Interfacial Shear Strength Research Articles

On demand thermal surface modification of carbon fiber for improved interfacial shear strength

A thermally triggered, on demand, surface modification method was exploited using carbon fibers (CFs). Bisdiazomethanes undergo thermal activation to generate extremely reactive carbene intermediates, able to react with the CF surface. Herein, the surface modification of continuous CFs is demonstrated by dipping the fibers in a solution of bisdiazomethane at three different concentrations of 1 mmol, 5 mmol, and 10 mmol, followed by air drying and heating at 120 °C. Tensile strength and Young's Modulus values were preserved in the treated fibers, while the interfacial shear strength (IFSS) values showed significant improvement. The highest IFSS improvement was found (189 %) for the fibers dipped in the 5 mmol solution, with significant increases noted for the 1 and 10 mmol modifications, of 54 % and 97 %, respectively. When the thermal modification was repeated with parameters analogous to a sizing application used in CF manufacture (30 s dip, 2-min heating), 74–79 % improvements in IFSS resulted. Hence, this approach can serve as a simple, scalable, and tunable surface modification method for discontinuous CFs that promotes their use in high value applications.

Tensile, flexural and fatigue response of lightweight pumice-reinforced magnesium composite: Experimentation followed by an analytical modelling

Abstract Featherweight material to sustain mountainous loads is an extreme contrast. Still, in reality, the automobile and aerospace industries seek very light materials with high specific strength to survive in global competition. This study offers a timely answer to the problems faced by those sectors. Through the use of a stir-assisted squeeze casting method, the current investigation aims to generate a lightweight magnesium composite that is reinforced with porous low-density pumice particles at weight percentages of 5, 10, and 15 per cent. An examination of the density indicates that there is a downward tendency in conjunction with the growing reinforcement. In comparison to the magnesium alloy in its natural state, the Pumice 15 coupon achieves a tensile strength increment of 47%, flexural strength increment of 35% and a 10-times increment in service cycle at fatigue increase. The micromechanics model is implemented to justify the strengthening process in terms of the adhesion between the filler matrix and the interface shear strength. The property plots that were drafted provide evidence that the suggested material is lightweight while exhibiting a significant amount of strength in tensile, flexural and fatigue. Post-fracture surface morphology analysis exhibits distinct tensile, flexural and fatigue patterns.

Interfacial adhesion enhancement in high‐modulus carbon fiber/poly (ether ether ketone) composites: through the flexible macromolecule‐grafted‐carbon nanotubes sizing treatment

AbstractIn this study, a flexible macromolecule‐grafted‐carbon nanotube (t‐CTN‐SPEEK) is developed and utilized as bridge to enhance the interfacial properties of high‐modulus carbon fiber (HM‐CF) reinforced poly (ether ether ketone) (PEEK) composites. With t‐CTN‐SPEEK sizing, the wettability of HM‐CF is enhanced, thereby promoting better resin wetting. The increased roughness induced by the t‐CTNs‐SPEEK on the surface of the HM‐CF affords improved mechanical interlocking among interface. Additionally, SPEEK enhances the interfacial compatibility of the composites. Thus, after the t‐CTN‐SPEEK sizing treatment, the composite exhibits the best interfacial shear strength (IFSS), as evaluated using the interfacial strength evaluation instrument. This paper also discusses in detail the interfacial strengthening mechanism after sizing and presents a promising approach to enhancing the interfacial properties of HM‐CF composites.

