Interfacial Shear Stress Research Articles

Experimental study on progressive interfacial mechanical behaviors using fiber optic sensing cable in frozen soil

Frost heave and thaw settlement in cold regions pose a significant threat to engineering construction. Optical frequency domain reflectometry (OFDR) based on Rayleigh scattering can be applied to monitor ground deformation in frozen soil areas, where the interface behavior of soil-embedded fiber optic sensors governs the monitoring accuracy. In this paper, a series of pullout tests were conducted on fiber optic (FO) cables embedded in the frozen soil to investigate the cable‒soil interface behavior. An experimental study was performed on interaction effects, particularly focused on the water content of unfrozen soil, freezing duration, and differential distribution of water content in frozen soil. The high-resolution axial strains of FO cables were obtained using a sensing interrogator, and were used to calculate the interface shear stress. The interfacial mechanical response was analytically modeled using the ideal elasto‒plastic and softening constitutive models. Three freezing periods, correlating with the phase change process between ice and water, were analyzed. The results shows that the freezing effect can amplify the peak shear stress at the cable-soil interface by eight times. A criterion for the interface coupling states was proposed by normalizing the pullout force‒displacement information. Additionally, the applicability of existing theoretical models was discussed by comparing the results of theoretical back‒calculations with experimental measurements. This study provides new insights into the progressive interfacial failure behavior between strain sensing cable and frozen soil, which can be used to assist the interpretation of FO monitoring results of frozen soil deformation.

Experimental and theoretical study on mechanical performance of Fe-SMA/steel single lap joints

The activated iron-based shape memory alloy (Fe-SMA) can introduce considerable prestress in the damaged zone of deteriorated steel structures through bonding technologies. In China, it has been successfully applied to several kilometer-span steel bridges, such as Sutong Bridge and Hangzhou Bay Bridge. The shear and interfacial performance of steel-to-Fe-SMA plates are crucial issues in bonding Fe-SMA to reinforce deteriorated steel structures, which remain unclear. This paper investigates the shear characteristics of Fe-SMA/steel single lap joints (SLJs), considering the effects of adhesive types, adhesive layer thicknesses and overlap lengths. The stress distribution and the interfacial shear stress at the overlap zone are obtained through experiments, and the damage evolution and load-transfer mechanisms of adhesive layers are analyzed. The experimental outcomes indicate that the maximum tensile stresses of Fe-SMA plates can reach 61 % of their ultimate strength. The failure modes and ultimate load of Fe-SMA/steel SLJs are affected by adhesive types. Interface failure occurs in CH 120 and PCMdur™-15 specimens, whereas interface, cohesive and mixing failure are formed in Sika 31 specimens. Due to the adverse effects of adhesive layer defects, out-of-plane bending moment, and damage accumulation of the adhesive layers, the distribution of surface strain and interfacial shear stress of all specimens are mainly at the effective overlap zone. For an efficient engineering design, the linear and polynomial fitting models of cohesive zone models with different adhesive types and adhesive layer thicknesses are proposed based on experiments. The experimental and theoretical achievements can provide design recommendations for deteriorated steel structures rehabilitated by bonding Fe-SMA.

The interfacial behavior of an axisymmetric film bonded to a graded inhomogeneous substrate

With the development of high-tech applications such as thermal barrier coatings, stretchable and flexible electronics, etc, the key film/substrate systems are more commonly involving three-dimensional axisymmetric problems with graded inhomogeneous substrates. In these film/substrate systems, the effects of geometric and material factors of both the films and the substrates on the interfacial behavior are urgently needed to be uncovered. Herein, a novel theoretical axisymmetric model of an elastic film bonded to a graded substrate is proposed and solved by using Hankel integral transformation and orthotropic polynomials. The interfacial shear stress and the corresponding shear stress intensity factor as well as radial stresses and hoop stresses of both the film and the graded substrate are obtained. It is found that the present model works well to predict the interfacial behavior between an axisymmetric film and a graded substrate. Compared with cases with homogeneous substrates, choosing graded substrates can reduce the risk of edge fracture on the surface of the substrate. A film with a smaller elastic modulus and thickness is advantageous for the interface reliability of the film/substrate system under a thermal load. The results should be useful for not only understanding the load transfer mechanism of axisymmetric film/substrate system, but also providing a valuable guidance to optimize film/substrate structures in various practical and potential applications.

