Adhesive Toughness Research Articles

Balancing Interfacial Toughness and Intrinsic Dissipation for High Adhesion and Thermal Conductivity of Polymer-Based Thermal Interface Materials.

In recent years, adhesive thermal interface materials have attracted much attention because of their reliable adhesion properties on most substrates, preventing moisture, vibration impact, or chemical corrosion damage to components and equipment, as well as solving the heat dissipation problem. However, thermal interface materials have a huge contradiction between strong adhesion and high thermal conductivity. Here, we report a polymer-based thermal interface material consisting of polydimethylsiloxane/spherical aluminum fillers, which possesses both adhesion properties (adhesion strength of 3.59 MPa and adhesion toughness of 1673 J m-2 and enhanced thermal conductivity of 3.90 W m-1 K-1). These excellent properties are attributed to the modified chain structure by introducing acrylate accelerators into the polydimethylsiloxane network, thereby striking a balance between interfacial toughness and intrinsic dissipation. The addition of thermally conductive aluminum fillers not only increases the thermal conductivity but also improves the bulk energy dissipation of the thermal interface material. This work provides a novel strategy for designing a novel thermal interface material, leading to new ideas in long-term applications in high-power electronics.

Interfacial fatigue fracture of pressure sensitive adhesives

Pressure sensitive adhesives (PSAs) are viscoelastic polymers that can form fast and robust adhesion with various adherends under fingertip pressure. The rapidly expanding application domain of PSAs, such as healthcare, wearable electronics, and flexible displays, requires PSAs to sustain prolonged loads throughout their lifetime, calling for fundamental studies on their fatigue behaviors. However, fatigue of PSAs has remained poorly investigated. Here we study interfacial fatigue fracture of PSAs, focusing on the cyclic interfacial crack propagation due to the gradual rupture of noncovalent bonds between a PSA and an adherend. We fabricate a model PSA made of a hysteresis-free poly(butyl acrylate) bulk elastomer dip-coated with a viscoelastic poly(butyl acrylate-co-isobornyl acrylate) sticky surface, both crosslinked by poly(ethylene glycol) diacrylate. We adhere the fabricated PSA to a polyester strip to form a bilayer. The bilayer is covered by another polyester film as an inextensible backing layer. Using cyclic and monotonic peeling tests, we characterize the interfacial fatigue and fracture behaviors of the bilayer. From the experimental data, we obtain the interfacial fatigue threshold (4.6J/m2) under cyclic peeling, the slow crack threshold (33.9J/m2) under monotonic peeling, and the adhesion toughness (~ 400J/m2) at a finite peeling speed. We develop a modified Lake-Thomas model to describe the interfacial fatigue threshold due to noncovalent bond breaking. The theoretical prediction (2.6J/m2) agrees well with the experimental measurement (4.6J/m2). Finally, we discuss possible additional dissipation mechanisms involved in the larger slow crack threshold and much larger adhesion toughness. It is hoped that this study will provide new fundamental knowledge for fracture mechanics of PSAs, as well as guidance for future tough and durable PSAs.

Endocytosis-Inspired Zwitterionic Gel Tape for High-Efficient and Sustainable Underoil Adhesion.

Marine oil exploration is important yet greatly increases the risk of oil leakage, which will result in severe environment pollution and economic losses. It is an urgent need to develop effective underoil adhesives. However, realizing underoil adhesion is even harder than those underwater, due to the stubborn attachment of a highly viscous oil layer on target surface. Here, inspired by endocytosis, a tough gel tape composed of zwitterionic polymer network and zwitterionic surfactants is developed. The amphiphilic surfactants can form micelle to capture the oil droplets and transport them from the interface to gel via electrostatic attraction of polymer backbone, mimicking the endocytosis and achieving robust underoil adhesion. Benefiting from the oil-resistance of polymer backbone, the gel further realizes a combination of i) long-term adhesion with high durability, ii) repeated adhesion in oil, and iii) renewable adhesion efficiency after exhausted use. The tape exhibits an ultra-high adhesive toughness of 2446.86 J m-2 to stainless steel in silicone oil after 30 days' oil-exposure; such value of adhesive toughness surpasses many of those achieved in underwater adhesion and is greater than underoil adhesion performance of commercial tape. The strategy illustrated here will motivate the design of sustainable and efficient adhesives for wet environments.

