Shear Band Formation Research Articles

Shear band evolution and mechanical behavior of cold-rolled Zr-based amorphous alloy sheets: An in-situ study

Cold rolling process can regulate the microstructure and mechanical properties of amorphous alloys, but it is still a challenging task to reveal their microscopic mechanism. Here, we designed an in-situ SEM observation device for the cold rolling process of amorphous alloy, and visually observed the formation and evolution of shear bands during single-pass and multi-pass rolling process of the Zr55Cu30Al10Ni5 amorphous alloy sheets. It is found that the evolution process of shear bands in the rolling process of amorphous alloy shows heritability, which is mainly reflected in two aspects: one is that the shear band formation pattern in the single-pass rolling process is more inclined to inherit the previous shear band formation pattern; the other is that the shear deformation is more likely to occur in the pre-existing shear bands in the multi-pass rolling process. This rule can be used to guide the controlled generation of shear bands in amorphous alloys. Moreover, we emphasized the importance of pre-existing shear band orientations and systematically investigated the mechanical behavior of the amorphous alloys with pre-existing shear bands by in-situ SEM observation. It is found that the mechanical properties of the as-rolled amorphous alloys are determined by the competition between the work-softening of the pre-existing shear band itself and the work-hardening caused by the blocking effect of the pre-existing shear bands on the shear deformation. Based on this, we enhance the tensile fracture strength and the tensile ductility of the amorphous alloy by adjusting the orientation of the pre-existing shear bands parallel to the tensile stress axis so that the pre-existing shear bands prevent the linear propagation and destruction of the new shear bands.

Capturing the transition from diffuse to localised failure in constitutive modelling of partially saturated soils

Localised failures in the form of shear band induce localised deformation and saturation within partially saturated soils. Inelastic responses mainly take place inside the shear band, while the zone outside it usually undergoes unloading processes with much smaller changes in deformation and saturation, as observed in several triaxial tests. The interaction between responses inside and outside shear bands governs the macro behaviour under effects of the hydromechanical coupling. This mechanism, along with properties of shear band (inclination, thickness) and the specimen size, are usually missing in existing classical models based on homogenous assumption. They are incorporated into our approach to correctly capture the post-localisation behaviour of partially saturated soils. In our proposed approach, enrichment terms for kinematics are used in the thermodynamics-based formulation to account for strong variations of hydromechanical responses (stress-strain, suction-saturation) outside and inside the shear band. The proposed formulation results in a size-dependent constitutive structure capable of describing the transition of behaviour from homogeneous to localised stages. The promising features of the proposed formulation are illustrated using data from drained triaxial tests.

Investigations on shear band formation in metallic nanolayered composites

While metallic nanolayered composites exhibit ultrahigh strength, they can fail due to shear bands propagation. Shear bands are affected by many factors, such as layer thickness and stacking fault energy. There is a growing demand to simultaneously prevent shear bands while harnessing the high strength potential derived from the dense interface nanostructures. The mechanisms of shear band formation vary among different nanolayered composites, and some of these mechanisms are investigated. The importance of utilizing advanced computational tools to understand shear band formation is highlighted. This review comprehensively addresses the influencing factors of shear band formation, strategies for shear band suppression, and the underlying mechanisms of shear band formation within metallic nanolayered composites.

Texture evolution and hardening behavior of Al/IF composite produced through severe plastic deformation

In this research, the microstructure, texture, and work hardening behavior of the Al/IF composite were investigated. The composites were produced through up to 7 cycles of accumulative roll bonding (ARB). The microstructure evolution revealed that the IF layer fractured during the process and distributed within the Al matrix due to its higher hardness and higher work hardening rate, as well as formation of shear bands. The main deformation textures formed in the Al layer were the {001} <110>, {4,4,11} <11,11,8>, and {111} <112> components. In the IF layer, preferred orientations of {001} <110>, {110} <112>, and {111} <110> were observed. The produced composite exhibited typical tensile behavior, with strength increasing and elongation decreasing during the process due to an increment in dislocation density and hardening. Additionally, the results revealed that the hardening capacity of the composite decreased during the process; however, the strain hardening rate increased. A noticeable increase in dislocation density and a decrease in crystallite size were found to be the main governing parameters of these variations. Moreover, the fracture mode of the composite changed from ductile fracture to a more brittle mode as a result of hardening.

