Laser Powder Bed Fusion of Polymers: Quantitative Research Direction Indices.
TL;DR: In this article, the authors statistically evaluated the 100 most cited articles to extract reported material, process, and as-built part properties to analyze the research trends in laser powder bed fusion (L-PBF) of polymer powder feedstocks.
Abstract: Research on Laser Powder Bed Fusion (L-PBF) of polymer powder feedstocks has raised over the last decade due to the increased utilization of the fabricated parts in aerospace, automotive, electronics, and healthcare applications. A total of 600 Science Citation Indexed articles were published on the topic of L-PBF of polymer powder feedstocks in the last decade, being cited more than 10,000 times leading to an h-index of 46. This study statistically evaluates the 100 most cited articles to extract reported material, process, and as-built part properties to analyze the research trends. PA12, PEEK, and TPU are the most employed polymer powder feedstocks, while size, flowability, and thermal behavior are the standardly reported material properties. Likewise, process properties such as laser power, scanning speed, hatch spacing, powder layer thickness, volumetric energy density, and areal energy density are extracted and evaluated. In addition, material and process properties of the as-built parts such as tensile test, flexural test, and volumetric porosity contents are analyzed. The incorporation of additives is found to be an effective route to enhance mechanical and functional properties. Carbon-based additives are typically employed in applications where mechanical properties are essential. Carbon fibers, Ca-phosphates, and SiO2 are the most reported additives in the evaluated SCI-expanded articles for L-PBF of polymer powder feedstocks. A comprehensive data matrix is extracted from the evaluated SCI-index publications, and a principal component analysis (PCA) is performed to explore correlations between reported material, process, and as-built parts.
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TL;DR: A systematic review of 3D-printed polyether ether ketone (PEEK) is presented in this article, where the authors found that most of the applications are still in the research phase.
Abstract: Polyether ether ketone (PEEK) is an organic polymer that has excellent mechanical, chemical properties and can be additively manufactured (3D-printed) with ease. The use of 3D-printed PEEK has been growing in many fields. This article systematically reviews the current status of 3D-printed PEEK that has been used in various areas, including medical, chemical, aerospace, and electronics. A search of the use of 3D-printed PEEK articles published until September 2021 in various fields was performed using various databases. After reviewing the articles, and those which matched the inclusion criteria set for this systematic review, we found that the printing of PEEK is mainly performed by fused filament fabrication (FFF) or fused deposition modeling (FDM) printers. Based on the results of this systematic review, it was concluded that PEEK is a versatile material, and 3D-printed PEEK is finding applications in numerous industries. However, most of the applications are still in the research phase. Still, given how the research on PEEK is progressing and its additive manufacturing, it will soon be commercialized for many applications in numerous industries.
33 citations
TL;DR: In this paper , the basic principle of the LPBF process, scientific and technological progress of several inter-related parameters, feedstock materials, produced properties/defects, and insights of numerical modeling to virtually understand the process behavior.
Abstract: Additive Manufacturing (AM) has revolutionized the manufacturing industry in several directions. Laser powder bed fusion (LPBF), a powder bed fusion AM process, has been dramatically accepted in various industries due to its versatility with several materials, including alloys. This comprehensive review article primarily explains the basic principle of the LPBF process, scientific and technological progress of several inter-related parameters, feedstock materials, produced properties/defects, and insights of numerical modelling to virtually understand the process behavior. Specific attention has been given to selective laser-meted (LPBFed) properties, driven through the microstructure formations and, thereby, concerning defects. The scope of the post-processing techniques to refine microstructure has also been discussed in this review paper. It has been identified that the defects are vital in LPBF process and are primarily governed by the process parameters. Therefore, a wisely chosen, optimized set of parameters can play a crucial role in minimizing defects considerably. Finally, the numerical modeling discussed in this review paper will help the researchers understand the LPBF process.
31 citations
01 Aug 2022
TL;DR: The bottom-up characteristic of additive manufacturing (AM) enables unparalleled control over material and structure, making AM a perfect candidate for FGMs as mentioned in this paper . But due to a lack of understanding of design and manufacturing methods, it remains a challenge to engineer FGMs.
Abstract: Functionally graded materials (FGMs) are desirable in a variety of applications. Due to a lack of understanding of design and manufacturing methods, it remains a challenge to engineer FGMs. Gradient patterns and performance shown in biological materials present motifs for designing FGMs. The bottom-up characteristic of additive manufacturing (AM) enables unparalleled control over material and structure, making AM a perfect candidate for FGMs. The integration of the two provides an unprecedented opportunity for developing next generation advanced materials. In this review, we firstly detail the biological gradient materials/structures in terms of their functions. Subsequently, the art-of-the-state AM methods for fabricating FGMs are reviewed, with a focus on the technology types of AM that can prepare biomimetic material and structural FGMs, especially emphasizing the multiform gradients induced by processing parameters. Then, the performance and application cases of FGMs created by AM are summarized. Finally, an outlook for further developments of AM technologies towards FGMs is provided.
