In this study, the properties of functionally graded and non-graded hybrid nanocomposites were evaluated through hardness, tensile, three-point bending, and Izod impact tests. Four functionally graded samples with different silica nanoparticle concentrations across the thickness and one non-graded sample, all with a total nanosilica content of 6 wt% were fabricated in four layers using a hand lay-up technique. In addition, one sample without nanoparticles was also prepared. The results of the hardness tests conducted on the upper surface of the samples indicated that increasing the silica nanoparticles content led to higher hardness. Specifically, the average hardness of the top-surfaces of samples containing 3 wt% nanosilica was approximately 27% higher than that of the top-surfaces of samples containing 0 wt% nanosilica. Among the samples containing silica nanoparticles, Sample E (non-graded, homogeneous) exhibited the highest tensile strength and modulus, showing increases of 17% and 22%, respectively, compared with Sample D (3-0-0-3, functionally graded). In the three-point bending test, the flexural strength of sample B (3-2-1-0, functionally graded) loaded from the 3 wt% side, was 24.5% higher than that of sample A (0-1-2-3, functionally graded) loaded from the 0 wt% side. In the Izod impact test, samples with non-graded nanoparticle distribution demonstrated superior impact resistance relative to the functionally graded samples. Overall, the results confirm that nanoparticle distribution plays a critical role in composite performance. Non-graded silica nanoparticles dispersion enhances tensile, flexural, impact, and hardness properties, whereas stepwise grading may introduce interlayer mismatches that reduce overall performance.
This study investigates the FSW of AA6092 reinforced with 17.5% SiC p in T6 condition, focusing on the effect of TRS (1000 rpm to 1750 rpm) on the thermal profiles, force-torque behaviour, microstructure, and mechanical characteristics. The results reveal that peak temperature increases with TRS, reaching ∼487°C, while a reversal in temperature trend along the weld direction is observed at higher TRS. A distinct AS-RS asymmetry is noted, with higher temperatures consistently on the advancing side. Increasing TRS significantly reduced spindle torque (14.7 to 10.6 Nm) and axial force (9715 to 7126 N), indicating enhanced material softening. Microstructural analysis reveals particle fragmentation and grain refinement up to 1500 rpm, with minimum grain size of 9.16 µm and particle size of 6.86 µm, followed by coarsening at 1750 rpm. Tool wear debris (Fe-rich particles) and oxide-rich phases are observed at higher TRS. The welds exhibit a characteristic ‘W’-shaped hardness profile, with maximum hardness of 121 HV 0.1 at 1500 rpm. The highest tensile strength (358 MPa) and joint efficiency (87%) are achieved at this condition, while further increase in TRS leads to strength degradation (308 MPa). Fractographic analysis confirms predominantly ductile fracture with dimple features up to 1500 rpm, transitioning to mixed-mode fracture at 1750 rpm.
This study aims to investigate the influence of graphene nanoplatelet (GNP) content on the crystallization and melting behavior of polyamide 6 (PA6) nanocomposites produced via melt mixing and injection molding. Compositions containing 0.05 and 0.10 phr of GNP were prepared and characterized using differential scanning calorimetry (DSC), activation energy analysis through the Friedman isoconversional method, Sestak–Berggren–Sbirrazzuoli (SbC) kinetic modeling, and field emission scanning electron microscopy (FEG-SEM). The presence of GNP shifted crystallization to higher temperatures and reduced the activation energy for crystallization, confirming the nanofiller’s nucleating effect. Pseudo-Avrami and SbC modeling showed excellent agreement with experimental data, revealing that GNP modifies crystallization kinetics by reducing the Nakamura Kg index and altering the reaction orders for nucleation and growth. During melting, neat PA6 exhibited complex, multi-step behavior associated with its heterogeneous melting response, whereas the nanocomposites, particularly those with 0.10 phr GNP, exhibited smoother melting behavior and lower apparent kinetic barriers. These results suggest that GNP modifies the thermal history and crystallization/melting behaviour of PA6, although confirmation of specific crystalline phases or structural changes would require complementary techniques such as XRD or WAXD. SEM analysis showed GNP incorporation into the PA6 matrix with localized agglomeration. Overall, the incorporation of GNP alters the crystalline morphology, reduces kinetic barriers, and significantly affects the thermal behavior of PA6, providing valuable insight into processing optimization and the development of advanced PA6-based nanocomposites.
