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Highlights: The stable periodic porous shielding materials were prepared by combining the strategies of 3D printing and metamaterial design. The relationship between porous material structure and electromagnetic interference shielding efficiency (EMI SE) effectiveness was deeply explored, revealing the important structural parameters for realizing tunable EMI SE property. The optimized design of the periodic porous shielding box achieves effective EMI shielding in a wide wavelength range (over 2.4 GHz). The new-generation electronic components require a balance between electromagnetic interference shielding efficiency and open structure factors such as ventilation and heat dissipation. In addition, realizing the tunable shielding of porous shields over a wide range of wavelengths is even more challenging. In this study, the well-prepared thermoplastic polyurethane/carbon nanotubes composites were used to fabricate the novel periodic porous flexible metamaterials using fused deposition modeling 3D printing. Particularly, the investigation focuses on optimization of pore geometry, size, dislocation configuration and material thickness, thus establishing a clear correlation between structural parameters and shielding property. Both experimental and simulation results have validated the superior shielding performance of hexagon derived honeycomb structure over other designs, and proposed the failure shielding size (Df ≈λ/8 − λ/5) and critical inclined angle (θf ≈43° − 48°), which could be used as new benchmarks for tunable electromagnetic shielding. In addition, the proper regulation of the material thickness could remarkably enhance the maximum shielding capability (85 − 95 dB) and absorption coefficient A (over 0.83). The final innovative design of the porous shielding box also exhibits good shielding effectiveness across a broad frequency range (over 2.4 GHz), opening up novel pathways for individualized and diversified shielding solutions. [ABSTRACT FROM AUTHOR]

3D printing technology is the new frontier in building construction. It is especially useful for making small structures within a short period. Full construction, including interior partitions and exterior façades, can be achieved with this technology. This paper proposes a parametric Voronoi tessellations model for quickly generating and fabricating 3D-printed hexagonal honeycomb partitions for interior design. Comprehensive experimental testing was conducted to characterize the mechanical properties and investigate the energy absorption characteristics of the proposed 3D-printed hexagonal honeycomb while comparing it to alternative hexagonal honeycomb structures. The tests included tensile testing (ASTM-D638) of the printed Polylactic Acid (PLA) material, especially with the almost total absence of conducted research that reported mechanical properties for 3D printed material with low infill percentages such as 10%. In addition, an in-plane quasi-static axial compression testing of the lightweight honeycomb structures was also conducted on the printed structure with the same low infill percentage. Compared to non-Voronoi honeycomb structures, the Voronoi honeycomb resulted in superior mechanical and energy absorption properties with energy absorption values ranging from 350 to 435 J and crash force efficiency being 1.42 to 1.65. [ABSTRACT FROM AUTHOR]

Polyolefins and polyolefin elastomers (POEs) are widely used in various applications due to their unique properties. However, their use in 3D printing has been limited due to challenges such as excessive softness, shrinkage, warpage, and poor mechanical properties. In this study, two strategies were employed to enhance the performance of POEs in 3D printing. First, POE was blended with 10%, 30%, and 50% percentages of linear low‐density polyethylene (LLDPE) to improve the material's mechanical properties and printability. Second, a specialized printer called a pneumatic feeding fused granule fabrication (FGF) printer was used. This printer allows for the direct printing of material granules, eliminating the need for filaments and resolving filament‐related problems. To evaluate the quality of the printed parts, tensile tests, dynamic mechanical thermal analysis (DMTA), and scanning electron microscopy (SEM) imaging were conducted. The printed parts showed desirable tensile properties (with approximately 3000% elongation at break and approximately 12 MPa tensile strength). Compression tests were also conducted on cubic structures with varied composition ratios and printing patterns such as grid, triangle, and honeycomb. The main purpose of this research was to explore the energy absorption capabilities of the printed blends. The results of our study showed that blending POE with LLDPE improved printability, tensile strength, energy absorption, and compressive properties. The blend with 50% LLDPE and honeycomb structure exhibited the best compressive and energy absorption properties. Highlights: Blending of POE and LLDPE using melt mixing with three different blending ratios.Successful 3D printing with the fused granule fabrication technique.Investigating mechanical properties, microstructure, and thermal analysis.125% increase in ultimate tensile strength by increasing LLDPE.Achieving the highest energy absorption for the 3D printed honeycomb structure. [ABSTRACT FROM AUTHOR]

Silicon oxycarbide (SiOC) ceramics have been used to fabricate microwave-absorbing metastructures, demonstrating impressive absorption capabilities. However, SiOC ceramic metastructures with excellent performance require simple fabrication processes and appropriate mechanical and electromagnetic properties. In this study, a solvent-free photosensitive polysiloxane preceramic was developed by blending methoxy/hydroxy polysiloxanes with acrylates, with a ceramic yield of over 60% after curing using a novel two-step ultraviolet (UV)/thermal method. The composition and microstructure of SiOC ceramics can be designed by controlling the preceramic composition. Dense, crack-free gyroid-shellular shaped triple periodic minimal surface (GS-TPMS) electromagnetic metastructures were fabricated using digital light processing (DLP) 3D printing technology. By designing the porosity of the GS-TPMS structure to 51%, an effective absorption bandwidth that covers the X-band can be achieved at a thickness of 3.1 mm. The honeycomb structure, with a geometric density of 0.69 g/cm3, exhibited a high compressive strength of 107.05 MPa. This paper presents an efficient approach for the prompt and customized fabrication of lightweight ceramic metastructures with outstanding microwave absorption properties. • A solvent-free polysiloxane/acrylate hybrid preceramics is developed for 3D printing. • The UV/thermal two-stage treatment achieved cross-linking curing of the preceramics. • Multiscale design of SiOC ceramics for enhanced microwave absorption properties. • SiOC ceramic metastructures with effective absorption in the X-band are prepared. [ABSTRACT FROM AUTHOR]

In recent days, the sandwich structure has created significant evolutionary changes in world technology, which are used in many sectors like automobile, aeronautical, defence, etc., The structural-based studies are evaluated and replaced with the sandwich structure, which contains three layers; a core layer, upper and lower face sheets. This article evaluates the transverse shear modulus of the sandwich core structure of 3D-printed materials. Henceforth the bioinspired structural design is adopted as core structure which is bio-mimicked from the microstructural layer design of the woodpecker's beak. Forming the wavy patterns is incorporated with the conventional honeycomb shape. The edges of the structure's waviness are modeled as champer edges with the required dimensions. The fused deposition modeling (FDM) process is carried out to bring out the expected sandwich core design. Here, the article speaks about the contest between the various types of materials like polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), high impact polystyrene (HIPS), carbon fiber-polylactic acid (CF-PLA), carbon fiber - acrylonitrile butadiene styrene (CF-ABS), carbon fiber-polyethylene terephthalate glycol (CF-PETG). Each material contains specific properties; Henceforth, each material property is validated by ASTM E1876 standard. The objective is to find the good effectiveness of transverse shear modulus by the Nondestructive process called alternative dynamic method among the 3D-printed Bioinspired materials. In this study, CF-PLA stands ahead to give efficient transverse shear modulus property values. These results can be carried forward to structural development, enhancing the structure's performance as the futuristic pathway. [ABSTRACT FROM AUTHOR]

