Fused Filament Fabrication Technique Research Articles

Experimental investigation on tailoring compressive properties and energy absorption of 3D printed gradient star re-entrant hybrid auxetic structure

Purpose Fused filament fabrication (FFF) is a widely used 3D printing technique for the fabrication of mechanical metamaterials with intricate geometries. Gradient strategy is applied to geometric parameters of gradient star re-entrant hybrid auxetic (GSRA) structure. Deformation behaviour is studied under compressive loading. The purpose of this study is to investigate the influence of gradient geometric parameters on mechanical properties, namely, specific strength (SS), specific modulus (SM) and specific energy absorption (SEA). Design/methodology/approach Response surface methodology (RSM) is implemented for the design of experiments of gradient geometric parameters to minimize the number of experimental tests. Acrylonitrile butadiene styrene material is used for the fabrication of GSRA structures by FFF technique. The best set of gradient parameters has been optimized maximizing all three responses using RSM and artificial neural network optimization technique. Findings During compressive testing, row-wise deformation is observed with two-stage plateau regions, which results in increase in SEA of the structure. Furthermore, based on analysis of variance and 3D response plots, it is found that height gradient is the most influencing gradient geometric parameter on SS and SM, whereas the wall thickness gradient has maximum influence on SEA. Meanwhile, the interaction effect of wall thickness gradient and height gradient has maximum influence on SS, SM and SEA. Research limitations/implications This study of applying gradient strategy to geometric parameters is limited to GSRA structure under compressive loading. In addition, findings are valid within the selected range of gradient geometric parameters. These findings are useful for the selection of gradient geometric parameters to maximize SS, SM and SEA of GSRA structure simultaneously. These outcomes pave the way for designing light-weight gradient hybrid auxetic structures in the field of construction, aerospace, automobile and biomedical engineering. Originality/value Limited experimental study is available on investigating the influence of gradient geometric parameters on mechanical properties, namely, SS, SM and SEA, and deformation behaviours of hybrid auxetic structures. This study directly addresses the above research gaps.

Architecture influence on acoustic performance, EMI shielding, electrical and thermal, properties of 3D printed PLA/graphite/molybdenum disulfide composites

Fused Filament Fabrication (FFF) is one of the most emerging techniques nowadays. Affordable, easy to use, economical, for a broad audience − from specialists to home users. These are only several of its advantages. A disadvantage is the limited number of available filament types, especially those with high performance. Therefore, the aim of the work was to investigate the properties of custom–made filament printouts based on polylactic (PLA), graphite (G) and molybdenum disulfide (MoS2).This work looked at structural and thermal analysis, acoustic performance, EMI shielding, and electrical and thermal properties, including thermal conductivity and heat diffusivity. The following were considered during the study: type of printing architecture, infill density, and filament formulations. Among the best values, which were obtained for the highest loaded sample based on 15 wt% graphite and 2 wt% MoS2 (G15/M2), where EMI shielding effectiveness surpassed SETOT ∼ 17 dB (per 1 mm sample thickness), electrical conductivity remained at a low level. It exceeded σ ∼ 0.2 S/m; thermal conductivity was slightly over κ ∼ 0.4 W/mK, and heat diffusivity was almost α ∼ 0.4 mm2/s.This work is the first step in designing high-performance materials dedicated to advanced applications based on the FFF technique.

Mechanically suitable and osteoinductive 3D-printed composite scaffolds with hydroxyapatite nanoparticles having diverse morphologies for bone tissue engineering.

