Advent Of Additive Manufacturing Technologies Research Articles

Fracture mechanics of bi-material lattice metamaterials

The advent of additive manufacturing technology empowers precise control of multi-material components or specific defects in lightweight lattice metamaterials, however, fracture mechanics and toughening design strategies in such metamaterials remain enigmatic. By incorporating theoretical analysis, numerical simulation, and experimental investigation, our study reveals that stretch-bend synergistic strut deformations caused by bi-material components or topology defects contribute notably tougher lattice structures surpassing its ideal single-material lattices. A peak fracture energy at a critical modulus ratio was found in a designed bi-material lattice composed of triangular soft struts and hexagonal stiff struts, which originates from the shift of fracture modes at crack tip from strut bending to stretching dominated failure modes as the modulus of soft struts increases, where the compromise in competition between bending-enhanced and stretching-weakened energy dissipations of struts deformations results in the maximized fracture energy. A parametric design protocol was proposed to optimize fracture energy of bi-material lattices through tuning the modulus ratio and relative density. Furthermore, the concept of stretch-bend synergistic toughening can also be applied to make tougher single-material lattices with specific topological defects. Our findings not only provide physical insights into directing crack propagation but also provide quantitative guidance to optimize fracture resistance within low-density tough lattice metamaterials.

3D-printed calcium magnesium silicates: A mini-review

Calcium magnesium silicates (CMS) represent a class of minerals with diverse applications in fields ranging from geology to materials science. With the advent of additive manufacturing technologies, particularly 3D printing, novel opportunities have emerged for the synthesis and utilization of CMS-based materials. In this mini-review, we provide a thorough overview of recent advancements in the 3D printing of CMS compounds, including diopside (DPS), bredigite (BR), and akermanite (AKT). We discuss the synthesis methods, properties, and potential applications of 3D-printed CMS materials, with a focus on their role in biomedical applications. Furthermore, we highlight challenges and prospects in the field, emphasizing the importance of continued research and innovation in harnessing the full potential of 3D-printed CMS materials.

Additive manufacture of ultrasoft bioinspired metamaterials

The dynamic loading behavior of materials plays a vital role in various engineering applications, such as aerospace protective components, armor, marine infrastructures, and automotive crash safety. The advent of additive manufacturing technologies has enabled the design of metamaterials that exhibit exceptional mechanical performance and artificially engineered properties not found in nature. However, fabricating ideal materials that resist dynamic loading is challenging because of the complexity of dynamic mechanical processes and varying requirements across different applications. In this study, a novel hierarchical design is proposed that combines natural fiber-inspired frameworks with graphene-inspired parent structures. This design aims to produce metamaterials, with characteristics such as reduced dynamic compressive strength, high energy absorption, and programmable dynamic loading, via advanced manufacturing technologies. An additive-manufacturing-oriented digital design approach and machine learning techniques were employed to engineer the dynamic loading performance of graphene-inspired metamaterials using the bonding principles inspired by natural fibers, to facilitate the design of next-generation metamaterial for advanced manufacturing. Experimental results illustrate the significant improvements achieved with our metamaterials compared to their existing counterparts. These improvements include a decrease in dynamic compressive strength of up to 86 %, while maintaining a remarkable 682 % enhancement in energy absorption during dynamic compressions, with a 42 % reduction in the energy decay rate. A compositional design strategy and programmable dynamic compression curve methodology is proposed that enable the tailored optimization of dynamic loading behaviors without modifying the base topology of metamaterials. This research offers a promising pathway for the development of next-generation materials, engineered to withstand dynamic loadings with intelligent and programmable performances suitable for aerospace, defense, and other high-value applications. By leveraging the advantages of natural fiber-inspired structures and graphene-inspired metamaterials, this work contributes to the advancement of materials with tailored resistance to dynamic loading and opens new possibilities for intelligent dynamic loading performance.

Current Status and Future Outlook of Additive Manufacturing Technologies for the Reconstruction of the Trachea.

