This study systematically evaluates the physical, mechanical and thermal performance of glycerol triglycidyl ether-based bio-epoxy resins to assess their suitability as sustainable alternatives for high-performance composite applications. A Taguchi (L12)-Gray relational analysis optimized the bio-epoxy formulation for high-performance composites. The optimal formulation was identified as glycerol-based bio-epoxy resin with low viscosity (BE1) combined with 5-methyl-5-norbornene-2,3- dicarboxylic anhydride (MNA) hardener at stoichiometric ratio and 1.5 wt.% catalyst. ANOVA results showed that resin type, MNA, and initiator contents contributed 18.2%, 31.8% and 4.5% to overall performance, respectively. The optimized bio-epoxy resin formulation exhibited a saturated water absorption of 2.06% and crosslink density of 0.002 mol/cm3. Tensile, compressive and flexural strengths of 60, 106 and 100 MPa, respectively were achieved, with corresponding moduli of 3.38, 2.71 and 3.25 GPa, respectively. The glass transition temperature was 136oC, linear thermal expansion coefficient was 105 μm/m.oC and thermal decomposition temperature was 306oC. When manufacturing process demanding high-viscosity resin system, the optimized formulation consisted of a high viscous glycerol-based bio epoxy resin (BE5) cured with MNA hardener at stoichiometric ratio and 1.5 wt.% catalyst. The optimized bio-epoxy provides a sustainable alternative to petroleum-based resins, supported by a scalable optimization framework for high-performance composite manufacturing.
The aerospace sector is increasingly prioritizing component repair over replacement as a sustainability strategy, driving demand for additive manufacturing solutions capable of restoring complex metallic geometries. Wire Arc Additive Manufacturing (WAAM) via GMAW offers high deposition rates and strong metallurgical bonding, yet its application to thin-walled structures and crack-susceptible alloys remains largely unresolved. This study presents a novel GMAW-WAAM repair methodology for an AA2219 aluminum-copper orthogrid aerospace component, characterized by thin walls (2-4 mm), a thin substrate (3mm), and structurally critical wall intersections. AA2219/2319 presents an exceptional challenge for WAAM due to its high susceptibility to hot cracking and hydrogen porosity. By leveraging CMT Cycle step technology combined with a controlled, intermittent dot-by-dot deposition strategy with optimized pauses between dots, this approach mitigated issues inherent to thin geometries, such as heat accumulation, collapse, and burn-through. For wall intersection repair, overlapping curved deposition paths proved the most effective strategy by avoiding arc start/stop points within critical zones. Microstructural characterization of the deposited material revealed no hot cracking, no significant porosity, or major defects, confirming the sound metallurgical integrity of the repair despite the challenging thermal conditions imposed by the thin-walled geometry and the crack-susceptible nature of AA2XXX alloys. These findings validate GMAW-WAAM as a viable repair route for thin-walled aluminum aerospace components and establish process guidelines applicable to similarly constrained geometries.
Abrasive waterjet machining (AWJM) has emerged as a versatile and efficient method for machining intricate shapes in challenging materials, particularly layered fiber composites. This review critically examines recent advances, machining characteristics, and persistent challenges associated with AWJM of composite materials. The review covers the fundamental principles of AWJM and its application to metal matrix composites (MMCs), polymer matrix composites (PMCs), and ceramic matrix composites (CMCs), with particular emphasis on the influence of process parameters on material removal, surface quality, and machining-induced damage. The reviewed studies indicate that AWJM can effectively minimize thermal damage, cutting forces, and conventional tool-related defects; however, its machining performance is strongly dependent on composite architecture and process conditions. In particular, the effects of water pressure, traverse speed, abrasive flow rate, and stand-off distance on delamination and surface quality are not universally consistent, with reported discrepancies associated with differences in composite type, laminate thickness, fiber orientation, manufacturing method, and machining configuration. Recent developments in nozzle technology, micro-AWJM, modelling, and process optimization have improved machining capability, although challenges remain in achieving consistent surface integrity, dimensional accuracy, and reliable process control. These findings highlight the need for material-specific parameter optimization, advanced monitoring, and intelligent process control to enable the broader industrial adoption of AWJM for layered fiber composites.
