When the strengthening material - fabric-reinforced cementitious matrix (FRCM) composite is used as the anode in the impressed current cathodic protection (ICCP) for reinforced concrete structures, its long-term performance will be compromised due to anode acidification. Incorporating graphene into the matrix offers a means of mitigating interface deterioration by delaying the localized calcium leaching. This paper presents the results of a study to investigate the mitigation effects of graphene on the mechanical and electrochemical properties of FRCM composites. Direct tensile and pull-out tests were performed on graphene-enhanced FRCM (Gr-FRCM) composites subjected to different ICCP current densities and graphene dosages. The results reveal that graphene significantly reduces the deterioration in tensile and interfacial properties induced by long-term ICCP. The degradation factor for the ultimate tensile strain of FRCM composites under ICCP follows an exponential relation of total electrons, whereas the addition of graphene reduces this factor by more than half. Two constitutive models were developed to predict the key mechanical parameter, the effective strain of fibres, in the FRCM composite subjected to cathodic protection with and without graphene. These models were validated against beam test results and shown to be accurate for calculations of the flexural resistance of concrete beams strengthened using Gr-FRCM composites.

An ultimate axial strain model for FRP sufficiently-confined recycled aggregate concrete columns

Developing synthetic materials that replicate the nonlinear and anisotropic mechanical behavior of soft tissues remains a central challenge in tissue engineering. Here, we present a silk fiber-reinforced interpenetrating polymer network (IPN) hydrogel platform engineered to achieve a tunable balance of tensile strength, extensibility, and stiffness. By varying fiber orientation - longitudinal, transverse, and cross-plied (CP) - we introduced directional anisotropy that emulates key structure-function relationships observed in native fibrous tissues. The longitudinal and CP composites exhibited significantly enhanced mechanical performance, with ultimate tensile strengths of 8.1±2.3MPa and 6.8±1.0MPa, and elastic moduli of 28.2±5.4MPa and 25.8±5.3MPa, respectively - significantly larger than the unreinforced hydrogel and transverse configuration. Despite increased stiffness, these configurations maintained physiologically relevant ultimate strains: 46.5±12.0% (longitudinal) to 63.5±33.6% (transverse), closely matching values for native coronary arteries (54.0±25.0%). The CP configuration further reproduced the nonlinear strain-stiffening and pressure-dependent compliance characteristic of coronary adventitia, with measured radial compliance (1.9-2.1 %/100mmHg) within the range of human coronaries and saphenous veins. These findings demonstrate that coupling long-fiber alignment with IPN architecture enables controlled anisotropy and physiological mechanical fidelity, providing a robust framework for next-generation vascular grafts, adventitial wraps, and soft-tissue phantoms.

How bending causes distal radius fracture: Evidence from 6dof load measurement and digital image correlation.

The study investigates the efficiency of using the bearing capacity surface in the design of reinforced concrete sections. Two methods for constructing it in the N–Mx–My force space are considered: the direct method, based on a parametric sweep of external forces, and the inverse method, in which points of the surface are determined by specifying ultimate strains followed by calculating the corresponding forces. The accuracy of determining the strength utilization coefficient based on the ultimate moment was evaluated on a test load set by comparing it with reference values obtained from direct ultimate state calculations considering the physical nonlinearity of materials. It is shown that both surfaces provide high accuracy, while the direct method produces a smoother surface, and the inverse method allows for a significant reduction in construction time.

ABSTRACT The rate-dependent damage and constitutive behaviour of micro-fibre-reinforced recycled cementitious composites (MF-RCC) were systematically investigated under high strain rates (40–380 s−1) using Split Hopkinson Pressure Bar (SHPB) tests combined with in-situ X-ray computed tomography (CT). A secant-stiffness-based damage variable was defined, and a dynamic damage – constitutive model incorporating a Dynamic Fibre Influence Factor (DFIF) was developed to characterise the coupled effect of strain rate and fibre content. The model reproduced the nonlinear responses across pre- and post-peak stages with high accuracy. CT quantification revealed that increasing fibre content effectively reduced pore volume fraction and crack connectivity, confirming the fibre-induced suppression of damage evolution. The results show that 2.0% fibre content at 377.6 s−1 enhanced peak stress and ultimate strain by 11.0% and 65.0%, respectively, whereas excessive fibres (2.5%) led to mild deterioration due to non-uniform dispersion. The integrated testing–modelling-CT framework provides a mechanism-based approach to predict the dynamic response and microstructural damage of MF-RCC, offering insights for fracture-resistant design of sustainable cementitious materials.