Machinability Features of Ti-6Al-4V Alloy with Ultrafine-Grained Structure

Titanium alloys are widely used in various industries. The most common and well-known titanium alloy is titanium alloy with aluminum and vanadium (Ti-6Al-4V). This alloy is used, for example, in the manufacture of aircraft engines. As part of the development of technologies and the emergence of the evolving requirements for materials, Ti-6Al-4V alloys with ultrafine grains less than 1 μm may become promising. This modification of the alloy has excellent strength characteristics, such as increased fatigue resistance. However, manufacturers are aware of the machinability problem of titanium alloys. To date, a sufficiently high level of understanding of this problem has already been achieved. But, there is practically no information about the machinability of ultrafine-grained alloys and their comparison, in this regard, with the usual coarse-grained version. This study presents the results of experimental studies on the influence of cutting parameters (cutting speed, V, m/min; feed rate, Fz, mm/rev) on the roughness and microstructure of the surface of Ti-6Al-4V samples with coarse-grained and ultrafine-grained structures produced via equal-channel angular pressing. It is shown that turning at a low cutting speed (V = 48 m/min) results in a better surface roughness, Ra, for the coarse-grained sample compared to its ultrafine-grained alloy counterpart. When the cutting speed is increased by 1.5 times (up to V = 72 m/min), on the contrary, the ultrafine-grained sample has a lower surface roughness, Ra, compared to the coarse-grained sample. The differences in the morphology and microstructure of the chips, depending on the microstructure type of the processed alloy, are discussed: the presence of plastic flow lines in the chip microstructure of the turned ultrafine-grained sample and the formation of shear bands, cleavages, and microcracks in the chips of the turned coarse-grained alloy.

Effect of geometry of crystalline dendrite on the uniaxial tension behavior of metallic glass matrix composites based on molecular dynamics simulations

Introducing crystalline dendrites can effectively enhance the plasticity of metallic glass matrix composites. The geometry (e.g., shape and orientation) of the crystalline dendrites can significantly influence the mechanical properties of the material. In this study, we create numerical Cu-Zr glassy samples containing crystalline dendrites of realistic geometries and study their mechanical behaviors under uniaxial tension loading through large-scale molecular dynamics simulations. The results indicate that shear band formation is sensitive to the shape and orientation of the dendrites. The geometry of the dendrites significantly affects the behavior of shear bands in the materials and ultimately leads to different tensile plasticity. This work is aimed at providing guidelines for the design of metallic glass matrix composites with complex second phase dendritic structures.

A comparative study on dynamic deformation and ballistic impact response of Ti–4Al–2.5V–1.5Fe–0.25O and Ti–6Al–4V alloys

Titanium alloys are most suitable for lightweight armour applications due to their superior strength to weight ratio, and α+β Ti alloy Ti–6Al–4V is widely used in armour applications. One of the critical factors limiting the widespread use of Ti alloys in armour application is their high cost. Recently, Allegheny Technologies Incorporated introduced ATI-425® Ti alloy with the chemical composition of Ti–4Al-2.5V-1.5Fe-0.25O as a low-cost alternative to Ti–6Al–4V. Though ATI-425 Ti alloy is primarily intended for armour applications, only limited ballistic results are available in the open literature. In the present work, we compare the quasi-static, dynamic deformation, ballistic impact response and post-deformation microstructure of a low-cost α+β Ti alloy ATI-425 with that of Ti–6Al–4V alloy. Analysis of the results showed that both alloys showed similar yield strength values during quasi-static tension and compression tests, while ATI-425 Ti alloy showed higher tensile ductility, Charpy-V notch impact energy and dynamic flow stress than Ti-6Al-4V. The ATI-425 Ti alloy also exhibited slightly better ballistic performance measured in terms of V50 ballistic limit velocity. Detailed microstructural analysis on quasi-static and dynamic compression-tested samples showed mainly {101–2} tensile twins, whereas {101–2} and {112–1} tensile twins are observed in ballistic-tested samples of both the alloys. Activation of deformation twinning in ATI-425 Ti alloy with higher oxygen is attributed to lower Al content which enhances the twinning activity. Adiabatic shear band (ASB)-induced plugging mechanism is ascertained as the perforation mode in both alloys during the ballistic impact. Analysis of propensity to ASB formation indicated that Ti-6Al-4V has a slightly better resistance to ASB formation than ATI-425 Ti alloy. The improved ballistic performance of ATI-425 Ti alloy in comparison to Ti-6Al-4V is attributed to the higher dynamic flow stress, Charpy-V notch impact energy absorption, and moderate resistance to adiabatic shear band formation.

