Search Results (959)

FDM-printed polylactic acid (PLA) composites containing 5 and 10 wt% obsidian powder sourced from the Kars region of Eastern Anatolia (Turkey) were produced via twin-screw masterbatch extrusion and subsequent single-screw filament dilution. Mechanical (tensile, three-point flexure, notched Charpy impact, Shore D), physical (density), thermal (simultaneous TGA/DSC) and microstructural (macroscopic fractography and SEM at 100×–1000×) characterizations were performed on FDM-printed specimens. Young’s modulus rose monotonically by +9.0% at 5 wt% and +18.2% at 10 wt%, while ultimate tensile strength decreased by 12.4% and 17.3%, respectively. The flexural modulus increased by +15.2% at 5 wt% and plateaued at 10 wt% (+16.7%), whereas the flexural strength decreased by only 3.5% at 10 wt%, indicating that flexure-mode loading is markedly more tolerant of obsidian filler than axial tension. Shore D hardness rose by +2.11 points from 0 to 5 wt% with saturation thereafter. TGA showed a dual thermal effect: T₅ and T₁₀ dropped by 5–6 °C from 5 to 10 wt%, while the main decomposition rate decreased by ~46% and the decomposition interval widened from 9.7 to 23.5 °C, indicating a barrier/heat-shielding effect of dispersed silicate particles. SEM revealed a continuous ductile → transitional → brittle progression with increasing obsidian content; extended interfacial debonding lines at 10 wt% identified weak unmodified filler/matrix coupling as the principal performance-ceiling factor. Density measurements indicated a ~3–6% residual void fraction consistent with the inter-bead voids observed by SEM. To the authors’ knowledge, this is the first systematic study of obsidian as a reinforcing filler in PLA; the 5 wt% composition is identified as a strong candidate for esthetic, flexure-dominant, and low-load structural applications. Full article

Resveratrol (RSV) is a poorly water-soluble polyphenolic compound with various potential health benefits, but its pharmaceutical application is limited by low aqueous solubility and poor oral bioavailability. Additive manufacturing (AM), particularly fused deposition modeling (FDM) 3D printing, offers a flexible approach for fabricating oral dosage forms with customized geometry and internal architecture. In this study, hot-melt extrusion (HME) combined with fused deposition modeling (FDM) 3D printing was used to prepare RSV-loaded tablets with different infill patterns. Hydroxypropyl methylcellulose acetate succinate and hydroxypropyl cellulose were selected as polymeric carriers to prepare RSV-loaded filaments suitable for FDM printing. The effects of infill pattern on the solid-state characteristics, dimensional accuracy, mechanical properties, floating behavior, and in vitro drug release of the printed tablets were systematically investigated. Differential scanning calorimetry, powder X-ray diffraction, and polarized light microscopy indicated that RSV was mainly converted into an amorphous or molecularly dispersed state after HME and FDM processing. All designed tablets were successfully printed and showed acceptable shape fidelity, while different infill patterns resulted in variations in tablet weight, mechanical strength, floating duration, and release behavior. In vitro dissolution studies showed that the RSV release profiles were dependent on the internal infill architecture. Tablets with more complex infill patterns generally exhibited slower drug release, which may be related to differences in internal pore structure, medium penetration pathways, matrix hydration, and diffusion distance. Release kinetic analysis further suggested that RSV release from the printed tablets involved a combination of diffusion and polymer relaxation processes. These results demonstrate that infill pattern is an important structural parameter for modulating the mechanical performance and drug release behavior of FDM 3D-printed RSV tablets. This study provides useful guidance for the design of 3D-printed oral dosage forms with tunable release characteristics. Full article

