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Experimental studies of the shock wave properties of two epoxy resins with the same composition but different curing temperatures (160 and 200 °C) at up to 330 GPa pressure have been carried out. Laser interferometry was used to record particle velocity profiles at up to 73 GPa pressure while measuring the shock wave velocity. The release sound velocity was experimentally determined in the 3–73 GPa pressure range. Cumulative explosive shock wave generators were used to study the shock Hugoniot of epoxy resins at pressures above 100 GPa. It was shown that the shock compressibility data of both samples are approximated by a single shock Hugoniot within the experimental error. A kink on Hugoniot recorded close to 25 GPa pressure indicates a chemical decomposition in epoxy resin. Above this kink, a change in the shock wave front structure was recorded. Hugoniots of epoxy resin and unidirectional carbon/epoxy composite were compared at up to 370 GPa pressure. [ABSTRACT FROM AUTHOR]

Surface flashover that occurs on the surface of epoxy resin (EP) is one of the main causes of insulation failure in the power system. The newly emerging polar groups on the surface are highly desirable for enhancing the surface flashover performance of EP. Here, we present a facile ultraviolet (UV) irradiation method to enable the controlled introduction of C–OH and C = O groups on the EP surface. The resultant UV-irradiated EPs (UV-EPs) are highly uniform with little variation in surface roughness while exhibiting tunable polar content with the irradiation time. We also present the first systematic investigation into the effect of UV irradiation time on the surface flashover voltage of UV-EPs, with a maximum increase of 23.07% compared to the pristine EP. Mechanistic studies suggest that the enhancement of the surface flashover voltage is mainly dominated by the density of the deep trap, which is strongly dependent on the UV-induced C–OH and C = O groups on the surface. Besides that, the UV-EPs also display long-term stability due to the stable presence of polar groups, which further demonstrates the feasibility of this method for the development of EP with excellent properties. [ABSTRACT FROM AUTHOR]

Alternating current (AC) loss measurement is crucial for the theoretical evaluation and optimization in the fabrication of superconducting AC devices. Lock-in amplifier based on the lock-in phase is commonly adopted and inevitably involves with phase error. In this work, a novel approach for measuring transport AC loss by determining the minimum compensated voltage (MCV) was developed, in which the lock-in amplifier was removed. Since it just uses the voltage signal from an AC voltmeter, it is phase-error immune. Experimental results demonstrated that when using the lock-in amplifier, there existed a system error as the initial phase difference between the sampled (reference) and real current phases, which required careful compensation. In contrast, the phase error no longer needed to be considered by the MCV method, and the AC loss results were obtained much more conveniently with the relative error between the theoretical and the experimental of less than 5%. Finally, the AC loss of a coated conductor spiral wound on an epoxy bar was obtained using the presented approach, demonstrating its low cost, ease of operation, and high accuracy. [ABSTRACT FROM AUTHOR]

Packaging insulation materials with high thermal conductivity and excellent dielectric properties are favorable to meet the high demand and rapid development of third generation power semiconductors. In this study, we propose to improve the thermal conductivity of epoxy resin (EP) by incorporating a three-dimensional boron nitride thermally conductive network. Detailedly, polyurethane foam (PU) was used as a supporter, and boron nitride nanosheets (BNNSs) were loaded onto the PU supporter through chemical bonding (BNNS@PU). After immersing BNNS@PU into the EP resin, EP-based thermally conductive composites were prepared by vacuum-assisted impregnation. Fourier transform infrared spectrometer and scanning electron microscope were used to characterize the chemical bonding and morphological structure of BNNS@PU, respectively. The content of BNNS in BNNS@PU/EP composites was quantitatively analyzed by TGA. The results show that the thermal conductivity of the BNNS@PU/EP composites reaches 0.521 W/m K with an enhancement rate η of 30.89 at an ultra-low BNNS filler content (5.93 wt. %). Additionally, the BNNS@PU/EP composites have excellent dielectric properties with the frequency range from 101 to 106 Hz. This paper provides an interesting idea for developing high thermal conductivity insulating materials used for power semiconductor packaging. [ABSTRACT FROM AUTHOR]

Frontal polymerization has great potential in complementing additive manufacturing processes such as direct ink writing as a continuous cure synchronized to the printing speed can overcome issues such as sagging. To study the incorporation of frontal polymerization into a potential printing process, a frontally polymerizable DGEBA epoxy resin has been developed for both UV and thermal initiation. Through frontal polymerization alone, full conversion is observed with a starting glass transition of 150[degrees]C for both initiation methods. Resulting thermal behavior is shown to have little dependence on either initiation irradiance or temperature utilized and much greater dependence on initiator concentration in the resin. Mechanical behavior is maximized by varying initiator concentration and cure conditions achieving tensile stress of 75 MPa and [K.sub.1C] of 1.2 MPa-[m.sup.1/2]. Shelf stability of the resin proves promising with no viscosity change after 12 weeks of room temperature storage. Future studies will concern adapting the resin for both direct ink writing and continuous fiber additive manufacturing applications. Highlights * Frontal polymerization of EPON 826 using RICFP * Utilized a tetrakis borate containing diaryliodonium cationic initiator * Stable and polymerizable after 12 weeks * Resin printed and frontally cured using UV initiation KEYWORDS direct ink writing, epoxy, frontal polymerization, 1 | INTRODUCTION Frontal polymerization has continued to be a promising rapid manufacturing solution in which polymerization propagates in a localized reaction zone. (1) More specifically, a single stimulus initiation [...]

In order to prepare highly heat-resistant packaging insulation materials, in this paper, bismaleimide/epoxy resin (BMI/EP55) composites with different contents of BMI were prepared by melt blending BMI into amino tetrafunctional and phenolic epoxy resin (at a ratio of 5:5). The microstructures and thermal and electrical properties of the composites were tested. The electrostatic potential distribution, energy level distribution, and molecular orbitals of BMI were calculated using Gaussian. The results showed that the carbonyl group in BMI is highly electronegative, implying that the carbonyl group has a strong electron trapping ability. The thermal decomposition temperature of the composites gradually increased with the increase of BMI content, and the 20% BMI/EP55 composites had the highest heat-resistance index, along with a glass transition temperature (Tg) of >250 °C. At different test temperatures, with increase in the BMI content, the conductivity of epoxy resin composites showed a tendency to first decrease and then increase, the breakdown field strength showed a tendency to first increase and then decrease, and the dielectric constant was gradually decreased. Two trap centers were present simultaneously in the composites, where the shallow trap energy level is the deepest in 20% BMI/EP composites and the deep trap energy level is the deepest in 10% BMI/EP55 composites. Correspondingly, the 10% BMI/EP55 composite had a slower charge decay rate, while the 20% BMI/EP55 had a faster charge decay rate. In summary, the BMI/EP55 composites with high heat resistance and insulating properties were prepared in this study, which provided ideas for preparing high-temperature packaging insulating materials. [ABSTRACT FROM AUTHOR]