The challenge of integrating hydroxyapatite nanoparticles (nHAp) with polymers is hindered by the conflict between the hydrophilic and hygroscopic properties of nHAp and the hydrophobic properties of polymers. This conflict particularly affects the materials when calcium phosphates, including nHAp, are used as a filler in composites in thermal processing applications such as 3D printing with fused filament fabrication (FFF). To overcome this, we propose a one-step surface modification of nHAp with calcium stearate monolayer. Moreover, to build the scaffold with suitable mechanical strength, we tested the addition of nHAp with diverse morphology-spherical, plate- and rod-like nanoparticles. Our analysis showed that the composite of polycaprolactone (PCL) reinforced with nHAp with rod and plate morphologies modified with calcium stearate monolayer exhibited a significant increase in compressive strength. However, composites with spherical nHAp added to PCL showed a significant reduction in compressive modulus and compressive strength, but both parameters were within the applicability range of hard tissue scaffolds. None of the tested composite scaffolds showed cytotoxicity in L929 murine fibroblasts or MG-63 human osteoblast-like cells, supporting the proliferation of the latter. Additionally, PCL/nHAp scaffolds reinforced with spherical nHAp caused osteoactivation of bone marrow human mesenchymal stem cells, as indicated by alkaline phosphatase activity and COL1, RUNX2, and BGLAP expression. These results suggest that the calcium stearate monolayer on the surface of the nHAp particles allows the production of polymer/nHAp composites suitable for hard tissue engineering and personalized implant production in 3D printing using the FFF technique.

Mechanical and tribological behaviour of three-dimensional printed almond shell particles reinforced polylactic acid bio-composites

Recently, composite filament development for three-dimensional printing has emerged and is used for numerous applications. The present research work develops neat polylactic acid and Almond Shell Particles reinforced polylactic acid bio-composites for three-dimensional printing and investigates the effects of printing orientation, including 0°, 45° and 90° orientation, on the tribological and mechanical behaviours of three-dimensional printed materials. The novel almond shell particles reinforced polylactic acid filaments are extruded by the filament extrusion method with the presence of 10% almond shell particles in the polylactic acid matrix, and the samples are three-dimensional printed by the fused filament fabrication technique. Mechanical characteristics such as tensile, flexural, compressive strength, and shore hardness are evaluated with respect to various three-dimensional printing orientations. The surface quality of the three-dimensional printed polylactic acid composite samples is analysed with respect to length and diameter deviation. Length accuracy of the 90° oriented polylactic acid and almond shell particles reinforced polylactic acid bio-composite samples exploits a better accuracy of 99.12% and 98.81%, respectively. It is shown that adding almond shell particles to the polylactic acid matrix decreases the flexural and tensile strength. Among the printing orientations, 0° flat samples result in the maximum tensile strength of 36 and 28 MPa for the neat polylactic acid and almond shell particles reinforced polylactic acid composites, respectively. The lowest contact angle of 54° is observed on the almond shell particles reinforced polylactic acid bio-composites three-dimensional printed with a 90° orientation. The highest contact angle value of 94° is observed on the neat polylactic acid three-dimensional printed with a 0° printing orientation. A tribological study is carried out under dry conditions on the pin-on-disc tribometer by varying the sliding speed (1, 2, and 3 m/s) and load (10, 20, and 30 N). The result shows that the lowest coefficient of friction of 0.22 is achieved for the almond shell particles reinforced polylactic acid bio-composite samples with a 0° printing orientation under a sliding load of 10 N. These kinds of newly developed compostable materials can be used for developing disposable orthotic foot appliances.

The process‐structure–property relationship of 3D printed G‐Polymer using fused filament fabrication technique

AbstractThe ever‐increasing demand for additive manufacturing (AM) is driven by the technology's rapid prototyping and flexible manufacturing benefits. Among the various AM techniques, fused filament fabrication (FFF) is one of the most commonly used techniques, in which thermoplastic polymer filaments are deposited layer by layer to create the final part. This technique has been used extensively in various sectors. However, new materials have yet to be developed for use in FFF. This research aims to introduce a new biodegradable highly amorphous polyvinyl alcohol (HAVOH), commercially known as G‐Polymer (GP), into the scope of FFF, to propose a process window for the fabrication of parts with enhanced mechanical properties and to discover the process‐structure–property relationship for this material. This study investigates the effect of five key parameters in GP FFF, including raster angle, number of contours, nozzle temperature, build platform temperature, and print speed. The results of the chemical, thermal, and thermo‐mechanical analysis of the filaments before and after hot extrusion of the 3D printer nozzle showed a significant increase in the mechanical properties of the hot‐extruded filaments. In addition, the mechanical characterization of 3D printed parts showed that increasing the number of contours can improve the mechanical properties of parts, while the raster angle can have a complex effect. The mechanical properties of the parts are also improved by reducing the temperature of the nozzle and the build platform. Printing speed, as an essential parameter in AM, was related to the previously mentioned parameters, and the results showed that increasing the printing speed could improve the UTS and Young's modulus of the 3D printed part.Highlights A novel biodegradable polymer (HAVOH) was introduced into the scope of FFF. The hot extruded G‐Polymer filament from the nozzle showed improved mechanical properties. 180°C nozzle and room temperature platform resulted in improved mechanical properties. 3D printed parts with +45°/−45° raster angle show improved mechanical properties 110 mm/s print speed results in higher mechanical strength than 70 mm/s print speed.