This study reports the development and ballistic evaluation of hybrid composite armour panels using plain-weave eucalyptus fabric and unidirectional dyneema (layer) in an epoxy matrix. Four configurations with different stacking ratios, plus a dyneema control, were made via compression moulding. Panels were tested using methodologies adapted from NIJ 0101.06 and BIS 17051:2018 standards against 9 mm × 19 FMJ projectile threat. Results show all samples recorded a back face signature (BFS) below the 44 mm threshold. The 30 eucalyptus +20 dyneema layer panel was most effective, reducing BFS by 31% (19.60 ± 3.76 mm) and depth of penetration (DOP) by 52% (9.02 ± 3.65 mm) compared to the dyneema control. Achieving this required a 42.6% reduction in areal density normalised incident energy ( E n o r m ), safely balancing required kinetic energy arrest with the structural mass needed to prevent blunt-force trauma. Instrument analysis (VSC 8000 HS, SEM, 3D-CT, FTIR, DSC) revealed a dual energy dissipation mechanism: eucalyptus layers cause projectile blunting and brittle shear fractures, while dyneema absorbs impact energy through thermal melting and chain yielding. Incorporating biomass up to 33.4%, these hybrid composites demonstrate effective ballistic performance and meet structural protection needs, laying a foundation for future hybrid/green armour advancements.
This study investigates the mechanical durability, time-dependent deformation, physicochemical stability, and thermal behaviour of recycled PLA–based composites reinforced with Canabo microfiber and crab-shell-derived chitosan nanoparticles fabricated for bone scaffold applications. Fatigue, creep, swelling–degradation, and thermogravimetric analyses were systematically conducted to evaluate the suitability of different composite formulations. The results demonstrate that hybrid reinforcement significantly enhances the functional performance of recycled PLA. Among all compositions, specimen C3 containing 40 vol.% microfiber and 3 vol.% chitosan nanoparticles exhibited superior fatigue resistance, recording fatigue lives of 25,169, 22,113, and 19,088 cycles at 25%, 50%, and 75% of UTS respectively, which is attributed to the optimal synergistic interaction between uniformly dispersed chitosan nanoparticles and microfibers that effectively bridge cracks, dissipate cyclic energy, and delay crack propagation. Specimen C3 also showed controlled swelling behaviour increasing from 11.63% to 16.03% and moderate degradation from 1.13% to 6.2% over 4 weeks, indicating a balanced hydrophilicity that supports gradual degradation while maintaining structural integrity, which is desirable for bone tissue regeneration. In contrast, specimen C4 with 5 vol.% chitosan nanoparticles exhibited the lowest creep strain values of 0.0064, 0.0073, and 0.0091 at 5000 s, 10,000 s, and 15,000 s respectively, due to increased stiffness and stronger restriction of polymer chain mobility under sustained loading. Specimen C4 also showed the highest thermal stability with a maximum degradation temperature of 321°C in TGA, attributed to higher filler content and enhanced char formation that delays thermal decomposition. Overall, the results confirm that controlled chitosan loading plays a crucial role in tailoring the mechanical durability, degradation behaviour, and thermal stability of recycled PLA composites for advanced bone scaffold applications.
Ti 3 AlC 2 /TiAl 3 composite has shown great potential for the lightweight high-temperature structural materials. Studying its high-temperature mechanical properties and revealing its high-temperature strengthening mechanisms is a highly challenging task. In this work, Ti 3 AlC 2 enhanced TiAl 3 matrix composites with different reinforcements mass fractions were successfully prepared at 1300°C by powder metallurgy route. Then, the high-temperature compressive properties of the composites were tested, and the macroscopic and microscopic structural morphologies of the compressed specimens were characterized. The results indicate that the high-temperature compressive properties of Ti 3 AlC 2 /TiAl 3 composites exhibit negative temperature sensitivity and positive strain rate sensitivity. At 900°C, the compressive peak stress of the 10-40Ti 3 AlC 2 /TiAl 3 composites is 16.6-41.3% higher than that of TiAl 3 matrix, indicating a significant strengthening effect. The pinning effect of Ti 3 AlC 2 particles on dislocations and grain boundaries, as well as the good interfacial bonding between Ti 3 AlC 2 particles and the TiAl 3 matrix, are the main reasons for improving the high-temperature compressive strength of Ti 3 AlC 2 /TiAl 3 composites.