This study investigates the axial compressive behavior of initially damaged recycled aggregate concrete (RAC) prisms confined with carbon fiber-reinforced polymer (CFRP). Monotonic compression tests evaluated the effects of the recycled aggregate replacement ratio, concrete strength, initial damage level, and the number of CFRP layers. Results indicate that CFRP confinement significantly enhances RAC load-bearing and deformation capacities. Conversely, increasing the replacement ratio reduces compressive strength, particularly in high-strength concrete. Initial damage negatively impacts axial performance by primarily reducing the turning point strength, an effect not fully mitigated by additional CFRP layers. Furthermore, a constitutive stress–strain model incorporating a damage evolution parameter was developed for 30 to 60 MPa structural-grade RAC. Although precise ultimate strain prediction remains intrinsically challenging due to stochastic premature CFRP rupture at square corners, the proposed model reasonably captures primary mechanical trends, providing an acceptable theoretical basis for structural rehabilitation.

Abstract This study presents a methodology to evaluate the ultimate load‐bearing capacity of prestressed concrete girders subjected to chloride‐induced corrosion. The model accounts for bending, shear, and bond failure, incorporating the effects of localized wire ruptures and the resulting local reduction in prestressing force. The effects of pitting corrosion on the prestressing reinforcement are incorporated in terms of reduced cross‐sectional steel area and corresponding prestressing force, reduced ultimate steel strain, reduced bond strength between concrete and steel, and an increase in transfer length. The influence of these factors on the structural capacity is assessed. Additionally, spatially distributed corrosion pits are considered in the wires of the strands by scaling the average corrosion pit depth of each strand according to a spatially correlated scaling factor. The results show that incorporating spatial variability in the pits has a significant effect, typically resulting in lower values of the predicted load‐bearing capacity, particularly when extreme pits are aligned in one cross‐section of the structure. By combining the methodology for the structural evaluation with a two‐dimensional chloride ingress model, the degradation of the structural capacity is predicted over time.

This work investigates how progressive microdamage accumulates in intact human fourth ribs under bending loads and how acoustic emission (AE) signals reflect that deterioration. Twenty-four ex vivo ribs (eighteen under quasi-static ( < 0.0004 s − 1 ) and six under dynamic (0.012– 0.042 s − 1 ) ) were subjected to three-point bending while AE sensors recorded microcrack activity near regions of peak tensile stress. To accommodate large deformations and complex geometry, we applied finite strain theory and described the mechanical response with an orthotropic continuum damage model. Damage growth followed a Weibull distribution, and stiffness degradation closely tracked the damage variable. We then correlated AE event counts with damage progression by fitting an empirical relationship that captures both the gradual accumulation of low-damage events and the abrupt increases in events near failure. Our analyses reveal three key outcomes. First, the Hild–Lemaître quasi-brittle damage model provides an excellent fit to stress-strain data across all strain-rate regimes. Second, cumulative AE counts increase monotonically with internal damage, confirming AE as a reliable real-time proxy for microcrack evolution. Third, AE-damage curves differ qualitatively with strain rate: quasi-static tests produce strongly convex profiles culminating in a near-vertical asymptote, whereas dynamic tests exhibit an initial concave segment followed by a more linear trend before ultimate failure. Furthermore, it was observed that increasing strain rate elevates both ultimate and damage strains, whereas subject age is associated with reductions in ultimate stress and stiffness. In contrast, BMI exerts only minor effects. Finally, b -value analysis did not yield predictive insight for human cortical bone fracture, unlike in concrete. Together, these findings establish AE monitoring coupled with continuum damage mechanics as a powerful framework for characterizing rate-dependent failure in rib cortical bone, which could inform real-time clinical monitoring during high-risk procedures.

