Designing an energy absorber for automotive bumpers involves balancing low-speed and high-speed impacts to ensure safety, reduce repair costs, and meet regulatory standards. This study explores a novel design using multi-material 3D printing and structural optimization to fabricate a lightweight and cost-efficient energy absorber. The design effectively dissipates energy in low-speed collisions and minimizes force transmission in high-speed pedestrain impacts, helping to meet both safety and performance requirements. The energy absorber design combines 20% carbon fiber-reinforced acrylonitrile butadiene styrene (CF-ABS) and thermoplastic polyurethane (TPU) for optimal stiffness and flexibility. It uses 3D-printed lattice structures optimized through finite element simulations to help meet both low-speed and high-speed impact requirements. Full-scale energy absorbers were 3D-printed using optimized CF-ABS/TPU blends and tested under high-speed impact using the Flexible Pedestrian Legform Impactor (Flex-PLI). For fair comparison, a baseline bumper with a traditional triangular lattice structure, also 3D-printed from the same CF-ABS/TPU materials, was similarly tested. Interestingly, both the optimized and baseline 3D-printed energy absorbers showed nearly identical performance, successfully meeting injury limits. Their performances were also benchmarked against an injection-molded energy absorber. While both 3D-printed and injection-molded designs met injury limits, the 3D-printed absorber exhibited a higher tibia bending moment, indicating an opportunity for further optimization. A Techno-Economic Analysis compared the costs of producing energy absorbers using traditional manufacturing and 3D printing. The analysis highlighted that 3D printing offers cost benefits for low to medium production volumes, with the total cost per energy absorber at similar to $74, compared to traditional methods that become economical beyond 2000 units.

Biomass (e.g., pine sawdust, especially high-ash content pine sawdust) is commonly disposed of as waste. Combining biomass with polymers to make composite feedstocks for 3D printing has been explored as a method to reduce or repurpose the biomass waste. Although not all biocomposite properties are known, the wood-based polylactic acid (PLA) composite has promising qualities for applications in ecological settings. In this work, pine wood-PLA composite feedstock was used to 3D print supplemental roost structures for endangered tree-roosting bats, which often face a paucity of suitable naturally occurring roosts. This material combination was selected because it is estimated to degrade faster than the synthetic material systems that are used widely in supplemental bat roosting structures to aid in the conservation of tree roosting bats. The layered, rough surface created by the 3D printing process serves as a surface that bats can grip while roosting. Computer-aided design (CAD) models were generated based on natural roost structures, and a full-size bat house was successfully additively manufactured using a pellet-fed large-scale 3D printing system. The 3D printed hexagon exhibited a tensile strength of 22-23 MPa and a Young's modulus of 3202-3218 MPa in the x -direction. It has been demonstrated that the 3D printed bat house can be installed on a tree in a stable fashion. This successful demonstration of a bat roost manufactured using a bioderived composite should promote its use in other fish and wildlife structures and broader industrial applications such as construction and automobiles.

IntroductionCritically ill ECMO patients face high bleeding risks from anticoagulation and other factors. Although viscoelastic tests, like ROTEM, are widely used to assess hemostasis, evidence for their superiority over conventional coagulation tests (CCTs) is unclear. We assessed the prevalence of coagulopathy defined by ROTEM and CCT transfusion triggers, test concordance, and blood product use in bleeding ECMO patients.MethodsThis retrospective study included patients treated with ECMO at the Intensive Care Unit from April 1, 2020, to September 30, 2022, for whom ROTEM and CCTs were tested simultaneously to identify coagulopathy during bleeding. Coagulopathy and transfusion needs were assessed using the cut-offs from both methods.ResultsOf 88 patients, 34 (39%) had Clauss fibrinogen <1.5 g/L, and 21 (24%) had INR ≥1.8. Low FIBTEM A10, low EXTEM A10, and prolonged EXTEM CT were identified in 49 (56%), 43 (49%), and 36 patients (41%). EXTEM CT and INR were poorly associated, particularly for patients on VV-ECMO. FIBTEM A10 and Clauss fibrinogen showed a stronger relationship regardless of circuit type. For plasma and fibrinogen transfusions, ROTEM-based thresholds were more frequently met than CCT thresholds. Patients with abnormal ROTEM received more plasma and fibrinogen than those without [26/36 (72%) versus 21/52 (40%) and 45/49 (92%) versus 13/39 (33%), all p-values <0.01].ConclusionAbnormal ROTEM results were more frequent, often discordant with CCTs, and were associated with more plasma and fibrinogen transfusions in bleeding patients on ECMO. Further prospective studies are required to assess the potential clinical utility of ROTEM in ECMO settings.

