ABSTRACTIn this study, a laser surface pre-treatment strategy was applied to aluminium 7075-T6 alloy, in which the laser power, speed and frequency were varied to determine the best modified surface property in terms of surface wettability. Surface texture, topography, roughness, contact angle and adhesive bonding strength of the treated surface were measured and characterised. Results showed that the laser-treated surface at a laser power of 30 W, speed of 1.2 m/s and frequency of 8 kHz provided the highest surface wettability by showing the lowest contact angle of 17°, which was attributed to the deeper surface cavities and higher surface roughness. The laser treatment increased the adhesion strength up to 8.5 MPa which was 45% higher than that of the untreated surface (of 5.9 MPa). Its adhesion strength nearly matched with that of the oxalic acid treatment. The laser-treated failed specimen shows predominantly adhesion–cohesion failure mode with a strong interfacial bonding. FTIR spectra confirmed the presence of required functional chemical groups of the adhesive after curing, demonstrating a strong bonding force and affinity between the adhesive and the modified surface. The findings clearly indicate that the laser surface pre-treatment would be a viable surface modification strategy without environmental and health hazard to provide adequate strength in the adhesively bonded joints.

ABSTRACTExperimental and theory investigations on the effects of single-phase (PyC) and co-deposited (PyC+SiC) interphases on the mechanical properties of T700TM-C/SiC minicomposites were conducted. Monotonic tensile tests and fiber’s push-in tests were conducted to obtain the minicomposite’s macro tensile mechanical properties and micro interface properties. The tensile strength was analyzed via a two-parameter Weibull distribution. The failure mechanism was obtained by fiber’s push-in tests and characterized by fracture morphology, and a damage-based micromechanical constitutive model was adopted to predict the tensile stress-strain response and interface debonding ratio (η) of C/SiC minicomposites with different interphases. For C/SiC, the experimental tensile curves were linearly till final tensile fracture with the lowest tensile strength and failure strain, due to the low interface shear strength (i.e., τiss = 50.8 ± 15.3 MPa). For C/(PyC)300 nm/SiC, the minicomposite with the moderate ISS (i.e., τiss = 62.2 ± 5.9 MPa) possessed the highest tensile strength and failure strain with the highest interface debonding ratio (i.e., ηmax = 0.95). For C/(PyC+SiC)/SiC, the tensile strength and strain were both lower than those of C/(PyC)/SiC due to the lower η.

ABSTRACTUnderstanding the microscopic adhesion behaviour and mechanism of waterborne epoxy resin emulsified asphalt (WEREA) at the aggregate interface is quite significant for improving the service life of pavements. This work created an interface model of WEREA and aggregate using molecular dynamics (MD) simulation to examine the interface adhesion behavior. The interface model based on MD simulation was used to evaluate the distribution characteristics of asphalt components on the aggregate surfaces by calculating the thermodynamic properties, radial distribution function (RDF), relative concentration (RC) distribution and mean square displacement (MSD). The results show that WEREA has better thermodynamic characteristics than base asphalt and has components with much better self-polymerization behaviour. WEREA adheres more tightly to alkaline aggregates than acidic ones. Van der Waals forces dominate interfacial adhesion to acidic aggregates, while that to alkaline aggregates is dominated by electrostatic forces. Interfacial water damage is a spontaneous reaction. Moisture has a substantial influence on asphalt – aggregate adhesion, especially with alkaline aggregates. This work provides an effective method for exploring WEREA – aggregate adhesion.

