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Comprehending the mechanical response of materials on an atomic level is pivotal in the optimisation of advanced materials with superior mechanical properties. This research article utilises the atomistic-scale based molecular dynamics simulations to report the uniaxial tensile behaviour of bicrystalline Ni-6Cu (Nickel – 94% and Copper – 6%) alloy incorporated with pre-existing faceted Σ3 [111] 60° {11 8 5} grain boundaries. The primary aim of this investigation is to comprehend the performance of bicrystalline Ni-6Cu alloy under varying thermodynamic conditions and to assess the influence of pre-existing faceted grain boundaries on its tensile behaviour. This work encompasses a range of strain rates (108 to 1010 1/s) and temperatures (spanning from 100 to 900 K) for the uniaxial tensile deformation simulations. The outcomes unveil that the Young's modulus of Ni-6Cu alloy (with pre-existing faceted grain boundaries embedded in its domain) was inversely proportional to temperature and constant with respect to strain rate. For the same configuration, yield stress was inversely and directly proportional to temperature and strain rate, respectively. Interestingly, incipient plasticity in the tensile stress–strain response was observed at lower temperature and lower strain rate. From the microstructural point of view, at lower temperatures, the incoherent twin boundary served as a source for the nucleation of stacking faults; however, as the temperature increased, both the incoherent twin boundary and the tips of coherent twin boundary function as the source for stacking faults formation. Our simulations also verified the GB's anti-thermal (or non-Arrhenius) migration behaviour even under tensile load. [ABSTRACT FROM AUTHOR]

Weathering agents can significantly affect the mechanical response of geotextiles, particularly when long exposure periods are involved. Usually, in design, changes in the mechanical behavior of geotextiles are represented by reduction factors for their tensile strength. However, their full tensile force versus elongation response can be affected. The main aim of this work was to contribute to defining simple procedures to estimate tensile force versus elongation curves for weathered samples of geotextiles. The tensile response of two thermally bonded polypropylene geotextiles, before and after natural and artificial weathering, was assessed experimentally and analyzed using different constitutive models: polynomial (Orders 4 and 6) and hyperbolic. The influence of weathering on the mechanical response of the geotextiles was analyzed, polynomial and hyperbolic models for representing the tensile force versus elongation response were adopted and their parameters derived, and simple relations were implemented to estimate model parameters for weathered samples. Results revealed the occurrence of changes in the tensile behavior of the geotextiles, both under natural and artificial weathering conditions. Both groups of models fitted the experimental data properly. The Order 4 and 6 polynomial models are shown to have limited application, as the model parameters had no link to the tensile properties of the geotextiles. By contrast, the parameters of the hyperbolic model were linked to the tensile properties, particularly if affected by correction factors. The hyperbolic model parameters of the weathered samples were estimated using the model parameters of the reference samples and the reduction factors to allow for weathering (initial stiffness and tensile strength). These estimates proved to be adequate for representing the tensile response of weathered samples, particularly for low ranges of elongation. Finally, a simple procedure to represent the tensile response of weathered geotextiles was proposed. This procedure has shown promise in generating realistic tensile versus elongation curves. [ABSTRACT FROM AUTHOR]

Boron nitride nanosheet (BNNS) is an attractive nanomaterial to improve polymeric materials in hydrogels due to their high mechanical properties, robust interfacial properties with polymer, and non-toxicity. However, the mismatching deformation capacity between BNNS and hydrogels results in damage to the BNNS-hydrogels interface and deteriorates the tensile properties of BNNS reinforced hydrogels. By adopting nanotechnology, the brittle nature of BNNSs can be modified. A novel penta-BNNS exhibits pentagonal rings, presenting ductile behavior under tensile deformation. The tensile test is performed by molecular dynamics simulations. The simulation results show that the ultimate failure strain of the penta-BNNS is significantly increased, which is attributed to the structure transition of the pentagonal rings in the penta-BNNS under tensile deformation. Due to the structure transition, the deformation capacity of the penta-BNNS is significantly improved with respect to the hexa-BNNS. This study links the structure to ductile behavior, which helps to devise advanced two-dimensional nanomaterials for improving hydrogels.