Bioinspired ‘phenol-amine’ cross-linking and mineral reinforcement enable strong, tough, and formaldehyde-free tannic acid-based adhesives

Conventional tannin-based adhesives have limitations such as formaldehyde emission, inadequate strength and toughness, which restrict their practical applications. Herein, motivated by the natural mechanisms of ‘phenol-amine’ cross-linking and biomineralization, a strong, tough and formaldehyde-free tannic acid-based adhesive was prepared by using all-biomass feedstock. The adhesive was prepared by integrating tannic acid-Zn nanoparticles (TA-Zn NPs), hyperbranched polyamide-grafted dialdehyde chitosan (HPCS), and triglycidylamine (TGA), which formed the fundamental cross-linking network of the prepared adhesive through a Schiff base reaction. The dry and wet bonding strength of the adhesive achieved 1.91 MPa and 1.54 MPa, respectively. The presence of sacrificial bonds such as N…Zn complexation and hydrogen bonding in the adhesive significantly enhance its toughness with a debonding work of 0.595 J. Benefiting from the exceptional antimicrobial properties of TA, chitosan, and Zn2+, the prepared adhesive demonstrated excellent mechanical properties even after being stored in a humid environment for 2 days, with wet and dry bond strength of 1.42 MPa and 1.10 MPa, respectively. Moreover, this adhesive exhibited remarkable resistance to mildew for a duration of 30 days and emitted lower volatile organic compounds compared to other synthetic and biomass adhesives. This innovative bionic strategy holds great potential in enhancing the toughness and functionality of adhesives and composites.

Soybean protein “mechanically interlocked” bonding of polysaccharide and MXene to improve the strength and toughness of biomass adhesive

Simultaneously improving the strength and toughness of soybean protein adhesives is a huge challenge. The multi-scale enhancement strategy proposed in this study introduced MXene nanosheets and oxidized sodium alginate (OSA) to improve mechanical properties. The polymer network framework with high crosslink density dissipates energy by restricting the slip of the SPI molecular chains, and MXene act as stress dispersers in the polymer network in order to solve the challenge of the strength-toughness balance. The prepared biomass-based adhesives with high adhesion (dry/wet shear strength 1.93 MPa/1.33 MPa), high toughness (adhesion work 810.9 mJ), high thermal stability, high residual rate (92.53 %), low moisture absorption rate (11.18 %), and long storage time (12 d). Additionally, the application of SOM-5 adhesive reduces the burden of petrochemical resource extraction for adhesive production and contributes to the sustainable development of the wood industry. Most importantly, it presents an adoptable strategy for resolving the tension between strength and toughness of composite materials.

Controllable stress-adsorbed layers in Ti/TiN/TiAlN coatings: Mechanical performance and micropillar compression

Solid particle erosion often compromises the durability of turbine engine blades, particularly those used in offshore and desert environments. Surface protective coatings have emerged as a promising solution to significantly enhance the erosion resistance of compressor blades. In this study, TiAlN multilayer coatings were deposited onto Ti-6Al-4V substrates using a vacuum arc deposition technique. The article explored the strategic incorporation of TiN-Ti-TiN stress-adsorbed layers (SALs) within TiAlN-based coatings. It also investigated the microscale mechanisms leading to coating failure under conditions of micropillar compression. The findings revealed that the presence of metal/ceramic interfaces significantly improved the adhesion strength, crack resistance, erosion resistance and fracture toughness of the coatings. The multilayer deformation behavior of the coatings was primarily determined by the plastic flow of the softer metal layers. The SALs played a crucial role in reducing the elastic strain energy by generating nanotwins, coherent interfaces, and high-density dislocations during deformation, thereby improving the coatings' plastic deformation capability. Moreover, the implementation of dual-cycle SALs successfully reduced radial crack propagation, facilitating a transition from brittle fracture to a combined brittle-ductile fracture mechanism. This study highlights the critical role of metal/ceramic interfaces and SALs in improving the erosion resistance and co-deformability of TiAlN-based hard coatings.