Tensile fatigue behavior of short and continuous carbon fiber reinforced additively manufactured thermoplastic multiscale composite

Fiber reinforced multiscale composites represent a cutting-edge class of advanced materials that have garnered significant attention in the realm of materials science and engineering. These advanced materials intertwine various fiber reinforcements, meticulously tailored at micro, to macro levels, imparting them with remarkable mechanical, thermal, and functional properties. In this research, an experimental investigation was performed to observe the tensile fatigue behavior of short and continuous carbon fiber reinforced additively manufactured multiscale thermoplastic composites. The multiscale composite was fabricated by combining layers of continuous woven carbon fiber (CCF) with short carbon fiber (SCF) reinforced acrylonitrile butadiene styrene (ABS) laminates which were additively manufactured using the fused filament fabrication technique. It was observed that the multiscale composite exhibits a maximum 127% higher strength and 154% higher Young’s modulus than neat ABS polymer. Based on non-normalized stress-life curves, multiscale composites with four layers of CCF have a higher fatigue strength than multiscale composites with one layer of CCF. However, when the applied stress is normalized by the quasi-static strength, the multiscale composite with one layer of CCF had a longer fatigue life than the four layers of CCF reinforced multiscale composites at high normalized cyclic stress, while the multiscale composite with four layers of CCF exhibited a longer fatigue life at low normalized cyclic stress. The four CCF layers reinforced multiscale composites experienced a different extent of fiber pull-out, matrix cracking, and delamination at different stress levels. Conversely, fatigue failure of the one layer of CCF reinforced multiscale composites primarily occurred due to localized fiber breakage with minimal matrix-related damage.

Electrically conductive and flexible filaments of hot melt adhesive for the fused filament fabrication process

Fused filament fabrication technique is the most popular additive manufacturing that has received extensive attention, revolutionizing industrial production processes. In addition to the standard thermoplastic polymers, much emphasis is placed on developing electrically conductive functional filaments being the most interesting. While there are conductive filaments that are commercially available, the market lacks a wide range of flexible options. Hence, this paper presents innovative filaments based on the combination of thermoplastic hot melt copolyester adhesive (HMA) with multi-walled carbon nanotubes (MWCNT). The incorporation of carbon nanotubes into the HMA was carried out through a two-step process. First, a masterbatch of 10 wt. % MWCNT was diluted with pure polymer using a half-industrial twin-screw extruder to obtain concentrations in the range of 1–9 wt. %. Consequently, the nanocomposite pellets were extruded again into the form of filaments. The rheological analysis demonstrates that adding MWCNT to the HMA increases both the viscous and elastic behavior of the composites. The homogenously dispersed nanotubes in the polymer matrix led to electrical conductivity of 1.39 S/m for the filaments containing 10 wt. % MWCNT. They are also characterized by the stiffness and tensile strength of about 300 and 13 MPa, respectively. With high thermal stability up to 360 °C, low porosity, and high flexibility, the developed filaments are suitable for 3D printing. The printability of all filaments was confirmed, exhibiting lack of breakage during printing and visibly better quality of the parts with the higher nanotube content.

Modeling of Effect of Infill Density Percentage on Rotating Bending Fatigue Behavior of Additive-Manufactured PLA Polymers.

Nowadays, 3D PLA-printed parts are widely used in many applications, essentially using the fused filament fabrication technique. While the influence of printing parameters on quasi-static mechanical characterization has been extensively considered within the literature, there are limited accounts of this effect on fatigue performance. The two main aims of this research are first to investigate the effects of the infill density percentage on the fatigue life of dog-bone samples under rotating bending cycling loads, and second to model the fatigue life using Wöhler and Basquin models. The experiments exhibit a high variability of results, especially for low cyclic loads. The S-N curves show that the number of cycles at failure increases with the increase in the infill density percentage and decreases with the increase in loads. Investigations allow the formulation of each constant model as a function of the infill density percentage. The new fatigue model formulations exhibit good agreement with the experimental data. As an outcome of this study, the fatigue model for 3D-printed parts may be expressed as a function of the infill density percentage using fewer tests in the future and for other polymers used in fused filament fabrication.

