Monotonic and cyclic compressive performance of self-monitoring MWCNT/PA12 cellular composites manufactured by selective laser sintering

Lithium-ion Batteries Fabricated Entirely with Additive Manufacturing Craig Milroy1,2, Tim Phillips1, Abhimanyu Bhat1,3, David Bourell1, Joseph Beaman1 1Department of Mechanical Engineering, University of Texas, Austin; 2Texas Research Institute, Austin; 3Evonik/Structured Polymers, Inc.There is an immediate need for disruptive battery manufacturing technologies that enable novel architectures and improve energy density by reducing packaging, interconnect, and integration requirements. Most conventional batteries are packaged in rigid metal containers with a restricted range of cell geometries and form factors; this poses major challenges for minimizing footprint and integrating batteries into small spaces. Additive manufacturing (AM) methods fabricate parts layer-by-layer by precisely assembling materials according to digitized instructions, and offer a means for simplified, top-down battery production, which provides enormous freedom to create innovative two-dimensional (2D) and 3D electrode architectural designs, customize battery form factor, and enable on-demand manufacturing. As such, AM offers a paradigm shift in electrochemical device design and manufacturing to accommodate novel geometries, improve energy density, and reduce costs. However, AM is still an emerging field, and while there have been numerous reports describing the use of AM techniques to produce components for batteries and supercapacitors, the vast majority of these efforts have focused on single components (typically the electrodes), rather than on complete systems comprising printed electrodes, separators, and cases.In this presentation, we describe methods to fabricate all necessary components of coin and pouch cells for functional prototype lithium-ion (Li-ion) batteries, using a variety of AM techniques. For example, functional graphite anodes, and cathodes based on nickel-manganese-cobalt oxide (NMC) and lithium iron phosphate (LFP), were fabricated with pneumatic extrusion, screen printing, and selective laser sintering (SLS); polymeric separators were fabricated with SLS; cases/enclosures were fabricated with SLS and direct metal laser sintering (DMLS), and metal components (e.g., foils and tabs) were fabricated with DMLS.We also utilized AM as a rapid-prototyping tool to implement novel component design approaches that improve battery performance, for example:(1) we identified improved electrode configurations by fabricating a wide range of free-standing anodes and cathodes (i.e., electrodes that do not contain or require a metal current collector) using a range of SLS fabrication parameters, then quantified the internal electrode structure/porosity with X-ray computed tomography (XCT) analyses, and used the XCT data to investigate the relationship between AM build parameters and electrochemical performance;(2) we fabricated separators with SLS using a variety of materials (i.e., polypropylene, aluminum oxide, polypropylene-polyethylene copolymer, polyether ether ketone (PEEK), polyester, and blends of these materials). SLS is well-suited to producing porous films, since spherical particles can be lightly melted to create a continuous object with ample void space, minimal membrane thickness, and maximum planar uniformity by preconditioning the printing powders (to prevent clumping), and using a machined build-plate to limit powder depth.The cycle performance of NMC-based cathodes fabricated with extrusion/direct-write and screen-printing was essentially identical to tape-cast (control) cathodes; however, the extrusion-printed cathodes exhibited more pronounced capacity-fade, and there was evidence of electrode-maturation processes, indicating the need for further optimization. The electrochemical performance of LFP-based cathodes fabricated with SLS was found to depend strongly on build setpoints and discharge rate, but exhibited robust extended cycle performance for > 300 cycles.The capacity of graphite-based anodes increased steadily over the first ~20 cycles, and strongly depended on post-SLS processing methods and the charge/discharge rate. We attribute this to the properties of the binder used in the SLS process, and to electrode maturation processes.Printed separators were tested with either tape-cast NMC-based cathodes or additively manufactured anodes/cathodes, and were cycled continuously at rates between C/5 and 2C. Specific capacity was stable and consistent at all rates, and remained above 100 mAh g-1 with no observable capacity fade for any of the rates below 2C. Extended cycling at C/1.5 stable (or even increasing) capacity for approximately 85 cycles, at which point slight capacity fade began.We evaluated the cooperative functionality of printed components (i.e., printed electrodes and separators) in both half-cell and full cell configurations (this work is ongoing). Cells containing an SLS-fabricated separator and a screen-printed NMC cathode charged at C/10 and discharged at C/5 delivered reversible capacity ~160 mAh g-1 for 100 cycles.We will also present ongoing work that uses additive manufacturing to produce flexible batteries and batteries with conformal form-factors. Figure 1