The anti-aging performance of stay cables in complex marine environments is directly related to the long-term service safety of sea-crossing cable-stayed bridge structures, and it has been recognized as one of the key issues for the priority evaluation of the structural performance of sea-crossing cable-stayed bridges with Basalt Fiber Reinforced Polymer (BFRP) cables. In this paper, the coupled aging effects of ultraviolet radiation, salt spray, temperature and humidity, and prestress on BFRP cables were taken into consideration. Accelerated aging tests involving the coupling of light, heat, water, salt, and prestress were carried out to simulate the actual marine service environment. The anti-aging performance of BFRP cables was investigated by combining the analysis of macro mechanical properties with the characterization of micro structural morphology. The results of the study were as follows: (1) With the increase in aging duration, the tensile strength and ultimate fracture strain of BFRP cables decreased gradually. The degradation rates of tensile strength and ultimate fracture strain of BFRP cables exhibited a decreasing trend, characterized by an initial rapid phase followed by a gradual slowdown under the coupled aging effects of light, heat, water, salt, and prestress. (2) Compared with the significant decrease in tensile strength, the elastic modulus of BFRP cables showed an insignificant decrease. The elastic modulus of BFRP cables was observed to exhibit a trend of initial decrease, subsequent increase, and another decrease, with an overall reduction. (3) Temperature and prestress were verified to exert a considerable influence on the anti-aging performance of BFRP cables. The influence of temperature on the degradation of aging performance of BFRP cables was found to be greater than that of prestress. (4) The degradation in the anti-aging performance of BFRP cables under coupled aging effects was confirmed to originate from the initiation and propagation of microcracks in the resin matrix, which were caused by the combined actions of prestress, photochemistry, and hydrolysis. Meanwhile, the damage to the fiber–resin interface was accelerated by chloride ions in seawater under high-temperature conditions, which ultimately led to a reduction in the anti-aging performance of BFRP cables.

In this study, we investigated the impact of nitrogen doping of vertically-aligned carbon nanotube (VACNT) arrays on their interaction with an elastomeric polymer. Specifically, we synthesized undoped and N-doped VACNT (N-VACNT) arrays and examined the direct current (DC) conductivity, terahertz (THz) responses, and elastic properties of their polydimethylsiloxane (PDMS)-impregnated composites. Structural diagnostics confirmed that incorporating approximately 1 at% nitrogen yielded mechanically stiff N-CNTs with superior ordering within the array compared to undoped VACNT array. This structural enhancement led to significantly improved conductivity and THz shielding efficiency in N-VACNT/PDMS composites. For instance, a 70µm-thick N-VACNT array impregnated with PDMS achieved a transmittance of 10-3, comparable with the value for an impregnated 200µm-thick undoped array. Despite exhibiting lower ultimate tensile strains (40% for N-VACNT/PDMS vs 70% for VACNT/PDMS), the N-VACNT/PDMS composites provided a broader conductivity and transmittance modulation window with less deformation. Under initial tension, undoped and N-doped PDMS-impregnated arrays showed distinct electrical and THz behaviors. While VACNT/PDMS composites suffered from permanent conductivity loss and material rearrangement upon initial stretching, N-VACNT/PDMS composites displayed fully reversible DC conductivity and a stable THz response over repeated stretch-release cycles. Density functional theory calculations revealed that graphite-like and pyridine-like nitrogen atoms in the nanotube walls enhance the adsorption of PDMS chains. Stronger interfacial bonding, combined with the superior ordering of stiff N-VACNTs, enables complete recovery of the N-VACNT/PDMS composite structure and its electromagnetic response after deformation. These results highlight the key role of nitrogen doping in tailoring both the nanoscale structure and performance of CNT-elastomer composites. The N-VACNT/PDMS system thus emerges as a leading candidate for stretchable THz components and other applications requiring stable, reversible electromechanical response, paving the way for advanced tunable sensors and functional composites.

This study investigates the compressive behavior and analytical modeling of natural and rubberized concretes confined with cost-effective glass fiber-reinforced polymer (GFRP) jackets. Forty-two cylindrical specimens were tested under axial compression, including natural aggregate concrete (NAC) and rubberized concretes (RuC) prepared with 20% fine aggregate replacement using coarse (2.0mm) and fine (0.425mm) waste tire rubber. Both full and strip GFRP wrapping configurations with two, four, and six layers were examined. The results showed that GFRP confinement substantially enhanced both strength and ductility, transforming brittle failure into a gradual, energy-absorbing response. Full wrapping produced up to 63% and 90% strength increases for NAC and rubberized concretes, respectively, with ultimate strain gains exceeding 1300% in the fine-rubber mix. Strip wrapping achieved moderate yet significant improvements while offering material savings. Analytical models were developed for both concrete types to predict confined stress-strain behavior, achieving strong correlations (R2 = 0.84-0.99) between predicted and experimental data. The derived regression-based formulations successfully captured the influence of confinement pressure, rubber content, and wrapping configuration. These findings demonstrate that GFRP provides an economical and sustainable confinement solution for enhancing the performance of rubberized concrete in structural and retrofitting applications.