Three-Dimensional Printing of Shape Memory Liquid Crystalline Thermoplastic Elastomeric Composites Using Fused Filament Fabrication.

Liquid crystalline elastomers (LCEs) are stimuli-responsive materials utilised in shape memory applications. The processability of these materials via advanced manufacturing is being paid increasing attention to advance their volume production on an industrial scale. Fused filament fabrication (FFF) is an extrusion-based additive manufacturing (AM) technique that offers the potential to address this. The critical challenge, however, is the rheological characteristics of LCEs that need to be tuned to achieve a facile processability through the extrusion-based method. In this work, new filaments of liquid crystalline thermoplastic elastomer (LCTPE) and its composites with lignin were made by the ternary system of LCE, thermoplastic polyurethane (TPU), and lignin. The results showed that TPU improves the melt flow index of the LCTPE system to approximately 10.01 g/10 min, while adding lignin further enhances the value of this index for the composites up to 21.82 g/10 min. The microstructural analysis indicated that the effective distribution of lignin and reduced domain size of the LCEs in the ternary blend contribute to the enhanced flowability of this filament through 3D printing. Samples of 3D-printed LCTPE and LCTPE/lignin composites maintained their shape memory characteristics via thermomechanical activation. Full shape recovery of the new LCTPE matrix and its composites with lignin was achieved in 39 s and 32 s at 130 °C, followed by 28 s and 24 s at 160 °C, respectively. The successful fabrication of LCTPE and LCTPE/lignin composite samples through 3D printing demonstrates a potential procedure for processing these shape memory materials using the FFF technique, and lignin offers a sustainable and cost-effective material solution that enhances the properties of this composite material.

Thermal stabilization of recycled PLA for 3D printing by addition of charcoal

Poly(lactic acid) (PLA) is one of the most widely used thermoplastic materials for 3D printing, particularly in the Fused Filament Fabrication technique. However, the printing process generates waste products and even though PLA is compostable, the possibility of recycling it provides ecological and economical benefits. In this work, a study on the stabilization of recycled PLA using charcoal (CC) was carried out, with the aim of overcoming the well-known problem of degradation (reduction in molecular weight) of PLA, during remelting. Microscopic investigations showed good dispersion of the filler in the polymer matrix, as well as better adhesion between the printed layers. Thermal analyses (Differential scanning calorimetry and thermogravimetry) indicate a stabilization of PLA waste because of the addition of small concentrations of CC to the recycled polymer matrix. These data are confirmed by GPC analyses, which show that the addition of filler is associated with higher molecular weight. Mechanical analysis indicated improved elongation at break and elasticity. Finally, a key ring was printed as an example of the better printability of the filament containing CC. The results indicate that a stabilization of the recycled PLA with a very low concentration of CC has been achieved. Improved 3D printability and properties of the 3D printed objects can be attained through recycling and recovery of wasted PLA, according to sustainability and circular economy matters.

Performance and Durability of Non-Stick Coatings Applied to Stainless Steel: Subtractive vs. Additive Manufacturing.

This study compares subtractive manufacturing (SM) and additive manufacturing (AM) techniques in the production of stainless-steel parts with non-stick coatings. While subtractive manufacturing involves the machining of rolled products, additive manufacturing employs the FFF (fused filament fabrication) technique with metal filament and sintering. The applied non-stick coatings are commercially available and are manually sprayed with a spray gun, followed by a curing process. They are an FEP (fluorinated ethylene propylene)-based coating and a sol-gel ceramic coating. Key properties such as surface roughness, water droplet sliding angle, adhesion to the substrate and wear resistance were examined using abrasive blasting techniques. In the additive manufacturing process, a higher roughness of the samples was detected. In terms of sliding angle, variations were observed in the FEP-based coatings and no variations were observed in the ceramic coatings, with a slight increase for FEP in AM. In terms of adhesion to the substrate, the ceramic coatings applied in the additive process showed a superior behavior to that of subtractive manufacturing. On the other hand, FEP coatings showed comparable results for both techniques. In the wear resistance test, ceramic coatings outperformed FEP coatings for both techniques. In summary, additive manufacturing of non-stick coatings on stainless steel showed remarkable advantages in terms of roughness, adhesion and wear resistance compared to the conventional manufacturing approach. These results are of relevance in fields such as medicine, food industry, chemical industry and marine applications.