Tracheal stenosis and defects occur congenitally and in patients who have undergone tracheal intubation and tracheostomy due to long-term intensive care. Such issues may also be observed during tracheal removal during malignant head and neck tumor resection. However, to date, no treatment method has been identified that can simultaneously restore the appearance of the tracheal skeleton while maintaining respiratory function in patients with tracheal defects. Therefore, there is an urgent need to develop a method that can maintain tracheal function while simultaneously reconstructing the skeletal structure of the trachea. Under such circumstances, the advent of additive manufacturing technology that can create customized structures using patient medical image data provides new possibilities for tracheal reconstruction surgery. In this study, the three-dimensional (3D) printing and bioprinting technologies used in tracheal reconstruction are summarized, and various research results related to the reconstruction of mucous membranes, cartilage, blood vessels, and muscle tissue, which are tissues required for tracheal reconstruction, are classified. The prospects for 3D-printed tracheas in clinical studies are also described. This review serves as a guide for the development of artificial tracheas and clinical trials using 3D printing and bioprinting.

Customized Additive Manufacturing in Bone Scaffolds-The Gateway to Precise Bone Defect Treatment.

In the advancing landscape of technology and novel material development, additive manufacturing (AM) is steadily making strides within the biomedical sector. Moving away from traditional, one-size-fits-all implant solutions, the advent of AM technology allows for patient-specific scaffolds that could improve integration and enhance wound healing. These scaffolds, meticulously designed with a myriad of geometries, mechanical properties, and biological responses, are made possible through the vast selection of materials and fabrication methods at our disposal. Recognizing the importance of precision in the treatment of bone defects, which display variability from macroscopic to microscopic scales in each case, a tailored treatment strategy is required. A patient-specific AM bone scaffold perfectly addresses this necessity. This review elucidates the pivotal role that customized AM bone scaffolds play in bone defect treatment, while offering comprehensive guidelines for their customization. This includes aspects such as bone defect imaging, material selection, topography design, and fabrication methodology. Additionally, we propose a cooperative model involving the patient, clinician, and engineer, thereby underscoring the interdisciplinary approach necessary for the effective design and clinical application of these customized AM bone scaffolds. This collaboration promises to usher in a new era of bioactive medical materials, responsive to individualized needs and capable of pushing boundaries in personalized medicine beyond those set by traditional medical materials.

Impact behavior of auxetic structures: Experimental and numerical analysis

Auxetic materials are structured lattice materials with a negative Poisson’s ratio (NPR) and excellent tensile and impact strength compared to conventional bulk materials. It could be used for crashworthy structural applications in aerospace, automotive, and biomedical sections due to its very high specific energy absorption capacity compared to honeycomb structures. With the advent of additive manufacturing technology, it is possible to fabricate complex auxetic structures using metallic, ceramic, and polymeric materials. The literature on the high-speed impact behavior of auxetic structured thermos plastic polylactic acid (PLA) is limited. Therefore, the present work is focused on studying the impact behavior of S-shaped and re-entrant auxetic structures fabricated using Fused Deposition Modeling (FDM). The drop mass impact tests were conducted on these auxetic structures to estimate their impact resistance and energy absorption capability. FEA was undertaken to simulate and validate the impact behavior with experimental results. Quasi-static compression and Split Hopkinson Pressure Bar (SHPB) tests were conducted to get the bulk material's impact properties and material model. These data were used to model material properties in FEA. It was observed that the S-shaped auxetic structure had shown higher compressive plateau stress and energy absorption capacity compared to the re-entrant structure. These auxetic structures' deformation mode and failure were explored through detailed structural analysis using FEA.