The rapid growth in the use of carbon fiber-reinforced polymers (CFRPs) and fused-deposition-modeled (FDM) polylactic acid (PLA) has generated substantial non-biodegradable and thermoplastic waste streams, creating urgent needs for scalable recycling and valorization strategies. This study develops and evaluates an integrated route that chemically recovers carbon fibers (CFs) from CFRP waste and converts them into high-performance reinforcements for recycled PLA matrices. CFRP fragments were pre-swollen in acetic acid (120 °C, 1 h), then depolymerized by means of oxidation with 1 M KMnO₄ (100 °C, 2 h), washed, dried (100 °C, 24 h), and size-reduced by means of cryogenic milling. Recycled CFs (treated) and untreated CFRP fragments were blended with 3D-printing PLA waste at 10, 20 and 30 wt.% via melt mixing (175 °C, 5 min, 70 rpm) and molded into ASTM D638 dog-bone specimens. Materials were characterized via XRD, FTIR, Raman, SEM and mechanical testing. XRD and Raman confirmed retention of the graphitic backbone after treatment; FTIR and Raman revealed oxygen-containing surface functionalization consistent with oxidation, while SEM showed effective removal of epoxy and improved fiber surface cleanliness. Compared with neat PLA (tensile strength 45.4 MPa; modulus 2.6 GPa; elongation 6.3%), composites reinforced with chemically recycled CFs exhibited marked mechanical enhancement: at 30 wt.% treated CF, the tensile strength increased to 102.6 MPa (+126%), elastic modulus to 11.7 GPa (+350%), and toughness to 250.3 MPa, while ductility decreased to 2.9%. Equivalent composites with untreated CFRP exhibited smaller gains (30 wt.%: tensile 87.3 MPa; modulus 10.3 GPa), highlighting the benefit of epoxy removal and surface activation for fiber–matrix adhesion. The proposed chemical recycling pathway is operationally simple and cost-effective, produces reusable CFs with preserved graphitic structure and enhanced surface chemistry, and enables the fabrication of high-performance, waste-derived PLA composites suitable for structural and engineering applications. This work demonstrates a viable waste-to-value approach that advances circularity for both CFRP and 3D-printing polymer waste streams. Full article

The increasing demand for high-performance and multifunctional polymer materials has driven interest in improving the mechanical properties of polymer components produced through additive manufacturing. This study aims to systematically investigate and comparatively evaluate the effects of low-content nanofiller incorporation on the structural, thermal, and mechanical performance of PLA-based materials produced via fused deposition modeling (FDM), with a focus on identifying filler-dependent behavior under different loading conditions. In this study, polylactic acid (PLA) composites reinforced with 0.5 wt.% graphene (Gr) and 0.5 wt.% silver (Ag) nanoparticles, added separately, were produced using fused deposition modeling (FDM) and comparatively investigated. Each nanofiller was incorporated individually into PLA-based filaments, and standard test specimens were fabricated via 3D printing. Structural, thermal, and mechanical properties were evaluated using tensile, compressive, and three-point bending tests, along with SEM, EDS, XRD, FTIR, DSC, and TGA analyses. The results showed that pure PLA exhibited typical brittle behavior and a single-stage thermal degradation profile. The tensile strength of pure PLA was 41.93 MPa, and the flexural strength was 70.76 MPa. The addition of 0.5 wt.% graphene led to noticeable improvements, particularly in flexural properties, while only a minimal (almost negligible) increase was observed in tensile strength, with tensile strength increasing to 42.24 MPa (+0.74%) and flexural strength increasing to 110.78 MPa (+56.6%). In contrast, 0.5 wt.% Ag exhibited mixed and load-dependent mechanical behavior, with slight improvements in flexural strength but reductions in tensile and compressive properties, where tensile strength decreased to 22.13 MPa (−47.2%) while flexural strength increased to 112.06 MPa (+58.3%). Structural and thermal analyses indicated that both nanofillers did not significantly alter the PLA matrix chemically, while contributing to controlled changes in material properties primarily through physical interactions. The novelty of this work lies in the comparative evaluation of graphene and silver nanoparticle reinforcement at a fixed low loading level within FDM-processed PLA, combined with a comprehensive and correlated analysis of mechanical, structural, and thermal behavior on the same specimen sets, enabling a clearer understanding of filler-dependent performance mechanisms in additively manufactured nanocomposites. Overall, it was concluded that low-rate nanofiller additions, when properly dispersed, may lead to selective improvements in the performance of PLA-based composites depending on filler type and loading mode, and show potential for advanced engineering applications such as lightweight structural components, functional sensors, and additive-manufactured parts requiring tailored mechanical performance and multifunctionality. Full article

