This study employed micro-arc oxidation (MAO) technology to modify magnesium alloy (MA) surfaces for enhancing bonding strength with carbon fiber reinforced polymer (CFRP). The MAO treatment created porous surface structures with improved hardness, roughness and wettability, and was combined with resin pre-coating (RPC) technology to facilitate high-viscosity epoxy infiltration into micro-pores. Using an MAO electrolyte system containing "20 g/L Na2SiO3 + 15 g/L KOH + 8 g/L KF" in conjunction with RPC modification achieved a bonding strength of 14.2 MPa, representing a 144.8% improvement over the baseline strength. The failure mode transitioned from MA interface debonding to predominant CFRP fiber tearing, demonstrating significant interfacial strength enhancement. This work exhibits MAO as an effective approach for improving MA-CFRP bonding strength, offering a promising strategy for industrial production of high-performance MA-CFRP composites.

Asphalt pavements in frozen regions are highly susceptible to damage induced by freeze-thaw cycles, during which microcracks initiate, propagate, and ultimately evolve into macrocracks. However, warm-mixed recycled asphalt mixtures (WRAMs) exhibit limited resistance to multi-stage fracture cracking. To address this limitation, basalt fibers (BFs) with various morphologies and dosages were incorporated into WRAMs to enhance their crack-resistance mechanisms. WRAM, chopped basalt fiber-reinforced WRAM (WR-CBF), and flocculent basalt fiber-reinforced WRAM (WR-FBF) were investigated under Mode I, Mode III, and mixed Mode I/III fracture modes. Specimens were subjected to 10 and 20 water and salt freeze-thaw cycles, followed by macroscopic edge-notched disk bend (ENDB) tests, mesoscopic acoustic emission (AE) analysis, and microscopic scanning electron microscopy (SEM) observations. The results indicate that WR-FBF with a basalt fiber content of 0.4% exhibits optimal crack resistance. Fracture resistance decreases with increasing freeze-thaw cycles, with salt freeze-thaw cycles causing more severe deterioration than water freeze-thaw cycles. Chopped basalt fiber provides more stable resistance to crack propagation across different fracture modes, whereas flocculent basalt fiber primarily enhances resistance to crack initiation, particularly under fracture mode I loading. SEM observations further indicate that FBFs enhance interfacial bonding and stress redistribution through adsorption, anchoring, three-dimensional network formation, and fiber pull-out mechanisms, thereby significantly improving the overall crack resistance of WRAMs.

This study aims at an optimum interface design against delamination in unidirectional carbon fiber-reinforced polymers (UD-CFRP) by incorporating ultra-thin micro-/nano- Aramid pulp (AP) interlayers with various AP lengths, volume densities, and thicknesses. Experimental results indicate that even reduction of interlayer thickness alone (while keeping other interleaving conditions unchanged) can significantly enhance the fracture toughness GIC by up to 190%. Nano-AP fibers primarily contribute to crack-bridging toughening, while micro-AP fibers facilitate fibre bridging across UD carbon fiber plies. SEM analysis reveals the key toughening mechanism of fibre bridging across the ply interface. These findings suggest that optimal AP interlayer properties (thickness, volume density, and fiber length) can be tailored for improved delamination resistance in CFRPs. AP-interleave toughening can be adopted in pre-preg manufacturing; therefore, this research methodology can potentially be transferred to industrial production for more reliable and delamination resistance CFRP.