Failure analysis of adhesively bonded joints using a modulatory damage model

This article presents a novel approach to investigating the failure behavior of adhesively bonded joints (ABJs) in two different configurations of the single lap joint (SLJ) and double cantilever beam (DCB). The proposed approach utilizes a numerical-experimental procedure that incorporates a trapezoidal traction-separation cohesive zone model (CZM) with a modulator damage function. This damage function adjusts to account for parameters specific to ABJs. Additionally, the adhesive model includes graphene nanoplatelets, which are added in varying concentrations (ranging from 0 wt% to 0.5 wt%), to account for the mechanical properties of the adhesives in the new damage model. With a dual effect, the results indicate that the addition of graphene nanoplatelets enhances the elastic modulus and adhesive strength while simultaneously reducing the adhesive toughness (GT). Extensive analysis demonstrates that the updated damage model outperforms its predecessor in accurately predicting the behavior of ABJs. Furthermore, by deriving the energy release rate from GT, the presented model eliminates the need for determining the mode I energy release rate (GIC) through DCB tests when simulating ABJ failure.

Study on the preparation of two-component structural acrylate adhesive with high performance and low odor

ABSTRACT This article describes the preparation of structural acrylic adhesives (SAA) with low odor and high strength. Isobornyl methacrylate and methacrylic acid were used as the main monomers. Cumene hydroperoxide was used as a radical polymerization initiator. The effects of tougheners, coupling agents, elastomers, monomers, and peroxide on the performance of acrylic adhesives were studied sequentially. The toughness of acrylic structural adhesives was discovered to be enhanced by the addition of carboxyl-terminated butadiene-acrylonitrile liquid rubber (CTBN) to the acrylic matrix. Coupling agents were added to improve SAA’s ability to adhere to steel. The results demonstrated that the SAA performs best when the methacrylic acid’s content is 7 wt%, cumene hydroperoxide’s content is about 1.5 wt%, CTBN’s content is 3 wt%, and the coupling agent’s content is 1 wt%. Adhesive modified using 2-hydroxyethylmethacrylate phosphate and CTBN as the toughener provided excellent adhesion to the steel substrate. Its lap shear strength was found to be above 24 MPa, its T-peel strength was up to 8.29 N/mm, and its impact strength was up to 12 kJ/m2. The resulting SAA is capable of meeting structural adhesive bonding strength criteria for steel-to-steel joints.

Six-membered ring-reinforced flexible high-elongation block polyamide as strong and multi-reusable hot melt adhesive

This study presented the synthesis and characterization of polyester block polyamide hot melt adhesives (PPHMAs) with high adhesion strength and toughness. The PPHMAs demonstrated an adhesion strength of 11.04 MPa and toughness of 22.54 MJ·m−3, making them suitable for various substrates such as aluminum, copper, and stainless steel. The polyamide segments synthesized from dimer acid and 2-methyl-1,5-diaminopentane exhibited characteristics of softness and high elongation. Using isophorone diamine as a reinforcing agent introduced a stable six-membered ring structure, which enhanced the polymer's rigidity and strength, thus meeting the requirements for polyamide segments to function as the hard segments in block polymers. A trace amount of Tris (2-aminoethyl) amine provided the cross-linking sites which are similar to those in neuronal structures. The polyester segments, which were synthesized from poly (propylene glycol) diglycidyl ether and sebacic acid, served as the soft segments in the block polymer and were connected to the hard segment via amide bonds. The addition of the polyester segments enhanced the non-covalent molecular interactions within PPHMAs, leading to dynamic crosslinking properties. The adhesive maintained stable adhesion even after six cycles, which showcased its durability. Furthermore, the PPHMAs exhibited notable chemical resistance. It retained over 60 % adhesion strength after exposure to some chemical solvents including artificial seawater, 5 % NaOH solution, 5 % HCl solution, and DMSO for 24 h. These findings offered a novel approach to enhancing the adhesion strength and toughness of conventional thermoplastic hot melt adhesives.