Interface stress analysis and bonding strengthening exploration of metal layer on the laser-activated copper-clad AlN

Aluminum nitride ceramics has excellent thermal conductivity and insulation property, making it a kind of excellent electronic packaging material. But enhancing the bonding strength between the metal layer and aluminum nitride (AlN) ceramic is a challenging problem. Especially regarding the lack of accurate data analysis on the stress between interfaces, enhancing adhesive strength still relies on blind attempts. By using the finite element method, this study reveals that the shear stress generated between the metal/ceramic interface is concentrated at the interface edge. Based on this finding, a method of inserting micro-pore arrays at the edge is proposed to enhance the interfacial bonding strength. The simulation results show that by inserting micro-pores with an appropriate density, the interface shear stress between metal and ceramic can be reduced obviously by 36 %. Finally, vertical peel-off verification experiments were designed. After inserting micro-pores to the interface, the bonding strength of the interface increased from 8.75 MPa to 11.69 MPa, and the performance was improved by 33.6 %. The experimental results were consist with the simulation results and indicated that the micro-pores had a significant effect on improving the bonding strength.

On the Thermally Induced Interfacial Behavior of Thin Two-Dimensional Hexagonal Quasicrystal Films with an Adhesive Layer

The mechanical response of a quasicrystal thin film is strongly affected by an adhesive layer along the interface. In this paper, a theoretical model is proposed to study a thin two-dimensional hexagonal quasicrystal film attached to a half-plane substrate with an adhesive layer, which undergoes a thermally induced deformation. A perfect non-slipping contact condition is assumed at the interface by adopting the membrane assumption. An analytical solution to the problem is obtained by constructing governing integral–differential equations for both single and multiple films in terms of interfacial shear stresses that are reduced to a linear algebraic system via the series expansion of Chebyshev polynomials. The solution is compared to that without adhesive layers, and the effects of the aspect ratio of films, material mismatch, and the adhesive layer, as well as the interaction between films, are discussed in detail. It is found that the adhesive layer can soften the localized stress concentration. This study is instructive to the accurate safety assessment and functional design of a quasicrystal film system.

Grouped rubber-sleeved studs–UHPC pocket connections in prefabricated steel–UHPC composite beams: Shear performance under monotonic and cyclic loadings

Prefabricated steel–ultra-high-performance concrete (UHPC) composite beams (PSUCBs) with grouped stud–UHPC pocket connections (GSUPCs) are a successful attempt of UHPC in bridge engineering, which offers significant advantages in accelerating on-site construction, enhancing structural performance, and improving environmental benefits. However, the uneven steel–concrete interfacial shear stresses distribution caused by the insufficient deformability of ordinary studs (OSs) in UHPC may result in the premature stud failure in large interfacial slippage regions. To address this issue, rubber-sleeved studs (RSSs) that wrapped rubber-sleeves around the stud roots were introduced to improve ductility and reduce the stiffness of connectors. However, the shear performance of grouped RSSs embedded in UHPC remains unclear, which hinders their application in practices. Against this background, systematic experimental and numerical studies were conducted to investigate the monotonic and cyclic shear performance of grouped RSSs–UHPC pocket connections. The results indicated that wrapping rubber-sleeve could increase the ultimate slip capacity and remained sufficient shear resistance, demonstrating great potentials of grouped RSSs–UHPC pocket connections in PSUCBs. Increasing the rubber-sleeve thicknesses and height effectively improved the ultimate slip capacity and deformation recovery, but led to the significant plastic deformation accumulation and cyclic stiffness degradation. Finally, design recommendation on rubber-sleeve configuration rationalization, ultimate shear resistance and load–slip relationship predictive models were provided.