An atomistic study is conducted to elucidate the fracture behavior of pristine and centrally pre-cracked T4,4,4-graphyne nanosheets (150 Å × 150 Å) under uniaxial tension in both X- and Y-directions. Stress–strain responses are analyzed as functions of crack length (30–60 Å), orientation (0°–90°), and temperature (200–1000 K). Elastic modulus degradation is captured by power-law and trigonometric models, yielding high correlation coefficients. Ultimate tensile strength and fracture strain are shown to decline with increasing crack length and temperature, while toughness and mode I fracture toughness illustrate anisotropic energy absorption and crack-tip shielding effects, particularly under X-loading where ligament bridging and bond rotation mechanisms are activated. Thermal softening is modeled via the Wachtman equation, revealing near-linear modulus reduction and an inversion of directional stiffness at elevated temperatures. The results demonstrate that crack-length thresholds (~30% of sheet width) and mixed-mode loading conditions critically govern the transition from ductile-like to brittle fracture regimes in anisotropic 2D graphyne nanosheets.

ABSTRACT Sufficient ductility is required in structures to sustain earthquake displacement demand. In RC members, ductility is controlled by the confinement of concrete. Four parameters define the confined stress-strain curve, namely initial modulus, peak stress, strain at peak stress, and ultimate strain. A simplified cubic polynomial-based stress-strain curve is derived here from a screened experimental dataset. The coefficients are obtained using the properties of unconfined concrete and the conditions of the curve. A spring analogy is considered to combine the differential confinement in the case of rectangular RC sections. This proposed expression provides competitive estimates of concrete confinement in both circular and rectangular RC sections with only a few input parameters, unlike popular expressions.

Flax Fiber Reinforced Polymer (FFRP), as a green material with nonlinear large deformation characteristics, is used in the reinforcement of timber structures. Due to the similar elastic moduli of FFRP, adhesive, and timber, stress concentration at the interface is significantly reduced, demonstrating favorable interfacial performance. This study investigates the effects of adhesive layer thickness and FFRP laminate thickness on the strain distribution, bond-slip relationship, and stress distribution at the FFRP-timber interface through two different types of single-lap shear tests, thereby revealing the bonding mechanism at the FFRP-timber interface. The results show that both the ultimate load and the ultimate strain at the loaded end decrease with increasing adhesive thickness. For instance, increasing the adhesive thickness from 0.5 mm to 3 mm led to a 68.6% reduction in peak interfacial shear stress. The thickness of the adhesive has a minor influence on the overall trend of the bond-slip relationship curve for the FFRP-timber interface, with the curve consisting of an ascending branch, a descending branch, and a horizontal plateau. The distribution patterns of interfacial shear stress for different adhesive layer thicknesses are similar: at the initial loading stage, the maximum shear stress appears at the loaded end and gradually decreases toward the free end; as the load increases, the peak shear stress shifts from the loaded end toward the free end. With an increase in the number of fiber layers in the FFRP laminate, the strain transfer efficiency first increases and then decreases, reaching its maximum when the number of fiber layers reaches 30. The maximum stress increases with the number of FFRP fiber layers, and the stress transfer efficiency peaks at 30 layers.

Abstract The time-dependent behaviour specific to geological formations, known as creep, was investigated through a series of multi-stage uniaxial creep tests, applying six increasing stress increments until reaching the failure stage. The analysis confirmed the presence of the three distinct creep stages: primary, secondary (steady-state or stationary), and tertiary. Based on the strain-time data, it was demonstrated that the relationship between the ultimate axial strain (ε f ) and the final time (t f ) aligns with a power-law model. For modelling secondary creep, Norton’s power law was applied, yielding a stress exponent of n≈1.57 and ln(C)≈−10.74. This relatively low exponent value suggests that diffusion-based creep mechanisms may be dominant. However, the magnitude and non-monotonic variation of the secondary creep rate with respect to stress indicate the limitations of this simplified model, highlighting the microstructural complexity of the salt. In the tertiary creep stage, under the highest applied load (117.6 daN/cm 2 ), a pronounced acceleration of the strain rate was observed. Exponential extrapolation of this phase led to an estimated service life of approximately 123 days before reaching a critical strain of 5 %. The results are significant for calibrating constitutive damage models and for forecasting the long-term stability and lifespan of underground structures within Slănic Prahova salt deposit.

