview of the design principles that have been developed and used for the AM of biomaterials as well as those dealing with three major categories of biomaterials, i.e., metals (and their alloys), polymers, and ceramics. The design strategies can be categorised as: library-based design, topology optimisation, bio-inspired design, and meta-biomaterials. Recent developments related to the biomedical applications and fabrication methods of AM aimed at enhancing the quality of final 3D-printed biomaterials and improving their physical, mechanical, and biological characteristics are also highlighted. Finally, examples of 3D-printed biomaterials with tuned properties and functionalities are presented.
... They found that the FDM parts are sensitive to the raster angle, ambient temperature, and defects or voids inside the part. A previous study [8] examined the effects of different layer thickness, raster angle, and infill factors via a tensile test. Chaudhari et al. [9] described how to improve the surface roughness of the parts by using different post-processing methods and varying technological parameters. ...
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One of the advantage of additive manufacturing technologies is the possibility to produce hollow section products, which are lighter, cheaper, faster to create and still they can have the required mechanical properties. Most of the times a 3D printed part's most important feature is the freedom of shape, and by setting the appropriate infill we can ensure the proper resilience as well. In this paper the different infill patterns and volume related percentages are compared by using the commercial Fused Deposition Modelling (FDM) technology. For the investigation non-standardized bending test were made with two loading orientation. From the results, the relation between the mass of the product and manufacturing time can be stated clearly, the pattern and percentage, as well as the decrease of the resilience in case the use of hollow areas in products.
Chapter
A biomaterial is basically a substance, whether natural or manmade, that constitutes an entire or a portion of a living structure or biomedical tool that executes, performs and enhances a natural feature, which can be used for a medical application and modified for it. Biomaterials have a benign role, including to be used for a heart regulator, which can be bioactive, similar to hydroxyapatite covered hip implants, designed for a much more active purpose. In surgery, dental applications and medicine delivery, biomaterials are still being used every day (Isa et al. 2000). The synthetic or natural materials such as ceramic, metals, polymerics and their composite materials can efficiently integrate into the body and are known as biomaterials, being biocompatible with living tissues (Ozkizilcik and Tuzlakoglu 2014). Furthermore, biomaterials are bioactive materials, while the biomimetic materials and biodegradable materials are biologically inactive materials (Li et al. 2007). The materials which interact with body parts and body fluids are important in hand bones, tendons, nerves, heart valves, blood vessel prosthesis and cochlear replacements (Cicco et al. 2015).
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Many people for different reasons end up wearing glasses to correct their vision. From time immemorial, there has been an unquestionable ability to associate people with glasses. Designing the glasses according to the physiognomy of each person opens a new path for a completely new optical experience. The frames are designed to fit perfectly on the face, are comfortable on the nose, and are positioned at an optimal distance from the cheeks and eyelashes. Three-dimensional printing technology offers the possibility to customize any form of glasses at a low cost with average quality. In this type of technology, the printer receives a digitized model of the spectacle frame (usually in STL file format) that must meet the parameters related to the wearer’s anatomy. Therefore, this paper presents an innovative process, an optical method used to scan the wearer’s face to design a parameterized design of the spectacle frames. The procedure has a measurement phase for quantifying the anatomical features of the wearer’s face, a para-metric design phase of the glasses for adjusting the design parameters according to the anatomical characteristics, and a manufacturing phase in which the custom eyeglass frame will be manufactured using 3D printing technology. The aim of this study was to create an innovative process that could be tested as an educational 3D printing system that could be used by undergraduate students (studying under an optometry program), a process that would begin at optometric prescription stage and can be used in the educational laboratory of the Department of Mechatronics and Precision Mechanics from the Politehnica University of Bucharest. Using this method we obtained a custom spectacle frame that can be prototyped using 3D printing. The 3D-printed polylactic acid (PLA) frames are lightweight, flexible, durable, and the innovative photogrammetry process gives designers the ability to create custom designs that cannot be created with traditional manufacturing techniques.