Influence of the thickness of pyrolytic carbon interphase on the mechanical behavior of SiC/(BN/PyC)/SiC composites

The composition and thickness of the interphase are critical factors affecting the strength of SiC/SiC materials. Therefore, SiC/(BN/PyC)/SiC ceramic matrix composites with varying PyC thicknesses were fabricated, and the mechanism by which thickness influences the mechanical properties of the materials was investigated. During the fracture process of the composites, debonding and crack deflection predominantly occurred at the BN/PyC interface. The PyC interphase thickness emerged as a critical factor influencing the mechanical performance of composites. The residual stresses within the PyC and its adjacent SiC matrix were determined by analyzing shifts in Raman peak positions. The findings indicate that a reduction in PyC thickness leads to an increase in residual compressive stress within the PyC and a corresponding increase in residual tensile stress within the SiC matrix, which increases the interfacial shear stress and improves the mechanical properties of the composites.

Subduction plate interface shear stress associated with rapid subduction at deep slow earthquake depths: example from the Sanbagawa belt, southwestern Japan

Abstract. Maximum shear stress along an active deformation zone marking the subduction plate interface is important for understanding earthquake phenomena and is an important input parameter in subduction zone thermomechanical modeling. However, such maximum shear stress is difficult to measure directly at depths more than a few kilometers and is generally estimated by simulation using a range of input parameters with large associated uncertainties. In addition, estimated values generally represent maximum shear stress conditions over short observation timescales, which may not be directly applicable to long-timescale subduction zone modeling. Rocks originally located deep in subduction zones can record information about deformation processes, including maximum shear stress conditions, occurring in regions that cannot be directly accessed. The estimated maximum shear stress is likely to be representative of maximum shear stress experienced over geological timescales and be suitable to use in subduction zone modeling over timescales of millions to tens of millions of years. In this study, we estimated maximum shear stress along a subduction plate interface by using samples from the Sanbagawa metamorphic belt of southwestern (SW) Japan, in which slivers of mantle-wedge-derived serpentinite are widely distributed and in direct contact with metasedimentary rocks derived from the subducted oceanic plate. These areas can be related to the zone of active deformation along the subduction plate interface. To obtain estimates of maximum shear stress at the subduction interface, we focused on the microstructure of quartz-rich metamorphic rocks – quartz is the main component of the rocks we collected and its deformation stress is assumed to be roughly representative of the stress experienced by the surrounding rock and plate interface deformation zone. Maximum shear stress was calculated by applying deformation temperatures estimated by the crystallographic orientation of quartz (the quartz c-axis fabric opening-angle thermometer) and the apparent grain size of dynamically recrystallized quartz in a thin section to an appropriate piezometer. Combined with information on sample deformation depth, estimated from the P–T (pressure–temperature) path and deformation temperatures, it is suggested that there was nearly constant maximum shear stress of 15–41 MPa in the depth range of about 15–30 km, assuming plane stress conditions even when uncertainties related to the measurement direction of thin section and piezometer differences are included. The Sanbagawa belt formed in a warm subduction zone. Deep slow earthquakes are commonly observed in modern-day warm subduction zones such as SW Japan, which has a similar thermal structure to the Sanbagawa belt. In addition, deep slow earthquakes are commonly observed to be concentrated in a domain under the shallow part of the mantle wedge. Samples showed the depth conditions near the mantle wedge, suggesting that these samples were formed in a region with features similar to the deep slow earthquake domain. Estimated maximum shear stress may not only be useful for long-timescale subduction zone modeling but also represent the initial conditions from which slow earthquakes in the same domain nucleated.