The load-bearing performance of bolted joints in open-hole CFRP laminates is critical to the structural integrity of composite assemblies. However, existing studies typically investigate the independent contribution of laminate and bolt, neglecting their coupled interaction and resulting in conservative predictions. This study aims to systematically investigate the influence of joint type and bolt size on the coupled load-bearing mechanical properties and failure modes of CFRP bolted joints. Single-lap and double-shear bolted joint configurations with various bolt sizes were examined through quasi-static tensile tests and nonlinear finite element analysis to obtain load-displacement curves, characterize mechanical properties and identify damage evolution as well as failure modes. The results indicate that the double-shear bolted joint exhibits higher ultimate load and failure displacement than the single-lap one. A transition in failure mechanism is observed for the M3 bolted joint. The failure mode shifts from brittle bolt fracture in single-lap configurations to bolt bending accompanied by fiber extrusion in double-shear configurations, effectively delaying bolt failure. Mechanical properties show a non-monotonic dependence on bolt size, initially increasing and then decreasing. The optimal bolt size differs between configurations. M6 maximizes ultimate load, initial stiffness, and bearing stiffness in single-lap joints, whereas in double-shear joints, the ultimate load peaks at M5 and failure displacement at M6. Matrix damage dominates in all cases, and the failure location progressively shifts from the hole edge to the laminate sides with increasing bolt size, a trend accelerated in double-shear configurations.
Thermal cycling is a hazardous condition that satellites in low Earth orbit (LEO) are regularly exposed to, as it causes the development of thermal stress in materials with non-zero coefficients of thermal expansion (CTE). Tubular braided composites (TBCs) combine high strength fibers with polymer matrices into a cylindrical structure suitable for load bearing applications. Their high customizability can allow for the creation of TBCs with near zero CTEs. In the author’s prior investigation, the effects of low amounts of thermal cycling on the mechanical performance of Kevlar®/Epoxy TBCs was investigated to assess the viability of these materials in satellite structures. In this work, scanning electron microscopy (SEM) was used to analyze the surfaces of Kevlar®/Epoxy TBCs exposed to thermal cycling to identify signs of material degradation. Samples were manufactured with one of three braid angles (35°,45°, and 55°) and exposed to 0, 5, or 10 thermal cycles between −50℃ and 120℃. Images of the samples were then taken using scanning electron microscopy and then digitally filtered to improve visibility of damage, which included microcracking, fiber-matrix debonding, and fiber breakage. At five cycles of exposure, samples manufactured at 35 and 55 degrees began to display signs of degradation, while the 45 degree samples did not. At 10 cycles of exposure, samples at all three braid angles displayed an increased presence of material damage. The development of thermally induced damage may be prevented through varying the material components or the introduction of nanoparticles to the epoxy resin.
Carbon fiber reinforced polymer (CFRP) composites are widely used in aerospace and other high-end equipment fields. However, they are prone to damage accumulation under the coupled effect of thermal-oxidative environments and cyclic loading. Currently, in-situ three-dimensional damage studies on CNT-ZnO synergistically modified composites under this coupled condition remain limited. In this work, CNT-ZnO/CFRP composites were fabricated via the VARTM process. The samples were subjected to thermal oxidation treatments at room temperature, 120°C, and 180°C, respectively. In-situ X-ray CT cyclic tensile tests combined with SEM characterization were performed to systematically investigate the effect of thermal-oxidative aging temperature on the cyclic tensile damage behavior of the composites. The results show that at room temperature, CNT-ZnO effectively inhibits the initiation and propagation of micro-damage in the composites under cyclic loading through crack bridging and interfacial strengthening mechanisms. Thermal oxidation at 120°C causes preliminary matrix degradation and weakening of interfacial properties, reduces the damage initiation threshold, significantly advances the occurrence of various damages, and weakens the strengthening effect of the modified system. High-temperature thermal oxidation at 180°C leads to severe damage to the matrix crosslinking structure and complete interfacial failure. Large-scale oxidation defects exist in the initial state of the material, the damage evolution process during cyclic loading is greatly advanced, and the effect of the modified system diminished drastically.