T1000 carbon fibers are far superior to T300 fibers in tension, but the performance of bulk T1000 composites can be matched by bulk T300 composites interleaved with sparsely distributed micro-/nano- Aramid pulp (AP) fibers. In this study, we focus not only on the short-beam shear strength but also on the flexural strength of T1000 and T300-AP composites before and after impact, as these properties are critical indicators of structural performance under bending-dominated loading conditions. Maintaining the AP-epoxy interlayer thickness increase at 8 mu m or less, with AP areal densities of 2, 4 and 6 g/m2, leads to improvements of up to 38 % in short-beam shear strength and 55 % in flexural strength for the T300-AP composites, surpassing the performance of plain T1000 composites without such AP-interfacial toughening. These findings highlight the importance of interfacial design and quasiZ-directional fiber bridging in CFRPs, demonstrating that resin-rich layers between carbon fiber plies as thin as 15 mu m can be transformed into mechanically interlocked ply interfaces through AP-interfacial toughening, thereby bringing the structural performance of T300-AP composites to parity with that of T1000 composites.

Carbon fiber reinforced polymer (CFRP) composite has undoubtedly revolutionized advanced engineering applications due to its lightweight and high strength. In this study, self-made zirconia fiber (ZF) via electrospinning was introduced into the interlayer of laminated CFRP composites to construct the fiber bridging to prevent crack generation and propagation, which could improve weak regions of resin-rich region (RRR) and interfacial transition region (ITR). Low-velocity impact results showed ZF-implanted CFRP composites exhibited better impact resistance than unreinforced CFRP composites. Three-point bending testing results demonstrate that the flexural strength of CFRP composites with 0.25 wt.% ZF before and after impact yielded the greatest 26.3% and 133.4% increments respectively compared with unreinforced ones, and the former had 55% and 121.5% higher energy absorption than that of the control group in pre impact and post-impact damaged energy absorption respectively. XRM-CT and SEM scanning results indicated the trace of fiber bridging of ZF on the damaged surface and its effects on shifting delamination failure of unreinforced CFRP composite to shear failure of ZF-implanted CFRP composites. Overall, introducing ZF into the interlayer might be an easy and effective method for manufacturing high-performance CFRP composites in industries.

To address the interfacial failure caused by insufficient interlaminar bonding in Carbon Fiber Reinforced Polymer (CFRP) composites, an effective electrospinning technique is proposed to prepare the Polyethylene-co-Maleic Anhydride (PEMA) modified Polyvinylidene Fluoride (PVDF) fibers on CF fabrics to improve the flexural performance. Testing results show that the prepared PVDF fibers had various diameters varying from several hundred nanometers to several micrometer and were disordered to form semi-bonded PVDF-CF integrated structure. CFRP composite with PVDF areal density of 0.16 g/m2 yielded the greatest flexural strength of 888.24 MPa and post-impact residual flexural strength of 122.05 MPa, exhibiting 25.1% and 68.6% increments respectively. Fiber trunks of PVDF were relatively stable and fiber ends were free-moved, which made them easier to construct fiber bridging network in situ compared with the fiber agglomeration of directly introducing fiber. The PVDF fibers bridging network at the interlayer could improve brittle epoxy resin, embed interfacial transition region and even penetrate adjacent CF, forming a three-dimensional interlocking that suppressed micro-crack generation and propagation. This contributed to failure modes changing from delamination dominated failure of unreinforced CFRP composites to shear-dominated failure of PVDF-reinforced composites. Overall, electrospinning method could provide an important alternative for manufacturing high-performance laminated FRP composites in industrial field.

As a key indicator for evaluating the fracture behavior of elastic-plastic materials, the size of the crack tip plastic zone is significantly affected by the strain hardening effect. However, the boundary effect model (BEM), which was originally developed for quasi-brittle materials, does not explicitly account for this effect, thereby limiting its applicability to elastoplastic materials. To address this limitation, this study proposes a modified BEM-based fracture prediction model for weld metals that inherently accounts for strain hardening. First, the strain hardening index is introduced to quantify the crack tip plastic zone size, refining the conventional BEM. Next, the proposed model is validated through three-point bending and tensile tests on low-carbon steel weld metal specimens. The prediction capability of the modified model was compared with the conventional BEM to thoroughly evaluate the fracture performance of the weld metal. Results indicated that the improved model determined a fracture toughness of 127.42 MPamand a yield strength of 403.05 MPa for the low-carbon steel weld metal. Both values showed excellent agreement with experimental results. Furthermore, the analytical value for the plastic zone length exhibits an error of only 0.27 mm relative to the experimental value. The proposed model provides a practical and robust analytical approach for fracture research in elastoplastic welded joints without relying on extensive data fitting.