The novelty of this research lies in the successful fabrication of a 3D-printed honeycomb structure filled with nanofillers for acoustic properties, utilizing an impedance tube setup in accordance with ASTM standard E 1050-12. The Creality Ender-3, a 3D printer, was used for printing the honeycomb structures, and polylactic acid (PLA) material was employed for their construction. The organic, inorganic, and polymeric compounds within the composites were identified using fourier transformation infrared (FTIR) spectroscopy. The structure and homogeneity of the samples were examined using a field emission scanning electron microscope (FESEM). To determine the sound absorption coefficient of the 3D printed honeycomb structure, numerous samples were systematically developed using central composite design (CCD) and analysed using response surface methodology (RSM). The RSM mathematical model was established to predict the optimum values of each factor and noise reduction coefficient (NRC). The optimum values for an NRC of 0.377 were found to be 1.116 wt% carbon black, 1.025 wt% aluminium powder, and 3.151 mm distance between parallel edges. Overall, the results demonstrate that a 3Dprinted honeycomb structure filled with nanofillers is an excellent material that can be utilized in various fields, including defence and aviation, where lightweight and acoustic properties are of great importance. [ABSTRACT FROM AUTHOR]

The present research efforts are directed toward investigating dimensional stability, focusing on bio‐inspired periodic honeycomb lattice structures within carbon fiber reinforced glycol‐modified poly ethylene terephthalate (PETG) composites. These samples are fabricated using extrusion‐based 3D printing, with topological parameters such as shell thickness (ST), unit cell type (UCT), wall thickness (WT), unit cell orientation (UCO), skewing angle (SA), and unit cell size (UCS) being manipulated across three different levels. The experimental findings indicate that achieving the lowest dimensional length error is attainable under specific conditions, including a smaller ST of 0.5 mm, a square UCT, a WT of 0.5 mm, a UCO of 90°, a SA of 0°, and a UCS of 4 mm. Analyzing the results with ANOVA reveals that UCT (28.82%) and WT (18.73%) exert the most significant influence on the dimensional stability response. The regression model closely aligns with experimental outcomes, with an error percentage of 3%, rendering it suitable for large‐scale customization. Under the optimized topological parameters, carbon fiber‐reinforced PETG latticed composites exhibited a dimensional length error of 0.292 mm and a compressive strength of 21.56 MPa. Fractography analysis revealed a brittle mode of fracture across all samples, indicating their stiffness and strength, especially when compared to samples with lower wall thickness. These findings suggest that the designed carbon fiber‐reinforced PETG latticed composite material holds potential for use in minor surgical orthotic and prosthetic applications. Highlights: Bio‐inspired periodic honeycomb lattice structured PETG composites.Topological optimization on the dimensional properties.Taguchi optimization is performed on design‐based lattice structures.Unit cell type has highest contribution of 28.82% on dimensional properties. [ABSTRACT FROM AUTHOR]

A non-pneumatic tire (NPT) overcomes the shortcomings of a traditional pneumatic tire such as wear, punctures and blowouts. In this respect, it shows great potential in improving driving safety, and has received great attention in recent years. In this paper, a carbon fiber-reinforced polyethylene terephthalate (PET/CF) honeycomb is proposed as a support structure for NPTs, which can be easily prepared using 3D printing technology. The experimental results showed that the PET/CF has high strength and modulus and provides excellent mechanical properties. Then, a finite element (FE) model was established to predict the compression performance of auxetic honeycombs. Good agreement was achieved between the experimental data and FE analysis. The influence of the cell parameters on the compressive performance of the support structure were further analyzed. Both the wall thickness and the vertically inclined angle could modulate the mechanical performance of the NPT. Finally, the application of vertical force is used to analyze the static load of the structure. The PET/CF honeycomb as the support structure of the NPT showed outstanding bearing capacity and stiffness in contrast with elastomer counterparts. Consequently, this study broadens the material selection for NPTs and proposes a strategy for manufacturing a prototype, which provides a reference for the design and development of non-pneumatic tires. [ABSTRACT FROM AUTHOR]

In light of the rapid advancements within the electronic industry, the urgent need for the development and implementation of advanced electromagnetic interference (EMI) shielding materials has become paramount. Herein a novel approach is presented for developing of lightweight honeycomb structures using 3D printing technology, combined with subsequent conductive spray coating, containing Silver Nanowires (AgNWs), to achieve effective EMI shielding as well as air vent functionality for thermal cooling.Using polyol method, AgNWs were synthesized having high aspect ratio and crystallinity for to be used as conductive coating on 3D printed structures. The EMI shielding results in X-band demonstrated that the developed structures exhibit promising EMI shielding properties, up to 35 dB attenuation with 2 mm honeycomb cell size, making them suitable for applications requiring EMI protection along with air venting. More importantly in all samples major contribution of the shielding efficiency comes from the absorption of the EM waves (up to 75 %) inside the structures which is helpful to reduce reflected EM noise.Effort was to effectively addresses the inherent limitations of conventional processing technology, by using additive manufacturing and material science to create structures for EMI shielding applications, bridging the gap between existing materials and desired components.

Complex structural configuration design is necessary for dielectric‐magnetic lossy composites to achieved broadband microwave absorption in civil and defense applications. Based on the unique space filling characteristic of fractal structure, the honeycomb metastructure can possess microwave absorption and mechanical resistance. However, traditional molding technique was difficult to realize complex shape of metastructure. Herein, the dielectric‐magnetic filament with different concentration of carbonyl iron particles was fabricated by high‐temperature extrusion process. The multi‐physical honeycomb metastructure with gradient layers was printed by fused deposition modeling (FDM) in a large size. The printed dielectric‐magnetic samples exhibited strong dielectric‐magnetic loss with high printing quality. The honeycomb metastructure achieved broadband microwave absorption in the −10 dB bandwidth of 9.6–18 GHz with tensile strength of 31 MPa. The results indicate that FDM is useful to fabricate metastructure with complex shape for broadband microwave absorption. The dielectric‐magnetic properties of filament are magnified by metastructure design. The proposed design‐fabrication process is promising for functional structure realization with complex shape in the future. Highlights: 1. Magnetic filament was fabricated for functional 3D printing. 2. Structural magnetic dissipation mechanism for microwave was presented. 3. Magnetic metastructure was designed and printed for broadband absorption. 4. Integrated design of mechanical and electromagnetic function was presented. 5. Structural absorption effect of honeycomb metastructure was revealed. [ABSTRACT FROM AUTHOR]

In this study, Al 2 O 3 honeycomb sandwich structures with different core geometries (square, triangular, circular) have been fabricated through an additive manufacturing system based on the stereolithography (SLA) method. The debinding procedure was performed under both nitrogen and air atmospheres. The impacts of the debinding atmosphere and core geometry on the densification and mechanical properties were investigated. The stiffness and flexural strength of the ceramics were examined experimentally using an impulse excitation of vibration technique and a three-point bending test, respectively. The specific stiffness and specific strength of the ceramics were also evaluated, with the core geometries taken into consideration. The outcomes showed that higher densification was achieved when the ceramics were exposed to debinding in nitrogen. The stiffness values were found to be similar for the same debinding condition within the honeycomb sandwich structures, irrespective of the core geometry. Notably, the highest specific stiffness (98 MNm/kg) was achieved for the samples subjected to debinding in nitrogen with a square core geometry. Furthermore, ceramics with square cores for debinding in a nitrogen atmosphere also demonstrated the highest performance in terms of specific strength (110 kNm/kg) within the honeycomb structures. This study demonstrated that Al 2 O 3 honeycomb sandwich structures with square cores may be suitable candidates for lightweight-structure demanding applications. [ABSTRACT FROM AUTHOR]