This study presents an experimental and predictive investigation of solid-particle erosion wear in interlaced E-glass/Carbon hybrid polymer composites. Hybrid polymer composites were fabricated through vacuum-assisted resin transfer moulding followed by autoclave curing, and their solid particle erosion behaviour was systematically evaluated under different operating conditions using a Taguchi L16 orthogonal array. Key process parameters, including impact velocity, impingement angle, and laminate layer configuration, were systematically varied during the erosion experiments. Analysis of variance showed that impact velocity was the primary factor influencing erosion wear, primarily due to increased kinetic energy and intensified micro-cutting mechanisms, followed by impingement angle and laminate layer configuration. SEM microstructural examination revealed severe matrix degradation, exposed reinforcement fibers, interfacial debonding, and irregular debris formation under aggressive erosive environments. To establish an accurate predictive framework, metaheuristic optimization techniques were used to tune the machine learning model parameters. Among the proposed predictive models, the Jaya-optimized Gradient Boosting framework demonstrated superior agreement with the experimental results, achieving a test R 2 of 0.9750 and a minimum MSE of 8.27 × 10 −10 . The excellent agreement between experimental measurements and predicted results validates the effectiveness of the proposed framework for accurate erosion wear prediction of hybrid polymer composites.
The incompatibility between a hydrophilic lignocellulosic fiber and a hydrophobic polymer matrix is always one of the major challenges in the development of lignocellulosic polymer composites. In this study, oil palm empty fruit bunch (EFB) fiber was chemically treated using three different anhydrides, i.e., maleic anhydride (MAh), itaconic anhydride (IAh), and succinic anhydride (SAh). Treated fiber (20%) was added to PLA to study the effects of anhydride type, concentration, and hydroquinone addition (for MAh and IAh) on composite properties. The results showed that the composites made of MAh and IAh treated EFB exhibited a better flexural property as compared to SAh treated EFB. The mechanical properties of the composites were further enhanced by preventing premature polymerization of C = C bonds from the MAh and IAh treated EFB. However, the impact strength was affected, which may be due to an increase in the composite stiffness, while SAh showed an improvement in the sudden energy absorption. Morphology studies had shown the treatments had improved fiber dispersion and interfacial adhesion in the composites. Overall, MAh and IAh treated EFB, especially with hydroquinone, had significantly improved the mechanical and interfacial properties of PLA/EFB composites, whereas SAh treatment resulted in more balanced enhancements.
Flax fiber is a renewable, biodegradable material with favorable mechanical properties and a low environmental footprint, making it a promising reinforcement for sustainable composite. In this study, waste flax fibers were processed into eco-friendly needle-punched nonwovens for automotive interior applications. The nonwovens were subsequently impregnated with waterborne polyurethane (WPU) at 10, 20, and 30 wt.%, dried at 120°C, and calendared under a pressure of 5 kN. The resulting materials were characterized in terms of their physical, morphological, mechanical and thermal properties. The results showed that flax nonwovens containing 20 wt.% or more WPU exhibited improved maximum tensile force compared with the untreated nonwoven. FTIR and SEM analyses confirmed WPU deposition on the flax fibers and indicated enhanced fiber-polymer interactions. Moreover, abrasion testing revealed a substantial improvement in wear resistance with increasing WPU content. While the untreated flax nonwoven failed before 10 000 Martindale cycles, the sample coated with 30 wt% WPU withstood 50,000 cycles with a mass loss of 12.67%, indicating its suitability for demanding automotive interior applications. In addition, WPU treatment reduced the water absorption of the flax nonwoven from 35% to 14.75% and increased the water contact angle from 53° for the untreated material to 122°, 127°, and 129.3° for the WPU-coated samples, demonstrating enhanced surface hydrophobicity. The WPU coating also enhanced the thermal stability and fire resistance of the flax nonwovens. Overall, the developed WPU-coated flax nonwovens exhibited improved durability, hydrophobicity, thermal performance, and flame resistance, highlighting their potential as sustainable materials for automotive interior applications.
This study analyses the buckling and material failure behaviour of thermoplastic composite pipes subjected to combined mechanical (internal and external pressures, bending moment and axial compression) and thermal loads, typical of deepwater offshore operational applications. Numerical simulations were conducted using temperature-dependent material properties for AS4/APC-2 carbon/PEEK laminates and APC-2 PEEK liners, to evaluate the effect of thermal gradient. Findings indicated that increasing internal pipe surface temperatures intensifies thermal gradients and reduces buckling and material failure resistance, with the inner liner being the most affected due to its proximity to elevated temperatures. The failure mode changes from buckling to material failure, driven by the plastic yielding of the inner liner, at approximately 70°C. Design strategies incorporating robust insulation, material and geometry optimisation as well as thermal management are proposed to enhance the structural integrity of the TCPs in deepwater operating conditions.