This study investigated the collapse behaviour and failure mechanism of composite thin-walled eggshells under hydrostatic pressure. The eggshells comprised a hand-laid composite outer layer and a 3D-printed nylon liner. Hydrostatic pressure tests, geometric measurements, and finite element analyses were conducted to evaluate their structural performance and collapse mechanisms. The results showed that the lay-up composite eggshell achieved the highest structural efficiency, with performance ratios 129.13%, 530.11%, and 200.36% greater than those of wet-filament-wound, 3D-printed, and machined eggshells, respectively. Two distinct collapse modes and three failure stages were identified. Damage initiated in the composite layers and progressively propagated with increasing pressure. As the stiffness of the composite layers degraded, more load transferred to the nylon liner, causing significant deformation. The ultimate collapse of the eggshell was governed by the coupling of composite damage progression and significant liner deformation. A semi‑analytical model for ultimate load was developed using response surface methodology and validated against nine independently designed specimens, with prediction errors ranging from –4.33% to 4.00%. These findings provide new insights into the collapse mechanisms of composite pressure shells and offer an efficient design approach for lightweight deep-sea pressure-resistant structures.

This study uncovers a critical discrepancy between static and impact fracture toughness across distinct zones of low carbon steel welded joints. Specimens were prepared using E4303 welding electrodes via shielded metal arc welding at a current of 100 A, voltage of 30 V, and a welding speed of 5 mm/s. Non-destructive continuous ball indentation and Charpy V-notch impact testing was conducted across weld metal (WM), fusion zone (FZ), heat-affected zone (HAZ), and base metal (BM). The results show that static fracture toughness exhibited the following distribution: WM (151.0 MPa root m) > HAZ (120.0 MPa root m) > BM (95.2 MPa root m ) > FZ (91.7 MPa root m ). In m contrast, the fracture toughness obtained from the Charpy V-notch impact test showed a different distribution: FZ (102.2 J) approximate to HAZ (103.5 J) > WM (91.0 J) > BM (69.8 J). Microstructural observations indicate that the low static toughness of FZ is associated with its coarse, heterogeneous grain structure, while WM exhibits reduced impact energy due to the presence of Widmansta & uml;tten ferrite. These findings highlight the role of microstructural heterogeneity and the need for region-specific fracture assessment. Moreover, static indentation measurements alone may overestimate the fracture resistance under dynamic loading conditions. This work provides a novel comparative perspective connecting microstructural features to both static and impact fracture performance, offering practical guidance for more accurate structural integrity evaluation of welded steel components.

Lightweight aggregate foam concrete (LAFC), composed of lightweight aggregate, cement, fly ash, and foam, features a highly heterogeneous internal structure. Its fracture performance is significantly influenced by specimen size due to large aggregates. In this study, a rapid experimental method and theoretical model were developed to evaluate the fracture performance of LAFC with expanded clay aggregate while eliminating the commonly observed size effect. A total of 622 specimens with six different mix proportions were prepared, and three-point bending (3-p-b) fracture tests were conducted with various specimen sizes and initial notch lengths. The results showed that as the foam content increased, the fracture behavior of LAFC shifted from cracks penetrating the aggregates to cracks bypassing them. Regardless of the crack propagation mode, the boundary effect model (BEM) adopted in this study accurately predicted the tensile strength (ft) of LAFC, and the fracture toughness (KIC) was calculated from ft and the average aggregate diameter. The agreement between the experimental results and the BEM predictions was evaluated using Bland-Altman analysis. Thus, KIC can be determined through the small 3-p-b fracture test, which cannot be analyzed by Linear Elastic Fracture Mechanics (LEFM). Based on a comprehensive analysis of the test data, recommended specimen parameters for the LAFC fracture tests are proposed. Compared with the minimum specimen sizes calculated according to the ASTM standard, the recommended sizes are reduced to one-tenth, making the method easier to implement in laboratories. The results also reveal that aggregate packing density has a significant effect on the fracture performance of the LAFC with crack penetrating aggregate mode, and the proportions of the constituent materials exert additional influence. The fracture characteristics of LAFC can therefore be optimized through adjustments to material parameters.

