Influence of disbond on notch crack behaviour in single bonded lap joints

The behaviour of the adhesive bonded joints due to the imposed eccentric loading generates a very complex distribution of the stress in the structure. Good adhesion between substrate and adhesive ensures a successful and lasting assembly. In this study the finite element method is used to analyze the behaviour of a bonded lap joint of dissimilar materials. The effects of the mechanical properties of the joints on the shear stress variation with and without presence of a circular notch are investigated. The results show that the maximum shear stresses are located at a distance of about 18% that of the lap length whatever the type of material used. In addition, the stress intensity factor is amplified by the presence of the negative effect of disband whose increase is linearly proportional to the square of the stress intensity factor. It reached its maximum value for a crack length equal to two-fifths of the notch radius.     

Interaction effect crack–interfacial crack using finite element method

The interaction effect of an interfacial crack–microcrack modifies considerably the fracture behaviour of S45C/Si₃N₄ bimaterial. This work aims at studying the interaction effect of a crack located in one of the materials constituting the assembly near the interface, and that between an interfacial crack and a microcrack parallel to the interface by using the finite element method. The effect of transverse and longitudinal interaction distances between the interfacial crack and the microcrack are highlighted. The stress intensity factor of the interacting cracks and the bimaterial mechanical properties influence on the conditions of deviation and propagation of crack by interface and intercrack are examined.     

Gliding arc plasma assisted photocatalytic degradation of anthraquinonic acid green 25 in solution with TiO2

Anthraquinonic acid green 25 (AG 25) removal was investigated by plasmachemistry using non-thermal gliding arc at atmospheric pressure. The gaseous species formed in the discharge, and especially OH radicals, induce strong oxidizing effects in the target solution. The removal of the dye was carried out in the absence and presence of TiO₂ as photocatalyst. The decolourization of AG 25 was followed by UV–vis spectrometry (at 643 nm), while the degradation was followed by COD measurements. The effects of operating variables such as initial concentration of AG 25 and catalyst concentration were investigated. Experiments were carried out to optimise the amount of TiO₂. The results showed that maximum degradation was attained for 2 g L⁻¹ TiO₂ concentration. At this optimum concentration, the dye (80 μM) was totally decolourized within 15 min of plasma-treatment time, and 93% removal of initial COD was attained after a 180-min plasma-treatment time. In the absence of catalyst, colour removal was 46% after 15 min, while COD abatement reached 84% after 180 min. The extent of degradation decreased with initial concentration and the time required for complete degradation increased. In all cases, the plasma-treated samples in the presence or absence of catalyst were found to follow pseudo-first order reaction kinetics. The TiO₂-mediated plasmachemical process showed potential application for the treatment of dye solutions, resulting in the mineralization of the dye confirmed by sulfate ion formation.     

Preparation of Nano-TiO2/Diatomite Composites by Non-hydrolytic Sol–Gel Process and its Application in Photocatalytic Degradation of Crystal Violet

Silicon - The dispersion of anatase TiO2 on diatomic material was a prospective route to avoid agglomerates of these particles. In this work, the TiO2/diatomite composites were prepared using a...     

Removal of Supranol Yellow 4GL by adsorption onto Cr-intercalated montmorillonite

Cr(III)-intercalated montmorillonite was utilized as an adsorbent for the removal of the organic pollutant, Supranol Yellow 4GL, a synthetic dye used for chemical fibres. The material was prepared by the reaction of Na montmorillonite with a base-hydrolyzed solution of Cr nitrate salt (OH(-)/Cr(3+) molar ratios of 2). XRD data showed that the interlayer spacing (d(001)) of montmorillonite was increased from 12.35 to 23.06 Angstroms. The kinetics and mechanism of the adsorption of the acid dye, Supranol Yellow 4GL, on Cr(III)-intercalated montmorillonite was investigated. The equilibrium time was reached within 30 min. The process follows pseudo-second-order rate kinetics. The Langmuir isotherm described the adsorption data over the concentration range (20-160 mg/l). The separator factor R(L) revealed the favourable nature of this adsorption process. Also, the thermodynamic parameters such as DeltaS degrees, DeltaH degrees, DeltaG degrees were determined.     

