J. Compos. Sci., Volume 10, Issue 8 (August 2026) – 62 articles

Natural biological materials achieve synergistic strengthening and toughening through soft–stiff dual-phase architectures, inspiring artificial composites. Despite extensive studies on individual bio-inspired designs, systematic comparative investigations under fully unified experimental conditions remain limited. Here, five representative bio-inspired composite structures (brick–mud, cross-lamellar, interlock, overlap, and concentric) are fabricated via 3D printing and compared under quasi-static three-point bending. Key mechanical parameters—including flexural modulus, flexural strength, crack-initiation displacement, effective fracture displacement, total energy absorption, and post-peak energy dissipation ratio—are derived from force–displacement curves, complemented by high-resolution imaging of crack paths, crack front morphologies, and fracture surfaces. The concentric structure exhibits the highest flexural modulus and flexural strength, yet fails catastrophically with only a 9.95% post-peak energy dissipation ratio. The brick–mud and cross-lamellar structures achieve the highest post-peak energy dissipation ratios (27.69% and 27.42%, respectively), which may be attributed to crack deflection and interfacial debonding, yet at the cost of low flexural strength. The interlock structure, apparently lacking effective deflecting interfaces, shows straight-through propagation and brittle behavior. In contrast, the overlap structure appears to benefit from sustained crack deflection along inclined interfaces, thereby providing a balanced combination of high flexural strength, large deformability, and moderate energy absorption, demonstrating the best overall mechanical performance. Full article

Triply Periodic Minimal Surfaces (TPMSs) represent a progressive class of cellular materials with high potential for high-tech applications. This review provides a comprehensive analysis of TPMS architectures, linking their mathematical underpinnings and advanced CAD modeling in PTC Creo Parametric 12 with technological aspects of additive manufacturing and macroscopic mechanical response. The work critically compares dominant topologies such as Schoen Gyroid, Schwarz Diamond, and Schwarz Primitive, focusing on the differences between uniform and functionally graded (FG-TPMS) structures. From a production perspective, this study identifies key process limitations of PBF-LB/M and SLA additive technologies, in particular the issues of unsintered powder accumulation, geometric deviations, and the negative impact of surface roughness (satellite particles) on fatigue life. Analysis of mechanical behavior confirms the superiority of sheet-based modifications in kinetic energy absorption, where specifically tailored FG-TPMS topologies exhibit stable deformation plateaus and controlled, progressive failure modes under compression. The conclusion of the work summarizes established applications in biomedical engineering for the elimination of stress shielding, as well as emerging trends in the field of 4D printing and acoustic metamaterials. This review serves as a comprehensive engineering guide for the optimization and implementation of next-generation porous structures. Full article

Glued laminated timber (glulam) is a high-performance structural wood product. However, means are still being researched to increase efficiency in challenges with a large scale of complexity, either owing to the diversity of the lamella’s material properties or through the development of computational models to better represent the real behavior of the material. This study aimed to determine a more efficient combined glulam beam in terms of the lamella’s proportion. The beams with a 12,000 mm span and a 150 × 600 mm cross-section were modeled using solid finite elements and a linear-elastic isotropic model. Two homogeneous and four combined glulam cross-sectional compositions were established based on the physical and mechanical properties of two strength classes (35 and 50 MPa), and their deflections and bending stresses were evaluated. Compared with that of homogeneous glulam beams with lamellae of the strength class 35 MPa, for softwood and hardwood lamellas, the combined cross-section with 33.3% of the lamellas of class strength 50 MPa, the load corresponding to the deflection limit increased by 17% and 12.4%, respectively. This composition had a higher self-weight only in relation to homogeneous glulam. It can be concluded that the combined glulam with a proportion of 33.3% was more efficient, considering the behavior of the beam under a load corresponding to the deflection limit, and that the lower self-weight affects the production and transportation processes. Full article

Searching by numerical simulation for structures with optimal damping properties among viscoelastic hollow cylindrical bodies with a filler is usually associated with a large amount of computation. Formulating the mechanical problem as one of natural vibrations and natural wave propagation makes it possible to evaluate the dissipative properties of such a structure independently of external force and kinematic actions, and thereby to reduce the computational cost substantially. The solution of the natural vibration problem for a piecewise homogeneous viscoelastic hollow cylindrical body with a filler yields complex natural frequencies, the real part of which represents the vibration frequency and the imaginary part the damping factor (attenuation rate). The mechanical behavior of the viscoelastic material is described by the linear Boltzmann–Volterra hereditary theory with a three-parameter Koltunov–Rzhanitsyn relaxation kernel, within which the material characteristics are represented by complex dynamic moduli—the shear modulus and the bulk modulus—that, as a rule, depend on frequency. In the natural vibration problem these moduli become functions of the real part of the sought complex natural frequency alone, which makes the standard eigenvalue procedures of commercial finite-element codes inapplicable. The paper presents an algorithm that removes this difficulty. The dispersion relation of the piecewise homogeneous cylinder is obtained analytically in the form of a complex determinant of order 12 for a two-layer and 18 for a three-layer configuration, the elements of which are Bessel and Neumann functions of complex argument; the global stiffness and mass matrices needed for the general configuration can be assembled automatically in a general-purpose finite-element code such as ABAQUS; the resulting complex characteristic equation is solved by Muller’s method—every iteration of which evaluates the determinant by Gaussian elimination with partial pivoting, so that no expansion of the determinant is required. The efficiency of the algorithm is demonstrated for a two-layer viscoelastic hollow cylindrical body with a filler, the outer load-carrying layer being made of Kh12 steel and the inner layer (the filler) of 30 L steel. The real and imaginary parts of the complex natural frequencies, of the phase velocities and of the attenuation are obtained as functions of the dimensionless wave number, of Poisson’s ratio, of the ratio of the layer radii and of the ratio of the instantaneous elastic moduli of the layers. Full article