We outline a coarse-grained model of epoxy resins (bisphenol-F-diglycidyl-ether/3,5-diethyltoluene-2,4-diamine) to describe elastic and plastic deformation, cavitation, and fracture at the μm scale. For this, molecular scale simulation data collected from quantum and molecular mechanics studies are coarsened into an effective interaction potential featuring a single type of beads that mimic 100 nm scale building blocks of the material. Our model allows bridging the time–length scale problem toward experimental tensile testing, thus effectively reproducing the deformation and fracture characteristics observed for strain rates of 10−1 to 10−5 s−1. This paves the way to analyzing viscoelastic deformation, plastic behavior, and yielding characteristics by means of "post-atomistic" simulation models that retain the molecular mechanics of the underlying epoxy resin at length scales of 0.1–10 µm. [ABSTRACT FROM AUTHOR]

Purpose: This study investigated and compared the bond strengths, microleakage, microgaps, and marginal adaptation of self-adhesive resin composites (SAC) to dentin with or without universal adhesives. Materials and Methods: Dentin surfaces of 75 molars were prepared for shear and microtensile bond strength testing (SBS and μTBS). Silicon molds were used to build up direct restorations using the following materials to form 5 groups: 1. Surefil One; 2. Prime&Bond active Universal Adhesive + Surefil One; 3. Vertise Flow; 4. OptiBond Universal + Vertise Flow; 5. Scotchbond Universal + Filtek Z500 (control group). Bonded specimens were thermocycled 10,000x before being tested either for SBS or μTBS using a universal testing machine at a crosshead speed of 0.5mm/min. Direct mesial and distal class-II cavities were created on 100 sound premolars, with the gingival margin of distal cavities placed below CEJ and restored according to the five groups. After thermocycling, microleakage scores were assessed following immersion of restored premolars in 2% methylene blue dye for 24h, while marginal gaps and adaptation percentages were investigated on epoxy resin replicas under SEM at magnifications of 2000X and 200X, respectively. Results were statistically analyzed with parametric and non-parametric tests as applicable, with a level of significance set at a = 0.05. Results: Bond strengths, microleakage scores, microgaps, and percent marginal adaptation of Surefil One and Vertise Flow were significantly (p<0.001) inferior to the control group. Dentin preconditioning with universal adhesives significantly increased the study parameter outcomes of Surefil One and Vertise Flow, yet they were still significantly below the performance of the control group. Conclusion: Conventional resin composite outperformed the SAC whether applied solely or in conjunction with their corresponding universal adhesives. [ABSTRACT FROM AUTHOR]

The damage mechanism and exposure tolerance of epoxy resins to fast electrons remain unclear. We quantitatively investigated the effects of electron irradiation on a common epoxy resin by dose-dependent electron energy loss spectroscopy. The results show that sp3 states of nitrogen, oxygen, and their adjacent carbon atoms were converted to sp2 states, forming imine (C=N) and carbonyl (C=O) as the total electron dose increased. The sp3 to sp2 conversion mechanism was proposed. The epoxy resin was very sensitive to fast electrons and the original electronic states were maintained up to a total dose of ∼103e− nm−2 at a low temperature of 103 K. Dose-dependent electron diffraction revealed that the intra- and intermolecular geometries changed below and around the total dose of ∼103e− nm−2. [ABSTRACT FROM AUTHOR]

The editor's choice for November 2024 in SPE's Polymer Engineering & Science journal is Anatoly E. Chalykh's article, 'Supramolecular Structure of Epoxy Oligomers.' Recent research by Anatoly E. Chalykh reveals [...]

With the rapid progress of the advanced electronic device industry, precision electronic instruments are gradually developing towards miniaturization. In this case, epoxy resin gradually attracts people's attention, but its intrinsic thermal conductivity is not high, and the resulting heat dissipation problem limits the further application of epoxy resin in the field of electronic packaging. Therefore, how to enhance the thermal conductivity of epoxy resins has become an urgent problem in the field of electronic packaging. In this work, BNNS was successfully prepared by stripping h‐BN into a flaky two‐dimensional material, which was added to the epoxy resin as a filler to make the composite material. And on the basis of the above, two‐dimensional micron silver flakes (AgMS) with different mass fractions were added to the composites, and the AgMS/BNNS/EP composites were successfully prepared. When BNNS was 25 wt% and AgMS was 1 wt%, its out‐of‐plane thermal conductivity was enhanced from 0.17 W m−1 K−1 of pure epoxy resin to 0.43 W m−1 K−1. When BNNS was 20 wt% and AgMS was 1 wt%, the breakdown strength was enhanced from 105 kV/mm for pure epoxy to 130 kV/mm. This work provides a new strategy for synthesizing high‐thermal‐conductivity epoxy matrix composites. [ABSTRACT FROM AUTHOR]

The difficult recycling and degradation in cured epoxy resins can be solved by introducing dynamic covalent bonds. However, the introduction of dynamic bonds degrades the properties of epoxy resins. In this paper, the dual‐cured epoxy resin with high mechanical properties and high healing efficiency were obtained by constructing interpenetrating networks (IPNs). The effect of IPNs on the recyclability of epoxy resins was investigated. The performance is as follows, the flexural and tensile strengths is 89 and 54.2 MPa, respectively, and the breakdown strength is 32.5 kV/mm. In addition, the recyclability and high healing efficiency of the dual‐cured epoxy resin were verified, and the effect of the hot‐pressing temperature and time on the properties of the recycled samples were investigated. Under certain hot‐pressing conditions, the flexural and tensile strengths of the recycled samples were recovered to 95.06% and 85.28%, respectively, and the breakdown strength was recovered to 83.6%. [ABSTRACT FROM AUTHOR]

One‐pot epoxy formulations, containing uncured resin, curing agent, and promoter, require the promoter to be insoluble in the resin at room temperature to prevent premature polymerization. Here, we introduce three novel reaction promoters synthesized by reacting amino propyl imidazole (API) and various diisocyanates such as HMDI, IPDI, or MDI. We evaluate the impact of these promoters on the physical properties, storage stability, and curing kinetics of the resulting epoxy formulations. The results of the kinetic study showed that the compositions containing each synthesized promoter acted as reaction promoters, as evidenced by the lower activation energy in the differential scanning calorimetry (DSC) experiment. The results of the mechanical properties showed that HMDI‐API promoter improved both tensile and flexural strength, while exhibiting high storage stability. The findings provide valuable insights for selecting suitable promoters for specific applications in one‐pot epoxy systems. [ABSTRACT FROM AUTHOR]

The cooling time in injection molding is defined as the period during which the molten plastic in the mold solidifies and cools to a temperature suitable for safe ejection without deformities. Efficient cooling is crucial for large-volume production in the plastic injection molding industry. This study investigates the cooling performance of rapid tooling made from aluminum-filled epoxy resin with varying inner cooling channel surface roughness. This study includes creating a microstructure on the cooling channel surface to assess its impact on cooling efficiency. The study produces rapid tooling with both parallel and series cooling channels. The average cooling time for molded wax patterns is lower with parallel cooling channels than serial cooling channels. Nanobubble coolant shortens the cooling time of molded wax patterns based on experiments of low-pressure wax injection molding. The average cooling time-saving ratio is about 15.4% from five low-pressure injection moldings using nanobubble coolant. [ABSTRACT FROM AUTHOR]

