Publisher Correction: In-situ temperature control in large-scale additive material extrusion: linking microstructure to mechanical performance

Additive manufacturing (AM) processes, such as material extrusion, are part of a popular growing technology field; with limited human assistance required and advanced rapid prototyping capabilities, this technology is advertised to have limitless possibilities. The common challenge faced by users is a lack of design control of the surface roughness, which is highlighted by a characteristic “stair case” layering effect at the boundary. Focusing on material extrusion processes, the goal of this research is to model representative bead shapes, and highlight the surface roughness challenges for assessing boundary-fill regions. Various bead shapes are explored and compared through virtual simulation. Unique material extrusion AM-related issues arise, and it is shown that machining solutions may not provide the desired surface smoothness. This research illustrates that specific physical and virtual assessment tools and standards need to be further developed to convey surface roughness attributes for material extrusion additive manufactured components.

The conducted study was focused on the development of a new type of polymer blends intended for additive manufacturing applications, in particular, the material extrusion method (MEX). The developed materials were prepared from recycled poly(ethylene terephthalate) and amorphous copolymers poly(ethylene terephthalate-glycol) (PETG), and poly(cyclohexylenedimethyl terephthalate-glycol) (PCTG). The basic blend systems were additionally modified with POE-g-GMA impact modifier (IM) during the reactive extrusion process. The main aim of the work was to assess the effectiveness of using composite additives and their influence on the mechanical and thermomechanical parameters of the tested systems. To prepare the composites, selected polymer blends were modified with 10% of talc (T) and carbon fibers (CF). The properties evaluation includes the mechanical/thermomechanical testing, thermal analysis and structural observations. The accuracy of printing was measured using optical scanning methods. The test results indicate that even the relatively small amount of the CF filler could lead to a significant increase in tensile modulus from reference 1.6 GPa to 2.9 GPa; the same improvement applies to strength values, where the CF-modified materials reached 45 MPa, compared to the reference 31 MPa. The heat deflection tests (0.455 MPa) after annealing revealed the maximum HDT of around 170 °C for both types of CF-modified materials. The Vicat test results were also favorable for annealed materials. Considering that the Vicat/HDT results after the 3D-printing process usually reach around 70 °C, the performed heat treatment strongly enhanced the heat resistance for most of the prepared blends. The performed studies revealed that for most of the prepared materials, the brittleness was a common drawback for both MEX-printed and injection-molded materials.

Improving mechanical performance in material extrusion parts via optimized toolpath planning

Additively manufactured polymeric composites exhibit customised properties beyond those offered by conventionally fabricated ones. However, in many cases, the mechanical performance mainly depends on the processing parameters, tools, and material selection. Yet, one of the issues of the additive manufacturing process especially in the material extrusion process is the inability to control the printing layups, thereby causing interlaminar damage. Thus far, literature and research have focused on improving the mechanical performance of such polymeric composites by focusing on the interlaminar shear strength under a transverse load transfer. Polymeric composites prepared using the material extrusion technique namely fused deposition modelling (FDM) are discussed upon its layup sequence and orientation. This article proposes that by realising a homogenous distribution of the transverse load, the orientation and the printing direction can maximise the printed load bearing. Moreover, the layup sequence and the interlayer diffusion are key for controlling the mechanical properties of the polymeric composites. This brief review presents a comprehensive elucidation of the polymeric composites manufactured using FDM that interprets the needs of having greater load bearing in each layup printing sequence of the polymeric composites. By able to control the layup sequence, one can control the mechanical performance based on specific functionality.

Polyethylene terephthalate glycol (PETG) and silicon nitride (Si3N4) were combined to create five composite materials with Si3N4 loadings ranging from 2.0 wt.% to 10.0 wt.%. The goal was to improve the mechanical properties of PETG in material extrusion (MEX) additive manufacturing (AM) and assess the effectiveness of Si3N4 as a reinforcing agent for this particular polymer. The process began with the production of filaments, which were subsequently fed into a 3D printer to create various specimens. The specimens were manufactured according to international standards to ensure their suitability for various tests. The thermal, rheological, mechanical, electrical, and morphological properties of the prepared samples were evaluated. The mechanical performance investigations performed included tensile, flexural, Charpy impact, and microhardness tests. Scanning electron microscopy and energy-dispersive X-ray spectroscopy mapping were performed to investigate the structures and morphologies of the samples, respectively. Among all the composites tested, the PETG/6.0 wt.% Si3N4 showed the greatest improvement in mechanical properties (with a 24.5% increase in tensile strength compared to unfilled PETG polymer), indicating its potential for use in MEX 3D printing when enhanced mechanical performance is required from the PETG polymer.

