3D-printed Specimens Research Articles

Development of Dynamic Four-Dimensional Printing Technology for Patterned Structures by Applying Microcellular Foaming Process.

Four-dimensional (4D) printing adds the dimension of time to 3D-printed specimens, causing movement when external stimuli are applied. This movement enables applications across various fields, including the soft robotics, aerospace, apparel, and automotive industries. Traditionally, 4D printing has utilized special materials such as shape-memory polymers (SMPs) or shape-memory alloys (SMAs) to achieve this movement. This study explores a novel approach to 4D printing by applying microcellular foaming processes (MCPs) to 3D printing. This study primarily aims to design and fabricate patterned specimens using common materials, such as PLA, through 3D printing and to analyze their dynamic behavior under various foaming conditions. To demonstrate the potential applications of this technology, the degree of bending was measured by controlling the patterning and foaming conditions. The 3D-printed specimens with microcellular foaming exhibited predictable deformations owing to the asymmetric expansion caused by differential gas saturation. The results confirm that 4D printing can be realized using conventional materials without the need for smart materials and can introduce foaming processes as a new external stimulus. This study highlights the potential of combining 3D printing with microcellular foaming for advanced 4D printing applications.

Flexural properties of additive manufactured resin designated for interim fixed dental prosthesis: Effect of nanoparticles, build direction, and artificial aging

ObjectiveThis study investigates the flexural strength and elastic modulus of three-dimension (3D) printed interim resin (ASIGA) incorporating zirconium dioxide (nano-ZrO2) and silicon dioxide (nano-SiO2) nanoparticles (NPs) with different build direction and after artificial aging. MethodsThree hundred 3D-printed specimens were used for testing. Groups were modified with nano-ZrO2 or nano-SiO2 at concentrations of 0.5 wt% or 1 wt% and an unmodified control group remained unmodified (n = 10). The bar-shaped specimens (25 × 2 × 2 mm) were printed at 0, 45, and 90 degree orientations. Flexural properties were assessed using a universal testing machine. The study employed various analyses to assess material properties and bonding. ResultsThe flexural strength was significantly improved (P<0.001) by the inclusion of nano-ZrO2 or nano-SiO2, with a maximum value of 61.8 ± 4.3 MPa with 1 wt% nano-ZrO2 at 45° build direction. The highest elastic modulus value observed was 998.2 ± 91.2 MPa with 0.5 wt% nano-SiO2 at 90° build direction. Build direction, NP type, and NP concentration all had a statistically significant combined effect on flexural strength and elastic modulus (P=0.003*, P=0.045), respectively. ConclusionIncorporation of nano-SiO2 and nano-ZrO2 increased the flexural properties of the interim resin used in 3D printing. Following artificial aging, all the flexural property values in the modified groups showedminimal reduction regardless of the nanoparticle concentration, while the unmodified control group showed a significant reduction. Before and after artificial aging, samples at a 0 degree build direction had a considerably higher flexural strength, although the highest elastic modulus values were found in the 90 degree group. The findings underscore the potential of nanocomposites in strengthening interim dental restorations, offering promising advancements for clinical practice.

Enhancing Clay-Based 3D-Printed Mortars with Polymeric Mesh Reinforcement Techniques.

Additive manufacturing (AM) technologies, including 3D mortar printing (3DMP), 3D concrete printing (3DCP), and Liquid Deposition Modeling (LDM), offer significant advantages in construction. They reduce project time, costs, and resource requirements while enabling free design possibilities and automating construction processes, thereby reducing workplace accidents. However, AM faces challenges in achieving superior mechanical performance compared to traditional methods due to poor interlayer bonding and material anisotropies. This study aims to enhance structural properties in AM constructions by embedding 3D-printed polymeric meshes in clay-based mortars. Clay-based materials are chosen for their environmental benefits. The study uses meshes with optimal geometry from the literature, printed with three widely used polymeric materials in 3D printing applications (PLA, ABS, and PETG). To reinforce the mechanical properties of the printed specimens, the meshes were strategically placed in the interlayer direction during the 3D printing process. The results show that the 3D-printed specimens with meshes have improved flexural strength, validating the successful integration of these reinforcements.

