Journal of Composites Science

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

Conventional soldered interconnects—necessarily requiring high-temperature processes to melt solder (tin)—are posing reliability challenges to crystalline silicon solar cell modules due to residual stress stemming from the mismatch of the coefficient of thermal expansion of the materials involved. On the other hand, electrically conductive adhesives (ECAs) have been shown to exhibit sufficiently promising improvements in mechanical and electrical properties to be used as silicon solar cell interconnects. However, the current ECA technology is dominated by ECAs with dispersed silver particles, which makes them costly and could cause embrittlement of the ECA at higher concentrations. This study investigates the potential application of a novel ECA, with composite metal particles, made of a nickel and Sn95Ag4Cu1 solder mixture and dispersed in a high-density polyethylene matrix for the solar cell interconnection. The test PV modules show comparable electrical and mechanical performance to that of soldered cell modules, despite the fact that the ECA application is still rather early in its learning curve. The present study suggests that the novel ECA could lead to a promising alternative to the conventional soldering process and the more costly silver-filled ECAs. Full article

The development of modern types of ammunition and the increasing requirements for ballistic protection have created a need for armour systems capable of providing a high level of protection while maintaining an acceptable weight. Traditional homogeneous armour systems, primarily based on steel materials, have gradually become insufficient against high-velocity projectiles and shaped-charge munitions, leading to the development of multilayered and hybrid protective systems that combine materials with different mechanical properties. The aim of this review article is to systematically analyse the development of armour systems, from homogeneous metallic armour to modern multilayered and hybrid composite configurations, and to identify the key mechanisms responsible for increasing ballistic resistance while reducing areal density. The article synthesises and critically evaluates findings published in the available scientific literature focused on metallic, ceramic, polymeric, and hybrid armour systems. Particular attention is paid to mechanisms of energy absorption, projectile fragmentation, stress redistribution, and interactions between individual layers under dynamic loading. The analysis of published studies indicates that multilayer composite armour systems achieve higher ballistic efficiency than homogeneous systems due to the synergistic action of several protective mechanisms. Ceramic layers provide projectile destabilisation and fragmentation, while metallic and polymeric backing layers effectively absorb the residual energy and capture the resulting fragments. The findings also highlight the importance of armour architecture, the sequence of individual layers, and the quality of interfaces between materials, all of which significantly affect the resulting ballistic resistance, multi-hit capability, and the ratio between the level of protection and system weight. Current trends in armour technology development are directed towards the optimisation of multilayer configurations, the use of hybrid materials, bio-inspired architectures, graded structures, and advanced manufacturing technologies. The objective is to develop lightweight multifunctional armour systems that provide a high level of protection without a significant increase in areal density. Full article

Polymer infiltration and pyrolysis (PIP) is a versatile route for densifying carbon–carbon composites (C/CCs) and ultra-high-temperature ceramic matrix composites (UHTCMCs), particularly SiC and UHTC-based systems. It operates at comparatively low temperatures, accommodates complex shapes, and is more cost-effective than chemical vapor infiltration (CVI). However, conventional PIP has intrinsic limitations, including low ceramic or char yield, significant shrinkage and gas evolution during pyrolysis, and the need for many infiltration–pyrolysis cycles to reach useful densities. Recent strategies to reduce these drawbacks include graded-concentration and high-pressure PIP, as well as hybrid CVI–PIP and PIP–reactive melt infiltration (RMI) schemes. In parallel, a separate body of work has shown that vacuum-assisted and vibration-assisted infiltration can improve impregnation quality in carbon or ceramic fiber preforms and in carbon-based UHTCMCs. Yet, these advances are rarely synthesized from a PIP-centered, manufacturing-focused perspective or systematically extended to the densification of porous C/C structures, particularly when high-viscosity modified phenolic or particle-laden preceramic precursors are used. This review summarizes the state of the art in PIP densification and processing–structure–property relationships in modified C/CCs or UHTCMCs and related high-temperature composites. It then examines vacuum- and vibration-assisted infiltration concepts, extracts the underlying fluid- and pore-scale mechanisms, and proposes design principles for enhanced PIP equipment and processes tailored to porous and modified C/C systems for space and defense thermal protection. Full article