Direct ink writing (DIW) is an extrusion-based form of 3D-printing that has gained popularity over the last decade. DIW uses thixotropic fluid extrusion to form a particular shape. In order to form stable structures, the rheology of the paste is important to allow for extrusion from the syringe, stability of the growing print, and prevention of unwanted seeping flow during jog moves. In this work, we use wood pulp as a bio-based filler that can provide shear thinning properties to the ink, which produces a stable ink for DIW processing. Additionally, the filler imparts improved mechanical and thermal performance compared to neat resin. The wood pulp provided the shear thinning behavior necessary for DIW printing, and pulp loadings greater than 6 wt%, provided sufficient yield stress so that the composite could self-support during printing. Nanoclay was utilized to further improve ink rheology and appearance to enable larger scale printing. Overall, this work showed successful DIW of an epoxy resin with a sustainable filler improving its stiffness and thermal properties and provides an avenue for further development of bio-based inks for DIW towards various applications.

Thermoforming of short-fiber reinforced thermoplastic sheets offers a viable pathway for producing lightweight composite components; however, inherent anisotropy in fiberreinforced sheets can limit structural performance under multidirectional loading. In this work, short carbon fiber, glass fiber, and hybrid fiber–reinforced PETG sheets were evaluated as candidate feedstock materials for thermoforming, with flexural and tensile testing performed both along the primary fiber direction and in the off-axis orientation to establish baseline stiffness, strength, and anisotropy. As expected, short carbon fiber PETG exhibited the highest stiffness and strength in the primary fiber direction, while all systems showed reduced performance in the off-axis direction. This off-axis performance reduction provides clear justification for the use of additive reinforcement when such thermoformed sheets are intended for structural applications. The intended manufacturing sequence involves thermoforming the reinforced sheet first, followed by the application of additively manufactured lattice reinforcement; therefore, the reinforcement strategy does not impose limitations on sheet formability during thermoforming. Post-forming lattice reinforcement significantly reduced load-normalized displacement by approximately 95–99% relative to non-reinforced sheets and improved weightnormalized stiffness by ~70%. These findings demonstrate that geometry-driven additive reinforcement can effectively compensate for off-axis property reductions in thermoformed PETG composites, enabling enhanced multidirectional structural performance without compromising manufacturability.

Large-Format Additive Manufacturing (LFAM) offers the ability to 3D print composites at multi-meter scale and high throughput by utilizing a screw-based extrusion system that is compatible with pelletized feedstock. As such, LFAM systems like the Big Area Additive Manufacturing (BAAM) system provide a pathway for incorporating AM techniques into industry-scale production. Despite significant growth in LFAM techniques and usage in recent years, typical Multi-Material (MM) techniques induce weak points at discrete material boundaries and encounter a higher frequency of delamination failures. A novel dual-hopper configuration was developed for the BAAM platform to enable in situ switching between material feedstocks that creates a graded transition region in the printed part. This research studied the influence of extrusion screw speed, component design, transition direction, and material viscosity on the transition behavior. Material transitions were monitored using compositional analysis as a function of extruded volume and modeled using a standard Weibull cumulative distribution function (CDF). Screw speed had a negligible influence on transition behavior, but averaging the Weibull CDF parameters of transitions printed using the same configurations demonstrated that designs intended to improve mixing increased the size of the blended material region. Further investigation showed that the relative difference and change in complex viscosity influenced the size of the blended region. These results indicate that tunable properties and material transitions can be achieved through selection and modification of composite feedstocks and their complex viscosities.