Investigation of the ductile deformation potential of microscale epoxy materials

In fiber reinforced polymers (FRP), the matrix, e.g. an epoxy system, usually has a microscopic size and therefore may have other properties than the standard bulk samples. It is known that a size effect exists, for epoxy also in terms of ductility or plasticity. However, to date, there is no physical, mechanochemical or molecular explanation for the correlation of plasticity and gauge volume, especially for an archetypical brittle standard epoxy matrix. The specific limits of the gauge volume for these ductile effects are unknown as well. Therefore, a new manufacturing method to produce thin epoxy films with thicknesses between 15 and 100μm is developed. These films are investigated by differential scanning calorimetry (DSC) with regard to the degree of cross-linking. The mechanical properties are determined by tensile and creep test, also at different temperatures. In the next step, a suitable analysis method for the correlation of molecular structure and mechanical deformation behavior is developed. Manufactured films are investigated by ex situ and in situ infrared spectroscopy (IR) to analyze the molecular mechanisms caused by load introduction. Various pre-processing and interpretation methods for the determination of spectral changes, such as peak shifts, are used to figure out the specific molecular changes related to the mechanical stress from the raw spectral data. It was possible to detect molecular changes of the highly cross-linked macromolecules as a result of plastic deformation caused by tensile load. Shear bands and necking are visualized by photoelastic analysis and a better understanding of the brittle material’s ability to form shear bands is achieved.

Effect of precipitate shape and distribution on mechanical behavior of shape memory metallic glass composites by molecular dynamics method

The deformation behaviors of metallic glass composites enhanced with brick and cylindrical shape B2-CuZr precipitates were investigated by molecular dynamics method. Both specimens experience a two-stage phase transformation and triple-yielding phenomenon. The brick-shaped precipitate enhanced bulk metallic glass composite (BMGC) exhibits significantly improved strength and mildly enhanced plasticity compared to cylindrical shape inclusion reinforced BMGC. The larger aspect ratio of brick-shaped precipitate enhanced BMGC strengthens the composite by improving elastic lattice deformation along loading direction, while the enhanced plasticity is ascribed to smaller free path for mature shear bands formation. The deformation mechanism for brick-shaped BMGCs is shear band cutting through precipitates, while that for cylindrical shape precipitate reinforced BMGCs is shear band wrapping around crystalline particles. Both specimens display high strain at crystalline/amorphous interface (CAI) region and might experience interfacial stability issue.

Dislocation behavior and strengthening mechanisms of Cu–Te alloy drawn at room and cryogenic temperatures

In the work, the cryogenic and room temperature drawing behaviors of Cu–Te alloy with a wide range of accumulative drawing true strain up to 1.1 are systematically investigated. For the first time, the storage of geometrically necessary dislocations (GND) and statically stored dislocations (SSD), occurrence of deformation twinning, as well as their respective roles in strain hardening in the drawn Cu–Te alloy at cryogenic and room temperature have been studied. The results show that the liquid nitrogen temperature drawn (LNT-D) Cu–Te alloy presents higher yield strength (YS), ultimate tensile strength than the room temperature drawn (RT-D) Cu–Te alloy. Microstructural investigation reveals that cryogenic wire drawing of Cu–Te alloy promotes the formation of simultaneous twinning and shear bands, accompanied by the fragmentation of Cu2Te phase. The LNT-D Cu–Te alloy exhibits planar slip characteristics, while RT-D Cu–Te alloy presents wave slip characteristics. Compared with RT-D Cu–Te alloy, the higher YS of LNT-D Cu–Te alloy can be mainly attributed to dislocation strengthening and twinning strengthening, which account for 76.25–80.45% and 4.79–4.91% of the total YS respectively. During room temperature drawing, both GND and SSD play an important role in the hardening of Cu–Te alloy. During cryogenic temperature drawing, work hardening is predominantly through rapid multiplication of SSDs.

