Fibers

24 pages, 8070 KB

Open AccessArticle

Structural Performance of Columns with Glass Fiber-Reinforced Polymer Bars Under Axial Compression

by Trupti Amit Kinjawadekar, Shantharam Patil and Gopinatha Nayak

Fibers 2025, 13(11), 156; https://doi.org/10.3390/fib13110156 - 20 Nov 2025

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Corrosion continues to be a major challenge affecting the service life, safety and durability of steel-reinforced concrete (RC) structures. The deterioration of steel not only reduces structural capacity but also increases long-term maintenance costs. To address this limitation, glass fiber-reinforced polymer (GFRP) is [...] Read more.

Corrosion continues to be a major challenge affecting the service life, safety and durability of steel-reinforced concrete (RC) structures. The deterioration of steel not only reduces structural capacity but also increases long-term maintenance costs. To address this limitation, glass fiber-reinforced polymer (GFRP) is being investigated as an alternative to conventional steel reinforcement, particularly in aggressive environments. This work examines the behavior of composite columns reinforced with GFRP bars with steel stirrups. Sixteen square columns of 150 × 150 × 850 mm dimensions, cast with M30 grade concrete, were reinforced using either GFRP or steel, while varying stirrup spacing and bar diameters. Experimental observations showed that GFRP reinforcement contributed about 10–12% of the ultimate capacity of the columns. A marked enhancement in load carrying capacity of GFRP-RC columns was obtained with closer stirrup spacing. The axial strength of GFRP-reinforced columns was comparable to steel-reinforced ones with the same main reinforcement ratio. Ductility increased by 12% when stirrup spacing was reduced. The difference between analytical and experimental values ranged between 12% and 15%, whereas experimental and numerical results differed by 10–12%. Based on these results, a modification factor derived from IS 456:2000 is proposed for predicting the capacity of ‘GFRP-reinforced’ columns. The outcomes clearly highlight the potential of GFRP reinforcement as a durable, sustainable and practical substitute for conventional steel reinforcement. Full article

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28 pages, 2327 KB

Open AccessReview

Industrial Hemp as Precursor for Sustainable Bioproducts: Recent Trends and Prospects

by Sodiq Babatunde Yusuf, Nnaemeka Ewurum, Harrison Appiah and Jovale Vincent Tongco

Fibers 2025, 13(11), 155; https://doi.org/10.3390/fib13110155 - 20 Nov 2025

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Abstract

The generation of over 150 million tons of hemp waste annually is as much of a sustainability challenge as it is an opportunity for the circular bioeconomy. This review provides a critical analysis of the recent trends in the use of industrial hemp [...] Read more.

The generation of over 150 million tons of hemp waste annually is as much of a sustainability challenge as it is an opportunity for the circular bioeconomy. This review provides a critical analysis of the recent trends in the use of industrial hemp waste as a precursor to producing sustainable bioproducts. The objective is to synthesize the current state of knowledge and to identify the various pathways for valorizing hemp waste beyond the traditional applications. The methodology involved the systematic assessment of the recent literature to identify the applications in textiles, biocomposites, packaging, and, most importantly, advanced areas such as hemp-based carbon materials for storing energy, biomedical materials, and smart biomaterials. Findings showed that hemp waste is a versatile material for creating high-value products, as it shows promise in carbon electrodes for supercapacitors as well as reinforcement for 3D-printed biocomposites. However, there are some limitations in terms of standardization and scalability. The review concludes that future progress depends on multidisciplinary research to optimize conversion and utilization processes, including the development of comprehensive life-cycle assessments and reliable supply chains. Full article

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25 pages, 8929 KB

Open AccessArticle

Experimental Evaluation of RC Structures with Brick Infills for Vertical Forest Adaptation in Seismic Regions

by Theodoros Rousakis, Vachan Vanian, Martha Lappa, Adamantis G. Zapris, Ioannis P. Xynopoulos, Maristella Voutetaki, Stefanos Kellis, George Sapidis, Maria Naoum, Nikos Papadopoulos, Violetta K. Kytinou, Martha Karabini, Constantin E. Chalioris, Athanasia K. Thomoglou and Emmanouil Golias

Fibers 2025, 13(11), 154; https://doi.org/10.3390/fib13110154 - 17 Nov 2025

Cited by 1 | Viewed by 427

Abstract

Existing Mediterranean reinforced concrete buildings with masonry infills exhibit critical seismic vulnerabilities, yet real-time damage detection capabilities remain limited. This study validates a novel dense piezoelectric transducer (PZT) network concept for early damage detection in deficient RC structures under progressive seismic loading. A [...] Read more.