Knowledge and accurate prediction of crack extension in rocks that incorporates accurate fracture criterion and fracture parameters are crucial for the stability of rock masses and for safe design of rock structures. While the stress intensity factor (SIF)-based crack propagation criteria have been employed to evaluate the fracture process of concrete, limited research is conducted on the applicability of SIF-based criteria in modelling the crack extension in rocks. In this paper, a numerical model was proposed to evaluate the mode-I crack propagation process in rocks with the consideration of the nil-SIF-based (KP IC-K sigma IC = 0) and initial fracture toughness (Kini IC )-based criteria (KP IC-K sigma IC = Kini IC ), where KPICand K sigma IC represent the SIF induced by external loads and cohesive forces, respectively. To facilitate these simulations, the fracture parameters were analytically calculated using the boundary effect model (BEM) and validated with those measured from experimental tests. Laboratory experiments were carried out on three-point bending (3-p-b) sandstone beam specimens with different initial crack length. After the validity of the proposed model is verified with both the self-conducted experimental results and the test data available in the literature, a comparative analysis was conducted to assess the effectiveness of the two SIFbased criteria by comparing with experimental database given in the literature. The results indicated that the predicted load-crack mouth opening displacement (P-CMOD) response, maximum load, critical CMOD (CMODc) at the peak load using the KiniIC-based criteria showed better agreement with the experimental data, regardless of rock type, specimen configurations and dimensions, while the predictions derived from the nil-SIF-based criterion were underestimated. The crack resistance (KR) values calculated using the nil-SIF-based criterion were observed to be lower than those determined via the KiniIC-based criterion during the initial cracking phase, specifically for normalized crack extension lengths near 0.6. Beyond this threshold, the crack resistance becomes predominantly governed by cohesive forces, which results in larger KR values when the nil-SIF-based criterion is applied.

An asymptotic non-LEFM model is developed for shallow surface cracks comparable to material microstructures. The characteristic microstructure size (Cch) of single crystal silicon (SCS) is the atomic diameter (0.235 nm), and Cch of a nano-grained polycrystalline silicon (N-PCS) is its average grain size. N-PCS with Cch from 150 nm to 3 mu m is considered in this study. The fracture toughness (KIC) of both SCS and N-PCS can be predicted from their intrinsic strengths and respective Cch. Predicted KIC values of 0.90-1.40 MPa Jm for SCS and 1.56-5.31 MPa Jm for N-PCS are confirmed by collected experimental data of 0.74-1.38 MPa Jm for SCS and 1.43-3.46 MPa Jm for N-PCS. The intrinsic relation between the KIC, intrinsic strength and characteristic microstructure is both practically useful and fundamentally significant. The macroscopic KIC and intrinsic strength, previously considered as two separate material properties, are now linked together by the atomic-/nano-scale microstructures. This fundamental relation on strength, toughness and microstructure for brittle solids, verified by SCS and N-PSC, is comparable to the classic "Hall-Petch relation" for ductile metals. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

This collection comprises 71 peer-reviewed papers which summarise the most recent developments in the fields of advanced materials research and structural integrity.The papers contained in this special issue include contributions from Australia, Canada, China, Europe, Japan, Korea, New Zealand and the USA and have been grouped into the categories of: Bio- and Nano- Materials, Fracture and Fatigue, Ceramics, Concrete and Rock, Composites, and Structural Integrity. The work therefore provides a handy guide to the current state-of-the-art concerning these topics.