In this work, 1–3 connectivity barium zirconate titanate ceramic cement-based composites were fabricated using Portland cement and epoxy resin as the matrix. Barium zirconate titanate (BZT) of 40–60 % by volume was used while epoxy was used with cement at 0–7% by volume. Dielectric and piezoelectric properties, and other properties such as acoustic impedance, density and microstructure were investigated. It was found that epoxy resin can be used in combination with BZT to achieve a suitable acoustic impedance value (9–11 × 106 kg/m·s2) matching that of concrete for structural health monitoring application. Thus, when epoxy resin was used at 7 %, BZT volume can be increased to 60 % where the highest d 33 value of 93 pC/N was found and remain within the acoustic matching range. In addition, when epoxy resin was increased, both piezoelectric charge coefficient (d 33) and piezoelectric voltage coefficient (g 33) were also found to increase. This is likely due to the lower porosity thus denser matrix when epoxy resin was used in addition to cement. [ABSTRACT FROM AUTHOR]

The bonding performance and formation of the interphase region between fiber and matrix have significant effects on the strength and durability of composites. A new approach, involving combined experimental and numerical analyses, has been developed to avoid the shortcomings and scattering associated with local experimental methods. For this purpose, tensile tests are performed on specimens fabricated from a single glass fiber and epoxy resin. The elongations for specified lengths are measured using the digital image correlation (DIC) technic. The size of the fiber diameter and specimen section are also measured from SEM images. The obtained experimental displacements for micro tensile tests are used in an inverse elastic finite element solution to obtain the interphase elastic modulus. It is shown that, considering the interphase thickness of 1.0 μm that is more realistic, the interphase elastic modulus is in the range of 12 ∼ 19 GPa. However, the performed sensitivity analysis shown that considering interphase thickness ranging from zero to 2.0 μm the interphase elastic modulus varies between 9 and 46 GPa. It is shown that the proposed procedure can be used to obtain the overall mechanical properties of the matrix/fiber interphase in long fiber composites. [ABSTRACT FROM AUTHOR]

This research introduces a low‐temperature catalytic‐assisted pyrolysis method for recycling waste thermosetting epoxy resins, transforming them into an efficient fire‐retardant additive for new epoxy resin formulations. In this study, we demonstrate that boric acid (BA) can significantly reduce the temperature required for epoxy resin (EP) pyrolysis, resulting in degradation products containing boron atoms that can act as a fire‐retardant additive. The impact of 5%–20% content of recycled EP (R‐EP) on the curing process, thermal stability, fire retardancy, and mechanical properties of the new EP was comprehensively investigated. The TGA results show that adding BA to epoxy resin at a 1:4 BA:EP ratio significantly reduces pyrolysis temperature. Neat EP degrades in two stages in 341°C and 557°C, while EP with BA degrades in three stages, starting below 120°C and peaking around 142°C. The results demonstrated an outstanding effect of incorporating 20% R‐EP on the char formation and fire retardancy of the new EP, surpassing the performance of 20% triphenyl phosphate (TPP), a commercially available fire retardant. The storage modulus for neat EP is 1510 MPa, increasing to 2280 MPa with EP/R‐EP 20%, indicating enhanced rigidity. Addition of R‐EP raised glass transition temperature (Tg) of the epoxy resin up to 38°C, indicating highly cross‐linked structures compared to TPP‐modified EP, which shows lower Tg values. [ABSTRACT FROM AUTHOR]

By combination of UV curing and frontal polymerization, interpenetrating polymer networks (IPNs) based on diglycidyl ether of bisphenol‐A (DGEBA) epoxy resin and polydicyclopentadiene (PDCPD) were prepared by UV‐induced simultaneously frontal polymerization in this paper. Compared with the net DGEBA cured polymer, the tensile strength, elongation at break and impact strength of the IPNs were simultaneously improved. The maximum tensile strength and elongation at break of the IPNs reached 100 MPa and 4.64%, respectively, and the maximum impact strength reached 7.34KJ/m2 with an improvement of 115.2% over that of the net DGEBA cured polymer. Thermogravimetric analysis (TGA) results revealed that the IPNs could enhance the thermal stability. Data of the differential scanning calorimetry (DSC) and TGA testing shows that the IPN shows a single glass transition temperature (Tg) which is between the Tg of DGEBA and DCPD, indicating homogeneous phase and highly cross‐linked IPN formed. Morphologies and molecular structure of the IPNs polymer were observed by scanning electron microscope (SEM) and characterized by Fourier transform infrared spectroscopy (FTIR), respectively, whose results also proved the formation of ideal IPNs structures. [ABSTRACT FROM AUTHOR]

To reduce the adverse effects of the flammability of epoxy resin (EP), addition of flame-retardants in EP is a common and effective strategy. A 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) derivative, DOPI, has been synthesized by adding the double bond of itaconic acid (ITA) to DOPO, and was utilized for ligand exchange with terephthalic acid in MIL-53(Fe) to obtain the derived material of MIL-53(Fe)-DOPI. A series of blends were prepared by adding different proportions of MIL-53(Fe)-DOPI into EP. The fire resistance and mechanical properties of these blends were assessed. Among them, the 2 wt% MIL-53(Fe)-DOPI/EP blend displays a UL-94 V-1 rating and a limiting oxygen index (LOI) of 30.0% for combustion. The peak smoke production rate (p-SPR), peak CO production rate (p-COP) and peak HRR production rate (p-HRR) for combustion are respectively reduced by 26.56%, 41.2% and 39.9% compared to the same parameters for the combustion of pure EP. Based on the analysis of Py-GCMS, TG-FTIR, Raman and FE-SEM, a flame retardancy process has been proposed. Additionally, the tensile strength, flexural strength, flexural modulus and impact strength of a blend containing 3 wt% MIL-53(Fe)-DOPI in EP are respectively increased by 24.3%, 62.0%, 85.2% and 13.8% relative to those for unmodified EP. Therefore, MIL-53(Fe)-DOPI is an outstanding additive that can effectively reduce the formation of the smoke and toxic gas during combustion, at the same time, improving the mechanical properties of EP. [ABSTRACT FROM AUTHOR]

Numerous efforts focus on renewable epoxy resin development, with lignin emerging as a viable green alternative to fossil‐derived resources. Being Earth's second‐most abundant organic molecule, lignin, rich in phenolic groups, shows promise as a substitute for bisphenol A in diglycidyl ether of bisphenol A (DGEBA) production. This work successfully modifies Kraft lignin (KL) via one‐step epoxidation (KLE) and phenolation prior to epoxidation (KLPE), significantly increasing oxirane ring content. Characterization via FTIR and 1H NMR spectroscopy validates the modifications, yielding epoxy equivalent weights of 862.1 and 214.6 g mol−1 for KLE and KLPE, respectively. Incorporating 20 wt% KLE into adhesive maintains tensile and lap shear strength compared to 100 wt% DGEBA adhesives, with an increase in elastic modulus, indicating its potential as a sustainable resin substitute. However, phenolation prior to epoxidation slightly reduces mechanical properties despite higher oxirane ring concentration. These results shed some light on the impact of both modification protocols on the mechanical properties of epoxy adhesives, supporting the development and properties optimization of sustainable epoxy adhesives. [ABSTRACT FROM AUTHOR]