Textile-reinforced concrete (TRC) is a composite made with bi-directional non-metallic fabric embedded in a fine-grained cementitious matrix. When engineered appropriately, these composites can reduce material usage for the desired performance, resulting in slimmer sections and enhanced material efficiency, which in turn lowers the CO2 footprint. To facilitate the widespread application of TRC in practice, it is crucial to comprehend the material and structural behavior of these composites, which can pave the way toward an optimized design methodology. In this paper, the tensile response of TRC is studied with different textile geometries, volume fractions and matrix strengths. The influence of the coating impregnation on the effectiveness of the textile to enhance the response of the composite is discussed, with complementing evidence from microstructural observations. The results of tests with different textile configurations indicate a transition in the type of stress–strain response from tri-linear to bi-linear, beyond a certain effective volume fraction. The paper also presents a simplified model to predict the bi-linear response from the efficiency factor-based approach. The insights gained can assist in achieving composite designs with optimized sections and limited tensile stress cracking, ensuring the targeted performance in slender elements. [ABSTRACT FROM AUTHOR]

In this paper, the tensile mechanical behavior and progressive damage morphology of glass-fiber-reinforced magnesium alloy laminate for different numbers of holes in a temperature range of 25–180 °C were investigated. In addition, based on extensive tensile tests, the tensile mechanical behavior and microscopic damage morphology of porous-glass-fiber-reinforced magnesium alloy laminates at different temperatures were observed by finite element simulation and scanning electron microscopy (SEM). Finally, the numerical simulation and experimental results were in good accordance with the prediction of mechanical properties and fracture damage patterns of the laminates, the average difference between the residual strength values of the specimens at ambient temperature was 5.57%, and the stress–strain curves were in good agreement. The experimental and finite element analysis results showed that the damaged area of the bonded layer tended to expand with the increase in the number of holes, which has a lesser effect on the ultimate tensile strength. As the temperature increased, the specimens changed from obvious fiber breakage (pull-out) and the resin matrix damage mode to matrix softening damage and interfacial delamination fracture damage. As the testing temperature of the specimens increased from 25 °C to 180 °C, the tensile strength of the specimens decreased by an average of 51.59%, while the tensile strength of the specimens showed a nonlinear decreasing trend. The damage mechanism of porous-glass-fiber-reinforced magnesium alloy laminates at different temperatures is discussed in this paper, which can provide a reference for engineering applications and design. [ABSTRACT FROM AUTHOR]

This paper discusses the challenges in using natural fibers for the development of textile-reinforced mortar (TRM) composites with pseudo-strain-hardening and multiple cracking behavior. The particular characteristics of natural vegetal fibers are analyzed with reference to data from the literature. It is concluded that the efficient use of these fibers as composite reinforcement requires the development of treatment or impregnation protocols for overcoming durability issues, eliminating crimping effects in tensile response and imparting dimensional stability. Relevant experimental research on the synthesis and performance of natural TRMs is reviewed, showing that the fabrication of such systems is, at present, largely based on empirical rather than engineering design. In order to set a framework regarding the properties that the constituents of natural TRM must meet, a comparative analysis is performed against inorganic matrix composites comprising synthetic, mineral and metallic reinforcement. This highlights the need for selecting matrix materials compatible with natural fibers in terms of stiffness and strength. Furthermore, a rational methodology for the theoretical design of natural TRM composites is proposed. First-order analysis tools based on rule-of-mixtures and fracture mechanics concepts are considered. Based on the findings of this study, paths for future research are discussed. [ABSTRACT FROM AUTHOR]