Data-driven prediction of strain fields in auxetic structures and non-contact validation with mechanoluminescence for structural health monitoring

Recent advancements in 3D printing technology have significantly enhanced the potential of auxetic structures, which are notable for their negative Poisson&amp;rsquo;s ratio, particularly in applications such as sensor technology and structural health monitoring. Central to the performance of these structures is the accurate estimation of the effective strain parameter, a critical metric for assessing structural integrity. However, as structural complexity increases, estimating this parameter becomes increasingly challenging. The fabrication and real-world validation of these structures are equally important challenges. This paper introduces two key innovations for the practical application of auxetic structures. First, we present a multi-kernel hierarchical deep neural network that leverages finite element simulation data to accurately predict effective strain fields in complex auxetic configurations. This model architecture not only reduces the number of parameters requiring training but also enhances feature learning and generalization capabilities, achieving over 90% accuracy in predicting strain fields. Second, we validate these predictions using a 3D-printed specimen embedded with mechanoluminescent (ML) particles. This approach enables direct, non-contact visualization of strain in real-time, offering high spatial and temporal resolution. The alignment observed between predicted and observed strain concentration areas demonstrates the efficacy of integrating ML technology into auxetic designs. This integration significantly improves the reliability and diagnostic capabilities of advanced structural systems.

Extreme roughness reduction and ultrafine quality of innovative dual function material extrusion 3D printer

PurposeThis paper aims to use hybrid manufacturing (HM) to overcome several drawbacks of material extrusion three-dimensional (3D) printers, such as low dimension ranging from 0.2 to 0.5 µm, resulting in a noticeable staircase effect and elevated surface roughness.Design/methodology/approachSubtractive manufacturing (SM) through computer numerical control milling is renowned for its precision and superior surface finish. This study integrates additive manufacturing (AM) and SM into a single material extrusion 3D printer platform, creating a HM system. Two sets of specimens, one exclusively printed and the other subjected to both printing and milling, were assessed for dimension accuracy and surface roughness.FindingsThe outcomes were promising, with postmilling accuracy reaching 99.94%. Significant reductions in surface roughness were observed at 90° (93.4% decrease from 15.598 to 1.030 µm), 45° (89% decrease from 26.727 to 2.946 µm) and the face plane (71% decrease from 12.176 to 3.535 µm).Practical implicationsThe 3D printer was custom-built based on material extrusion and modified with an additional milling tool on the same gantry. An economic evaluation based on cost-manufacturing demonstrated that constructing this dual-function 3D printer costs less than US$560 in materials, offering valuable insights for researchers looking to replicate a similar machine.Originality/valueThe modified general 3D printer platform offered an easy way to postprocessing without removing the workpiece from the bed. This mechanism can reduce the downtime of changing the machine. The proven increased dimension accuracy and reduced surface roughness value increase the value of 3D-printed specimens.

Effect of nanodiamonds surface deposition on hydrophilicity, bulk degradation and in-vitro cell adhesion of 3D-printed polycaprolactone scaffolds for bone tissue engineering

