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SURFACE preparation, MANUFACTURING processes, SHEAR strength, ADHESIVES, STEEL, and ADHESION

In this paper, the manufacturing and mechanical properties of steel-carbon fiber reinforced polymer (CFRP) hybrid composites were investigated. Steel-CFRP hybrid composites with different manufacturing processes were prepared to obtain different shear strength based on steel surface treatment (abrasion and grit blasting) and adhesive-bonding process. Single lap shear tests reveal that the steel/CFRP adhesion property can be improved by using grit blasting surface treatment on steel and introducing an adhesive layer at the interface. The steel/CFRP adhesion has no significant effect on the tensile and flexural properties of the hybrid composites, while the steel/CFRP interface failure occurs during interlaminar shear tests. [ABSTRACT FROM AUTHOR]

FIBROUS composites, NATURAL fibers, MACHINABILITY of metals, CELLULOSE, WATER jets, and SCANNING electron microscopy

In the current scenario, the applications of natural fibers are increasing enormously due to their biodegradability, low-density and better mechanical properties. This research explains the machining nature of pineapple (P) and flax (F) fibers by the incorporation of cellulose micro filler (CMF). These epoxy-based composites were manufactured using compression moulding. In the machining process using abrasive water jet machining (AWJM), lower kerf angle of 1.31° and surface roughness of 5.1 µm were observed in 30% PF/2% cellulose micro filler hybrid epoxy combination. Agglomeration at higher filler incorporation causes decrease in machinability of hybrid 30% PF. Pineapple and flax hybrid fibers with 30 and 35 wt % showed better machinability at 2 and 3% cellulose micro filler addition. Scanning electron microscopy analysis after machining process showed reduction in flush off and pullouts of fiber by improved compaction with the epoxy matrix due to filler addition. [ABSTRACT FROM AUTHOR]

SILANE, TREATMENT effectiveness, COMPRESSION molding, FLOUR, ABSORPTION, PLASTIC scrap recycling, and THERMAL properties

Rubberwood flour (RWF) was treated by alkaline, silane, and alkaline–silane, and consequently, reinforced recycled polypropylene (rPP) composites. The wood–plastic composites (WPCs) were prepared with 40 wt% RWF content using a twin-screw extruder, followed by compression molding. Silane treatment was applied at various concentrations and treatment times to evaluate the effect of treatment conditions on water absorption, mechanical properties, thermal properties, and morphological characterization of WPCs. The results indicated that alkaline–silane treatment of RWF exhibits higher properties in comparison to silane or alkaline only. In addition, silane concentrations significantly affected water absorption, mechanical strength, and hardness, while treatment times remained relatively unaffected by these properties. The best water resistance, mechanical strength, and hardness of WPCs were achieved by alkaline–silane treatment with 5% silane concentration for 2 h, which improved the interfacial adhesion of RWF and rPP as well as increased the crystallinity in the WPCs. [ABSTRACT FROM AUTHOR]

ORGANOCLAY, POLYHYDROXYBUTYRATE, THERMAL properties, NEWTONIAN fluids, FLEXURAL modulus, TRANSMISSION electron microscopy, and PSEUDOPLASTIC fluids

Polyhydroxybutyrate (PHB), a bio-derived and biodegradable polyester, has the potential to be a substitute for traditional polymers. PHB was modified with montmorillonite (MMT), a nanoclay, with the aim of improving its mechanical properties. The clay dispersion, mechanical, rheological and thermal properties of untreated and acid-treated MMT-modified PHB nanocomposites were investigated. Nanocomposite specimens at three different clay loading were prepared using extruder and injection moulding machine. Energy dispersive X-ray mapping revealed that nanocomposites with clay content of 3 phr exhibited better dispersion compared to nanocomposites with higher clay content. The mechanical properties of the MMT-modified PHB, such as the tensile and flexural modulus, were enhanced when compared to neat PHB. From rheology, PHB and PHB nanocomposites modified with untreated MMT exhibited Newtonian fluid behaviour in the tested frequency range. However, for nanocomposites modified with acid-treated MMT, shear thinning behaviour was observed at higher clay content. The nanocomposites also exhibited higher complex viscosity compared to PHB. From transmission electron microscopy analysis, exfoliation of the MMT was observed for the treated MMT nanocomposites at all clay loading. MMT-modified PHB has lower melting temperature when compared to neat PHB. Furthermore, it was found that the addition of MMT influenced the crystallisation behaviour of PHB. The presence of acid-treated MMT also reduced the degree of crystallinity with increasing clay content. [ABSTRACT FROM AUTHOR]