Influence of dimension, building position, and orientation on mechanical properties of EBM lattice Ti6Al4V trusses

The advent of additive manufacturing technologies significantly encouraged the development and usage of lattice structures. This paper aims to experimentally investigate the influence of dimension, building position, and orientation on the mechanical properties of Ti6Al4V trusses, manufactured by electron beam melting process, to be used in lattice cells. Specimens were manufactured considering the following parameters: truss diameter (1, 1.5, 2 mm), growth orientation (0°, 45°, 90°), and specimen position inside the building chamber. Trusses with diameter of 1 mm showed inconsistent mechanical properties caused by the poor manufacturing quality. Specimen position was found to influence the analyzed mechanical properties. Unmelted powders were observed to affect the outer surfaces of all specimens and the whole cross-sections of specimens manufactured at 0°. Specimens manufactured at 45° with diameter of 2 mm demonstrated the best performances, whereas specimens manufactured at 90° with diameter of 2 mm displayed the highest elongation at fracture.

Design and test a converging and de Laval nozzle using additive manufacturing

The advent of additive manufacturing technology has facilitated the design and fabrication of parts and models in both academia and aerospace industry. Compressible flow in the nozzles is not a new research topic; however, the accuracy of the experimental results obtained from the nozzles using additive manufacturing has not been assessed comprehensively. Surface roughness and strength of 3D-printed nozzles are two major concerns when they are applied to compressible flows. In this paper, a converging and a de Laval nozzle fabricated by additive manufacturing using ABS filament are designed and tested. Surface roughness inside the converging nozzle is quantified using a nondestructive method. In general, the experimental results compare well with the analytical solutions from isentropic equations for the converging nozzle and the numerical simulations conducted in ANASYS Fluent for the de Laval nozzle. 3D-printed nozzles can be employed to quickly demonstrate and verify novel ideas and concepts in the pedagogy and research at large Reynolds numbers.

Investigation of thermal influence on weld microstructure and mechanical properties in wire and arc additive manufacturing of steels

Alloy steels are commonly used in many industrial and consumer products to take advantage of their strength, ductility, and toughness properties. In addition, their machinability and weldability performance make alloy steels suitable for a range of manufacturing operations. The advent of additive manufacturing technologies, such as wire and arc additive manufacturing (WAAM), has enabled welding of alloy steels into complex and customized near net-shape products. However, the functional reliability of as-built WAAM products is often uncertain due to a lack of understanding of the effects of process parameters on the material microstructure and mechanical properties that develop during welding, primarily driven by thermal phenomena. This study investigated the influence of thermal phenomena in WAAM on the microstructure and mechanical properties of two alloy steels (G4Si1, a mild steel, and AM70, a high-strength, low-alloy steel). The interrelationships between process parameters, heating and cooling cycles of the welded part, and the resultant microstructure and mechanical properties were characterized. The welded part experienced multiple reheating cycles, a consequence of the layer-by-layer manufacturing approach. Thus, high temperature gradients at the start of the weld formed fine grain structure, while coarser grains were formed as the height of the part increases and the temperature gradient decreased. Microstructural analysis identified the presence of acicular ferrite and equiaxed ferrite structures in G4Si1 welds, as well as a small volume fraction of pearlite along the ferrite grain boundaries. Analysis of AM70 welds found acicular ferrite, martensite, and bainite structures. Mechanical testing for both materials found that the hardness of the material decreased with the increase in the height of the welded part as a result of the decrease in the temperature gradient and cooling rate. In addition, higher hardness and yield strength, and lower elongation at failure was observed for parts printed using process parameters with lower energy input. The findings from this work can support automated process parameter tuning to control thermal phenomena during welding and, in turn, control the microstructure and mechanical properties of printed parts.