20 citations
TL;DR: In this paper, the authors presented the possibility of printing with PLA and TPU using commercially available filaments and software to obtain the best possible bond strength between two different polymers with respect to printing parameters, surface pattern, and the order of layer application.
Abstract: A 3D printer in FDM technology allows printing with two nozzles, which creates an opportunity to produce multi-material elements. Printing from two materials requires special consideration of the interface zone generated between their geometrical boundaries. This article aims to present the possibility of printing with PLA and TPU using commercially available filaments and software to obtain the best possible bond strength between two different polymers with respect to printing parameters, surface pattern (due to the material contact surface’s roughness), and the order of layer application. The interaction at the interface of two surfaces of two different filaments (PLA-TPU and TPU-PLA) and six combinations of patterns were tested by printing seven replicas for each. A total of 12 combinations were obtained. By analyzing pairs of samples (the same patterns, different order of materials), the results for the TPU/PLA samples were better or very close to the results for PLA/TPU. The best variants of pattern combinations were distinguished. Well-chosen printing parameters can prevent a drop in parts efficiency compared to component materials (depending on the materials combination).
13 citations
01 Oct 2021
TL;DR: In this article, a review of laser sintering polymers with organic and inorganic nanofillers is presented, including key challenges, including dispersion of the nanophase, and methods that have been developed to overcome them.
Abstract: Laser sintering is a commonly used Additive Manufacturing (AM) technique applicable to a variety of applications in fields such as the automotive industry, healthcare, and consumer goods. As well as offering mechanical properties suitable for end-use part production, polymer laser sintering can produce more complex structures than many other AM techniques since it does not require support structures, and parts can be stacked in the build area for more efficient processing. A wide range of polymers should theoretically be processable by laser sintering. However, in practice this is not the case, with only a small number of polymers currently able to be processed reliably and consistently. This paper reviews research that has been undertaken to increase the processability, mechanical properties and functionality of laser sintering polymers through the addition of a range of organic and inorganic nanofillers. It examines key challenges, including dispersion of the nanophase, and methods that have been developed to overcome them. The effects of the nanophase on processability are explored, as well as the importance of key processing parameters. The latest developments on techniques for production of nanocomposite powders and characterisation of parts are discussed. The final properties of laser sintered parts that have been achieved and their potential applications are highlighted, and the current challenges and potential directions for future research are discussed.
10 citations
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TL;DR: Polymers are by far the most utilized class of materials for AM and their design, additives, and processing parameters as they relate to enhancing build speed and improving accuracy, functionality, surface finish, stability, mechanical properties, and porosity are addressed.
Abstract: Additive manufacturing (AM) alias 3D printing translates computer-aided design (CAD) virtual 3D models into physical objects. By digital slicing of CAD, 3D scan, or tomography data, AM builds objects layer by layer without the need for molds or machining. AM enables decentralized fabrication of customized objects on demand by exploiting digital information storage and retrieval via the Internet. The ongoing transition from rapid prototyping to rapid manufacturing prompts new challenges for mechanical engineers and materials scientists alike. Because polymers are by far the most utilized class of materials for AM, this Review focuses on polymer processing and the development of polymers and advanced polymer systems specifically for AM. AM techniques covered include vat photopolymerization (stereolithography), powder bed fusion (SLS), material and binder jetting (inkjet and aerosol 3D printing), sheet lamination (LOM), extrusion (FDM, 3D dispensing, 3D fiber deposition, and 3D plotting), and 3D bioprinting....
2,136 citations
TL;DR: An overview of a diverse range of fibers, their properties, functionality, classification, and various fiber composite manufacturing techniques is presented to discover the optimized fiber-reinforced composite material for significant applications.