Visual Quantitation of Dopamine-Inspired Fluorescent Adhesion with Orthogonal Phenanthrenequinone Photochemistry.

Quantifying adhesion is crucial for understanding adhesion mechanisms and developing advanced dopamine-inspired materials and devices. However, achieving nondestructive and real-time quantitation of adhesion using optical spectra remains challenging. Here, we present a dopamine-inspired orthogonal phenanthrenequinone photochemistry strategy for the one-step adhesion and real-time visual quantitation of fluorescent spectra. This strategy utilizes phenanthrenequinone-mediated photochemistry to facilitate conjoined network formation in the adhesive through simultaneous photoclick cycloaddition and free-radical polymerization. The resulting hydrogel-like adhesive exhibits good mechanical performance, with a Young's modulus of 300 kPa, a toughness of 750 kJ m-3, and a fracture energy of 4500 J m-2. This adhesive, along with polycyclic aromatic phenanthrenequinones, shows strong adhesion (>100 kPa) and interfacial toughness thresholds (250 J m-2) on diverse surfaces─twice to triple as much as typical dopamine-contained adhesives. Importantly, such an adhesive demonstrates excellent fluorescent performance under UV irradiation, closely correlating with its adhesion strengths. Their fluorescence intensities remain constant after continuous stretching/releasing treatment and even in the dried state. Therefore, this dopamine-inspired orthogonal phenanthrenequinone photochemistry is readily available for real-time and nondestructive visual quantitation of adhesion performance under various conditions. Moreover, the adhesive precursor is chemically ultrastable for more than seven months and achieves adhesion on substrates within seconds upon blue light irradiation. As a proof-of-concept, we leverage the rapid and visual quantitation of adhesion and printability to create fluorescent patterns and structures, showcasing applications in information storage, adhesion prediction, and self-reporting properties. This general and straightforward strategy holds promise for rapidly preparing functional adhesive materials and designing high-performance wearable devices.

Micro-structural, electrical, and tribological properties of SiC/DLC composite coating grown by PLD on steel

Protective diamond-like carbon (DLC) composite coating was grown on cylindrical steel surface in a simple inclined pulsed laser deposition (PLD) process. Based on this kind of flexible film-synthesis method, mixed deposition was used to generate the gradient interface that could enhance adhesive strength in Ti/SiC interface, and periodic SiC/DLC layers were grown to reduce residual stress of the pure DLC film. This kind of PLD-grown SiC/DLC composite coating on the curved thin steel that was imitated as piston cylinder showed excellent adhesive property and toughness. Compared with the bare steel, DLC-filmed steel strip had a much lower friction coefficient, higher nano-hardness, and enhanced elastic modulus. Raman spectroscopies showed transform of the micro-structure in DLC layers during friction process, revealing the important reason for reducing friction coefficient. Electrical conductivity test displayed the DLC-filmed steel strip was in high resistance state, although its thickness was only 1.27 μm. Further on, good adhesive strength, excellent toughness and high resistance state of SiC/DLC composite coating could be applied in the MEMS advices.