Existing Mediterranean reinforced concrete buildings with masonry infills exhibit critical seismic vulnerabilities, yet real-time damage detection capabilities remain limited. This study validates a novel dense piezoelectric transducer (PZT) network concept for early damage detection in deficient RC structures under progressive seismic loading. A three-dimensional single-story RC frame with brick infills, representative of pre-Eurocode Mediterranean construction (non-ductile detailing, inadequate transverse reinforcement), was tested at serviceability limit states (SLSs) (Phase A) using a dynamic pushover approach with the 1978 Thessaloniki earthquake record, progressively scaled from EQ0.1g to EQ1.1g within the GREENERGY vertical forest renovation project. The specimen featured 48 PZTs using electromechanical impedance (EMI) methodology, 12 accelerometers, 8 displacement sensors, and 20 strain gauges. Progressive infill deterioration initiated at EQ0.5g while steel reinforcement remained elastic (max 2350 μstrain < 2890 μstrain yield). Maximum inter-story drift reached 11.37‰ with negligible residual drift (0.204‰). The PZT network, analyzed through Root Mean Square Deviation (RMSD), successfully detected internal cracking and infill-frame debonding before visible manifestation, validating its early warning capability. Floor acceleration amplification increased from 1.26 to 1.57, quantifying structural stiffness degradation. These SLS results provide critical baseline data enabling the Phase B implementation of sustainable vertical forest retrofitting strategies for aging Mediterranean building stock. Full article

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14 pages, 1023 KB

Open AccessArticle

Study of the Physical and Chemical Properties of Banana Peduncle Fibers of the Cultivar “William Cavendish”: Influence of Extraction Techniques

by Solange Mélanie Anafack, Paul William Mejouyo Huisken, Jean-Yves Drean, Omar Harzallah, Rodrigue Nicodème Sikame Tagne, Hermann Tamaguelon Dzoujo, Murugesh Babu and Ebenezer Njeugna

Fibers 2025, 13(11), 153; https://doi.org/10.3390/fib13110153 - 17 Nov 2025

Viewed by 687

Abstract

This study deals with the physical, chemical, and thermal properties of William banana peduncle fibers in order to consider the possibility of using these new fibers in textile applications. The samples were collected in Cameroon, in the Littoral region, Njombe Penja district (agri-food [...] Read more.

This study deals with the physical, chemical, and thermal properties of William banana peduncle fibers in order to consider the possibility of using these new fibers in textile applications. The samples were collected in Cameroon, in the Littoral region, Njombe Penja district (agri-food industry). The fibers were extracted by three methods, including Water Retting (WR), Dew Retting (DR), and Mechanical Extraction (ME). The various resulting fibers were characterized by X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA), Fourier-Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM), respectively. The FTIR analysis confirmed the lignocellulosic structure of the fibers and revealed that the three extraction methods had not affected the chemical nature of the fibers. The extraction methods also had no significant impact on density and moisture content. Scanning electron microscopy showed bands of fibers bundles on all samples. Thermogravimetric analysis (TGA) showed that the fibers extracted were thermally stable at 82 °C. X-ray diffraction (XRD) analysis showed crystallinity levels ranging from 58.24% for (WR), 54.83% for (DR), and 69.53% for (ME). The results obtained on the chemical composition show that the extracted fibers consist mainly of 71.8%, 73.6%, and 74.8% cellulose for WR, DR, and ME, respectively, making them suitable for textile applications. Full article

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29 pages, 11420 KB

Open AccessArticle

FRESCO: An Open Database for Fiber and Polymer Strengthening of Infilled RC Frame Systems

by Vachan Vanian and Theodoros Rousakis

Fibers 2025, 13(11), 152; https://doi.org/10.3390/fib13110152 - 10 Nov 2025

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Abstract

This paper presents FRESCO (Fiber REinforced Strengthening COmposite Database), a comprehensive open-source database designed to systematically organize experimental data on infilled RC frame systems that can be strengthened with advanced composite materials, such as Fiber-Reinforced Polymers (FRP), Textile-Reinforced Mortars (TRM), and other fiber-based [...] Read more.