This study utilizes Omani limestone waste powder (CaCO₃) sourced from the mountain ranges of the Sultanate of Oman as an economical natural reinforcement for scrap-based aluminum matrix composites (AMCs) using stir casting. The recycling of aluminum alloy from end-of-life automotive engine cylinder blocks was strengthened with limestone at volume fractions of 2.5%, 5.0%, and 7.5%. Mechanical characterization was conducted in accordance with ASTM standards (E8/E8M, E18, E23). Statistical significance (p < 0.05) was calculated using one-way ANOVA. The optimum 5.0 vol.% reinforcing fraction showed tensile strength, Rockwell hardness and Charpy impact energy of 130.9 MPa (+16.9%), 91 HRF (+19.7%) and 7.2 J (+28.6%) compared to the unreinforced scrap alloy (112.0 MPa, 76 HRF, 5.6 J). The results of Scanning Electron Microscopy (SEM) research showed that the composite of 5.0 vol.% had a uniform distribution of CaCO₃ particles and very low porosity, while the composite of 7.5 vol.% had a significant porosity (2–8 μm), interconnected microcracks and particle agglomeration. The porosity was increased with the increase of the content of the reinforcement as shown by the density experiments based on Archimedes’ principle. The maximum deviation of the experimental density from the predicted one was at 7.5 vol. % reinforcement. X-ray diffraction (XRD) confirmed the stability of the aluminum matrix structure as well as stable CaCO₃ phases without any evidence of harmful interfacial reaction products (Al₄C₃ or CaAl₂O₄). The findings confirm the optimal reinforcement ratio of 5.0 vol.% of Omani limestone, tackling both the environmental load of limestone quarrying waste and the expensive synthetic reinforcements, in accordance with the circular economy goals of Oman Vision 2040. Full article

In this study, polyamide 6/poly(butylene-adipate-terephthalate) (PA6/PBAT) blends, potentially applied as novel self-healing matrices for structural composites, were developed and characterized. The blends were melt-compounded at different PBAT amounts (from 20 up to 50%vol) and hot pressed. Rheological analysis showed a decreased in the storage and loss moduli of PA6 with PBAT, maintaining viscosity levels suitable for conventional melt-processing operations. FT-IR and FESEM observations demonstrated the formation of blends with immiscible morphology and uniformly dispersed PBAT domains. Quasi-static tensile tests showed a progressive decrease in tensile modulus and strength with PBAT, but a strong improvement in the elongation at break. The blend containing 30%vol PBAT showed satisfactory stiffness (2.2 GPa), strength (42 MPa) and elongation at break (10.5%) compared to PA6 (3.4 GPa, 62 MPa and 5.2%), thus this formulation was selected for self-healing assessment. Its repair efficiency was quantified as recovery of the fracture toughness (K_IC) after a thermal treatment at 150 °C for 30–120 min under pressure from 1–3 MPa. The highest healing efficiency (28%) was obtained after 120 min under 1 MPa, conditions at which the PBAT reduced its viscosity and flowed across the crack interface. Therefore, the blend with 30%vol PBAT will be considered in future for the preparation of multifunctional composites with thermal self-healing capability. Full article

In biofuel cells using laccase, the electron supply to the type 1 (T1) site is inefficient, constituting a major bottleneck for the overall reaction. To solve this problem, the use of mediator molecules that mediate electron transfer is being studied. Furthermore, lignin is known to be oxidized by laccase and can donate electrons, which indicates the potential application of this reaction in biofuel cells. Therefore, in this study, docking calculations were performed to clarify the interactions between a copper(II) complex mediator and laccase. At the same time, a copper complex mediator was selected, and cyclic voltammetry (CV) measurements were performed to evaluate its electrochemical properties. In the CV measurements, the differences in current responses with and without the mediator and lignin (an oxidized substrate of laccase) were compared. As a result, based on the docking calculations, it was proposed that the synthesized copper complex mediator binds relatively strongly to laccase. Moreover, CV measurements confirmed that the current tended to increase upon the addition of the mediator and/or lignin. This current enhancement explicitly demonstrates the efficient electron-providing effect of the mediator and lignin to the laccase-based system. Full article