Covalently grafting silane coupling agents onto MXene‐reinforced carbon fibers for epoxy composites with improved mechanical properties

AbstractTwo‐dimensional (2D) MXene (MX) and silane coupling agents are increasingly used to modify carbon materials for the fabrication of composite functional materials, which exhibit enhanced electrical, optical, and mechanical properties due to the synergistic effects of both MX and silane. We demonstrate the modification of carbon fibers (CFs) with MX and three different kinds of silane coupling agents, including 3‐aminopropyltriethoxysilane, 3‐glycidyloxypropyldimethoxymethylsilane, and 3‐mercaptopropyltriethoxysilane, which are named as CF‐MX@N, CF‐MX@O, and CF‐MX@S, respectively, and further prepare the CF‐MX@silane/epoxy (EP) composites. The utilized silane coupling agents serve as bridges between MX and CFs, forming CF‐MX@silane composites. Through comparative analysis, it is found that the CF‐MX@S composites form a strong interface phase through covalent bonds, significantly enhancing the interface compatibility and revealing strong interface adhesion. The interfacial shear strength of the molded CF‐MX@S/EP composites increases to 119.7 MPa, with an 173.9% enhancement comparing to unmodified composites. This work can offer useful guidance and reference for selecting appropriate silane coupling agent to modify CFs with 2D materials to form high‐performance composite materials.Highlights Silane coupling agents are used as bridges to graft MXene‐modified CFs The surface modification of CFs is achieved by a simple one‐step approach Excellent interfacial phase is constructed through forming strong covalent bonds Microstructure and failure interface are responsible to interface strengthen.

Effect of Soil Fines on Geosynthetic Interface Shear Strength

Effect of Soil Fines on Geosynthetic Interface Shear Strength

Microdroplet Pull-out Testing: Significance of Fiber Fracture Results

Fiber reinforced composites are used in structural materials that required light weight and stiffness. The properties of the fibers or matrix are important, but the interfacial properties have a significant impact on the properties of fiber reinforced composite. In this study, the interfacial shear strength (IFSS) was measured using acrylic resin and epoxy resin as base materials. The chemical composition of acrylic and epoxy matrix materials was analyzed to predict the effects on IFSS. Additionally, IFSS was measured through a microdroplet pull-out test. The reliability of the experimental results was enhanced by applying a statistical analysis to IFSS results. In the case of epoxy, GF/epoxy exhibited higher IFSS to twice and half times than CF/epoxy specimens. It means that the surface treatment of the fibers has a significant impact on the interface. In the case of acrylic, IFSS could be measured for GF. But in the case of CF, IFSS was too low to get accurate results of IFSS. Through this research, methods to improve the accuracy of composite interfacial strength measurement experiments were examined, and the study suggested the need for standardized criteria to evaluate composite interfacial adhesion.

Interfacial shear behavior of salt freeze-thaw pre-damaged NC with ECC: Experimental and theoretical investigations

This study aims to clarify the interfacial shear behavior of salt freeze-thaw pre-damaged normal concrete (NC) with engineered cementitious composite (ECC). A comprehensive analysis was conducted to study the effects of the cycle number, interfacial roughness, and ECC curing age on the interfacial shear performance. The results showed that, as the cycle number increased, the interfacial shear strength decreased to varying degrees. The optimal interfacial roughness was 5.5mm, and further increasing roughness would decrease the interfacial shear stiffness. When the ECC curing age was 7 days, it had already reached 85% of the interfacial shear strength of specimens cured for 28 days. Additionally, considering the effects of cycle number and interfacial roughness, an interfacial shear strength calculation model and a shear-slip curve prediction model were established, providing a valuable reference for the engineering application of ECC repair for salt freeze-thaw damaged NC.

Deep learning assisted prediction on main factors influencing shear strength of sintered nano Ag-Al joints under high temperature aging

Bonding strength of sintered nano silver (Ag) joints has been an important index for evaluating the reliability of power module packages, which has been reported to be influenced by many factors. However, it is hard to evaluate and predict those factors affecting bonding strength. With the help of artificial intelligence (AI), the utilization of AI tools to assist in finding science solutions has become a mainstream consensus. In this paper, we will show how to evaluate and predict those sintered nano Ag-Al bonded joints bonding strength with deep learning (DL) methods. Firstly, a reliable extended dataset was obtained using the conditional formal condition table generation Induction Network (CTGAN) based on the die shear test dataset of sintered Ag-Al interface shear strength with four different metallization layers under different high-temperature aging time. Subsequently, four DL models were adopted to predict the shear strength of Ag-Al interface under different metallization layers to evaluate the interface bonding strength, all with high level of determination coefficient (R2, above 0.99) and classification accuracy (above 85%). Last but not least, factors influencing the shear strength of Ag-Al interface were analyzed and ranked by weight analysis and SHapley Additive exPlanations (SHAP) method. This research could provide a novel perspective on understanding those factors affecting the shear strength of sintered nano Ag interconnect layer in power devices.