One of the main issues in epoxy‐based composite manufacturing is the formation of porosity derived from moisture absorption during storage and layup due to the high hydrophilicity of epoxy matrices. During the curing process, the presence of moisture and other volatile compounds can initiate the nucleation and growth of voids. In this study, the effect of both the initial water content absorbed in the uncured resin and the pressure on the porosity development in an epoxy resin was investigated. In particular, Kardos' and Ledru's models, aimed at predicting void formation in polymers, were applied to study the effect of different hydrostatic pressures in an epoxy resin during curing up to the gel point, after conditioning it at two different relative humidity levels, 50% and 95%. Subsequently, the porosity of the cured resin samples was quantified through density measurements. Comparative analysis of the microscopy images of cured samples and the predictions of both models revealed an overestimation of the final void sizes by both models, with the Kardos' model exhibiting a higher deviation. Additionally, a finite element model was employed to investigate the conditions leading to void formation, aiming to understand the factors influencing the porosity development and properly set the process parameters during composite manufacturing. Highlights: Evaluation of the conditions leading to void growth in epoxy resin during curingMoisture sorption in uncured epoxy resinEffect of curing pressure on pore developmentFinite element analysis for void growth during resin curing [ABSTRACT FROM AUTHOR]

Aramid fiber‐reinforced epoxy resin composites (AFRP) are the main components of electrical equipment such as GIS insulated tie rods, but the poor interfacial bonding between aramid fibers (AF) and epoxy resin (EP) results in a degradation of the material's insulating properties. In this paper, iron phthalocyanine (FePc) molecules are introduced on the AF surface, and the π‐π interaction effect between the metal phthalocyanine rings is used as a driving force to guide the spontaneous assembly of FePc into a three‐dimensional microstructure, and the effect of microstructures with different FePc contents on the insulating properties of AFRP interfaces is investigated. Combining a series of test simulation methods such as surface potential attenuation test, electric tree test, interlayer shear test, and molecular dynamics simulation, reveals the enhancement mechanism of the electrical insulation performance of the interface. The results show that FePc at four contents has an enhancement effect on the flashover voltage along the AF and the breakdown voltage at the AFRP interface, with a maximum enhancement of 25.63% for the flashover voltage and 232.23% for the breakdown voltage. Highlights: Self‐assembled three‐dimensional structures on aramid surfaces were constructed via iron phthalocyanine molecules.The effects of self‐assembled structures on physicochemical properties are compared.Modifications substantially increase the breakdown voltage and flashover voltage.The mechanism of microstructure on interface breakdown voltage enhancement is revealed.The overall effect of multiple factors on insulation properties is analyzed. [ABSTRACT FROM AUTHOR]

The homogeneous dispersion of multi‐walled carbon nanotubes (MWCNTs) in a polymer matrix significantly affects the overall properties of composites. In this study, MWCNTs/epoxy (EP) composites were prepared using DeoxyriboNucleic acid (DNA) as a dispersant. The MWCNTs were uniformly dispersed in a phenalkamine curing agent and crosslinked with an epoxy resin matrix. The non‐covalent functionalization of DNA‐dispersed MWCNTs was confirmed by characterizing both the pristine and DNA‐modified MWCNTs. Additionally, the dispersion state and stability of MWCNTs in the curing agent solution were evaluated. Tensile strength and single‐lap‐shear (SLS) were employed to assess the mechanical properties of the composites. The results indicated that the DNA‐dispersed MWCNTs composites exhibited superior strength and toughness, with tensile and shear strengths of 46.81 and 19.64 MPa, respectively, at optimal ratios. These values represent increases of 68.38% and 50.96% compared to pure EP. Dynamic mechanical thermal analysis (DMTA) revealed that the energy storage modulus of DNA‐dispersed MWCNTs/EP composites increased to 2722 MPa, a 24.7% enhancement over pure EP. Furthermore, the thermal properties of the composites were thoroughly investigated. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) showed that the initial decomposition temperature of the DNA‐assisted dispersed composites rose to 330°C. The macromolecular relaxation of the EP materials occurred at higher temperatures, leading to an increased glass transition temperature. Highlights: DNA was used to disperse MWCNTs in phenalkamine curing agent.MWCNTs/EP composites were made by crosslinking DNA‐dispersed MWCNTs with epoxy resin.DNA‐dispersed MWCNTs boosted tensile and lap shear strength.Thermal properties improved due to DNA‐dispersed MWCNTs, and increased the energy storage modulus of the composite. [ABSTRACT FROM AUTHOR]

In this study, interleaving electrospun Nylon 6.6 nanofibers in the laminate was utilized to improve interlaminar properties of glass/epoxy composite during punching and as a solution to this issue. In order to do so, virgin and nano modified samples are produced and punched and the results are compared to determine the effect of nanofibers on the damaged area as well as the three‐point bending residual strength (carried out on both penetration and exit sides) of the punched laminate. Furthermore, punch—die clearance was also varied to investigate the range in which the nano modification improves the outcome of the process on the laminated composite. According to results of this study, using of Nylon 6.6 nanofibers between composite layers causes significant decrease in the damaged area up to 50%. Also, in both virgin and nano modified laminates, increasing the punch—die clearance increases the damaged area up to 50% and reduces the residual strength of the laminates up to 17%. In addition, nano modified laminates, the residual strength increased up to 28% and 22% for three‐point bending tests carried out on both punch penetration‐ and exit‐side samples, respectively. This is due to the fact that the punch exit‐side contains more damage compared to the penetration‐side. Highlights: Toughening glass/epoxy laminates using electrospoon Nylon 6.6 nanofibers.Decreasing the damage area occur in the punching of composite laminates.Decreasing the damage area in punching by decreasing the punch‐die clearance.Increasing the strength of punched laminates by applying nanofibers. [ABSTRACT FROM AUTHOR]

This study presents a comparative analysis of carbon fiber reinforced polymer (CFRP) composites manufactured through vacuum assisted resin infusion (VARI) using a traditional epoxy resin (E), a fully‐recyclable epoxy resin system with (BBR10) and without (BBR) the addition of a reactive diluent (R*Diluent). Various mechanical and thermal tests were conducted to assess their performance. The BBR10 laminate, incorporating 10 wt% R*Diluent, exhibited competitive mechanical performance, comparable to traditional (E) and fully‐recyclable laminates (BBR). Despite a slightly lower ultimate tensile strength (UTS) compared with BBR, BBR10 demonstrated improved flexural strength and modulus. Low‐velocity impact testing confirmed comparable strength between VARI‐produced composites with the recyclable matrix (BBR and BBR10) and the traditional one (E). X‐ray mCT investigations revealed distinct void arrangements in the CFRP laminates. Additionally, a chemical approach was employed for recovering high fractions of fibers from CFRP laminates with a recyclable matrix (BBR and BBR10). Chemical recycling achieved an almost 100% yield for long carbon fibers. Highlights: Comparative analysis of CFRP composites manufactured through VARI.Diluent addition allowed to tailor the recyclable epoxy viscosity.Mechanical characterization of traditional and fully recyclable epoxy resins.Investigation by X‐ray mCT of potential flaws and manufacturing defects.Chemical recycling of CFRP laminates with a recyclable matrix. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study of the fabrication and joining mechanisms of carbon fiber reinforced polymer (CFRP) composites. The CFRP composites were fabricated by hand lay‐up and vacuum bagging methods. In order to improve the efficiency of the CFRP‐CFRP and CFRP‐AL 7075‐T651 joints, laminates with varying overlap lengths of 25 and 60 mm single lap joints were prepared in both multi‐riveted and hybrid bonded/riveted joint configurations. Due to the epoxy compatibility of CFRP‐CFRP joints, riveted/bonded hybrid joints (HJs) showed superior improvements compared to riveted joints for both material combinations at 25 and 60 mm overlap lengths. Non‐epoxy compatible surfaces of CFRP‐AL 7075‐T651 specimens performed similarly to riveted joints in hybrid configurations. The use of epoxy compatible surfaces was found to increase the joint strength in CFRP‐CFRP single lap hybrid joints in proportion to the increase in overlap length. Ansys non‐linear analysis and experimental results were complementary. The new improvements in joint efficiency of CFRP composites create a wide range of structural applications considering the increasing lifetime of the components and joints. Highlights: Riveting of composites have negative impact on joint strentgh.Hybrid joints using a combination of rivets and adhesives can increase the load bearing capacity.Tensile performance strategy of joint in composites can be improved by diversification of joint combinations. [ABSTRACT FROM AUTHOR]