To evaluate human osteoblast metabolic activity cultured in medium conditioned with commercially pure titanium after surface treatments with alumina or ceramic grit-blasting followed by acid etching. Commercially available, pure Grade 4 titanium disks were used and subjected to seven different surface modifications: (1) machined (MA)—used as the control group; (2) blasted with Al2O3 (Al2O3); (3) blasted with sintered ceramic (HAS); (4) blasted with non-sintered ceramics (HA); (5) blasted with Al2O3 and etched with HCl/H2SO4 (Al2O3 DE); (6) blasted with sintered ceramic and etched with HCl/H2SO4 (HAS DE), and (7) blasted with non-sintered ceramic and etched with HCl/H2SO4 (HA DE). A samples roughness evaluation test was carried out with an interference microscope, and energy-dispersive X-ray spectroscopy was performed to evaluate the presence of aluminum, phosphorus, and calcium deposited during the titanium surface treatment along with carbon contaminants acquired by the surface during processing. A culture medium conditioned with the respective samples was prepared in five dilutions, and its effect on human osteoblast cell viability was evaluated using the relative viability of cells. Human osteoblast metabolic activity was found to be the most intensive for the Al2O3 DE sample. The lowest activity was observed for the HAS DE. The material's cytocompatibility depended on both the surface roughness and its chemical composition. Etching had a dual effect on cell activity, depending on the chemical composition of the titanium surface after blasting. [ABSTRACT FROM AUTHOR]

Surface treatments are typical surface protection against corrosion or serve to create an attractive appearance for the end customer. However, the surface to which they are applied must be completely oxide-free, otherwise, defects occur which can cause subsequent corrosion or deterioration of the visual appearance of the product. The parts manufactured by wire electrical discharge machining, however, have a high tendency to oxidize. For this reason, this study was aimed at demonstrating the effect of machine setup parameters (gap voltage, pulse on and off time, wire feed and discharge current) on oxygen occurrence on the surface of two non-metallic (aluminium alloy 7475-T7351, chromium nickel superalloy Inconel 625) and four metallic materials (tool alloy steel X210Cr12, Hadfield steel, Creusabro 4800 and Hardox 400). Within this study, 18 samples were produced, where the chemical composition of energy-dispersive X-ray was analysed, on the basis of which the effect of these parameters on the surface oxidation was proved. [ABSTRACT FROM AUTHOR]

ACRYLONITRILE butadiene styrene resins, CARBON fibers, MACHINE molding (Founding), GLASS transition temperature, LATENT heat of fusion, THERMOGRAVIMETRY, and POLYAMIDES

Carbon fibers (CFs) were surface treated using nitric acid (HNO3). Afterward, polyamide 6/acrylonitrile–butadiene–styrene (PA6/ABS)-based hybrid nanocomposites containing 10 wt% of HNO3-treated short CFs and 0, 2, 5, and 8 wt% of calcium carbonate (CaCO3) nanoparticles were produced using a counter-rotating twin-screw extruder and injection molding machine. Scanning electron microscopic observations showed the formation of strong interaction between surface-treated CFs and polymer matrix. Dynamic mechanical thermal (DMTA) and thermoanalytical assessments were carried out. DMTA results indicated considerable improvements of storage modulus and viscose damping, in a wide range of temperature, by incorporating surface-treated CFs and CaCO3 nanoparticles. The glass transition temperatures of composites were noticeably greater than that of neat polymer because of the restriction effects of the fibers and nanoparticles on polymer chain mobility. Surface-treated CF and CaCO3 inclusions considerably elevated the heat of fusion and crystallinity. Results of thermogravimetric analyses indicated noticeable higher thermal stability against decomposition for composites as compared to the neat polymer. The adhesion of PA6/ABS polymer to surface-treated CFs and the presence of nanoparticles in polymer–fiber interphase were considered to be the key factors in determining the properties of composites. [ABSTRACT FROM AUTHOR]