Meter-scale MICP improvement of medium graded very gravelly sands: Lab measurement, transport modelling, mechanical and microstructural analysis

Microbially induced carbonate precipitation (MICP) is a promising biogrouting method for ground improvement. Most studies to date have focused on MICP treatment of uniform clean sands, with few studies having been conducted at large-scale on well-graded soils more representative of in situ deposits. This study presents a laboratory meter-scale MICP test on medium-graded very gravelly sands. The MICP treatment was conducted in a radial flow cell (diameter: ∼1 m; thickness: ∼0.15 m) with an injection well located at the centre and a constant hydraulic head at the outer boundary to replicate field conditions. Aqueous chemistry of the effluent samples inside the flow cell was continuously monitored. Transport modelling and effluent sampling monitoring of the electrical conductivity and pH show that, in general, there was good delivery and reaction of the bacteria and chemicals in the radial flow cell, with some preferential flow paths being present. The MICP-treated soil was subjected to a series of hydraulic and mechanical tests and microstructural analysis. Interestingly, the biocemented medium-graded very gravelly sands had higher strengths (UCS values of 2.6–7.4 MPa) for a given calcite content (9.2–15.1%) than those in comparable studies where uniform soils have been treated. This can be attributed to the higher initial density of grain-to-grain contact points in the medium-graded soil, and a high grain angularity which resulted in particle interlocking and longer grain-to-grain contact surfaces, as can be seen from Scanning Electron Microscopy images. Consolidated-drained triaxial tests on two cores showed peak deviatoric strengths of 5.9 MPa and 3.7 MPa under an effective confining stress of 100 kPa, with the clear formation of shear bands during shearing, compared to a peak deviatoric strength of 0.5 MPa determined for the untreated soil. MICP treatment clearly enhanced the shear strength and stiffness of the material. The study shows that formation of preferential flow paths may be a challenge for producing uniform biocementation in field applications of MICP. We propose that successful MICP treatment in heterogeneous soils will require a well-designed and well-executed site investigation programme that can identify, a priori, the geometry of any significant high or low permeability features within the soil body to inform the final MICP treatment strategy.

In situ damage characterization of CFRP under compression using high-speed optical, infrared and synchrotron X-ray phase-contrast imaging

The strain rate dependency and failure modes of carbon fiber reinforced plastic (CFRP) laminate were investigated under out-of-plane compressive loading. Simultaneous high-speed optical and infrared imaging were used to measure full-field deformation and temperature in the dynamically loaded specimens. The damage initiation and propagation inside the CFRP laminates at high strain rates were characterized using in-situ ultra-fast synchrotron X-ray phase contrast imaging (XPCI). The visually observed damage onset occurs at the strain value of 4.2 ± 0.6% as a transverse shear fracture at the free edge of specimens. The local temperature increases significantly to 185 °C due to damage initiation at high strain rates, while at low strain rates the temperature rise occurs after the final shear band forms. The XPCI and post-failure analysis provide an integrated perspective on the formation of a diagonal shear crack and disintegration of the specimen into two pieces with the fracture of plies in the in-plane transverse direction. Scanning electron microscopic (SEM) study was integrated with XPCI results to append the time scale for the post-mortem failure pattern as well as the length scale for microcracks and filament-level failure.

Nanostructured Ti-13Nb-13Zr alloy for implant application-material scientific, technological, and biological aspects.

In dentistry, the most commonly used implant materials are CP-Titanium Grade 4 and Ti-6Al-4V ELI, possessing comparably high Young's modulus (>100GPa). In the present study, the second-generation titanium alloy Ti-13Nb-13Zr is investigated with respect to the production of advanced dental implant systems. This should be achieved by the fabrication of long semi-finished bars with high strength and sufficient ductility to allow the automated production of small implants at low Young's modulus (<80GPa) to minimize stress shielding, bone resorption, and gap formation between the bone and implant. In addition, bacterial colonization is to be reduced, and bone adhesion is to be enhanced by adjusting the microstructure. To do so, a dedicated thermo-mechanical treatment for Ti-13Nb-13Zr has been developed. This includes the adaption of equal channel angular swaging, a modern process of severe plastic deformation to continuously manufacture nanostructured materials, to Ti-13Nb-13Zr and short-time recrystallization and ageing treatments. In particular, two-pass equal channel angular swaging at a deformation temperature of 150°C and a counterpressure of 8MPa has successfully been used to avoid shear band formation during deformation and to produce long Ti-13Nb-13Zr bars of 8mm diameter. During recrystallization treatment at 700°C for 10min followed by water quenching, a sub-micron-size primary α-phase in a matrix of α″-phase was developed. Subsequent ageing at 500°C for 1h leads to martensite decomposition and, thus, to a homogeneously nanostructured microstructure of α- and β-phase with substructures smaller than 200nm. The resulting mechanical properties, especially the ultimate tensile strength of more than 990MPa, fulfill the requirements of ASTM F1713 at Young's modulus of 73GPa. Biological investigations show promising results in reducing bacterial biofilm formation and increased cell proliferation of osteoblasts compared to CP-Titanium Grade 4 and Ti-6Al-4V ELI, especially, if etched surfaces are applied.