ABSTRACTAccording to EURO IV and EURO V, benzene in gasoline should not exceed 1 volume%, to prevent environmental pollution and health risks; hence benzene must be removed from pyrolysis gasoline (octane booster), before blending with gasoline. Polyvinyl alcohol (PVA) based membranes are quite effective for pervaporative separation of hydrocarbon mixtures. The main objective of this work is to fabricate insitu Ag/PVA nanocomposite membranes, using simple solution casting approach, for pervaporative separation of benzene from model pyrolysis gasoline (mixture of benzene/1-octene). Debenzenation of pyrolysis gasoline using PVA-based polymeric membranes was not reported by earlier researchers. The impact of incorporation of nano-Ag in the PVA matrix, on the pervaporative performance of the PVA membrane towards benzene, based on the swelling coefficient, fractional free volume, total flux, separation factor and activation energy, is the novelty of this study. Scanning Electron Microscopy, Transmission Electron Microscopy, mechanical strength, UV-Vis spectroscopy, Fourier Transform Infrared Spectroscopy were used to characterize all the fabricated membranes. The most suitable composite membrane for the intended purpose was identified. The maximum flux and highest separation factor of the said membrane are 4.05 kg/m2/h and 5.51 respectively at 343K operating temperature and 1 mm Hg downstream pressure.

ABSTRACTThe use of printed paper electronics in consumer goods is expected to experience a mass development in the next future. The ink used in these devices contains silver nanomaterials that may be released into the environment at the product end-of-life. We report here the first evaluation of the fate of silver during a pilot-scale recycling of printed paper electronics, made of paper printed with a cellulose nanofibrils-silver nanowire ink. We show that the released effluents are mainly free from silver, which is retained in the pulp conserved for recycling. We use atomic force microscopy experiments to show that this strong pulp-silver bond is due to the embedding of the silver nanowires in the pulp by coils of cellulose nanofibrils. We propose an estimate of the resulting adhesion stress of the nanowires to the ink, high enough to keep the silver inside the pulp during the recycling procedure.

ABSTRACT3D-Network SiC ceramic was prepared using a polymer sponge replica technique with SiC ceramic slurry (77 wt% solid content). The triangular hole defects in 3D-Network SiC ceramic were reduced and the mechanical properties were improved by high-pressure spraying and vacuum infiltration. The 3D-Network SiC/Cu composite material was fabricated by the gravity casting technique, and the interfacial bonding and abrasion resistance of the composites were tested and analyzed. The results show that the compressive strength of high-pressure sprayed 3D-Network SiC ceramic increased slightly from 0.67 Mpa to 0.74 Mpa due to the triangular hole defects left when the polymer sponge was decomposed at high temperatures. The mechanical properties of 3D-Network SiC ceramics that have been vacuum infiltrated in alumina and a mixture composed of alumina and andalusite were greatly improved, and their compressive strength was increased to 1.02Mpa and 1.57Mpa, respectively. The interface between SiC and Cu in the 3D-Network SiC/Cu composites prepared by different processes shows excellent bonding, and the abrasion resistance of the 3D-Network SiC/Cu composites prepared by different processes was 2.02–9.18 times that of pure copper respectively.

ABSTRACTThe service conditions of high temperature and heavy load of aero-engine require high-temperature self-lubricating composites with high strength, low wear and long life. Hence, the high-level objective of this study is to regulate the interface between the substrate and hexagonal boron nitride (h-BN) lubricant in GH4169 nickel-based high-temperature self-lubricating composites to improve the interfacial bonding strength and the overall performance. Electroless plating method was adopted to coat nickel on h-BN, and the dense high-temperature self-lubricating composites were fabricated through hot-pressing sintering. The effects of nickel coating on h-BN on the microstructure, mechanical properties and high-temperature tribological behaviors of composites were analyzed in detail, and the lubrication mechanism was also elucidated. The results illustrate the Ni@h-BN/GH4169 composites with addition of chemically modified lubricant particles have excellent mechanical properties and lubrication and wear reduction properties, compared to h-BN/GH4169 composites. This is mainly due to the introduction of nickel coating contributed to the distribution uniformity of h-BN in the matrix, and the wettability between h-BN and the substrate together with interfacial bonding strength were enhanced as well. This work provides an insight to overcome the challenges facing the technology when using GH4169 nickel-based self-lubricating composites in manufacturing of mechanical components in aerospace.