In an effort to keep up with the rapidly growing needs of society, manufacturing processes and materials need to be constantly developed. Additive manufacturing (AM) exploits different materials and enables reinforcing them with additives. Acrylonitrile styrene acrylate (ASA) is a thermoplastic with high UV and weather conditions resistance. Herein, it was reinforced with ceramic titanium carbide (TiC) nanoparticles. Nanocomposites were developed and evaluated utilizing material extrusion (MEX) AM. TiC loadings ranged between 0 and 12 wt%. Standard specimens for testing were produced with these loadings. The effect of filler content on mechanical, dynamic mechanical, thermal, rheological, and microstructural properties of the 3D printed coupons was studied. The maximum tensile properties were achieved by the 8 wt% nanocomposite (13.9% tensile strength and 20.0% Young's modulus improvement). Overall, considering also the filler cost, the 6 wt% should be considered the optimum loading in the nanocomposites. Higher loadings resulted in higher porosity, increased microhardness (24.3% increase with 12 wt% TiC content), and better dimensional accuracy, making nanocomposites suitable for wear-related applications. The impact strength decreased, suggesting that the nanocomposites are not effective for such applications. Overall, this work establishes ASA/TiC as a promising nanocomposite system for outdoor applications and provides design guidelines for optimizing filler content for robust MEX components manufacturing.
This work aims to evaluate the feasibility of an integrated additive manufacturing-incremental forming (IAMIF) technique to fabricate AA6061-T6/PLA composite laminates. The process integrates fused deposition modeling (FDM) as an additive mean and single-point incremental forming (SPIF) process as a forming mean to fabricate functional 3D models of metal/polymer composite laminate. The study investigates the effect of three process parameters—step down (0.3 mm, 0.6 mm), wall angle (20°, 30°, 40°), and PLA layer thickness (0.4 mm, 0.8 mm)—on the average wall spring-back (AWSB), thinning ratio (ψp) of AA6061-T6/PLA composite laminates and hardness of PLA and AA6061sheets as well as Interfacial Adhesion (Gc). The results show that as the step-down increases, the AWSB, the ψp and the hardness of PLA sheets also increase in contrast to AA6061sheets as well as Gc. Further, an increase in wall angle led to an increase in ψp, AWSB, AA6061sheets and Gc but had no effect on PLA hardness. Moreover, the PLA layer thickness interaction with step down positively influenced Gc, with slight improvement in Gc as it increases at 0.3 mm step down in contrast to 0.6 mm step down. The results proved the feasibility of IAMIF process more deeply, through successful manufacturing a scaled blade of agricultural drone propeller as proof-of-concept. The proposed IAMIF approach presented herein offers a sustainable mass customization approach that benefit many industries that utilize composite laminates for manufacturing components of various sizes, including, but not limited to the automobile, renewable energy industry and the scientific industry.
In this study coaxial composite all-aluminium wire (CAAW), made of electromagnetically cast Al–0.5Fe (core) and Al–1.7Fe (sleeve) alloys, was produced by cold drawing and subjected to annealing at 230 °C for 1h. Core alloy area fraction in CAAW was 0, 10%, 30%, 50% and 100%, which corresponds to 0, 0.32, 0.55, 0.70 and 1 of the boundary between constituents as a fraction of the outer wire diameter, respectively. Rule of mixtures was implemented to calculate the CAAW's expected levels of electrical conductivity, ultimate tensile strength and elongation to failure. Experimental data was compared to the IEC 62641-2023 standard for conductive aluminium wires. It was demonstrated that produced CAAWs mostly meet the requirements of the commercial standard. Rule of mixtures predictions have highest deviation from the experimental data in the 0.3-0.5 core alloy fraction range, meaning that these properties are boundary-driven. CAAWs exhibit the decrease in ductility and increase in ultimate tensile strength during annealing due to the presence of Al-1,7Fe alloy, which was as well reported in previous studies. For these properties' changes the CAAWs could be considered thermally resistant. Visual representation of the experimental data combined with rule of mixtures predictions allow to prognose the CAAW with certain composition that will meet the targeted level of properties.