Superconductivity of a micron-sized hydride sample measured between metal probes under extreme pressure could be considered as a macroscopic quantum tunnelling phenomenon through metal-hydride-metal. The energy barrier height of hydride is regulated by pressure. The energy barrier width between tips of the metal probes should be minimized to limit the chance of exponential decay in electron tunnelling. There is also a thickness effect since thinner hydride samples around 1 micron are favoured for achieving higher superconductive temperatures. Hence, reduction in both barrier width and sample thickness is recommended to ensure optimum quantum tunnelling for realization of the room temperature superconductivity.

Carbon/basalt hybrid composites have attracted considerable interest as a cost-effective alternative to conventional carbon-fiber composites. However, their application in filament-wound composite pressure shells subjected to external hydrostatic pressure has received limited attention. This study experimentally and numerically investigated the buckling behavior and failure mechanisms of carbon/basalt hybrid cylindrical shells with different stacking sequences. The symmetric hybrid configuration achieved an average collapse pressure of 6.53 MPa, close to 6.57 MPa for the all-carbon shell, while replacing two-thirds of the carbon fiber layers with basalt fiber. A nonlinear finite element model incorporating initial geometric imperfections predicted the collapse pressures with a maximum relative error of 4.0%. Thickness-normalized simulations, which isolated the influence of wall-thickness variation, further confirmed the structural efficiency of the proposed hybrid stacking strategy, with the symmetric hybrid shell retaining 88.2% of the nonlinear buckling load of the all-carbon shell. Micro-computed tomography and scanning electron microscopy observations revealed brittle fracture in carbon fiber layers and more progressive damage in basalt fiber layers. A reinforcing-fiber material cost assessment showed that performance gains exceeded fiber-cost increases below approximately 27% carbon fiber content. These findings offer practical guidance for the design of lightweight, cost-efficient filament-wound composite pressure shells subjected to external hydrostatic pressure.

Recycled concrete aggregates (RCAs) typically exhibit higher chloride permeability and lower strength compared to natural aggregates, potentially accelerating steel corrosion and compromising the durability of reinforced concrete structures. While functional additives like fibers, fly ash (FA), and glazed hollow beads (GHBs) are known to improve concrete properties, the quantification of the synergistic effects of their hybridization in RAC and a systematic multicriteria-based performance assessment are still lacking. This study experimentally investigates the individual and combined effects of GHB, FA, BF, and PPF on the compressive strength and electric flux of RAC. Fourteen mixtures were designed with different RCA replacements (0, 30, 50, and 100%), FA contents (0, 10, 20, and 30%), GHB dosages (0, 15, and 30%), and PPF and BF hybridization (0, 0.1 and 0.2%). Compared to unmodified RAC with 50% RCA replacement, the addition of 30% GHB significantly decreased the electric flux by 34.1% but comprised the compressive strength by 9.4%, whereas FA provided a weaker electric flux reduction of 16.3% alongside a lower strength decrease of 6.0%. A multicriteria analysis revealed that the synergistic GHB-FA-BF-PPF hybridization achieved the best performance of all formulations, exhibiting a remarkable 40.7% reduction in electric flux and a slight 1.3% increase in compressive strength compared to the unmodified RAC specimen. These findings demonstrate that the practical use of RAC modified by GHB-FA-BF-PPF hybridization would be highly beneficial in terms of mechanical performance as well as chloride permeability.