ABSTRACTThe accurate prediction of gas separation properties of mixed matrix membranes (MMMs) is essential to eliminate the tedious experimental work. In this work, a new model is proposed to predict the gas permeability of MMMs, considering the role of interface voids between the polymer matrix and inorganic fillers. The new model is developed based on an analogy with a model derived for thermal conduction through the particulate composites using effective medium theory. The new model is validated using the gas permeability data of four sets of MMMs containing spherical micro- or nano-fillers reported in the literature. The results show an excellent agreement between new model predictions and gas permeability experimental data with deviations lower than 10% in comparison with the other models (29–43%). In addition, the value of the thickness of the interface voids layer for MMMs, which is difficult to directly determine by experimental methods, is correctly predicted using the new model. Therefore, a new theoretical model named as renovated Maxwell model considering the effect of filler/polymer interface voids is developed to accurately predict the gas permeability of MMMs.

ABSTRACTIn order to increase the interfacial adhesion between polybutylene succinate and coconut shell particles, two kinds of chemical treatment of coconut shell particle were carried out. Firstly, a 5% sodium hydroxide treatment and secondly, a 2% sodium hydroxide plus silane coupling agent treatment. The possibility of increasing matrix adhesion has also been explored through addition of polycaprolactone to polybutylene succinate as a matrix. Composites were produced using extrusion prior to injection moulding. The results show that, compared with neat polybutylene succinate, composites with low percentage of particle loading have a higher tensile strength and strain at break despite their lower elastic modulus. A higher elastic modulus can be obtained for composites with higher particle loadings through sacrifice of their ductility. The same trend is observed for composites with the polymer-blend matrix. Scanning electron micrographs show good adhesion between particle and matrix for particles that undergo the second treatment. At low percentage of particle addition, the crystallinity of the composites is higher than the neat polybutylene succinate, however melting temperature is less affected by the addition of reinforcement. Rheological properties such as storage modulus, loss modulus and complex viscosity of the composites are higher than for neat polybutylene succinate.

ABSTRACTPLA/HAP composites have attracted significant attention in material science, especially in the field of biomaterials. However, these composites have suffered from unfavorable interface interactions between PLA and HAP interfaces, which limits the applications . In this study, we aimed to improve the interface interactions of PLA/HAP composite by modifying the HAP surface. For this purpose, HAP particles were functionalized with three different silane modifying agents, including (3-Aminopropyl)trimethoxysilane (AMMO), (3-glycidyloxypropyl)trimethoxysilane (GLYMO) and (3-triethoxysilyl)propylsuccinic anhydride (GF-20). The obtained modified HAP (m-HAP) were used to prepare PLA/m-HAP. Interface interactions of composites were characterized by Fourier transform infrared spectrophotometer (FT-IR) and differential scanning calorimetry (DSC). In addition, Vickers hardness tests were performed to reveal the effect of silane modifying agents on hardness before and after the in vitro degradation test.

ABSTRACTTo improve the performance of traditional oil absorption materials, a novel concept is proposed for the fabrication of composite oil absorption materials with three-dimensional porous structure via a double Pickering emulsion template. Oil‐in‐water‐in‐oil type double Pickering emulsion is prepared with modified attapulgite (ATP) and modified Fe3O4. Then, the Pickering emulsion as a template is synthesized ATP/P(EHMA-St)/Fe3O4 composite porous materials. The influences of the amount of inorganic additives-modified ATP, initiator, cross-linking agent, and oil–water ratio on the oil absorption rate and oil retention rate of the material were studied. It showed that under the conditions of polymerization temperature of 80°C and reaction time of 6 h, the morphology of the material was the best and the oil absorption rate was the largest with the content of modified ATP, nano Fe3O4, DVB, and BPO of 0.20%, 0.10%, 1.20%, and 0.32%, respectively, and the oil–water ratio of 1:5. The absorption of diesel oil can reach 986.65%, and the oil retention rate of material can reach 82.37%. Our work provides a novel strategy for the preparation of composite porous materials, which is expected to be popularized and applied in oil spill treatment and oily wastewater treatment.