This paper presents FRESCO (Fiber REinforced Strengthening COmposite Database), a comprehensive open-source database designed to systematically organize experimental data on infilled RC frame systems that can be strengthened with advanced composite materials, such as Fiber-Reinforced Polymers (FRP), Textile-Reinforced Mortars (TRM), and other fiber-based solutions. The database employs open source practices while providing high-quality output that is fully compatible with leading commercial software packages such as ANSYS 2022R2. It uses Python3 as the main programming language and FreeCAD v1.0 as the model generation engine, with a systematic 13-section structure that ensures complete documentation of all parameters necessary for numerical modeling and validation of analytical methods. Two types of databases are provided: in comma-separated format (.csv) for common everyday interaction and in JSON format (.json) for easy programmatic access. The database features automated 3D modeling capabilities, converting experimental data into detailed finite element models with solid RC frame geometry, reinforcement details, and infill configurations. Validation through three comprehensive examples demonstrates that numerical models generated from the database closely match experimental results, with response curves that closely match the initial stiffness, the peak loading and the post-peak stiffness degradation phase across different loading conditions. The database focuses on RC frame systems with unreinforced brick infill. Reflecting the term FRESCO, which in Greek (φρέσκο) means “fresh”, the database is designed as a dynamic, evolving resource, with future versions planned to include RC walls and full buildings. Full article

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22 pages, 4710 KB

Open AccessArticle

Finite Element Modelling of Pultruded FRP Beam-to-Column Joints

by Jawed Qureshi and Karthick Murugan Mahendran

Fibers 2025, 13(11), 151; https://doi.org/10.3390/fib13110151 - 7 Nov 2025

Viewed by 806

Abstract

This research addresses the critical gap in accurately modelling pultruded fibre-reinforced polymer (FRP) beam-to-column joints, where previous studies largely ignored progressive damage mechanisms. A novel finite element framework is developed in ABAQUS, integrating Hashin’s failure criterion with fracture energy-based damage evolution to simulate [...] Read more.

This research addresses the critical gap in accurately modelling pultruded fibre-reinforced polymer (FRP) beam-to-column joints, where previous studies largely ignored progressive damage mechanisms. A novel finite element framework is developed in ABAQUS, integrating Hashin’s failure criterion with fracture energy-based damage evolution to simulate delamination and brittle failure in FRP cleats. The model is rigorously validated against full-scale experimental data, achieving close agreement in moment–rotation response, initial stiffness (within 5%), and ultimate moment capacity (variation < 10%). Quantitative results confirm that delamination at the fillet radius governs failure, while qualitative analysis reveals the sensitivity of stiffness to cleat geometry and bolt characteristics. A parametric study demonstrates that increasing cleat thickness and bolt diameter enhances stiffness up to 15%, whereas bolt–hole clearance introduces slip without significantly affecting strength. The validated FEM reduces reliance on costly physical testing and provides a robust tool for optimising FRP joint design, supporting the future development of design guidelines for pultruded FRP structures. Full article

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14 pages, 3406 KB

Open AccessArticle

Effect of Electron Radiation and Triallyl Isocyanurate on the Structure, Thermal, and Mechanical Properties of Epoxy Resin Filled with Dusty Fiber Fraction Derived from Recycled Wind Turbine Blades

by Rafał Malinowski, Danuta Matykiewicz, Volodymyr Krasinskyi, Urszula Gryczka and Daniel Kaczor

Fibers 2025, 13(11), 150; https://doi.org/10.3390/fib13110150 - 4 Nov 2025

Viewed by 502

Abstract

This paper presents the investigation of the effect of electron radiation or the combined action of this radiation and triallyl isocyanurate (TAIC) on the structural, thermal, and mechanical properties of epoxy resin filled with a fraction of dust fibers (DFs) from recycled wind [...] Read more.