Abstract: Composites have been found to be the most promising and discerning material available in this century. Presently, composites reinforced with fibers of synthetic or natural materials are gaining more importance as demands for lightweight materials with high strength for specific applications are growing in the market. Fiber-reinforced polymer composite offers not only high strength to weight ratio, but also reveals exceptional properties such as high durability; stiffness; damping property; flexural strength; and resistance to corrosion, wear, impact, and fire. These wide ranges of diverse features have led composite materials to find applications in mechanical, construction, aerospace, automobile, biomedical, marine, and many other manufacturing industries. Performance of composite materials predominantly depends on their constituent elements and manufacturing techniques, therefore, functional properties of various fibers available worldwide, their classifications, and the manufacturing techniques used to fabricate the composite materials need to be studied in order to figure out the optimized characteristic of the material for the desired application. An overview of a diverse range of fibers, their properties, functionality, classification, and various fiber composite manufacturing techniques is presented to discover the optimized fiber-reinforced composite material for significant applications. Their exceptional performance in the numerous fields of applications have made fiber-reinforced composite materials a promising alternative over solitary metals or alloys.
619 citations
TL;DR: Three-dimensional nanocomposite scaffolds provide a biomimetic environment for osteoblastic cell attachment, proliferation and differentiation and have great potential for bone tissue engineering applications.
351 citations
TL;DR: Together with osteoconductive nanocomposite material and controlled growth factor delivery strategies, the use of SLS technique to form complex scaffolds will provide a promising route towards individualized bone tissue regeneration.
Abstract: Integrating an advanced manufacturing technique, nanocomposite material and controlled delivery of growth factor to form multifunctional tissue engineering scaffolds was investigated in this study. Based on calcium phosphate (Ca–P)/poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) nanocomposite microspheres, three-dimensional Ca–P/PHBV nanocomposite scaffolds with customized architecture, controlled porosity and totally interconnected porous structure were successfully fabricated using selective laser sintering (SLS), one of the rapid prototyping technologies. The cytocompatibility of sintered Ca–P/PHBV nanocomposite scaffolds, as well as PHBV polymer scaffolds, was studied. For surface modification of nanocomposite scaffolds, gelatin was firstly physically entrapped onto the scaffold surface and heparin was subsequently immobilized on entrapped gelatin. The surface-modification improved the wettability of scaffolds and provided specific binding site between conjugated heparin and the growth factor recombinant human bone morphogenetic protein-2 (rhBMP-2). The surface-modified Ca–P/PHBV nanocomposite scaffolds loaded with rhBMP-2 significantly enhanced the alkaline phosphatase activity and osteogenic differentiation markers in gene expression of C3H10T1/2 mesenchymal stem cells. Together with osteoconductive nanocomposite material and controlled growth factor delivery strategies, the use of SLS technique to form complex scaffolds will provide a promising route towards individualized bone tissue regeneration.
145 citations
TL;DR: In vivo results showed that both nano-HA/PCL composite scaffolds and PCL scaffolds exhibited good biocompatibility and osteogenesis and fulfilled all the basic requirements of bone tissue engineering scaffolds, which show large potential for use in orthopedic and reconstructive surgery.
Abstract: The regeneration of functional tissue in osseous defects is a formidable challenge in orthopedic surgery. In the present study, a novel biomimetic composite scaffold, here called nano-hydroxyapatite (HA)/poly-e-caprolactone (PCL) was fabricated using a selective laser sintering technique. The macrostructure, morphology, and mechanical strength of the scaffolds were characterized. Scanning electronic microscopy (SEM) showed that the nano-HA/PCL scaffolds exhibited predesigned, well-ordered macropores and interconnected micropores. The scaffolds have a range of porosity from 78.54% to 70.31%, and a corresponding compressive strength of 1.38 MPa to 3.17 MPa. Human bone marrow stromal cells were seeded onto the nano-HA/PCL or PCL scaffolds and cultured for 28 days in vitro. As indicated by the level of cell attachment and proliferation, the nano-HA/PCL showed excellent biocompatibility, comparable to that of PCL scaffolds. The hydrophilicity, mineralization, alkaline phosphatase activity, and Alizarin Red S staining indicated that the nano-HA/PCL scaffolds are more bioactive than the PCL scaffolds in vitro. Measurements of recombinant human bone morphogenetic protein-2 (rhBMP-2) release kinetics showed that after nano-HA was added, the material increased the rate of rhBMP-2 release. To investigate the in vivo biocompatibility and osteogenesis of the composite scaffolds, both nano-HA/PCL scaffolds and PCL scaffolds were implanted in rabbit femur defects for 3, 6, and 9 weeks. The wounds were studied radiographically and histologically. The in vivo results showed that both nano-HA/PCL composite scaffolds and PCL scaffolds exhibited good biocompatibility. However, the nano-HA/PCL scaffolds enhanced the efficiency of new bone formation more than PCL scaffolds and fulfilled all the basic requirements of bone tissue engineering scaffolds. Thus, they show large potential for use in orthopedic and reconstructive surgery.
135 citations