Excellent impact resistance of multilayer metallic glass films subjected to micro-ballistic impact by overcoming dynamic size effects

Size effects are key issues that hinder the enhancement of impact resistance of films with increasing thickness. In this paper, we consider Ni2Ta amorphous metallic alloy as a prototype thin film and demonstrate that the impact resistance of metallic glass (MG) nanofilms with surface oxidation subjected to micro-ballistic impact can be increased significantly by lamination of thin monolayers, overcoming significantly the size effects in the impact resistance of MG nanofilms. Shear band formation and delamination are the dominant energy dissipation mechanisms for multilayered films under impact. Our molecular dynamics (MD) simulations confirmed that the interfaces between thin layers as modified by surface oxidation play an important role in the impact resistance of the multilayered films. Surface oxidation of multilayered films increases significantly the impact resistance due to oxidation-induced curly structure and the increase of the interfacial strength, which contributes greatly to the energy dissipation during impact. However, excessive oxidation initiates defects near the surfaces of the monolayers to therefore reduce greatly impact resistance of the multilayered films. Our work suggests an effective pathway for fabricating high-performance multilayered MG films with extraordinary impact resistance by overcoming the size effects through the lamination of monolayers.

Relationship between structural heterogeneity and serrated flow in nanoscale phase separated Zr-Cu-Fe-Al bulk metallic glasses

In this work, the relationship between structural heterogeneity and serrated flow in nanoscale phase separated Zr-Cu-Fe-Al bulk metallic glasses with different plasticity was investigated. The results showed that liquid-liquid phase separation would occur during rapid cooling of Zr59(Cu1-xFex)33Al8 (x = 0.4 and 0.5) alloys, resulting in the microstructure formation of amorphous FeZr-rich nanoparticles embedded in the amorphous CuZr-rich matrix. The compression test and statistical analysis indicated that serration dynamics transforms from a chaotic state with a characteristic length scale of stress drop to a self-organized critical (SOC) state with the increase of the atomic ratio of Cu to Fe. This transformation is ascribed to the increase of the number of nucleation sites for shear transformation zones with the increase of structural heterogeneity, which is conducive to the formation of multiple shear bands. This work will be helpful to understand the relationship between the microstructure and deformation behavior.

Rheological properties of Mg2SiO4 glass: A molecular dynamics study

We report an initial investigation of the rheology of Mg2SiO4 glass through classical molecular dynamics simulations. We performed simple shear tests at different temperatures (1–300 K), shear rates (108–1010 s–1) and pressures (0–10 GPa), from which we investigate the atomic rearrangements induced by loading. At low strain, atomic rearrangements, as detected by a non-affine displacement criteria, nucleate randomly in the glass. They then give rise to the formation of shear bands once the steady state of plastic flow is reached. We show that the flow stress follows a Herschel-Buckley law modified to account for the thermal activation of plastic events.

Tonian Continental Arc Magmatism of the Porongos Complex, Dom Feliciano Belt, Southern Brazil

This study provides new information on the deformation, metamorphism, and tectonic setting of the metavolcanic rocks of the southern portion of the Porongos Complex, southern Brazil. The structural analysis enabled the identification of three deformational phases, formed under ductile to semi-ductile conditions. D1 progressed through deformation partitioning, comprising closed to isoclinal folds and an axial plane foliation. Then, simple shear prevailed, resulting in isoclinal folds, sigma-type porphyroclasts, foliation transposition, and mylonitic rocks. D2 comprises open to gentle folds and an axial plane cleavage. The formation of shear bands is ascribed to the semi-ductile D3. The mineral assemblage represented by phengite + chlorite + clinozoisite-epidote + actinolite + albite + quartz associated with the temperatures obtained through the chlorite geothermometer (316°C) indicates greenschist facies conditions. The protoliths of these metavolcanic rocks are geochemically discriminated as calc-alkaline, dacite-to-rhyodacite, with peraluminous compositions. The bulk trace element compositions show enrichment in large-ion lithophile elements and light rare-earth elements and depletion in heavy rare-earth elements. Also, negative Nb, P, Ti, and Ta anomalies are observed in the multielement diagram. All these geochemical features are typical of rocks formed in continental magmatic arcs. Geochemical comparison with other pre-collisional Tonian orthometamorphic rocks from the Dom Feliciano Belt demonstrates strong similarities, which corroborates the prior interpretation of a continental arc setting for the origin of these Tonian rocks.