ABSTRACTThis paper aims to develop a novel approach to determining the fiber/matrix interfacial shear strength (IFSS) due to both carbon fiber roughness and the presence of carbon nanotubes (CNTs) in the matrix of a polymer composite in the form of a fiber overwrap. Under an atomic force microscope (AFM), the carbon fiber surface exhibits multi-scale asperities extending from a nanometer to several microns, likely caused by shrinkage during the graphitization process. Therefore, a Fourier series decomposition of the surface asperity data is performed to model these asperities present at various wavelengths on the fiber resulting in an amplitude and wavelength corresponding to each Fourier series term, effectively capturing the surface roughness over the entire spectrum of wavelengths. Furthermore, Molecular Dynamics (MD) simulations were performed to determine the interfacial shear strength of any subcomponent asperity of a specific amplitude and wavelength. Using MD data, governing equations were developed to compute the length-scale-averaged shear strength for a carbon fiber with any given surface asperities from the interfacial shear force for each of these subcomponent wavelengths. The results show that the presence of CNTs enhanced the IFSS by about 19% overall for a given surface asperity profile compared with the case without CNTs.

ABSTRACTNatural fiber-reinforced polymer composites are presently receiving the attention of scholars and industrialists due to their specific properties, such as being naturally eco-friendly, biodegradable, economical, viable, available, and sustainable. The key problems associated with natural fiber polymer composites, including fiber/matrix compatibility, high moisture absorption, and, especially, thermal degradation in engineering plastics (high-temperature plastics), constitute the most critical thrust of this review. It is noted that at high temperatures, natural fibers degrade and this has adversely restricted their usage with only commodity thermoplastics having relatively low melting temperatures, such as polypropylene (PP) and polyethylene (PE). This review paper, therefore, provides valuable research highlights on utilizing and improving the mechanical and thermal properties of natural kenaf fibers as reinforcement in engineering polymer composites for high-temperature engineering applications using polymer matrices, such as polyethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), and polyphenylene ether (PPE). The initial and various chemical treatments of natural fibers, their effect on the thermal and performance properties of natural fiber engineering thermoplastic composites, and the advanced treatment of epoxy coatings are reviewed. Applications of natural fiber-reinforced thermoplastic composites in the construction and automotive industries, as well as in other applications, are outlined. It was established that the adhesion and thermal stabilities between polymer matrix and natural fibers are better improved by surface coating with diluted epoxy resin thermoset. This eventually improved the overall thermal and performance properties of the resultant composites and will serve as a data bank and guide for manufacturers and future research directions using high-end engineering polymers with higher processing temperatures.

ABSTRACTIn this study, the preparation of thermally stable organic-inorganic hybrid nanocomposites from chemically functionalized oxidized graphite is carried out by in-situ catalytic oxidative decarboxylation of 3,5-dinitrobenzoic acid (reactant) in the presence of potassium persulfate (oxidant), silver nitrate (catalyst) and graphite (support) under thermal or microwave conditions. The effects of heat transfer and dosages of reactant, catalyst and oxidant on the crystalline structure and the morphology of nanocomposites are studied in detail. The prepared nanocomposites are characterized by EDS, elemental mapping, FE-SEM, FT-IR and XRD. The thermal stability of nanocomposites is examined by TGA and DSC. EDS shows that nanocomposites are composed of C, O, N, S, K and Ag elements. FT-IR exhibits that the graphitic layers in nanocomposites are mainly oxidized and functionalized with carboxyl, carbonyl, hydroxyl, epoxy, sulfate, nitrate and nitroaryl groups. Addition of nitroaryl groups to nanocomposites is also supported by an increase found in their C and N contents. XRD demonstrates the coexistence of both oxidized amorphous carbon and graphite in combination with different levels of organic and inorganic phases. The prepared nanocomposites show good thermal stability. The total area of the DSC curve in these nanocomposites compared to graphite is enhanced.