This study investigated the development of biopolymer films from bitter cassava starch (Manihot esculenta) and coconut mesocarp cellulose as a promising alternative for biodegradable packaging. The biopolymer film was prepared using the casting method, with glycerol as a plasticiser and Tween 80 as an emulsifier. Different formulations were developed by varying the cellulose concentration to 6%, 8% and 10% to determine how this influences their physical and optical properties. FTIR analysis confirmed the presence of characteristic –OH, C–H, C=O, C–O–C and OH groups in the structure of the cellulose and starch, demonstrating their purity and chemical structure. It was found that the variation in cellulose within the starch polymer matrix significantly influences the microstructural organisation of the material, yielding film thicknesses of between 0.49 and 0.56 mm, with a moisture content ranging from 6.46% to 8.01% and a water absorption percentage between 67.7% and 109.5%; highlighting that the cellulose concentration of 0.4 g (8%) yielded the best results. This research contributes to bridging the existing gap in the utilisation of agricultural waste from bitter cassava and coconut mesocarp, integrating them to form biodegradable composites with potential use in biodegradable packaging, thereby strengthening environmental sustainability through the circular economy. Full article

The advancement of catalytic substrates through Additive Manufacturing (AM) offers notable benefits over conventional techniques, particularly for producing intricate three-dimensional forms that enable precise control over pore dimensions and surface characteristics. These attributes play a vital role in improving catalytic efficiency, which is evaluated by measuring pressure drop and mass transfer. This research focuses on the design and manufacture of a monolithic ceramic filter for catalytic cracking. The monoliths under study have a Triply Periodic Minimal Surface (TPMS) lattice. A macroporosity of about 65% is the criterion used to model the structures, and the TPMS unit cell length is the design parameter to achieve that porosity. Adapting a conventional Fused Filament Fabrication (FFF) desktop to use alumina filament, we produced samples based on three TPMS types: Schwar-Primitive (SP), Schoen Gyroid (SG), and Schwarz-Diamond (SD), which, after a plastic debinding process and subsequent sintering, resulted in meso-scale porous structures. The samples showed relative dimensional errors below 5% and a real total porosity of around 70%, with a maximum difference of 4% among the TPMS types. Because the printed SP lattices have the lowest unit cell length and real porosity, their pressure drop measurements were higher than those of the SG and SD. The opposite occurred with the estimated permeability. Although yielding similar pressure drop results, printed SG lattices had greater permeability than SD; therefore, in terms of monolith fluid dynamics, the SG lattice is the preferred geometry. Full article

Due to their high strength-to-weight ratio and corrosion resistance, carbon fiber-reinforced polymers (CFRPs) are increasingly used as tension elements in bridge engineering. Their pronounced anisotropy, resulting from stiff carbon fibers and a weaker polymer matrix, is critical for fatigue behavior under multiaxial dynamic stress states, such as those occurring in stay cables over saddles of extradosed bridges or at clamps of suspension-bridge hangers. This multiaxial loading can cause progressive damage accumulation in the contact regions and lead to premature failure. To study this efficiently, an energy-based progressive damage analysis (PDA) model for CFRP tension elements under multiaxial fatigue loading was implemented as a vectorized user material in ABAQUS^® 6.14 (VUMAT in FORTRAN) and validated against tension-tension fatigue tests on pin-loaded CFRP straps. The model was then applied to two representative bridge applications, viz. a clamped CFRP rod and a CFRP cable bent over a saddle, where parameters such as clamping pressure, maximum stress level, and friction coefficient were varied to quantify their influence on fatigue life and to assess suitability in line with fib recommendations. The results indicate that clamping pressures inducing transverse compressive stresses above roughly 85% of the CFRP’s transversal compressive strength significantly reduce fatigue life, whereas keeping the maximum fatigue stress below about 40% of the mean longitudinal tensile strength, the stress amplitude below 200 MPa, and the friction coefficient near 0.2 yields fatigue lives exceeding 2 × 10⁶ load cycles, which is satisfactory under fib criteria. Full article

Chitosan has emerged as a multifunctional biopolymer widely exploited in electrochemical sensing due to its unique physicochemical properties, including biocompatibility, film-forming capacity, protonated amino groups, and strong affinity for metal ions and biomolecules. These intrinsic characteristics enable efficient electrode modification, enhanced analyte adsorption, and immobilization of enzymes, nanoparticles, and 2D materials. In recent years, integrating chitosan with conductive nanostructures, such as carbon nanomaterials, metal oxides, metallic nanoparticles, and layered 2D materials, has significantly enhanced sensor performance, providing high sensitivity, selectivity, stability, and low detection limits across a broad range of analytes. This review presents an updated overview of chitosan’s roles in electrochemical sensing, including its functionalization techniques, electron transfer mechanism, and analyte identification. Key applications, such as biomolecule detection, heavy-metal monitoring, environmental pollutant analysis, pharmaceuticals, and emerging wearable sensing platforms, are discussed. Finally, current challenges and future research directions are highlighted to support the development of next-generation chitosan-based electrochemical sensors. Full article

