Purpose This study aims to address the absence of research on the torsional behavior of vat-photopolymerized (VPP) resin polymers, particularly under cyclic and reversed cyclic loading. No systematic investigations have previously examined the cyclic torsional response of VPP-ultraviolet (UV)-LED specimens. The aim is to establish reliable experimental data, evaluate the influence of UV post-curing and propose simplified constitutive models for numerical simulations. Design/methodology/approach Seventy-five Anycubic UV Tough resin specimens were fabricated in a vertical orientation and post-cured for 0, 60, 120, 180 and 240 min. Monotonic, cyclic, and reversed cyclic torsion tests were performed at a constant rate until failure. Torque–revolution data were converted into shear stress–strain curves, from which shear modulus, peak shear stress, energy absorption and torsional rigidity were quantified. Logistic regression was applied to predict parameter evolution, and normalized multilinear models were developed to represent shear stress–strain envelopes for different torsional regimes. Findings Results showed that UV post-curing improved stiffness, strength and energy absorption, with the most significant gains up to 180 min. All specimens failed in a ductile manner, with more than 90% of strain energy absorbed in the plastic range. Compared with monotonic tests, cyclic and reversed cyclic torsion reduced ultimate strain but preserved high ductility. Damage indices confirmed progressive stiffness degradation, while fracture consistently followed 45° shear planes. Originality/value To the best of the authors’ knowledge, this work provides one of the first comprehensive data sets on VPP resin polymers under torsion and introduces empirical relationships and normalized multilinear models suitable for direct integration into numerical simulations.

Purpose Surface roughness inherent to additive manufacturing (AM) is frequently overlooked in the design of components for thermal management and fluid transport, particularly under laminar flow conditions where its effects are often assumed negligible. This study aims to systematically evaluate the impact of different AM roughness scales on flow resistance in such applications. Design/methodology/approach The roughness of side-skin surfaces produced by laser-based powder bed fusion of metals (PBF-LB/M) is decomposed into three components: a base profile with dominant sinusoidal or smoother features from inter-layer meltpool stitching; small-scale roughness caused by partially melted or adhered powder particles; and large-scale random roughness due to process instabilities such as spatter. Laminar flow simulations are performed in circular channels generated from both analytical sinusoidal profiles and profilometry scans of vertically printed AlSi10Mg samples, enabling isolation and quantification of each roughness component’s contribution to flow resistance. Findings Results show that spatter-induced large-scale roughness is the primary contributor to drag, accounting for nearly two-thirds of the total pressure loss in AM channels. Powder–scale roughness is responsible for more than half of the remaining pressure loss, while the base profile contributes the least. These findings provide quantitative insight into the role of each roughness scale in AM-fabricated components. Originality/value This work provides the first systematic decomposition and quantification of multi-scale AM roughness effects on laminar flow resistance, supporting targeted roughness mitigation strategies to enhance the hydraulic performance of AM components.

Purpose This study aims to examine how surface roughness arising from laser powder bed fusion (LPBF) impacts the tensile properties of thin-wall cobalt-chrome (CoCr) components relevant to aviation heat exchangers. It aims to quantify the effects of key LPBF parameters and surface texture metrics on the effective elastic modulus, yield strength, and ultimate tensile strength (UTS). Design/methodology/approach Thin-wall CoCr specimens were additively manufactured via LPBF with varied wall thicknesses (0.889, 1.397, and 1.905 mm), build angles (50°, 60°, and 70°) and laser incidence angles. Surface topography was measured using an optical profilometer, and standard areal roughness parameters were extracted. Tensile testing was performed on as-built and machined samples to assess the influence of surface condition on mechanical response. Analysis of variance (ANOVA) was used to identify the most influential roughness metrics affecting tensile properties. Findings As-built 0.889-mm-thick specimens showed the greatest performance degradation relative to their machined counterparts, with average reductions of 12% in effective elastic modulus, 14% in yield strength, and 15% in UTS. Statistical analysis indicated that Sv, S10z, and Sku were most significant parameters influencing UTS, while Sa, Sq, Sv and S10z most strongly affected the effective elastic modulus. Originality/value The paper provides a quantitative linkage between LPBF process-induced surface texture and tensile performance in thin-wall CoCr components, isolating the most influential areal roughness metrics via ANOVA. These results offer practical guidance for parameter selection and post-processing to improve the mechanical reliability of LPBF-fabricated heat exchanger structures in aerospace applications.