The interface property of carbon fiber/matrix materials is a key factor influencing the service life of composites. In this paper, our group facilely in‐situ grew zeolitic imidazolate framework‐8 (ZIF‐8) onto the carbon fiber (CF) surface by using branched polyethyleneimine (BPEI) as coupling agent to simultaneously enhance the interface and mechanical performances of CF/epoxy composite. The successful growth of ZIF‐8 nanocrystals onto carbon fiber was confirmed by FT‐IR, XPS, TGA, XRD, Raman, and SEM. After growth of ZIF‐8, the surface morphology for CF grafted with ZIF‐8 (CF‐ZIF‐8) was greatly changed and the surface energy for modified carbon fiber increased from 28.7 mN/m for the untreated CF to 55.8 mN/m. As a result, the interfacial shear strength (IFSS) of CF‐ZIF‐8/epoxy composite enhanced by 103.4%, indicating a significant improvement of interface property of composite. Moreover, the interlaminar shear strength (ILSS) and bending strength also have 37.8% and 23.3% improvement because of the synergistic effect of BPEI and ZIF‐8 compared to the untreated CF/epoxy composite. This work furnishes a facile and efficient strategy for developing high‐performing structural composite materials with excellent interface property. Highlights: ZIF‐8 was in‐situ grown on CF to improve the interface property of composite.Significant improvements on IFSS, ILSS, and bending strength.The mechanism for improving the performances of composite was proposed. [ABSTRACT FROM AUTHOR]

This study explores the development of nanocomposites by incorporating multi‐walled carbon nanotubes (MWCNT), titanium nitride (TiN), and cubic boron nitride (c‐BN) nano powders into photo‐polymer epoxy resins for use in Stereolithography (SLA) additive manufacturing. Mechanical and thermal properties were systematically investigated to assess their performance. Initially, MWCNT, TiN, and c‐BN nano powders were homogeneously mixed with the resin to ensure uniformity. The resulting mixtures were then processed using SLA technology to evaluate production quality and material performance. The study revealed significant improvements in mechanical and thermal properties compared to pure resin, aligning with previous research outcomes. Specifically, the incorporation of MWCNT led to a notable enhancement in thermal conductivity, showing an increase of 24.21% as the thermal conductivity coefficient increased from 0.19 to 2.36 W/m·k. On the other hand, c‐BN significantly boosted mechanical strength, resulting in a substantial 20.45% increase as the shore D hardness went from 88.53 to 106.64. These findings highlight the promising potential of nanocomposites across various industries including electronics, aerospace, automotive, construction, medical devices, and manufacturing. Highlights: Developed nanocomposites with MWCNT, TiN, and c‐BN in SLA resin.c‐BN increased hardness by 20.45%, proving its effectiveness in composites.MWCNT enhanced thermal conductivity by 24.21%, boosting material performance.Pioneering use of TiN and c‐BN in SLA, addressing gaps in existing research.Applications span electronics, aerospace, automotive and medical devices. [ABSTRACT FROM AUTHOR]

Supercritical CO2 (sc‐CO2) was widely used in CO2 flooding projects to enhance the recovery efficiency recently owing to its amazing dissolving capability and permeability. Fiber reinforced pipe (FRP) has exceptional properties that may be widely used in the petrochemical sector for transportation of corrosive fluid in CO2 flooding projects. In this research, a system was designed to simulate the transport behavior of fluids containing CO2 which can reaches the supercritical state by the adjustment of pressure and temperature. The fluid penetrates into the resin interior through the pores and gathers in the cavities at 65°C and 8 MPa. When the temperature and pressure are below the critical point, the CO2 volume expands dramatically, causing inter‐layered micro‐crack. When the environmental conditions repeatedly change above and below the critical point, these cracks will continue to propagate along the fiber arrangement direction, resulting in the fracture progressively grow into the delamination. At the same time, the fluid corrodes the resin in some areas of the surface, generating pitting and a 0.66% loss in resin content. The composition of elements and groups altered after corrosion revealed that a chemical interaction occurred between fluid and epoxy resin. Finally, due to physical and chemical processes produced by penetration, expansion, and dissolution, the stiffness of FRP fell by 3.53% during treatment. Highlights: In the present work, a reactor coated with polytetrafluoroethylene (PTFE) was built to model the corrosion of FRP in delivery fluids containing sc‐CO2. The corrosion mechanism was shown as a combination action by chemical react and physical behavior comprising penetration, expansion and dissolution.The physical corrosion mechanism of fluid containing sc‐CO2 was investigated. The fluid containing sc‐CO2 penetrated the FRP via pores and accumulated in cavities. The quick expansion of sc‐CO2 causes delamination while the ambient circumstances remain below the critical threshold. The pitting and resin loss can be linked to the epoxy resin solution in supercritical CO2.The chemical process, known as hydrolysis, took place on the interior surface of epoxy resin and a fluid containing supercritical CO2. This finally resulted in molecular structural modification. [ABSTRACT FROM AUTHOR]

Supercritical CO2 (sc‐CO2) was widely used in CO2 flooding projects to enhance the recovery efficiency recently owing to its amazing dissolving capability and permeability. Fiber reinforced pipe (FRP) has exceptional properties that may be widely used in the petrochemical sector for transportation of corrosive fluid in CO2 flooding projects. In this research, a system was designed to simulate the transport behavior of fluids containing CO2 which can reaches the supercritical state by the adjustment of pressure and temperature. The fluid penetrates into the resin interior through the pores and gathers in the cavities at 65°C and 8 MPa. When the temperature and pressure are below the critical point, the CO2 volume expands dramatically, causing inter‐layered micro‐crack. When the environmental conditions repeatedly change above and below the critical point, these cracks will continue to propagate along the fiber arrangement direction, resulting in the fracture progressively grow into the delamination. At the same time, the fluid corrodes the resin in some areas of the surface, generating pitting and a 0.66% loss in resin content. The composition of elements and groups altered after corrosion revealed that a chemical interaction occurred between fluid and epoxy resin. Finally, due to physical and chemical processes produced by penetration, expansion, and dissolution, the stiffness of FRP fell by 3.53% during treatment. Highlights: In the present work, a reactor coated with polytetrafluoroethylene (PTFE) was built to model the corrosion of FRP in delivery fluids containing sc‐CO2. The corrosion mechanism was shown as a combination action by chemical react and physical behavior comprising penetration, expansion and dissolution.The physical corrosion mechanism of fluid containing sc‐CO2 was investigated. The fluid containing sc‐CO2 penetrated the FRP via pores and accumulated in cavities. The quick expansion of sc‐CO2 causes delamination while the ambient circumstances remain below the critical threshold. The pitting and resin loss can be linked to the epoxy resin solution in supercritical CO2.The chemical process, known as hydrolysis, took place on the interior surface of epoxy resin and a fluid containing supercritical CO2. This finally resulted in molecular structural modification. [ABSTRACT FROM AUTHOR]