“Like binding a book”: Interfacial improvement of pre-melted ultrahigh molecular weight polyethylene by pulse vibration molding

Ultrahigh molecular weight polyethylene (UHMWPE) is widely used in industrial, military, and civilian applications owing to its excellent properties. However, the high entanglement degree of UHMWPE melt leads to great difficulties in diffusion and crystallization, which causes poor interfacial strength and mechanical properties of pre-melted UHMWPE, restricting its high-quality processing and high-value recycling. To this end, we propose a rapid interface stitching technology with a pulsed vibration force driving free volume homogenization and chain segment orientation. For the first time, pulse vibration molding (PVM) is applied for the hot-pressing of pre-melted UHMWPE, successfully realizing the interface stitching and product strengthening. Compared with those of the convention molding (CM) samples at 180 °C, the interfacial adhesive fracture toughness of the adhesive samples processed using PVM is increased by 105.9 % and the work of tension of the recycled samples processed using PVM is also increased by 49.09 %, respectively. The fracture strength of the PVM recycled samples at 180 °C reaches 91.77 % of that of the pure samples and the yield strength is also higher, which significantly enhances the recycling of UHMWPE. The characterization results of the interfacial molecular chain entanglement and crystallization show that PVM strengthens the molecular chain diffusion and induces crystallization by promoting the orientation of chain segments, especially at the interface. Consequently, we believe that the proposed technology can play a significant role in the UHMWPE processing methods that involve surface healing.

Constructing reactive “rod-bead” nanohybrid-driven high-efficient crosslinking network for the preparation of strong and tough plant protein adhesive

There still exist challenges to regulate the crosslinking network of soybean flour (SF) precisely with both strong and tough mechanical properties to match adhesion requirements of wood adhesives applications. Herein, a novel nanohybrid crosslinker with dynamic bonding effect was synthesized and then employed to improve SF adhesives. Dimethylglyoxime as chain extender was incorporated into polyurethane cooperating with CuO to form dynamic coordination bonds, after which epoxy and siloxane dual-functionalized polyurethane was co-deposited onto cellulose nanocrystal (CNC) surface to construct reactive “rod-bead” nanohybrid named CuOGU@CNC. It is found that epoxy groups induce CuOGU@CNC to form covalent crosslinking interactions with SF matrix constructing a stable adhesive system. Meanwhile, the dynamic coordination bonds of dimethylglyoxime and CuO serve as sacrificial units to contribute for energy dissipation, during which the unique “rod-bead” structure increases contact efficiency between DMG and CuO to optimize bonding exchange rate to high-effectively redistribute stress during loading. Given on the effect, the adhesives modified by CuOGU@CNC present improved dry and wet adhesion strength, and adhesion toughness compared to pristine SF sample. This work can provide a facile strategy to prepare high-performance wood adhesives aiming to meet higher applicational standard.

Influence of modelling hypotheses on strength assessment of CFRP stepped repairs

Composite stepped repairs can achieve high strength recovery without the addition of bolts or fasteners to the structure. They are therefore a major issue in the field of aerospace composite structure damage repair. However, there is no standardized method to design this type of repairs. Many analytical, semi-analytical and finite element models were proposed throughout the years to predict the strength of stepped repairs, using various hypotheses and simplifications. The aim of this paper is to investigate the influence of modelling hypotheses on stress distribution and strength prediction of composite stepped repairs. Five simplified stepped joint models using macro-element (ME) modelling and finite element method (FE) are compared to a full 3D FE model of a stepped repaired panel. The influence of step length and adhesive fracture toughness was investigated to determine the field of validity of each model. Among FE models, it was shown that modelling the equivalent joint under 2D generalized plain strain gives a very close strength prediction to the 3D stepped repair model while saving computation time. Simplified macro-element models under bar or beam hypotheses are fairly close to the results of FE modelling, but the deviation between those and FE is sensitive to step length and adhesive fracture toughness.