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High-value recycling and reuse of plastic products is very important to solve global plastic pollution in the era of green development and low-carbon economy. Giving that the mainstream of processing plastic waste is still direct mechanical recycling, the unexpected degradation on mechanical properties betrays the intention to recycle plastic waste. Here, based on the temperature sensitivity of interfacial diffusion and orientation retention, we proposed an innovative protocol of recycling biaxially oriented polypropylene (BOPP) film waste in high value and efficient manner. Specially, a lamellar assembly of the biaxially-oriented film wastes was constructed layer by layer and then compressed into a sheet near the melting temperature. The temperature effects on interfacial fusion and orientation retention were investigated comprehensively. When the welding temperature approached the end melting temperature, the low-temperature laminated processing technology not only enabled strong interfacial adhesion, but also retained most of intrinsic orientation structure, conferring the as-prepared sheet with unprecedented combination of strength and toughness, as evidenced by a dramatic increase in ∼200% of mechanical strength and ∼650% of toughness to that of mechanically-recycled convention polypropylene (PP) products without orientation. The enhancement mechanism, in essence, stemmed from high strength endowed with orientation order and the laminar structure with strong ability to inhibit the crack propagation. Finally, supercritical CO2 foaming technology was utilized to transform the high-performance fused PP sample into more valuable lightweight and rigid foam. This simple, scalable, economical and highly effective method without any interfacial additives is easily applied to the other biaxially-oriented films and sets a good example for the recycling application of biaxially-oriented film wastes to achieve the goal of green and low-carbon life.
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Additive manufacturing techniques facilitate fabrication of polymeric lattice structures comprising complex cell architectures, via the ability to fabricate component struts at specified angles. However, the inherent layer-wise fabrication process, especially for Fused Deposition Modelling (FDM), introduces angle-dependent properties depending on the orientation with respect to the printing bed. This results in lattices displaying different mechanical responses, depending on the direction of loading. The present study examines how the static and dynamic tensile material properties of cell strut material are influenced by the angle of printing. Specimens printed at various angles were subjected to quasi-static tensile loading, as well as dynamic extension using a tensile split Hopkinson bar device. It was found that the degree of rate-sensitivity depends on the printing angle. Octet and Hybrid Structure (HS) lattices were also fabricated and subjected to quasi-static and impact compression along the printing direction and transverse to it. The results show that the load-deformation responses and lattice crushing patterns differ significantly. Finite element models, incorporating both printing angle and rate dependent strut material and failure properties, were established, to analyse the deformation with respect to loading direction, at both lattice sample and cell-component levels.
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The effect that the infill orientation angle has on the strain-rate dependence of the yield stress for material extrusion additive manufactured (ME-AM) PolyLactic Acid (PLA) material was investigated. Symmetric angle-ply stacking sequences were used to produce ME-AM tensile test samples. Measured yield stresses were compensated for the voided structure, typical of ME-AM components. Furthermore, molecular orientation and stretch was macroscopically assessed by a thermal shrinkage procedure. Additionally, hot-press compression molded (CM) samples were manufactured and mechanically characterized in uniaxial tensile and compression in order to determine the material’s isotropic bulk properties. Initial model parameters for the Ree-Eyring modification of the Eyring flow rule were determined using CM data. According to SEM fractography, all samples showed microscopically brittle fracture behavior. Notwithstanding, contrary to CM samples, ME-AM specimens showed macroscopically ductile stress–strain behavior and a transition from a regime with only a primary α-deformation process, at low strain rates, to a regime with 2 deformation processes (α+β), at high strain rates. These effects are an influence of the processing step and are attributed to the molecular orientation and stretch of the polymer chains, provoking anisotropic mechanical properties. As a consequence, a deformation-induced change of the Eyring rate constants is needed to adequately describe the strain-rate dependence of the ME-AM yield stress behavior, leaving the initial activation volumes unchanged. Taking this deformation-dependence of the rate constants into account, yield stresses as a function of infill orientation angle can be appropriately predicted.
