Interfacial Shear Strength Research Articles

Significantly improved interfacial and overall mechanical properties of aramid fiber/phenolic resin matrix composite reinforced with short CNT

Aramid fiber-phenolic matrix composite laminates reinforced with carbon nanotubes (CNT) were developed, and their interfacial and mechanical properties were systematically investigated. Results revealed that short length of the CNT (≤1 μm in average length) (Short CNT) was critical to the performance of the laminates. Long CNT (∼10 μm) cannot effectively improve the properties of the laminates. Excellent dispersion and functionalization of the CNT are also conduced to improve the properties. The laminates reinforced with 3.0 wt% of the short/carboxylic functionalized CNT (Short CNT-COOH) in the phenolic matrix showed improvements of 17.7%, 49.6% and 22.3% in tensile strength, modulus and flexural strength, respectively, as compared with the control sample without CNT. No obvious improvement of the properties was seen based on Long CNT reinforcement. The interfacial shear strength and the wettability between the single aramid fiber and the matrix were significantly improved with CNT reinforcement. A detailed analysis was performed and reported.

Impact of Mendong fiber–epoxy composite interface properties on electric field frequency exposure

AbstractThis research investigates the effects of the frequency of the external electric field during the curing process on the interfacial properties of epoxy composites reinforced by Mendong fiber. Epoxy was used as a matrix with cycloaliphatic amine as a curing agent. The AC electric field by frequencies of 1, 2, and 3 kHz and strength of 750 V/cm were applied during the curing process. The functional groups, structure, interface properties, and morphology of treated epoxy were observed using Fourier‐transform infrared, x‐ray diffraction, scanning electron microscope, and pull‐out test, respectively. The result indicates that after treatment with an electric field of 1 kHz, new peaks were observed in the epoxy diffractogram at the angle of 6.2° and 12.3°, change in morphology, the wettability properties of epoxy were increased and interface shear strength was improved. Increasing the frequency of electric fields results in more damage to the interface and subsequently reduces the shear strength at the interface.Highlights Interface properties of the composite after curing in an electric field characterized. Exposure to electric field frequency during curing changed epoxy properties. Shear strength of Mendong fiber/epoxy varied post‐exposure to the electric field.

Improved dielectric and mechanical properties of aramid fiber reinforced epoxy resin composites by polyethyleneimine grafting

In this paper, aramid fiber surface is modified by polyethylenimine (PEI) grafting with abundant -NH2 active groups after plasma surface activation treatment. Various aramid fiber reinforced epoxy resin composites (AFRC) are prepared. The effects of PEI grafting on the dielectric and mechanical properties of AFRC are studied. Obtained results show that PEI is successfully grafted onto aramid fiber surface as evidenced by x-ray photoelectron spectroscopy results, and effectively improves the interfacial properties between aramid fiber and epoxy resin. The dielectric properties, including DC conductivity, dielectric constant, and integration charge Q(t) of the composites are improved after optimized modification parameters, and the breakdown strength is increased by up to 23%. These are attributed to the decrease in interfacial polarization and the increase in interfacial bonding strength. Furthermore, the interfacial shear strength of AFRC is increased from 29.5 MPa to 63.7 MPa, which further verifies the improvement of interfacial performance. This paper provides a way to improve the dielectric and mechanical properties of AFRC, which is of great significance for its application in high voltage power equipment.

Preparation Method and Properties of Q235/5083 Composite Plate with 1060 Interlayer by Differential Temperature Rolling with Induction Heating

Due to their exceptional all-around performance, steel/aluminum-alloy composite plates have been frequently utilized in many different industries. However, when steel/aluminum-alloy composite plates are prepared by the rolling process, they will scarcely bond with high bonding strength under a lower reduction rate due to the inconsistent deformation the of steel/aluminum-alloy. Therefore, a method of adding a pure-aluminum interlayer by differential temperature rolling with induction heating was proposed to prepare steel/aluminum-alloy composite plates. The results showed that when the induction heating time was 10–18 s, the pure-aluminum interlayer became molten, and the temperature difference between the steel and aluminum alloy reached 350–500 °C. The interface shear strength of the composite plate reached more than 68 MPa under a 31% reduction rate. The shear fracture of the composite plate occurred in the pure-aluminum layer, and the steel/aluminum interface diffusion layer was 0.83–0.99 μm thick. There was no obvious compound formation at the bonding interface, however, the steel and aluminum alloy could not bond without the addition of an interlayer under the same conditions.