This paper presents the investigation of the effect of electron radiation or the combined action of this radiation and triallyl isocyanurate (TAIC) on the structural, thermal, and mechanical properties of epoxy resin filled with a fraction of dust fibers (DFs) from recycled wind turbine blades. The resin containing 20 wt% of DF was irradiated with doses of 40, 80, 120, and 160 kGy. The results showed that electron radiation had only a slight effect on the properties of the studied composite, mainly on its glass transition temperature. More significant changes were observed with the combined action of radiation and TAIC. The main effect that occurred after the TAIC addition was the plasticization of the polymer matrix. With its participation, the glass transition temperature, thermal stability, and the hardness of the material and its flexural modulus were significantly reduced. The degree of change in these properties was regulated by the radiation dose. Furthermore, no significant changes in the composite structure were observed after radiation treatment, while the introduction of TAIC into the polymer matrix caused the formation of gas cells, probably due to the partial decomposition of TAIC. Full article

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19 pages, 981 KB

Open AccessReview

Molecular Self-Reassembled Regenerated Fibres and Their Significance in Tissue Engineering Bio-Composites

by Kristiyan Stiliyanov-Atanasov and Probal Basu

Fibers 2025, 13(11), 149; https://doi.org/10.3390/fib13110149 - 4 Nov 2025

Viewed by 831

Abstract

Due to their interesting physicochemical and bioactive properties, regenerated fibres (including cellulose and collagen regenerated fibres) have been considered attractive biomaterials for biomedical applications. These regenerated fibres have an altered molecular arrangement compared to the native fibres and exhibit unique properties. Despite their [...] Read more.

Due to their interesting physicochemical and bioactive properties, regenerated fibres (including cellulose and collagen regenerated fibres) have been considered attractive biomaterials for biomedical applications. These regenerated fibres have an altered molecular arrangement compared to the native fibres and exhibit unique properties. Despite their distinctive structural characteristics, a meagre amount of research explores their potential for the development of tissue-engineering bio-composites. This work focuses on exploring the promise of cellulose and collagen-based regenerated fibres in tissue-regeneration bio-composite development. Initially, the work investigates the similarities and dissimilarities between the collagen and cellulose structures, which are linked to their specific properties, such as crystallinity, chemical characteristics, and mechanical properties. It then delves deeper into their molecular structural reassembly and various aspects of the already reported bio-composites developed using them. Finally, their promise in the development of tissue-engineering bio-composites is explored through a meticulous comparative analysis of their advantages and challenges. It was found that efficient biodegradability is one of the key advantages of regenerated fibres, whereas difficulty in processing presents a significant disadvantage. Despite these facts, regenerated fibres can incorporate enhanced and desired properties into the bio-composite matrix, which could lead to tissue-specific bio-regenerative applications. Full article

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20 pages, 10833 KB

Open AccessArticle

Mechanical Performances of Natural Textiles for Eco-Friendly Composite Materials: A Comparative Assessment

by Gianfranco Stipo, Valerio Alecci, Mario De Stefano, Stefano Galassi, Maria Cristina Salvatici and Maria Luisa Satta

Fibers 2025, 13(11), 148; https://doi.org/10.3390/fib13110148 - 4 Nov 2025

Cited by 1 | Viewed by 916

Abstract

In the last decades, composite materials made of synthetic fibers embedded in organic or inorganic matrices have been successfully used for strengthening reinforced-concrete and masonry buildings. The scientific community is currently discussing the low sustainability of these materials and their environmental impact due [...] Read more.

In the last decades, composite materials made of synthetic fibers embedded in organic or inorganic matrices have been successfully used for strengthening reinforced-concrete and masonry buildings. The scientific community is currently discussing the low sustainability of these materials and their environmental impact due to the production process, the life cycle, and the generation of potentially harmful waste. In this context, the use of natural textiles represents a promising solution, alternative to conventional synthetic fibers, aimed at designing an innovative composite material obtained from renewable resources with no energy consumption and greatly reducing the impact of building activities on the environment. In this paper, an experimental assessment of ten different natural textiles is presented in order to compare their mechanical properties for possible use in innovative, eco-friendly composite materials. Mechanical tensile tests were performed on the ten different textiles before and after an all-natural protective treatment referred to as the “hornification” process. Treatment-induced changes in the fiber morphology were also analyzed using a scanning electron microscope (SEM), which provided high-resolution images of the surface and cross-sectional area of the fibers. Considering that the current demand for sustainable building materials capable of ensuring a greener future for the construction industry is on the rise, the promising results obtained in this study could be useful to the academic community and building industry. Full article