CELLULOSE nanocrystals, LACTIC acid, THERMAL properties, BAGASSE, SUGARCANE, and X-ray photoelectron spectroscopy

Poly(lactic acid) (PLA) nanocomposites film reinforced with cellulose nanocrystals (CNCs) extracted from sugarcane bagasse fibre (SBF) was prepared by solvent casting method. The CNCs were obtained through alkaline treatment followed by sulphuric acid hydrolysis or phosphoric acid hydrolysis. The aim of this work was to evaluate the feasibility of utilizing phosphoric acid (mild acid) to extract CNC from the SBF. The properties of the CNC were investigated by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The thermal properties of the PLA/CNC nanocomposites were characterized using thermogravimetric analyser (TGA). TEM results demonstrated that the CNC having diameter of 5.5–6.2 nm and length of 235–300 nm. Results from XPS characterization have confirmed the existence of both sulphate group and phosphate group in the H2SO4-treated CNC (S-CNC) and H3PO4-treated CNC (P-CNC). FTIR results indicated that the presence of hydrogen bonding and chemical interaction between PLA and CNC. The thermal stability of PLA/P-CNC-10 is higher than that of PLA/S-CNC-10 nanocomposites attributed to the char formation of P-CNC in the PLA matrix. [ABSTRACT FROM AUTHOR]

JUTE fiber, POLYLACTIC acid, NATURAL fibers, TEXTILES, SCANNING electron microscopy, DIFFERENTIAL scanning calorimetry, and TENSILE tests

Jute woven fabrics in as-received and alkali-treated conditions were respectively combined with polylactic acid resin to fabricate completely biodegradable composites by compression molding in one step. Scanning electron microscopy and differential scanning calorimetry and tensile tests were conducted to estimate the surface morphology, thermal, and mechanical properties of jute fabrics and the composites manufactured. The formability of the composites was evaluated by a thermal-stamping experiment. The results demonstrate that alkali treatment removes the surface impurities of fabrics and refine the fiber structures, lifting the thermal property of composites. As for the mechanical properties, the strength of the fabrics and composites declines while the modulus increases after alkali treatment of fabrics. Although some defects occur, the thermal-stamping experiments confirm the possibility of shaping jute/polylactic acid composite into complicated geometries. And the formability of the composites is influenced by many factors including sample sizes, the holding time of temperature, layup sequence, and so on while the number of layer makes no obvious difference to it. [ABSTRACT FROM AUTHOR]

WETTING, PLANT fibers, LIGNINS, BAGASSE, STRENGTH of materials, and COMPOSITE materials

Chemical modification of fiber surfaces can increase wettability of composites reinforced by vegetal fibers and, consequently, the dispersion of the fiber in the matrix and mechanical properties can be improved. Although there are some studies about agents for chemical modifications of vegetal fiber surfaces, there are few data and discussion about the usage of lignin. In the present work, chemical modifications of sugarcane bagasse and sisal fibers using lignin (previously hydroxymethylated) were carried out under different reaction times (15, 30, and 60 min). The composition (holocellulose, hemicelluloses, cellulose, and lignin contents) of the treated and untreated fibers was evaluated. Phenolic composites were prepared using unmodified and modified fibers via compression molding process under temperature. Izod impact, water absorption tests, and scanning electron microscopy were performed to evaluate composite properties. The resin and lignin were characterized by size exclusion chromatography. Results showed that there was a tendency of reducing water absorption for composites prepared from modified fibers. Impact strengths of composites reinforced with sugarcane bagasse with modified fibers were similar to the ones with unmodified fibers (around 20 J/m). However, impact strengths for composites reinforced with modified sisal fibers (around 104 J/m for 15 min of reaction time) were higher than the ones with unmodified fibers (around 95 J/m). Therefore, the usage of lignin as a modifier agent of vegetal fiber surfaces to increase fiber–matrix adhesion for phenolic composites is a strategic alternative for improving products through simple, eco-friendly, and low-cost procedures. [ABSTRACT FROM AUTHOR]