The development of sustainable self-sensing composites remains limited by the lack of recyclable polymer matrices reinforced with natural fibers that can simultaneously deliver adequate mechanical performance and reliable electrical functionality. Currently, a significant understanding of the mechanical behavior of fiber-reinforced composite structures, but an important gap in knowledge remains in the way Cu nanoparticles influence the electromechanical performance of thermoplastic elastomer/sisal composites. Consequently, this work aims to bridge the gap in understanding the effect of Cu nanoparticles on the electrical conductivity and piezo-resistive behavior of these composite materials. Sandwich laminates were manufactured using thermoplastic elastomer as matrix and sisal fibers coated with copper nanoparticles whose molar concentrations ranged from 0.2 to 0.8 M. The test specimens were tested via FTIR, scanning electron microscopy, and electromechanical tensile tests to evaluate piezo-resistive behavior. The microscopic observations showed that the 0.8 M test sample had an even nanoparticle distribution as well as better interlocking. The Young’s modulus reached 0.59 GPa, while 9.64 MPa for tensile strength. Also, electrical conductivity increased proportionally with molarity reching its higher value at 0.8 M (5.30 × 10 −1 S.m −1 ). These findings demonstrate that combining Cu nanoparticle-functionalized sisal fibers with a recyclable thermoplastic elastomer matrix constitutes a promising strategy for developing eco-friendly multifunctional composites for smart sensing applications within a circular economy framework.
Needle-punched carbon/carbon (NP C/C) composites are widely used in rocket-engine nozzles and re-entry vehicles for their high strength, low weight, and thermal stability. Due to cost considerations and strategic defense requirements, the launch and recovery of marine platforms have gradually developed. This study experimentally investigates the combined effects of saltwater immersion and ablation on reusable NP C/C composites. Saltwater introduces chloride ions and salt crystals into the porous matrix, promoting the development of microcracks and increasing porosity. Compressive properties degrade significantly due to fiber-matrix debonding and interface weakening, while increased fracture strain indicates damage accumulation. The chemical corrosion mechanism preferentially damages the fiber/matrix interface, leading to rapid deterioration of strength and modulus. The findings reveal a synergistic degradation mechanism driven by physical and chemical corrosion processes, emphasizing the urgent need for enhanced protective strategies to ensure the long-term reliability of NP C/C composites in harsh marine and aerospace environments.
Advanced grid-stiffened (AGS) composite structures are widely used in aerospace engineering due to their excellent specific strength and high damage tolerance. Previous studies have predominantly focused on the optimization of grid stiffener configurations, while the effects of skin layup schemes on structural performance have received comparatively little attention. This study systematically investigates the influence of skin layup strategies, namely the novel Double-Double (DD) and conventional Legacy Quad Laminate (LQL) methods, on the buckling and failure behaviors of three representative AGS structures. Both experimental tests and numerical simulations are conducted to investigate the buckling and post-buckling failure behaviors of AGS structures. The results indicate that DD layup offers significant advantages in improving axial stiffness, while the grid layout has more effects on the failure strength of the structures. These findings show that skin layup schemes and grid layout configurations jointly affect the mechanical performance of AGS structures and should be considered together in their optimal design.
This study investigates low-velocity impact damage in quasi-isotropic Glass Fibre Reinforced Polymer (GFRP) composites subjected to both normal and oblique impact loading using Local Defect Resonance (LDR)-based low-power vibro-thermography. The GFRP laminates were fabricated using the Vacuum Assisted Resin Transfer Moulding (VARTM) process. The specimens were impacted using a portable spring energy based in-house developed low velocity impact testing macine. Low-velocity impacts were introduced by varying the spring compression (10, 15, 20, and 25 mm), base plate angle (0° and 15°) and impactor body orientation (45°, 90°, 135°, and 180°), simulating real-life non-vertical impact conditions. These tests produced visible, barely visible and invisible impact damage on the sample. Damage characterization was initially performed using Phased Array Ultrasonic Testing (PAUT) to evaluate defect size, shape, and depth. Subsequently, Local Defect Resonance (LDR) based low power vibro-thermography (LVT) was performed using wideband excitation, and thermal responses were recorded with an uncooled infrared camera to obtain frequency specific defect mapping. A comparative evaluation demonstrated that LDR-LVT is more effective in detecting physical delamination and provides significantly faster inspection than PAUT for impact damage assessment. The results demonstrate the strong potential of LDR-LVT as a rapid and reliable non-destructive evaluation technique for impact-induced damage in composite structures. Furthermore, the experimental observations indicate that, below a threshold impact energy of approximately 8 Joule, the induced damage remains confined closer to the impacted surface.