Design of Porous Partition Elastomer Substrates for the Island–Bridge Structures in Stretchable Inorganic Electronics

Abstract Stretchable inorganic electronics have been of growing interest over the past decades due to their various attractive potential applications. The island–bridge structure is the most widely used structural design, where rigid inorganic devices (islands) and interconnects (bridges) are attached to an elastomer substrate, and large deformations in the structure are accommodated by the large stretchability of the interconnects and the elastomer underneath them. Due to the large modulus mismatch of more than five orders of magnitude between the rigid island and elastomer substrate, there is a severe stress and strain concentration at the interface between the island and the substrate during large deformations, which may cause the interface fracture and delamination. In this work, the analytical solution of the interfacial shear and peel stress between the island and the substrate is derived to reveal the mechanism of interface fracture and agrees well with finite element analysis (FEA) results. A simple porous partition substrate design strategy is proposed to alleviate this stress and strain concentration at the boundary of the interface, where the porous region can undergo larger deformation due to the reduced stiffness of the material. FEA obtains the key parameters affecting the pore layout. The digital image correlation (DIC) experiment verifies the design strategy. The results show that, compared to the solid substrate, the porous partition substrate strategy can significantly reduce the maximum normal strain of the substrate around the island, thus effectively reducing the risk of structural interface failure.

Calculation and Analysis of Load Transfer Characteristics of Tensile Anchors for Geotechnical Anchoring Systems

In order to explore the problems of load transfer and anchorage mechanisms of tensile anchors under pull-out load for geotechnical anchoring systems, a step-wise mathematical model is established which considers the linear–nonlinear shear stress and shear displacement of the anchorage segment, using an elasto-plastic constitutive model. The displacement, axial force, and shear stress of the anchorage interface in different stages (elastic, plastic, and debonding) are analyzed and solutions are derived. And the theoretical solutions for the ultimate pull-out load of the anchor at each stage are also presented. Two in situ pull-out tests are used to verify and apply these findings in engineering. The results show that the stepwise composite model could reflect the bonding, softening and residual characteristics of the anchoring interface. In the process of the pull-out load increasing, the pulling end of the anchor initially enters the plastic stage and the debonding stage, respectively, and the failure of the anchor occurs at the pulling end, and as the axial force transfers down deeper, the damage gradually spreads deeper. The axial force distribution of the anchorage section is a monotonically decreasing curve, and the peak point of the shear stress gradually moves deeper. The calculation results of the axial force distribution curve and load–displacement curve of the anchor are in good agreement with the measured values, which verifies the rationality and reliability of the theoretical prediction method. This method can provide a theoretical reference for the load transfer analysis and design of tension anchors for geotechnical anchoring systems.

Analysis of transverse constraint force mechanics of anchor rods based on higher order theory

Abstract Research on the mechanical properties of transverse constraint force of anchor support under different loads can help to improve work safety. In this paper, based on the higher-order shear deformation theory, the higher-order whole-local theory of anchor rods is established with full consideration of the transverse normal strain. The geometric and physical equations in the intrinsic relationship are given for the wet thermodynamic behavior of anchor rods’ transverse restraining force. The equilibrium equations of the whole-local are constructed by combining them with the principle of virtual displacement. The analytical solution of the anchor core material was calculated by applying Navier’s method. The boundary displacement conditions of the anchor core material were solved. The anchor core material was modeled by combining it with ABAQUS finite element software. The mechanical analysis was carried out from the two perspectives of the buckling problem under thermal load and the parameter change of the transverse restraining force, respectively. It was found that when the thickness of the anchor bar increased from 20 mm to 50 mm, the radial displacement of the upper layer decreased by 52.95%, and there was no significant change in the positive stress at the upper and lower interfaces. The peak value of the upper interface shear stress decreases significantly from 0.55MPa to −1.41MPa when the anchor laying method is changed from a single layer to four layers. The combination of higher-order theory with ABAQUS software can effectively analyze the change of transverse constraint force of the anchor support, which can help improve its safety.