Composite aerogels based on polytetrafluoroethylene (PTFE) and graphene oxide (GO) with a high polymer content of 90, 95 and 98 wt.% were synthesized for the first time. It was found that GO performs a structure-forming function, allowing the production of monolithic three-dimensional frameworks stable under freeze-drying conditions even at a minimal concentration of 2 wt.%, whereas pure PTFE is destroyed under these conditions. Subsequent annealing of the composites at 370 °C, which is higher than the decomposition temperature of oxygen-containing groups of GO and the melting point of PTFE, leads to the formation of PTFE/reduced graphene oxide (rGO) aerogels. A direct dependence of shrinkage during annealing on the polymer content was observed: it sharply increases from 2.1% to 26.6% with an increasing proportion of PTFE. This effect is explained by the dominant role of capillary forces pulling together the rGO sheets in the molten polymer, while the rGO frame resists the shrinkage. The most significant result is the achievement of a record low water sorption capacity (Q_w) for an aerogel with 98% PTFE, amounting to only 0.001 g/g. This value is several orders of magnitude lower than that of pure rGO aerogel (~20 g/g), confirming that a high content of hydrophobic polymer combined with thermal treatment effectively shields the hydrophilic sites on the surface of the rGO sheets. The composites obtained in this work exhibit high hydrophobicity (contact angles up to 144°) and unique potential for the selective absorption of organic solvents from water. Full article

The nano-hydroxyapatite/β-tricalcium phosphate composite (nano-HA/β-TCP) is widely used in various medical and dental procedures. The absence of in vivo toxicity of nano-HA/β-TCP has been extensively studied, and it is considered one of the most effective synthetic biomaterials for promoting cell differentiation in bone regeneration. Bone marrow-derived mesenchymal stem cells (BM-MSCs) are the primary cell type involved in the osteoinductive process of guided bone regeneration following injury. In the present study, rat BM-MSCs were cultured with nano-HA/β-TCP (80/20%) composite spheroids, and the interaction between the cells and the composite was analyzed using transmission electron microscopy (TEM). Ultrathin sections examined by TEM showed extensive interaction between nano-HA/β-TCP and BM-MSCs. Semi-thin sections stained with toluidine blue revealed the incorporation of the biomaterial into the cell cytoplasm. For the immunohistochemistry analysis, eight adult male Wistar rats weighing approximately 300 g were used in each group. Two bilateral, non-critical-sized 3 mm defects were created in the parietal bones of the calvaria: Control, Bio-Oss^®, and Blue Bone^® (n = 24) during a 12-week experimental period. Bone formation was evaluated through osteonectin and osteopontin expression. At the ultrastructural level, internalization of the biomaterial and close association with the endoplasmic reticulum (ER) and mitochondria were observed. TEM analysis also revealed no harmful effects on the cells, such as apoptotic or necrotic bodies or cell lysis. These findings indicate that the nano-HA/β-TCP composite demonstrates in vitro biocompatibility and interacts appropriately with BM-MSCs, including incorporation into the cell cytoplasm. In vivo, the Blue Bone^® group exhibited superior bone formation when compared with the other groups. Full article