In this study, the mechanical behavior of high-density polyethylene (HDPE) reinforced with short natural fibers was evaluated using a dedicated test bench designed to investigate the high-cycle bending fatigue of gear teeth. Single-tooth bending tests were performed under displacement-controlled loading, employing high-resolution imaging to monitor crack initiation and propagation relative to the number of cycles. Quasi-static tests revealed a significant increase in structural tooth stiffness with increasing fiber content, accompanied by a reduction in maximum displacement. Fatigue performance was analyzed using S–N (stress–life) curves, damage indices, and linearized Weibull distributions. The results show that fiber reinforcement significantly increases structural tooth stiffness and reduces deformation; consequently, these composites sustain higher relative displacement levels than unreinforced HDPE. However, Weibull analysis indicates that this stiffness enhancement does not systematically translate into improved fatigue life. Crack propagation and residual load evolution exhibit consistent trends, reflecting progressive material damage. This work highlights a trade-off between stiffness and fatigue resistance in short natural fiber-reinforced HDPE gears, offering critical insights for design under cyclic loading conditions.
Lightweight Magnesium (Mg) microgears present a compelling market opportunity motivated by the emerging trend towards miniaturization in the biomedical, robotic, and aerospace sectors. Microforming is a low-cost micromanufacturing solution that can enable the fabrication of complex microgears with high repeatability and precision. The microformability of Mg alloys is limited by the complex HCP crystal structure and grain size effect at room temperature. These forming related limitations of Mg alloys can be surpassed by the hot microforming route. In this domain of Mg hot microforming few research groups are working and there is no study on Mg microgear manufacturing to date. The present work is focused on addressing this issue by using a novel hot microforming strategy integrated with microstructural engineering to manufacture high-quality Mg microgears. To facilitate this, a custom-designed hot microforming tool was developed with a microgear die module. An Mg-RE alloy with high thermal stability was selected and two grain-size extremities, namely coarse-grained (CG) and ultrafine-grained (UFG), were synthesized using thermomechanical processing. A processing map was used for both CG and UFG materials in order to identify the favorable microgear manufacturing conditions and the three most suitable manufacturing conditions in UFG and one in CG condition were identified based on processing efficiency (η) greater than 35 % (safe zone). Using the developed hot microforming setup, high precision Mg-RE microgears were manufactured successfully. The microgears manufactured in the optimized UFG condition showed highest geometric replication and dimensional accuracy with lowest standard deviation (0.78). The microstructural assessment of these microgears showed unrestricted and uniform material flow through the micro-die profile due to activation of grain boundary sliding (GBS) mechanism. The CG microstructure exhibited the worst repeatability and mechanical homogeneity, as indicated by a high standard deviation (19.01). In the CG microgears, twinning led to detrimental mechanical properties. Overall, this study created a strategy for producing Mg microgears and advanced the scientific understanding of microgear manufacturing.
Recently developed Al–Zn–Ca alloys with high thermal conductivity were consolidated from powders via laser powder bed fusion (LPBF) method. Particular attention is paid to the effect of Zn and Ca content on the defects formation and mechanical properties of the produced samples. It was found that the printed samples with the rated composition Al–6Zn–6Ca (wt.%) were characterized by the presence of a significant number of large cracks and demonstrated brittle behavior under tension loading. The total crack length increased inversely proportional to the volumetric energy density, which is atypical for LPBF-consolidated materials. In obtained samples with reduced zinc and calcium content of the rated composition Al–3Zn–4Ca, cracks do not form, and the ductility improves slightly (relative elongation up to 4.5%). Annealing at 400 °C for 1 h of the Al–3Zn–4Ca samples printed with a lower volumetric energy density provided a good combination of strength and ductility as well as overall ductile fracture behavior.