Accidental web openings caused by impact, corrosion, or conflict-related damage can substantially reduce the strength, stiffness, and stability of steel bridge girders. Although numerous studies have examined beams containing intentionally designed web openings, limited experimental research has systematically compared practical rehabilitation methods for accidental openings in slender-web plate girders. This study experimentally and numerically evaluates several rehabilitation configurations incorporating welded patch plates and transverse stiffeners. Ten slender-web steel girder specimens, each 1800 mm long, 800 mm deep, and 300 mm wide, were tested under monotonic concentrated loading at mid-span. Nonlinear finite element models were also developed to qualitatively examine the principal deformation and instability trends. Relative to the control specimen, the untreated web opening reduced the ultimate load by approximately 43% and exhibited approximately 10% greater deflection at its respective ultimate load. One-sided and two-sided welded patch plates increased the ultimate load of the damaged specimen by approximately 22% and 26%, respectively. Transverse stiffeners increased the ultimate load by approximately 73% while exhibiting substantially lower ultimate-load deflections. The combined use of patch plates and transverse stiffeners provided the greatest improvement, increasing the ultimate load by approximately 101–123% relative to the untreated damaged specimen and substantially reducing lateral instability. The findings demonstrate that effective rehabilitation of slender-web girders requires not only restoration of the interrupted load path but also restraint of web instability. Full article

This study investigates the evolution of microstructural, mechanical, and transport properties in AZ31 magnesium alloy surface composites reinforced with Ti₂AlC MAX-phase particles at volume fractions of 6, 9, and 12 vol.%, which were fabricated by solid-state friction stir processing (FSP). In contrast to conventional brittle ceramics, Ti₂AlC MAX-phase mitigates interfacial reactivity and thermal mismatch. FSP successfully fabricated a highly consolidated, macroscopically defect-free, dynamically recrystallized fine-grained stirred zone with homogeneous particle distribution and metallurgically clean interfaces. Mechanically, the addition of 12 vol.% Ti₂AlC significantly improved the elastic response, increasing the Young’s modulus from 51 GPa to 67 GPa. The microhardness of the stirred zone reached 60.14 HV, a 53.4% increase over the base metal. The controlled electron and phonon scattering, enabled by the introduction of heterogeneous Mg/Ti₂AlC interfaces, decreased the electrical and thermal conductivities from initial values of 1.15 × 10⁷ S/m and 86.0 W/m·K for the unreinforced matrix down to 7.8 × 10⁶ S/m and 76.0 W/m·K, respectively, and caused a significant reduction in the coefficient of thermal expansion. Theoretical analysis, utilizing the Wiedemann–Franz law and Maxwell–Eucken approximations, provided a supportive baseline indicating the dominance of electronic thermal transport and interfacial scattering mechanisms. These results outline a viable route for developing lightweight magnesium-based composites with tailored mechanical and thermal characteristics for advanced structural applications. Full article

SrTiO₃/Nb₂O₅ composite materials with 1 and 10 wt.% Nb₂O₅ were prepared by a sol–gel route and characterized by XRD, Raman spectroscopy, SEM, BET, UV-Vis DRS, photoluminescence, and dielectric spectroscopy. The photocatalytic activity was evaluated via degradation of rhodamine B and tetracycline under UV and visible light. The addition of Nb₂O₅ resulted in a significant reduction in specific surface area (from 22.7 to 3.1 m²/g), a narrowing of the optical band gap (from 3.22 to 2.49 eV), and a decrease in photoluminescence intensity. Despite these changes, the photocatalytic performance decreased with increasing Nb₂O₅ content. For rhodamine B degradation, the UV rate constant fell from 0.0136 min⁻¹ for pristine SrTiO₃ to 0.0035 min⁻¹ for SrTiO₃/10% Nb₂O₅. The lower activity is mainly ascribed to the loss of active sites, surface carbonate formation, and enhanced non-radiative recombination at interface defects, which suppress charge transfer to the surface. The results demonstrate that careful control of the composite microstructure is essential for achieving efficient photocatalysis, even when heterojunction formation is thermodynamically favorable. Full article

Acute and chronic wounds remain a major clinical burden, motivating the design of multilayer biomedical composite systems capable of combining structural support, antimicrobial protection, and controlled release of therapeutic agents within a single device. These architectures integrate natural and synthetic biomaterials, hydrogels, electrospun membranes, bioactive nanoparticles, and 3D-printed scaffolds to reproduce the multifunctionality of the native extracellular matrix. This review examines how layer-by-layer design and biomaterial selection govern mechanical strength, as well as bioactivity, and how these parameters can be tuned to the distinct phases of wound repair. Particular emphasis is placed on strategies for incorporating growth factors, antimicrobial agents, metal/metal-oxide nanoparticles to enhance re-epithelialization, angiogenesis, and infection control; emerging gene-based delivery strategies are also discussed. The main technologies and biomaterial combinations reported to date are compared, alongside a critical overview of their in vitro and in vivo performance. Reproducibility, scalability, and regulatory standardization remain the main barriers to clinical translation. We conclude by outlining priority research directions to advance multilayer composites from bench-scale prototypes toward approved wound-care products. Full article