An infill pattern can be implemented in manufacturing a porous component using 3D Printing technology to reduce the mass of the printed part. The use of an infill pattern and infill angle affects the structure of the printed part. This research aims to investigate the effect of various infill patterns and angles on the compressive strength-to-mass ratio of components manufactured by 3D Printing. This research implements a General Linear Model analysis with two replications. Seventy-two compressive test specimens, according to ASTM D695, are printed and tested for compression. The experiment results show that the type of infill pattern has a significant effect on the mass. However, the mass is not significantly influenced by the infill angle. In addition, the infill pattern type and the infill angle significantly influence the compressive strength of the specimen. Then, the compressive strength-to-mass ratio is significantly affected by the infill patterns and angles. The results indicate that a part using the Honeycomb infill pattern type gains the highest compressive strength-to-mass ratio compared to other infill patterns. On the opposite, the infill pattern that creates the lowest compressive strength-to-mass ratio compared to other infill patterns is the Archimedean chords type. The use of a 45° infill angle causes the lowest compressive strength-to-mass ratio compared to other infill angles. Using a 90° infill angle causes the highest compressive strength-to-mass ratio compared to other infill angles. [ABSTRACT FROM AUTHOR]

Despite the wide growth of additive manufacturing, it is still very expensive to mass produce 3D-printed parts. The costs can be minimized if the quantity of material required to produce a part can be substantially reduced by introducing hollow cavities into the structure, without compromising its properties. This study investigates the effect of the degree of hollowness and different internal cavity structures on the mechanical properties of 3D-printed materials. Test specimens were prepared with four polymeric materials (i.e., acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), carbon fiber-reinforced (CFR) ABS, and CFR PLA) using the fused deposition modeling 3D printing technique. Internal hollow cavities were introduced to the specimens during printing and the specimens were prepared with three different cavity structures (i.e., hexagonal honeycomb, circular drills, and squares), and the degree of hollowness was varied from 0% to 30% in 10% increments. Tensile and flexural properties of the 3D-printed specimens were evaluated and analyzed. The mechanical properties of all specimens were found to decrease with increasing hollowness levels, regardless of the type of material or the internal cavity structure. The hexagonal honeycomb structure showed the best tensile properties out of the three internal cavity structures, while the flexural properties were not significantly affected by the internal cavity structure. The material type had a significant impact on the mechanical properties with PLA exhibiting better tensile and flexural properties than ABS, while their carbon fire reinforced counterparts showed enhanced mechanical properties than pure ABS and PLA. [ABSTRACT FROM AUTHOR]

In most of the automobile and aerospace materials, cellular structures are extensively used due to their lightweight and high energy absorption capabilities. Naturally available animal bones and plant stems are light in weight due to their natural cellular structures. This may inspire various researchers for integrating the various lattice structures such as beam, planar, triply periodic minimal surfaces, and voronoi structures on the various structural materials. The development of lattice structures using 3D printing technology has opened up major attention towards fabricating lightweight components without any complications. In this study, the detailed crashworthiness responses such as compressive strength was optimized in terms of varying the topology‐related factors on the carbon fiber reinforced polyethylene terephthalate glycol (CF/PETG) composite. The experimentation was conducted concerning variable topology factors such as shell thickness, unit cell type, wall thickness (WT), unit cell orientation (UCO), skewing angle, and unit cell size. The model was examined and optimized by means of the Taguchi optimization technique. The crashworthiness response was analyzed using the compression test and moreover, this experimental response is used for the optimization processes. From the observation, the topology factors which contributed more for the higher compressive strength will be UCO of 65.47% and WT of 15.20%. Results of the regression study show that the R square value with concern to the compressive strength will be 92.74%. The optimized design parametric condition for CF/PETG composite established a higher compressive strength of 41.179 MPa, From the overall results, it is clear that the variation in the topology factors has developed a huge and favorable impact on the mechanical characteristics of the lattice‐structured CF/PETG polymer composite. Highlights: Hexagonal Lattice structure incorporation on the carbon fiber reinforced PETG composite.Design optimization on the compressive properties.Taguchi optimization is performed on design‐based lattice structures.Unit cell orientation has higher percentage contribution on compressive strength. [ABSTRACT FROM AUTHOR]

Continuous fiber reinforced polymer composites are widely used in load-bearing components and energy absorbers owing to their high specific strength and high specific modulus. The path planning of continuous fiber is closely related to its structural defects and mechanical properties. In this work, continuous fiber reinforced polymer honeycomb structures (CFRPHSs) with different printing paths were designed and fabricated via the fused deposition modeling (FDM) technique. The investigation of fiber dislocation at path corners was utilized to analyze the structural defects of nodes caused by printing paths. The lower stiffness nodes filled with pure polymer due to fiber dislocation result in uneven stiffness distribution. The bending performance and deformation modes of CFRPHSs with different printing paths and corresponding pure polymer honeycomb structures were investigated by three-point bending tests. The results showed that the enhancement effect of continuous fibers on the bending performance of honeycomb structures was significantly affected by the printing paths. The CFRPHSs with a staggered trapezoidal path exhibited the highest specific load capacity (68.33 ± 2.25 N/g) and flexural stiffness (627.70 ± 38.78 N/mm). In addition, the fiber distributions and structural defects caused by the printing paths determine the stiffness distribution of the loading region, thereby affecting the stress distribution and failure modes of CFRPHSs. [ABSTRACT FROM AUTHOR]

Magnesium (Mg)/Polylactic acid (PLA) composites are promising materials for bone regeneration and tissue engineering applications. PLA is a biodegradable and biocompatible polymer that can be easily processed into various shapes and structures, such as scaffolds, films, and fibers, but has low biodegradability. Mg is a biocompatible metal that has been proven to have good biodegradability and osteoconductivity, which makes it suitable for bone tissue engineering. In this study, we prepared and characterized a Mg/PLA composite as a potential material for direct ink writing (DIW) in 3D printing. The results showed that the addition of Mg has a significant impact on PLA's thermal and structural properties and has also significantly increased the degradation of PLA. XRD was used to determine the degree of crystallinity in the PLA/Mg composite, which provides insight into its thermal stability and degradation behavior. The crystallization temperature of PLA increased from 168 to 172 °C for a 15 wt% Mg incorporation, and the melting temperature reduced from 333 °C to 285 °C. The surface morphology and composition of these films were analyzed with SEM. The films with 5 wt% of Mg particles displayed the best-ordered honeycomb structure in their film form. Such structures are considered to affect the mechanical, biological and heat/mass transfer properties of the Mg/PLA composites and products. Finally, the composite ink was used as a feed for direct ink writing in 3D printing, and the preliminary 3D printing experiments were successful in resulting in dimensionally and structurally integral scaffold samples. The shape fidelity was not very good, and some research is needed to improve the rheological properties of the ink for DIW 3D printing. [ABSTRACT FROM AUTHOR]

By utilizing 3D printing technology, experimental three-point bending (TPB) tests, and finite element analysis, six honeycomb structures with a variety of overall Poisson's ratios (PR) are studied and compared in terms of bending properties and failure mechanisms. Four novel honeycombs that are designed by hybridizing hexagonal and re-entrant units outperform benchmark conventional honeycombs in terms of load-carrying capacity. Architected hybrid geometry honeycombs with zero PR show excellent specific energy absorption capability in comparison to benchmark honeycombs, absorbing approximately 136.9% and 475.1% more energy under TPB. 3D-printed honeycombs consisting of hexagonal units face layer separation damage mode under bending, while honeycombs with re-entrant cells in their lattice fail with joint shear due to the angle of their struts towards loadings. Designing honeycombs with a hybrid geometry lattice can enhance the load-carrying capacity, specific energy absorption, flexibility, and flexural modulus of the structure under bending. Due to their superior performance, the proposed architected hybrid geometry honeycombs with various Poisson's ratios own promising applications in automotive, protective, and construction industries. [ABSTRACT FROM AUTHOR]

