液体端羧基丁腈橡胶改性双马来酰亚胺结构胶粘剂(Ⅱ)DACPE固化BMI体系胶粘剂的改性及形态结构

液体端羧基丁腈橡胶(CTBN)改性双马来酰亚胺树脂（BMI）中，不同共混方式、不同分子量及不同-CN含量的CTBN对DACPE体系双马来酰亚胺胶粘剂力学性能的影响不同，由此选择性能优异的CTBN制备出改性4,4‘-双（对-氨基苯甲酰基）二苯醚（DACPE）固化1^#双马来酰亚胺体系胶粘剂。     

Adhesive repair of bismaleimide/carbon fiber composites with bisphenol E cyanate ester

The adhesive strength and repair efficiency of bisphenol E cyanate ester (BECy) is investigated for the injection repair of high temperature polymer-matrix composites (PMCs) by lap shear (LS), short beam shear bending (SBSB), and double-cantilever beam (DCB) tests. Bismaleimide/carbon fiber (BMI-cf) composites were chosen as a model substrate. The BECy resin showed similar strength at room temperature to a benchmark epoxy adhesive and outperformed the epoxy at high temperature (200 °C) in all mechanical tests performed. The influence of moisture content of the PMC substrate on the adhesive strength of BECy was systematically investigated. Drying of PMC before repair was necessary for excellent repair performance. Both the flexural strength of repaired SBSB specimens and the inter-laminar fracture toughness of repaired DCB specimens were significantly higher than that of the control composites and stable over a broad temperature range.     

The preparation and performance of a novel room-temperature-cured heat-resistant adhesive for ceramic bonding

A novel adhesive for joining ceramic materials was made using silicon-epoxy interpenetrating polymer networks (IPNs) as matrix (based on silicon resin (SR) and diglycidyl ether of bisphenol A (DGEBA) epoxy resin (EP)), γ-glycidoxypropyltrimethoxysilane (γ-GPS) as cross-linking agent, dibutyltin dilaurate (DBTDL) as catalyst, Al, low melting point glass (GP) and B₄C powders as inorganic fillers, low molecular polyamide (LMPA 650) as curing agent. The character and heat-resistance property of the IPNs and adhesive were tested by FT-IR, DSC and TG. The compressive shear strength of ceramic joints was investigated at different temperatures in atmosphere surroundings. The modification mechanism of inorganic fillers was studied using XRD. Results showed that the IPNs were a homogeneous morphology of inter-crosslinked network structure with single T_g. The adhesive could be cured at room temperature with good heat-resistance property due to the chemical bond of epoxy group and Si-O-Si. The optimum compressive shear strength (9.44 MPa at 1000 °C) occurred at SR/EP ratio: 9/1, content of KH560: 2%, Al/GP/B₄C ratio: 3.2/4/3, fillers/IPNs ratio: 6/4. The adhesive had good heat-resistance property with 10% weight loss at 435 °C. Failure mode of joint was mixing failure due to the high chemical bonding force.     

Investigation on the bond strength of Al-1100/St-12 roll bonded sheets,optimization and characterization

Al-1100/St-12 aluminum clad steel sheets were produced using roll bonding process at different reductions in thickness and with various supplemental annealing treatments. Experiments were conducted by applying the Taguchi method to obtain optimum condition for maximizing the joint strength. The joint strengths of the bi-layer sheets were evaluated by peel test. The Al/Fe intermetallic phases at the joint interface and the peeled surfaces were examined using scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) and Vickers microhardness test were performed to characterize the intermetallic compounds. The results indicate that at the optimum condition of 0.50 reduction in thickness, 450 °C annealing temperature and 90 min annealing time, the bond strength reaches to the base aluminum sheet strength. In comparison to the reduction in thickness and annealing time, the annealing temperature has the most influence on the joint strength changes. In general, raising the annealing temperature up to 450 °C, increases the joint strength. However, annealing treatment at 500 °C reduces the strength due to the formation of brittle Al/Fe intermetallic layer at the bond interface. Additionally, increasing the reduction in thickness improves the joint strength.     