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Tailoring the properties of high-performance polymers through reinforcing will bring multifunctionality and expand their use in additive manufacturing (AM). However, machine and material-based challenges exist, eventually resulting in low-quality end products. When expensive polymers are considered, it is still challenging to tailor their properties and print them for high-quality multifunctional structures. Here, polymer composites of polyetherimide (PEI) and carbon nanotubes (CNTs) with varying CNT weight fractions are produced in filament form by melt-processing. Neat PEI, 1 wt% and 3 wt% CNTs/PEI are additively manufactured in two different raster orientations (Rectilinear and Concentric), and two most proposed testing geometries, ASTM D638 and D3039. Through effective melt-processing, CNT-reinforced PEI filaments were achieved, printing parameters and testing protocols were discussed. As a result, ASTM D3039 showed superior coherence with filaments’ mechanical properties. Moreover, based on failure modes, ASTM D3039 provided better compatibility to AM, owing to its simple rectangular form yielding well-adhered layers.
Article
The reductions in manufacturing cost and process complexity of flexible sensors are of great significance in popularizing their applications. In present work, a Graphene UV-Cured Direct Electronic (GUDE) process based on photo-curing additive manufacturing technology is proposed and used to fabricate flexible electrode components of wearable respiratory sensors with excellent electrical responses. The method enables one to directly print the conductive structures without the need for cumbersome preparation and complex equipment. Compared with screen printing and microfabrication process that involve the mask preparation, the GUDE process can rapidly produce electrode patterns of any shape, thereby shortening the molding process and time cost of flexible electrodes. Moreover, GUDE process is additive manufacturing process, which saves the cost of raw materials. To verify the feasibility and application of the GUDE technology, a flexible humidity-sensing electronic device is fabricated. The humidity-sensing electronic device has a rapid response and recovery time of 0.27 s and 0.34 s, respectively, and a linear range in relative humidity variation between 39.3% and 88.3%. It can be perfectly attached to skin/surface where humidity needs to be monitored, and then be used in scenarios such as detection of body signals like respiration, disease diagnosis, monitoring of exercise status and industrial humidity/air flow, etc. In addition, excellent humidity responsiveness is attributed to enhanced adsorption capability of GUDE-printed surface microstructures due to large specific surface area and hydrophobic properties of graphene. In conclusion, the GUDE process, as a fast, direct electronic printing technology, offers broad prospects in the fabrication of flexible, high-performance electrical sensors, and has great potential for manufacturing advanced electronic devices.
Article
Continuous basalt fiber (CBF) is an outstanding inorganic fiber produced from nature, which has a wide range of applications in the field of armor protection of national defense military. However, the mechanical response and failure mechanism of 3D printed CBF reinforced components are still not well understood. Here, the 3D printing thermoplastic composites with high volume fraction CBF have been successfully prepared by fused deposition modelling (FDM) method. The effects of fiber printing direction and polymer matrix type on the tensile and flexural properties of the 3D printed composites have been explored, and the detailed failure morphology has been characterized using scanning electron microscopy and optical microscopy. It was found that under high fiber volume fraction, 3D printed CBF reinforced polyamides (PA) composites have the best ability to maintain material integrity of the composites, followed by acrylonitrile butadiene styrene (ABS) and high impact polystyrene (HIPS). Besides, the results from rule of mixtures can accurately predict the longitudinal Young’s modulus of the 3D printed specimens, but there exists a large discrepancy for the prediction of the tensile strength. The microstructure analysis shows that the failure modes of 3D printed composites mainly include fiber debonding, fiber pull-out, stress whitening and matrix cracking.
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In this paper a new methodology developed for predicting the mechanical performance of the structures additively manufactured by Fused Filament Fabrication is presented. The novelty of the approach consists in accounting for the anisotropy in the material properties induced by the printing patterns. To do so we partition the manufactured structure according to the printing patterns used in a single component. For determining the material properties of each partition, a hybrid experimental/computational characterization is proposed. The external partitions with aligned (contour) and crossed (cover) filaments are characterized through uniaxial tensile tests on General Purpose Acrylonitrile Butadiene Styrene dog-bone samples with corresponding patterns. Characterization of the inner structure (infill/lattice) is done through computational homogenization technique using Representative Volume Element. The presented methodology is validated against experimental results of square cross-section demonstrators. It is shown that the material properties depend on the geometrical relationship of the different printing patterns, exclusively. Therefore, the exhaustive experimental procedure can be avoided characterizing the printed material by a pre-defined anisotropic constitutive relationship proportional to the properties of the raw material. Moreover, the acquired geometrical relationship is validated for components made of Polylactic Acid. The given methodology may be used as design-for-manufacture tool for creating functional components.