Advances in mechanical metamaterials for vibration isolation: A review

The adverse effect of mechanical vibration is inevitable and can be observed in machine components either on the long- or short-term of machine life-span based on the severity of oscillation. This in turn motivates researchers to find solutions to the vibration and its harmful influences through developing and creating isolation structures. The isolation is of high importance in reducing and controlling the high-amplitude vibration. Over the years, porous materials have been explored for vibration damping and isolation. Due to the closed feature and the non-uniformity in the structure, the porous materials fail to predict the vibration energy absorption and the associated oscillation behavior, as well as other the mechanical properties. However, the advent of additive manufacturing technology opens more avenues for developing structures with a unique combination of open, uniform, and periodically distributed unit cells. These structures are called metamaterials, which are very useful in the real-life applications since they exhibit good competence for attenuating the oscillation waves and controlling the vibration behavior, along with offering good mechanical properties. This study provides a review of the fundamentals of vibration with an emphasis on the isolation structures, like the porous materials (PM) and mechanical metamaterials, specifically periodic cellular structures (PCS) or lattice cellular structure (LCS). An overview, modeling, mechanical properties, and vibration methods of each material are discussed. In this regard, thorough explanation for damping enhancement using metamaterials is provided. Besides, the paper presents separate sections to shed the light on single and 3D bandgap structures. This study also highlights the advantage of metamaterials over the porous ones, thereby showing the future of using the metamaterials as isolators. In addition, theoretical works and other aspects of metamaterials are illustrated. To this end, remarks are explained and farther studies are proposed for researchers as future investigations in the vibration field to cover the weaknesses and gaps left in the literature.

Coatability of diamond-like carbon on 316L stainless steel printed by binder jetting

Diamond-like carbon (DLC) coatings are efficient in improving surface properties of functional components and parts. For conventionally manufactured materials and products, the DLC coatings are on a high level of development and industrially well established. However, with the advent of additive manufacturing technologies and the unique microstructure of the produced parts, so far the properties of the DLC coatings on these surfaces have not been extensively investigated. Additively manufactured materials possess process-related structural characteristics, such as residual porosity or an anisotropic material behavior, thereby leading to distinguished properties of the substrate/coating system compared to conventionally fabricated substrate materials. Therefore, 316L substrates are produced with an intended residual porosity and different building directions by binder jetting and subsequently coated with DLC in a magnetron sputtering process. Conventionally manufactured 316L substrates were also coated to evaluate the manufacturing effects on the DLC properties. Based on the analysis of DLC coated open pores, a model is developed to describe the growth mechanisms of thin PVD coatings on open pores of different size. The thin DLC coating entirely covers residual porosity when the pore size (opening diameter) is smaller than or equal to the coating thickness of ~3 µm. Independently of the residual porosity or building orientation, the DLC coating provides a high hardness of 24 GPa and reveals a high adhesion strength to all binder jetted 316 L substrates. Compared to conventional manufacturing routes, the combination of additive manufacturing and DLC deposition is a competitive approach to fabricate complex-shaped components and parts with enhanced surface properties.

Heat transfer performance of a finned metal foam-phase change material (FMF-PCM) system incorporating triply periodic minimal surfaces (TPMS)

Metal foams have been used extensively to enhance the thermal conductivity of phase change materials (PCMs) in thermal energy storage (TESs) systems and thermal management systems (TMSs). The conventional metal foam structure, referred to commonly as the Kelvin cell, has been characterized well and the effects of its geometric and macroscopic parameters, such as porosity, pore size, and surface area density, on the performance of metal foam–PCM composites have been investigated extensively. With the advent of additive manufacturing technology, any intricate and complex architecture can be manufactured easily, thereby opening doors for the utilization of several other candidate foams and structures in TES systems and TMSs. In this work, three triply periodic minimal surface (TPMS)-based foams (Gyroid, IWP, and Primitive) were used in a finned metal foam–PCM (FMF–PCM) system, and their heat transfer performances were compared with that of the conventional metal foam. Pure conduction and natural convection-based transient phase change simulations were performed under isothermal conditions. The results indicated that all TPMS structures exhibited enhanced heat transfer performance by reducing the melting time of the PCM and increasing the average heat transfer coefficient. Hence, TPMS-based foams offer great promise for use in TES systems and TMSs.

Phase-Selective and Localized TiO2 Coating on Additive and Wrought Titanium by a Direct Laser Surface Modification Approach.