Hydro-mechanical analysis of water-induced pothole patch failure in asphalt pavement

Pothole repair is one of most common roadway maintenance to improve driving comfort and reduce safety risk. This study aimed to conduct hydro-mechanical analysis of water-induced pothole patch failure in asphalt pavement. Three-dimensional finite element models are used to analyze the coupled hydraulic and mechanical responses of surface patching under moving traffic loading considering different wheel path locations and asphalt patch sizes. The model results under dry and saturated conditions were validated against field measurements and simulation results from the literature, respectively. Laboratory tests were conducted to measure dynamic modulus and permeability of asphalt patch material. Analysis results show that regardless of patch size and wheel path, the maximum pore water pressure occurs either at the patch body or the interface between the patch and surrounding pavement when traffic loading approaches the pothole. The hydraulic scouring effect was observed with positive and negative pore pressure under moving loads. The maximum interface shear stress at the interface between the patch and surrounding pavement under traffic loading was found close to the bonding strength, especially for big-shallow patch. The comparison of asphalt patch responses at dry and saturated conditions indicates that water intrusion mainly accelerates edge disintegration of pothole patch.

An analytical model to predict bond behavior of fiber reinforced polymer bonded to concrete with an end anchorage system

The end mechanical anchorage system has been widely applied in the conventional externally bonded reinforcement (EBR) technology, to hinder the premature debonding failure of fiber reinforced polymer (FRP) laminate, especially for the reinforcement structures with prestressed FRP due to higher interfacial shear stress at the ends. Through the introduction of the hinge as the substitution of end anchorage, this paper presents a numerical model based on the bilinear bond-slip model and ordinary differential equations in elastic, elastic-softening, and elastic-softening-debonding stages. The bond behavior of the FRP-concrete interface under the end anchorage in different stages is predicted, obtaining the analytical expressions of interfacial load-slip relation, interfacial shear stress distribution, and the stress distributions of FRP. Additionally, two experimental programs from this group and previous literature were involved in this study to validate the accuracy of the numerical model. The comparison shows they are in good agreement. Moreover, it indicated that the strength increase is linear with the torque applied in the end anchorage, but bonding strength is not the case.

Study on reasonable anchorage length based on failure mechanism of the bolt anchorage system

In addition to analysing the mechanism of failure of the prestressed rock anchor anchor system and investigating the appropriate depth for fixing the rock anchors, theoretical equations were derived to calculate the rock anchors' axial force, ultimate capacity, and the interfacial shear force in the elastic phase. These equations are then used to analyse the pressure distribution within the rock bolt anchorage section and to investigate the effect of interfacial shear strength, shear stiffness, and anchorage length on interface failure. Drawing on the findings from both field-based rock bolt pull-out tests and numerical simulations, analyzed the failure mechanism of the anchor system, and proposed a reasonable anchor length design method for rock bolt. The results show that there is a strong dependence between ultimate load carrying capability of rock bolts and interfacial shear stress and shear rigidity, and that increasing the anchorage length and reducing the interface shear stiffness can avoid the stress concentration phenomenon. The primary factor leading to the anchor system failure is secondary interface failure. The evolution law of interface damage is that the damage occurs first at the initial position. As the interface damage location changes, the peak shearing stress moves towards the bottom of the anchored section. The engineering application results verified the feasibility of a reasonable anchorage length calculation method and rock bolt design process. The findings of this paper can be used as a basic reference for determining rock bolt anchorage support parameters during the design and construction of underground engineering projects.