A Cavity-Based Micromechanical Model for the Shear-Band Failure in Metallic Glasses Under Arbitrary Stress States

Abstract Deformation and fracture of metallic glasses are often modeled by stress-based criteria which often incorporate some sorts of pressure dependence. However, detailed mechanisms that are responsible for the shear-band formation and the entire damage initiation and evolution process are complex and the origin of such a pressure dependence is obscure. Here, we argue that the shear-band formation results from the constitutive instability, so that the shear-band angle and arrangements can be easily related to the macroscopic constitutive parameters such as internal friction and dilatancy factor. This is one reason for the observed tension-compression asymmetry in metallic glasses. The free volume coalescence leads to precipitous formation of voids or cavities inside the shear bands, and the intrinsic “ductility” is therefore governed by the growth of these cavities. Based on a generalized Stokes–Hookean analogy, we can derive the critical shear-band failure strain with respect to the applied stress triaxiality, in which the cavity evolution scenarios are sharply different between tension-controlled and shear/compression-dominated conditions. This is another possible reason for the tension-compression asymmetry. It is noted that diffusive-controlled cavity growth could also be the rate-determining process, as suggested by the recent measurements of shear-band diffusivity and viscosity that turn out to satisfy the Stokes–Einstein relationship. This constitutes the third possible reason for the tension-compression asymmetry.

Effect of fines loss on the microstructure and shear behaviors of gap-graded soils: A multiscale perspective

Natural sand is typically composed of both coarse and fine particles and are susceptible to suffusion erosion under seepage effect. Fines loss caused by suffusion is a critical factor affecting the mechanical and hydraulic properties of soils. This paper investigates the effect of fines loss on the microstructure and shear behaviors of gap-graded soils using a three-dimensional finite element and discrete element coupling method. A modified particle removal scheme based on the internal moment tensor is first presented, which is utilized to generate several specimens with varying degrees of fines loss. The macroscopic shear responses of both eroded and non-eroded specimens are benchmarked using the responses of representative volume elements (RVEs) in pure discrete element method (DEM). The results reveal that the eroded specimen exhibits a reduced peak stress ratio yet almost unchanged critical state values compared to the non-eroded specimen. Fines loss restrains the formation of shear band and results in more uniform stress and strain distribution inside the specimens. In addition, fine particles in gap-graded soils only sustain a small proportion of external loads, particularly for the specimens with more fines loss. The RVEs at different locations of the specimens are found to exhibit distinct packing assemblies and force networks at the end of shearing.

Introducing a new approach for designing advanced epoxy film adhesives with high mechanical, adhesion, and thermal properties by adding hybrid additives for structural bonding

BackgroundEpoxy-based adhesives are widely used in different industries in various forms. Among them, epoxy film adhesives are particularly applicable in constructing honeycomb structures in aerospace systems. However, these adhesives suffer from brittleness, low flexibility, and thermal stability. In the current paper, the effect of pure and functionalized SiO2 and ZrO2 nanoparticles (NPs), the addition of a block copolymer (butyl acrylate-block-styrene), and Novolac resin on the mechanical, thermal, and adhesive properties of the epoxy film adhesive were thoroughly studied. MethodsThe mechanical properties, thermal stability, and surface morphology of the epoxy adhesive samples were evaluated using tensile, thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FE-SEM) images, respectively. More importantly, the Lap shear and Peel tests were utilized to investigate the adhesive properties. Significant findingsPure and functionalized NPs were added to the prepared epoxy adhesive samples. Intriguingly, compared to the non-functionalized NPs, by only adding 1 phr of each functionalized NPs to the formulation, the tensile modulus, tensile strength, and toughness increased to 66 %, 197 %, and 553 %, respectively. More importantly, the single lab shear and T-peel strength were increased as high as 121 % and 101 %, respectively, indicating a synergistic effect. After optimizing the parameters effective on the properties, FE-SEM images of the fractured surface of optimized samples were used to study the possible fracture mechanisms, including crack deflection, crack pinning, nanoparticle debonding, and shear band formation. Also, this synergistic effect was observed in the thermal stability where the only addition of 1 phr of functionalized NPs increased the decomposition onset temperature up to 40 ℃ higher than the neat one. This simple and applicable method can pave the way for using functionalized NPs in modifying epoxy adhesives.