Investigation of the performance of the structure and energy absorption in sandwich panels of PLA/TPU manufactured by the FFF technique

Sandwich structures are often used in the automotive, marine, aerospace, and many other industrial sectors due to their desirable performance properties, energy absorption, and ability to reduce the weight of parts. Multilayer composite materials also provide various design possibilities, making it simple for producers to fabricate intricate parts. One of the most popular additive manufacturing technologies for producing complicated objects is fused filament fabrication (FFF). In this study, sandwich samples with a dual-core of polylactic acid (PLA) and thermoplastic polyurethane (TPU) were fabricated by FFF technique in three different configurations, including cylindrical, honeycomb, and tetrahedral truss cells. Their properties were determined and investigated through tensile, three-point bending, Izod impact, microhardness tests, and scanning electron microscopy. The results were compared with samples manufactured with monolithic PLA. The results demonstrated that sandwich structures with TPU cores had a high-energy absorption capability. In comparison to monolithic PLA samples, these materials’ ultimate elongation and impact strength were dramatically enhanced. However, TPU cores had lower flexural and tensile strengths than samples with PLA cores. The structure's shape significantly influences both its strength and energy absorption characteristics. Firstly, tetrahedral truss core samples revealed that the samples’ elongation climbed considerably and exceeded three times with the deposition of TPU as the inner core compared to monolithic PLA. Last but not least, in flexural testing, sandwich panels with honeycomb manufactured of PLA/TPU showed the ultimate strain unit to be about 0.08, twice as much as samples made of monolithic PLA. The lowest impact resistance and the amount of energy absorbed before collapsing were demonstrated by monolithic PLA with a honeycomb inner core. Regarding energy absorption, dual sandwich panels with PLA/TPU, including cylindrical and tetrahedral truss cores, showed the best results.

Parametric optimization of 3D printing process hybridized with laser-polished PETG polymer

The potential of Fused Filament Fabrication (FFF) technology to produce very complex geometrics has a profound impact on the physical world. Practitioners in the industry are developing predictive methods for assessing key parameters and responses of engineering materials. Enterprises are trying to solve problems such as Flexural Strength (FS), Average Surface Roughness (Ra), Tensile Strength (TS), sustainability including energy efficacy, and time management problems. This study's objective is divided into two main parts. The First part includes the parametric investigations of Polyethylene Terephthalate Glycol (PETG) polymer to optimize the mechanical properties, Ra, and sustainability, including Print Time (T) and Printer Energy consumption (E) of samples using the FFF technique. In second part, samples were printed at optimized parametric values and further post-processed to enhance the responses such as TS, FS, Ra, and Laser Scan Time (Tl) using CO2 laser polishing treatment. FFF with PETG, a biodegradable material, is commonly used in various fields, despite the traditionally significant surface roughness of FFF products. In pre-processing, by optimizing 3D printed parameters, FS of 69.9 MPa, lowest Ra of 6.8 μm, TS of 45.1 MPa, lowest T of 53 min and E of 0.20 kWh were attained. In post-processing, the Ra decreased by more than 58.38% due to laser polishing (6.8 μm–2.81 μm). The TS increased by 8.89%, from 45.1 MPa to 49.11 MPa. SEM investigation revealed that the gaps in the material lowered the FS by 5.09%, from 69.9 MPa to 66.34 MPa and Tl for 0.22 min. The fracture morphologies were studied as a means of learning more about the reinforcing process in the future. These outcomes prove that laser scanning can improve and alter the surface of an FFF product.