The mechanical performance of textile composite materials strongly depends on the architecture of the reinforcement, particularly in complex structures such as 2.5D interlock fabrics. While numerous optimization approaches have been developed for composite materials, most studies focus on parameter optimization within predefined architectures, such as laminate stacking sequences, fiber orientations, or structural layouts. The topology of textile reinforcement architectures themselves is rarely considered as a design variable. This work introduces a topology-driven optimization framework for 2.5D interlock composite architectures in which the textile architecture itself is optimized. The interlock reinforcement is represented using a motif-based discretization of the representative volume element (RVE), allowing the architecture to be described through a compact topology matrix. Geometric consistency rules derived from interlock construction principles are applied to ensure the validity of the generated architectures. The mechanical response of each candidate architecture is then evaluated through a micromechanical stiffness prediction model based on the Chamis formulation, enabling the computation of the effective stiffness matrix of the composite. The proposed framework is intended as a computational design and screening tool for identifying manufacturable textile architectures prior to high-fidelity numerical or experimental validation. This framework enables the systematic exploration of admissible textile architectures and the identification of configurations capable of achieving targeted stiffness characteristics. The results demonstrate that treating the textile architecture as a topological design variable provides a new pathway for the optimization of textile composite materials.
A four-order “orientation-clustering-stiffness-damage” coupling framework is proposed for 28–30 vol% carbon-fiber/epoxy short-fiber composites (7 μm nominal fiber diameter, 3–5 mm chopped length), enabling accurate cross-scale failure prediction spanning from 60 μm single-fiber interfacial debonding regions up to 300 μm component-level representative volume elements that cover the full statistical distribution of fiber orientation and spatial arrangement. Twenty-one 30 × 30 × 30 mm 3 cubic specimens were in-situ imaged under quasi-static loading via synchrotron radiation Micro-CT at 0.5 μm voxel spacing, delivering approximately 1 μm effective spatial resolution after standard modulation transfer function deconvolution and ring-artifact suppression processing. The tomographic finite-element analysis workflow was fully synchronized to a pre-calibrated six-channel acoustic-emission array with 120 dB gain and 100 kHz–1 MHz bandwidth, where 15 specimens were exclusively used for multi-parameter model calibration through a genetic algorithm optimization loop, while the remaining six completely independent specimens were adopted for rigorous blind validation under uniaxial tension, biaxial compression and in-plane shear loading conditions. This framework achieves a tensile modulus prediction error below 5% and over 92% acoustic-emission hit event agreement on the fully unseen validation dataset, which significantly outperforms conventional Mori-Tanaka mean-field homogenization and periodic representative-volume-element homogenization methods by reducing prediction deviation by more than 40%. By embedding high-order orientation tensors, statistical fiber clustering spectral descriptors and gradient-sensitive non-local damage variables into a single physically interpretable constitutive kernel, the framework delivers an experimentally calibratable, highly scalable and transferable modeling paradigm, holding great practical application potential for composite process reverse design in aerospace and automotive lightweighting industries.
Natural fiber-reinforced polymer composites offer a sustainable alternative for non-structural construction applications, including partition panels and lightweight cladding systems. However, the hydrophilic nature of natural fibers limits their interfacial bonding with polymer matrices, reducing the overall efficiency of the composite. In this study, Guadua angustifolia bamboo fibers were surface-modified prior to composite fabrication using alkali treatment (NaOH solutions) and dry-etching plasma treatment, and their influence on fiber–matrix interfacial mechanics was systematically investigated. Single-fiber pull-out tests were performed to quantitatively determine the interfacial shear strength (IFSS) and analyze debonding mechanisms in polyester-based composites. Plasma-treated fibers exhibited the highest IFSS (34.46 MPa), followed by alkali-treated fibers (25.15 MPa) and untreated fibers (12.60 MPa). Distinct debonding responses were identified: plasma-treated fibers showed stable and progressive debonding associated with enhanced stress-transfer efficiency, whereas alkali-treated fibers displayed a partially stable response, reflecting intermediate adhesion conditions. Macroscopic tensile and bending tests demonstrated that improvements in IFSS were consistent with enhanced composite strength and stiffness, although excessive alkali concentration led to diminished reinforcement efficiency. Scanning electron microscopy (SEM) of fracture surfaces corroborated the pull-out results, revealing increased matrix adherence and reduced fiber pull-out in plasma-treated specimens. The results demonstrate that controlled surface engineering directly regulates interfacial shear performance and debonding stability, providing mechanistic insight into interface optimization in bamboo fiber-reinforced polymer composites.