ABSTRACTAmphiphilic Silane coupling agent (SCA) improves the weak bond between the two phases of rubber and hydration products, fills the interfacial gaps and effectively repairs the interfacial defects between rubber and hydration products. The addition of PVA fibers mainly improves the cracking performance and durability of concrete. However, most of the studies addressing this issue have been limited to phenomenology, ignoring the mechanism of action at the atomic structure level. Therefore, this study investigates the strengthening mechanism of the interfacial properties of KH-560 coupling agent-reinforced PVA fiber-rubber concrete from the multi-scale analysis of macro-mechanical properties, micro and fine structure, chemical composition and nano-optical level. Based on the results of macro-mechanical tests, it was found that the KH-560 coupling agent could improve the compressive, flexural and shear strength of PVA-rubber concrete, so that the damage morphology also changed from brittle damage to plastic damage, and the compressive strength of concrete was slightly reduced due to the addition of PVA, but the durability and cracking resistance were enhanced. XRD (X-ray diffraction), FT-IR (Fourier transform infrared spectroscopy) and SEM (scanning electron microscopy) tests observed the presence of some gels and polymers that filled the interfacial slits and effectively repaired the interfacial defects. The two-phase interface was simulated by molecular dynamics at the nano level, and it was found that KH560 molecules could be closely connected with C-S-H gel collectively through Si-O-Si chemical bonding, and KH560 molecular bonds were unevenly distributed between the C-S-H and rubber interfaces, while the addition of modifier KH560 and PVA fibers caused more hydrogen and ionic bonds at the interface, which enhanced the interfacial interaction energy. Systematic experiments were conducted on PVA fiber-rubber soil materials before and after SCA modification under macroscopic, microscopic, fine and nano-level multi-scale analyses, which ultimately lead to the design and performance improvement of SCA modification of PVA-rubber cement-based materials in a multi-scale framework. The graphic summary is shown in Figure 1.

ABSTRACTIn the present work, stress-dependent matrix crack opening behavior of SiC/SiC composites was analyzed considering stochastic fragmentation in fibers. The stochastic matrix multiple fragmentation model was adopted to determine the fragmentation lengths of three different types, the accompanying interface debonding process was assessed by the fracture mechanics theory, and stochastic fiber fragmentation was determined by the global load sharing (GLS) criterion. Considering the aforementioned multiple micro-damage mechanisms, matrix crack opening displacements (CODs) in different matrix fragmentation states were determined using a micromechanical technique. Relationships between CODs and the constituent properties of SiC/SiC composites with fiber fragmentation were established. The crack opening behavior of SiC/SiC composites was also analytically predicted. Effects of fiber stochastic fragmentation on crack opening-related damage parameters were examined.

ABSTRACTThe current research aimed to investigate the different aspects of novel nanocomposites based on carboxylated acrylonitrile butadiene rubber (XNBR), carboxylated styrene butadiene rubber (XSBR), graphene oxide (GO), and glycidyl methacrylate-grafted XNBR compatibilizer (XNBR-g-GMAC) blend. For this purpose, the novel nanocomposites of GO-XNBR-g-GMAC/XNBR/XSBR with different XNBR, XSBR, and GO composition and with and without XNBR-g-GMAC were synthesized. The related characteristics including curing properties, swelling behavior, morphological, electrical and mechanical characteristics were studied through rheometry, swelling test, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) observation, electrical resistivity, mechanical test, dynamic mechanical thermal analysis (DMTA), etc. Results of rheometric tests revealed that the addition of XNBR-g-GMAC and increasing GO content reduces the scorch time (t5) and optimum cure time (t90) and increases the crosslink density (CLD). So that the addition of 5 phr of compatibilizer and 1 phr of GO to the XNBR75/XSBR25 blend reduced the t5 and t90 by 29% and 34%, respectively. TEM micrograph confirms the GO dispersion in rubber matrix and SEM observation shows that incorporation of XNBR-g-GMAC and GO reduces dispersed-phase droplet size due to the improved compatibility of XNBR and XSBR. According to the DMTA result, all the samples except XNBR/XSBR (without XNBR-g-GMAC) show one glass transition temperature (Tg) which means XNBR-g-GMAC successfully enhanced the compatibility of XNBR/XSBR. The mechanical properties of samples showed that by the increase of GO concentration tensile strength, elongation at break, modulus, fatigue life, and hardness increased. Testing surface temperature changes in constant voltage (75 V) showed that the addition of 0.3 phr GO showed the best result and the further increase of GO up to the value of 1 phr revealed the opposite result and caused a decrease of about 54%. The results of practical tests also confirm the theories.