Evaluation of interfacial shear strength and residual stress of sol-gel derived fluoridated hydroxyapatite coatings on Ti6Al4V substrates

Interfacial shear strength is one of the critical properties in bioceramic coatings on metal implants because it directly affects the success of implantation and long-term stability. In this study, shear strain lag method was employed to evaluate the interfacial shear strength of sol-gel derived fluoridated hydroxyapatite (FHA) coatings on Ti6Al4V substrates. The residual stresses were measured using the “wafer curvature method”. The resultant interfacial shear strength increased from pure HA’s ∼393-459 MPa as fluorine was increased to 1.96 at% and further increased to ∼572 MPa as fluorine increased to 3.29 at%. The residual stresses in the coating also decreased from pure HA’s ∼273-190 MPa and further to ∼137 MPa as fluorine composition in the coating increased. The reduction in the residual stress mainly comes from the reduction in the difference in coefficient of thermal expansion between the coating and the titanium alloy substrate.     

Optimum thickness of joints made of GFPR pultruded adherends and polyurethane adhesive

This paper presents results of experimental and numerical investigations on double-lap joints composed of pultruded GFRP profiles and polyurethane adhesive subjected to quasi-static axial tensile loading. The objective was to investigate the effect of the joint geometry on the structural response of adhesively-bonded joints and, in particular, to seek for experimental evidence of an optimum adhesive layer thickness. The influence of the adhesive thickness (0.3–10.0 mm) and the overlap length (50–200 mm) on the joint behavior was investigated. It was found that there is an optimum adhesive thickness of approximately 1.0 mm and joint strength consistently increases with the overlap length.     

Mechanical properties of 3D KD-I SiCf/SiC composites with engineered fibre-matrix interfaces

Three-dimensional (3D) silicon carbide (SiC) matrix composites reinforced with KD-I SiC fibres were fabricated by precursor impregnation and pyrolysis (PIP) process. The fibre-matrix interfaces were tailored by pre-coating the as-received KD-I SiC fibres with PyC layers of different thicknesses or a layer of SiC. Interfacial characteristics and their effects on the composite mechanical properties were evaluated. The results indicate that the composite reinforced with as-received fibre possessed an interfacial shear strength of 72.1 MPa while the composite reinforced with SiC layer coated fibres had a much higher interfacial shear strength of 135.2 MPa. However, both composites showed inferior flexural strength and fracture toughness. With optimised PyC coating thickness, the interface coating led to much improved mechanical properties, i.e. a flexural strength of 420.6 MPa was achieved when the interlayer thickness is 0.1 μm, and a fracture toughness of 23.1 MPa m^1/2 was obtained for the interlayer thickness of 0.53 μm. In addition, the composites prepared by the PIP process exhibited superior mechanical properties over the composites prepared by the chemical vapour infiltration and vapour silicon infiltration (CVI-VSI) process.     

Analysis of a modified microbond test for the measurement of interfacial shear strength of an aqueous-based adhesive and a polyamide fibre

The microbond test was used to measure the interfacial shear strength (IFSS) between a polyamide fibre and a water-based polyurethane. Due to the low viscosity of the water based polyurethane, the droplet could not be formed using a conventional preparation method. A disc shaped microbond droplet forms when an aqueous-based colloidal polymer adhesive was deposited onto the pin hole in a mounting card with a vertical polyamide fibre in the middle after drying and curing at an elevated temperature. Since the droplets were formed with a disc shape, which differs from the conventional ellipsoid, a finite element analysis of the stress distribution at the interface for these contrastingly shaped droplets were calculated and compared. The stress analysis showed that the interfacial shear stress profiles were well matched for both providing confidence that the disc-shaped droplets could be used for interfacial analysis. The microbond test using a disc-shaped droplet was used to study the influences of silane treatment and plasma treatment on the interfacial shear strength between a polyamide fibre and an aqueous deposited polyurethane. The interfacial shear strength of the fibre after plasma treatment was 10.3 MPa, much higher than that of the control and the silanised fibres, 5.2 MPa and 5.4 MPa respectively. The results showed that the microbond test could be used to investigate the interfacial properties of the polyamide fibre and water-based polymer adhesive.     