Pre-notch and pre-crack size effects on T-peel fracture behaviors of SAC305 solder joints

T-peel test of ductile adhesive is always an interesting and important topic in peeling mechanics and fracture mechanics. In this paper, the pre-notch and pre-crack effect on the T-peel test with a ductile adhesive layer is studied. Based on the experimental test of SAC 305 adhesive and copper adherent T-peel tests, it is found that the peak loads, fracture toughness, resistance curve, and adhesive toughness are sensitive to pre-crack or pre-notch lengths. Short pre-notch or pre-crack trigger unsteady state debonding frequently, and deep pre-notch or pre-crack conditions achieve steady state debonding more easily. Different data reduction schemes such as simple beam theory (SBT), corrected beam theory (CBT), and compliance-based beam method (CBBM) will lead to variations of fracture toughness extractions for T-peel tests. Trapezoidal shape cohesive zone model (CZM) is found to be easier matching T-peel tests conducted in this paper. However, T-peel samples with shorter pre-notch or pre-crack lengths are hard to simulate with the CZM method due to the unstable crack propagation. The reasons, which may lead to the discrepancy between pre-notch and pre-crack T-peel samples, are also presented and discussed. The selection of different pre-notch or pre-crack lengths is a very important factor that needs to be considered in the T-peel test.

Tuning mechanical properties of TiAlSiN/TiAlN multilayers by interfacial structure

Multilayer structure as an effective way to tailor the structure and performance of hard coatings has attracted wide attentions. Here, we aim to elucidate the change of the interface, mechanical properties and oxidation resistance for TiAlSiN/TiAlN multilayers by varying modulation ratios from ML (tTiAlSiN/tTiAlN = 1:1) to HML (tTiAlSiN/tTiAlN = 1:2). Increasing TiAlN sublayer thickness stabilizes the cubic growth of TiAlSiN layers, where the HML exhibits coherent epitaxial growth in contrast to the cubic-wurtzite mixed structure of ML. This coherent strengthening effect is responsible for the noteworthy enhancement of the hardness values from ∼30.9 GPa of ML to ∼33.2 GPa of HML. Significantly, the presence of a coherent interface effectively withstands external pressure, thereby endowing HML with exceptional adhesive strength and fracture toughness. Nevertheless, the oxidation resistance of the coating is reliant on the chemical composition, with the multilayers displaying lower oxidation resistance compared to the TiAlSiN monolayer.

Biomimicry and topology optimization for adhesive toughness design in bonded heterogeneous films

Heterogeneous films have recently been extensively studied due to their superior material properties compared to homogeneous films. However, studies focusing on the design of heterogeneous films, especially with multi-material phases and structures, have been relatively scarce. This paper presents a bioinspired design methodology aimed at optimizing the mechanical properties of heterogeneous films through the strategic arrangement of stiff and soft material blocks. The heterogeneous film is represented as a composite beam and the interfacial failure process is simulated by a cohesive zone model. Then an optimization algorithm is employed to adjust the distribution of stiff materials within the soft film patch in the heterogeneous film. The results show that a nearly twofold increase in adhesive toughness for the optimized film compared to the original. Further discussions shed light on the energy distribution and variations in the fracture process zone size, providing insights into the observed enhancements. In terms of efficiency, the proposed optimization method distinctly outperforms the greedy method, demonstrating the potential for a more effective and efficient design of heterogeneous films with improved mechanical properties.

Effect of Al content on in-situ formation of Al2O3 protective layer on Ni-Al coatings in high-temperature chloride molten salt

The microstructure, strength, toughness, and resistance to chloride molten salt corrosion of Ni-Al coatings with varying Al content were investigated. Increasing the Al content from 9.9 to 61.1 at.% resulted in a decrease in adhesion strength and toughness, while an increase in corrosion rate. Contrary to previous reports, it is noteworthy that Ni-Al coatings with the lowest Al content exhibited superior resistance corrosion due to the formation of an oxidation layer which effectively blocked corrosion. This protective layer was primarily in-situ formed through the reaction between crystalline water present in the molten salt and an appropriate amount of Al. The balance between Al and O content is precisely regulated, resulting in the in-situ formation of Al2O3 protective.