Influence of printing-based factors on the mechanical properties of hexagonal lattice-structured 3D printed novel walnut shell/polylactic acid composite

The incorporation of bio-based natural fillers and lattice structures in thermoplastic polymer has superior advantages such as a reduction in the usage of conventional polymers with improved damping and mechanical properties. The present work focuses on the development of Walnut Shell/PLA (WSP) lattice-structured composite by the Fused Filament Fabrication technique. The flexural strength, compression strength, and thickness error properties of the hexagon lattice-structured WSP composites are optimized by varying Printing-Based Factors (PBFs) which include infill density (60%, 80%, and 100%), nozzle temperature (190°C, 210°C, and 230°C), printing speed (10 mm/sec, 20 mm/sec, and 30 mm/sec), and layer height (0.1 mm, .2 mm, and .3 mm). The flexural and compression test experiments were conducted as per the ASTM D790 and ASTM D695 standards. The process optimization of the measured responses is made by using Taguchi grey relational grade optimization technique. The experimental outcomes such as compressive and flexural strength and minimal dimensional error are converted into the Grey Relational Grade (GRG) for the optimization process. The results show that the Signal-to-Noise ratio (S/N) from the measured GRG clearly shows that, the lower layer height of 0.1 mm, higher nozzle temperature of 230°C, higher infill density of 100%, and average printing speed of 20 mm/sec is an optimal experimental condition for attaining higher strengths and lower errors. From the Analysis of Variance (ANOVA) analysis, the printing temperature, and layer height are the most persuasive PBFs for the mechanical and physical characteristics with respect to the incorporated lattice structure. The optimized experimental conditions develop maximum flexural and compressive strengths of 4.98 MPa and 28.19 MPa, in addition to a lower thickness error of .186 mm obtained for hexagon lattice-structured WSP biopolymeric composites.

A comparison between large-format 3D printing and conventional fused filament fabrication

ABSTRACT This paper reports the results of a comparison study between objects printed with a large-format 3D printing machine and a conventional fused filament fabrication (FFF) printer. A pellet extrusion head was developed and integrated into a cartesian 3D printing platform, obtaining a large-format 3D printing system based on the FFF technique. This integration allows to use polymerised pellets as raw material and printing with a larger stroke through bigger nozzles than conventional FFF nozzles. In addition, this integration enables printing pieces with considerably thicker layers compared with a traditional FFF process. One of the concerns addressed in this study was the mechanical performance of the objects obtained by the large-format 3D printer. Hence, a comparison of the surface’s roughness, maximal tensile stress, tensile modulus, and deformation were made between pieces printed in a large-format 3D printer and a conventional FFF printer. The results reveal that large-format 3D printing has important benefits, such as reducing the time required to print objects, improving the mechanical performance of the printed pieces, and enabling the use of composite materials in additive manufacturing. However, some drawbacks are noticed, e.g. the low resolution and poor surface finish obtained.

Experimental and simulated study of 3D-printed couplings’ suitability for industrial application

This paper explores the possibility of applying reverse engineering to flexible coupling spare parts through additive manufacturing. Although couplings’ simplicity makes them go unnoticed, they connect elements that transmit power between two shafts, thus being an essential component for most of the machinery currently used in the industry. In this study, flexible couplings with different infill density (60% and 80%) were 3D printed by the fused filament fabrication technique. The original and the additive manufactured couplings were modelled to compare their compressive response and energy-absorbing characteristics, and experimental tests were performed to validate finite element analysis. To derive an optimal material distribution within coupling structure, a generative design approach was conducted through nTopology software. With this novel simulation-driven design, it is possible to reduce the weight of the redesigned part up to 15.8% by defining the wall thickness of the internal structure based on the results of finite element simulation, while maintaining its functionality. Moreover, an economic-environmental study was carried out. Results ensure that the 3D printed prototypes are suitable for replacing the original one under its current operating conditions. Additionally, the economic study shows that the redesigned couplings allow companies to save more than €2700 per coupling in relation to CO2 emission payments.