Satellite droplets and macroscopic distortions, induced by the non-Newtonian rheological behavior of ceramic inks, severely compromise the 3D inkjet printing of multilayer ceramics. To address these issues, we establish a two-phase fluid dynamics model coupling the Level Set method with the Carreau fluid model. The synergistic regulation mechanisms of the piezoelectric driving waveform, initial jet velocity, and pulse width under a high-shear field are elucidated. The results demonstrate that under the excitation of a rectangular pulse with an initial jet velocity of 6 m/s and a pulse width of 10–30 µs, the inertial force, surface tension, and internal non-Newtonian viscous dissipation of the fluid reach an optimal dynamic balance. This facilitates the on-demand ejection of spherical droplets while mitigating the formation of satellite droplets. Based on this, a 10 mm × 10 mm × 2 mm multilayer alumina ceramic packaging substrate was successfully fabricated, with the maximum relative dimensional error reduced from 2.6% to 1.4%. This study provides new insights into improving the 3D inkjet printing accuracy of ceramic devices. Full article

The Lorenz number is a critical parameter for separating the electronic and lattice contributions to thermal conductivity in thermoelectric materials through the Wiedemann–Franz law. However, the classical Sommerfeld approximation often fails to accurately represent the temperature-dependent transport behavior of BiSbTe-based thermoelectric materials. This study presents a systematic analysis of the temperature dependence of the Lorenz number using experimental data compiled from eleven independent studies. A unified database was established through literature review, data extraction, normalization, and statistical analysis. Linear, exponential, and quadratic regression models were evaluated to identify the mathematical representation that best describes the reported behavior, and a Processing Complexity Index (PCI) was introduced to examine potential relationships between fabrication-route complexity and the degree of nonlinearity. The compiled datasets consistently exhibited an overall increase in the Lorenz number with temperature, although noticeable variability in magnitude and curvature was observed among studies, reflecting differences in material composition, processing routes, and experimental conditions. While the quadratic model generally achieved the best statistical performance, linear and exponential models provided comparable fits for some datasets, indicating that no single functional form is universally optimal. The proposed correlations provide a statistically representative framework for improving thermal conductivity decomposition and thermoelectric characterization within the investigated temperature range (300–500 K). Nevertheless, the correlations are constrained by the scope of the literature-derived database and should not be interpreted as universally applicable predictive models. Full article

This study aims to reveal the formation mechanisms of typical defects in copper alloy castings and propose targeted process optimization strategies for production quality control. Taking the ZCuSn10P1 tin bronze outer layer of copper-clad iron core as the core research object, typical fracture and burr defects in actual mass production were systematically analyzed via multi-scale characterizations including SEM and EDS. Results show that fracture arises from abnormal Sn segregation and coarse hard-brittle δ phase, while burrs stem from insufficient matrix hardness during machining. Shrinkage cavity and porosity defects of aluminum bronze are further comparatively analyzed. A dual strategy of composition regulation and process optimization is put forward, which can effectively suppress defects and improve product qualification rate. This study provides a reliable reference for quality control and technical upgrading of copper alloy castings. Full article

This study investigates the shear behavior and failure mechanisms of innovative hybrid structural beams fabricated by filling pultruded glass fiber-reinforced polymer (GFRP) box sections with waste rubber-reinforced concrete (RuC). Environmentally friendly concrete was produced by replacing natural aggregate with recycled tire-rubber fibers at proportions of 0%, 5%, 10%, and 15%. Twelve hybrid beam specimens were tested to evaluate the synergistic effects of rubber content and stirrup spacings of 16, 20, and 27 cm on shear capacity, ductility, and crack propagation. The experimental results revealed that the reference specimen (S16-0%) exhibited the maximum shear capacity of 154.41 kN and a brittle failure mode, while an increase in rubber content to 15%, combined with wider stirrup spacing, significantly reduced this capacity to a minimum of 96.89 kN (S27-15%). However, the 5% rubber replacement ratio achieved an optimal performance balance by preserving sufficient load-carrying capacity while enhancing flexural deformation and ductility, particularly in specimens with 16 cm stirrup spacing. Damage analysis demonstrated that longitudinal splitting cracks initiated in the mid-span tension zone at the bottom of the pultruded profiles, with final localized damage concentrated at the geometric corners of the box section. Crucially, the outer pultruded GFRP profiles provided substantial structural confinement, effectively mitigating the strength loss associated with high rubber incorporation and controlling the progression of sudden brittle failure. These findings highlight that combining pultruded GFRP profiles and optimized RuC offers a structurally viable and sustainable solution for modern infrastructure applications. Full article

Laminated carbon fiber reinforced polymer (CFRP) beams are widely used in lightweight structures, yet their vibration response depends strongly on laminate architecture, boundary conditions, thickness, and material anisotropy. Previous studies often examined these effects separately or relied on a single analytical or numerical approach. This study presents a multi fidelity framework integrating classical laminate theory (CLT), the Vinson–Sierakowski (VS) equivalent modulus method, and three-dimensional finite element analysis for modal prediction and parametric design of symmetric CFRP laminated beams. Three stacking sequences, [0/0/0/0], [0/45/45/0], and [0/90/90/0], were evaluated under clamped-free (CF) and clamped-clamped (CC) conditions. ANSYS models using quadratic HEX20 solid elements served as the numerical reference. Across 36 validation frequencies, the mean absolute percentage errors were 3.05% for CLT and 2.28% for VS, giving VS a 25.1% lower average error. The [0/0/0/0] laminate produced the highest frequencies. The first numerical frequency increased from 36.37 to 230.20 Hz when the boundary condition changed from clamped-free to clamped-clamped. Increasing thickness from 2 to 8 mm raised the first frequency from 18.20 to 72.62 Hz, while increasing $E_1/E_2$ from 10 to 30 raised it from 30.80 to 53.85 Hz. The framework supports rapid screening, laminate level interpretation, and detailed numerical verification for vibration-oriented composite beam design. Full article