The performance and durability of tribological components in roller follower valve train is governed mainly by the roller rotational behaviour. Pure rolling of roller on the camshaft surface is essential to achieve the optimum valve train efficiency. The increase in roller slip can lead to high valve train power loss due to increase in sliding friction and can increase the wear rate of mating surfaces of camshaft and roller. In this research work, a modern gasoline engine having end-pivoted roller finger follower valve train configuration has been instrumented to investigate the effects of Wonder Process Craft surface treatment on roller slip. Comprehensive test programme has been undertaken at transient camshaft speeds by employing the New European Drive Cycle under different oil temperatures and pressures. Remarkable reduction in roller slip was recorded for Wonder Process Craft surface treated roller as compared to the original unmodified roller indicating its strong potential of employment in engine valve train. The test rig, surface treatment of roller, instrumentation, experimentation, results and discussion have been presented in detail in this paper. [ABSTRACT FROM AUTHOR]

The state of the surface plays a crucial role in defining the mechanical properties of bonded joints, in particular, the chemical state of the adherend surface and its structural morphology have been proved to be the main elements of the bonding process. The structural morphology of the surface strictly depends from its topological features, like roughness, presence and distribution of grooves, homogeneity, etc. In a previous work, the effect provided by pulsed Yb-laser ablation on the mode I energy release rate of aluminium double cantilever beam joints was evaluated, in order to identify a relation between the combination of laser parameters and the morphological characteristics of the ablated surfaces which can support in identifying the optimal process configuration. The experimental tests showed that the fracture toughness of the double cantilever beam joints grew up as the surface roughness increased until a threshold value, after which the grooves resulted too narrow to allow the adhesive to completely fill them, inducing a higher amount of entrapped air into the grooves and therefore reducing the level of failure propagation energy. In this work, the problem dealing with the influence that the presence of air bubbles has over the mechanical behaviour of bonded joints was considered and the study went deeper into the investigation on the relation between laser-induced surface topology and mechanical response of joints. Different surface textures involving different directions and conditions of treatment were realized and their effect on the mechanical properties of aluminium bonded specimens was evaluated through experimental tests. The characterization of the treated surfaces was carried out by observing them with a 3D optical profiler and with SEM analysis and by measuring some geometrical features of the patterns created as a result of laser ablation. [ABSTRACT FROM AUTHOR]

Laser finishing tests were carried out using a 1000 W, CO2 continuous transverse-flow laser, with a defocusing value of 2 mm, and at different scanning speeds (200 mm/min, 400 mm/min, 600 mm/min, 800 mm/min, and 1000 mm/min). When the laser scanning speed was 600 mm/min, an Al-Si alloy cylinder liner gave the lowest friction coefficient and weight loss. Laser finishing could completely remove the aluminum layer and at the same time increase the silicon particles’ exposure with rounded edges. This microstructure improved the lubrication and bearing capacity, while it reduced adhesion and the friction force. Therefore, the friction coefficient and weight loss were lower with laser finishing than without. [ABSTRACT FROM AUTHOR]

EPOXY resins, COMPOSITE materials, X-ray diffraction, CARBON fibers, and MICROSTRUCTURE