Shear behaviors of engineered cementitious composites to seawater sea-sand concrete (ECC-to-SSSC) interfaces cast using 3D-printed pre-grooving formwork: Mechanical properties, characterization, and life-cycle assessment

This paper aims to investigate shear behaviors of engineered cementitious composites to seawater sea-sand concrete (ECC-to-SSSC) interfaces cast using 3D-printed pre-grooving formwork. The investigation involves experimental tests and economy/environmental analysis. The investigated parameter includes concrete types, interface roughness, and ECC compressive strength. A novel and eco-efficient interface treatment method was developed using 3D printing pre-grooving formworks, and an accurate interface roughness quantification method was proposed. The interface shear test was conducted to obtain shear load-slip curves and interfacial shear strengths. The characterization results showed that, ECC-to-SSSC interfaces contained Frieda's salt, which improved hydration rate and generated more hydration products to enhance interface strength. Moreover, economic/environmental analysis showed that the use of SSSC, ECC, and 3D-printed pre-grooving formwork greatly reduced life-cycle cost, carbon footprint, and energy consumption. This study is promising to enhance the understanding of interfacial behaviors of ECC-to-SSSC interface and mitigate material cost and carbon footprint in concrete.

Sliding behavior at the graphene oxide and polyethylene interface

Harnessing their excellent physical attributes, two-dimensional nanostructures have gained prominences as reinforcements in polymer nanocomposites. Given the intricate structure of nanofillers and the varied interfacial connections, in-depth understanding of the strengthening mechanisms becomes pivotal for optimizing nanocomposite design. By varying the GO's morphology, a notable divergence of approximately 30% is evident in the interfacial shear strength. This divergence is attributed to the mechanical interlocking effect instigated by the presence of -O- and -OH functional groups. Functionalizing with groups like -CH3-CH2-NH2 (-Ethylamine) and -(HOCH2)3CNH2 (-TRIS) enhances the mass density of PE polymers at the interphase, which changes the interface sliding (low-density interphase) to the cohesive sliding during the pull-out process. As a result, the maximum interfacial shear strength (204–223 MPa) of these two samples is much larger than that of the pristine GO/PE (149–151 MPa), and even comparable with the pure PE's tensile strength. Intriguingly, shorter or highly flexible functional group exhibit a comparatively weaker influence on the interfacial shear strength. Moreover, as the sliding surface shifts toward the cohesive zone, diminishing sample thickness (less than 60 Å) generally corresponds to augmented interfacial shear strength due to the boundary confinement effect. In summary, this work offers a comprehensively elucidation of GO/PE pull-out behavior, facilitating the design of nanocomposites with exceptional mechanical performance.

Promotion of crystallization of polyamide 6 at an interphase and a mechanical interlocking effect at an interface due to surface irregularities of carbon fibers

The effect of surface irregularities in the carbon fiber (CF) axial direction on the interfacial properties of polyamide 6 (PA6) was investigated using CFs with different amounts of oxygen functional groups on the surface, that is, chemical reactivity. The interfacial shear strength between PA6 and CF was measured using the microdroplet method. The crystal structure of PA6 at the interphase was characterized using unpolarized and polarized micro-Raman spectroscopy and polarized light microscopy. Not only the chemical interactions at the interface but also the surface irregularities of the CF were found to contribute to the formation of oriented crystals of PA6 in the CF axial direction at the interphase, and these oriented crystals of PA6 at the interphase enhanced the interfacial shear strength. The surface irregularities of the CF were found to cause mechanical interlocking effects. This study demonstrates the importance of CF surface irregularities in controlling interfacial properties.