Inspired by the double-helix structure of biological DNA, low-volume fraction and high-strength Al 2 O 3 twisted honeycomb structures with characteristics similar to those of helical structures in the z -axis were prepared by digital light processing 3D printing technology. As the twist angle increased, the compressive strength of the fabricated Al 2 O 3 structure decreased, and the deformation mechanism of the Al 2 O 3 structures gradually changed from stretching-dominated to bending-dominated, which can be predicted by the Gibson–Ashby model. The relationship between the effective elastic modulus and the volume fraction that can be modified by varying the wall thickness was described by the Pabst–Gregorova exponential relationship. The compressive strength of the Al 2 O 3 structure with a twist angle of 0° can reach 62.4 MPa at a volume fraction of 13.3%, providing guidance to optimize lightweight structures of ceramics. [ABSTRACT FROM AUTHOR]

Black absorber with wide‐angle high absorption properties is of great significance to the in‐orbit operation of space optical system. However, up to now, black absorber used in space optical system with wide‐angle high absorption properties has rarely been reported. Herein, this work reports a multiscale structure coordinated black poly(ether ether ketone) (PEEK)‐based black absorber with lightweight, low volatilization, and wide‐angle high absorption properties through 3D printing method. The as‐prepared absorber with honeycomb structure shows a high surface absorptivity (about 96.89%), and excellent wide‐angle high absorption properties which absorptivity attenuation rate is only 1.43% at 70°, benefiting from 3D‐printed honeycomb structure and multi‐scale light trap structure on the absorber inner surface. Besides, high and low temperature cycling test shows that its wide‐angle high absorption properties have a good stability at the space extreme environment, and its collected volatile condensable material (CVCM) is as low as 0.00%. This work provides a new strategy for simple fabrication method of novel lightweight multifunctional‐structure integrated absorber for space optical system. [ABSTRACT FROM AUTHOR]

Three-dimensional printing by fused deposition modeling (FDM) coupled with hot-melt extrusion (HME) is a point of convergence of research efforts directed toward the development of personalized dosage forms. In addition to the customization in terms of shapes, sizes, or delivered drug doses, the modulation of drug release profiles is crucial to ensure the superior efficacy and safety of modern 3D-printed medications compared to those of conventional ones. Our work aims to solidify the groundwork for the preparation of 3D-printed tablets that ensure the sustained release of diclofenac sodium. Specifically, we achieved the fast release of a diclofenac sodium dose to allow for the prompt onset of its pharmacological effect, further sustaining by the slow release of another dose to maintain the effect over a prolonged timeframe. In this regard, proper formulation and design strategies (a honeycomb structure for the immediate-release layer and a completely filled structure for the sustained-release layer) were applied. Secondarily, the potential of polyvinyl alcohol to function as a multifaceted polymeric matrix for both the immediate and slow-release layers was explored, with the objective of promoting the real-life applicability of the technique by downsizing the number of materials required to obtain versatile pharmaceutical products. The present study is a step forward in the translation of HME-FDM-3DP into a pharmaceutical manufacturing methodology. [ABSTRACT FROM AUTHOR]

Proton-conducting ceramic membranes designed with an asymmetric configuration have received increasing attention for their 100% H 2 selectivity, high thermo-chemical stability, and intrinsic lower cost respect the Pd–based counterparts. The design of the substrate is of paramount importance to increase the gas diffusivity through the porous support. In this work, porous BaCe 0.65 Zr 0.20 Y 0.15 O 3-δ (BCZY) supports were fabricated for the first time via UV-assisted micro-extrusion. Different BCZY-based inks preparation methods were evaluated to obtain high solid loading (> 40 vol%), solvent and dispersant-free eco-friendly formulations. Printable inks with optimal shear thinning behaviour were successfully extruded, depositing up to three stacked layers without defects. Drying and thermal post printing treatments were carefully optimized to obtain defect-free and easy to handle green bodies. The optimization of the whole process leaded to planar BCZY-based supports with a high degree of engineered porosity and suitable mechanical properties to be potentially applied in asymmetric membrane structures. • Proton conductive BCZY ceramics for hydrogen separation were produced. • Solvent- and dispersant- free UV-curable pastes were obtained. • UV-assisted direct ink writing were considered to obtain complex shapes structures. • Honeycomb type structures with a high degree of engineered porosity were produced. • Samples presents promising mechanical properties. [ABSTRACT FROM AUTHOR]

Free and forced vibration characteristics of composite sandwich beams with single‐core (SC) and dual‐core (DC) are investigated in this study. The wet hand‐layup technique is followed to make the composite face sheet, and honeycomb cores are 3D printed using the fused filament fabrication method. The natural frequencies of SC and DC sandwich beams were measured using experimental modal tests and validated through a three‐dimensional finite‐element model. Also, parametric studies on the geometry of composite structures are performed to scrutinize the effect of DC sandwich beams with different ply orientations, length‐to‐breadth ratios, core thickness, and core cell wall thickness. In addition, the transverse vibration responses of SC and DC sandwich beams are examined under harmonic force excitations at different end conditions. The study result shows that the sandwich beam's vibration behavior is enhanced by the inclusion of a core. [ABSTRACT FROM AUTHOR]

A non-pneumatic tire (NPT) overcomes the shortcomings of a traditional pneumatic tire such as wear, punctures and blowouts. In this respect, it shows great potential in improving driving safety, and has received great attention in recent years. In this paper, a carbon fiber-reinforced polyethylene terephthalate (PET/CF) honeycomb is proposed as a support structure for NPTs, which can be easily prepared using 3D printing technology. The experimental results showed that the PET/CF has high strength and modulus and provides excellent mechanical properties. Then, a finite element (FE) model was established to predict the compression performance of auxetic honeycombs. Good agreement was achieved between the experimental data and FE analysis. The influence of the cell parameters on the compressive performance of the support structure were further analyzed. Both the wall thickness and the vertically inclined angle could modulate the mechanical performance of the NPT. Finally, the application of vertical force is used to analyze the static load of the structure. The PET/CF honeycomb as the support structure of the NPT showed outstanding bearing capacity and stiffness in contrast with elastomer counterparts. Consequently, this study broadens the material selection for NPTs and proposes a strategy for manufacturing a prototype, which provides a reference for the design and development of non-pneumatic tires.