This study was designed to deposit nanodiamonds (NDs) on 3D-printed poly-ϵ-caprolactone (PCL) scaffolds and evaluate their effect on the surface topography, hydrophilicity, degradation, andin-vitrocell adhesion compared to untreated PCL scaffolds. The PCL scaffold specimens were 3D-printed by fused deposition modeling (FDM) technique with specific porosity parameters. The 3D-printed specimens' surfaces were modified by NDs deposition followed by oxygen plasma post-treatment using a plasma focus device and a non-thermal atmospheric plasma jet, respectively. Specimens were evaluated through morphological characterization by field emission scanning electron microscope (FESEM), microstructure characterization by Raman spectroscopy, chemical characterization by Fourier transform infrared (FTIR) spectroscopy, hydrophilicity degree by contact angle and water uptake measurements, andin-vitrodegradation measurements (n= 6). In addition,in-vitrobone marrow mesenchymal stem cells adhesion was evaluated quantitatively by confocal microscopy and qualitatively by FESEM at different time intervals after cell seeding (n= 6). The statistical significance level was set atp⩽ 0.05. The FESEM micrographs, the Raman, and FTIR spectra confirmed the successful surface deposition of NDs on scaffold specimens. The NDs treated specimens showed nano-scale features distributed homogeneously across the surface compared to the untreated ones. Also, the NDs treated specimens revealed a statistically significant smaller contact angle (17.45 ± 1.34 degrees), higher water uptake percentage after 24 h immersion in phosphate buffer saline (PBS) (21.56% ± 1.73), and higher degradation rate after six months of immersion in PBS (43.92 ± 0.77%). Moreover, enhanced cell adhesion at all different time intervals was observed in NDs treated specimens with higher nuclei area fraction percentage (69.87 ± 3.97%) compared to the untreated specimens (11.46 ± 1.34%). Surface deposition of NDs with oxygen-containing functional groups on 3D-printed PCL scaffolds increased their hydrophilicity and degradation rate with significant enhancement of thein-vitrocell adhesion compared to untreated PCL scaffolds.

Compressive behavior of thermoplastic polyurethane with an active agent foaming for 3D-printed customized comfort insoles

The primary objective of this study was to investigate the compressive behavior of 3D-printed specimens made of a thermoplastic polyurethane filament, specifically colorFabb varioShore TPU, which incorporates a foaming agent. The foaming technology makes it possible to manipulate 3D prints' properties by adjusting process parameters that affect the level of expansion, such as printing temperature, printing speed or flow ratio. This capability opens new possibilities for 3D-printed personalized foot orthotics or for static comfort-oriented applications by tailoring the stiffness of the print based on the application requirements. Since infill density and infill pattern also affect the compressive characteristics of 3D prints, this research took these two parameters into account as independent variables, alongside the printing temperature. Thus, the specimens with printing temperatures set at 190 °C, 220 °C, and 240 °C, gyroid and honeycomb patterns, and infill variations from 10 % to 35 % in 5 % increments were experimentally investigated in compression testing. The evaluation was conducted to determine the influence of these factors on the stiffness of prints at 10 % and 20 % strains, in accordance with established standard. The findings had an important practical value as they provide data for adjusting the variable stiffness based on peak plantar pressure measurement data when developing tailored foot orthoses (insoles), which was the second objective of the research. The most influential factor affecting the compressive strength was the printing temperature, followed by infill density and pattern type. The difference in compression modulus between 10 % and 20 % strains did not exhibit statistical significance. Moreover, the main effects plots indicated minimal variations in compression modulus effects at 220 °C and 240 °C, whereas an important difference was observed at 190 °C printing temperature, which was confirmed by scanning electron microscopy investigations showing foamed layers at 220 °C and unfoamed layers at 190 °C. Furthermore, interaction plots revealed no significant interaction effect among the studied variables. Additionally, a comparison of samples’ sizes and densities before and two months after testing indicated no observable modifications When applied to custom orthotics (five pairs of insoles were customized and tested), the experimental findings documented variations in the reduction and distribution of peak plantar pressure based on the infill variability.