Synergistically enhanced interfacial and wave-transparent properties of PBO fiber composites: Constructing self-assembly interphase with different dimensional COF

Naphthalimide-linked covalent organic framework (COF) with two-dimensional (A-COF and B–COF) and three-dimensional structure (M-COF) was designed and applied to self-assembly on PBO fiber surface, and the influences of 2D or 3D COF on interfacial and wave-transparent properties as well as their reinforcing mechanisms of composites were investigated. A-COF and M-COF exhibited higher BET surface area and porosity compared to those of B–COF, and the morphology of 2D and 3D COF respectively presented lamellar nanosheet and random particle aggregation. The dense inner COF layer and numerous nanocrystals were attached on 2D COF@PBO fiber, and 3D COF@PBO fiber surface showed nano-porous structures from M-COF nanoparticle stacking. Compared with pristine PBO fiber composites, transverse fiber bundle tensile (TFBT) strength and interfacial shear strength (IFSS) of A-COF@PBO and B–COF@PBO fiber composites were increased by 38.76% and 51.77%, 37.23% and 43.94% due to lamellar stacking structure of 2D COF, while 15.31% and 19.56% increment for M-COF@PBO fiber composites, which was attributed to the weaker binding force between PBO fiber and 3D COF from interpenetrated structure. The optimal wave transmission efficiency (|T|2) at low frequency was obtained for A-COF@PBO fiber composites, resulting from the highest porosity of A-COF and best interfacial compatibility, while M-COF@PBO fiber composites showed the best |T|2 at high frequency due to the higher porosity and scarce electron-coupling phenomenon of M-COF.

INVESTIGATION INTERFACIAL SHEAR STRENGTH AND MECHANICAL PROPERTIS OF ALKALI TREATED HONEY PINEAPPLE FIBER/ MICROCRYSTALLINE CELLULOSE COMPOSITE

The research objective was investigate the effect of alkali treatment on thermal stability, interfacial shear strength, mechanical properties and waterabsorption in composite of honey pineapple fiber (HPF). HPF was not given and treated by soaking in a mixture of 6% wt sodium hydroxide. Mixing between Unsaturated Polyester (UPRs) and Microcrystalline Cellulose (MCC) applied the Taguchi test with 5% MCC, 250 RPm, 40 oC temperature, and 30 minutes. The composites were mold using the vacuum infusion method and curing at 60 o C for 120 minutes. Interfacial shear strength test showed 9 hours of immersion, gave strength of 3.49 MPa, an increase of 37.39%. Tensile strength increased by 30.4%,the flexural strength of the composite increased by 51.08%. The results of the SEM test showed the fiber untreated was still smooth and there were several interface gaps. The water absorption test showed that the untreated fiber had a higher absorption rate.

Comparative Assessment of Single- and Double-Interface Shear Tests of MSW Landfill Liners Using Large Direct Shear Equipment

Geosynthetics form an integral part of engineered municipal solid waste (MSW) landfill lining systems, as they provide cost saving and technical benefits. Their introduction in lining systems, however, has presented new potential interfaces for shear failure especially on bases and on side slopes of engineered MSW landfills. In the laboratory, interface shear strength parameters used in slope designs of landfill lining systems are determined through single-interface testing configurations as per ASTM D5321-20 and D6243-20 standards. However, single-interface testing configurations do not provide a clear understanding of shear strength transfers among the lining components and does not aid in pin-pointing the interface facilitating failure especially when a multi-layered lining system has been proposed. Multi-interface testing configurations present an alternative that may address such limitations. But there is minimum information available on this type of testing as it is not stipulated in any official laboratory testing standard. This study was conducted to provide an understanding of the potential use of multi-interface testing configurations of MSW landfill liners, through identifying similarities and dissimilarities to the single-interface testing configurations. These interface tests were conducted on geosynthetics and geomaterials from a proposed lining system of a new landfill cell in South Africa.