MXene composites represent an exceptionally promising member of the family of two-dimensional multifunctional materials known for outstanding electrical properties, mechanical strength, chemical tuning abilities, and the potential for wide applications. The paper conducts a profound patent landscape investigation of MXene composites with the help of the WIPO PATENTSCOPE database. In total, 658 patent families were found; duplicate patent entries were eliminated through the application of the Single Family Member method. The results show that China is a patent leader worldwide, followed by PCT applications and the patenting activity of the USA, India, and other countries, which indicates a growing international interest in MXene technologies and materials. The classification of patents also shows that this technology is actively researched in relation to the development of technologies in the field of electrochemical energy storage, polymer engineering, sensing technologies, catalysis, environmental remediation, electronics, and biomedical applications. Additionally, the paper studies the technology development in the field of the creation of MXene antennas, semiconductor devices, and ceramic oxide composites, materials that change shape, anti-corrosion coatings, electrochemical sensors, and many others. Even though substantial advances have been made, obstacles related to efficient manufacturing, oxidation resistance, quality assurance, sustainability, and industry adoption persist. The overall picture of patents shows that MXene-based composite materials have progressed from the testing stage to commercial products with high potential for next-generation technologies. Full article

The development of sustainable, high-performance friction composites is critical for the automotive industry, given the environmental and health concerns associated with conventional brake pad materials such as asbestos and copper. This study investigates the effect of incorporating micro- and nano-sized Al₂O₃, SiC, and carbon nanotubes (CNTs) into a novel, eco-friendly, asbestos-free, and copper-free brake pad formulation. Six composite samples were fabricated via a cold-pressing and hot-molding process: five formulations containing a single, size-controlled micro-/nano-sized reinforcement (Al₂O₃, SiC, and CNTs), and one reference formulation (CBP# Reference) containing an unrefined, commercial-grade combination of Al₂O₃ and SiC in place of the size-controlled additive. All formulations were rigorously characterized for their physical, mechanical, and tribological properties. The nano-Al₂O₃ formulation exhibited the highest density (2.197 g/cm³) and compressive strength (249.7 MPa), while the micro-SiC formulation achieved superior wear resistance, recording the lowest weight loss (0.0053 g) and the highest hardness (90 HV). The nano-SiC formulation offered the most balanced overall performance, combining high hardness (86.2 HV) with the highest average friction force (33.65 N) and the most stable friction-time response among all samples. The CNT-reinforced formulation produced the highest maximum friction force (42.07 N) but showed only moderate improvement in density, hardness, and compressive strength relative to the ceramic-reinforced samples. Compared with the CBP# reference, all five developed formulations exhibited higher hardness and coefficient of friction alongside lower weight loss, confirming their potential as durable, sustainable alternatives for automotive brake friction applications. Full article

(1) Background: This study aimed to assess how two different adhesive solvent evaporation techniques affect the microtensile bond strength (µTBS) of a universal adhesive to dentin, as well as the enzymatic activity of dentinal matrix metalloproteinases (MMPs) at baseline and after 6-month aging under simulated pulpal pressure. (2) Methods: Middle-depth dentin surfaces of 32 sound extracted human molars were bonded under simulated pulpal pressure using a universal adhesive (Clearfil Universal Bond Quick) in either etch-and-rinse (ER) or self-etch (SE) mode. Two solvent evaporation approaches were compared: evaporation with a disposable air/water syringe (air) and with a disposable suction device (suction), yielding four experimental groups (n = 8): ER/air, ER/suction, SE/air, and SE/suction. After light-curing for 10 s, a 4 mm composite build-up was created. Specimens were stored in distilled water under simulated pulpal pressure at 37 °C for either 24 h (T0) or 6 months (T6) and then sectioned into sticks and subjected to µTBS testing. Fracture surfaces were examined by scanning electron microscopy (SEM). An additional subset of teeth from each group (n = 3) underwent in situ zymographic analysis, in which bonded sticks were ground and exposed to fluorescein-conjugated gelatin, with enzymatic activity quantified by confocal microscopy. Statistical analysis was performed at a significance threshold of p < 0.05. (3) Results: Air-drying yielded significantly higher µTBS values than suction drying, irrespective of adhesive application mode (p < 0.05). At T6, SE groups retained bond strength values comparable to baseline (p > 0.05), whereas ER groups showed a significant reduction in bond strength with aging (p < 0.05). The ER mode and suction were associated with significantly increased MMP activity at T0 (p < 0.05), while there were no differences between SE/ER at T6 (p > 0.05), and air increased MMP activity (p < 0.05). (4) Conclusions: When using an ethanol-based universal adhesive under pulpal pressure, evaporation with a disposable air syringe combined with the self-etch application mode appears to offer greater bonding reliability and stability. Full article