Lean-and-Green Fractional Factorial Screening of 3D-Printed ABS Mechanical Properties Using a Gibbs Sampler and a Neutrosophic Profiler

The use of acrylonitrile butadiene styrene (ABS) in additive manufacturing applications constitutes an elucidating example of a promising match of a sustainable material to a sustainable production process. Lean-and-green datacentric-based techniques may enhance the sustainability of product-making and process-improvement efforts. The mechanical properties—the yield strength and the ultimate compression strength—of 3D-printed ABS product specimens are profiled by considering as many as eleven controlling factors at the process/product design stage. A fractional-factorial trial planner is used to sustainably suppress by three orders of magnitude the experimental needs for materials, machine time, and work hours. A Gibbs sampler and a neutrosophic profiler are employed to treat the complex production process by taking into account potential data uncertainty complications due to multiple distributions and indeterminacy issues due to inconsistencies owing to mechanical testing conditions. The small-data multifactorial screening outcomes appeared to steadily converge to three factors (the layer height, the infill pattern angle, and the outline overlap) with a couple of extra factors (the number of top/bottom layers and the infill density) to supplement the linear modeling effort and provide adequate predictions for maximizing the responses of the two examined mechanical properties. The performance of the optimal 3D-printed ABS specimens exhibited sustainably acceptable discrepancies, which were estimated at 3.5% for the confirmed mean yield strength of 51.70 MPa and at 5.5% for the confirmed mean ultimate compression strength of 53.58 MPa. The verified predictors that were optimally determined from this study were (1) the layer thickness—set at 0.1 mm; (2) the infill angle—set at 0°; (3) the outline overlap—set at 80%; (4) the number of top/bottom layers—set at 5; and (5) the infill density—set at 100%. The multifactorial datacentric approach composed of a fractional-factorial trial planner, a Gibbs sampler, and a neutrosophic profiler may be further tested on more intricate materials and composites while introducing additional product/process characteristics.

Compressive Properties of Additively Manufactured Metal-Reinforced PLA and ABS Composites.

The development of multi-material filaments has enabled fused filament fabrication-based additive manufacturing to address demand for high-performance lightweight multifunctional components. In this study, polylactic acid (PLA) and acrylonitrile butadiene styrene based filaments with metallic reinforcements of magnetic iron (MI), stainless steel (SS), bronze (Br), copper (Cu), Bismuth (Bi), and Tungsten (W) were investigated to elucidate their complex processing-structure-property relationships. The microstructure of 3D-printed materials were characterized by microscopy and analyzed to determine the metal cross-sectional area percentage and the relationship between metal reinforcement, the polymer matrix, and porosity. Compression testing was conducted in directions parallel and perpendicular to the build direction in order to evaluate the effect of orientation and metal reinforcement on the mechanical properties. 3D-printed specimens experienced either fracture through print layers or layer-wise interfacial rupture for loads applied perpendicular and parallel to the print layers, respectively. A dependence of yield strength on loading orientation was observed for Br-PLA, Cu-PLA, SS-PLA, Bi-ABS, and W-ABS; however, MI-PLA and pure ABS specimens did not exhibit this sensitivity. Metal reinforcement also influenced the magnitude of compressive yield strength, with MI-PLA and SS-PLA demonstrating increased strength over Br-PLA and Cu-PLA, while ABS demonstrated increased strength over Bi-ABS and W-ABS. These results demonstrate the importance of considering orientation in printing and applications, the trade-off between various metallic reinforcements for added multifunctionality, and the potential of these tailored polymer composites for novel 3D-printed structures.

Variations in the Thermomechanical and Structural Properties during the Cooling of Shape-Memory R-PETG.