Purpose This study aims to determine the influence of the effect of pulsation in wire laser additive manufacturing (WLAM) on the performance of ER308 stainless steel for applicability in critical industries. Design/methodology/approach ER308 stainless steel walls were fabricated using WLAM in pulsed and un-pulsed. Microstructural analysis was conducted via metallography, while mechanical properties were assessed through hardness, Charpy impact and tensile testing. Fractography was performed to evaluate failure mechanisms. Findings In the un-pulsed mode, samples exhibited a dual-phase microstructure, consisting of austenite with some ferrite. The pulsed mode resulted in a higher fraction of ferrite and finer grains due to rapid solidification and thermal cycling. Pulsed specimens displayed a more uniform hardness distribution, with values ranging from 165 Hv at the bottom to 230 Hv at the top, reflecting fine grain structures. Charpy impact tests showed an approximately 29.2% increase in energy absorption for pulsed specimens. Tensile testing revealed pulsed specimens had a higher ultimate tensile strength (853.47 MPa vs 831.25 MPa) and fracture strain (42% vs 38%). Fractography confirmed ductile failure in pulsed specimens and brittle fracture in un-pulsed specimens. Research limitations/implications This study is limited to ER308 stainless steel and specific WLAM parameters. Future work should explore other materials and process variations. Practical implications Pulsed WLAM improves mechanical performance and uniformity, making it suitable for aerospace, energy and automotive applications. Originality/value A direct comparison of pulsed and un-pulsed WLAM of stainless steel.

Purpose The aim of this study is to improve printability by studying the effects of ink’s viscosity, pattern width and length and the process parameters of direct ink write (DIW) technique on the printed carbon patterns for applications in functional sensors and devices. The primary focus is to understand the effects of all the possible parameters, including rheological and geometrical characteristics associated with direct ink writing of conductive carbon and their effects on the performance of the printed pattern, followed by their optimization for desired applications. Moreover, the research work seeks to draw a relationship accounting for the influencing parameters to improve printability and performance. Design/methodology/approach The research performed a comprehensive analysis of ink’s rheological characteristics, geometrical attributes and process parameters on the performance of DIW printed carbon. The rheological characteristics involve the viscosity and shear thinning effects on the process parameters and their fine-tuning. Moreover, the viscosity reduction was carried out to study the effects on printing parameters. Response surface modeling technique was adopted to statistically determine the significant parameters and their effects on the printed patterns. Furthermore, a lab-developed setup was used to realize samples, followed by a detailed study of the effects of each parameter on the pattern width and resistance. The experiments were performed for both pristine and reduced viscosity carbon paste, and the results were compared. Furthermore, the length of the pattern was varied, and the effects were recorded to conclude the study. Findings The research findings concluded establishing a relationship between the ink’s rheological characteristics, geometrical attributes and process parameters of the DIW technique to improve printability and electrical performance of printed functional devices of carbon ink. The statistical analysis carried through highlights extrusion pressure and print speed as the most significant process parameters for a given viscosity, and their optimization is dependent on the required output performance. The viscosity reduction significantly reduced the required extrusion pressure and enhanced print speed without altering the electrical characteristics. It was found experimentally that pattern width is influenced by printing parameters, which are associated with electrical characteristics. Furthermore, the results showed that the printed patterns obey Ohm’s law in terms of increased length at a fixed increment. Originality/value The study provides the very first comprehensive and systematic analysis of the critical impacts of rheological characteristics, geometrical attributes and process parameters of DIW of conductive carbon for applications in functional sensors and devices. The combination of statistical and experimental aspects of the study establishes a definitive, optimized printing window, moving ahead of qualitative aspects, thus providing a quantitative framework for the fabrication of stable, high-performance carbon-based devices via DIW. The printing window will ensure reproducibility and enhancement in the performance of carbon-based sensors fabricated through DIW, thus enabling robustness and cost-effectiveness.