Enhancement of interfacial adhesion to carbon fibers via electrostatic interaction using polyvinyl chloride as a model matrix

The purpose of this study is to provide a framework for spectroscopic investigation of an enhancement mechanism of the interfacial adhesion using a polyvinyl chloride (PVC) matrix as a model. PVC dissolved in a tetrahydrofuran solution was dropped onto carbon fiber (CF) or glass fiber (GF), and the interfacial shear strength was measured after annealing at various temperatures. The interfacial shear strength of PVC/CF increased significantly with the annealing temperature compared with that of PVC/GF. As characterized by Raman spectroscopy, the polyene content (an indicator of PVC degradation) in bulk PVC was positively correlated with the interfacial shear strength. PVC radicals were not detected at the annealing temperature in the electro spin resonance spectroscopy. It was demonstrated that the interaction between the ions (C+Cl−) formed during the decomposition of PVC (formation of polyene) and the π electrons in the benzene of CF; the cation–π interaction is attributable to the enhancement of the interfacial shear strength.

A novel bio-based hyperbranched waterborne polyurethane sizing agent with superior UV-resistance and interfacial properties for CF/PA6 composites

On account of environment concerns and the gradually depletion of fossil resources, a hyperbranched waterborne polyurethane (HWPU) serving for sizing agent of carbon fibers (CF) was designed based on bio-based materials. Hyperbranched chain extender named CAG was synthesized by citric acid (CA) and glycerol as HWPU precursor. Tartaric acid (TA) was coordinated with nano titanium dioxide (TiO2) through two –COOH groups, which was introduced to HWPU as the chain extender, leading to a significant improvement in ultraviolet (UV)-resistant of the sizing agent. The interfacial performance promotion of CF reinforced nylon 6 (CF/PA6) composites contributed by the HWPU sizing agent were systematically investigated. In contrast to the untreated CF composites, the mechanical performance arrived the best improvement after sizing by concentration of 1.5 wt%, which exhibited a dramatic promote of 44.9% in interlaminar shear strength (ILSS), 58.7% in interfacial shear strength (IFSS) and 43.3% in flexural strength. Extraordinary, the treated CF composites remained over 98% of mechanical performance after a week of unremitting ultraviolet irradiation, signifying the outstanding UV-resistance of the TiO2 modified HWPU sizing agent.

Effect of vacancy defects of graphene on the interfacial bonding and strengthening mechanism of graphene/Al composite

The structure and properties of the graphene-Al interface change significantly when defects are present in graphene. However, the effect of defects on interfacial bonding lacks quantitative assessment, and the results of theoretical studies are also difficult to guide the design of interface structures. In this paper, the interfacial structure of graphene-Al with different vacancy defect types has been investigated by first-principle calculations, and the interfacial bonding was calculated by quantifying the interfacial shear strength. The interfacial shear strengths of defect-free, single-vacancy, and double-vacancy were 0.02 GPa, 6.8 GPa, and 8.5 GPa, respectively. Based on the first-principles data and the differential idea, the calculation model of shear strength of graphene-Al interface with different defect contents was established. The role of vacancy defects on the enhancement of graphene-Al interfacial bonding was elucidated. A method to estimate the shear strength of graphene-Al direct bonding interface based on Raman characterization of graphene defects was proposed. The influence of graphene defects on graphene strengthening efficiency was clarified, and an apparent strengthening model applicable to directly bonded interfacial graphene/aluminum composites was established. The model was validated by graphene/Al composites with directly bonding interface.

Assessment of the interface shear strength between HDPE geomembrane and tropical soil by the direct shear test

Liners are important impermeable constituents of sanitary landfill to contain the transport of pollutants to the unsaturated zone. The system can be made of different kind, being the compacted soil and geosynthetics widely used. Thus, knowing the interface shear strength of those materials is important to avoid rupturing the system. The purpose of this paper is to compare the shear strength in the geomembrane-soil interfaces by the direct shear test. Assays were performed under the dry and saturated condition (water and leachate). The used soil is a colluvial, lateritic, tropical silty sand-clay, typical of the city of Campinas, in Brazil. In this work, high density polyethylene (HDPE) 2,00mm geomembrane, smooth and two texturized – with different roughness level - were used. It was found that the shear strength is directly influenced by the roughness of the geomembrane, showed higher friction angle in the textured geomembrane. The direct shear test, performed with soil contaminated by leachate showed smaller friction angle than uncontaminated soil.