Additively-Manufactured Electroactive Carbon-fiber/Phenolic Anodes for Structural Batteries and Grid Storage Craig Milroy, Tim Phillips, Joseph Beaman (Department of Mechanical Engineering, University of Texas, Austin).This presentation describes the electrochemical energy-storage properties of additively -manufactured anodes fabricated from carbon fibers and an electroactive phenolic resin, and demonstrates their utility for three important energy-storage applications:(1) additively-manufactured batteries(2) grid storage(3) structural batteriesPhenolic polymer resins are polymerized by reacting phenols with formaldehyde, and are used in a broad range of applications such as coatings, adhesives, and molded products. Although phenolic resins are technically thermosets, the melting point of most phenolics is lower than their cure (crosslinking) temperature; as a result, many phenolics are melt-processable and may therefore be used as thermoplastic binders for indirect selective laser sintering (SLS) additive manufacturing (AM) processes.Although the uncured phenolic compound is soft and melts at low temperature, the cured polymer has excellent strength/hardness, thermal stability, and chemical resistance/imperviousness. As such, phenolic resins are frequently used in building materials, and are therefore an excellent choice for structural battery applications.In addition, the phenol monomer that forms the basis of phenolic resins is an aromatic molecule with delocalized non-bonding electrons, which allows the hydroxyl moiety on the phenol to undergo reversible hydroxyl/quinine redox conversion. In addition, the polymerization process of phenolic monomers creates methylene bridges between phenol molecules, which preserves the electroactivity of the phenol molecule in its polymerized form. These properties have led to many reports of phenols as “natural” energy storage materials, since there are numerous biological sources of phenolic compounds.We observed the electroactivity of the cured phenolic (GP 5520) when using it as a thermoplastic binder in an indirect SLS fabrication process to produce additively-manufactured graphite anodes. To unambiguously measure the electroactivity of the cured phenolic, we fabricated electrodes by mixing phenolic powder in solid or dissolved form with non-electroactive conductive carbon fibers. The electrodes were fabricated via SLS and then cured to affix the electroactive phenol to the carbon fibers, which provided mechanical strength and served as a current collector for charge injection/extraction . The Figure depicts representative voltage profiles during galvanostatic discharge/charge testing of an SLS-fabricated composite electrode containing carbon fibers and phenolic, and indicates that the material is predisposed to function well as an anode, since the discharge occurs exclusively in a relatively narrow potential range below 1.0 V relative to the Li / Li+ equilibrium potential.The Figure also presents lgalvanostatic cycle performance of the SLS-fabricated electrodes at different rates. As expected, electrodes that were discharged at lower current density produced higher capacity. However, all electrodes exhibited a gradual maturation of capacity that is commonly observed in other electroactive polymers such as polypyrrole and polyanaline. The total number of cycles required to reach stable capacity was inversely proportional to the current density. Overall, the electrodes displayed consistent cycle performance once their discharge capacity stabilized; therefore, to address the observed electrode maturation process, and to definitively evaluate the rate-dependent cycle performance, we utilized rate-capability testing, beginning with low current for a few cycles at the beginning of each cell test, followed by a traditional rate-capability ladder to assess the dependence of capacity on previous cycling history. As shown in the Figure, these tests found that the electrodes produced 200 mAh/g of phenolic at 15 mA/g , and 100 mAh/g phenolic at 75 mA/g. Figure 1

Compressive performance of an arbitrary stiffness matched anatomical Ti64 implant manufactured using Direct Metal Laser Sintering

The main aim of this research work is to investigate the high-temperature cyclic corrosion performance of the wrought and direct metal laser sintered (DMLS) alloy 718 in the air and molten salts NaCl-90%Na2SO4 and three salt mixture (3SM) Na2SO4-10%V2O5-10%NaCl atmosphere for 120 h at 800°C. The microstructure of the wrought and DMLS alloy illustrated the austenitic and dendrite structure. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to evaluate the structure and phase constitutions of the scale. Visual and microstructural evaluation of the alloy post-exposure indicates that corrosion is more prevalent in molten salt conditions, when compared to air, and Cl-species induced the active oxidation in molten salt. The oxide film development and damage mechanism were detailed and explained by a cross-sectional investigation. Significant spalling and sputtering were also noticed in the S3 salt mixture. This might be attributed to the rapid formation of oxide scales by vanadate, followed by dissolution of the oxide in molten sulphate and chloride. The results divulged that both AM-built and wrought alloy exhibited the similar corrosion properties and both the alloys were undergone severe degradation in MS condition. Highlights Alloy 718 was fabricated successfully by the direct metal laser sintering (DMLS) method. Cyclic high-temperature oxidation and corrosion of the alloy were studied at 800°C. The oxidised sample exhibits a lower weight gain with no damage. Due to chlorination and sulfidation, the corroded samples exhibited more oxidation and susceptible.