This paper describes the results obtained when ultraviolet laser treatment was performed as a surface treatment prior to adhesive bonding for two aeronautical carbon fibre-reinforced plastics based on an epoxy resin prepreg. Different laser- processing parameters were employed, and their effect on the surfaces was analysed through morphological characterisation and wettability studies. X-ray photoelectron spectroscopy measurements were performed to determine the cleaning and activation effects of the treatment. The strength of the bonded joint was studied for laser-treated and manually ground samples. Samples processed under the selected laser conditions exhibited better adhesive behaviour than the manually treated samples, thereby suggesting that ultraviolet laser treatment could be used as an alternative method for surface activation of aeronautical composites based on epoxy resins. [ABSTRACT FROM AUTHOR]

LEAF fibers, PINEAPPLE, SURFACE preparation, THERMOPLASTIC composites, SILANE compounds, ISOCYANATES, and POLYPROPYLENE

Pineapple leaf fiber (PALF) was treated by silane and isocyanate treatments at 0–20% prior to being used as reinforcement in low-density polyethylene (LDPE) and polypropylene (PP) composites. The reactive groups of silane and isocyanate on PALF surface were confirmed by Fourier transform infrared spectroscopy. Scanning electron micrographs also showed the fiber surface coated with layers of treated chemicals as compared with the untreated one. These surface treatments reduced the water absorption of PALF. The physical properties of the PALF-reinforced composites were investigated. The resulting composites possessed higher tensile strength and lower crystallinity than the untreated composites. Silane treatment gave better PALF/LDPE composites in terms of composite strength as compared to isocyanate treatment. For treated PALF/PP composites, fiber pullout was reduced both silane and isocyanate treatments. [ABSTRACT FROM AUTHOR]

AMINES, SURFACE grafting (Polymer chemistry), CARBON fibers, POLYMERIZATION, FIBROUS composites, and MECHANICAL behavior of materials

Low-generation poly(amido amine) (PAMAM)-grafted carbon fibers (CFs) emerged as a new reinforcement for improving the mechanical properties of fiber composites. In this work, hybrid reinforcement, which could greatly enhance the surface roughness and wettability of CF, was prepared via growing PAMAM onto fiber surface by in situ polymerization.The modified surface morphology and chemical composition were investigated by scanning electron microscopy, atomic force microscopy, dynamic contact angle analysis test, and X-ray photoelectron spectroscopy. Experimental results indicated PAMAM dendrimers grown on the CF significantly enhanced interfacial properties of the resulting composites. In addition, compared with the desized CF composites, the CF grafted with PAMAM composites exhibited 34.65% enhancement in the interfacial shear strength. [ABSTRACT FROM AUTHOR]

SURFACE grafting (Polymer chemistry), METHACRYLATES, BIOMEDICAL materials, SURFACE preparation, and DIFFERENTIAL scanning calorimetry

Since octafluoropentyl methacrylate is an antifouling polymer, surface modification of polyether ether ketone with octafluoropentyl methacrylate is a practical approach to obtaining anti-biofilm biocompatible devices. In the current study, the surface treatment of polyether ether ketone by the use of ultraviolet irradiation, so as to graft (octafluoropentyl methacrylate) polymer chains, was initially implemented and then investigated. The Fourier-transform infrared and nuclear magnetic resonance spectra corroborated the appearance of new signals associated with the fluoroacrylate group. Thermogravimetric curves indicated enhanced asymmetry in the polymer structure due to the introduction of the said new groups. Measuring the peak area in differential scanning calorimetry experiments also showed additional bond formation. Static water contact angle measurements indicated a change in wettability to the more hydrophobic surface. The polyether ether ketone–octafluoropentyl methacrylate surface greatly reduced the protein adsorption. This efficient method can modulate and tune the surface properties of polyether ether ketone according to specific applications. [ABSTRACT FROM AUTHOR]

ANTIBACTERIAL agents, HYDROGELS, SUPERABSORBENT polymers, ION exchange (Chemistry), and CETYLTRIMETHYLAMMONIUM bromide