Medium-entropy alloys (MEAs), characterized by configurational entropy in the range of 1.0R<ΔSconf≤1.5R, represent a thermodynamically distinct space between traditional alloys and high-entropy alloys. With fewer constituent elements, MEAs offer simpler phase analysis and clearer mechanistic insights compared to more complex systems. At the same time, their entropy-stabilized structures remain highly responsive to thermal processing, making them especially compatible with additive manufacturing (AM) techniques. This review draws on over 200 studies from the last ten years, concentrating on laser powder bed fusion (LPBF) processing of CoCrNi-based systems (including CoNiV and CoNiTa) and refractory compositions (NbTiZr, NbTiTa). Other methods, such as directed energy deposition (DED), are addressed as complementary routes. The intense thermal gradients and fast cooling rates typical of AM foster complex, layered microstructures that promote twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP), resulting in superior strength and ductility compared to their cast counterparts. These enhanced properties are driving interest in structural components, soft-magnetic devices, cryogenic equipment, corrosion-resistant materials, and biomedical implants. The paper also examines progress in computational methods, including CALPHAD-based thermodynamic modelling, first-principles predictions of stacking fault energy, and machine learning for process refinement. However, model reliability remains limited by sparse training data. Key challenges persist, such as inconsistent documentation of processing parameters, vulnerability to defects in refractory compositions, and a lack of long-term performance and biocompatibility assessments. To accelerate the adoption of AM-fabricated MEAs, the development of standardized reporting practices and broader access to shared alloy databases is deemed essential.
Wave springs (WSs) are compact, lightweight alternatives to helical springs; although additive manufacturing enables complex WS geometries, prior work has focused on polymers. Herein, we design and manufacture Ti-6Al-4V WSs via electron beam additive manufacturing (EBAM). Seven WSs were designed using SolidWorks, and the fabricated specimens were evaluated through geometrical accuracy, surface roughness, quasi-static compression testing, and material characterization techniques. EBAM produced near-net geometry compared with the CAD, showing only minor deviations, with the lowest being 0.04 mm (WS2) and the largest being a 2.7 mm reduction in the height of WS7. In contrast, WS7 exhibited the smoothest top surface, with arithmetic mean height (Sa) values of 0.007 μm, whereas the surface along the build orientation was considerably rougher, with Sa values ranging from 45.84 μm (WS5) to 463 μm (WS1). WS2 and WS3 showed the best compressive response, sustaining peak loads of 6.84 kN and 8.267 kN, with energy absorption of 74 J and 75 J, respectively. SEM revealed unfused powder sticking to the sidewalls, which is linked with the higher Sa values on build-direction faces, while XRD showed only α-Ti (HCP) peaks. This study enables EBAM WS manufacturability and explicitly links geometry, process, and performance.
This study investigates the effects of seawater immersion and subsequent sun-drying on the compressive properties of solid and open-hole carbon/epoxy laminates. The specimens were manufactured using the Vacuum Assisted Resin Infusion (VARI) method and evaluated per ASTM D6641 standards. The water absorption behavior was analyzed over a 30-day period, indicating a saturation level of 0.65% by weight, along with significant changes in the mechanical properties of the composite. Compressive testing indicated that immersion in seawater resulted in decreased stiffness and maximum compressive capacity in both solid and open-hole laminates. Sun-drying for 12 h resulted in partial restoration of these properties; however, complete recovery was not achieved. Solid laminates exhibited a 26% decrease in compressive strength after immersion, followed by a 14% recovery upon drying. In contrast, open-hole specimens showed a 30% reduction and a 15% recovery. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FT-IR) spectroscopy analyses demonstrated the degradation of fiber-matrix interfacial bonding resulting from seawater exposure, along with the partial restoration of these bonds after drying. Failure mode analysis identified brittle fracture, delamination, and fiber-matrix debonding as the primary mechanisms occurring under compressive loading. Finite Element Analysis (FEA) predictions align with experimental curves during the elastic phase; however, they fall short in accurately representing progressive damage, especially in dried samples that display complex failure patterns. The integration of progressive damage modeling could enhance the accuracy of FEA. The findings indicate the partially reversible effects of seawater immersion and sun-drying on carbon/epoxy laminates, providing insights into their application in marine and humid environments.