Experimental investigation on the temperature-dependent shear strength of frozen coarse-grained soil-rock interfaces by considering three-dimensional roughness

Climate warming has led to landslides, especially the slopes containing soil-rock interfaces. A series of shear tests were conducted on the coarse-grained soil (CGS) rock interface at low temperatures. The interface shear strength comprises the pre-peak bonding strength produced by ice and post-peak residual strength created by friction between the CGS and rock surface. As the temperature rose from −15 to −1 °C, the bonded ice strength at different rough interfaces rapidly decreased by a maximum of 82.99 %, because more than 21.29 % of the pore ice had thawed within the CGS. However, the average interface residual strength had decreased by only 18.56 %, which is consistent with the variation of the internal friction angle of the frozen CGS. The interfacial shear strength was much lower than the shear strength of the frozen CGS below −1 °C and that the shear slide typically occurred at the interface. In addition, as the freezing temperature increased, the impact of the three-dimensional roughness to the interfacial shear strength decreased, because the warm frozen CGS could easily shear rupture and adhere to the interface, reducing the influence of the roughness. Finally, it was demonstrated that the Mohr-Coulomb failure criterion could be employed to predict the interface peak shear strength for different normal stresses. This study aims to determine the mechanism responsible for shear strength reduction at a frozen CGS-rock interface during warming and to provide some references for preventing landslides caused by rising temperatures.

Controllably constructing organic-inorganic multilevel network structures by regulating the ratio of APES/OCNTs on the basalt fiber surface to enhance the interfacial properties of fiber/polyethersulfone composites

Basalt fiber-reinforced polyethersulfone (BF/PES) composites exhibit high strength, heat resistance, chemical resistance, excellent mechanical properties, and environmental sustainability. However, the smooth and chemically inert surface of BF results in weak interfacial bonding with PES, limiting its broader applications. In this study, an organic-inorganic multilevel network structure was constructed on the fiber surface by optimizing the ratio of APES and OCNTs, significantly improving the interfacial properties of BF/PES composites and enhancing their overall performance. After treatment with APES2/OCNTs3, the interlaminar shear strength (ILSS), flexural strength, flexural modulus, and interfacial shear strength (IFSS) reached 71.9 MPa, 379.1 MPa, 12.8 GPa, and 55.1 MPa, representing increases of 94.8 %, 64.1 %, 140.5 %, and 161.1 %, respectively. Furthermore, the enhancement mechanism and influence pattern of the APES/OCNTs hybrid sizing agent on the composite interface were thoroughly investigated. This simple, effective, and controllable method offers considerable potential for improving the interfacial bonding of BF/PES composites.

Enhancing Shear Strength in Hybrid Metal-Composite Single-Lap Joints Using Z-pins Fabricated via Fused Filament Fabrication

This paper investigates the interfacial shear strength of hybrid metal-composite single-lap joints (SLJs) reinforced with stainless steel Z-pins fabricated by fused filament fabrication (FFF). The joints were created by 3D printing an orthogonal array of 2 mm diameter steel Z-pins onto a steel substrate using FFF. The Z-pins were then embedded into a basalt fibre (BF)-fabric/epoxy resin composite using the Ultrasonically Assisted Z-FibreTM (UAZ) method to form a high-strength and tough interface. The results demonstrate that steel Z-pins produced via FFF effectively enhance the shear strength of the hybrid metal-composite SLJs, significantly improving joint performance. The study also explores the influence of Z-pin volume fraction and embedding height on SLJ shear strength. It was found that higher volume fractions and greater embedding heights of the Z-pins contribute to the increased shear strength. Compared to unreinforced joints, the maximum shear strength of the steel Z-pin reinforced joints increased by 120.1%. This enhancement is attributed to the effective energy absorption mechanisms, primarily facilitated by the frictional pull-out, plastic deformation and shear fracture of Z-pins accompanied by the formation of ductile dimples. These mechanisms suppress crack propagation and improve joint integrity. This study presents an innovative approach for fabricating hybrid metal-composite joints with enhanced toughness and strength.