Boron nitride, as an excellent thermal conductive filler, has received widespread attention in the field of heat dissipation, and its interface thermal transport with organic matrix is a key issue for improving thermal conductivity. In this study, several typical modifiers are selected to modify boron nitride to improve its interfacial compatibility with epoxy resin. The composition of functional groups, crystal structure and factors affecting thermal conductivity of the modified boron nitride surface are systematically studied. The influence of main factors such as the structural characteristics of grafted molecules and the grafting functional groups on the construction of thermal conductivity channels was analyzed in detail. The results show that shorter chain length and fewer cross-linked branches are more conducive to phonon transport and propagation. The thermal conductivity of BN-KH570/EP composite at 26 wt% load reaches 1.52 W/m·K, which is 7.6 times that of pure epoxy resin. It also maintains good thermal stability at 600 °C, which provides a new idea for improving the interface interaction of boron nitride composites. [ABSTRACT FROM AUTHOR]

The corrosion problem of metals has caused significant economic losses and safety risks in industrial production. Therefore, it is imperative to take measures to against corrosion. This study develops a new type of hyperbranched epoxy resin for anticorrosive coatings that contain catechol groups similar to mussels. The anticorrosive epoxy coating exhibits extremely high hardness and strength, outstanding thermal stability, excellent adhesion, as well as remarkable resistance to water and salt spray. The results of mechanical test showed that the tensile strength of the coatings could achieve as high as 63 MPa and their pencil hardness reached 8 H. After 30 days of immersion in saltwater, the pencil hardness could still keep 6 H, respectively. Furthermore, compared with the HBEP coating, the PCA-modified coating exposed to salt spray environment for 30 days shows less corrosion on both its surface and scratch area. This new type of coating has tremendous potential applications in areas such as marine metal protection. [ABSTRACT FROM AUTHOR]

Epoxy resin is a thermosetting resin with excellent mechanical properties. It has been pointed out that there are problems on its mechanical properties due to poor polymerization of the epoxy ring caused by water and chlorine impurities during resin production. In this study, we focused on the electrochemical behavior during curing reaction of epoxy resin. To investigate the electrochemical reaction, galvanostat meter was used to measure the voltage behavior during chemical reaction. Molecular Orbital (MO) method was used to understand the mechanisms of voltage behavior during curing reaction. Furthermore, the effect of water existence during curing reaction was investigated by experimentally and analytically. As a result of experimental electrochemical reaction, we successfully measured the voltage behavior associated with the curing reaction. In the case of MO analysis, the epoxy and curing agent models were prepared. Before the reaction, each molecule had zero charge, but after the reaction, it was confirmed that the epoxy had a positive charged and the amine had a negative charged. It is thought that the voltage could be observed due to the movement of this charge during curing reaction. It has been also demonstrated through experimentation and analysis that water accelerates the curing reaction. It was observed that the accelerating effect amplifies as the quantity of water increases. Building upon these results, it was confirmed that the factor leading to the increase in voltage is due to the amount of water. To examine the presence of chlorine impurities during the production of epoxy resin, MO analysis was conducted on the production reaction of epoxy prepolymers. The findings indicated that as the water content increases, the reaction that results in the production of by-products is amplified. This outcome suggested that by-products were already incorporated during the formation of the epoxy. In conclusion, this study provides significant insights into the electrochemical behavior during the curing reaction of epoxy resin, the role of water in accelerating the reaction, and the impact of chlorine impurities during resin production. The findings pave the way for further research to optimize the production process and enhance the mechanical properties of epoxy resin. [ABSTRACT FROM AUTHOR]

Optimizing the impact properties of polymer composites is essential in aircraft industries. Hybridization of fibres is one of the efficient methods to enhance the impact properties of polymer composites. Dispersion of nanoparticles into epoxy resin improves the toughness of composites. This study examines the low-velocity impact (LVI) behaviour of hybrid epoxy-based carbon/glass fibre-reinforced laminates. Initially, the epoxy resin was modified with 0, 0.5, 1, 1.5, and 2 wt% of nanoclay and TiO2 nanoparticles using mechanical stirring followed by an ultrasonication method. To investigate the influence of stacking sequences, laminates were fabricated with (90 G/0 G/90 C)S, (90 G/0 C/90 G)S, and (90 C/0 G/90 G)S. The samples used for this study are six-ply symmetric laminates. Laminates were impacted with different impact energies between 30 and 80 J with an impact velocity of 7 m/s to generate damages. The residual strength of damaged specimens is determined using compression after the impact test. The order of stacking, fibre orientation, and the presence of nanoparticles all have a significant impact on the residual strength of laminates. By using C-scan images, layer-wise damage mechanisms were identified. The specimen with (90 C/0 G/90 G)S sequence has very high damage resistance compared to other laminates. [ABSTRACT FROM AUTHOR]

To evaluate the deterioration degree of insulation material by monitoring partial discharges (PDs), it is necessary to fully understand the PD behavior prior to breakdown. We performed measurements of temporal variations in the number and magnitude of PDs in a void of epoxy resin. It was found that the number of PDs with larger magnitude is less before breakdown and that there is a decreased tendency of the number and magnitude of PDs with the elapsed time. The tendency is remarkable as the applied electric field is small. Additionally, the time to breakdown becomes short when the scattering of the number of PDs per unit time decreases. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The thermoplastic high-ortho phenolic resins (HPRs) were synthesized by a one-step synthesis using phenol, formaldehyde, zinc acetate, sulfuric acid, and small amounts of ethanol. It was then blended with epoxy resins, and a small amount of ethylenediamine (EDA) was added as a curing agent for dry spinning to produce the as-spun fibers. Heat curing and microwave curing treatments were performed to obtain phenolic epoxy fibers. Using Fourier transform infrared spectroscopy to study the structural changes during the fiber curing process revealed that the amino groups in EDA opened the epoxy groups to generate the hydroxyl groups. The hydroxyl groups can further react with the epoxy groups, which accelerate the curing reaction. Thermogravimetric analysis (TGA) results showed a higher residual carbon degree in the fibers after curing. Mechanical property testing demonstrated a significant improvement in the mechanical properties of the fibers. By modifying the blending and optimizing the curing process, the heat resistance of the fibers was successfully improved, resolving the issue of poor mechanical properties in the high-ortho phenolic epoxy fibers (HPEFs). [ABSTRACT FROM AUTHOR]