Carbon fiber-reinforced polyetheretherketone (CF/PEEK) thermoplastic composites are increasingly used in biomedical implants and are attracting attention as potential alternatives to carbon fiber-reinforced epoxy (CF/ epoxy) thermosets due to their superior toughness and biocompatibility. However, delamination in CF/PEEK composite laminates, arising from the absence of fiber reinforcement in resin-rich regions, remains a critical limitation. This study demonstrates the interfacial toughening effect of micro-/nano- aramid pulp (AP) interleaving in unidirectional CF/PEEK laminates, as well as comparing the AP interleaving effect in CF/epoxy counterparts. AP-interfacial toughening led to notable improvements in CF/PEEK composites, with up to 21% higher longitudinal compressive strength, 27% higher transverse compressive strength, and 15% higher shortbeam shear strength. A comparison further revealed that AP-interfacial toughening exhibits distinct behaviors in CF/PEEK and CF/epoxy under different loading modes. While AP interleaving enhanced compressive strength in both systems, its effect on flexural strength diverged: CF/epoxy benefited due to compression-driven failure, whereas CF/PEEK, governed by tension-driven failure, experienced flexural strength reduction when interlayer thickness exceeded 10 mu m. Overall, this work establishes AP-interfacial toughening as an effective strategy to enhance CF/PEEK compressive performance by promoting fiber bridging in resin-rich layers and reducing delamination between carbon fiber plies.

Perfect bond between carbon fiber-reinforced polymer (CFRP) and steel is a prerequisite for effective performance of CFRP-strengthened steel structures. Indeed, the engineering utility of CFRP is typically governed by the behavior of the CFRP-to-steel bonded interface rather than its intrinsic strength. While the bonded joint is prone to randomly localized defects caused by air voids, superficial cracks or deterioration under external loads, their influence on debonding behavior of CFRP-to-steel joints has not been fully understood. This study proposes a closed-form analytical solution for the first time based on a bilinear Cohesive Zone Model (CZM) to predict the full-range debonding process of both long and short bonded joints with arbitrary localized defects. The predictions were validated with the experimental data and numerical results given in the literature. It was shown that the shape of the load-displacement curve of long joints exhibits a distinct two-peak load response followed by a snap-back due to sequential failure of bonded regions, while that of short joints was insensitive to the defect size. A defect covering 75% of the bonded area reduces the load capacity of short bonded joints by up to 40%. In long bonded joints, this severe degradation is substantially mitigated to below 20%, while the snap-back instability is found to be insensitive to defect size. Defect location determines which bonded segment governs the load capacity and shapes the load-displacement response, yet its primary influence is on failure progression and ductility rather than on the peak load. The proposed analytical solution enables engineers to quantify the influence of localized defects on the debonding progression and load capacity of CFRP-to-steel interfaces, which facilitates the design and maintenance of FRP-strengthened steel structures.

To improve interfacial condition and mechanical properties of basalt/carbon fiber reinforced polymer (BCFRP) laminates, this study innovatively employed a double electrospinning technique to prepare multi-directional polyvinylidene fluoride (PVDF) fiber veils on carbon fiber (CF) fabric surfaces. Energy-dispersive X-ray spectrometer (EDS) confirmed the uniform distribution of fluorine, verifying the successful anchoring of PVDF onto the CF fabric. With systematically varied areal densities (0.1-0.5 g/m2), the PVDF veils demonstrated a substantial enhancement in mechanical performance, with the 0.4 g/m2 density identified as optimal. This specific formulation yielded remarkable flexural and compressive strengths of 529.26 MPa and 248.08 MPa, corresponding to significant improvements of 37.9% and 43.6%, respectively, over the unreinforced specimen. Microstructural analysis via X-ray microscopy (XRM-CT) and scanning electron microscopy (SEM) revealed that the multi-directional PVDF veils established continuous fiber bridges at the interlaminar interface. These bridges provided a better fracture resistance to prevent the generation and propagation of micro-cracks, promoting failure mode variation from traditional dominated delamination to shear-dominated failure. This work established a novel technical pathway for developing high-performance PVDF@BCFRP laminates, presenting a viable alternative to traditional CFRP composites for civil applications.