In this paper, a honeycomb Si3N4 ceramic was fabricated by 3D printing with a well‐preserved structure. The effects of Si3N4 content on the rheological properties of Si3N4/sol–silica ink and the printing resolution of products were investigated. The microstructure, phase composition, liner shrinkage rate, and fracture behavior of printed samples before and after sintering were systematically characterized in detail. The results showed that the modified inks had the optimized rheological properties, and the stress–shear rate curves corresponding to each slurry could be well described by Bingham and Herschel–Bulkley fluid models. The corresponding slump rates of the printed samples with different Si3N4 to sol–silica mass ratios were all lower than 4%, and the linear shrinkage rate of all of the samples after sintering was below 20%. The fracture behavior under compressive loading of the honeycomb Si3N4 ceramics tended to be non‐catastrophic fractures both before and after sintering. The compressive strengths of all of the printed samples decreased with the increase of the Si3N4 content, and the highest compressive strength of the honeycomb ceramics could reach 131.2 MPa after sintering at 1600°C, which was about 366.9% higher than that of the samples in green state prior to the sintering. [ABSTRACT FROM AUTHOR]

This research aims at enhancing the performance of scale-model scooter decks by investigating various architected cellular metamaterial and bio-inspired core structure designs, such as honeycomb, tetrachiral, re-entrant, arrowhead, and star-shaped arrangements. An initial effort is made toward the design and rapid prototyping of small-scale deck with a uniform honeycomb core structure. More specifically, polylactic acid is utilized to fabricate complex structures via fused filament fabrication technique. Investigation is then focused on its mechanical performance, such as its bending properties obtained through a three-point bending test. Simulations are also conducted with different core configurations using a geometrically non-linear finite element method which is implemented. Experiments are carried out to verify the numerical results. After validation, various patterns are modeled, and eventually, it is observed that the functionally graded arrowhead structure has the best bending resistance, compared to other bio-inspired and mechanical metamaterial structures. At a constant force of 845 N, the functionally graded arrowhead design lowers the deflection in the middle of the scale model of scooter deck by up to 14.7%, compared to the uniform arrowhead structure. Furthermore, comparing the tetrachiral and functionally graded arrowhead configurations at a constant force, a 30% reduction in central deflection was observed. Due to the lack of similar results and designs in the specialized literature, this work could potentially advance the state-of-the-art scooter core designs and provide designers with architectures that could enhance the performance and safety of scooters. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to find the best geometries among the cylindrical, enamel and honeycomb geometries based upon the mechanical properties (tensile test, compression test and shear test). Further this obtained geometry could be used to fabricate products like exoskeleton and its supporting members. Design/methodology/approach: The present research focuses on the mechanical testing of cylindrical, enamel and honeycomb-shaped parts fabricated through multi-jet printing (MJP) process with a wall thickness of 0.26, 0.33, 0.4 and 0.66 mm. The polymer specimens (for tensile, compression and shear tests) were fabricated using a multi-jet fusion process. The experimental results were compared with the numerical modelling. Finally, the optimal geometry was obtained, and the influence of wall thicknesses on various mechanical properties (tensile, compression and shear) was studied. Findings: In comparison to cylindrical, enamel structures the honeycomb structures required less time to fabricate and had lower tensile, compressive and shear strengths. The most efficient geometry for fully functional parts where tensile, compressive and shear forces are present during application – cylindrical geometry is preferred followed by enamel, and then honeycomb. It was found that as the wall thickness of various geometries was increased, their ability to withstand tensile, compressive and shear loads also enhanced. The enamel shape structure exhibits greater strain energy storage capacity than other shape structures for compressive loads, and the strength to resist the compressive load will be lower. In the case of cylindrical geometries for tensile loading, the resisting area toward the loading will be higher in comparison to honeycomb- and enamel-based structures. At the same time, the ability to store the stain energy is less. The results of the tensile, compression and shear load finite element analysis using ANSYS are in agreement with those of the experiments. Originality/value: From the insight of literature review, it is found that a wide range of work is done on fused deposition modeling (FDM) process. But in comparison to FDM, the MJP provide the better dimensional accuracy and surface properties (Lee et al., 2020). Therefore, it is observed that past research works not incorporated the effect of wall thickness of the embedded geometries on mechanical properties of the part fabricated on MJP (Gibson, n.d.). Hence, in this work, effect of wall thickness on tensile, compression and shear strength is considered as the main factor for the honeycomb, enamel and cylindrical geometries. [ABSTRACT FROM AUTHOR]

Cellular infill structures such as honeycomb have been widely used in the field of light weighting. In recent years, the emergence of additive manufacturing technologies has provided a new solution to fabricate complicated cellular infill structures. This paper presents a continuous printing path planning method for gradient honeycomb structures. Given a 2D filling region represented by a polygon, a honeycomb graph that covers the filling area is trimmed to generate an infill pattern. Then an algorithm is proposed to transform the honeycomb filling pattern into an Eulerian graph, which can be traversed by a single-stroke printing path. For each honeycomb, double-spiral paths are used to generate gradient honeycomb structures with varying wall thicknesses. Later, the 2D honeycomb infills are generalized to 3D cases that are suitable for multi-axis printing. First, three mutually orthogonal vector fields that are embedded on the tetrahedral mesh of the printed part are generated by considering the support-free condition. Then the three vector fields are used to calculate three monotonically increasing scalar distance fields, which span a non-Euclidean space. Finally, the 2D honeycomb infills are generated in the non-Euclidean space with parallel sliced layers, which are then mapped back to the Euclidean space to obtain the real self-supporting 3D honeycomb infills. The proposed 2D/3D honeycomb infill structures generation algorithms have been verified by both simulation and experimental tests. [ABSTRACT FROM AUTHOR]

Over the years, the building envelope has evolved from a protective barrier element to a complex filter system capable of optimizing the interactions between the external and internal environments. An efficient envelope reacts flexibly to variable external conditions, minimizing heat losses in the winter season. Therefore, insulating materials play a fundamental role in building's thermal performance. In this scenario, Additive Manufacturing represents an emerging and promising solution for the construction sector. Three-dimensional printing allows the creation of custom geometries, reduces material waste, and automates the construction process. This work aims to compare the thermal performance of a PLA (polylactic acid) 3D-printed block with an internal honeycomb structure whose air cavities are filled with natural and recyclable waste-insulating materials. The selected air cavity filling materials are (i) wood sawdust, (ii) sheep's wool, and (iii) hemp. The thermal behavior of the block with the different filling materials was experimentally tested via Heat Flow Meter (HFM) method in a controlled environment (Hot Box). The results showed that the introduction of waste material significantly improved the thermal performance of the 3D-printed block compared to the case of air cavities. A thermal transmittance (U-value) reduction of up to 57% was obtained. Moreover, the sheep's wool showed the best performance, with a U-value equal to 0.53 ± 0.02 W/m2K, i.e., 18.5% less than the wood sawdust and 19.7% less than hemp. [ABSTRACT FROM AUTHOR]

Aerogels, shaped as fibers, films, as well as monoliths, have demonstrated a plethora of applications in both academia and industry due to charming properties including ultralow density, large specific surface area, high porosity, etc., however studies on more complicated aerogel forms (e.g., honeycombs) with more powerful applications have not been fully explored. Herein, the Kevlar aerogel honeycomb is firstly constructed through a dry ice‐assisted 3D printing method, where the Kevlar nanofiber ink is printed directly in dry ice freezing atmosphere, followed by supercritical fluid drying. The subsequent 3D Kevlar/shear‐stiffening gel (SSG) honeycomb (3D‐KSH) can be obtained by selective nanoconfining of SSG into nanopores of the aerogel skeleton wall (with the loading amount of 93 wt%) rather than into open honeycomb channels, solving the leakage, creep deformation, and shape design infeasibility of the SSG. Combining the advantages of Kevlar, honeycomb and SSG, the fabricated 3D‐KSH shows obvious smart responsive behavior to external stimulus. Additionally, the 3D‐KSH has high strain rate sensitivity (sensitivity factor of 4.16 × 10−4) and excellent impact protection performance (energy absorption value up to 176 J g−1 at the strain rate of 6300 s−1), which will significantly broaden application prospect in some intelligent protection fields. [ABSTRACT FROM AUTHOR]