Conference Paper
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عملگرهای پنوماتیکی نرم که از مواد هایپر الاستیک ساخته شده اند، مزایایی از جمله انعطاف پذیری بالا و ساخت آسان و کم هزینه نسبت به عملگرهای صلب رباتیک دارند و در زمینه های مختلفی از جمله صنایع فضایی، حمل و نقل و پزشکی ... مورد استفاده قرار می گیرند. طراحی و تحلیل رفتار این عملگرها به دلیلی ماهیت غیر خطی مواد هایپر الاستیک آن و روش های ساخت جدید افزایشی مانند پرینتر سه بعدی پروسه ای چالش برانگیز می اشد. در این مقاله، تاثیر جهت لایه چینی نازل پرینتر سه بعدی و فاصله گام الیاف کولار بر رفتار خمشی و تنش های عملگر نرم با استفاده از روش اجزای محدود مورد بررسی قرار گرفته است.
Article
Researchers and industries rely heavily on standardized testing methods to ensure products are designed and manufactured with high quality. With increasing use of additive manufacturing processes, such as material extrusion (MEX), there is a significant gap in material testing standards tailored for such components, and a lack of guidance on preparing appropriate test specimens with mesostructures that best represent the final part being analyzed. This paper aims to support the standardization of MEX material testing by reviewing the current methods used for preparing test specimens for tensile testing and proposing guidelines for implementation in a new standard. The need for standardization of MEX specimen preparation is addressed by analyzing the effects of slicing parameters on resulting tensile properties of the specimen. It is suggested that a standard should acknowledge these parameters, in addition to specimen geometry, toolpath optimization, printer and material specifications, so that they are appropriately selected for the test specimen by regarding the final part structure. Consideration of the proposed guidelines in a standardized method may enable comparisons between published results and support the development of MEX technology for use in advanced applications.
Article
Purpose: Masked stereolithography (MSLA) or resin three-dimensional (3D) printing is one of the most extensively used high-resolution additive manufacturing technologies. Even though, the quality of 3D printing is determined by several factors, including the equipment, materials and slicer. Besides, the layer height, print orientation and exposure time are important processing parameters in determining the quality of the 3D printed green state specimen. The purpose of the paper is to optimize the printing parameters of the Masked Stereolithography apparatus for its dimensional correctness of 3D printed parts using the Taguchi method. Design/methodology/approach: The acrylate-based photopolymer resin is used to produce the parts using liquid crystal display (LCD)-type resin 3D printer. This study is mainly focused on optimizing the processing parameters by using Taguchi analysis, L-9 orthogonal array in Minitab software. Analysis of variance (ANOVA) was performed to determine the most influencing factors, and a regression equation was built to predict the best potential outcomes for the given set of parameters and levels. The signal-to-noise ratios were calculated by using the smaller the better characteristic as the deviations from the nominal value should be minimum. The optimal levels for each factor were determined with the help of mean plots. Findings: Based on the findings of ANOVA, it was observed that exposure time plays an important role in most of the output measures. The model’s goodness was tested using a confirmation test and the findings were found to be within the confidence limit. Also, a similar specimen was printed using the fused filament fabrication (FFF) technique; it was compared with the quality and features of MSLA 3D printing technology. Practical implications: The study presents the statistical analysis of experimental results of MSLA and made a comparison with FFF in terms of dimensional accuracy and print quality. Originality/value: Many previous studies reported the results based on earlier 3D printing technology such as stereolithography but LCD-based MSLA is not yet reported for its dimensional accuracy and part quality. The presented paper proposes the use of statistical models to optimize the printing parameters to get dimensional accuracy and the good quality of the 3D printed green part.