聚醚分子量对PUA光固化胶黏剂性能的影响

采用不同分子量的聚醚合成了聚氨酯丙烯酸酯预聚体,加入其他助剂配制成光固化胶黏剂。傅里叶红外光谱表明,C=C双键有效地参与了光固化反应;透光率测试显示,聚乙二醇分子量增大,光固化后胶黏剂的透光率降低,聚醚分子量小于1000时,变化不大;DSC曲线表明,预聚体中聚醚分子量越大,玻璃化温度越低;TG曲线表明,不同分子量的聚乙二醇对胶黏剂的热稳定性区别不大;剪切强度证明,随着聚乙二醇分子量的增加,胶黏剂的剪切强度下降,聚乙二醇分子量为600时,剪切强度为1547N,且为本体破坏。聚醚分子量为600～1000时,胶黏剂具有最佳的综合性能。     

Alumina coating formed on medical NiTi alloy by micro-arc oxidation

Al₂O₃ coatings were prepared on NiTi alloy by micro-arc oxidation in an aluminate solution. Thin-film X-ray diffraction (TF-XRD) indicated that the coating consisted of only Al₂O₃ crystal phase. Energy dispersive X-ray spectrometer (EDS) showed that there was about 2.53 at.% Ni in the surface layer, which was greatly lower than that of NiTi substrate. Scanning electron microscopy (SEM) showed that the coating exhibited a typical porous surface and excellent adhesive interface between the coating and the substrate. Direct pull-off test showed that the coating had a mean coating-substrate bonding strength of 28 ± 2 MPa. The results of electrochemical impedance spectroscopy (EIS) study and potentiodynamic polarization test indicated that the corrosion resistance of the coated sample was increased by two orders of magnitude compared with uncoated sample.     

Thermal,mechanical and rheological properties of polylactide toughened by expoxidized natural rubber

This paper concerns on the use of epoxidized natural rubber (ENR) as toughening agent for polylactide (PLA). ENR with epoxidation content of 20 mol% (ENR20) and 50 mol% (ENR50) were separately melt blended with PLA using an internal mixer. DSC results suggested that PLA/ENR blends were amorphous after melt blending while they were crystalline and revealed two melting peaks in the thermograms after being annealed at 100 °C. Mechanical tests showed that the introduction of ENR reduced the tensile modulus and strength but enhanced the elongation and the impact strength of PLA. The impact strength of the 20 wt% ENR20/PLA and ENR50/PLA blends increased to 6-fold and 3-fold, respectively, compared to that of pure PLA. This enhancement was due to a good interfacial adhesion between ENR and PLA. Both ENR20/PLA and ENR50/PLA blends performed very strong shear thinning behavior, and the complex viscosity, storage and loss modulus of the blends also increased after blending with ENR.     

Impact of carbon black substitution with nanoclay on microstructure and tribological properties of ternary elastomeric composites

Various particulate composites based on epoxidised natural rubber (ENR), carbon black (CB), and nanoclay (NC) were prepared keeping the total filler content constant at 35 phr (parts per 100 g rubber). Tribology and hysteretic (stress–strain) properties of the composites were analyzed. Morphology of these composites were also characterized by small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) to establish the structure–property correlations. SAXS results reveal enhancement in overall interfacial roughness (ds) with the increased substitution of CB by NC. Increased CB–NC interface causes enhancement in ds, leading to reduction in wear resistance of ternary composites. Reduction of wear resistance for NC populated samples is attributed to lower dispersion parameter (D_0,1) values of NC in the matrix, realized through image analysis of TEM photomicrographs. Thus, for ternary particulate samples, a definite interrelation among the extent of wear, ds and D_0,1 is realized. Frictional force (F_T) and its adhesive component (F_A) increase when CB is substituted by NC up to 15 phr. When NC fraction exceeds 15 phr, both F_T and F_A decrease substantially. This is attributed to the lubricity offered by the modified NC at higher NC concentration, which is explained using a predictive mechanism.     