This study establishes material selection guidelines for localized additive reinforcement of fiber-reinforced polyethylene terephthalate glycol (PETG) composite sheets intended for thermoformed structural components. Three classes of PETG sheets, including neat PETG, short fiber-reinforced (SCF, SGF, and hybrid), and continuous fiber-reinforced (CCF and CGF) composites, were systematically evaluated to identify material architectures that provide an optimal balance between thermoformability, mechanical performance, and compatibility with localized additive lattice reinforcement. Based on the selected material systems, lattice structures were additively deposited to evaluate stiffness enhancement, interfacial bonding, and thermoforming feasibility within a convergent manufacturing framework. CCF sheets exhibited the highest flexural performance (∼860 MPa strength and ∼31.6 GPa modulus) but also the greatest spring-back, limiting thermoformability. In contrast, SCF sheets provided a favorable balance between stiffness (∼140 MPa flexural strength and ∼8.8 GPa modulus) and formability, reducing spring-back by ∼94% relative to CCF, while SGF sheets exhibited the lowest spring-back and the hybrid composites showed intermediate behavior. Localized lattice reinforcement reduced load-normalized displacement by up to ∼98%, and untreated substrates exhibited the highest lap shear strength (∼5.2 MPa) following additive deposition. Collectively, these findings demonstrate the potential of convergent manufacturing for thermoformed structural composite components requiring enhanced stiffness and dimensional stability.

Oak Ridge National Laboratory (ORNL) has developed a highly automated manufacturing process for thermoplastic composites that combines the benefits of Additive Manufacturing and Compression Molding (AM-CM) to produce high-performance functional composite structures at automotive production rates. The AM-CM process creates highly precise preforms by additively placing extruded fiber-filled polymers (with controlled fiber orientations and multi-material configurations) in the desired mold location before undergoing a secondary compression molding process immediately before the preform cools down. Preforms can be in the form of short, long-chopped, or continuous fiber-filled thermoplastic polymers (e.g., CF/GF-filled ABS, PC, LM-PAEK, etc.). The AM-CM process combines the benefits of controlled fiber alignment, that is only achievable in AM-printed parts with the classical CM process, which eliminates porosity and good surface finish. A preform created using AM-CM can integrate various materials to enable additional architectural functionalities, including over-molding, selective stiffening, and the incorporation of electrically or thermally conductive channels. All these advantages come with a fast part production cycle time. The AM-CM process can manufacture multi-material, multifunctional parts in under 3 min, starting from raw material (pellets) to the final product. The novel AM-CM process offers superior microstructural control and enhanced multi-functionality previously unattainable with any other traditional high-rate thermoplastic composite manufacturing method. This work covers the manufacturing concept, system development, materials and applications of AM-CM process in detail.

This study proposes a novel design for automotive bumper using optimized lattice structures and multi-materials to balance low-speed collision and high-speed pedestrian impact performance. Different blends of 20 % carbon fiber-reinforced acrylonitrile butadiene styrene with thermoplastic polyurethane were used to tailor material properties. The energy absorber features lattice structures with customized mechanical responses, created by varying the incline angle theta from 0 to 180 degrees. We conducted 576 finite element simulations on a half-scale model to optimize energy absorption and stiffness, leading to 66 optimized designs that met both low-speed and highspeed impact criteria. Two sub-scale optimized energy absorbers with different peak forces-both meeting low-speed impact requirements-were 3D printed and validated through drop-weight testing. The one with lower peak stress demonstrated a more compliant response, exhibiting approximately 90 % lower initial peak force and an increase in energy absorption of around 33 % (from 24 J to 32 J). Compared to the baseline triangular lattice, the optimized absorber increased energy absorption by 68 % from (19 J to 32 J) and reduced peak stress by 70 %. It also showed near-complete recovery with minimal fractures, making it suitable for repeated use. This design improves safety while offering a lightweight, durable, and cost-effective bumper system.