The application of continuous carbon fiber (CCF) can reinforce the mechanical properties of 3D-printed parts, but the effect of reinforcement layer distribution on composite performance remains unclear. This study investigates the effect of concentrated and separated distributions of CCF layers with different numbers of reinforcement layers. Tensile and flexural tests are conducted in accordance with ASTM D5083 and ASTM D790, respectively. Under the conditions of a solid-filled matrix (Onyx) and 0° CCF deposition, both concentrated and separated CCF layers improve several mechanical properties. Compared with pure Onyx, one-layer CCF increases the tensile modulus by about six times and more than doubles the tensile strength. Increasing the CCF volume leads to further increases in these properties. With concentrated three-layer CCF, the tensile modulus and tensile strength reach 7.153 ± 0.090 GPa and 109.045 ± 5.124 MPa, respectively. For flexural properties, separated two- and three-layer CCFs significantly improve the tangent modulus of elasticity from 0.467 ± 0.106 GPa for pure Onyx to 2.246 ± 0.333 GPa and 3.394 ± 0.081 GPa, respectively. This study also compares the tensile and flexural strength-to-weight ratio of all specimen groups and analyzes the failure mechanisms based on macroscopic fracture appearance. The results can provide guidance for selecting appropriate CCF layer distribution strategies to reinforce composites in different applications. Full article

This paper investigates the viability of utilizing Fused Deposition Modeling (FDM) for the fabrication and follow-up testing of a hemispherical resonator (HR). This form of resonator has several significant applications, including the design of vibratory gyroscopes. While traditional high-precision resonators for this application rely on expensive fused-silica fabrication, this study proposes a macro-scale approach using Polylactic Acid (PLA) to enable accessible lab-scale experimentation. The specimens, featuring a unique central-hole mounting configuration, were designed in SolidWorks and analyzed via finite element methods to establish the modal hierarchy. Experimental Modal Analysis (EMA) was conducted using a Laser Doppler Vibrometer (LDV) to acquire vibration signals, which were then analyzed in NVGate, MATLAB, and MEscope to extract natural frequencies and quality factor. Results for a lab-scale HR specimen identified the n = 2 wine-glass mode with a deviation from theoretical natural frequency predictions largely attributed to inherent defects in the fabrication process. Furthermore, a frequency split of 2.15 Hz was observed due to the inherent asymmetries and mass imbalances of the fabrication method. The quality factor was evaluated via the ring-down method and validated using the half-power bandwidth (HPBW) technique. This work demonstrates that 3D-printed resonators serve as an effective, low-cost platform for isolating modal behaviors and optimizing geometric parameters before advancing to micro-scale fabrication. Full article

Additively manufactured cellular architectures frequently exhibit brittle failure under impact due to layer-induced stress concentrations. Through the programming of architectural and material design, specifically combining Fused Deposition Modeling (FDM) lattice topology with hyperelastic polyurea infiltration, this study achieves active control over the macroscopic transition from catastrophic structural fragmentation to stable progressive collapse. To evaluate this, auxetic and honeycomb specimens printed with ABS and glass-fiber-reinforced polyamide (PA-GF) were evaluated in unreinforced and polyurea-infiltrated states under quasi-static compression, three-point bending, and Charpy impact loading. Results show that the compressive response depends primarily on cellular topology; the pure auxetic (A-A) configuration provided the highest stiffness and energy absorption. Polyurea infiltration did not significantly alter elastic stiffness but increased post-yield stability, leading to a 96.6% elastic recovery in PA-GF A-A structures. In flexure, the base polymer governed stiffness, with ABS structures measuring 68% stiffer than PA-GF. Unreinforced ABS achieved 34% higher specific energy absorption (SEA) than PA-GF under compression, with the A-H topology maximizing SEA. Under dynamic impact, PA-GF absorbed an average of 70% more energy than ABS, and the H-A configuration recorded the highest impact resistance. The addition of polyurea shifted the failure mode from brittle fragmentation to stable elastomeric deformation, increasing absorbed impact energy by 52% for ABS and over 30% for PA-GF, preventing catastrophic structural failure. Integrating topological sequencing with elastomeric confinement provides a direct method to control energy dissipation and damage tolerance in 3D-printed cellular composites. Full article