The resin film infusion (RFI) process is a novel composite molding method for high-fiber content, excellent mechanical properties, low porosity, and adjustable thickness. This review examines two common resin materials used in the RFI process: bismaleimide resin (BMI) and epoxy resin. Furthermore, numerical simulation methods for isothermal and non-isothermal processes in the RFI process are described, focusing on the analysis of the mathematical model of resin flow. Finally, it covers the unique properties of RFI composites and showcases the RFI process's cost-effectiveness and functionality in fabricating composite structures for various applications. The limitations and potential future developments of RFI process molding technology are also summarized. [ABSTRACT FROM AUTHOR]

Bisphenol-A resin epoxy resin composites doped with various concentrations of inorganic hybrid nanofillers, TiO2 + ZnO, were thoroughly examined in the research described in this report for their microwave dielectric relaxation spectroscopy. Ultrasonic dispersion techniques were used to disperse the TiO2 + ZnO hybrid nanofiller into the Bisphenol-A resin. X-ray diffraction (XRD) was employed to ascertain the structural characteristics of the TiO2 and ZnO nanoparticles (NPs) and TiO2 + ZnO hybrid NPs doped neat epoxy (epoxy + hardener). A Vector network analyzer was used to measure the dielectric properties of the hybrid NPs doped neat epoxy in the frequency range from 200 MHz to 20 GHz. Our findings offer important new perspectives on the polarization mechanisms and structural properties of these composite materials. The complex relationship between frequency and dielectric characterization led to measurement complexities that often come with extensive time and cost requirements. This paper presents the random forest regression model as an effective method for predicting the frequency-dependent dielectric constants in composite materials. The main objective of this study was to examine the performance metrics, such as the adjusted R-squared score, root mean squared error (RMSE), and mean absolute error (MAE), across various values of the minimum node size parameter (nmin). This study showcases the effectiveness of the RF regression model to accurately and efficiently predict the frequency-dependent dielectric constants in composites. As a result, it eliminates the requirement for laborious and expensive laboratory testing. [ABSTRACT FROM AUTHOR]

This study investigates the impact of zinc oxide nanoparticles on epoxy resin systems and the ultraviolet (UV) aging resistance of modified epoxy resin composites using molecular dynamics (MD) simulations and experimental methods. Initially, various epoxy resin cross‐linking models are established through MD simulations to understand the influence of different nano ZnO contents on resin modification, further validated by experiments. Subsequently, the UV radiation resistance of nano ZnO–epoxy resin composites is assessed by subjecting them to high‐intensity UV radiation equivalent to 3 years of natural environmental conditions, analyzing changes in tensile properties, impact performance, hardness, and glass transition temperature of epoxy resin before and after UV radiation exposure. The findings suggest that the addition of nano zinc oxide reduces the impact of UV radiation on epoxy resin, with optimal UV radiation resistance observed at a nano zinc oxide mass fraction of 0.3 wt%. [ABSTRACT FROM AUTHOR]

Recently, composites have attracted many researchers, which have advanced favored properties compared to metallic materials, such as high strength with lightweight as well as corrosion and erosion resistance and others. However, these resources are exposed to yield during the working life. For these new products and their employing in different applications, and for the mentioned importance, this study has investigated the mechanical characteristics of these structures to avoid potential failure. An investigation of Arcan (shear V -notch test) procedure has been conducted for epoxy resin which is used for reimpregnations with Eglass and compared with lightweight metal of Aluminum as a benchmark to show the shear behavior for the composite one under shear load experimentally and numerically. The butterfly-shaped sample was modeled and tested accordingly with Arcan (shear V -notch test) numerically in order to produce pure shear force by tensile subjection condition using ANSYS software. The test verified that a state of pure shear was present during the testing on each ± 45∘ inclined from the axis of subjection although the changes recorded as G magnitude of shear modulus between Aluminum and the thermoplastic of Epoxy resin is nearby 94%, which may be because of the effect of material nature (i.e. mechanical properties) for the selected materials. The mentioned novel constituent shear behaviors have been investigated and compared expediently. These novel constituents can be adopted in different applications of shear loads. [ABSTRACT FROM AUTHOR]

Polysilazane (PSZ) is a class of novel materials with significant advantages; however, its practical applications are severely limited due to drawbacks such as the need for high-temperature curing and susceptibility to brittleness and cracking. Consequently, we have chosen PSZ and epoxy resin (EP) as the film-forming resins, with silica aerogel (SiO2gel) serving as the inorganic filler, to fabricate a SiO2gel–PSZ/EP composite coating capable of curing at room temperature. The incorporation of EP and SiO2gel has improved the toughness, mechanical stability, and thermal stability of PSZ. After 800 cycles of abrasion wear, the composite coating maintained its surface integrity. The scratch test rated its adhesion at level 1. Additionally, after 14 days of immersion in acidic and alkaline solutions, the coating demonstrated favorable chemical stability. The coating underwent 10 cycles of thermal shock testing, during which no significant cracking or peeling was observed on the surface. Finally, electrochemical impedance spectroscopy testing revealed that, after exposure to 300 °C, the composite coating exhibited a corrosion current density of 1.23 × 10−10 cm2, corresponding to a corrosion protection efficiency of up to 99.99%. In summary, the coating maintains excellent anticorrosion properties even after exposure to high temperatures and demonstrates outstanding stability, significantly enhancing its durability in harsh environments. This enhancement suggests a broad potential for applications in the field of subsea transportation. [ABSTRACT FROM AUTHOR]

The application of fiber-reinforced polymer (FRP) composites as piling materials in harsh environments has gained popularity due to their high corrosion resistance. FRP composites can be fabricated using different types of epoxy resin matrices and fibers. This study aims to investigate the interface behavior between sand and FRP materials with varying levels of hardness, with a particular emphasis on the abrasive surface wear of FRP. Monotonic interface shear tests (under normal stresses of 50, 100, 200, and 400 kPa) and interface shear tests repeated 20 times (under normal stresses of 200 and 400 kPa) are performed. The local surface roughness of the FRP plates is measured for tested samples under both monotonic and repeated loadings using laser scanning to evaluate the accumulated abrasion effect. The results of monotonic tests indicate that under a given shear displacement and normal stress, the samples with softer FRP plates exhibit higher interface friction angles and more pronounced dilative behavior. Following repeated tests, the interface friction angles of softer FRP specimens decrease, while the surface roughness of the FRP plates gradually increases. However, for the softest FRP plate, its surface is severely damaged after repeated tests under high normal stress levels, leading to unstable changes in the test results. [ABSTRACT FROM AUTHOR]

Epoxy insulators in gas-insulated power apparatus are subjected to the combined effects of electrical and mechanical loads. In this work, a simulation model is built based on the energy theory to explore the electrical tree growth of epoxy resin under tensile and compressive stresses. With increasing AC voltage, the electrical tree growth is promoted, exhibiting a morphology with more branches. Tensile stress accelerates the electrical tree growth, while proper compressive stress has the opposite effect. However, when the compressive stress exceeds a certain value, electrical tree growth is promoted again. When the mechanical stress is vertical to the needle electrode, these effects primarily impact the length of the trees. Conversely, in parallel cases, mechanical stress mainly affects the width of the electrical trees. Filler doping play the role of obstacles as well as enhancing the electric field concentration, the electrical tree growth is firstly inhibited and then promoted as the doping content increases. The electrical tree morphologies of simulation and experiment are in good consistency, proving the reasonability of the simulation model. [ABSTRACT FROM AUTHOR]