One of the useful features of 3D-printed specimens of recycled polyethylene terephthalate glycol (R-PETG) is the ability to repetitively develop free recovery as well as the work-generating, shape-memory effect. This behavior is enabled by the R-PETG's capacity to stiffen during cooling, thus allowing for a new temporary shape to be induced. Aiming to devise an explanation for the polymer's stiffening, in this study, the variation in some of the R-PETG's parameters during cooling are emphasized and discussed. The evolution of an R-PETG filament's shape was monitored during room-temperature-bending heating-cooling cycles. Straight-shape recovery and the complete loss of stiffness were observed at the start and the end of heating, respectively, followed by the forced straightening of the filament, performed by the operator, around 40 °C, during cooling. The tests performed by dynamic mechanical analysis disclosed the rise of the storage modulus (E') after 100 °C heating followed by either liquid-nitrogen- or air-cooling to room temperature, in such a way that E' was always larger after cooling than initially. Static tests emphasized a peculiar stress variation during a heating-cooling cycle applied in air, within the heating chamber of the tensile testing machine. Tensile-failure tests were performed at -10 °C at a rate of 100 mm/min, with specimens printed at various deposition directions between 10 and 40° to the transversal direction. The specimens printed at 40°, which had the largest ultimate strains, were broken with tensile rates between 100 and 500 mm/min. Deformation rate increase favored the shift from crazing to delamination failure modes. The correlation between the structural changes, the sharp E' increase on heating, and the stiffening induced by cooling represents a novel approach that enables the use of 3D-printed R-PETG for the fabrication of the active parts of low-priced lightweight resettable actuators.

Synthesis and Characterization of Furan-Based Methacrylate Oligomers Containing the Imine Functional Group for Stereolithography.

Herein, a furan-based methacrylate oligomer (FBMO) featuring imine functional groups was synthesized for application in stereolithography. The preparation involved the imination reaction of 5-hydroxymethylfurfural (5-HMF) and amino ethanol. Utilizing 5-HMF as a sustainable building block for furan-based polymers, FBMO was formulated and subsequently integrated into photosensitive resin formulations along with methacrylate-containing diluents, such as PEGDMA and TEGDMA. The synthesized furan-based methacrylate oligomers underwent comprehensive characterization using FTIR, 1H NMR spectroscopy, and size exclusion chromatography. The impact of methacrylate-containing diluents on various properties of the formulated resins and the resulting 3D-printed specimens was systematically evaluated. This assessment included an analysis of rheological behavior, printing fidelity, mechanical properties, thermal stability, surface morphology, and cytotoxicity. By adjusting the ratios of FBMO to methacrylate-containing diluents within the range of 50:50 to 90:10, the viscosity of the resulting resins was controlled to fall within 0.04 to 0.28 Pa s at a shear rate of 10 s-1. The 3D-printed specimens exhibited precise conformity to the computer-aided design (CAD) model and demonstrated compressive moduli ranging from 0.53 ± 0.04 to 144 ± 6.70 MPa, dependent on the resin formulation and internal structure. Furthermore, cytotoxicity assessments revealed that the 3D-printed specimens were noncytotoxic to porcine chondrocytes. In conclusion, we introduce a new strategy to prepare the furan-based methacrylate oligomer (FBMO) and 3D-printed specimens with adjustable properties using stereolithography, which can be further utilized for appropriate applications.

Thermal and manufacturing properties of hollow-core 3D-printed elements for lightweight facades

High-performance facades play an important role in achieving Net-Zero goals by 2050. As a facade manufacturing technology, 3D printing offers the opportunity to create site-specific and high-performance building envelopes. In this manuscript, the thermal performance of components fabricated with different Material Extrusion methods is studied experimentally, and the fabrication time is calculated, thereby examining both performance and fabrication viability. More specifically, this manuscript investigates the thermal performance of 3D-printed facades using Hollow-Core 3D printing (HC3DP) and explores the potential of this novel approach in creating thermally insulating, lightweight, and translucent building envelopes. The research compares the thermal resistance of HC3DP specimens to conventional material extrusion methods, such as desktop 3D printers, and granular-based, large-scale pellet extrusion. Different methods are used to determine the thermal resistance of specimens, including the dynamic thermal conductivity measurement for the desktop 3D-printed (3DP) specimens, and the steady-state hot box heat flux meter approach for HC3DP. The results demonstrate that HC3DP enables lower Thermal transmittance (U-value)s at lighter weight and faster printing speed, making it a promising avenue for further research. Additionally, the combination of HC3DP with aerogel is shown to create ultra-lightweight and thermally insulating 3D-printed facade elements. The potential of this new facade technology is also highlighted in comparison with established facade systems. All in all, the manuscript provides insights into the thermal performance of 3D-printed facades at different printing resolutions and emphasizes the importance of printing time and material consumption in determining the most promising 3D printing approach for lightweight and thermally insulating facades.