In this paper, the tensile mechanical behavior and progressive damage morphology of glass-fiber-reinforced magnesium alloy laminate for different numbers of holes in a temperature range of 25–180 °C were investigated. In addition, based on extensive tensile tests, the tensile mechanical behavior and microscopic damage morphology of porous-glass-fiber-reinforced magnesium alloy laminates at different temperatures were observed by finite element simulation and scanning electron microscopy (SEM). Finally, the numerical simulation and experimental results were in good accordance with the prediction of mechanical properties and fracture damage patterns of the laminates, the average difference between the residual strength values of the specimens at ambient temperature was 5.57%, and the stress–strain curves were in good agreement. The experimental and finite element analysis results showed that the damaged area of the bonded layer tended to expand with the increase in the number of holes, which has a lesser effect on the ultimate tensile strength. As the temperature increased, the specimens changed from obvious fiber breakage (pull-out) and the resin matrix damage mode to matrix softening damage and interfacial delamination fracture damage. As the testing temperature of the specimens increased from 25 °C to 180 °C, the tensile strength of the specimens decreased by an average of 51.59%, while the tensile strength of the specimens showed a nonlinear decreasing trend. The damage mechanism of porous-glass-fiber-reinforced magnesium alloy laminates at different temperatures is discussed in this paper, which can provide a reference for engineering applications and design.

Owing to high heat flux ability and good mechanical strength, copper has been used for micro-electro-mechanical systems (MEMS) components with dimensions in micrometers processed by electrochemical methods. In the present study, fine grained copper foils of different thicknesses and grain sizes produced by pulsed electrodeposition under different controlled current densities were used to investigate the effect of total number of grains across thickness of foil on its tensile response and formability. For a comparative study, commercially available rolled Cu foils were also used. Vacuum annealing was employed to obtain a wide range of fully recrystallized grain sizes within same thickness of the foils. Detailed microstructural characterization was carried out using scanning electron microscope attached with electron backscattered diffraction detector. The foils were subjected to uniaxial tensile testing and formability testing using a miniaturized Nakazima test setup. As anticipated, finer the grain size higher was the yield strength. However, the strength of copper reduced with decreasing the total number of grains across thickness of the foil. The electrodeposited Cu foil exhibited relatively higher strength levels but reduced tensile ductility along with decreased strain hardening ability compared to the fully recrystallized Cu foils having similar grain sizes. Furthermore, the number of grains across thickness and the prior history of foils played significant role on the shape and trend in variation of the forming limit curve of Cu. An α-fiber (< 110 >) texture evolved in Cu during deformation and its volume fraction strengthened under biaxial deformation conditions. [ABSTRACT FROM AUTHOR]

We aim to demonstrate the creation of a fabricated fluidic antenna based on dielectric PDMS substrate, its unique properties of conductivity, flexibility, robustness, and use as an antenna. We evaluated an appropriate fluidic solution comprised of a polyethyleneimine (PEI) matrix assembled from nanoparticle Ttinum oxides and graphene. Various investigations of its mechanical flexibility (stress), thermal properties (DSC), and IR have been carried out on fabricated PDMS substrates, and a dielectric was recorded at 2.67. In addition, (TEM), IR, UV, and Electrochemical Impedance (EIS) tests have been performed to evaluate the PEI matrix-like surface morphology. The measurement and simulation outcomes show that the fabricated antenna operates at 1.8–2.6 GHz, which covers the WLAN band area.

This paper discusses the challenges in using natural fibers for the development of textile-reinforced mortar (TRM) composites with pseudo-strain-hardening and multiple cracking behavior. The particular characteristics of natural vegetal fibers are analyzed with reference to data from the literature. It is concluded that the efficient use of these fibers as composite reinforcement requires the development of treatment or impregnation protocols for overcoming durability issues, eliminating crimping effects in tensile response and imparting dimensional stability. Relevant experimental research on the synthesis and performance of natural TRMs is reviewed, showing that the fabrication of such systems is, at present, largely based on empirical rather than engineering design. In order to set a framework regarding the properties that the constituents of natural TRM must meet, a comparative analysis is performed against inorganic matrix composites comprising synthetic, mineral and metallic reinforcement. This highlights the need for selecting matrix materials compatible with natural fibers in terms of stiffness and strength. Furthermore, a rational methodology for the theoretical design of natural TRM composites is proposed. First-order analysis tools based on rule-of-mixtures and fracture mechanics concepts are considered. Based on the findings of this study, paths for future research are discussed.