Hybrid moulds are a novel approach for rapid tooling of injection moulds that combines conventional machining for the mould structure and rapid prototyping techniques for the moulding blocks (core and cavity). In this study, two routes were used for producing the moulding blocks: selective laser sintering of stainless steel-based powder (hard tool) and epoxy resin vacuum casting (soft tool). The experimental work was based on a complex tridimensional commercial part. The mouldings were made in polypropylene, and the processing performance was monitored online in terms of pressure and temperature at the impression. The performance of the moulding blocks was analysed in terms of thermal and cycle performance and structural integrity. The epoxy tooling route is more adequate for fine detailing than selective laser sintering but is not adequate for parts with extensive ribs or deep bosses. The structural integrity of the less costly epoxy composite can be compromised during ejection, this suggesting the need to evaluate the stress field by simulation at the design stage of the mould.

This review systematically explores the emerging use of food by-stream materials in 3D printing (3DP) applications, addressing the pressing need for sustainable resource utilization in the food sector. The review evaluates the potential of food by-products and waste, ranging from agricultural, animal, marine, microbial fermented biomass, and filamentous-fungi by-products to food consumption waste, for integration into 3DP techniques like fused deposition modeling, paste extrusion, direct ink writing, and selective laser sintering. Utilizing the PRISMA 2020 framework, a comprehensive literature analysis identified 80 relevant studies, categorized by material type and application. The findings indicate that plant-based by-stream materials encompassing sources like vegetable residues, fruit peels, nut and bean shells, and grain husks, dominate current 3DP research. These materials support biocomposite advancements across various fields, with notable applications in food-safe packaging, biomedical scaffolds, nutritious snacks, and sustainable construction materials. Several studies highlight significant improvements in mechanical strength, such as tensile and compressive performance, alongside enhanced biodegradability of nonedible printed products and nutrient content in edible printed products. Key process parameters, including extrusion speed, nozzle temperature, and layer thickness, have been optimized to accommodate the unique properties of these food by-stream materials, ensuring printing fidelity, smooth extrusion, and structural integrity, thereby maximizing their potential across diverse 3DP techniques and applications. This review highlights 3DP as a transformative approach in resource recovery, demonstrating how incorporating food by-stream materials aligns with circular economy goals by reducing waste and enabling eco-friendly production. By advancing customizable, nutrient-dense, and sustainable products, 3DP of food by-stream materials holds significant promise for addressing global food security and sustainability challenges.

Experimental and numerical studies on the compression responses of novel mixed lattice structures

High strength Aluminium alloys feature low densities, high strength‐to‐stiffness ratio, large ductility range and high fracture toughness, all attractive features for applications in industries such as automotive, aerospace and construction. To date, little attention has been given to the performance of 3D‐printed high strength Aluminium alloys such as Al7075 due to the inherent challenges in the additive manufacturing process. In this context, the present study reports material (tensile) and stub column (compression) tests on additively manufactured (AM) Al7075 square hollow sections (SHS). Both material and SHS samples were manufactured by Direct Metal Laser Sintering (DMLS), a laser powder‐bed fusion (L‐PBF) sub‐technology that uses metal powder as feedstock and a laser to fuse the feedstock layer by layer. Three newly develop set of process parameters that had successfully led to crack free medium sized samples were employed in this study. The effect of post processing treatments on the mechanical properties of printed Al7075 samples is investigated through the application of two heat treatments and a Hot Isostatics Pressing (HIP) treatment. A total of 33 material samples were manufactured and tested in tension, 6 of which in their as built condition and 27 subject to the above post processing treatments. The tensile test results showed that the Al7075 samples manufactured using the new set of parameters used is unable to produce specimens which can then develop their full tensile resistance. Nine square hollow tubes were subsequently manufactured utilising a selected heat treatment and tested in compression. All tubes successfully develop good compression performance and primarily exhibit failure due to local buckling, which led to the formation of a yield‐line‐like pattern of cracks, ultimately resulting in the specimens' failure.