Composite joining typically involves multiple steps, such as drilling and surface treatment, as part of the manufacturing process, which leads to low throughput and long cycle times. In the present study, we demonstrated a macro-level mechanical interlocking (MI) based, rapid joining technique to assemble additively manufactured compression molded (AMCM) panels, enabling the production of parts larger than the mold dimensions. Composite panels made of 20 wt% short carbon fiber reinforced acrylonitrile butadiene styrene (CF/ ABS) were joined using MI features of various geometries, namely tree (TR), dovetail (Dov), rectangle 2 (Rect2), and rectangle 1 (Rect1), and their in-plane strength was evaluated. The resultant strength of the tested MI joints reached up to 74 % of the baseline tensile strength (i.e., the 'no joint' case). Observations from optical and scanning electron microscopy revealed inadequate polymer diffusion between the adherends, indicating that the joint strength was primarily derived from mechanical interlocking. Additionally, the fracture surfaces exhibited stress-whitening marks, which were characterized using differential scanning calorimetry (DSC). The increase in melting enthalpy suggested local stretching of polymer chains due to MI. Finite element analysis (FEA) indicated that the Rect1 MI feature, which generated the lowest stress concentration, outperformed the others in terms of joint strength, achieving 42 MPa. As a demonstration of the MI joining method, a battery box tray measuring 108 cm x 34 cm using a mold with an effective dimension of 36 cm x 34 cm successfully manufactured, resulting in a part with an area three times larger than the mold. This study presents a promising approach to improving composite joining techniques while minimizing production complexities.

OBJECTIVES:Trauma-induced coagulopathy (TIC) can be fatal but preventable if recognised early. With emerging uses of rotational thromboelastometry (ROTEM) to guide transfusions in trauma, patient outcomes with TIC-defined by initial ROTEM and conventional coagulation tests (CCTs) during massive haemorrhage protocol (MHP) activations were evaluated at a primary trauma centre in British Columbia. METHODS:This retrospective observational study included adult trauma patients requiring MHP from June 1, 2020, to May 31, 2022. TIC, defined by initial results including (1) ROTEM-based EXTEM A10 <40 mm, EXTEM CT >100 s, EXTEM ML30 >10%, FIBTEM A10 <10 mm; and (2) CCT-based INR ≥1.8, PTT ≥1.5 times of upper normal limit, platelets <50 x 109/L, and Clauss Fibrinogen <1.5 g/L, was assessed for its correlation with mortality. Modified Poisson regression was used to model 28-day mortality. RESULTS:Twenty-two of sixty-eight patients (32%) had abnormal ROTEM but normal CCTs. TIC defined by CCTs was associated with increased mortality [24 h: 5/13 (38%) vs. 5/55 (9%), p = 0.025; 28d: 8/13 (62%) vs. 11/55 (20%), p = 0.002]; compared to ROTEM, which was not [24 h: 7/35 (20%) vs. 3/33 (9%), p = 0.307; 28d: 11/35 (31%) vs. 9/33 (27%), p = 0.594], despite requiring significantly higher blood component transfusion within the first 4 and 24 h of MHP (p-values<0.05). CONCLUSIONS:ROTEM is more sensitive in identifying TIC. Patients with abnormal CCTs had a higher death rate, and those with abnormal ROTEM had no significantly increased mortality. A prospective study is required to assess the effects of ROTEM further.

