This study investigates the flexural behaviour of reinforced concrete beams strengthened with a hybrid reinforcement system comprising both steel and fibre-reinforced polymer (FRP) bars, with a specific focus on serviceability deflection performance. The incorporation of FRP reinforcement offers significant advantages in terms of corrosion resistance and reduced self-weight, making it an attractive complement to conventional steel reinforcement. However, the linear-elastic response of FRP up to failure, combined with its lower modulus of elasticity, limits its suitability as a complete replacement for steel. Hybrid reinforcement systems therefore present a promising compromise, combining the ductility of steel with the durability of FRP. An extensive database of experimental tests on hybrid reinforced beams, compiled from the literature, was analysed. Measured mid-span deflections were compared with predictions from established guidelines. The findings indicate that many existing models tend to underestimate deflections, which may have implications for both serviceability and long-term structural performance. To address these discrepancies, the analytical models were recalibrated by introducing correction factors derived through multiple error functions, including mean squared error (MSE), mean absolute error (MAE), mean absolute percentage error (MAPE), and the coefficient of determination (R²). Finally, a parametric analysis identified the most influential variables affecting deflection, including the stiffness ratio between steel and FRP reinforcement, the proportion of FRP reinforcement, and the shear span-to-depth ratio. The results provide valuable guidance for optimising hybrid reinforcement design and contribute towards the development of dedicated design provisions, addressing current gaps in structural codes and promoting the wider adoption of steel–FRP hybrid systems in civil engineering practice.

Essential oils have been extensively explored across different industrial sectors due to their multiple bioactive properties and health benefits. Among their main constituents, terpenes stand out, with limonene being one of the most abundant in nature, particularly present in citrus essential oils. This compound possesses well-recognized antioxidant, antimicrobial, aromatic, and therapeutic activities, making it a promising candidate for applications in pharmaceuticals, cosmetics, food products, and sustainable materials. However, its high volatility and sensitivity to adverse environmental conditions limit its stability and direct application, making microencapsulation an essential strategy for preserving its functional properties and enabling controlled release. Therefore, the aim of this study was to produce limonene microcapsules via complex coacervation using natural biopolymers, such as chitosan and gum arabic, in order to investigate the effect of biopolymer concentration and limonene content on productivity as well as on the chemical and morphological properties of the particles. The microcapsules were characterized in terms of morphology, solid content, particle size, and encapsulation efficiency. Microscopic analyses revealed predominantly spherical and uniform morphologies, with diameters ranging from 1 to 10 µm. The solid content varied from 2.06% to 5.68% (w/w), influenced by formulation composition and close to the theoretical values calculated. Particle size distribution by laser diffraction showed mean values between 0.74 µm and 1.22 µm. Encapsulation efficiencies were remarkably high, exceeding 99% in all trials. The results confirm the feasibility of complex coacervation with natural biopolymers as a sustainable, versatile, and highly efficient method for limonene microencapsulation. This approach not only ensures the protection and stability of the compound but also enables its incorporation into innovative formulations, driving the development of functional products with high added value across different industrial sectors.

This research investigates the thermal modification (TM) of European black alder (Alnus glutinosa) wood boards (1000 x 100 x 25 mm), treated under nitrogen atmosphere at 4 bar starting pressure. TM was performed at temperatures of 160°C and 170°C for 30, 60, 120, or 180 minutes. Despite growing interest, detailed studies on the impact of TM on black alder wood, particularly under nitrogen pressure, are scarce.

The TM process resulted in mass reductions ranging from 4.6% to 8.6%, with shrinkage observed across all anatomical directions. Water retention decreased significantly, with the cell wall’s total water content dropping from 35% to a range of 14%–27%. Anti-swelling performance improved, with efficiency between 21% and 61%. Notably, the treated wood exhibited more than a 50% reduction in volumetric swelling and equilibrium moisture content compared to untreated samples.

Regarding mechanical properties, a decrease in the modulus of rupture was noted, particularly for treatments at 160°C for 180 minutes and 170°C. On the other hand, the modulus of elasticity saw minor increases, though they were not substantial. Brinell hardness tests highlighted a significant contrast between the tangential and radial surfaces, with the tangential surface demonstrating notably lower hardness.

In conclusion, TM substantially improves dimensional stability and moisture resistance in black alder wood. The dark brown color developed during TM enhances its visual appeal, making it a competitively priced alternative to more expensive wood materials. This study expands the knowledge of TM applied to black alder, demonstrating its potential for use in sustainable wood product industries.

Introduction
Fused deposition modeling (FDM) is a widely used additive manufacturing technique valued for its affordability and accessibility. Despite its widespread adoption in education, prototyping, and hobbyist use, FDM often suffers from quality and consistency issues. Common problems such as warping, stringing, first-layer adhesion, or dimensional inaccuracies reduce the functionality and reliability of 3D-printed prototypes. Understanding the causes of these issues is essential to improving print quality and expanding the applicability of low-cost 3D printing.