This study evaluates sustainable dune-sand concrete produced using local dune sand, rice husk ash (RHA), and dried oil sludge. The experimental program included a control mixture (C0) and three modified mixtures (M1–M3). RHA was used as a partial replacement for Portland cement at contents of 20, 40, and 60 kg/m³, while dried oil sludge was introduced as a waste-derived additive at 10, 15, and 20 kg/m³, respectively. The total binder content, defined as Portland cement plus RHA, was maintained at 350 kg/m³, while the mixing-water content and water-to-binder ratio were kept constant at 185 kg/m³ and 0.53, respectively. The RHA was heat-treated at 800 °C for 60 min, immediately quenched in water, and subsequently dried at 105 ± 5 °C until a constant mass was achieved. Among the investigated compositions, M2, containing 310 kg/m³ Portland cement, 690 kg/m³ dune sand, 1110 kg/m³ crushed stone, 40 kg/m³ RHA, and 15 kg/m³ dried oil sludge, exhibited the most balanced overall performance. Its compressive strength reached 27.8 MPa at 7 days, 42.5 MPa at 28 days, and 47.7 MPa at 90 days, while its static modulus of elasticity was 32.7 GPa. M2 also showed the lowest water absorption (3.63%), the highest watertightness grade within the investigated series (W10), and the greatest measured freeze–thaw resistance, completing 223 cycles. Optical microscopy and X-ray diffraction observations indicated a visually more continuous matrix and lower relative intensities of several portlandite peaks in the modified concrete. For the replicate-based properties, mixture composition had a statistically significant effect (p < 0.001). Because RHA and dried oil sludge were varied simultaneously, the results represent their combined effect. M2 is therefore identified as the most balanced composition within the present limited test series, rather than as a universal optimum. Full article

Fiber-reinforced plastics (FRPs) exhibit significantly lower compressive strength than tensile strength, mainly because of fiber micro-buckling. During compressive failure, fiber micro-buckling leads to the formation of a kink band, in which fractured fibers are reoriented at a constant angle. Previous studies have shown that compressive strength and the fiber collapse direction are affected by initial fiber misalignment and remote shear stress, and that kink-band formation can induce subsequent damage, such as delamination. In this study, a three-dimensional mesoscale constitutive model is developed to represent these compressive failure mechanisms by introducing a coupling term between longitudinal normal stress and shear strain. The formulation is implemented in a numerical framework using a user subroutine in a commercial finite element solver. Numerical examples demonstrate that the proposed model reproduces the dependence of compressive failure behavior on both initial fiber misalignment and remote shear stress. Comparisons with experimental observations indicate the potential of the proposed model to predict compressive strength, while qualitatively capturing the interaction between compressive damage and delamination. Full article

The increasing scarcity of conventional feedstocks for WPCs requires alternative resources supporting circular material flows in the wood-based bioeconomy. This study investigated thermomechanical pulp (TMP) fibers from fresh, recovered, and beetle-infested spruce as well as fresh beech as reinforcements for polypropylene-based WPCs. Fiber geometry was characterized before and after injection molding, and composite performance was evaluated with and without a maleic-anhydride-grafted polypropylene coupling agent. After injection molding, the aspect ratio ranged from 7.1 to 7.9, with recovered spruce showing the highest value. The addition of 30 wt.-% TMP fibers increased the tensile modulus from 1.4 GPa for neat polypropylene to as much as 4.7 GPa for the coupled WPCs. Compatibilization markedly improved strength, resulting in tensile strengths of up to 54 MPa and flexural strengths of up to 80 MPa, compared with 33 MPa and 36 MPa for neat polypropylene, respectively. Recovered and beetle-infested spruce did not impair composite performance and achieved the highest tensile and flexural strength values. Beech-based WPCs showed lower tensile and flexural performance than spruce-based composites but still reached a technically relevant property level. Overall, recovered and beetle-infested spruce and fresh beech represent viable TMP raw materials for mechanically demanding WPC applications. Full article

A fully coupled three-dimensional (3D) thermo-magneto-elastic layer-wise formulation is developed for the analysis of multilayered flat and curved panels used in aerospace and aeronautical applications. The model relies on a system of coupled second-order differential equations along the thickness coordinate z, formulated in a mixed orthogonal curvilinear reference system. The governing equations combine the three-dimensional equilibrium equations with the magnetic induction divergence equation and the heat conduction equation, providing a unified multifield framework for thermo-magneto-elastic analyses. Through a suitable definition of the curvature parameters, the same formulation can be directly applied to plates, cylinders, cylindrical panels, and shells with constant radii of curvature. The governing equations are analytically solved by adopting harmonic expansions in the in-plane directions together with the exponential matrix method along the thickness coordinate. The harmonic representation naturally satisfies simply-supported boundary conditions along the panel edges. The multilayered structure is modeled according to a layer-wise strategy, where the continuity of the selected mechanical, magnetic, and thermal variables is enforced across the interfaces between adjacent layers. Different loading boundary conditions can be assigned at the external surfaces by prescribing pressure loads, magnetic potential, transverse magnetic induction, and over-temperature. The numerical investigation is divided into two stages. First, the accuracy of the proposed formulation is verified through comparisons with thermo-magneto-elastic solutions available in the literature. Then, a comprehensive set of new benchmark results is presented by considering different geometries, thickness ratios, and loading boundary conditions. Both tabulated values and through-the-thickness distributions are reported for the most significant field variables. These benchmark results provide useful reference data for the assessment and validation of future two-dimensional and three-dimensional analytical and numerical formulations devoted to coupled thermo-magneto-elastic problems. Full article