This study utilized additively reinforced thermoforming (ART) to enhance the thermomechanical properties of polyethylene terephthalate glycol (PETG) sheet. ART materials were produced by overprinting PETG/carbon fiber filament (PETG/CF) on neat PETG sheets at varying conditions. The mechanical properties of the PETG sheet, PETG/CF, and ART materials were assessed, showing that ART exhibited superior tensile strength and modulus of elasticity. The tensile strength and modulus in the x-direction for ART at 265 degrees C were 57.32 f 2.9 MPa and 3.41 f 0.4 GPa, respectively, compared to 49.1 f 0.5 MPa and 1.92 f 0.09 GPa for neat PETG. Microstructural analysis revealed strong interfacial adhesion between layers, while thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and heat deflection temperature analysis provided insights into the ART material's thermoforming behavior, aiding design optimization for enhanced stiffness, reduced necking, and improved customization. This information can be used to design for the thermoforming operation.

The integration of additive manufacturing (AM) technology with compression molding (CM), has emerged as a high-performance composite manufacturing technology in recent years. In the AM-CM process, quickly deposited AM preform on a mold undergoes a rapid compaction cycle to fabricate structurally robust composite parts due to highly controlled fiber alignment (from AM) and reduced porosity (from CM). Currently, AMCM-based part size is limited by the size of the mold volume, thus posing a challenge to manufacture scalable parts. This work focuses on joining techniques developed to enable fast rate joining of short fiber-reinforced thermoplastic composite parts using the AM-CM process. Acrylonitrile butadiene styrene resin reinforced with 20 wt% short carbon fiber composites was printed onto a flat mold and pressed under a hydraulic press. Fabricated panels were joined by the (a) mechanical impression at the joining interface and (b) over-molded continuous carbon fiber (CCF) sheet. Tensile tests were performed to characterize the joining strength of both mechanical impression-based joints and CCF over molded joints. Among the mechanical impression-based joints, a U-shape channel allowed the fibers to flow between two joint parts, and 280 % increased mechanical properties were observed. The continuous carbon fiber-based over molded joint CCF showed 350 % increase in tensile strength compared to the butt joints.

There has been growing interest in integrating bio-derived composites into Large-format additive manufacturing (LFAM) feedstocks to reduce the use of petroleum-derived materials and reduce the overall carbon footprint of LFAM. However, these materials present unique challenges during manufacturing due to their variability, which can lead to unintended deformations and failures attributable to suboptimal process conditions. While numerical modelling has been extensively employed to simulate numerous manufacturing processes, its application in LFAM with bio-derived composites remains limited. This study addresses this gap by systematically developing a numerical model to simulate the LFAM process using bio-based materials, specifically wood fiber-reinforced polylactic acid (PLA/WF). Experimental investigations were conducted to characterise the thermal and mechanical properties of additively manufactured PLA/WF specimens. Numerical simulations were performed to predict temperature profiles and deformations during LFAM. The effect of varying infill patterns, internal structures, and tool paths on the temperature distribution and deformation of printed parts was explored using the developed model. This article aims to advance the utilisation of bio-derived composites in LFAM systems and provide a comprehensive understanding of the LFAM process. The findings offer valuable insights for optimising process parameters and enhancing the performance of LFAM with bio-based composites.

Electroimpact inc. has developed a new additive manufacturing process involving continuous fiber reinforcement along with high-strength thermoplastics. A unique part of this process includes using additive manufacturing to print a base geometry that is then used as a tool for continuous fiber placement. Ideally the tool should be disposable and cost effective. After printing the base tool, continuous fiber is printed on top of the tool using a secondary additive head on the same system to create the final printed part. After continuous fiber printing is completed, the tool is removed and disposed of to leave only the final desired structure. Materials used for the base tool have several requirements that must be met in order to complete this process. First, the material must be rigid and strong enough to support the loads from the secondary printing operation (continuous fiber printing). In addition, the material must be able to adhere to the secondary process material as well be capable of being removed such that the only remaining structure is continuous fiber composite. Using innovative soluble materials allows for parts to be produced through additive with molds that are produced as non-reusable one-off shapes and sizes.