The development of efficient and stable catalysts for ethanol steam reforming (ESR) is critical for sustainable hydrogen production. In this study, a series of Ni–Cu bimetallic catalysts supported on Gadolinium-doped ceria (GDC) were synthesized via the wet impregnation method to evaluate their performance in ESR. The catalysts were characterized by BET, XRD, SEM-EDS, H₂-TPR, and H₂ chemisorption to correlate their physicochemical properties with catalytic activity. Experimental results demonstrate that the incorporation of a small amount of Cu into the Ni/GDC system significantly enhances the resistance to carbon deposition without compromising hydrogen production rates. Among the formulations tested, 7.5%Ni-2.5%Cu/GDC exhibited superior catalytic stability at 700 °C. H₂-TPR analysis revealed that the presence of Cu facilitates the reduction of nickel species through a synergistic effect, while the GDC support provides high oxygen mobility, which promotes the gasification of surface carbonaceous species. This study provides valuable insights into the design of Ni–Cu bimetallic catalysts for mitigating coking and sintering in ESR processes, offering a robust catalyst formulation for industrial-scale hydrogen generation. Full article

The effects of ultraviolet (UV) light and moisture environments on the properties of continuous fiber-reinforced thermoplastic composites were investigated in this study. Materials included carbon fiber-reinforced polyphenylene sulfide (CF/PPS), glass fiber-reinforced polyphenylene sulfide (GF/PPS), glass fiber-reinforced polypropylene (GF/PP), and glass fiber-reinforced polyethylene terephthalate (GF/PET). Fiber orientation was noted to affect the response of the materials to UV and moisture environments. For CF/PPS, UV exposure led to enhanced unidirectional tensile and flexure properties, and quasi-isotropic compression strength, but reduced in-plane shear properties of cross-ply laminates and the short-beam shear strength of unidirectional laminates. Exposure to moisture had minimal effect on CF/PPS laminates. UV light caused a slight decrease in tensile strength and strain of unidirectional samples of GF/PPS and a slight increase in these properties with various degrees in quasi-isotropic samples. Exposure to moisture was noted to cause a reduction in most of the mechanical properties with various degrees in unidirectional and quasi-isotropic GF/PPS laminates. For GF/PP, exposure to UV and moisture decreased the tensile and compressive strengths of unidirectional and quasi-isotropic laminates. However, a notable increase in flexure strength was observed in both laminates after UV exposure. The GF/PET quasi-isotropic laminates showed reduced tension, compression, and flexure strengths but increased impact resistance and short-beam strength under UV exposure, while moisture decreased in-plane shear properties of cross-ply laminates and increased the glass transition temperature of unidirectional laminates. Vertical burn and surface flammability and smoke generation tests showed high flame resistance of CF/PPS and GF/PPS composites, and less so for GF/PP and GF/PET composites. The findings highlight the various responses of the materials to extreme environments. Full article

Hybrid composites combining natural and synthetic fibers have emerged as promising materials for lightweight ballistic protection systems due to their ability to balance mechanical performance, energy absorption, and sustainability. This study investigates the influence of stacking sequence on the ballistic response of epoxy hybrid composites reinforced with raffia and carbon woven fabrics subjected to 9 mm projectile impact. Four stacking-sequence configurations were investigated: alternating laminates (R₂C₂)₃ and (C₂R₂)₃, and block laminates R₆C₆ and C₆R₆, all containing identical reinforcement contents. Ballistic response was evaluated through impact and residual velocities, velocity reduction, absorbed energy, energy absorption efficiency, momentum reduction, and Doppler radar velocity profiles. All laminates were completely perforated but maintained their structural integrity after impact, without catastrophic fragmentation. The results showed that architectures with carbon fiber layers positioned at the impact face, namely (C₂R₂)₃ and C₆R₆, exhibited the lowest residual velocities and the highest absorbed energies, reaching 136.8 J and 135.4 J, respectively. Energy absorption efficiencies ranged from 16.6% to 19.1%, indicating similar ballistic responses among all configurations. Statistical analysis revealed no significant differences among the investigated architectures (p > 0.05). Overall, the results indicate that the impact-face reinforcement exerts a secondary influence on ballistic response, whereas the total reinforcement content governs energy dissipation during projectile penetration. Full article