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35 pages, 12093 KB

Open AccessArticle

Numerical Evaluation of the Effective Thermo-Mechanical Properties of a Large-Scale Additively Manufactured Short Fiber-Reinforced Polymer Composite

by Aigbe E. Awenlimobor and Douglas E. Smith

Fibers 2025, 13(11), 147; https://doi.org/10.3390/fib13110147 - 30 Oct 2025

Viewed by 1129

Abstract

This study presents a finite element analysis (FEA)-based numerical homogenization method for evaluating the effective thermo-mechanical properties of a large-area additively manufactured particulate-filled composite using realistic periodic representative volume elements (RVEs) generated from reconstructed X-ray µ-CT image scans of a 3D-printed bead. The [...] Read more.

This study presents a finite element analysis (FEA)-based numerical homogenization method for evaluating the effective thermo-mechanical properties of a large-area additively manufactured particulate-filled composite using realistic periodic representative volume elements (RVEs) generated from reconstructed X-ray µ-CT image scans of a 3D-printed bead. The numerical results of the predicted effective properties, including the elastic stiffness, coefficient of thermal expansion (CTE) and thermal conductivity, were benchmarked with the Mori–Tanaka–Benveniste analytical estimates, which were found to be comparable. Initial sensitivity analysis using a single region of interest (ROI) extracted from the bead’s volume was performed to determine a suitable RVE size. The impact of inherent micro-porosities on the resulting composite material’s behavior was also quantified in the current investigation and was shown to reduce the composite’s effective properties. Using a suitable RVE size, the effect of anisotropy due to spatial variation in the microstructure across the bead specimen on the computed composite’s effective properties was also assessed. The results show that the regions closer to the exposed surface of the print bead with highly aligned and densely packed fiber particulates have superior properties as compared to inner regions with a more randomly oriented and less densely packed fibrous microstructure. Full article

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15 pages, 3178 KB

Open AccessArticle

Nonlinear Dual-Wavelength Switching of Ultrashort Pulses in Slightly Asymmetric Dual-Core Fibers

by Mattia Longobucco, Ignas Astrauskas, Audrius Pugžlys, Andrius Baltuška, Ryszard Buczyński and Ignác Bugár

Fibers 2025, 13(11), 146; https://doi.org/10.3390/fib13110146 - 30 Oct 2025

Viewed by 552

Abstract

We conducted a comprehensive experimental investigation of dual-wavelength switching of 1560 nm, 75 fs pulses (referred to as signal) driven by 1030 nm, 270 fs pulses (referred to as control) using two dual-core fibers with high refractive index contrast and different [...] Read more.

We conducted a comprehensive experimental investigation of dual-wavelength switching of 1560 nm, 75 fs pulses (referred to as signal) driven by 1030 nm, 270 fs pulses (referred to as control) using two dual-core fibers with high refractive index contrast and different levels of asymmetry. The study explores the influence of fiber length, control pulse energy, and control-signal pulse delay on switching performance. For the fiber with higher dual-core asymmetry, we achieved an exceptional switching contrast of 41.6 dB at a 14 mm fiber length, exhibiting a homogeneous character within the spectral range of 1450–1650 nm. In contrast, the study of the weaker dual-core asymmetry fiber revealed a maximum switching contrast of 10.7 dB at a 22 mm fiber length, albeit under lower control pulse energy. These observations confirm that the switching mechanism is based on the nonlinear balancing of dual-core asymmetry, wherein the control pulse induces an enhancement of the effective refractive index in the fast fiber core, facilitating the switching of the signal pulse. This work demonstrates high switching contrasts with only a 0.4–0.6 nJ control pulse energy requirement, providing experimental confirmation of a previously reported theoretical model. For the first time, the dual-wavelength switching performance of dual-core fibers with varying levels of asymmetry is compared. The results reveal key directions for the further development of dual-core fibers in view of their potential applications. Full article