In order to reduce stress shielding following a segmental bone replacement surgery requires stiffness matching strategies between the host bone and the implant are required. Carefully engineered implant geometry that can mimic the mechanical performance of the host bone is required to achieve this. The development of Additive Layer Manufacturing (ALM) techniques such as Direct Metal Laser Sintering (DMLS) allows for the fabrication of complex geometries that can achieve targeted mechanical performance. Consequently, this work introduces a sheathed Ti6Al4V additively manufactured tibial implant that mimics the circumferential anatomy of the host bone. Performance evaluation of the implant was carried using experimental and numerical technique under axial compression. Furthermore, the influence of sheathing strategy and sheath thickness on the compressive performance of the implant is parametrically analysed. The results of this study shows a promising sheathed implant that can replace a defective tibia bone segment. The implant is superior to conventional porous implants as it allows for easy implantation in surgical operation and allows for the reduction of stress shielding.

Compressive properties of hollow lattice truss reinforced honeycombs (Honeytubes) by additive manufacturing: Patterning and tube alignment effects

Lattice structures are widely used in the field of collisional energy absorption due to their flexible design and excellent energy absorption properties. In this study, chain lattice structures (CLSs) that can flexibly change their shapes after manufacturing were proposed, and their axial compression performance and energy absorption properties were investigated. The hollow octahedral CLS (HOLS), hollow sphere CLS (HSLS) and mixed CLS (MLS) prototypes with material of nylon 11 were prepared by selective laser sintering (SLS) technology, and quasi-static compression experiments were performed. The results from the experimental analysis were consistent with the simulation results, affirming the validity and accuracy of the simulation model. Moreover, it was concluded that the hollow octahedral cells have better mechanical properties. Therefore, we investigated the effects of cell diameter D, number of cell layers L and cell arrangement on the energy absorption characteristics of HOLS. In conclusion, CLSs exhibited remarkable energy-absorption properties, showcasing enhanced performance and holding significant promise for diverse applications.

Conventional uniform lattice structures are subject to non-uniform loads or concentrated loads alternating back and forth during service, which can no longer meet the refinement requirements. In this paper, SiCp/SiC gradient lattice structures are prepared by selective laser sintering (SLS) technology and polymer impregnation pyrolysis (PIP) process, and compression standard specimens with different tilt angles are prepared according to the structural model by changing the printing direction, to analyze the influence of the anisotropic properties of the materials due to the SLS molding technology on the load-bearing behaviour of the core rod, and to further study the mechanical properties of the gradient lattice structures and the Failure behaviour. The results show that: with the increase of the angle of printing direction, the compression performance of the densification specimen decreases gradually; the compression strength of the gradient lattice structure is 13.95 MPa. During compression, the core rods with tilt angles of 60° and 75° mainly exhibit shear failure and crushing failure, respectively. The theoretical and simulated compression strengths were 16.08 and 16.32 MPa, respectively. This paper provides a new insight into the research and application of gradient lattice structures.

Experimental and simulation study on effects of material and loading direction on the quasi-static compression behavior of re-entrant honeycomb structure

The cyclic performance of a novel piling system is presented in this article. It is composed of spun-cast ductile iron (SCDI) tapered pile fitted with a lower helix. The pile combines the durability of rough surface spun-cast ductile iron, the efficiency of tapered section and the construction advantages of helical piles. Five instrumented SCDI tapered helical piles and two straight helical piles were installed in sand and tested in cyclic compression and uplift. Effects of prior monotonic and cyclic tests on the piles’ cyclic performance were assessed. Finite element simulations of the tested piles were performed to evaluate the possible stiffness change during loading. The proposed pile exhibited enhanced cyclic compressive performance compared to straight shaft piles. Prior cyclic uplift loads had a negative effect on the proposed pile’s performance, whereas previous monotonic compression loading reduced its cyclic uplift displacement. Both tested configurations showed satisfactory cyclic uplift perfor...

Encapsulating ultrafine Fe3O4 nanoparticles into interconnected 3D multiporous carbon for superior Li-ion energy storage