This study evaluated the effects of thermocycling and staining on the optical behavior, chemical stability, and surface morphology of three commercial dental composites manufactured using different polymerization protocols: a light-cured composite (Omnichroma, OMNI) and two digital light-processed (DLP) 3D-printed composites intended for permanent (SprintRay CROWN, SPRINT) and temporary (GC Temp PRINT, TEMP) clinical applications. Disc-shaped specimens were subjected to thermocycling (0, 5000, 10,000, and 30,000 cycles) and immersion in coffee, Coca-Cola, or red wine for 1 and 7 days. Color change (ΔE₀₀) and translucency parameter (TP) were determined spectrophotometrically, while Fourier-transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) were employed to assess the polymerization efficiency (expressed as the relative conversion index) and surface morphology, respectively. Thermocycling induced material-dependent changes in color stability and translucency. After 30,000 cycles, ΔE₀₀ values reached 2.77 ± 0.89 for OMNI, 0.74 ± 0.34 for SPRINT, and 3.30 ± 0.89 for TEMP. SPRINT maintained the highest TP values throughout the aging protocol, ranging from 26.09 ± 0.33 to 23.81 ± 1.93, whereas OMNI and TEMP exhibited lower TP values. The most favorable optical performance and the highest resistance to beverage-induced coloration were detected for SPRINT, whereas TEMP showed the greatest susceptibility to aging- and staining-induced optical degradation. Red wine and coffee produced substantially greater color changes and reductions in translucency than Coca-Cola. AFM analysis demonstrated progressive surface degradation and increased roughness following prolonged thermocycling, highlighting the significant influence of material composition and manufacturing protocol on the long-term optical stability of the investigated dental composites. Full article

Hybrid composite lattice structures have emerged as a promising approach for improving the impact resistance of lightweight aerospace components. This study investigates the influence of density gradient direction in metallic Body-Centred Cubic (BCC) lattice reinforcement on the bird strike response of a composite UAV leading-edge (LE) structure. Three lattice architectures, uniform, backward graded, and forward graded, were parametrically generated using Rhino/Grasshopper and integrated within a carbon-fiber-reinforced polyamide LE. The hybrid structures were analyzed using Abaqus/Explicit with a validated Smooth Particle Hydrodynamics (SPH) bird model (1 kg, 95 m/s). All configurations maintained nearly identical structural mass, enabling the influence of lattice density distribution on structural response to be isolated. The backward graded configuration promoted progressive plastic collapse, resulting in the highest lattice energy absorption, but also increased deformation and load transfer to the spar. In contrast, the forward graded configuration suppressed progressive collapse, confined deformation near the impact interface, and significantly reduced stress transmission to critical structural components. Peak displacement and spar energy transfer were reduced by approximately 95% and 90%, respectively, compared with the backward graded configuration. The results demonstrate that density gradient tailoring of metallic lattice reinforcement enhances the structural performance of hybrid composite lattice LE structures by improving load sharing, deformation control, and impact resistance without increasing structural mass. Full article

The paradigm of sustainable development, coupled with contemporary inclinations towards green construction, exerts a considerable effect on the evolution of environmentally benign building composites. The main aim of this study is to create geopolymer composites with improved physical and mechanical properties. An examination of the properties of a geopolymer composite (GS), using ground granulated blast furnace slag (GGBFS) and plant fibers, is presented in this paper. Sisal (SF) and flax (FF) fibers, along with their combination (SF + FF), were integrated into the slag at concentrations of 0%, 0.5%, 1.0%, 1.5%, and 2% by weight. Before use, plant fibers were treated with a 5% NaOH solution. The geopolymer composites (GC) underwent evaluation for their density, compressive and flexural strengths, and water absorption characteristics. Scanning electron microscopy was employed to examine the fracture characteristics of the GC. The compressive and flexural strengths of GC were improved by including 1% SF, FF, and their combination, 0.5% SF + 0.5% FF. Compressive strength increases were 11.5%, 8.6%, and 14.5%, while flexural strength increases were 17.4%, 13%, and 19.6%, respectively. Water absorption of GC with 1% SF, FF, and SF + FF decreased by 14.6%, 10.8%, and 20.4%, respectively. The apparent synergistic performance of hybrid sisal-flax reinforcement at a total fiber content of 1% was revealed. GCs at the fracture have a homogeneous rough structure with microcracks and accumulations of geopolymer reaction products. The matrix-plant fiber interface in GC is identified by a rounded region with elongated fibers, indicating the fiber’s performance under mechanical stress. The findings of this investigation suggest the feasibility of utilizing plant fibers in environmentally sound geopolymer construction composites. Full article