Conventional formwork systems are limited in their ability to efficiently realize complex and free-form concrete geometries, while additive manufacturing (AM)-based formwork faces constraints in casting-stage structural stability and cost-effectiveness, particularly at construction scale. To address these limitations, a hybrid formwork system integrating a structural steel frame with 3D-printed modules is proposed, in which the steel frame resists casting-induced lateral pressure while the printed components define complex mold geometries. The system was fabricated and validated through a full-scale case study structure measuring 3.0 m × 1.7 m × 2.2 m, produced using a large-scale fused deposition modeling (FDM) process with carbon-fiber-reinforced ABS (ABS-CF20). Geometric accuracy was evaluated by comparing design dimensions with as-built measurements across planar, edge, curved, and inclined regions. Construction efficiency and cost performance were assessed through process-based and cost-based comparisons with conventional steel formwork and fully 3D-printed formwork alternatives. The constructed structure reproduced the intended geometry with an average deviation of approximately 3.2 mm and a maximum deviation within ±4 mm, and no notable formwork deformation or damage was observed during concrete casting. Relative to conventional steel formwork, the hybrid system reduced total fabrication duration by about 50% and fabrication cost by about 60% based on a normalized cost index, while also outperforming fully 3D-printed formwork in cost efficiency by about 45%. The modular configuration and bolted connection system further improved transportability, on-site assembly efficiency, and component reusability. These findings demonstrate that the proposed hybrid formwork system provides a practical and resource-efficient pathway for fabricating complex concrete structures, supporting the broader adoption of digital fabrication in sustainable construction practice. Full article

There is a lack of knowledge concerning the interlaminar fracture toughness of 3D-printed composite materials using both commercial filament composites and fused deposition modeling (FDM) technology from Markforged^®. In this investigation, additive manufacturing (AM) continuous fiber-reinforced thermoplastic (cFRT) specimens have been tested to characterize the initiation and propagation of interlaminar fracture toughness in mode I (G_I). Unidirectional glass fiber (GF)-reinforced polyamide 6 (PA) laminates were characterized by means of the double cantilever beam (DCB) test. These specimens were manufactured using a MarkTwo^® printer and tested without doublers, following a laminate configuration selected according to appropriate experimental findings reported in the state of the art, ensuring reliable fracture characterization. The experimental results exhibited repeatability and strong agreement between the modified compliance calibration (MCC) and modified beam theory (MBT) reduction methods. The resistance curve (R-curve) indicated a progressive increase in fracture resistance during crack propagation. To analyze the experienced failure mechanism during testing, the fracture surfaces of representative post-mortem DCB specimens were observed using a scanning electron microscope (SEM), revealing characteristic morphological features at two magnification levels. Moreover, representative cross-sections of the tested DCB specimens were electronically observed to analyze the interlaminar morphologies, showing an irregular and random distribution of the matrix, fiber, and voids between consecutive plies and adjacent deposited rasters. Compared with previously reported Markforged^® continuous fiber-reinforced systems, the GF/PA composite material exhibited intermediate initiation fracture toughness but lower propagation toughness. This study contributes to filling the existing gap in fracture toughness data for glass fiber-reinforced additively manufactured composites. Full article

This paper presents a practical implementation of a 3D-printed spherical Luneburg lens for gain enhancement of a WR-28 open-ended waveguide antenna operating in the Ka-band. The lens is designed based on Luneburg theory and realized using a six-zone discretized gradient-index structure, providing a balance between theoretical performance and fabrication feasibility. The proposed design enables the realization of the required permittivity distribution using a single dielectric material, where the effective permittivity of each zone is controlled through infill variation in a fused deposition modeling (FDM) process. To facilitate fabrication, the lens is divided into two hemispherical parts, enabling reliable manufacturing and assembly while maintaining the intended dielectric profile. The antenna performance is experimentally evaluated through reflection coefficient (S₁₁) measurements and radiation pattern characterization in both the XZ and YZ planes over the frequency range of 26.5–40 GHz, including co-polarized and cross-polarized responses. The proposed antenna achieves a simulated realized gain ranging from 17.6 dBi to 19.83 dBi, while the measured realized gain ranges from 16.42 dBi to 18.43 dBi, with a maximum deviation of 1.47 dB. In comparison, the standalone WR-28 open-ended waveguide exhibits a measured realized gain of 7.22–8.01 dBi. The integration of the six-zone Luneburg lens results in a realized gain enhancement of 9.20–10.97 dB across the operating band. These results confirm that the proposed approach provides a simple, low-cost, and experimentally validated solution for high-gain millimeter-wave antenna applications, while maintaining good agreement between simulation and measurement. Full article