Abstract Thermal and mechanical properties of blends of nucleated heterophasic polypropylene copolymer (HECO) (80% homopolypropylene matrix and 20% ethylene-propylene rubber) with Vistamaxx™ (VM) statistical copolymer (85 wt% propylene and 15 wt% ethylene) have been investigated. The nucleating agent polyvinylcyclohexane (PVCH) has shown an improved crystallization behavior of the blends, maintaining high crystallization temperatures between 118.5 °C and 129.0 °C (± 0.2 °C). The small shift in the crystallization temperature indicates a very fast crystallization and excellent compatibility in the blend. The morphology and crystallization of different blend compositions have been investigated with small-angle and wide-angle X-ray scattering (SAXS–WAXS) and polarized light microscopy (PLM). The formation of small crystallites, uniformly distributed within the blends, leads to not only the formation of toughened materials but also a novel class of rubbery blends with high ultimate tensile strength, elastic modulus, and strain recovery. The results suggest that the optimized blend composition, in conjunction with nucleation, is a highly effective approach for superior physical cross-linking in the investigated elastomeric blends, offering both improved mechanical performance and environmental benefits by introducing a new class of advanced elastomers.

ABSTRACT In this research, black liquor from papermaking factories was applied to prepare a functionalized lignin-derived biochar. The microscopic observations confirmed the porous structure of the biochar. This biochar effectively played the role of both a reinforcing and toughening agent for poly(lactic acid) (PLA). Although the addition of untreated biochar to the PLA matrix adversely affected the mechanical performance, the presence of chemically modified biochar, with functional hydroxyl and carboxyl groups, enhanced all mechanical characteristics, including toughness, stiffness, tensile strength, and ultimate strain, as well as thermal properties. For the PLA/modified biochar system with balanced stiffness and toughness, 33%, 19%, 22%, 17%, and 43% improvements were observed in notched impact resistance, yield strength, stress at break, ultimate strain, and tensile toughness, respectively. While in the case of another modified biochar with the strongest reinforcing effect, about 140% increment in the tensile stress at break of PLA was achieved. This biochar assisted the PLA crystallization process and noticeably increased the crystallinity degree. The functionalization of biochar and the presence of an epoxidized soybean oil (ESO), as a plant-based reactive compatibilizer and chain extender additive, improved the filler dispersion state in the PLA-based biocomposite. By adding modified biochar and ESO to PLA, 80% increase was attained in the impact strength.

Gelcasting is a widely developed ceramic forming technique; however, a persistent challenge lies in the drying process, where cracking and deformation frequently occur, hindering the further development of gelcasting. In this study, a strategy was proposed to address warpage and cracking during drying through gel structure design, aimed at increasing the ultimate strain of the bodies. The stress–strain curves of the bodies were analyzed at the wet body, ethanol body, and dried body stages. The effects of different gels on the mechanical performance of the bodies and their roles in regulating drying stress were further examined. The incorporation of flexible polymer segments into the polyethylene glycol diglycidyl ether/polyethyleneimine (PEGDE/PEI) system enhanced the strain capacity of the bodies. A physically and chemically crosslinked gel, denoted as PEGDE/PEI-TAC/SMALA-Na (PPS), was designed and synthesized in a silicon carbide/carbon black aqueous slurry. This PPS gel imparted excellent mechanical properties to the bodies, manifested by high strain during the drying process and high strength after drying. These findings provide a new perspective for controlling the mechanical behavior of gelcast bodies through gel structure manipulation and achieving defect-free execution of the drying process in gelcasting.

Purpose This study aims to determine the influence of the effect of pulsation in wire laser additive manufacturing (WLAM) on the performance of ER308 stainless steel for applicability in critical industries. Design/methodology/approach ER308 stainless steel walls were fabricated using WLAM in pulsed and un-pulsed. Microstructural analysis was conducted via metallography, while mechanical properties were assessed through hardness, Charpy impact and tensile testing. Fractography was performed to evaluate failure mechanisms. Findings In the un-pulsed mode, samples exhibited a dual-phase microstructure, consisting of austenite with some ferrite. The pulsed mode resulted in a higher fraction of ferrite and finer grains due to rapid solidification and thermal cycling. Pulsed specimens displayed a more uniform hardness distribution, with values ranging from 165 Hv at the bottom to 230 Hv at the top, reflecting fine grain structures. Charpy impact tests showed an approximately 29.2% increase in energy absorption for pulsed specimens. Tensile testing revealed pulsed specimens had a higher ultimate tensile strength (853.47 MPa vs 831.25 MPa) and fracture strain (42% vs 38%). Fractography confirmed ductile failure in pulsed specimens and brittle fracture in un-pulsed specimens. Research limitations/implications This study is limited to ER308 stainless steel and specific WLAM parameters. Future work should explore other materials and process variations. Practical implications Pulsed WLAM improves mechanical performance and uniformity, making it suitable for aerospace, energy and automotive applications. Originality/value A direct comparison of pulsed and un-pulsed WLAM of stainless steel.