Interfacial strength and fracture energy of individual carbon nanofibers in epoxy matrix as a function of surface conditions

The interfacial shear strength (IFSS) and fracture energy of individual carbon nanofibers embedded in epoxy were obtained for different surface conditions and treatments by novel, MEMS-based, nanoscale fiber pull-out experiments. As-grown vapor grown carbon nanofibers (VGCNFs) with turbostratic surface and 5 nm peak-to-valley surface roughness exhibited high IFSS and interfacial fracture energy, averaging 106 ± 29 MPa and 1.9 ± 0.9 J/m², respectively. Subsequent high temperature heat treatment and graphitization resulted in drastically reduced IFSS of 66 ± 10 MPa and interfacial fracture energy of 0.65 ± 0.14 J/m². The smaller IFSS values and the reduced standard deviation were due to significant reduction of the fiber surface roughness to 1–2 nm, as well as a decrease in surface defect density during conversion of turbostratic and amorphous carbon to highly ordered graphitic carbon. For both grades of VGCNFs failure was adhesive with clear nanofiber surfaces after debonding. Oxidative functionalization of high temperature heat-treated VGCNFs resulted in much higher IFSS of 189 ± 15 MPa and interfacial fracture energy of 3.3 ± 1.0 J/m². The debond surfaces of functionalized nanofibers had signs of matrix residue and/or shearing of the outer graphitic layer of the VGCNFs, namely the failure mode was a combination of cohesive matrix and/or cohesive fiber failure which contributed to the high IFSS. For all three grades of VGCNFs the IFSS was independent of fiber length and diameter. The findings of this experimental study emphasized the critical role of nanofiber surface morphology and chemistry in determining the shear strength and fracture energy of nanofiber interfaces, and shed light to prior composite-level strength and fracture toughness measurements.     

Corrosion protection of ENIG surface finishing using electrochemical methods

Four types of thin film coating were carried out on copper for electronic materials by the electroless plating method at a pH range from 3 to 9. The coating performance was evaluated by electrochemical impedance spectroscopy and potentiodynamic polarization testing in a 3.5 wt.% NaCl solution. In addition, atomic force microscopy and X-ray diffraction were also used to analyze the coating surfaces. The electrochemical behavior of the coatings was improved using the electroless nickel plating solution of pH 5. The electroless nickel/immersion gold on the copper substrate exhibited high protective efficiency, charge transfer resistance and very low porosity, indicating an increase in corrosion resistance. Atomic force microscopy and X-ray diffraction analyses confirmed the surface uniformity and the formation of the crystalline-refined NiP {1 2 2} phase at pH 5.     

Moisture absorption,tensile strength and microstructure evolution of short jute fiber/polylactide composite in hygrothermal environment

In this research, aging behaviors of short jute fiber/Polylactide (PLA) composite material in hygrothermal environment were investigated. The material was fabricated by using film stacking hot pressed method. The aging was carried out for uncoated samples and adhesive tape coated samples in saturated vapor at 70 °C. Moisture absorption rates of the samples were measured during the aging process. It is found that the moisture absorption process of uncoated samples includes three stages: a short and quick moisture uptaking stage, a slow stable uptaking stage and an abrupt very quick moisture uptaking stage. Microstructures of the samples in different aging stages were observed. The main defects occurred during the aging process include pores, microcracks, delamination and complete relaxation in the whole structure. The results reveal that the moisture absorption and aging process can be effectively retarded by coating. The molecular weight measurement by gel permission chromatography (GPC) indicated that the PLA matrix was severely degraded in hygrothermal environment. Tensile strength severely decreased after aging.     

Atomistic simulations of shearing friction and dynamic adhesion of double-walled carbon nanotubes on Au substrates

Functional gecko-mimetic adhesives have attracted a lot of research interest in recent years. In this paper, the physical adhesion behavior of (5, 5)@(10, 10) double-walled carbon nanotubes (DWCNTs) on an Au substrate is investigated by performing detailed, fully atomistic molecular dynamics (MD) simulations. The effects of adhesion temperature, tube length, and peeling velocity on the binding energy, normal adhesion force, lateral shearing friction, and adhesion time are thoroughly analyzed. The simulation results indicate that the binding energy (per unit length) of the DWCNT–Au adhesive system is −26.7 × 10⁻² eV/Å, which is 7.2% higher than that of single-walled counterparts. The tip-surface adhesion force for a single DWCNT is calculated to be 1.4 nN, and thus the adhesive strength of a DWCNT array is about 1.4 × 10¹–1.4 × 10³ N/cm² (corresponding to an aerial density of 10¹⁰–10¹² tubes/cm²). Two distinctive friction modes, namely (i) sliding friction (by the nanotube wall) and (ii) sticking friction (by the nanotube tip), are elucidated in term of the phase relationship of atomic friction forces. Moreover, the effective Young’s moduli of double- and single-walled CNTs are obtained using MD simulations combined with Euler–Bernoulli beam theory. The calculation results show good agreement with previously reported numerical and experimental results.     