Bioinspired strategy for the fabrication of fast‐curing, tough, and high‐strength phenolic resins

AbstractPhenolic resins (PRs) find extensive use in adhesives and constructions, but they suffer from low curing rate and high brittleness. Herein, we drew inspiration from the lobster sclerotization process and proposed a simple approach to fabricate PRs by integrating pyrogallol‐functionalized graphene nanoplatelets (PG@GnPs), amine‐terminated hyperbranched phosphonitrilic chloride trimer (HPNC), and phenol formaldehyde (PF) resin. The resulting PRs exhibited significant improvements in comprehensive performance. The onset curing temperature decreased from 115.6 to 101.7°C, while the adhesion work increased by 126.5% and the toughness increased by 494%. Additionally, the wet bonding strength increased by 68.7% and the flexural strength increased by 208%. The accelerated curing rate was attributable to the oxidative crosslinking between catechol moieties in pyrogallol and amino groups in HPNC under alkaline conditions, as well as the high reactivity between pyrogallol or amino groups and PF chains. The outstanding mechanical properties were resulted from the synergistic enhancement effects of PG@GnPs and HPNC, which effectively transferred and absorbed energy upon loading. Overall, this work presented an attractive design strategy for developing high‐performance and multifunctional polymer composites.Highlights A bioinspired strategy was proposed for preparing advanced phenolic resins. PG@GnPs were produced via a green and low‐cost ball milling method. Adhesion work and toughness increased by 126.5% and 494%, respectively. Bonding and flexural strength have improved by 68.7% and 208%, respectively. Significantly accelerated curing rate was achieved.

Thermomechanical behavior of a novel hybrid epoxy/ZnO nanocomposite adhesive in structural bonding: Experimental analysis and ANN modeling

ObjectivesEpoxy adhesives are advanced materials, but suffer from high brittleness and low toughness due to their high crosslinking degree, which limits their service life in structural applications. The lack of appropriate thermal stability at high temperatures is another constraint of epoxy adhesives. The main aim of this research was to increase the thermal stability and toughness of epoxy adhesives using phenolic resin, zinc oxide (ZnO) nanoparticles, and poly (butyl acrylate-block-styrene) copolymer as a toughening agent. Furthermore, the mechanical properties of epoxy adhesives were predicted by designing two feed-forward multilayer perceptron (MLP) networks. MethodsEpoxy adhesives with different contents of phenolic resin (10, 20, and 30 phr), copolymer (1.25, 2.5, and 3.75 phr), and ZnO (0.5, 1, 2, and 5 phr) nanoparticles were synthesized under mechanical mixing by using xylene as solvent. Then, the epoxy adhesive samples for tensile and lap shear tests were cured at room temperature for 7 and 2 days, respectively. The mechanical properties of adhesive samples were measured by tensile and lap shear tests. The thermal stability of the epoxy adhesive samples was investigated by thermogravimetric analysis (TGA). The kinetics of the curing reaction of the optimum epoxy adhesive samples was also studied by differential scanning calorimetry (DSC). ResultsThe toughness of epoxy adhesive containing 10 phr phenolic, 2.5 phr block copolymer, and 2 phr ZnO nanoparticles increased by 20%, and shear strength by 99% compared to pure epoxy adhesive, notifying a significant synergistic effect. The TGA results showed that all three mentioned additives have increased the thermal stability of pure epoxy. The highest thermal stability was observed for epoxy adhesive containing 2.5 phr block copolymer and 2 phr ZnO nanoparticles. In addition, DSC analysis proved the positive effect of ZnO nanoparticles incorporation and block copolymer on the curing kinetics of epoxy adhesive. Moreover, the predicted tensile strength, tensile modulus, toughness, and shear strength of epoxy adhesives by MLP networks showed a very good consistency between the experimental data and the model predictions (e.g., MRE < 1.1 for lap shear). SignificanceIn the current study, the artificial neural networks (ANN) results showed that there was very good consistency between the ANN predictions and the experimental data.