Investigation on interfacial shear performance of concrete strengthened with bonded steel plate

This study investigated the interfacial shear performance of concrete strengthened with bonded steel plate through tests, fracture energy based theoretical analysis and numerical simulation. Firstly, the interfacial shear bearing capacity of concrete strengthened with bonded steel plate having various lengths was experimentally investigated, and the failure mode and bearing capacity were discussed. Secondly, based on fracture theory, fictitious crack hypothesis, concrete failure criteria and bilinear linear softening shear slip model, the interfacial shear capacity was theoretically derived, including the effective interfacial shear stress transfer length, fracture energy and peak interfacial shear bearing capacity. Moreover, the interfacial shear failure behavior was also numerically simulated, and the interfacial shear stress and normal stress during the whole loading and failure process were discussed. The results confirmed that the numerical simulation using the theoretically derived interfacial fracture energy and peak shear strength could give simulation results in good agreement with experimental results. Also, the calculated interfacial bearing capacity using the theoretical approach showed excellent agreement with the experimental results. Furthermore, the influence of bonding length was also theoretically derived using the numerical parametric simulation results, and a revised interfacial shear bearing capacity considering bonding length was further proposed, which was also in good agreement with both experimental and numerical simulation results.

Shearing behavior of suction caisson wall-sand interface throughout the suction caisson life-cycle

Suction caissons are widely used as foundations for offshore platforms and offshore wind turbines. The life-cycle of a suction caisson includes penetration, service and retrieval. The mechanical characteristics of the interface between sand and suction caisson wall are crucial for assessing the penetration behavior and bearing capacity of suction caissons. Interfacial shear tests under constant normal loading (CNL) and variable normal loading (VNL) conditions were conducted to investigate the shearing behavior of suction caisson wall-sand interface throughout the suction caisson life-cycle. Results show that the interfacial shear stress increases with an increase in normal stress and decreases with an increase in penetration rate throughout the life-cycle of the suction caisson. The value of vertical displacement of the interface decreases with an increase of cycle times during service and the sand particles’ movement, rotation and rolling were observed by visualization tests. Under the test conditions, the interface frictional coefficient ranges from 0.46 to 0.80 and the interface friction angle varies between 25.64° and 27.43° during retrieval. Both the interface friction angle and interface friction coefficient during the penetration stage are greater than those during the retrieval stage, indicating that retrieval stage is not an inverse process of penetration stage. In addition, the control groups were carried out to investigate the effect of penetration on service stage and the effect of service on retrieval stage. It was also found that the influence of the penetration stage on shear stress during service stage is mainly observed in the first two cycles. The influence of service stages on shear stress during retrieval stage is more obvious. After prolonged cycling during service stage, the strength of the interface would be reduced.

Flow field analysis and particle erosion of tunnel‐slope systems under coupling between runoff and fast (slow) seepage

AbstractThe presence of particles on the surface of a tunnel slope renders it susceptible to erosion by water flow, which is a major cause of soil and water loss. In this study, a nonlinear mathematical model and a mechanical equilibrium model are developed to investigate the distribution of flow fields and particle motion characteristics of tunnel slopes, respectively. The mathematical model of flow fields comprises three parts: a runoff region, a highly permeable soil layer, and a weakly permeable soil layer. The Navier‒Stokes equation controls fluid motion in the runoff region, while the Brinkman‐extended Darcy equation governs fast and slow seepage in the highly and weakly permeable soil layers, respectively. Analytical solutions are derived for the velocity profile and shear stress expression of the model flow field under the boundary condition of continuous transition of velocity and stress at the fluid‒solid interface. The shear stress distribution shows that the shear stress at the tunnel‐slope surface is the largest, followed by the shear stress of the soil interface, indicating that particles in these two locations are most vulnerable to erosion. A mechanical equilibrium model of sliding and rolling of single particles is established at the fluid‒solid interface, and the safety factor of particle motion (sliding and rolling) is derived. Sensitivity analysis shows that by increasing the runoff depth, slope angle, and soil permeability, the erosion of soil particles will be aggravated on the tunnel‐slope surface, but by increasing the particle diameter, particle‐specific gravity, and particle stacking angle, the erosion resistance ability of the tunnel‐slope surface particles will be enhanced. This study can serve as a reference for the analysis of surface soil and water loss in tunnel‐slope systems.