The utilization of polyethylene terephthalate (PET) waste from single-use packaging offers potential for sustainable manufacturing. This study evaluates recycled PET (rPET) from bottles as an FDM filament by varying infill architectures (honeycomb, gyroid, grid, and triangles) and layer thicknesses (0.20, 0.25, and 0.30 mm), with commercial PETG as a benchmark. Compared with previous rPET FDM studies, which were limited to reporting mechanical strength, the novelty of this study lies in the fact that it not only reports mechanical strength performance, but also compares printing time requirements and material efficiency. Efficiency calculations are obtained by comparing the weight of the filament to the weight of the printed specimen, which then correlates with optimizing processing time and costs. Overall, rPET produced densities of 1.11–1.22 g/cm³, tensile strengths of 12.5–22.5 MPa, flexural strengths of 12.5–30 MPa, impact strengths of 0.032–0.060 J/mm², and surface roughnesses of Ra 5.2–7.1 μm, while PETG showed higher mechanical performance (tensile 30–39.5 MPa, flexural 30–50 MPa, impact 0.037–0.065 J/mm²) and comparable density (1.15–1.27 g/cm³). Within rPET, gyroid provided the best optimal performance; the gyroid (0.20 mm) variation achieved the highest impact response (0.060 J/mm²) and the lowest Ra (5.2 μm) and the gyroid (0.25 mm) variation maximized flexural strength (30 MPa) and the gyroid (0.30 mm) variation maximized tensile strength (22.5 MPa). Material utilization efficiency was consistently higher for rPET (65–68%) than for PETG (46–56%). These results provide an integrated rPET-specific assessment and practical parameter recommendations for functional 3D printing, while also aligning with SDG 12 by pro-moting resource-efficient circular-economy practices through the utilization of waste materials in additive manufacturing. Full article

Flexible thermoplastic polyurethane (TPU) materials fabricated using fused deposition modeling (FDM) are increasingly used in engineering and biomedical applications where exposure to moisture is unavoidable. However, the relationship between material hardness, water absorption, diffusion behaviour, and dimensional stability remains insufficiently understood and investigated. In this study, the hygroscopic behaviour of eight commercially available TPU filaments (60A–98A Shore hardness) was systematically investigated. Specimens were produced using an FDM 3D printer under controlled processing conditions and immersed in physiological solution (0.9% NaCl) for up to 96 h. Water absorption, dimensional changes, and diffusion characteristics were analyzed. Diffusion coefficients were determined using the Fickian diffusion model based on the initial stage of water uptake. The results suggest a transition in behaviour between lower- and higher-hardness materials. Softer TPU materials (60A–85A) exhibited higher water absorption (up to ~1.80%) and an apparent linear trend between hardness and absorption within the investigated material group (R² = 0.999). In contrast, higher-hardness materials (89A–98A) showed lower absorption (~1.18–1.42%) and a weaker apparent relationship with hardness (R² = 0.4214). Diffusion coefficients ranged from 1.40 × 10⁻¹³ to 3.40 × 10⁻¹² m² s⁻¹, with no monotonic dependence on hardness. Additionally, no clear correlation between diffusion kinetics and equilibrium absorption or volumetric expansion was observed. These findings indicate that hygroscopic behaviour of FDM-printed TPU materials cannot be reliably predicted based solely on hardness, and that diffusion, absorption, and swelling may be influenced by different mechanisms. The identified transition from hardness-dependent to behaviour potentially influenced by material structure provides new insight for the design and selection of flexible polymer components in moisture-exposed environments, particularly in biomedical applications. Full article