Bias effects on the tribological behavior of cathodic arc evaporated CrTiAlN coatings on AISI 304 stainless steel

In this study, CrTiAlN coatings were deposited on AISI 304 stainless steel by cathodic arc evaporation under a systematic variation of the substrate bias voltage. The coating morphology and properties including surface roughness, adhesion, hardness/elastic modulus (H/E) ratio, and friction behavior were analyzed to evaluate the impact of the substrate bias voltage on the coating microstructure and properties. The results suggest that for an optimized value of the substrate bias voltage, i.e. − 150 V, the CrTiAlN coatings showed increased Cr content and improved properties, such as higher adhesion strength, hardness, and elastic modulus in comparison to the coatings deposited by other substrate bias voltage. Moreover, the optimum coatings achieved a remarkable reduction in the steel friction coefficient from 0.65 to 0.45.     

Mesoporous titania films with adjustable pore size coated on stainless steel substrates

Mesoporous layers of titania were prepared on stainless steel substrates of defined roughness by dip coating. Ordered arrays of micelles formed from amphiphilic block copolymers served as pore templates during film drying. Coating of the precursors solution on freshly grinded steel resulted in extensively fractured films with severely distorted templated porosity. In contrast, films produced on precalcined steel showed good integrity, high substrate coverage and narrow pore size distribution with pores interconnected and ordered in a short range. This difference in film quality and morphology was ascribed to the reaction between template polymers and metal ions leached from the steel of grinded substrate surfaces. Films were ca. 700 nm thick and composed of nanocrystalline titania. The pore size of titania coatings was varied between 5 and 16 nm employing polymer templates of different structure and molecular weight.     

Tensile and impact-toughness behaviour of cryorolled Al 7075 alloy

The effects of cryorolling and optimum heat treatment (short annealing + ageing) on tensile and impact-toughness behaviour of Al 7075 alloy have been investigated in the present work. The Al 7075 alloy was rolled for different thickness reductions (40% and 70%) at cryogenic (liquid nitrogen) temperature and its mechanical properties were studied by using tensile testing, hardness, and Charpy impact testing. The microstructural characterization of the alloy was carried out by using field emission scanning electron microscopy (FE-SEM). The cryorolled Al alloy after 70% thickness reduction exhibits ultrafine grain structure as observed from its FE-SEM micrographs. It is observed that the yield strength and impact toughness of the cryorolled material up to 70% thickness reduction have increased by 108% and 60% respectively compared to the starting material. The improved tensile strength and impact toughness of the cryorolled Al alloy is due to grain refinement, grain fragments with high angle boundaries, and ultrafine grain formation by multiple cryorolling passes. Scanning electron microscopy (SEM) analysis of the fracture surfaces of impact testing carried out on the samples in the temperature range of −200 to 100 °C exhibits ductile to brittle transition. cryorolled samples were subjected to short annealing for 5 min at, 170 °C, and 150 °C followed by ageing at 140 °C and 120 °C for both 40% and 70% reduced samples. The combined effect of short annealing and ageing, improved the strength and ductility of cryorolled samples, which is due to precipitation hardening and subgrain coarsening mechanism respectively. On the otherhand, impact strength of the cryorolled Al alloy has decreased due to high strain rate involved during impact loading.     

Enchanced high-temperature performances of SiC/SiC composites by high densification and crystalline structure

We report the enchanced in situ performances of tensile strength and thermal conductivity at elevated temperatures of the PCS-free SiC/SiC composite with a high fiber volume fraction above 50% fabricated by NITE process for nuclear applications. The composite was fabricated by the optimized combination of the fiber coating, the matrix slurry and the pressure-sintering conditions, based on our previous composites’ study history. The composite showed the excellent tensile strength up to 1500 °C, that it retained approximately 88% of the room-temperature strength. Also, the thermal conductivity of the composites represented over 20 W/m K up to 1500 °C, which was enough high to take the advantage of the assumed design value for nuclear applications. Microstructural observation indicated that the excellent high-temperature performances regarding tensile strength and thermal conductivity up to 1500 °C were the contribution to the high densification and crystalline structure in matrix.