Impact of fiber surface gas treatments on interfacial bonding in SiC/BN/SiC minicomposites

AbstractBN interphases with different microstructures and a structural gradient were prepared by chemical vapor deposition (CVD) within SiC/SiC minicomposites. The interfacial shear stress (ISS) measured by the fiber push‐out test and the debonding location in the fiber/matrix interface zone during mechanical loading depends on the BN interphase structure. The ISS is higher when the structural organization of the BN interphase is poor, in which case debonding occurs on the fiber side. The Hi‐Nicalon S fiber surfaces were gas‐treated to strengthen the bond with the interphase. BCl3‐based reactive CVD treatments have produced a thin boron carbide layer on the fiber surface, resulting in a 30% increase in ISS. However, the minicomposites are brittle in tensile tests due to fiber bridging by parasitic boron clusters. Short‐time CVD of SiC increases the fiber surface roughness and doubles the ISS, but again the minicomposites are brittle, indicating the need to better modulate the resulting roughness and adjust the interphase. Finally, ammonia treatments have nitrided the fiber surface and increased the ISS by 12%. While the increase in interfacial bonding measured at the microscopic scale was small, this nitriding treatment did not embrittle the minicomposites at the macroscopic scale.

Interfacial properties of carbon fiber‐reinforced biobased resin composites by single fiber fragmentation, fiber push‐out, and interlaminar shear strength

AbstractThe present study examines the interfacial properties of carbon fiber biobased resin composites by comparing the test methods such as the single fiber fragmentation test, fiber push‐out test, and interlaminar shear strength test. The composites were fabricated using a cold vacuum‐assisted resin infusion method for the preparation of fiber push‐out and interlaminar shear test specimens. The interfacial adhesion from the three different test methods is analyzed and compared to determine their relative effectiveness in evaluating interfacial adhesion. Plasma treatment is performed on the carbon fibers and the interfacial shear stress is evaluated by conducting the push‐out test. The surface characterization of the carbon fibers is done by scanning electron microscopy and x‐ray photoelectron spectroscopy to investigate the influence of the plasma treatment on the fiber surface. Plasma treatment resulted in significant improvement in the interfacial adhesion between the fiber and matrix.Highlights Analysis and comparison of interfacial adhesion by several test methods. Single fiber fragmentation and push‐out tests with IFSS of 40.5 and 42.2 MPa. Plasma surface treatment improved the IFSS by 88.1%. Surface characterization of treated and untreated fibers by SEM and XPS.

Temperature-dependent mechanical properties of graphene nanoplatelet reinforced polymer nanocomposites: Micromechanical modeling and interfacial analysis

One of the challenges to be addressed in the reasonable prediction of the mechanical properties of nanocomposites at elevated temperatures is the quantitative characterization of the temperature-dependent interfacial behavior. In this study, the temperature-dependent mechanical properties for graphene nanoplatelets (GNPs) reinforced polymer-matrix nanocomposites are modeling based on the nonlinear interfacial shear stress transfer mechanism. Besides, the influence of interfacial debonding, polymer matrix plasticity, thermomechanical parameters of components, and their evolution with temperature, as well as the orientation, dimensions and volume fractions of GNPs is considered. The Young's modulus, yield/ultimate strength, and stress-strain relationships at elevated temperatures are predicted and are verified by the available experimental data. Compared to the extended room-temperature models previously established, the proposed model considering the microscopic structures achieves higher prediction accuracy with only basic material parameters input. Furthermore, the temperature-dependent interfacial mechanical behavior is analyzed. The initial strain of debonding and the maximum debonding ratio of the interface at elevated temperatures are calculated. The micromechanical modeling establishes the quantitative relationships between the temperature-dependent interfacial behavior and the mechanical properties of nanocomposites. This study deepens the understanding of the mechanical behavior of the interface and their evolution with temperature, which contributes to the prediction of the high-temperature mechanical performance and reliability analysis of nanocomposites.