Carbon honeycomb (CHC) is a novel carbon allotrope with excellent mechanical and physical properties and has great potentials for various energy and environmental applications. In this work, the tensile response of the CHC nanostructure is re-examined via molecular dynamics simulation to provide an atomistic understanding of its anisotropic mechanical properties and zero-stiffness as reported previously. The simulation results obtained demonstrate that the tensile response of CHC is closely related to the deformation of its constitutive graphene nanoribbons. To illustrate the underlying deformation mechanisms of the nanoribbons, the evolution of their atomic structure during the deformation is characterised by calculating several characteristic bond lengths and angles, and the atomic stress distribution. It is found that when tensile loading is applied in the armchair direction, the graphene nanoribbons undergo severe distortion and subsequent distortion flattening as the tensile strain increases, which leads to the zero-stiffness behaviour. For the tensile loading applied in the zigzag direction, the graphene nanoribbons are mainly stretched without distortion, giving rise to the anisotropic tensile response of CHC. In addition to the zero-stiffness and anisotropic behaviour, the negative Poisson's effect is also observed when a tensile loading is applied in the armchair direction. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) modeling of soil–geogrid interaction is a numerical challenge when simulating reinforced soil systems. Modeling the soil–geogrid interaction requires an appropriate consideration of the geogrid geometry, the materials' model, and the interface properties. In this study, a series of 3D models were developed using the finite-element method (FEM) to investigate the response of geogrid under confined and unconfined conditions focusing on geogrid tensile stiffness effects. In this regard, a modeling approach for the geogrids whose configuration is complex was proposed. The validity of the models was also justified by the good agreement between calculated numerical results and measured experimental data. Moreover, particular emphasis was placed on visualizing the soil–geogrid interaction and load transfer mechanisms. The load transfer mechanisms were embodied not only through the distributions of displacement, strain, and tensile force along the geogrid but also through the displacement fields inside the soil domain. The results from two series of tests showed that the proposed approach was capable of reasonably capturing the geogrid response, whether under unconfined or soil-confined conditions. [ABSTRACT FROM AUTHOR]

Unbonded flexible pipes are widely utilized in the exploitation of offshore oil and gas resources. They are connected to two of the most critical types of system: floating production platforms and underwater production systems. However, if some tensile armor wires are substituted by cables or broken, the tensile armor layer will be incomplete, which seriously reduces the safety and reliability of the flexible pipe. In the present study, models of a flexible pipe with a complete tensile layer and with the tensile layer partially missing were established. The error for the tensile stiffness obtained by the finite element model of an intact flexible pipe was only 1% compared with experimental results. Because the load borne by the inner tensile armor layer is larger under tension than that borne by the outer tensile armor layer, the loss of inner tensile armor wires has a greater impact on the tensile properties. The maximum axial elongation of the flexible pipe increases with the number of missing inner tensile armor wires as a cubic polynomial. If the distribution of the missing armor wires is too dense, a stress concentration and local bending may occur, which will reduce the tensile strength of the flexible pipe. [ABSTRACT FROM AUTHOR]

This study involves the fabrication of triply periodic minimal surface sheet lattices possessing two different topologies—Neovius and Schoen’s IWP. The structural characteristics of these materials, which were fabricated by laser powder bed fusion using CoCrMo alloy powder, were investigated. The tensile properties and deformation behavior of the materials were evaluated by increasing the unit cell size (1, 2.5, and 5 mm) for each topology. The results of the tensile tests showed that the yield strengths and Young’s moduli of both topologies decreased, and that their elongations increased with decreasing unit cell size. We compared the mechanical properties of the Neovius and IWP lattices, which had the same unit cell size, and found that the former exhibited higher yield strength, tensile strength, and elongation. Further, the tensile deformation behavior of the specimens was analyzed by applying the Gibson–Ashby analytic model. The Neovius lattice accommodated more uniform deformations in a greater number of cell layers. These experimental observations and the use of a simplified model of the lattice structure can enhance the understanding of the mechanism of the room-temperature tensile deformation of Neovius and IWP sheet-based lattice structures.