Polymer-based composites with magnetic properties are promising materials that are able to combine the usual polymer features (low density, high electrical resistance, enhanced flexibility, and processability, etc.) with magnetic properties typically associated with ferro- or ferrimagnetic metals, alloys or metal oxide. The combination of recycled NdFeB powders with additive manufacturing techniques based on material extrusion enables the production of magnetic composites. The novelty of this approach lies in the use of 3D printing supported by an external magnetic field, which is used to align the particles during the printing process and thus improve the final magnetic properties. This approach represents a sustainable strategy for the recovery of electronic waste, converting it into high-value-added magnetic materials intended for additive manufacturing applications. Micrometric particles made of a Neodymium–Iron–Boron (NdFeB) alloy are compounded with a flexible thermoplastic matrix made of polybutylene adipate-co-terephthalate (PBAT). The NdFeB alloy is recovered from permanent magnets of obsolete hard drives and is demagnetized, ground to powder under an inert atmosphere, and finally sieved to a particle size below 50 µm. The obtained powder is mixed with the polymer using a twin-screw extruder. The composite material containing the NdFeB particles is then processed to obtain a calibrated filament, used for the fused deposition modeling (FDM) three-dimensional (3D) printing of magnetic composites. To improve the composite’s ferromagnetic behavior, the particles were aligned along the stacking direction of the layers during the 3D FDM process by printing directly onto a permanent magnet placed on the build plate. Composites containing up to 50% by weight of recycled NdFeB powder were successfully processed using FDM technology, exhibiting increased stiffness, with the storage modulus rising from 123 to 178 MPa at 20 °C, while magnetic field-assisted printing increased the remanence from 11 to 28 emu/g and improved the reduced remanence from 0.21 to 0.49, corresponding to an estimated fourfold improvement in the magnetic energy product. Full article

Fused deposition modelling (FDM) is being increasingly considered for manufacturing electrically insulating components with complex geometries; however, the relationship between mechanical performance and dielectric breakdown behaviour of common printable polymers remains insufficiently understood. This study investigates the electrical insulation potential of five FDM-printed thermoplastic polymers—ABS, PLA, PETG, ASA, and PC/ABS—by evaluating their dielectric breakdown strength and mechanical properties. Specimens were fabricated using fused deposition modelling and tested according to standardised procedures: dielectric breakdown strength was measured in accordance with IEC 60243, and tensile properties were determined following ASTM D638. Surface damage produced during breakdown events, including holes and carbonised regions, was quantified using ImageJ analysis. The results were evaluated comparatively to identify the advantages and limitations of each material for electrical insulation applications. Among the tested materials, PLA exhibited the highest mechanical strength and the lowest surface damage area, whereas ABS demonstrated the highest dielectric breakdown strength. These findings highlight the trade-offs between mechanical and dielectric performance in material selection for 3D-printed insulators, and they demonstrate that ImageJ-based damage analysis serves as a valuable supplementary tool for characterising breakdown behaviour. Full article

This study presents an experimental investigation of 3D-printed poly(lactic acid) samples (PLA) subjected to high-voltage AC stress. Although additive manufacturing is gaining importance in electrical engineering, studies on FDM-printed materials have concentrated mainly on mechanical behaviour. Their dielectric strength under oil-immersed high-voltage stress—a critical aspect for insulation applications—has not been systematically investigated. Additive manufacturing is increasingly considered for auxiliary insulating components in oil-immersed high-voltage equipment; however, process-induced voids and interlayer interfaces can intensify the local electric field and reduce dielectric strength. This work evaluates the AC breakdown strength of 3D-printed PLA specimens under oil immersion using the standard AC electrical strength test method for solid insulating materials. Two parameter sets were investigated: extrusion temperature (190–240 °C ) at a constant nozzle diameter, and nozzle diameter ($0.3$–$0.6 \mathrm{mm}$) at a constant extrusion temperature of $T_{\mathrm{e}}=200°\mathrm{C}$. Breakdown data were analysed using the standard two-parameter Weibull approach typically used in the statistical evaluation of electrical insulation breakdown strength, with the results additionally expressed in terms of the $B_{10}$, $B_{50}$, and $B_{90}$ percentiles. The experimental observations were interpreted using simplified electric-field simulations representing inter-bead and interlayer voids. The results indicate that, for a given material, there exists an optimal extrusion temperature that yields the highest electrical breakdown performance. Full article