Superabsorbent polymer hydrogels with antibacterial activity were prepared by an ion exchange reaction as a feasible approach to induce high saline absorption without gel blockage. Hydroethanolic solutions of cetyltrimethylammonium bromide were used to modify surface particles of cross-linked sodium acrylate-co-acrylic acid copolymers which already synthesized under defined conditions. Fourier transform infrared spectroscopy was employed to study the structural characteristic of the finished products. The influence of cetyltrimethylammonium bromide on free (in water) and loaded (in saline) swelling capacity as well as antibacterial activity of superabsorbent polymer hydrogels against Staphylococcus aureus was investigated. Modified samples displayed an improved free and loaded swelling in water and saline, as well as no gel-blocking. These improvements were found to be affected by the reaction time, cetyltrimethylammonium bromide concentration, and water percentage in the solvent mixture. The results from energy dispersive X-ray analysis showed that cetyltrimethylammonium bromide was distributed uniformly in the superabsorbent polymer hydrogel particle surface. Moreover, the modified superabsorbent polymer hydrogels showed high antibacterial activity against S. aureus. Both bacteriostatic and bactericide effects were observed depending on the reaction conditions. Overall, several improvements were concurrently achieved via a single cost-effective post-treatment on the superabsorbent polymer hydrogel particles. Therefore, the results can effectively be used in designing larger scale production of antibacterial superabsorbent polymer hydrogels with desirable swelling properties in hygiene applications. [ABSTRACT FROM AUTHOR]

A study on new materials usage to produce fiber metal laminates is presented in this work. Amorphous polyvinyl chloride thermoplastic and aluminum 3550 sheets are used to fabricate the fiber metal laminates. Different surface treatments were carried out on the aluminum sheets and the fiber metal laminates were produced using the film stacking procedure. Flexural strength and modulus of the products and also shear strength of bonding were measured using three-point bending test, and their failure mechanisms were evaluated using optical microscope images. Also, the effects of aluminum layer and aluminum/composite laminates bonding on the dynamic properties of the fiber metal laminates were studied using Dynamic Mechanical Thermal Analysis. It was concluded that mechanical roughening of the aluminum sheet has the maximum effect on the aluminum/matrix bonding strength such that simultaneous fracture of composite laminates and aluminum layer in the bending condition was observed in the produced fiber metal laminates without any delamination. [ABSTRACT FROM AUTHOR]

MOLDING (Founding), PERMEABILITY, RAMIE, EPOXY resins, NATURAL fibers, and SURFACE preparation

Natural fiber has been a focus for environmental and recyclable polymer composite. Liquid composite molding process is an attractive manufacturing technique for natural fiber-reinforced polymer composites with high quality and low cost. Understanding the permeability along different directions of fiber preform is important for liquid composite molding to design and optimize mold and processing parameters. This paper addresses issues of the permeabilities along longitudinal direction of ramie fiber bundles and through-thickness direction of ramie fabric stack. Two simple methods were designed to detect axial and transverse infiltration with assistance of external vacuum pressure in ramie bundles and ramie fabric stack, respectively. Different surface chemical treatments, including flame retardant, silane and alkali treatments, were done on ramie fabric. The effects of fiber content, liquid type and surface treating method on the permeability and capillary pressure were studied. The results show that surface treatment obviously changes the surface morphology and surface energy of ramie fiber. The relationships between defined relative velocities of penetration flow and applied pressure for ramie fiber bundles and fabrics perfectly follow linear relationships, indicating that Darcy’s law is suitable for describing permeation behavior in ramie fibers. Moreover, fiber content and liquid type, including silicone oil and epoxy resin, significantly impact axial permeability and capillary pressure. Surface treatment significantly decreases the permeability along the thickness direction of ramie fabric stack followed by increasing capillary pressure, which are attributed to the changes of treated ramie fibers in surface energy and morphology. Finally, a unique difference in the permeabilities along axial and thickness directions was pointed out. [ABSTRACT FROM AUTHOR]