Digital manufacturing techniques, such as computer numerically controlled (CNC) machining and additive manufacturing (AM), have greatly increased the design space available to engineers with respect to both geometry and materials. Obviously, certain geometries cannot be realized by anything other than a layer-by-layer AM process, and certain materials can only be formed using traditional subtractive approaches, leaving designers with little choice. However, for the wide array of structures that could be realized in a variety of different ways, the choice of manufacturing process is just another faction in the overall design process. Planar lattice structures have complex repeating geometric features which are best designed using computer aided design (CAD) tools, and these structures can easily be manufactured using a variety of different digital manufacturing processes. For this study a set of planar lattice structures were designed and fabricated from acrylonitrile butadiene styrene (ABS) plastic using both a CNC milling machine and a material extrusion AM machine. All test lattices were then loaded in tension to failure to determine their mechanical performance. The determined properties were then compared to analytical predictions from the literature, and an analysis of the impact of a chosen manufacturing process was performed. The results obtained show good agreement with publish models for lattice performance, and additionally suggest that the choice of manufacturing process has a measurable effect on the mechanical performance of the resulting structures for this specific material and geometry combination, but it is important to note that this study is just an example of how to mitigate the uncertainties associated with the freedoms offered by advanced manufacturing processes, and more work in needed in this important area of study.

Material Extrusion (MEX) additive manufacturing offers a versatile platform for producing lightweight, structurally optimized components. This study investigates the simultaneous optimization of topology and infill density using three polymer composite materials, PPA-CF, PAHT-CF, and ABS, selected for their mechanical performance, cost efficiency, and printability. Cylindrical specimens were fabricated with nine mass retention levels (100% to 33%) by systematically varying topology and infill parameters. Compression testing was conducted to assess stiffness, deformation behavior, and structural integrity under simulated operational loads. Results show that combining topology optimization with variable infill density can significantly reduce material usage and manufacturing time while maintaining mechanical reliability across all three materials. PAHT-CF demonstrated the highest strength-to-weight performance, while ABS offered cost-effective alternatives for less demanding applications. The study establishes clear relationships between design strategies and material behavior, enabling the production of net-shape satellite support structures with fewer design iterations and improved throughput. These findings support the adoption of resource-efficient manufacturing practices and provide a framework for sustainable, low- to mid-volume production in high-value manufacturing industries. Overall, the integration of design and material optimization advances the potential of additive manufacturing for scalable, cost-effective, and environmentally conscious aerospace solutions.

Material Extrusion (ME) is a layer-by-layer additive manufacturing technique that has gained prominence due to its simplicity, cost-effectiveness, design freedom, and adaptability to a wide range of thermoplastic materials. However, the mechanical performance of ME-printed parts often remains suboptimal, primarily due to complex thermal phenomena that govern microstructural development during the printing process, which are key determinants of mechanical strength. As a result, optimizing thermodynamic printing parameters has become essential for improving the overall quality of the printed parts. Extensive research articles and reviews have been published to explore the effect of many ME printing parameter settings on the resultant product characteristics. Despite this focus, the effect of cooling rate, a critical thermodynamic parameter of the process, has been largely overlooked in current research when they are critically reviewed. Cooling rate plays a central role in determining the thermal history of printed material, which in turn influences polymer chain mobility and microstructural features of the extruded material, all of which are crucial to the mechanical integrity of the printed part. Thus, it has been concluded by this review that analytical and empirical investigations into the influence of cooling rate on the microstructural properties of ME parts represent a valuable and novel contribution to the academic field.

Additive manufacturing of Diels-Alder self-healing polymers: Separate heating system to enhance mechanical, healing properties and assembly-free smart structures

The present study permeates the frontier of additive manufacturing (AM) by extruding composite materials with continuous reinforcement (Continuous fibers reinforced polymer - CFRP). The growing demand for the development of composites with greater capacity for mechanical resistance due to relative density that meet the needs of projects in the aeronautical and automobile industries, for example, has fostered research around the world on this technology. The current world scenario of technology still has a small number of startups and companies, thus resulting in the opportunity to study and apply it in Brazil. The current stage of CFRP AM by extrusion of material in desktop printers with Cartesian axis presents a fiber volumetric fraction (Vf) of 30%, non-homogeneous reinforcement distribution and the presence of voids. This research aimed to develop and characterize a composite filament of thermoplastic PLA matrix and hybrid reinforcement of short carbon fibers and continuous Kevlar29. With the purpose of application in AM by material extrusion, PLA, short carbon fibers, Kevlar29 and the composites produced were characterized by FTIR-ATR, TGA, DSC, mechanical tensile test, XRD, SEM and µCT. The TGA and DSC results indicated the ideal drying temperature for Kevlar29, where the present humidity triggered porosity. SEM and µCT demonstrated the level of impregnation obtained in the manufacture of the composite, which, due to the absence of internal pressure control in the coating chamber, was limited to the external continuous fibers. FTIR-ATR, TGA, DSC, and XRD indicated that the crystalline structure of the matrix and reinforcement were not altered, indicating the non-formation of adhesion between the phases of the composite. Mechanical tensile performance demonstrated premature failure of the matrix to separate from the reinforcement. Improvement processes were identified, such as pre-drying the continuous reinforcement and adjusting the sealing of the coating chamber nozzles. The studies pointed out that the result of the manufacture of the composite is in the TRL4 stage of technological development, which means testing the product in the laboratory.