PE-UHPFRC is a new Ultra High-Performance Fiber Reinforced Concrete (UHPFRC), which is developed to reduce the environmental impact of conventional UHPFRC by replacing the steel fibers with synthetic ones and reducing the clinker content in the mix. The development of the dynamic elastic modulus, the evolution of free autogenous deformations and the eigenstresses development with age, under full and partial restraint conditions, were investigated for PE-UHPFRC and the results were put into perspective with that for conventional UHPFRC with steel fibers. Furthermore, the tensile responses of different mixes under imposed shrinkage were compared and discussed. The results showed a shorter setting time and consequently an earlier initiation of elastic modulus development for PE-UHPFRC compared with that of conventional UHPFRC. Furthermore, the developed eigenstresses under full restraint conditions in a PE-UHPFRC layer compared with that for conventional UHPFRC were reduced by more than 70%, which is highly beneficial especially for cast-in-place rehabilitation applications. [ABSTRACT FROM AUTHOR]

Flight feather shafts are outstanding bioinspiration templates due to their unique light weight and their stiff and strong characteristics. As a thin wall of a natural composite beam, the keratinous cortex has evolved anisotropic features to support flight. Here, the anisotropic keratin composition, tensile response, dynamic properties of the cortex, and fracture behaviors of the shafts are clarified. The analysis of Fourier transform infrared (FTIR) spectra indicates that the protein composition of calamus cortex is almost homogeneous. In the middle and distal shafts (rachis), the content of the hydrogen bonds (HBs) and side-chain is the highest within the dorsal cortex and is consistently lower within the lateral wall. The tensile responses, including the properties and dominant damage pattern, are correlated with keratin composition and fiber orientation in the cortex. As for dynamic properties, the storage modulus and damping of the cortex are also anisotropic, corresponding to variation in protein composition and fibrous structure. The fracture behaviors of bent shafts include matrix breakage, fiber dissociation and fiber rupture on compressive dorsal cortex. To clarify, ‘real-time’ damage behaviors, and an integrated analysis between AE signals and fracture morphologies, are performed, indicating that calamus failure results from a straight buckling crack and final fiber rupture. Moreover, in the dorsal and lateral walls of rachis, the matrix breakage initially occurs, and then the propagation of the crack is restrained by ‘ligament-like’ fiber bundles and cross fiber, respectively. Subsequently, the further matrix breakage, interface dissociation and induced fiber rupture in the dorsal cortex result in the final failure.

The strength of a rockbolt is one of the key parameters for the design of ground support systems. However, published mechanical performance data by suppliers are usually limited to tensile strength and elongation. To provide additional performance measures, mechanical tests on four commercially available solid reinforcing bar rockbolts have been performed and analysed. In each of the cases, the rockbolts are marketed by the manufacturers as being similar and equivalent products. The mechanical tests have been developed to mimic five modes of failure that include tension, shear, torsion, and nut/thread interface. The results show significant variability in seemingly similarly marketed products. Recommendations are made for suppliers to provide additional testing results (torsion, shear and nut/thread capacity) as standard data within their product specification sheets. A summary of recommended design parameters is provided based on the test results. [ABSTRACT FROM AUTHOR]