Environmental Effects on the Interface Shear Strength of Geomembrane made from Rubber Compound Sheet

Environmental Effects on the Interface Shear Strength of Geomembrane made from Rubber Compound Sheet

Effect of high quality hybrid coatings and coating condition on the properties of continuous glass fiber reinforced polypropylene prepreg composites

AbstractDue to the difficulty in infusing resin into interiors of fiber bundles by prevalent pre‐impregnation methods like melt impregnation and the substantial polarity difference between glass fibers (GF) and polypropylene (PP), the application of continuous glass fiber reinforced polypropylene (CGF/PP) composites has been restricted. In this study, a hybrid emulsion is prepared to address the polarity difference through coating process. And further by optimizing coating process parameters, composites glass fibers with excellent performance can be obtained. The study demonstrates that the composite glass fiber with coating amount of 15.34% exhibits good bunching and flexibility. The monofilament tensile strength and interfacial shear strength (IFSS) are increased by 2.53% and 109.74%, respectively compared to the desized glass fiber (GF0). Furthermore, after the hot‐pressing process, the composites glass fiber bundles show fully filled gaps and a completely wrapped surface. This study lays the foundation for producing CGF/PP prepreg composites conveniently, efficiently, and commercially.

Study on the Interface Reinforcement Effect of Bamboo Grid in Filled Loess Embankment in a High and Steep Gully

A bamboo grid is a new type of reinforcement material, which can replace traditional geogrids in the reinforcement of embankments. In this study, the reinforcement effect of the bamboo grid that is only set at the interface between the filled and undisturbed soils of the filled loess embankment in a high and steep gully was investigated. The influence of reinforcement position and grid spacing on the reinforcement effect was studied by carrying out a large-scale direct shear test, numerical simulation, and field measurement. The results indicated that the bamboo grid could enhance the shear strength of the reinforcement interface. The interface shear strength first improved and then decreased with the decrease in grid spacing. The differential settlement was significantly reduced after the reinforcement of the bamboo grid at the interface. Compared with other reinforcement positions, setting the bamboo grid in the upper part of the embankment was the most efficient and economical. When the grid spacing became dense, the reinforcement effect was improved as the differential settlement decreased. However, the improvement in the reinforcement effect by decreasing the grid spacing was limited, which meant there was an optimal grid spacing.

Effects of oxidation‐induced aggregation structure transformation of aramid fiber on interfacial adhesion of epoxy resin

AbstractThe large‐scale pretreatment and efficient surface activation of aramid fibers (AFs) before composite fabrication remains a major challenge. In this study, we developed a heat treatment–induced surface modification method to change the reactive groups on AFs. Results indicated that the O/C ratio and the number of ester groups on the AFs as well as the surface morphology of the AFs could be flexibly controlled using the heat treatment–induced surface modification method. Furthermore, the surface oxidation mechanism of the AFs changed from point oxidation to surface oxidation during heat treatment. As the heat‐treatment time increased, the crystallinity and tensile strength of the AF monofilament considerably increased. An optimal heat‐treatment time of 30 min was provided considering that long‐time heating (>30 min) would destroy the surface molecular chains. Under this optimal heat‐treatment time, the number of ester groups reached the maximum, which enhanced the reactivity of the AFs in the epoxy resin matrix. The interfacial shear strength between the AFs treated for 30 min and epoxy resin microdroplet increased by 12.64%, reaching as high as 18.17 MPa. Moreover, the contact angle between the AF monofilament and epoxy resin droplet reached a minimum value of 54.7°. Furthermore, the thickness of the interfacial bond layer between the AFs and epoxy resin reached 50–60 nm. These results provide effective theoretical guidance for the large‐scale application of AFs in composite materials.