Breast reconstruction after mastectomy or trauma poses considerable clinical and aesthetic challenges that traditional methods, such as silicone implants and autologous tissue flaps, often insufficiently address. This review analyzes the evolution of biomaterials for breast and soft tissue reconstruction, encompassing conventional ECM-derived scaffolds and acellular dermal matrices, as well as advanced hybrid constructs, injectable smart hydrogels, functionalized biomaterials, and cell-integrated systems incorporating adipose-derived stem cells. Emerging fabrication technologies, including 3D bioprinting, electrospinning, and computational imaging-guided design, are examined for their ability to create patient-specific, vascularized scaffolds with adjustable mechanical and biological characteristics. This review analyzes the scientific basis of soft tissue regeneration, focusing on adipogenesis, angiogenesis, immunomodulation, and extracellular matrix remodeling. The paper further overviews the efficacy of both well-known and new biomaterials, providing a detailed discussion of the translational challenges associated with their clinical application. Despite the substantial recent advancements in the field, comprehensive regenerative breast reconstruction requires ongoing interdisciplinary collaboration and innovation to translate promising preclinical results into safe, effective, and accessible clinical solutions for patients. Full article

Dental composites are ceramic-reinforced polymers; however, their colour stability is crucial for clinical maintenance, as composite restorations are inherently susceptible to colour change over time. In this in vitro study, eighty standardised 3D-printed samples were fabricated, filled with one of two supra-nanospherical resin composites, divided according to two polishing protocols (standard and reduced), and immersed in black tea with or without sugar for 28 days, after which they were repolished. Colour measurements were performed using a spectrophotometer at baseline (T₁), after tea immersion (T₂), and after repolishing (T₃). Statistical analysis was performed using a three-way repeated-measures mixed ANOVA followed by a Bonferroni post hoc test. The colour outcomes were interpreted against the CIEDE2000 50:50% perceptibility threshold (PT₀₀ = 0.8) and acceptability threshold (AT₀₀ = 1.8). Given the constraints of this in vitro investigation, all specimens exhibited initial discolouration (ΔE₀₀1 = 5.85 ± 1.63) that exceeded the acceptability threshold. Following repolishing, overall discolouration was significantly reduced (5.64 ± 1.46), achieving a final recovery (ΔE₀₀3 of 0.92 ± 0.56) near the perceptibility threshold. Although Tokuyama PALFIQUE^® LX5 might have exhibited lower ΔE than Estelite^® Alpha, the choice of composite had no statistically significant impact. Conversely, polishing methods and sugar content significantly influenced the outcomes (p < 0.05). Specifically, the standard method consistently resulted in final residual colour differences below the perceptibility threshold (ΔE₀₀3 ≤ PT), whereas the reduced method resulted in values exceeding this threshold. Furthermore, exposure to sucrose resulted in significantly greater residual staining post-treatment compared to plain black tea. Within the limitations of this in vitro study, the findings suggest that while composite selection between similar supra-nanospherical resins does not significantly affect aesthetic longevity, the standard method effectively maintains final residual colour shifts within imperceptible clinical boundaries. Moreover, dietary sucrose may contribute to greater permanent residual staining after repolishing. Nonetheless, as these observations derive from an in vitro model lacking a natural salivary pellicle and biofilm, clinical in vivo validation is required before direct extrapolation to daily dental practice. Full article