Article
Lattice structures have been widely used in aircraft and automobile industries due to their excellent mechanical properties namely high specific strength, specific stiffness, and energy absorption capability. On the other hand, additive manufacturing that is considered as an essential for Industry 4.0 offers incredible opportunities for product development and production flexibility. Previous research on 3D printed isogrid structures focused on isogrid panels and their buckling behavior, whereas isogrid lattice cylindrical shells garnered less attention. This work reports the effect of short carbon fiber reinforcement with polyamide three‐dimensional printing material on the compression response of isogrid lattice shell structures by experimental and numerical modeling. Isogrid cylindrical shells were three dimensionally printed using fused deposition modeling. Initially, test coupons were printed using polyamide and carbon fiber reinforced polyamide and their mechanical properties were found using uniaxial tensile testing. The obtained tensile properties were given as an input to the numerical modeling performed using LS‐DYNA®. The peak load and the maximum displacement of the printed isogrid lattice shells subjected to axial compression loads were experimentally evaluated. The numerical findings were compared with those produced using experimental methods. The error in estimating the peak load of lattice cylinders through numerical modeling was limited to 5.35%. The effect of geometric parameters namely rib width (helical and hoop), shell thickness, helical angle of ribs on the buckling strength was also studied.
Article
Three‐dimensional printing has proven to be a convenient and effective method for manufacturing structured electromagnetic wave (EMW) absorbers with adjustable EMW absorption characteristics. In this study, composites of multi‐walled carbon nanotube (MWCNT) and polyamide 12 (PA12) were prepared via wet dispersion and mechanical ball milling followed by melt extrusion. The effects of different levels of MWCNT content on the EMW absorption and mechanical properties of the MWCNT/PA12 composite were examined. Within the MWCNT content from 7 to 12 wt%, the flexural strength of the composite increases with the addition of MWCNT, and the impact strength, tensile strength, and volume resistivity of the composite decrease with the addition MWCNT. With regard to the best impedance matching, when sodium dodecylbenzene sulfonate was used as the dispersant, the lowest reflection loss observed herein for the MWCNT/PA12 composite was −20 dB, which was achieved with an MWCNT content of 10 wt%. Furthermore, the composite exhibited superior mechanical properties. The tensile and flexural moduli of the composite were 18.85% and 33.97% higher than those of pure PA12, respectively. Moreover, the MWCNT/PA12 composite was proven to be a high performance modeling material suitable for fused deposition modeling. And the tensile strength, flexural modulus, and impact strength of the printed samples can reach 94.45%, 92.94%, and 85.51% of those of the injection‐molded samples, respectively. In this study, composites of multi‐walled carbon nanotube (MWCNT) and Nylon 12 (PA12) were prepared via wet dispersion and mechanical ball milling followed by melt extrusion. The effects of different levels of MWCNT content on the electromagnetic wave absorption and mechanical properties of the MWCNT/PA12 composite were examined.
Article
The study aim was to develop a 3D model representing the aircraft air conditioning system with the purpose of performing a numerical experiment in an automated environment of engineering analysis. The completeness of this model was associated with the required result of the numerical experiment. During the experiment, we simulated conditions for the flow of aerodynamic processes in the vicinity of the louvre integrated into the fuselage skin at the point of communication between the air conditioning system and the external environment. Of particular interest was that part of the air conditioning system, which directly affects the louvre strength. The Siemens NX computer-aided design system was used to form a digital copy of the original. The toolkit of this system allows high-precision geometric models to be designed. As a result, a 3D-model was obtained applicable to simulate external and internal aerodynamical processes in the digital environment of engineering calculations for evaluating the strength parameters of the studied part. This model is a combination of geometric objects formed by a set of assembly units. In particular, such elements of the air conditioning system as the cooling turbine, radiator, and valve, are considered. In order to recreate the complex geometry of the original assembly parts of these units, an algorithm for selecting and performing typical operations of the Siemens NX system was developed and optimized for constructing correct 3D models. The constructed 3D model of the aircraft air conditioning system can be used when simulating external and internal aerodynamical processes affecting the louvre strength in the digital environment of engineering calculations. The proposed model allows users to study the structure of aircraft air conditioning systems.