Methods
A series of standardized models were manufactured using desktop FDM printers under controlled conditions. Key variables such as nozzle temperature, material type, layer height, cooling, and filament quality were systematically investigated. The manufactured pieces were evaluated through visual inspection and dimensional measurement to assess the presence and severity of defects. Environmental factors and hardware calibration (e.g., bed leveling) were also considered.

Results
This study identified clear correlations between specific printing parameters and the emergence of imperfections. Among the findings is that warping is strongly influenced by material choice and bed temperature. An excess of deposited material is a consequence of non-optimal nozzle temperature selection. Additionally, filament quality and printer maintenance were found to have a significant impact on print reliability.

Conclusions
The findings of this work highlight the importance of parameter optimization and equipment upkeep in achieving consistent FDM print quality. A set of practical guidelines is proposed to help users diagnose and mitigate common printing issues. These recommendations aim to support both novice and experienced users in enhancing the performance of their FDM fabrications. Ultimately, this research contributes to the broader goal of making desktop 3D printing more reliable for functional and engineering-oriented applications.

TRIP (Transformation Induced Plasticity) steels, also referred to as TRIP-Assisted Steels, constitute a class of advanced high-strength steels characterized by their complex multiphase microstructures. These steels are extensively employed in the automotive industry due to their superior combination of high tensile strength, excellent ductility, and relatively low weight, which contribute significantly to vehicle lightweighting. Typically, these alloys present low carbon content, combined with small additions of alloying elements such as silicon, manganese, and aluminum, which play a fundamental role in suppressing carbide precipitation and stabilizing the retained austenite phase. From a metallographic perspective, one of the major challenges lies in the accurate identification and quantification of the individual phases present in TRIP steels. Conventional chemical etchants are usually insufficient, as they fail to distinctly reveal the multiple phases associated with such complex microstructures. In this context, this work reports the application of the LePera reagent to distinguish the multiphase constituents. The etchant was prepared and applied following standard metallographic procedures to ensure reproducibility and reliability of the microstructural characterization. The application of the LePera etchant produced a distinct contrast between the phases present in the TRIP steel microstructure. Ferrite grains were revealed in shades of blue, while bainitic regions appeared in a characteristic brown coloration. The martensite–retained austenite constituent (M–A), which cannot be distinguished into its individual components through this reagent, was observed as bright white areas distributed within the matrix. Although LePera etching provides valuable insight into the distribution and morphology of these phases, it does not permit the separation of martensite and retained austenite, which remain indistinguishable within the M–A constituent. Therefore, complementary characterization techniques or alternative chemical etching methods are necessary to achieve a more precise differentiation and quantification of these critical microstructural constituents.

Residual stress is a critical challenge in laser powder bed fusion (L-PBF) that can compromise the mechanical performance and dimensional accuracy of printed parts. This study investigated the role of scanning strategy on residual stress mitigation and temperature distribution in Ti-6Al-4V components fabricated by L-PBF. Six scanning strategies, comprising three continuous and three discontinuous patterns with rotation angles of 45° and 67° and unidirectional paths, were evaluated using a combined experimental–numerical approach. Experimental analyses included computed tomography (CT), surface roughness and hardness tests, and X-ray diffraction (XRD) residual stress measurement, while thermal and static finite element simulations were conducted to capture temperature evolution and stress distribution.

The results revealed that discontinuous strategies generally outperformed continuous ones in mitigating defects and residual stress. In particular, the discontinuous 67° rotation strategy exhibited the most favorable performance, achieving a high relative density of 99%, reduced peak temperatures, the lowest residual stress of 220 MPa, and a uniform stress field. CT analysis confirmed that continuous 45° rotation yielded the lowest density (97%) due to poor overlap and possible keyhole porosity, whereas discontinuous patterns reduced porosity and improved surface finish. Thermal simulations indicated that continuous strategies generated smoother but more heat-accumulated fields, leading to higher stresses, while discontinuous approaches facilitated thermal relaxation and stress homogenization.

This study demonstrated the importance of choosing scanning strategies for residual stress mitigation in L-PBF. The insights gained provide valuable guidance for improving the structural integrity and reliability of additively manufactured components.

This study presents an investigation into the strength prediction of adhesively bonded single lap shear joints subjected to elevated temperatures, with a focus on capturing the adhesive response beyond the glass transition temperature (Tg). Finite element analysis with Ansys was used to simulate the mechanical behavior of single lap shear joints made of Aluminum 6061 T6, with a thickness of 1.5 mm substrates and Henkel LOCTITE EA 7000 structural adhesive. This epoxy adhesive has excellent moisture and corrosion resistance in high humidity environments with a minimal reduction in mechanical properties. The simulations incorporated temperature-dependent material response to predict joint strength under thermal and mechanical loading. Experimental validation was conducted through single lap shear tests at temperatures ranging from ambient to above the adhesive’s Tg, highlighting the agreement between simulated and experimental results. The test specimens were made according to ASTM D1002. The results show a drop in the joint strength above the glass transition temperature. The observed drop in could be attributed to the thermal degradation and oxidation in the adhesive which, in turn, reduces its adhesion and cohesion properties. The findings highlight the critical influence of temperature on adhesive performance and joint's structural integrity, providing valuable insights for designing reliable bonded structures at elevated temperatures.