Effect of surface modification on interfacial behavior in bioabsorbable magnesium wire reinforced poly-lactic acid polymer composites

The mechanical behavior, corrosion mechanisms, and cytocompatibility at the interface of magnesium wires reinforced poly-lactic acid polymer composites were studied by in vitro degradation study of 180 days. Surface modification of Mg wires by plasma-electrolytic oxidation improved the interface shear strength from 10.9 MPa to 26.3 MPa which decreased to 8 MPa and 13.6 MPa in Mg/PLA and PEO-Mg/PLA composites, respectively, after 42 days of in vitro degradation. Cross-sections of the composite showed good cytocompatibility, although the cells tended to migrate towards the PLA regions and avoided the surface of the Mg wires. Corrosion of Mg wires (without surface modification) was very fast in composite while corrosion of surface-modified Mg wires was significantly reduced, hydrogen gas was suppressed and only 3% mass loss of Mg wires was found after 180 days. Finally, the corrosion mechanisms at interface were discussed for both composites.

Synergetic surface modification of 3D braided carbon fiber-reinforced composites for enhancing mechanical strength

Excellent interfacial bonding contributes to the reduction of internal defects in composites for enhancing the mechanical properties of the 3D braided carbon fiber reinforced composites. In this paper, the effects of plasma and strong acid treatment on the surface morphology, chemical composition, and surface free energy of original carbon fiber braid (CFB) were investigated in detail to reveal the mechanism of synergetic enhancement of surface wettability of carbon fiber by plasma and strong acid. The results showed that the synergetic effect of plasma and strong acid produced significantly improved the resin/fiber interfacial bonding. The interfacial shear strength (IFSS) of the carbon fiber braided reinforced composites (CFBC) treated with the synergetic treatment was 64.6% higher than that of the untreated fiber reinforced composites. The improved interfacial properties increase the polar functional groups on the fiber surface to promote the formation of mechanical interlocking caused by Cassie-Baxter(CB) and Wenzel(WZ) leaps of liquid resin on the fiber surface, and this was verified by molecular dynamics(MD) simulations of carbon fiber-resin interfacial wetting. The simple and effective synergetic reinforcement strategy proposed in this paper can effectively regulate the interfacial bonding and is applicable to the optimal design of original carbon fiber braided reinforced composites.

Effect of helium bubbles on the interface shear strength of copper/niobium multilayer

The influence of the helium bubble on the interfacial shear strength of copper/niobium multilayers and the corresponding deformation mechanisms are studied through molecular dynamics. Strong anisotropy of the shear strength is demonstrated, and the ratio of the highest strength to the lowest is approximately 4.3. The interface bubble leads to the dislocation emission under the shear along the high-strength directions and results in the severe decrease of the interface bearing capability, while the loss of the interface bearing is negligible for the case along the weak/medium-strength directions. The contradictory effects of the bubble on the interface shear strength under different shear directions are explained by the competition between the bubble-related dislocation emission and propagation and the regular uniform interface slip. For the shear along the high-strength direction, the interface could bear relatively high shear stress which is large enough to activate the dislocation from the bubble. Consequently, the corresponding deformations are dominated by the mechanism of bubble-related dislocation emission and its propagation. For the shear along the weak/medium-strength direction, the interface itself is sheared under relatively low shear stress before the effective nucleation of dislocation. Therefore, the corresponding deformation mechanism is controlled by the regular interface shear.

Using Nitroxides to Enhance Carbon Fibre Interfacial Adhesion and As An Anchor for "Graft to" Surface Modification Strategies.