This study investigates the effects of weld configuration (WC: single-sided and double-sided), welding pass number (WPN: single and two-pass), and post-weld heat treatment (PWHT) on the microstructure and mechanical performance of dissimilar AA7075–T651/AA2024–T3 friction stir welded (FSWed) joints produced under identical processing parameters. The double-sided (DS) configuration improved material flow and reduced internal defects due to enhanced stirring symmetry, but was less effective in achieving grain refinement in the stir zone compared with single-sided (SS) welding. SEM/EDS analysis revealed that the second pass (2P) was beneficial only for the SS configuration, whereas in DS friction stir welding (FSW) it caused excessive localized heating, leading to the formation of Cu-rich (θ–Al2Cu) intermetallic compounds (IMCs) and microstructural degradation. PWHT significantly improved microstructural homogeneity and grain refinement in single-pass (1P) conditions for both configurations, resulting in enhanced mechanical performance. The HT-1P-DSFSW joint exhibited the best performance, achieving an ultimate tensile strength (UTS) of 419.5 ± 17.4 MPa, elongation of 5.92%, and joint efficiency (JE) of 86.4% relative to AA2024-T3. Hardness mapping indicated that joint reliability correlates more strongly with hardness uniformity than with peak stir zone hardness.
Weak mechanical properties of biodegradable polymers, such as poly(butylene adipate-co-terephthalate), have led to many studies on adding cellulosic fillers to polyesters to develop composites with enhanced properties in order to make them suitable for more applications. This work aims at getting a better understanding of the effect of various cellulosic fillers with different sizes, aspect ratios, and contents on composites of PBAT as well as the impact of combining these fillers in the same blend. Melt mixing at 150 °C was used for the preparation of biocomposites with micro or nano-fibrillated cellulose (MFC), cellulose nanocrystals (CNC), and lignocellulosic fillers (LCF). The resulting biocomposite materials were characterized by tensile tests, dynamic mechanical analysis in solid and melt states, DSC and microscopic observations (SEM or TEM). Results indicated that composites reinforced with 10 wt% cellulose micro-fibrils, present a percolating network owing to their high aspect ratio, leading to the improvement of the mechanical properties of the polymer by increasing the Young’s modulus by 100% (from 80 MPa to 160 MPa). A synergistic reinforcement effect was identified in PBAT composites containing both CNC and LCF, resulting in a significant increase in stiffness of 35% when 5 wt% CNC were added simultaneously with 10 wt% LCF to the blend compared to only 19% improvement when added to the neat polymer. In contrast, the composite obtained with the MFC and LCL fillers kept the exact same improvement of about 35% indicating mainly an additive behavior. This enhancement in CNC/LCF composites occurs without a proportional loss in ductility relatively to MFC/LFC composites, highlighting the potential of combining fillers with distinct aspect ratios, such as LCF and CNC, to optimize mechanical performance.
Micro AJM (abrasive jet machining) is a more advanced non-traditional machining process utilised for making microchannels and micro holes on materials, especially brittle materials. It is one of the non-contact types of material removal processes, where highly pressurized abrasive particles and air are mixed in a mixing chamber and then impact the workpiece. The substance is eliminated through mechanical erosion. During machining, a large number of abrasive particles are discharged, which may create environmental contamination. To address this issue, an abrasive dust-collecting mechanism with the introduction of liquid film is studied in this study. In the present study the workpiece is placed inside of the liquid chamber, and used input process parameters as jet pressure, nozzle size, abrasive particle size, and liquid film thickness are varied, and their influence on the responses like radial overcut, material removal rate, and area of frosted zone are measured. The process variables are optimized utilising an AI approach. The ANOVA test is used to find the contribution of different variables to individual responses and also multi-response optimization using an AI approach. When there is no liquid film, the ideal MPI parameter levels are jet pressure 4 kgf/mm2, nozzle size 0.7 mm, and abrasive size 45 microns. Jet pressure of 4 kgf/mm2, nozzle size of 0.9 mm, abrasive size of 66 microns, and water film thickness of 1 mm are the ideal MPI parameter levels. Jet pressure of 4 kgf/mm2, nozzle size of 0.9 mm, abrasive size of 66 microns, and thickness of 1 mm in the case of glycerine film are the ideal MPI parameter settings. Additionally, it was shown that while a water liquid film improves MRR, the machining quality is low. Glycerine liquid film, on the other hand, results in high-quality machining with reduced MR. Improving dust absorption in Abrasive Jet Machining (AJM) lowers the danger of downstream contamination, enhances surface quality, and decreases airborne particulates. Manufacturers may reach tighter tolerances and cleanliness standards while reducing cycle time and consumable use by combining targeted dust capture devices with AI-based optimization of AJM process variables. This method can be used for various industrial processes, including medical device finishing, aerospace micro-deburring, precision optics polishing, semiconductor mask and wafer cleaning.