Honeycomb cores are widely used in the aerospace and automotive fields as a part of protective structures. Unfortunately, standard prismatic honeycomb cores offer a limited amount of energy absorption under lateral loads and suffer from degradation of their impact-deadening properties when their dimensional scale is increased. In this work, a multiscale study on energy absorption under quasi-static load is carried out on 3D-printed honeycomb core samples constituted by a variable section and compared to the cases of standard hexagonal honeycomb samples having the same mass and external dimensions. When doubling the dimensional scale in the case of lateral loads, the novel core geometry showed a substantial absence of specific energy absorption degradation, whereas the hexagonal core suffered from a 12.2%-degradation. Furthermore, by increasing the dimensional scale, the novel core geometry shows a delay in the densification onset. The variable-core geometry showed an average increase, in terms of energy absorption under lateral loads, of 46.8% for the regular scale and 71.4% for the double scale. Under axial loads, a 12.4%-decrease in energy absorption was observed for the samples with novel geometry, which, nevertheless, showed a relatively constant profile of reaction force under compression: this property could potentially allow it to avoid pre-crushing. [ABSTRACT FROM AUTHOR]

3D printing technology is the new frontier in building construction. It is especially useful for making small structures within a short period. Full construction, including interior partitions and exterior façades, can be achieved with this technology. This paper proposes a parametric Voronoi tessellations model for quickly generating and fabricating 3D-printed hexagonal honeycomb partitions for interior design. Comprehensive experimental testing was conducted to characterize the mechanical properties and investigate the energy absorption characteristics of the proposed 3D-printed hexagonal honeycomb while comparing it to alternative hexagonal honeycomb structures. The tests included tensile testing (ASTM-D638) of the printed Polylactic Acid (PLA) material, especially with the almost total absence of conducted research that reported mechanical properties for 3D printed material with low infill percentages such as 10%. In addition, an in-plane quasi-static axial compression testing of the lightweight honeycomb structures was also conducted on the printed structure with the same low infill percentage. Compared to non-Voronoi honeycomb structures, the Voronoi honeycomb resulted in superior mechanical and energy absorption properties with energy absorption values ranging from 350 to 435 J and crash force efficiency being 1.42 to 1.65.

Continuous fiber reinforced polymer composites are widely used in load-bearing components and energy absorbers owing to their high specific strength and high specific modulus. The path planning of continuous fiber is closely related to its structural defects and mechanical properties. In this work, continuous fiber reinforced polymer honeycomb structures (CFRPHSs) with different printing paths were designed and fabricated via the fused deposition modeling (FDM) technique. The investigation of fiber dislocation at path corners was utilized to analyze the structural defects of nodes caused by printing paths. The lower stiffness nodes filled with pure polymer due to fiber dislocation result in uneven stiffness distribution. The bending performance and deformation modes of CFRPHSs with different printing paths and corresponding pure polymer honeycomb structures were investigated by three-point bending tests. The results showed that the enhancement effect of continuous fibers on the bending performance of honeycomb structures was significantly affected by the printing paths. The CFRPHSs with a staggered trapezoidal path exhibited the highest specific load capacity (68.33 ± 2.25 N/g) and flexural stiffness (627.70 ± 38.78 N/mm). In addition, the fiber distributions and structural defects caused by the printing paths determine the stiffness distribution of the loading region, thereby affecting the stress distribution and failure modes of CFRPHSs.

Polymer‐filled honeycomb composites are composite materials that exhibit effective in‐plane moduli greater than either the honeycomb or polymer alone. Previous numerical modeling work by the authors has identified two key mechanisms by which this stiffness amplification is achieved. For thin honeycomb cells, the difference in Poisson's ratio between the infill and honeycomb drives the in‐plane composite behavior. For large cell depths, the volume change of the hexagonal cells, acting on the infill polymer, is the dominant factor in stiffness amplification. This work aims to extend these findings to thick walled honeycombs, and to experimentally validate the model predictions while making comparisons to existing analytic models. A unit cell finite element model is created for the composite, with isotropic material properties for the honeycomb and infill obtained from characterization tests on 3D printed honeycomb wall material and polyurethane elastomer infill materials. An experimental investigation is completed, where both empty and polymer filled honeycomb samples are 3D printed and tested for a range of cell geometries, varying the cell angle, cell depth, and infill polymer, and are testing in two in‐plane loading directions. The results support both the model predictions of the effective Young's moduli and the mechanisms of stiffness amplification previously found, with a maximum percent error of 16.9% found and an amplification factor of the infill modulus of up 16 demonstrated. The improved understanding demonstrated in this work supports the use of these composites in applications where reinforcement of the honeycomb by a polymer, or vice versa, is desired. [ABSTRACT FROM AUTHOR]

The gradient honeycomb structures absorb a wide range of energy, but a systematic study on anisotropic design is lagged. The same justify the novelty of the current work, wherein the honeycomb design of anisotropic gradient honeycomb structure comprises its originality. The gradient 3D-printed honeycomb structures fabricated samples were subjected to a static and cyclic compression test in the in-plane direction, and the energy absorption capabilities were analyzed. The cyclic compression and free vibration test confirmed the highest damping ability attributed to hybrid gradient structure. A high damping ability demonstrates application possibilities as an efficient and effective energy absorption element and other technical curiosity. [ABSTRACT FROM AUTHOR]

A time-dependent understanding of swelling characteristics and external stimuli behavior is crucial for the development and understanding of functional hydrogels. Magnetic resonance imaging (MRI) offers the opportunity to study three-dimensional (3D) soft materials nondestructively. This technique is already widely used as an image-based medical diagnostic tool and is applied here to evaluate complex structures of a hydrogel—a double network of chemically crosslinked casein enhanced with alginate—fabricated by 3D printing. When hydrogel disks immersed in four different liquid systems were analyzed, the material exhibited distinct system-dependent behavior characterized by rheological and mechanical measurements. Further material functionalization was achieved by macroscopic structuring of the hydrogel as an auxetic material based on a re-entrant honeycomb structure. MRI offers the advantage of monitoring overall changes in the area of the analyzed specimen and internal structural changes simultaneously. To assess the behavior of this complex structure, a series of short MRI measurements, each lasting 1.7 min, captured liquid diffusion and thus structural swelling behavior. A clear dependence of external and internal structural changes as a function of liquid properties causing these changes was observed. In conclusion, this approach might pave the way for prospective applications to monitor liquid diffusion into (e.g., vascularization) and swelling behavior of functional hydrogels. [ABSTRACT FROM AUTHOR]

To develop a composite filament with an electromagnetic-wave-absorbing function suitable for 3D printing, we combined thermoplastic polyurethane (TPU) as the matrix material and carbonyl iron powder (CIP) as the absorbing agent to prepare TPU/CIP composites by melt blending. The composites passed through a single-screw extruder to obtain a filament with 2.85 mm in diameter. Different absorber structures were printed using fused deposition modeling, and their absorption properties were tested using the bow method. The results showed that by increasing CIP content, the electromagnetic-wave absorption performance gradually improved, while the mechanical properties substantially decreased. When the mass fraction of the CIP was 60%, the TPU/CIP composite showed good absorption properties and could be prepared into a filament that met the requirements for fused deposition modeling. Simulation results of plate-wave-absorption performance showed that, when the plate thickness was 3 mm, the minimum reflection loss was −21.98 dB, and the effective absorption bandwidth (for reflection loss below −10 dB) was 3.1 GHz (4.55–7.65 GHz). After the TPU/CIP composite was printed into honeycomb, pyramid, and other absorber structures, the absorption performance was further improved. For a structure printed with a gradient-wall honeycomb structure at 3 mm thickness, the effective absorption bandwidth was 4.64 GHz (8.48–13.12 GHz), and the minimum reflection loss was −36.69 dB. The effective absorption bandwidth of the pyramid structure reached 15.88 GHz (2.12–18 GHz), and the minimum reflection loss was −49.75 dB. [ABSTRACT FROM AUTHOR]