Nitroxide groups covalently grafted to carbon fibres were used as anchoring sites for TEMPO-terminated polymers (poly-n-butylacrylate and polystyrene) in a "graft to" surface modification strategy. All surface modified fibres were evaluated for their physical properties, showing that several treatments had enhanced the tensile strength and Young's modulus compared to the control fibres. Up to an 18% increase in tensile strength and 12% in Young's modulus were observed. Similarly, evaluation of interfacial shear strength in an epoxy polymer, showed improvements of up to 144% relative to the control sample. Interestingly, the polymer grafted surfaces showed smaller increases in interfacial shear strength compared to surfaces modified with a small molecule only. This counterintuitive result was attributed to incompatibility, both chemical and physical, of the grafted polymers to the surrounding epoxy matrix. Molecular dynamics simulations of the interface suggest that the diminished increase in mechanical shear strength observed for the polymer grafted surfaces may be due to the lack of exposed chain ends, whereas the small molecule grafted interface exclusively presents chain ends to the resin interface, resulting in good improvements in mechanical properties. This article is protected by copyright. All rights reserved.

The Effect of the Cu Interlayer on the Interfacial Microstructure and Mechanical Properties of Al/Fe Bimetal by Compound Casting.

Al/Fe bimetals prepared by a compound casting method, combining the excellent properties of both the Al alloy and the ductile cast iron, exhibit great potential for application in achieving engine weight reduction. However, the problem of insufficient interfacial bonding ability because of the difference in thermophysical properties of Al and Fe is particularly prominent. Therefore, in this work, the electrodeposited Cu coating on the surface of the Fe matrix was used as the interlayer of Al/Fe bimetal fabricated by coupling hot-dipping with compound casting to solve the above problem. The effect of Cu interlayer thickness on the interfacial microstructure and shear strength of bimetal was investigated. The experimental results showed that the shear strength up to 77.65 MPa in regard to Al/Fe bimetal with a 5 μm Cu interlayer was obtained. No Cu element was detected at the interface of bimetal regardless of the thickness of the Cu interlayer. The diffusion behavior of the Cu atom at the interface and the influence of the Cu layer at the atomic scale on diffusion reaction and the Al/Fe interface were further revealed by combining first-principle and molecular dynamics calculations. The simulation results revealed that the Cu layer gradually dissolved into an Al alloy at 750 °C, thereby promoting the diffusion reaction of the Al/Fe interface. Meanwhile, the protective role of the Cu layer against oxidation on the surface of the Fe matrix was confirmed. As a result, the interfacial bonding performance was enhanced when the Cu interlayer was introduced.

Effects of chloride salt erosion and freeze–thaw cycle on interface shear behavior between ordinary concrete and self-compacting concrete

Self-compacting concrete (SCC) has been widely used for concrete jacketing to strengthen RC structures due to its high workability, fluidity, and segregation resistance. In this study, a test was carried out to study the effects of substrate curing including chloride salt erosion and the freeze–thaw cycle on the interface shear strength between ordinary concrete and the SCC. Eighty-four Z-type specimens were designed and tested through direct shear experiments, and the influence of interface treatment (implanting steel bar and cutting groove), concrete type, and substrate curing on the interface shear strength were analyzed. Four calculation models of interface shear strength based on different codes are compared, the applicability of these models is also analyzed. The results show that: For close the substrate concrete and the SCC strength, the effect of chloride salt erosion and freeze–thaw cycle will cause a slight decrease in the interface shear strength compared with the specimen that substrate is not cured, the influence of chloride ion erosion and freeze–thaw cycle on the degeneration of interface shear strength for specimen with implanting steel bar is not more obviously than specimen with cutting groove. Any single code model can not accurately predict the interface shear strength of all specimens with different interface treatments and substrate curing. The fib model can accurately predict interface shear strength of specimens which the average compressive strength of old and new concrete is less than 40 MPa and the substrate is not cured. Whether the substrate is cured or not, EC2 and CSA A23.3–14 models can quite accurately predict the interface shear strength of specimens with an implanting steel bar, but for specimens with cutting groove, the modified AASHTO model can accurately predict the interface shear strength. Except modified AASHTO model, the factor considering the effect of interface treatment should be taken into account when using fib, EC2 and CSA A23.3–14 models to calculate the interface shear strength.