Aramid fiber (AF)-reinforced epoxy (EP) resin composite materials are widely used in the application of insulation rod-reinforced components, but the adhesion performance between AFs and EP resin is poor, which easily leads to interfacial defects and even gradually develops into breakdown, flashover, and other faults. In this study, a simple, environmentally friendly, diverse, and highly designable layer-by-layer self-assembly modification method was adopted to assemble aramid nanofibers/SiO2 onto the surface of AFs. The modified AFs were then used to produce composite materials with EP resin. By testing the interface breakdown, flashover, and leakage current of the AF/EP resin composite materials, the influence mechanism of AF surface modification on the material interface insulation performance was studied. The results show that the insulation performance of the modified composite material first increases and then decreases with the increase in the number of assembled layers, with the maximum increase in breakdown voltage being 93.56% and the maximum increase in flashover voltage being 30.91%. [ABSTRACT FROM AUTHOR]

Epoxy resins, ubiquitous and indispensable thermosetting material in various industries, suffer from the resistance to crack initiation, poor ductility, and irreparable permanent cross‐linked network, which hinder their utilization in high‐performance applications and are detrimental to the development of a sustainable economy. However, achieving the trade‐off between toughness, robustness, and reprocessability of epoxy resins remains a formidable challenge. Herein, an epoxy resin that combines ultratoughness, robustness, and reprocessability by incorporating a hierarchical crosslink structure embedded in a transesterification network is reported. The construction of hierarchical coordination structures facilitates formation of dense nano‐hard domains, enabling enhancement of both strength and toughness at multilength scales. As a result, the epoxy resin, integrating covalent adaptable networks with sacrificial non‐covalent networks, exhibits exceptional elongation at break (280%), modulus (1.8 GPa), stress at break (56.3 MPa), and tensile toughness (142 MJ m−3), showcasing its excellent endurance and ability to undergo multiple reprocessability. The application of this epoxy resin in carbon fiber‐reinforced polymer composites further underscores its potential as the resulting HCEV‐CFRPs exhibit unprecedented tensile properties and facilitate multiple non‐destructive recycling of high‐value carbon fiber under mild conditions. This research provides novel design principles for recyclable and high‐performance materials that combine strength and toughness. [ABSTRACT FROM AUTHOR]

Highlights Hybrid fiber‐reinforced composites uniquely address the performance limitations of carbon fiber‐reinforced polymers (CFRPs). In this study, continuously wrapping large tow CF (48 K) with low‐cost nylon was proposed to create nylon‐CF core‐spun yarns (NCCYs). Unidirectional nylon‐CF/epoxy composites (NCFECs) were successfully fabricated using NCCYs as hybrid fiber reinforcement. The nylon wrapping on the CF significantly enhanced the energy absorption and dispersion of the CFRPs, thereby improving the impact strength. The measured impact strength of the NCFECs was 108.7 kJ/m2, which was 70.4% greater than that of the corresponding CF/epoxy composite (63.8 kJ/m2) with the same CF content. Additionally, NCCYs exhibited an excellent interfacial shear strength of 35.3 MPa, representing a 73.9% increase compared to that of the large tow CF (20.3 MPa). This study developed NCFECs using a simple and low‐cost process to produce advanced composites, providing an innovative manufacturing strategy for CFRPs with high impact resistance. The NCCYs are prepared by using the wrapping technology. The structure of the wrapped yarns endows the NCCYs with high interfacial shear. The nylon fiber layer gives NCFECs higher impact strength. [ABSTRACT FROM AUTHOR]

Highlights SiO2 and Al2O3 micron particle effects on the mechanical and vibration properties of carbon fiber‐reinforced polymer (CFRP) composites were systematically investigated by incorporating these particles into the epoxy resin. CFRP laminates were prepared by adding various weight fractions (0–10 wt. %) of micron particles to the epoxy resin. The influence of cutout shape and the angle (θcf) between square cutout and fiber orientation on the vibrational performance of CFRP laminates were investigated. As the particle weight fraction (PWF) increased, the tensile, bending, interlaminar shear, and vibration properties of CFRP initially improved and then declined. The flexure strength of samples with 4 wt. % SiO2 and Al2O3 particles increased by 11.70%. The samples with 8 wt. % SiO2 and Al2O3 particles exhibited the highest damping ratio, which was 4.59 times greater than that of the samples without particles. The cutout shape and θcf influence the vibration performance of CFRP laminates. For the rectangular cutout, the sample with θcf = 22.5° exhibits the highest damping ratio, exceeding those at 0° and 45° by 2.28% and 7.10%, respectively. Three‐roll milling can disperse 4 wt.% particles in resin. SiO₂ and Al₂O₃ particles improve mechanical properties of CFRP. SiO2 and Al2O3 particles increased the damping ratio of CFRP by 359.22%. Circular cutout minimally reduces the first‐order natural frequency of CFRP. Angle between rectangular cutout and fiber affects CFRP vibrational properties. [ABSTRACT FROM AUTHOR]

With the development of electronic devices and wireless communication technology, the quality of human life has improved. However, shielding from electromagnetic interference (EMI) is required due to device malfunctions and harmful effects on human health. Polymer‐based shielding materials getting much attention due to their light weight, flexibility, good processability, and other desirable traits. However, achieving consistent dispersion of conductive fillers and optimizing the balance between electrical, mechanical, and thermal properties remain challenges despite the advantages of polymer‐based materials. Especially, epoxy resins are promising polymer materials for EMI shielding applications due to their excellent mechanical strength, chemical resistance, and excellent adhesive properties. Additionally, epoxy resin exhibits remarkable processability allowing for various fabrication techniques such as casting, molding, and three‐dimensional printing. However, one of the significant drawbacks of epoxy resin is the difficulty in achieving uniform dispersion of conductive fillers within the epoxy matrix. In this study, we propose an iron‐nickel alloy (FeNi) embedded in an epoxy matrix (FeNi/Epoxy) for EMI shielding material. It is manufactured by facile fabrication process due to the advantages of epoxy, which has excellent processability. EMI shielding effectiveness at 12 GHz is enhanced from 9.12 to 17.86 dB by the increase of FeNi concentrations. Furthermore, thermal and mechanical properties were improved by the increase of FeNi concentration. Thermal conductivity for efficient heat dissipation is increased from 0.63 to 1.49 Wm−1 K−1. Moreover, polydopamine (PDA) was employed as a surface coating material for FeNi to overcome the non‐uniform dispersion of FeNi particles in the epoxy matrix. Surface coating by PDA significantly enhanced the dispersion uniformity and strengthened the adhesion between the filler and matrix. Elastic modulus is greatly increased from 83.03 MPa to 1.29 GPa by the surface coating. The enhancement of mechanical properties is derived from the chemical bonds between the filler and matrix. [ABSTRACT FROM AUTHOR]