This paper proposes an innovative class of two-and-a-half dimensional (2.5D) hybrid continuous fiber reinforced lattice structures (CFRLSs) that rationally combine distinct lattice designs to leverage the tensile strength of fibers for achieving superior compression performance. These hybrid structures are fabricated through a self-supporting suspension printing (SSSP) method, which enables the fabrication of suspension structures across substantial gaps through continuous fiber 3D printing (CF-3DP). The compression behavior of the proposed 2.5 D hybrid CFRLSs was optimized by focusing on two key variables in hybridizing the basic lattice along the build direction: composition ratio and distribution strategy. Finite element and analytical models were developed to elucidate their three failure mechanisms and related control strategies. Compared to the conventional single-type structure, i.e., honeycomb design, the proposed hybrid structures show a substantially higher compression performance, with improvements of up to 141.3 % and 330.1 % in specific strength and modulus, respectively, even at a lower density. This hybrid lattice design method based on SSSP opens up new horizons for engineering high-performance CFRLSs with superior compression performance by fully exploiting the design freedom offered by CF-3DP. [Display omitted] [ABSTRACT FROM AUTHOR]

• The CFRCs honeycomb sandwich structures are fabricated integrally by 3D printing technique. • The damage types at each stage of the flatwise compression process of 3D printed CFRCs honeycomb sandwich structures are successfully characterized. • A 3D printing method for CFRCs honeycomb sandwich structures with multilayer sandwich and core/panel variable printing thickness is proposed. • The compressive strength and energy absorption capacity of multilayer CFRCs honeycomb sandwich structures have obvious advantages. Continuous fiber reinforced composites (CFRCs) 3D printing technology has the advantage of integrated fabricating for honeycomb sandwich structures, the load-bearing capacity of the fabricated honeycomb sandwich structures still needs to be investigated and improved. This study aims to reveal compression failure modes of 3D printed CFRCs honeycomb sandwich structures with various internal configurations by conducting flatwise compression tests. The deviations of single-layer CFRCs honeycomb cores with different core sizes and core heights and their impacts on the compression failure process were analyzed. A 3D printing method with multilayer cores and core/panel variable printing thickness was proposed, and the effects of multilayer core structure and different core printing parameters on the compressive properties of honeycomb sandwich structures were investigated. The results showed that interlayer cracking caused by core buckling deformation was the leading cause of failure of 3D printed CFRCs honeycomb sandwich structures when subjected to compression. The core buckling deformation could be suppressed by printing multilayer cores and using low core printing thickness, and the compression strength and specific energy absorption of the sandwich structures reached 38.1 MPa and 25.4 kJ/kg, respectively. This study provides guidance for the customization of the 3D printing process of CFRCs honeycomb sandwich structures. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Bioinspired design was used to ceramic materials via DIW technique. • Polysilazane (PSZ) based ceramic materials were printed by DIW 3D printing. • B 4 C-based honeycomb ceramic 3D structures were printed by PSZ/B 4 C ink. • B 4 C-based honeycomb ceramic was impregnated by epoxy resin for armor structures. B 4 C ceramic holds enormous application potential in the lightweight armors. In order to simplify the design of armor materials, 3D printed B 4 C-based honeycomb ceramic via DIW technique with high solid content were fabricated using printing ink with B 4 C powder, BYK-2070 dispersant, BAC solvent, PSZ adhesive and DCP cross-linking agent. The role of each constituent and the printing parameters of such honeycomb ceramic were investigated. In addition, epoxy resin was employed to impregnate PSZ-modified B 4 C-based honeycomb ceramic to prepare three-dimensional structure hybrid composites with excellent mechanical strength (172 MPa of flexural strength, 4.95 KJ/m2 of impact strength) and physiochemical properties (7.52 % of open porosity, 5.5 % of water absorption, 1.35 g/cm−1 of density, and 5.2 GPa of hardness). The exceptional performances of the three-dimensional structure hybrid composite come from the bioinspired structure design, new chemical bonds (such as the formation of B–C, C–N and Si–B bonds) formed in the ceramic material and cross-linking reaction occurred during curing between epoxy resin and PSZ. The findings in this study provide an effective strategy for the fabrication of B 4 C-based composites with controllable structures and mechanical performances and exhibit the potential application in complex armor structures. [ABSTRACT FROM AUTHOR]

In this paper, we briefly reviewed the development of cranial windows and their functions in brain sciences. We demonstrated that a 3D-printed titanium frame coated with a polydimethylsiloxane (PDMS) film could serve as an excellent transparent cranial window for long-period, in vivo optical experiments in mice and rats, and the devices also allowed multiple injections through the elastic PDMS window, without leaking. Our large-area honeycomb structured Ti-PDMS samples had a relative transparent area ratio of over 90% but a mechanical strength close to that of a human skull, showing a promising potential for applications in large animals as multifunctional cranial windows. We also suggested that more functional modules could be integrated in the large-area Ti-PDMS cranial device, thus turning it into a novel wearable smart platform for wireless data communication, electro-probing and brain stimulation, optical imaging, transcranial injection, and so on, for both fundamental research on neuroscience and clinical practices dealing with brain damage and disease. [ABSTRACT FROM AUTHOR]

The advancement of 3D-printing technology has ushered in a new era in the production of machine components, building materials, prototypes, and so on. In 3D-printing techniques, the infill reduces the amount of material used, thereby reducing the printing time and sustaining the aesthetics of the products. Infill patterns play a significant role in the property of the material. In this research, the mechanical properties of specimens are investigated for gyroid, rhombile, circular, truncated octahedron, and honeycomb infill structures (hexagonal). Additionally, the tensile properties of PLA 3D-printed objects concerning their infill pattern are demonstrated. The specimens were prepared with various infill patterns to determine the tensile properties. The fracture of the specimen was simulated and the maximum yield strengths for different infill structures and infill densities were determined. The results show the hexagonal pattern of infill holds remarkable mechanical properties compared with the other infill structures. Through the variation of infill density, the desired tensile strength of PLA can be obtained based on the applications and the optimal weight of the printed parts. [ABSTRACT FROM AUTHOR]

The development of microwave absorbing technology raises the demands for all-band absorption. The topological structures expand the frequency range of electromagnetic wave absorption and eliminate the differences caused by scattering in different incident directions. The multi-wall carbon nanotube and carbonyl iron particles were mixed with polylactic polymer to fabricate filaments for fused deposition. The distribution characteristics of the structures using carbonyl iron/carbon nanotube hybrid material for the key absorption frequency band are obtained. The reflectivity of the honeycomb structure in X and Ku bands is verified experimentally through the preparation method of fused deposition modeling 3D printing. With the decrease of the fractal dimension number, the electromagnetic loss performance basically increases. Preliminary research results showed that the topological structure could significantly expand the absorbing frequency range, and the effective frequency band less than −10 dB is 2–40 GHz, which has a clear application potential for radar absorption. [ABSTRACT FROM AUTHOR]