This study demonstrates the multifunctional performance of innovative 2D auxetic lattices through a combination of multiscale experiments, finite element modeling and data-driven prediction. A geometric modeling approach utilizing Voronoi partitioning and a unique branch-stem-branch (BSB) structure, patterned according to 2D wallpaper symmetries, enables precise concurrent geometric and topological tuning of lattices across a continuous parameter space. Selected architectures are physically realized via material extrusion of polylactic acid (PLA) infused with carbon black (CB). Experimental characterizations, supported by Finite Element modeling, reveal the significant influence of BSB structure's design parameters on mechanical and piezoresistive performance under tensile loading, with a remarkable Poisson’s ratio of -0.74, accompanied by a 15-fold increase in elastic stiffness and a 34-fold increase in strain sensitivity. Additionally, architecturally, and topologically tailored lattice structures exhibit tunable damage sensitivity, reflecting the rate of conductive network destruction within the lattice. This offers insights into the rapidity of cell wall failure, with a steeper slope of the piezoresistance curve in the inelastic regime indicating a faster breakdown and quicker onset of mechanical failure. Integration of Gaussian Process Regression enables accurate exploration of the design space beyond realized structures, highlighting the potential of these intelligent lattice structures for applications such as sensors and in situ health monitoring, marking a significant advancement in multifunctional materials.

Purpose Fibre-reinforced polymers offer enhanced in-plane mechanical properties in material extrusion (MEX) additive manufacturing, expanding its applicability. However, fibres have minimal impact on the mechanical properties in the build direction, limiting the industrial applications of MEX. This study aims to propose a novel method using a customised toolpath to enhance the interlayer mechanical properties of carbon fibre-reinforced nylon 6 (CF-PA6) structures in an easily accessible manner, requiring no hardware modifications. Design/methodology/approach The customised toolpath discretises the continuous bead into sub-sections and implements periodic vertical toolhead movement during fabrication. Three bead width configurations of MEX-fabricated CF-PA6 specimens were investigated using microscopy, thermal analysis and mechanical performance assessment. Findings In all configurations, the customised toolpath outperformed the conventional toolpath, showing significant increases in ultimate tensile strength (238%–513%), failure strain (70%–349%) and modulus (71%–164%). The main factors contributing to these improvements were found to be redistribution of fibre orientation and thermal effects. In addition, the enhancements became more pronounced as the print width increased. Originality/value This novel fabrication method improves the interlayer mechanical properties of CF-PA6 through software modifications alone. To the best of the authors’ knowledge, this approach has not been demonstrated on fibre-reinforced materials and may enable printing of high-performance polymers on less capable MEX printers.

Bond strength measurement for additively manufactured Inconel 718- GRCop84 copper alloy bimetallic joints

Accurate and reliable results in orthodontics heavily depend on selecting the right impression materials. With the rise of digital technology and additive manufacturing techniques, it has become necessary to characterize experimentally the materials used to design prosthetic bases. In this study, the mechanical properties of Polyetheretherketone, Nylon6, Nylon12, and Polypropylene are analyzed, as impression materials commonly used in dentistry applications. Specifically, the effect on their flexural elastic modulus of the exposure to working environment conditions is also investigated by means of 3-point bending test performed on virgin materials and samples immersed in saliva for 72 hours. The proposed approach revealed significant behavior in terms of loss in mechanical performances. These findings have significant implications for the proper selection and use of AM materials in dental applications.

A hip implant is surgically placed to replace damaged components and restore the patient’s mobility. Although hip implants are widely used, there is a need to improve their mechanical performance while minimizing weight. Traditional designs often compromise between strength and weight, which can lead to implant failure. This research presents the optimization of hip implant design to minimize weight while maintaining bio-mechanical strength under physiological loading conditions. The primary objective of this study is to investigate the mechanical behavior of hip implants using three different lattice structures for designing the lightweight hip implant. The results show that at 50% of the lattice level, the cubic lattice has the highest deformation of 0.13 mm, the triangle lattice has a similar deformation of 0.13 mm, while the hexagonal lattice has a lower deformation of 0.12 mm. The maximum equivalent stress of the cubic lattice is 363.7 MPa, and the triangle lattice is 364.82 MPa. Meanwhile, the hexagonal lattice has a lower value, at 280.97 MPa. All three lattice structures with 10%, 30%, and 50% lattice have different structural integrity, where the hexagonal lattice implant has the maximum level of stress distribution and structural integrity, particularly at higher lattice levels. Additionally, the cubic lattice minimizes 15.49% of mass, the triangular lattice minimizes 15.72% of mass, and the hexagonal lattice minimizes 15.84% of mass, which makes the hexagonal lattice ideal for hip implants to achieve optimal mechanical performance and lightweight structure. In conclusion, the combination of finite element analysis and additive manufacturing can enhance the orthopaedic implant design, especially for hip implants.