Glass laminate aluminum reinforced epoxy, as an attractive material for advanced aerospace applications, is most likely to face the challenge of various blunt notched damages. In this paper, the tensile tests of the glass laminate aluminum reinforced epoxy with circular and square blunt notches are conducted. The effects of notch geometry, such as notch diameter, notch corner radius, and off-axis angle, on the laminated tensile behaviors of glass laminate aluminum reinforced epoxy laminate are explored. A characteristic distance function representing the damage-affected region of notch is empirically constructed to predict the residual strength of the circular notched glass laminate aluminum reinforced epoxy based on a modified point stress criterion. For the square notched laminate, the strength is almost equal to that of the laminate with its circumscribed circle notch. Furthermore, the variation of two fracture patterns observed with the notch geometry is studied, and the evolution of the interlaminar delamination damage is analyzed after the metal chemical removal. [ABSTRACT FROM AUTHOR]

Certain martensitic alloys demonstrate significant crystalline anisotropy in coefficients of thermal expansion (CTEs), including very large negative (<−50 ppm) and positive (>100 ppm) CTEs along specific crystallographic orientations. In polycrystals, martensite detwinning during deformation imparts texture changes resulting in directional negative/positive thermal expansions. Several compositions of TiNb martensitic alloys were examined here for the compositional dependence of their degree of crystalline anisotropy in CTE and mechanical properties. Results indicated that increasing Nb content decreases detwinning stress and increases crystalline CTE anisotropy. An atomistic mechanism based on statistical thermodynamics was proposed to describe the reasons for anisotropic CTE in martensitic alloys. Image, graphical abstract [ABSTRACT FROM AUTHOR]

[Display omitted] • The penta-boron nitride nanosheet exhibits ductile behavior under tension instead of brittle behavior in the hexa -boron nitride nanosheet. • Structure transition in the penta-boron nitride nanosheet yields progressive failure under tension up to the strain 0.9. • The penta-boron nitride nanosheet extends the collapse strain 0.274 in the hexa -boron nitride nanosheet to 0.9. • The penta-boron nitride nanosheet sustains the load-carrying capacity after bond breaking and crack development. Boron nitride nanosheet (BNNS) is an attractive nanomaterial to improve polymeric materials in hydrogels due to their high mechanical properties, robust interfacial properties with polymer, and non-toxicity. However, the mismatching deformation capacity between BNNS and hydrogels results in damage to the BNNS-hydrogels interface and deteriorates the tensile properties of BNNS reinforced hydrogels. By adopting nanotechnology, the brittle nature of BNNSs can be modified. A novel penta-BNNS exhibits pentagonal rings, presenting ductile behavior under tensile deformation. The tensile test is performed by molecular dynamics simulations. The simulation results show that the ultimate failure strain of the penta-BNNS is significantly increased, which is attributed to the structure transition of the pentagonal rings in the penta-BNNS under tensile deformation. Due to the structure transition, the deformation capacity of the penta-BNNS is significantly improved with respect to the hexa -BNNS. This study links the structure to ductile behavior, which helps to devise advanced two-dimensional nanomaterials for improving hydrogels. [ABSTRACT FROM AUTHOR]