A lightweight AuxHex zero Poisson's ratio pressure-resistant sandwich cylindrical shell and its load-bearing and sound insulation behaviors: Design, simulation and experiment

Pressure-resistant hulls are critical components in underwater vehicles and submersible systems. Exploring novel materials and structures has been a growing trend to overcome conventional structural limitations and achieve multifunctionality. Mechanical metamaterials with tunable physical properties can offer promise. Therefore, this study focuses on designing and fabricating a pressure-resistant sandwich cylindrical shell using AuxHex zero Poisson's ratio (ZPR) mechanical metamaterials. Structural optimization is employed to develop a lightweight AuxHex ZPR unit cell to withstand deep-sea pressure. Mechanical and acoustic experiments were then conducted on a 3D-printed Titanium alloy specimen, and the rationality of numerical modeling was validated by the experimental results. Load bearing and sound insulation properties of the designed ZPR sandwich cylindrical shell have been numerically analyzed and compared with its geometrically similar positive Poisson's ratio (PPR) and negative Poisson's ratio (NPR) shells. The designed ZPR structure that yields a mass density ratio of 0.569 g/cm³ can withstand hydrostatic pressure at 1000 m depths without strength or buckling damage, while adequate reserve buoyancy can be maintained. The submerged ZPR shell structure can provide superior protection for inner spaces and its average sound transmission loss (STL) is more than 5 dB higher than the PPR and NPR shells.

The Impact of Internal Structure Changes on the Damping Properties of 3D-Printed Composite Material

This article investigates the impact of changes in the internal structure of composite materials on their dynamic properties. The present research focuses on 3D-printed specimens with different reinforcement fiber arrangements. The specimens are printed on a Markforged Mark Two 3D printer. The base material is nylon filled with chopped carbon fibers (Onyx) and the reinforcement is in the form of long carbon, glass and Kevlar fibers. The experiment is carried out by the impact method. The principle of this method is to expose the specimen to a short impulse of force while monitoring its frequency response. The obtained results determine the natural frequencies and internal damping of the individual structures. We found that the highest damping is achieved by specimens with glass and Kevlar fibers in 45°, 90° and ±45° configurations. On the other hand, the lowest damping is achieved by specimens with carbon fibers and 0° and 0°,90° configurations. Also, the specimens with circumferential reinforcement show lower damping coefficient values. The knowledge and results of this work can be used in the development of new components; for example, in the transport industry, where the low weight and sufficient strength of components are important factors. These components have to absorb vibrations from various sources, such as motors and external influences.

Experimental and numerical study on the fatigue behaviour of pre and post heat treated additively manufactured SS 316L specimens

The success of 3D printing relies on developing components with desired strength that heat treatment processes can further improve. While SS 316L is a widely used structural material for several industrial applications, the fatigue behaviour of its 3D-printed version is investigated herein. The low cycle fatigue (LCF) behaviour ofheat-treated (HT)3D-printed SS 316L specimens was carried out and compared with thewithout heat-treated (WHT)specimens thereof. The heat treatment considerably affected its LCF behaviour, which can be attributed to the microstructural changes post heat treatment. The cyclic softening is observed in both HT and WHT specimens. However, the degree of softening is lower (12.35 %) for HT compared to WHT specimens (25.30 %) and 62 % higher fatigue life for HT compared to WHT specimens. Further, the hardness values obtained are 176 and 169 HV for WHT and HT, respectively, while it is 238 and 223 HV for the same, before and after fatigue tests. Fractography revealed fewer pores and reduced fatigue striations in the HT specimens. Considering the Chaboche non-linear model, finite element modelling was employed to capture the specimens’ fatigue behaviour. The proposed model is found to be suitable for predicting the cyclic behaviour of 3D-printed austenitic steels.