Prior studies have suggested that immune thrombotic thrombocytopenic purpura (iTTP) may display seasonal variation; however, methodologic limitations and sample sizes have diminished the ability to perform a rigorous assessment. This 5-year retrospective study assessed the epidemiology of iTTP and determined whether it displays a seasonal pattern. Patients with both initial and relapsed iTTP (defined as a disintegrin and metalloprotease with thrombospondin type motifs 13 activity <10%) from 24 tertiary centers in Australia, Canada, France, Greece, Italy, Spain, and the US were included. Seasons were defined as: Northern Hemisphere-winter (December-February); spring (March-May); summer (June-August); autumn (September-November) and Southern Hemisphere-winter (June-August); spring (September-November); summer (December-February); autumn (March-May). Additional outcomes included the mean temperature in months with and without an iTTP episode at each site. A total of 583 patients experienced 719 iTTP episodes. The observed proportion of iTTP episodes during the winter was significantly greater than expected if equally distributed across seasons (28.5%, 205/719, 25.3%-31.9%; p = .03). Distance from the equator and mean temperature deviation both positively correlated with the proportion of iTTP episodes during winter. Acute iTTP episodes were associated with the winter season and colder temperatures, with a second peak during summer. Occurrence during winter was most pronounced at sites further from the equator and/or with greater annual temperature deviations. Understanding the etiologies underlying seasonal patterns of disease may assist in discovery and development of future preventative therapies and inform models for resource utilization.

Realizing topological superconductivity by integrating high-transition-temperature (TC) superconductors with topological insulators can open new paths for quantum computing applications. Here, a new approach is reported for increasing the superconducting transition temperature ( T C onset ) $( {T_{\mathrm{C}}^{{\mathrm{onset}}}} )$ by interfacing the unconventional superconductor Fe(Te,Se) with the topological insulator Bi-Te system in the low-Se doping regime, near where superconductivity vanishes in the bulk. The critical finding is that the T C onset $T_{\mathrm{C}}^{{\mathrm{onset}}}$ of Fe(Te,Se) increases from nominally non-superconducting to as high as 12.5 K when Bi2Te3 is replaced with the topological phase Bi4Te3. Interfacing Fe(Te,Se) with Bi4Te3 is also found to be critical for stabilizing superconductivity in monolayer films where T C onset $T_{\mathrm{C}}^{{\mathrm{onset}}}$ can be as high as 6 K. Measurements of the electronic and crystalline structure of the Bi4Te3 layer reveal that a large electron transfer, epitaxial strain, and novel chemical reduction processes are critical factors for the enhancement of superconductivity. This novel route for enhancing TC in an important epitaxial system provides new insight on the nature of interfacial superconductivity and a platform to identify and utilize new electronic phases.

Large format additive manufacturing (LFAM) necessitates the use of short fiber thermoplastic composites, such as carbon fiber filled acrylonitrile butadiene styrene, to enable printing. Currently, when LFAM parts are machined into their final shape, the machining scrap (i.e., small flake like particles and offcuts) is landfilled. Previous studies have demonstrated the viability of recycling end-of-life LFAM parts by shredding and optionally re-compounding the material back into pellets. However, there is little understanding of the value and performance of recycled material made from LFAM machining scrap, which if pursued could motivate more broad recycling of this waste stream. In this study, recycled in-process machining scrap is explored as an LFAM feedstock source. Herein, it is found that the primary degradation mechanism of the recycled material is significant fiber length attrition during surface machining. While this fiber attrition negatively impacts the mechanical performance of the material in the print direction, it seems that the changes in processing behaviors and print quality, namely the surface roughness of the printed structure associated with shorter fiber lengths, is beneficial to interlayer adhesion. The tensile strength and elastic modulus of the recycled material, in the print direction, decreased 11% and 31% respectively compared to the pristine material. However, in the layer-wise direction it was found that the recycled material exhibited no significant change in elastic modulus and a significant 21% increase in tensile strength – a surprising result. This work indicates that machining waste could be a viable material stream for recycled LFAM feedstock materials.