Abstract Carbon fiber-reinforced polymer (CFRP) composites have excellent structural properties and potential multifunctionality, but thermal conductivity enhancement is desired to meet the heat transfer requirement due to low thermal conductivity in the through-thickness direction. The micro-nano boron nitride (BN) fillers were incorporated into the CFRP by the acetone vehicle-solvent to prepare three phase composites with relatively high thermal conductivity. Three prediction models were presented to estimate the thermal conductivity of composites respectively based on component configurational correlation, filler penetration degree, and ease of conductive chains formation. Most predicted results for modified composites show good agreement with experiments. The effects of vehicle-solvent concentration on microsurface morphology of prepreg and thermal conductivity of composites were conducted, and the thermal modification mechanism was explored based on above-mentioned and filler distribution. The tensile responses of modified composites also show obvious difference as the variation of vehicle-solvent concentration. The degradation of mechanical property suggests that it is a couple of potential challenges between structural property and thermal functionality. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The dislocation emission mechanism of the low-angle twist grain boundary is revealed. • Stress variation during dislocation emission is observed. • The influence of GB structures and temperature on dislocation density is obtained. Abstract Molecular dynamics simulations are performed to investigate the tensile behavior of W bicrystals with different twist grain boundaries (TGBs): the low-angle grain boundary (LAGB), the ordinary high-angle grain boundary (HAGB) and the Σ 3 TGB. Owing to the initial hexagonal dislocation network (HDN), the LAGB can directly emit dislocations without dislocation nucleation: the 1 2 〈 1 1 1 〉 dislocations in HDN are pinned by bilateral nodes or 〈 0 0 1 〉 dislocations and form Frank-Rend dislocation sources, which continually emit dislocations and remain the structure of HDN under tensile loading. Once the HDN become disordered, Frank-Rend dislocation sources are broken and dislocations in HDN can be directly emitted. In the ordinary HAGB and Σ 3 TGB, dislocations are nucleated from interfaces accompanied with apparent stress decrease at nucleation sites. Supplied with enough stress, emitted dislocations can freely pass through adjacent boundaries. By measuring dislocation densities, we find that the Σ 3 TGB becomes more active at high temperature and easier to nucleate dislocations, while the LAGB and ordinary HAGB are less affected by temperature. Besides, it is found that 1 2 〈 1 1 1 〉 dislocations play a dominate role in the plastic deformation of W bicrystals regardless of TGB structures and temperature. [ABSTRACT FROM AUTHOR]

The paper presents a solid-mechanics based method for the determination of the macroscopic tensile properties of fibers composed of monodispersed Carbon NanoTubes (CNTs), whose length is much lower than the fiber length, arranged in a cross-sectional square lattice. In the longitudinal direction, each CNT is offset, with respect to the neighboring ones, of a given quantity. The interaction between the CNTs caps is negligible, while the model takes into account the coupling occurring on their lateral surfaces, thanks to van der Waals forces and cross-links, modeled as distributed springs. One of the main improvements with respect to previous studies is that the CNTs are here modeled as deformable elastic bars, with given axial stiffness. Under the assumption that, due to the periodicity of the CNTs arrangement, each CNT is subjected to the same loading state, it is demonstrated that the axial strain/stress fields are governed by a delayed-advanced differential equation, that is here solved by means of finite difference technique. This allows to evaluate the total axial force on the fiber, and, consequently, its effective tensile stiffness, strongly dependent on the length of the constituent CNTs, their offset and their axial compliance. Comparisons with literature data confirm the accuracy of the proposed approach. [Display omitted] • An analytical–numerical model is proposed for Carbon NanoTube fibers under traction. • CNTs are modeled as deformable elastic bars, periodically arranged. • Van der Waals interaction among CNTs is modeled by shear springs on lateral surfaces. • The fiber stiffness is governed by longitudinal offset of the CNTs and their length. • The obtained results are in agreement with experimental data. [ABSTRACT FROM AUTHOR]

Ultra-high performance concrete (UHPC) is an ideal construction material to cut down carbon emissions due to its superior mechanical performance and durability. It is important to clarify the relationship between the microstructure and the overall tensile response of UHPC. In this paper, a microstructure-based multiscale framework is proposed to predict the stress-strain curve of UHPC under tensile load. The linear elastic stage is obtained by estimating the effective properties with the multi-level homogenization scheme based on the microstructure. The strain hardening and tension softening processes in the tensile curve are predicted with a statistical micromechanical damage model, where the characteristics of steel fibers are considered, including the effects of slip-softening, residual bonding strength of the fiber/matrix interface, matrix spalling and fiber orientation distribution. Comparisons with existing test results and previous models demonstrate the feasibility of using this multiscale framework to predict the overall tensile response of UHPC, especially the tension softening branch. Finally, the effects of interface parameters, matrix spalling degree, fiber orientation distribution, hydration degree and water/binder ratio on the tensile response of UHPC are evaluated and discussed with the proposed framework. [ABSTRACT FROM AUTHOR]