This paper addresses a primary limitation of single-point incremental forming (SPIF), non-uniform wall thickness, by developing a hybrid manufacturing route that combines SPIF with machining. The methodology supporting the proposed hybrid manufacturing route employs a computational implementation of the backward application of the point projection method, previously used to predict the final wall thickness of conventional SPIF parts. The approach involves machining tailored blanks with initially varying thicknesses from thicker sheets or plates, designed to compensate for material thinning during SPIF and achieve the desired final geometry and thickness. Experimental validation was performed using benchmark truncated cones with varying wall angles, and a proof-of-concept aeronautical component was fabricated, presenting uniform wall thickness. Results demonstrate that the proposed hybrid manufacturing route significantly improves thickness uniformity compared to conventional SPIF, reducing thickness deviations to below 10% in benchmark geometries and to approximately 3% in the industrial demonstrator. Additionally, it maintains geometric accuracy and achieves good surface quality. The integration of the backward application of the point projection method with a hybrid manufacturing route combining SPIF and machining constitutes a novel manufacturing approach that enables the systematic design and fabrication of tailored blanks with thickness-controlled thin-walled sheet metal parts, particularly suited for low-volume, high-value applications.
The increasing demand for lightweight components in the automotive and aerospace sectors has driven the development of advanced forming processes, as in the case of the Sheet-Bulk Forming (SBF). Among these, the sheet injection process, combining stamping and injection, enables the formation of complex features like ribs on metal sheets. However, when applied to medium-strength aluminium alloys, the process faces challenges, including high forming forces and limited formability, often resulting in material failure. The present study experimentally and numerically investigates the application of local Laser Heat Treatment (LHT) to achieve a specific distribution of properties as a strategy to improve the formability of medium-strength aluminium alloy AW6082-T6 in sheet injection operations. Several LHT strategies were developed to selectively reduce the mechanical strength in highly deformed regions of the sheet, thereby favouring the material flow and reducing forming loads. The results demonstrate that the local modification of the properties significantly decreases the process forces and reduces the risk of fracture and folding in critical areas. Experimental validation confirmed the numerical predictions, showing improved part quality. These findings highlight the viability of using LHT to expand the process window for SBF operations involving medium-strength aluminium alloys. The methodology offers a promising route for producing functional sheet metal components with enhanced performance.
Noise pollution has become a critical challenge, impacting human health and social progress. Nanomaterials, with their unique nanoscale properties, offer innovative solutions for noise control by enhancing the acoustic efficiency of sound-absorbing materials. This review highlights the integration of advanced nanomaterials, including carbon nanotubes (CNTs), graphene, nano-silica, and emerging alternatives such as nanofibers and hollow silica structures, into composite systems, and indicates that enhanced acoustic performance is most often achieved through appropriate nanofiller selection combined with tailored pore architecture and composite design. These materials exhibit exceptional improvements in Sound Absorption Coefficient (SAC), Noise Reduction Coefficient (NRC), and Sound Transmission Loss (STL). Factors influencing acoustic performance, such as material composition, structural properties, and environmental conditions, are explored alongside advancements in characterization techniques. By examining current trends and innovations, this paper underscores the transformative potential of nanomaterials in designing lightweight, durable, and efficient acoustic solutions for diverse industrial and environmental applications.