Chapter
Photopolymers represent the largest portion of the additive manufacturing materials market and have a wide variety of applications. The term photopolymer refers to a class of light-sensitive resins that solidify when exposed to ultraviolet light. They are mainly composed of monomers, binders, and photoinitiators. Photopolymerization finds immense applications in the field of microelectronics, printing plates, coatings, adhesives, dentistry, contact lenses, and so on. Photopolymers are also applied in 3D printing to create complex architectures with better mechanical and chemical functionalities. Development of variety of functional resins can extend the applications of photopolymers in biomedical and electronic industries. This chapter details various types of photopolymers, their properties, and applications in 3D printing.
Chapter
The chapter describes the commonly used classification of additive manufacturing (AM) processes described in the International Standard ISO/ASTM 52900, the classification according to the method of deposition and fixation of layers and according to the type of material used in the process. The technologies included in each of these seven main process categories are briefly characterized, pointing to their applicability and possible limitations. Moreover, the main parameters determining the quality of 3D printing and the applicability of individual technologies are shown, as well as a comparison of the precision of parts production, their size, time consumption, the need for support and finishing processes, or the amount of generated waste. Finally, the current use of each technology and forecasts for growth in their use are also presented.
Chapter
In this chapter an overview of thermoplastic polymers used in fuse deposition modeling 3D printing is given. Only the most common polymers that are used in the form of commercially available 3D printing filaments are considered. Polymers are presented following the pyramid of polymers classification, ranging from commodity (high-density PE, polypropylene, poly(methyl methacrylate), polystyrene, and poly(vinyl alcohol)), engineering (acrylonitrile butadiene styrene, acrylonitrile styrene acrylate, polylactide, polyamide, polyesters, polycarbonate, thermoplastic polyurethane) to high-performance polymers (polyetherimide, polyether ether ketone, polyphenylsulfone). The description of each polymer starts with a short introduction, description of chemical structure and polymer synthesis, polymer characteristics, its processing, applications, and ends with recycling. The emphasis is on 3D printing, which includes recommendations for print settings, features of printing process, printing tips, and characteristics of printed object. Advantages and disadvantages are highlighted and some typical properties of 3D printing filament are given. Briefly, composites and speciality 3D printing filaments offered on a commercial basis are described, too.
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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.
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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).
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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Three-dimensional (3D) printing, also referred to as additive manufacturing, is a technology that allows for customized fabrication through computer-aided design. 3D printing has many advantages in the fabrication of tissue engineering scaffolds, including fast fabrication, high precision, and customized production. Suitable scaffolds can be designed and custom-made based on medical images such as those obtained from computed tomography. Many 3D printing methods have been employed for tissue engineering. There are advantages and limitations for each method. Future areas of interest and progress are the development of new 3D printing platforms, scaffold design software, and materials for tissue engineering applications.
Conference Paper
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An entry level consumer priced 3d-printer, the MakerBot Replicator 2x, was used to print specimen to conduct tensile, flexural and fatigue testing. Average priced, generic brand PLA material was used (similar to the filament a home user may purchase). Specimen were printed at raster orientation angles of 0°, 45° and 90° to test orientation effects on part strength. PLA filament was also tensile tested. Tensile testing of the 3d-printed specimens showed that the 45° raster orientation angle made the strongest specimen at an ultimate tensile strength of 64 MPa. The 0° and 90° raster orientation were not much less at 58 MPa and 54 MPa. A 3-point bending fixture was used to conduct flexural testing on printed specimen. For this type of testing, the 0° raster orientation produced the strongest parts with an ultimate bending stress of 102 MPa. Both the 45° and 90° raster orientations had similar results at 90 MPa and 86 MPa. For the fatigue testing, there was no clear best option, but there was a clearly worst option, the 90° raster orientation. This orientation clearly had lower fatigue lives than either of the other two raster orientations. The other two raster orientations, 0° and 45°, were very similar. PLA filament testing using bollard style grips, showed that the PLA filament exhibited mechanical properties similar to that of printed specimen — when tested at high enough strain rates that creep damage didn’t play a significant role. This may lead to implications for recycling failed 3d-print jobs and turning it back into reusable filament.
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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.
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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.
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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.
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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.
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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.
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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.
Chapter
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.
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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.
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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.
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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.
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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.
Conference Paper
Additive manufacturing (AM) is a class of manufacturing processes where mater