A Review on Uncertainty Cases in Additively Manufactured Polylactic Acid Using Fused Filament Fabrication Technique

Polylactic acid (PLA) is one of the most frequently used materials in Additive Manufacturing (AM) because it is considered as a nontoxic, biodegradable, and biocompatible material. In addition, Fused Filament Fabrication (FFF), or also known as Fused Deposition Modelling (FDM), is a desirable additive manufacturing technique to manufacture PLA because of its relatively low cost and geometrical flexibility. However, the uncertainty existence can lead to unpredicted failure scenarios, which highly can affect the quality and cost. This review focusses on the different works carried out on the identification of the effective parameters in the additively manufactured PLA when using FFF technique in order to provide the reader with an overview about different uncertainty cases for these common material and technique. Here, we seek to reduce the likelihood of failures when using the additively manufactured PLA using FFF technique. Some future ideas are suggested to develop new strategies with the object of improving several objectives such cost, quality, and productivity. In this way, we do not only need to obtain rapid prototyping, but rapid, economic, and sustainable manufacturing strategies are needed to be closer to a sustainable environment.

Bio-inspired design, modeling, and 3D printing of lattice-based scale model scooter decks

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.

A hybrid ANN/PSO optimization of material composition and process parameters for enhancement of mechanical characteristics of 3D-printed sample

PurposeThis paper aims to study the effects of inorganic CaCO3 nanoadditives in the polylactic acid (PLA) matrix and fused filament fabrication (FFF) process parameters on the mechanical characteristics of 3D-printed components.Design/methodology/approachThe PLA filaments containing different levels of CaCO3 nanoparticles have been produced by mix-blending/extrusion process and were used to fabricate tensile and three-point bending test samples in FFF process under various sets of printing speed (PS), layer thickness (LT), filling ratio (FR) and printing pattern (PP) under a Taguchi L27 orthogonal array design. The quantified values of mechanical characteristics of 3D-printed samples in the uniaxial and the three-point bending experiments were modeled and optimized using a hybrid neural network/particle swarm optimization algorithm. The results of this hybrid scheme were used to specify the FFF process parameters and the concentration of nanoadditive in the matrix that result in the maximum mechanical properties of fabricated samples, individually and also in an accumulative response scheme. Diffraction scanning calorimetry (DSC) tests were conducted on a number of samples and the results were used to interpret the variations observed in the response variables of fabricated components against the FFF parameters and concentration of CaCO3 nanoadditives.FindingsThe results of optimization in an accumulative scheme showed that the samples of linear PP, fabricated at high PS, low LT and at 100% FR, while containing 0.64% of CaCO3 nanoadditives in the matrix, would possess the highest mechanical characteristics of 3D-printed PLA components.Originality/valueFFF is a widely accepted additive manufacturing technique in production of different samples, from prototypes to the final products, in various sectors of industry. The incorporation of chopped fibers and nanoparticles has been introduced recently in a few articles to improve the mechanical characteristics of produced components in FFF technique. However, the effectiveness of such practice is strongly dependent on the extrusion parameters and composition of polymer matrix.

Friction stir welding of polypropylene based graphene nanocomposites fabricated with 3-D printing: An investigation on the microstructure and mechanical properties

Polymer nanocomposites find diverse applications in the aerospace, automobile and electronic industries due to good corrosion resistance, high specific strength and excellent processing ability. However, the production of complex and larger parts typically requires welding technology. In this research, fused filament fabrication technique was used to prepare polypropylene nanocomposite reinforced with graphene nanoplates. The polypropylene/graphene nanocomposites were then joined using the friction stir welding. Afterward, different analyses such as thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, tensile testing and hardness testing were applied to examine the effects of the process parameters on the microstructure and mechanical properties of the nanocomposite. The results of thermal analysis indicated that the addition of graphene nanoplates improved the melting point and crystallinity percentage of the polypropylene nanocomposite. Mechanical characterization of the welded samples indicated that the increase of rotational speed from 500 to 750 rpm enhanced the tensile strength of weld joint, while it reduced the hardness. Moreover, an increase in the welding speed from 10 to 30 mm/min resulted in a reduction in the tensile strength and an improvement in the hardness. The highest tensile strength of the weld was obtained by addition of 1 wt% graphene to polypropylene, whereas the hardness of the weld was maximized by addition of 2 wt% graphene. Nevertheless, the desirable combination of the process parameters for simultaneous enhancement of tensile strength and hardness was achieved by rotational speed of 667 rpm, welding speed of 16 mm/min and graphene content of 1.5 wt%.