Titanium has been the material of interest in biological implant applications due to its unique mechanical properties and biocompatibility. Their design is now growing rapidly due to the advent of additive manufacturing technology that enables the fabrication of complex and patient-customized parts. Titanium dioxides (TiO2) coatings with different phases (e.g., anatase, rutile) and morphologies have shown to be effective in enhancing osteointegration and antibacterial behavior. This enhanced antibacterial behavior stems from the photocatalytic activity generated from crystalline TiO2 coatings. Anatase has commonly been shown to be a more photocatalytic oxide phase compared to rutile despite its larger band gap. However, more recent studies have suggested that a synergistic effect leading to increased photocatalytic activity may be produced with a combination of oxides containing both anatase and rutile phases. Here, we demonstrate the selective and localized formation of TiO2 nanostructures on additive and wrought titanium parts with anatase, rutile, and mixed phases by a laser-induced transformation approach. Compared to conventional coating processes, this technique produces desired TiO2 phases simply by controlled laser irradiation of titanium parts in an oxygen environment, where needed. The effects of processing conditions such as laser power, scanning speed, laser pulse duration, frequency, and gas flow on the selective transformation were studied. The morphological and structural evolutions were investigated using various characterization techniques. This method is specifically of significant interest in creating phase-selective TiO2 surfaces on titanium-based bioimplants, including those fabricated by additive manufacturing technologies.

Direct ink writing of porous titanium (Ti6Al4V) lattice structures.

Ti6Al4V components, for biomedical and aerospace sectors, are receiving a great interest especially after the advent of additive manufacturing technologies. The most used techniques are Selective Laser Sintering (SLS), Selective Laser Melting (SLM) and Electron Beam Melting (EBM). In the current research, we developed 3D-printed Ti6Al4V scaffolds by Direct Ink Writing (DIW) technology. Appropriate ink formulations, based on water-titanium powder suspensions, were achieved by controlling the rheological properties of the developed inks. After printing process, and drying, the printed components were sintered at 1400 °C under high vacuum for 3 h. Highly porous titanium scaffolds (with porosity up to 65 vol%) were produced and different geometries were printed. The influence of the porosity on the morphology, compression strength and biocompatibility of the scaffolds was investigated.

A Thermomechanical Analysis of Conformal Cooling Channels in 3D Printed Plastic Injection Molds

Plastic injection molding is a versatile process, and a major part of the present plastic manufacturing industry. The traditional die design is limited to straight (drilled) cooling channels, which don’t impart optimal thermal (or thermomechanical) performance. With the advent of additive manufacturing technology, injection molding tools with conformal cooling channels are now possible. However, optimum conformal channels based on thermomechanical performance are not found in the literature. This paper proposes a design methodology to generate optimized design configurations of such channels in plastic injection molds. The design of experiments (DOEs) technique is used to study the effect of the critical design parameters of conformal channels, as well as their cross-section geometries. In addition, designs for the “best” thermomechanical performance are identified. Finally, guidelines for selecting optimum design solutions given the plastic part thickness are provided.

Effect of Unit Cell Type and Pore Size on Porosity and Mechanical Behavior of Additively Manufactured Ti6Al4V Scaffolds.

Porous metal structures have emerged as a promising solution in repairing and replacing damaged bone in biomedical applications. With the advent of additive manufacturing technology, fabrication of porous scaffold architecture of different unit cell types with desired parameters can replicate the biomechanical properties of the natural bone, thereby overcoming the issues, such as stress shielding effect, to avoid implant failure. The purpose of this research was to investigate the influence of cube and gyroid unit cell types, with pore size ranging from 300 to 600 µm, on porosity and mechanical behavior of titanium alloy (Ti6Al4V) scaffolds. Scaffold samples were modeled and analyzed using finite element analysis (FEA) following the ISO standard (ISO 13314). Selective laser melting (SLM) process was used to manufacture five samples of each type. Morphological characterization of samples was performed through micro CT Scan system and the samples were later subjected to compression testing to assess the mechanical behavior of scaffolds. Numerical and experimental analysis of samples show porosity greater than 50% for all types, which is in agreement with desired porosity range of natural bone. Mechanical properties of samples depict that values of elastic modulus and yield strength decreases with increase in porosity, with elastic modulus reduced up to 3 GPa and yield strength decreased to 7 MPa. However, while comparing with natural bone properties, only cube and gyroid structure with pore size 300 µm falls under the category of giving similar properties to that of natural bone. Analysis of porous scaffolds show promising results for application in orthopedic implants. Application of optimum scaffold structures to implants can reduce the premature failure of implants and increase the reliability of prosthetics.