ABSTRACTSilica-coated limestone (SCL) microcapsule was synthesized and successfully introduced into acrylic resin to produce fire-retardant coatings. SCL microcapsules were prepared by encapsulating limestone granules with silica nanoparticles using epoxy resin as a binder. The morphology and the chemical composition of the SCL microcapsules were confirmed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), respectively. The performance of SCL microcapsules on mechanical, flame retardant and thermal stability of the coatings was thoroughly investigated using FTIR, SEM, thermogravimetric analysis (TG), smoke density test, adhesion pull-off test, pendulum damping test and cone calorimeter test. The results shows that while the adhesion strength, pendulum hardness and limiting oxygen index (LOI) increased remarkably, the values of flame spread ratings (FSR), specific optical density (ODs), heat release rate (HRR), total heat release rate(THRR), smoke production rate (SPR) and total smoke production rate (SPR) decreased significantly with the introduction of SCL microcapsules. The TGA results confirm that incorporation of SCL microcapsules increases the thermal stability and boosts formation of large char layers.

ABSTRACTRubber concrete (RC) is a new environmentally friendly composite material, there are many weak interfaces and pores inside it, which degrade its mechanical properties. To address this problem, this study coordinates the modification of RC with carboxy styrene butadiene latex (CSBL) and polyvinyl alcohol (PVA) fibers to improve its mechanical properties. From mechanical properties experiments, it was found that 0.6% cement mass of PVA fiber and 10% cement mass of CSBL could increase the compressive and shear strengths by 12.4% and 30%, respectively. A series of microscopic tests (Scanning Electron Microscope-SEM, X-ray diffraction-XRD, Fourier Transform Infrared Spectrometer-FTIR) revealed that PVA fibers limited the development of cracks and CSBL caused further hydration of unhydrated cement to produce more cement gel, which in turn filled the internal pore structure of concrete. Molecular dynamics simulation techniques were used to create hydrated calcium silicate (C-S-H)/CSBL, rubber/CSBL and PVA/CSBL models. Dynamic and static simulations of the interfaces based on the above models revealed that CSBL is used to enhance the bonding between materials through a large number of stable hydrogen and ionic bonds. In this study, the enhanced RC is analyzed at multiple scales, which provides experimental and theoretical support for its application in engineering.

ABSTRACTSeveral research articles in the field of nanocomposite have revealed that organic fillers can be used as reinforcing agents for plastic materials in hybrid material production. Advancement in multifunctional materials is anticipated to grow with the advent of lightweight, low-cost, and sustainable materials with improved mechanical, fire retardancy, water resistance, and higher barrier properties. As reported in the literature, these performance properties could be obtained by reinforcing nanoclay/organic filler in polymeric matrices. In this report, the pretreatment techniques for overcoming the challenges of hybrid composite production are discussed in detail. The bonding mechanisms between the nanoclay and plastic materials are explained. The study gives an overview of the recent progress on multifunctional hybrid materials made using nanoclay/organic particulate fillers as reinforcements for polymer matrices intended for use in the automotive, building, and construction industries.