Layer-by-layer assembling boron nitride/polyethyleneimine/MXene hierarchical sandwich structure onto basalt fibers for high-performance epoxy composites

Interfacial adhesion directly affects the mechanical properties of basalt fiber (BF)-reinforced polymer composites. To construct a more superior interphase between BFs and epoxy resin (EP) than a weak interphase of the unmodified BF/EP, we propose a hierarchical sandwich structure consisting of sodium hydroxide–activated boron nitride (BNOH), polyethyleneimine (PEI), and MXene (MX, Ti3C2Tx) through facile layer-by-layer self-assembly. The fabricated BNOH/P/MX sandwich structure (P denoting “PEI”) can synergistically improve the interface adhesion by enhancing the mechanical interlocking and chemical bonding of the composites. When the composites reinforced by BF–BNOH/P/MX subject to the external loading, flexible PEI molecules allow two-dimensional (2D) rigid BNOH and MX nanosheets to slip at the interface by uncurling the molecular chains, dissipating a great amount of energy during the fracture progress. Meanwhile, the hierarchical BNOH/P/MX sandwich structure acts as an excellent interface and possesses multistage gradient modulus and wider thickness, uniformly and efficiently transferring the stress from the EP matrix to BFs. The interfacial shear strength, impact strength, and fracture toughness of BF–BNOH/P/MX-reinforced EP composite are substantially improved by 45.9 %, 60.6 %, and 148.9 %, respectively, compared with bare BF–based composites. This study can provide valuable references and inspirations for designing and constructing high-quality interfaces for high-strength and high-toughness BF structural materials, taking advantage of 2D materials.

Effect of Water Content and Degree of Compaction of Clay Subgrade Soil on the Interface Shear Strength Using Geogrid

Pavement performance in clay soil roads can be enhanced with the help of the geogrid concept by increasing lateral confinement, bearing capacity, and overall rigidity of the pavement. Also, geogrid is useful in minimizing vertical and lateral pavement deformations. In this study, 65 tests are performed without and with two types of geogrid, and the aim behind it is to investigate the effect of the moisture content and degree of compaction of clay soil on the interface shear strength. The number of materials used to conduct this study, included subbase granular (type B), clay subgrade soil, the Biaxial and SS2 geogrid which is used as a reinforcing material. Testing the direct shear is conducted by a large-scale direct shear manufactured device contains an upper box with side lengths of (20×20×10) cm, and a lower box with side lengths of (20×25×10) cm. Results show that for all tests the normal applied stresses are 25, 50, 75 and 100 kPa, the shear stress displacement curves for all cases follow similar trends and they are affected by normal stress, density and water content of subgrade soil and type of geogrid. Also, it is obvious that the shear stress increases by increasing the normal applied stress and degree of compaction of clay subgrade soil reaching its maximum value at 95% degree of compaction while it decreases by increasing the water content of subgrade soil. The maximum value of shear strength is observed when water content is equal to 8% (dry side) and finally, the Biaxial geogrid BX1100 (G1) is more efficient in reinforcing clay-subbase interface as compared with SS2 geogrid (G2).

Study of alkali and acetylation treatments on sisal fibers compatibility with low-amine/epoxy stoichiometric ratio