The ballistic performance of a non-commercial aramid/epoxy composite laminate subjected to Fragment Simulating Projectile (FSP) impact was investigated through combined experimental testing and numerical simulation. Ballistic tests were performed in accordance with STANAG 2920 to determine the ballistic limit velocity (V₅₀). Complete and partial penetration responses were identified, with the ballistic transition region occurring between 412 and 452 m/s. The experimental ballistic limit was V₅₀ = 440.57 m/s. A three-dimensional finite element model was developed in ANSYS^® AUTODYN 2026 R1 using a Lagrangian formulation and an orthotropic constitutive model incorporating elastic behavior, stress/strain-based failure criteria, post-failure response, and geometric strain erosion. The numerical simulations predicted a ballistic limit of V₅₀ = 440.65 m/s, corresponding to a relative difference of less than 0.03% with respect to the experimental result. The numerical model successfully reproduced the ballistic transition, damage evolution, projectile velocity history, and energy transfer during impact, providing good agreement with the experimentally observed penetration responses. These results demonstrate that the proposed methodology provides a reliable and validated framework for predicting the ballistic response of aramid/epoxy composite laminates under standardized FSP impact conditions and supports the design and evaluation of lightweight composite armor systems. Full article

This study investigates adhesively bonded composite patch repair to enhance the load-carrying capacity of damaged metallic structures, introducing a novel FE-augmented machine learning (ML) framework that addresses the limited availability of experimental data in structural repair applications. To evaluate this approach, aluminum and steel specimens with central fatigue cracks were repaired using glass-fiber/epoxy and carbon-fiber/epoxy composite patches and tested under quasi-static loading at room ($70 \mathrm{F} °$), high ($145 \mathrm{F} °$), and low (−$60 \mathrm{F} °$) temperatures. Finite element (FE) models were then developed in ABAQUS© to predict the failure loads of the patched specimens under varying temperature conditions, showing excellent agreement with the experimental data. The high accuracy of the FE predictions enabled their use as additional training data, effectively augmenting the limited experimental dataset and allowing the development of more robust regression models. Ten machine learning (ML) regression models, including linear regression (LR), polynomial regression (PR), support vector regression (SVR), random forest (RF), gradient boosting (GB), XGBoost (XGB), LightGBM (LGBM), Gaussian process (GP) regression, artificial neural networks (ANNs), and Kolmogorov–Arnold networks (KANs), were trained to predict the failure load of both unpatched and patched specimens as a function of material type, temperature, specimen thickness, crack length, and, for patched specimens, patch type and thickness. The datasets combined a limited set of physical results (75 patched samples: 63 experimental and 12 finite-element; 72 unpatched samples: 27 experimental and 45 theoretical) with Gaussian-mixture-model synthetic samples used only to augment the training data up to 300 samples per case. Under a configuration-grouped, leakage-free nested cross-validation (entire configurations held out for testing, hyperparameters tuned on inner folds only), the best models predicted the failure load of unseen configurations with mean absolute percentage errors of 2.78% (Gradient Boosting, patched, $R^2=0.87$) and 3.33% (Gaussian Process, unpatched, $R^2=0.98$). A paired ablation showed that Gaussian-mixture-model augmentation did not improve accuracy and, for several models, actually reduced it; the final models therefore rely on the real multi-source (experimental, FE, and theoretical) data, with the synthetic pipeline reported as a validated but non-beneficial component for these datasets. Overall, this study provides a novel, data-efficient framework combining experimental testing, FE simulation, and validated regression modeling to predict the performance of adhesively bonded composite patch repairs under varying thermal and mechanical conditions. Full article

Composite overwrapped pressure vessels (COPVs) present a tractable recycling target as the production/recovery methods do not require cutting fibers, permitting recovery and re-spooling of continuous fiber tows. To address the gap between lab-scale recycling methods and commercial COPVs as a target application, an apparatus is required to control the unwinding process during recycling. A fiber management system (FMS) was designed and produced to maintain tension in the fiber tows and prevent tangles during unwinding filament-wound structures. To demonstrate the effects of the FMS, vitrimer composite tubes were produced, the matrix was dissolved, and recovered tows were used to produce a second tube. Second-generation specimens, some produced from tows unwound with the FMS as well as some from tows recovered manually, were cut into coupons and the tubular short-beam strength was measured. Specimens remanufactured with recovered tows unwound with the fiber management system exhibited an 11% increase in strength compared to specimens that were manually unwound (p = 0.048) and were statistically indistinguishable from first-generation tubes (p = 0.22). Maintaining control of the fiber tows resulted in full retention of mechanical properties in addition to automating and simplifying the unwinding process. Full article