Impact response of textile-reinforced 3D printed concrete panels

This study assessed the impact response of 3D-printed textile-reinforced concrete for structural applications of 3D concrete printed structures, where impact is a significant load case. To study the impact response, two layers of AR-glass and two layers of carbon textile-reinforced 3D-printed high-strength concrete panels were investigated experimentally under low-velocity impacts from drop weights, respectively. The effect of textile reinforcement on the impact behaviour was compared with unreinforced printed specimens. The specimens were subjected to increasing levels of impact load until the failure was observed. The effect of textile reinforcement on the impact resistance, cumulative energy absorption capacity and failure pattern of printed specimens were investigated and compared with their mould-cast counterparts. To understand the effect of textile reinforcement on the printed and mould-cast panel specimens, a quasi-static flexural test was performed to evaluate the load vs deformation behaviour. The test results from the quasi-static flexural test showed that the incorporation of textile reinforcement improved the first crack strength by about 40 % and enhanced post-peak behaviour for both printed and mould-cast specimens. Further, providing carbon textile reinforcement significantly improved the impact resistance by 75 % when compared to AR glass textile-reinforced specimens due to the higher stiffness and better strain-hardening behaviour. Moreover, the effect of textile reinforcement on enhancing the energy absorption capacity of 3D-printed specimens was more evident at higher impact velocities. The cumulative energy absorption capacity of carbon textile-reinforced specimens was observed to be 60 % higher compared to AR glass textile-reinforced specimens. During high-velocity impacts, the textile reinforcement was observed to improve damage distribution by enhancing the bridging between the interlayers. The damage condition at failure showed that AR-glass textile-reinforced printed and mould-cast specimens showed severe punching failure on the compression face and widened cracks and spalling on the tension face. However, carbon textile reinforcement enhanced the impact resistance, thus showing multiple cracks and reduced spalling on the tension face even after multiple impacts. Overall, the impact performance of 3D-printed textile-reinforced concrete panels showed high-level impact resistance.

Support medium development for 3D printing natural rubber latex via direct ink writing in the support bath technique

The direct manufacturing of rubber products from natural rubber latex through 3D printing, particularly extrusion in air, faces challenges in creating intricate shapes. Research suggests that utilizing 3D printing with extrusion in a support medium, known as direct ink writing (DIW), is effective for crafting complex-shaped rubber products. However, few studies have explored 3D printing natural rubber as a support medium. This study focuses on formulating a support medium for the DIW printing of natural rubber by incorporating triethanolamine (TEA) and alcohol in varying proportions. Key characteristics, such as viscosity, were assessed for each formulation, along with essential printing parameters, such as speed and flow rate. A suitable support liquid consisting of TEA (2.5 g), alcohol (160 g), Carbopol (1.5 g), and water (200 g) was determined for DIW printing natural rubber. The optimal settings were determined to be a nozzle size of 0.85 mm, a speed of 30 mm/s, and a flow rate of 30 mm3/s. Comparative results from the forming process indicate that 3D-printed rubber specimens exhibit poorer mechanical properties than traditionally molded specimens, owing to material uniformity. The vulcanized rubber system with the EV pattern exhibited superior mechanical characteristics. The developed support medium for DIW printing shows potential for use in intricate natural rubber products; however, further exploration of additional parameters is crucial for advancing complex-shaped natural rubber manufacturing using 3D printers.