Sisal fibers are one of the most commercially utilized as reinforcing agents in composite materials. However, sisal fibers are very hydrophilic because they contain many hydroxyl groups, so their interfacial bonding is low when mixed with a non-polar polymer matrix. One method to improve the fiber-matrix interfacial bond is to modify the sisal fiber surface with chemical treatment. This study evaluated the influence of various chemical treatments on the tensile properties and interfacial adhesion of sisal fibers reinforced with low-amine/epoxy stoichiometric ratio resin. The sisal fibers were subjected to a series of treatments, including 2 wt% alkali for 4 h, acetylation for 1 h, and a combined alkali and acetylation treatment. The FT-IR analysis confirmed the success of the acetylation process by the presence of the carbonyl signal (1728 cm−1). The XRD analysis indicated that the crystallinity index of the sisal fiber (65 %) was increased after alkali (75 %) and acetylation (66 %) treatments. The alkali-treated sisal fibers showed the highest tensile strength (728 MPa) but the lowest interfacial shear strength (17.7 MPa). The acetylated-treated sisal fibers exhibited the highest tensile modulus (44.5 GPa) and interfacial shear strength (25 MPa). However, the combination of alkali and acetylation treatments reduced the tensile strength of the fiber from 659 to 619 MPa. The TGA results revealed that the maximum degradation temperature of sisal fibers (344 °C) was increased after alkali (349 °C), acetylation (348 °C), and a combination of alkali and acetylation (350 °C) treatments. The results suggest that acetylation treatment is highly beneficial for advanced composite applications.

Impact sensing, localization and damage assessment in Fiber-Reinforced composites with ZnO Nanowires-Based sensor array

The structural integrity and monitoring of load distributions in composites are critical for safety and economic efficiency but still challenging. Herein, zinc oxide nanowires (ZnO NWs) were embedded into a carbon fiber-reinforced composite serving as mechanical reinforcement and sensing components. The presence of ZnO NWs in the composite material increased the flexural strength, interlaminar, and interfacial shear strength by respectively 4.9 %, 8.8 %, and 19.9 % due to the strong bonding at the fiber/resin interface and the mechanical interlocking effect. Additionally, the piezoelectric nature of ZnO NWs with an asymmetric crystal structure generated piezoelectric charges under stress, thereby enhancing the sensitivity of capacitive monitoring. A self-developed algorithm was then designed to analyze the array capacitance changes collected from the prepared composite laminate to determine the impact load with high precision with an error margin of 3 mm and not exceeding 0.25 MPa. Furthermore, damage was also able to be detected by monitoring capacitance changes. Overall, the proposed high-precision and minimally aggressive approach for load localization and quantification provides a promising direction and strategic pathway for the development of smart self-monitoring composites.

Investigating the interfacial vertical shear behavior of BFPMPC mortar and cement concrete with pothole repair

Magnesium phosphate cement (MPC) has both traditional cement properties and ceramic properties with fast setting and hardening characteristics. To rapidly reopen traffic and extend its service life, MPC has been widely used in the rapid repair of highway and airport cement concrete pavement. This study utilizes basalt fiber-reinforced polymer-modified magnesium phosphate cement (BFPMPC) developed in previous research to rapid repair the typical potholes on cement concrete pavement, aims to reveal the interface properties between BFPMPC mortar and cement concrete and further investigate the underlying mechanisms for such properties. Firstly, the optimal mixture ratio was determined by orthogonal test design. Then, the shear strength of the repair interface was measured by composite BFPMPC mortar and cement concrete specimens. The mechanical characteristics of the repair interface and the microscopic mechanism were characterized by nano-indentation technology and SEM/EDS. Finally, the interface constitutive model was established by DIGIMAT and finite element model was developed to simulate the interface failure. Results showed that the no new hydration products were produced by the addition of polymer in BFPMPC. BFPMPC matrix became denser with the increase of age, resulting in the better bonding between fiber and paste. The interface vertical shear strength at 6 h and 3 d were 3.1 MPa and 3.9 MPa, respectively. SEM/EDS results showed that polymer has a certain self-healing ability to decrease the crack width with increase of curing age, and a variety of inclusions in the repair interface were observed. The elastic modulus of each inclusion phase can be effectively analyzed by nanoindentation. The simulation results showed that the pressure on upper surface of BFPMPC mortar transfers to the bottom through the repair interface. As the tensile stress on the bottom over the maximum interface tensile stress, the cracks were extend from the bottom to upper, then the structure was failed. Interface vertical shear strength of numerical simulation was, respectively, 3.149 MPa and 3.957 MPa. It is close to the plain shear strength experimental value, validating the proposed interface constitutive relationship.