Purpose Commercial bioprinting systems are typically characterized by high costs and limited adaptability, presenting a significant barrier for academic research. This study aims to introduce and empirically validate an integral prototyping methodology for developing a low-cost, accessible robotic bioprinters. The primary objective is to provide a holistic framework that integrates mechanical design, electronics and control systems, aimed at addressing key engineering challenges. This work also addresses the critical issue of maintaining high positional accuracy in a system with a variable payload mass. Design/methodology/approach Following the Integral Prototyping framework, a multi-link robotic manipulator bioprinter was developed through an iterative process that integrated mechanical, electronic and control subsystems. A direct-drive extruder was implemented to minimize material waste by embedding cartridges into the end-effector, a design choice that created the central challenge of a variable payload. This study develops a payload-agnostic visual servoing controller. The system’s adaptability and the controller’s performance were validated by testing with five biomaterials and two 50:50 composites with diverse viscosities (gelatin-based hydrogel, lipid-rich emulsion, ground pork, starch-based hydrogel and composites), confirming the framework’s control strategy and the overall adaptability to heterogeneous biomaterials. Findings Application of the Integral Prototyping methodology resulted in a robotic bioprinter capable of sustaining high positional accuracy despite variable payloads. The visual servoing controller improved the system’s precision, reducing average positional deviations for key joint angles (e.g. from 13.18% to 6.62% for q1 and from 6.74% to 4.08% for q2), demonstrating effective compensation for mass variability introduced by the direct-drive extruder. The control system interfaces with standardized G-code to ensure both accuracy and accessibility. This control robustness translated into accurate fabrication outcomes, with dimensional deviations below 2.0% and scaffold fidelity deviations between 2.0% and 3.3%. Scaffold integrity was partially constrained given the configuration of the extrusion module. Results confirm that the control system successfully decouples positional precision from payload variability. These outcomes validate Integral Prototyping as a framework that not only integrates design, electronics and software but also resolves emergent engineering challenges central to accessible bioprinting. Originality/value The primary contribution is a reproducible Integral Prototyping methodology for developing low-cost, adaptable robotic manufacturing bioprinting platform that remain robust under variable operating condition. This work contributes in uniting design, electronics and control into a single framework while providing a validated visual servoing solution to the long-standing robotics challenge of variable end-effector mass. Beyond the specific controller, this study establishes a generalizable blueprint for rapid prototyping and tissue engineering, demonstrating that cost and flexibility barriers in bioprinting can be addressed through integrative, methodology-driven development.

Purpose In the field of 4D printing, shape memory polymers are gaining more and more interest, thanks to their large deformability and ease of manufacturing, compared to their metallic alloy counterparts. However, they are still rarely adopted for industrial applications, often limited by the poor time and space accuracy of their recovery behaviour. In this paper, the aim is to use an electroconductive shape memory polymer to design a hinge for the self-deployment of space structures. Design/methodology/approach Fused filament fabrication and composite material made of bio-sourced polylactic acid filled with carbon black particles are used. First, the hinge is conceived as the answer to an inverse design problem: its geometry integrates an electrical circuit and the influence of the printing parameters is considered to perform the shape memory behaviour. The deployment of the hinge is filmed and tracked thanks to a multi-instrumented setup to calculate its recovery ratio and kinetics and evaluate its performance. One to ten deployments are considered to study their behaviour under repeated use. Furthermore, the force deployed is measured and compared between the first and the tenth cycles to evaluate its durability. Findings Results show that the hinge is able to recover up to 80% of its initial shape and deploy the same force through the cycles. Originality/value This paper highlights the ability of training the shape memory effect to obtain targeted results and the capacity of the device to maintain the force deployed throughout the cycles. A novel multi-instrumented setup is presented to measure four different properties (electrical, thermal, mechanical and force).

Purpose The primary purpose of this study is to develop an eco-sustainable and high-performance three-dimensional (3D)-printed polymer composite by reinforcing polyethylene terephthalate glycol (PETG) with short bamboo fibre (SBF) and nano-scale coconut shell ash (CSA-n). The study aims to enhance the mechanical, structural and interfacial characteristics of PETG through a hybrid reinforcement strategy that uses renewable natural fibres and waste-derived nano-fillers. By integrating SBF for strength and nano-scale CSA for improved interfacial bonding and thermal stability, the work seeks to address the limitations of conventional PETG composites, such as poor stiffness and limited fibre–matrix adhesion. The overall objective is to contribute towards the advancement of sustainable materials in additive manufacturing, enabling environmentally friendly and structurally efficient bio-composites suitable for engineering and structural applications. Design/methodology/approach The hybrid PETG composites were fabricated using the fused filament fabrication process. The methodology began with the preparation of SBF through cleaning, alkali treatment, and silane coupling to improve surface roughness and adhesion with the polymer matrix. CSA was converted into nano-scale particles via controlled carbonization, calcination, high-energy ball milling and ultrasonic dispersion to achieve fine particle size and uniform morphology. Composite formulations were prepared at a fixed 70:30 volume ratio of PETG to reinforcement (SBF + CSA-n), and filaments were produced through twin-screw extrusion. Standardized specimens were 3D printed using optimized process parameters and tested for tensile, flexural, impact and hardness properties according to ASTM standards. Scanning electron microscopy was used to analyse fibre–matrix interaction, filler dispersion and fracture characteristics, supported by quantitative image analysis to assess void content and alignment. Findings The experimental results demonstrated that the incorporation of nano-scale CSA substantially enhanced the interfacial bonding, mechanical strength and filler dispersion of PETG-based composites. Among all the developed specimens, the hybrid composite containing SBFs and nano-CSA (Specimen D) exhibited superior performance, with tensile strength of 54.1 MPa, flexural strength of 74.8 MPa, impact toughness of 5.6 kJ/m², and hardness of 101 HRM. SEM analysis revealed dense fibre distribution, minimal void formation and strong interfacial adhesion in the nano-CSA-reinforced composites, confirming efficient stress transfer and structural integrity. In contrast, fibre-only composites showed poor adhesion and higher porosity, while micro-CSA-filled composites presented moderate improvements but exhibited uneven filler dispersion. Overall, the findings confirm that the synergistic interaction of SBFs and nano-scale CSA leads to significant gains in stiffness, strength and toughness without compromising printability or weight efficiency. Originality/value To the best of the authors’ knowledge, this study is the first to report the development of a 3D-printed hybrid PETG composite reinforced simultaneously with SBF and nano-scale CSA . The novelty lies in demonstrating the synergistic effect of natural fibre and nano-filler reinforcement in enhancing interfacial bonding, load transfer and overall composite performance. Unlike previous single-reinforcement PETG composites, this hybrid system introduces a dual mechanism that significantly improves both mechanical and thermal stability, contributing to the design of next-generation bio-based engineering materials. The research holds substantial value for advancing sustainable additive manufacturing practices by using renewable bamboo fibres and waste-derived nano-fillers, thereby supporting circular economy initiatives and offering a scalable pathway towards environmentally responsible, high-performance composite materials.