Sustainable and eco-friendly 3D printing filament fabricated from different recycled solid wastes and evaluate its impact on interior and furniture design

A designer's work is based on creativity, innovation, and fresh ideas therefore, they are constantly searching for creative designs, especially when it comes to furniture and internal design. Meanwhile, innovative materials and ideas are actively sought after by designers for usage in furniture and interior design. In this scope, our study explores the practical implications of using date palm fronds and plastic waste from drinking water bottle to create a composite with varying loadings of date palm frond nanoparticles (DPFNP) at 10, 20, and 30 wt % and its applications on furniture design. A desktop extruder was used to form the composites into filaments, which were subsequently used to create 3D-printed specimens. The impact of adding (DPFNP) on the composite's mechanical, thermal, and chemical properties was assessed. Polyethylene terephthalate (PET) drinking water bottle waste, and filament composites presented similar FTIR spectra; however, filament composites presented increased thermal stability and mechanical strength. The filament with 10 wt% DPFNP has been effectively printed with a 3D printer, demonstrating the practicality of employing the developed filaments and perhaps encouraging new uses in furniture and interior design. As a result, employing DPFNP in the recycled PET (RPET) matrix offers a cheap substitute for making filaments. It could increase the use of 3D printing in furniture and interior design by using more environmentally friendly materials. This result will be considered the first phase of future research investigation on a full-scale furniture prototype, examining its physical, thermal, and mechanical properties.

Development of bone surrogates by material extrusion-based additive manufacturing to mimic flexural mechanical behaviour and fracture prediction via phase-field approach

Background and objectiveThe limited availability of human bone samples for investigation leads to the demand for alternatives. Bone surrogates are crucial in promoting research on the intricate mechanics of osseous tissue. However, solutions are restricted to commercial brands, which frequently fail to faithfully replicate the mechanical response of bone, or oversimplified customised simulants designed for a specific application. The manufacturing and assessment of reliable bone surrogates made of polylactic acid via material extrusion-based additive manufacturing are presented in this work. MethodsAn experimental and numerical study with 3D-printed dog-bone and prismatic specimens was carried out to characterise the polymeric feedstock and analyse the influence of process parameters under three-point bending and quasi-static conditions. Besides, three porcine rib samples were considered as a reference for the development of the artificial bones. Bone surrogates were manufactured from the 3D-scanned real bone geometries. In order to reproduce the trabecular and cortical bone, a lattice structure for the infill and a compact shell surrounding the core were employed. Infill density and shell thickness were evaluated through different printing configurations. Additionally, a computational analysis based on the phase-field approach was conducted to simulate the experimental tests and predict fracture. The modelling considered homogenisation of the infill material. ResultsOutcomes demonstrated the potential of the presented methodology. Maximum force and flexural stiffness were compared to real bone properties to find the optimal printing configuration, replicating the flexural mechanical behaviour of bone tissue. Certain configurations accurately reproduce the studied properties. Regarding the numerical model, strength and stiffness prediction was validated with experimental results. ConclusionsThe presented methodology enables the manufacturing of artificial bones with accurate geometries and tailored mechanical properties. Furthermore, the described modelling strategy offers a powerful tool for designing bone surrogates.

Optimization Course of Titanium Nitride Nanofiller Loading in High-Density Polyethylene: Interpretation of Reinforcement Effects and Performance in Material Extrusion 3D Printing.

In this study, titanium nitride (TiN) was selected as an additive to a high-density polyethylene (HDPE) matrix material, and four different nanocomposites were created with TiN loadings of 2.0-8.0 wt. % and a 2 wt. % increase step between them. The mixtures were made, followed by the fabrication of the respective filaments (through a thermomechanical extrusion process) and 3D-printed specimens (using the material extrusion (MEX) technique). The manufactured specimens were subjected to mechanical, thermal, rheological, structural, and morphological testing. Their results were compared with those obtained after conducting the same assessments on unfilled HDPE samples, which were used as the control samples. The mechanical response of the samples improved when correlated with that of the unfilled HDPE. The tensile strength improved by 24.3%, and the flexural strength improved by 26.5% (composite with 6.0 wt. % TiN content). The dimensional deviation and porosity of the samples were assessed with micro-computed tomography and indicated great results for porosity improvement, achieved with 6.0 wt. % TiN content in the composite. TiN has proven to be an effective filler for HDPE polymers, enabling the manufacture of parts with improved mechanical properties and quality.