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This paper presents the results of FEM (Finite Element Method), CFD (Computational Fluid Dynamics) and modal analyses of model semi-axial pump. Two sets of impeller blades were printed by metal 3D printing technology with internal honeycomb structures. The set of solid blades, manufactured by CNC machining for a comparison, was also included. 3D printed blades were designed with internal structures in order to save material, and with respect to mechanical and dynamic properties. Saved material can change the starting moment, modulate modal properties or decrease strength properties. The 3D printed blades can be produced very quickly and with accurate blade surface finish. One of the reasons of this approach can be the use of 3D printed blades as spare parts for industrial applications or for model pump research. This paper contains short introduction to blade design with internal honeycomb structures and their one-way FSI analyses (Fluid Structure Interaction). The final results of best design are presented and discussed. [ABSTRACT FROM AUTHOR]

• A central self-similar strategy is proposed to develop bio-inspired honeycombs. • Central self-similar degradable polymer honeycombs are additively manufactured. • The interaction effect of different connections between the two walls can promote EA. • Theoretical models of the proposed central self-similar honeycombs are built. At present, improving the energy absorption capacity of lightweight degradable polymer honeycombs is crucial for one of the future engineering applications and bio-inspired strategy based on hierarchy is considered an efficient method for designing honeycomb structures. To improve the energy absorption performance and stability of polymer honeycombs, this study develops three central self-similar bio-inspired honeycombs combining the microstructure of horsetails and designs different connections between the two walls and connecting structures for the central self-similar honeycombs. Bio-inspired honeycombs are fabricated using toughened polylactic acid (PolyMax™ PLA) through fused deposition modelling and subjected to axial compression tests. The finite element (FE) models of the bio-inspired honeycombs are developed to simulate the axial compression process and verified with experimental results. Results show that the connecting structures distributed on the outer wall of the central self-similar honeycombs considerably improve the energy absorption performance of the bio-inspired honeycombs. In the double-cell honeycombs, connecting structures interact with the cell walls, leading to the formation of more folding lobes on the cell walls and increased cell wall utilisation. Furthermore, the effects of geometrical parameters on the energy absorption performance of the bio-inspired honeycombs are investigated. Suitable connecting structure size and cell wall thickness can improve the energy absorption performance and stability of the honeycombs. In addition, the theoretical calculation models of the three bio-inspired honeycombs are established, and the errors with the FE calculation results are within 6 %, which verifies the accuracy of the theoretical models. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Heterogeneous honeycombs with bio-inspired line defects are designed and analyzed. • Structure with octagon-pentagon defects own 12.7% higher Young's modulus than the benchmark. • The structure with pentagon-trigon defects exhibit about 56.5% higher SEA than the benchmark. • Composite-lattice honeycombs own non-uniform collapse bands under compression. Taking inspiration from geometric defects in hexagonal lattices existing in nature (beehive and graphene), this work explains how defects in the form of channels can improve the effective Young's modulus and specific energy absorption properties of hybrid-lattice hexagonal honeycombs under compression due to non-uniform collapse band behavior and strain delocalization. The results reveal that in terms of effective Young's modulus, honeycombs with octagon-pentagon and pentagon-trigon defected cells outperform the benchmark structure by roughly 13% and 20%, respectively. In terms of specific energy absorption (SEA), all composite-lattice honeycombs show superior behavior to the benchmark honeycomb, especially the pentagon-trigon defective honeycomb with about 56.5% higher SEA. The novel structures show promising design prospects for applications in various industries, especially automotive and construction with cost-effective advantage in customized or low-volume production cases. [ABSTRACT FROM AUTHOR]

3D printing of continuous carbon fiber-reinforced composites relieves molds in composite manufacturing and gives flexibility to the design of lightweight and robust circular honeycomb structures. Nevertheless, how process defects affect the failure mechanisms of 3D-printed continuous carbon fiber-reinforced honeycomb structures remains undisclosed. To advance this research area, it requires a comprehensive investigation of the failure mechanisms and process defects of 3D-printed continuous carbon fiber-reinforced composite circular honeycomb structures (CCFRCCHSs), with particular attention to the influence of stacking orientations. In this study, 3D printing has been introduced to fabricate CCFRCCHSs using the identical composite material and geometry but different stacking orientations. Both in-plane and out-of-plane quasi-static compression experiments were carried out on these CCFRCCHSs. The mechanical properties and failure mechanisms were investigated through experimental analysis and cross-section observation, from which the microscopic voids and weak interfaces were identified as the dominating factors influencing the failure modes of CCFRCCHSs. This study provides insights into the association between process defects and failure mechanisms of 3D-printed CCFRCCHSs with different stacking directions, which offers guidance for the design of lightweight and robust composite circular honeycomb structures. [Display omitted] [ABSTRACT FROM AUTHOR]

• SiCN honeycomb ceramic is prepared from 3D printed photocurable polysilazane. • The optimal composition of acrylate and polysilazane affords high-strength ceramic. • Combination of acrylate and polysilazane results in high-content free carbon. • SiCN honeycomb ceramic has excellent intrinsic microwave-absorbing property. The combination of 3D printing technology and polymer-derived ceramic route provides an attractive strategy to construct microwave-absorbing honeycomb with fine structure through flexible process. However, preparation of honeycomb ceramics with both excellent mechanical and microwave-absorbing properties is still challenging. Herein, SiCN honeycomb ceramic was fabricated by stereolithography from UV curable polymeric precursor consisting of polysilazane and multifunctional acrylates. By optimizing the multifunctional acrylates and its ratio, the decomposition of organic moiety and the ceramization process of precursor are matched, rendering the achieved ceramic with high compactness. The hardness and specific compressive strength of SiCN honeycomb ceramic reach as high as 14.3 GPa and 333.3 MPa/(g·cm3), respectively. Meanwhile, at low pyrolysis temperature, the copolymerized acrylate and polysilazane that formed during curing process was converted to free-carbon nanodamins in-situ, which endows SiCN honeycomb ceramic with the minimum reflection loss of –49.0 dB, namely microwave absorption rate over 99.99%. [ABSTRACT FROM AUTHOR]

The use of 3D printing to produce acoustic panels with good mechanical and acoustic properties was investigated in this paper. Various fiber layups of the fiberglass face sheet and core designs were fabricated and tested for their indentation resistance and acoustic absorption performance. It was found that the bidirectional face sheet layup exhibited the best indentation energy absorption recording 4.2 J, which is 37% more than the 45-degree layout and 66% more than the quasi-isotropic layup. The specific energy absorption of the hybrid honeycomb core is the best among the three core designs recording 404 J/kg, which is 56% higher than the corrugated triangle with horizontal beam core (359 J/kg) and 20% higher than double ellipse core (335 J/kg). Computed-Tomography (CT) scan was used to study the fracture behavior of the sandwich structures. It was found that the bidirectional layup exhibited a different failure mode as compared to the 45-degree and quasi-isotropic layup. In terms of the acoustic properties, the face sheets with various layup patterns have a low acoustic absorption coefficient with minimal differences from each other at low frequencies (500 Hz–3000 Hz) and have higher absorption coefficients with greater differences from each other at frequencies between 3000 Hz–6500 Hz. The absorption curve was significantly affected by the design of the core. The orientation of the core also comes into play if the core is asymmetrical. The hybrid honeycomb sandwich structure was the optimal structure among the three designs for balanced indentation resistance and acoustic insulation. [ABSTRACT FROM AUTHOR]