Purpose The inherent strain method for laser powder bed fusion additive manufacturing (AM) allows for rapidly simulating process-induced distortion while still retaining the influence of thermomechanical physics. However, previous implementation of a single vector taken from a global average does not fully capture the known AM process results. This study aims to increase predicted accuracy in simulations by modifying the inherent strain method to better reflect experimentally defined print behavior. Design/methodology/approach This study analyzed the thermomechanical response of a small-scale AM part and applied the findings to a part-scale simulation, validated against experimental measurements of a benchmark geometry. This included the effects of the compressive core and the rapidly cooled tensile shell of an AM part and the differing in-plane and build-direction environments, captured with two strain vectors in the inherent strain method. Findings When compared to experimental X-ray diffraction strain measurements in the in-plane and build directions, simulation accuracy was improved from the traditional single-vector approach, reaching errors as low as 1% and lowering part median error from 82% to 17%. Originality/value This vector assignment approach better captures the process physics to improve AM simulation accuracy without sacrificing the lightweight computational cost advantage of inherent strain modeling. Part residual strain distribution was characterized, leading to a better understanding of post-print effects in AM parts.

Purpose The purpose of this study is to investigate the production and performance of zinc borate–reinforced epoxy composites produced via additive manufacturing. This study aims to evaluate the effects of different zinc borate reinforcement ratios on the mechanical, thermal and fire retardancy properties of the composites. By analyzing the results, this study seeks to provide a deeper understanding of the potential of zinc borate as an eco-friendly flame retardant in advanced polymer composite applications. Design/methodology/approach Epoxy composites were reinforced with zinc borate at weight fractions of 0.5%, 1%, 2% and 3% using the stereolithography additive manufacturing method. The mechanical properties were characterized through tensile, three-point bending and dynamic mechanical analysis. Thermal properties were assessed using thermogravimetric analysis, and flame retardancy was evaluated with specific fire retardancy tests. Microstructural and chemical properties were examined via scanning electron microscopy, X-ray diffraction and Fourier-transform infrared spectroscopy analyses. In addition, hardness and thermal conductivity tests were performed to provide a comprehensive evaluation of the composites. Findings The incorporation of zinc borate significantly improved the thermal stability and mechanical properties of epoxy composites. Zinc borate acted as an effective flame retardant due to its hydrate groups, which enhanced thermal stability. However, the flame retardancy performance was found to be insufficient at lower reinforcement rates. This study highlights the potential of zinc borate as a multifunctional additive for enhancing the durability and performance of epoxy composites while emphasizing the need for further optimization to achieve superior flame retardancy. Originality/value This study represents an innovative approach by combining eco-friendly zinc borate reinforcement with advanced additive manufacturing techniques to produce high-performance polymer composites. It provides valuable insights into the interplay between reinforcement ratios and composite properties, offering a pathway for the optimization of zinc borate–reinforced materials. The findings contribute to the growing field of sustainable material development and establish a foundation for future studies in flame-retardant polymer composites.