This work explores the design, simulation and manufacturing of energy-absorbing two-dimensional lattice structures, aiming to identify geometries and processes that improve impact mitigation and lightweight performance. Several representative lattices were selected from literature or modified, including honeycomb, anti-tetrachiral and others. CAD models were prepared in CATIA V5 and evaluated with finite element analysis. Both static compression and explicit dynamic simulations were carried out in Ansys to study elastic-plastic behaviour, reaction forces and energy dissipation. The comparison showed that while honeycomb remains a conventional reference, auxetic and anti-tetrachiral geometries displayed greater capacity for plastic deformation and lower transmitted forces, which are desirable for energy absorption.

In addition to structural simulations, manufacturing feasibility was investigated. Additive manufacturing by Selective Laser Melting (AlSi10Mg) and investment casting with additive-assisted moulds were simulated in Altair Inspire and Inspire Cast. Preliminary coupons were also fabricated by polymer FDM printing to verify geometrical consistency and prepare for mechanical testing. These first physical prototypes confirm that the designed structures can be produced with acceptable accuracy and provide the basis for further experiments.

The study highlights the strong influence of lattice geometry on energy absorption efficiency and underlines the importance of combining digital modelling, process simulation and preliminary prototyping. Future work will extend the study to full mechanical tests on manufactured coupons to validate the numerical simulations. The results are expected to support the selection of one or two lattice families that combine mechanical efficiency with robust and cost-effective manufacturing processes.

Duplex stainless steel (DSS) cladding offers an attractive solution for combining the corrosion resistance and strength of DSS with the low cost of mild steel substrates. This approach is highly relevant for industries such as chemical processing, marine engineering, and energy systems, where enhanced durability and reduced material costs are critical. A major challenge, however, is dilution at the clad-substrate interface, which can degrade the intended properties of the DSS overlay. This study investigates the influence of plasma transferred arc (PTA) cladding parameters on dilution and associated deposition characteristics. Systematic variation of current (150 A-170 A), wire feed rate (1.1 m/min-1.3 m/min) and travel speed (1.0 mm/s-2.5 mm/s) resulted in heat inputs between 1.39 KJ/mm and 3.94 kJ/mm, corresponding to dilution levels between 34% and 45%. Higher current and lower travel speed increased heat input, leading to deeper penetration (1.6 mm-3.9 mm) and wider beads (5.6 mm-11.5 mm). Energy-dispersive spectroscopy (EDS) across the clad-dilution region revealed progressive Fe enrichment from 58.6 wt% to 69.7 wt% with rising dilution, accompanied by Cr and Ni depletion from 29 wt% and 7 wt%, respectively (feedstock) to 18 wt%-21 wt% Cr and ~4.5 wt% Ni. Microhardness measurements exhibited limited variation (within ±10%) despite these compositional shifts, indicating that hardness does not directly reflect dilution. These results establish quantitative correlations between process parameters, dilution and composition, providing a framework for optimising PTA cladding conditions to achieve high-performance overlays on low-cost substrates.

Introduction: Additive manufacturing has significantly advanced the fabrication of complex structures, with 3D printing offering precision, customization, and reduced waste compared to conventional methods. Building on this foundation, 4D printing introduces time as an additional dimension, allowing printed objects to transform in response to external stimuli such as heat, light, water, stress, or magnetic and electric fields. This innovation expands the potential of additive manufacturing from creating static structures to developing dynamic, stimuli-responsive systems.
The concept of 4D printing was first introduced by Skylar Tibbits in 2012, marking the beginning of research into integrating smart materials with 3D printing technologies. Since then, this field has grown rapidly, opening new possibilities across scientific and industrial domains.

Methods: The success of 4D printing depends on the choice of materials. These can be broadly classified into metals, which provide structural strength; ceramics, offering thermal stability; polymers, particularly shape-memory polymers enabling flexibility and responsiveness; and composites, which combine the advantages of multiple classes to achieve multifunctional performance. Fabrication techniques rely on advanced adaptations of existing 3D printing technologies such as stereolithography (SLA), fused deposition modeling (FDM), and selective laser sintering (SLS). Results: The 4D printing process results in products with several applications, extending from general uses to medical applications such as adaptive prostheses. Within dentistry, its potential is particularly promising, with opportunities for self-adjusting orthodontic aligners, adaptive prosthodontic devices, smart scaffolds for regenerative dentistry, and restorations that respond to the oral environment. Conclusions: Four-dimensional printing represents a transformative step in dentistry, shifting from static to smart solutions.