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23 pages, 14077 KB

Open AccessArticle

Mitigating Out-of-Plane Fiber Waviness in AFP Laminates with Tow-Gaps via Selective Placement of Thermoplastic Veils

by Ahmadreza Ravangard, Kuthan Celebi, Sergii G. Kravchenko and Oleksandr G. Kravchenko

Fibers 2025, 13(11), 145; https://doi.org/10.3390/fib13110145 - 24 Oct 2025

Cited by 1 | Viewed by 2632

Abstract

Fiber tow-gaps and overlaps formed during the Automated Fiber Placement (AFP) process pose a significant challenge by introducing non-uniform composite morphologies, often characterized by resin-rich regions and fiber waviness. These defects occur as deposited fibers sink into the gap regions during consolidation, with [...] Read more.

Fiber tow-gaps and overlaps formed during the Automated Fiber Placement (AFP) process pose a significant challenge by introducing non-uniform composite morphologies, often characterized by resin-rich regions and fiber waviness. These defects occur as deposited fibers sink into the gap regions during consolidation, with gap geometry determined during path planning. Such morphological inconsistencies can compromise structural reliability by initiating premature failure, particularly through localized out-of-plane waviness and resin accumulation. This study investigates the integration of high melting temperature thermoplastic veils, specifically polyetherimide (PEI), into fiber tow-gaps as a method to prevent ply sinking and reduce fiber waviness on both internal and external surfaces of the laminate. The PEI veils also serve to reinforce resin-rich regions by forming an interpenetrated network of high fracture toughness material within the brittle epoxy matrix. Tensile tests conducted on cross-ply laminates containing staggered gaps demonstrated that the inclusion of PEI veils modified the failure mode. The results suggest that the selective placement of thermoplastic veils within tow-gaps during AFP offers a viable strategy to mitigate manufacturing-induced non-uniform morphologies. Full article

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14 pages, 4363 KB

Open AccessArticle

Impact of Cutting Direction in CAD/CAM FRC Blanks on the Shear Bond Strength of Veneering Composites

by Sven Räther, Franz Sebastian Schwindling, Akinori Tasaka, Peter Rammelsberg, Andreas Zenthöfer and Stefan Rues

Fibers 2025, 13(11), 144; https://doi.org/10.3390/fib13110144 - 22 Oct 2025

Viewed by 615

Abstract

Fiber-reinforced composites (FRCs) are increasingly utilized in computer-aided design/computer-aided Manufacturing (CAD/CAM) workflows for both definitive and provisional restorations. Veneering these materials is essential not only for achieving aesthetic outcomes, but also to prevent direct exposure of oral tissues to glass fibers. This study [...] Read more.

Fiber-reinforced composites (FRCs) are increasingly utilized in computer-aided design/computer-aided Manufacturing (CAD/CAM) workflows for both definitive and provisional restorations. Veneering these materials is essential not only for achieving aesthetic outcomes, but also to prevent direct exposure of oral tissues to glass fibers. This study evaluated the short- and long-term shear bond strength (SBS) between a veneering composite and FRC (Trinia, Bicon) with varying bonding interface orientations and load directions. Specimens were sectioned into discs with 1.5° or 45° tilt with respect to material’s layering planes and veneered with a composite pin (Ceramage, Shofu Inc.). SBS was tested after 24 h and 180 days of water storage, with forces applied either parallel or perpendicular to the layer orientation seen at the bonding interface. Long-term water storage significantly reduced SBS (24 h: 23.9 MPa vs. 180 d: 18.1 MPa, p < 0.001). In contrast, neither cutting direction (1.5° vs. 45°, p = 0.584) nor loading direction (parallel vs. perpendicular, p = 0.367) significantly influenced SBS. These results suggest veneering of the tested FRC material is clinically viable regardless of interface orientation or load direction. Although aging significantly reduced SBS, this was not clinically relevant, indicating that appropriate adhesive protocols may ensure durable bonding. Full article

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Fibers, Volume 13, Issue 11 (November 2025) – 13 articles

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