Open-cellular metal implant design and fabrication for biomechanical compatibility with bone using electron beam melting.

Implant history extends more than 4000 years in antiquity, with biocompatible alloy implants extending over only 70 years. Over the past several decades, total hip and knee replacements of Ti-6Al-4V and Co-Cr-Mo alloys have exhibited post implantation life spans extending over 15 years; limited by infection, loosening, stress-shielding-related bone resorption and other mechanical failures. With the advent of additive manufacturing technologies, such as electron beam melting (EBM) over the past decade, personalized, patient-specific; porous (open-cellular) implant components can be manufactured, and the integration of chemical, biological and mechanical methods is able to optimize strategies for improving long-term clinical outcomes. This review outlines these strategies, which include enhanced osseointegration and vascularization prospects, and provides some evidence for, and examples of, clinical trials representative of millions of implant surgeries world-wide.

Thermo-mechanical Design Optimization of Conformal Cooling Channels using Design of Experiments Approach

Plastic injection molding is a versatile process and a major part of the present plastic manufacturing industry. Traditional die design is limited to straight (drilled) cooling channels, which don’t impart optimal thermal (or thermo-mechanical) performance. With the advent of additive manufacturing technology, design of injection molding tools with conformal cooling channels is now possible. The incorporation of conformal cooling channels can improve the thermal performance of an injection mold, though it may compromise the structural or mechanical stability of the mold. However, optimum conformal channels based on thermo-mechanical performance are not found in the literature. This paper proposes a design methodology to generate optimized design configurations of such channels in plastic injection molds. Design of experiments (DOEs) technique is used to study the effect of critical design parameters of conformal channels. In addition, a trade-off technique is utilized to obtain optimum design configurations of conformal cooling channels for “best” thermo-mechanical performance of a mold.

Cell-Laden 3D Printed Scaffolds for Bone Tissue Engineering

Tissue engineering, relying on a combination of biomaterial scaffolds, cells, and bioactive molecules, has emerged as a promising strategy for the treatment of bone defects. The presence of viable cells inside the engineered tissue has been shown to be crucial for bone formation in vivo. However, cells require mechanical support and a physical template, or scaffold, to facilitate their attachment and to stimulate neotissue formation. The advent of additive manufacturing technologies, and most critically three-dimensional (3D) printing, has allowed the development of a new generation of scaffolds. Cells used alongside 3D bioprinting in bone tissue engineering are typically utilized in two different strategies. The first strategy, 3D bioprinting, involves the layer-by-layer deposition of a bioink, made of a scaffold material and cells. The second strategy focuses on the fabrication of a scaffold by printing an acellular material, followed by seeding living cells. Here we review these two approaches, discussing printing techniques, their inconveniences and advantages, hydrogels for 3D printing, and how to overcome obstacles. Finally, we consider the resulting engineered tissues from these two approaches, specifically their mechanical properties, matrix production, and tissue mineralization.

Tools for Sustainable Product Design: Additive Manufacturing

The advent of additive manufacturing technologies presents a number of opportunities that have the potential to greatly benefit designers, and contribute to the sustainability of products. Additive manufacturing technologies have removed many of the manufacturing restrictions that may previously have compromised a designer’s ability to make the product they imagined, which can increase product desirability, pleasure and attachment. Products can also be extensively customized to the user thus, once again, potentially increasing their desirability, pleasure and attachment and therefore their longevity. As additive manufacturing technologies evolve, and more new materials become available, and multiple material technologies are further developed, the field of product design has the potential to greatly change.This paper examines aspects of additive manufacturing from a sustainable design perspective could become a useful tool in the arsenal to bring about the sustainable design of consumer products.