Removal of mercury from natural gas by a new activated adsorbent from olive stones

This study was devoted to the valorization of a plant waste (olive stones): that is widely available in Mediterranean countries in order to remove mercury from natural gas. The raw material from olive stones was prepared by pyrolysis, chemical activation with phosphoric acid, and physical activation under steam. Two olive stone‐based granular activated carbons were prepared: one with the virgin stones, while the other was impregnated with sulphur. After treatment, the adsorbents obtained were characterized by determining the iodine number, the methylene blue index, and by estimating the porous properties by N₂ adsorption at 77 K. Thermogravimetric analysis and infrared spectroscopy analysis were carried out to determine the functional groups before and after mercury adsorption. An experimental study of vapour‐phase mercury adsorption by the activated carbons (virgin and sulphur‐impregnated) and a comparison with a commercial material (HGR) were performed. The comparison, made by analyzing the adsorption in a continuous mode, showed that the proportion of sulphur and the porosity were important for the removal of mercury. In the conditions used, the mercury adsorption on the ACs studied follows a physisorption mechanism. The results showed that granular activated carbon‐based olive stones (sulphur‐impregnated) are very efficient to remove mercury (with 2864 μg/g) and also less expensive than commercial activated carbon due to their local availability.     

Preparation, characterization and Methylene Blue adsorption of phosphoric acid activated carbons from globe artichoke leaves

Activated carbons were prepared by the pyrolysis of artichoke leaves impregnated with phosphoric acid at 500 °C for different impregnation ratios: 100, 200, 300 wt.%. Materials were characterized for their surface chemistry by elemental analysis, “Boehm titrations”, point of zero charge measurements, infrared spectroscopy, as well as for their porous and morphological structure by Scanning Electron Microscopy and nitrogen adsorption at 77 K. The impregnation ratio was found to govern the porous structure of the prepared activated carbons. Low impregnation ratios (~ 100 wt.%) led to essentially microporous and acidic activated carbons whereas high impregnation ratios (> 100 wt.%) gave essentially microporous-mesoporous carbons with specific surface areas as high as 2038 m²·g^− 1, pore volume as large as 2.47 cm³·g^− 1, and a slightly acidic surface. The prepared activated carbons were studied for their adsorption isotherms of Methylene Blue at pH = 3 and pH = 9. The supermicroporous structure of the material produced at 200 wt.% H₃PO₄ ratio was found to be appropriate for an efficient adsorption of this dye controlled by dispersive and electrostatic interactions depending on the amount of oxygen at the surface.     

Interaction effect of a main crack emanating from a semicircular notch and a microcrack

The study of morphology of fracture surfaces cannot only answer the whole of the problems arising from the damage of microcracking. This damage generates energy dissipation and a stress field redistribution which contributes to the dissipation of the energy stored in the structure, and favours the stable propagation of the main crack. In this work, the finite element method is used to analyze the interaction effect of a main crack emanating from semicircular notch and a microcrack in order to understand the different mechanisms induced by this interaction and in particular the effects of reduction and/or amplification of the stress field between the macro and the microcrack. Two cases were considered: transverse and longitudinal displacement of the microcrack compared to the main crack. This kind of approach makes it possible to predict the predominating fracture mode, either by coalescence, or by deflection in the direction of mode II.     

Progressive edge cracked aluminium plate repaired with adhesively bonded composite patch under full width disbond

In this study, the crack growth behaviour of an aluminium plate cracked at the tip and repaired with a bonded boron/epoxy composite patch in the case of full-width disbond was investigated. This effect is the imperfection which could result during the bonded patch of the repaired structure. Disbonds of various sizes and situated at different positions with respect to the crack tip as well as the effect of adhesive and patch thickness on repair performance were examined. An analysis procedure involving the efficient finite element modelling applied to cracked plate, adhesive and composite patch was used to compute the stress intensity factors. The crack growth rate is dominated by the stress intensity factor near the location and size of the pre-existing disbonds. The cracked plate and disbond propagation result in an increase in the patch deformation. The patch does not have an influence on the crack growth when the ratio 2a/d_R exceeds 0.8.     

Enhancement of the bleaching and degradation of textile wastewaters by Gliding arc discharge plasma in the presence of TiO2 catalyst

The degradation of two polluted textile wastewaters from SOITEX (silk and textile) industry using the plasma-catalytic process, has been studied by non-thermal Gliding arc technique coupled to Degussa P25 titanium dioxide (TiO(2)) as photo-catalyst. Experiments were carried out to optimise the amount of phtoto-catalyst. The results showed that maximum degradation was attained for 3 g L(-1) TiO(2) concentration. For wastewater (1) degradation was 95% at the end of 60 min of treatment time. The same wastewater was completely decolourised after only 30min of plasma-catalytic treatment time. In parallel, the biodegradability was significantly enhanced through 20 min of exposure to the plasmagenous source for both wastewater samples. Turbidity of wastewater (1) and wastewater (2) decreased with rate constants of 0.015 and 0.017m in(-1), respectively. The TiO(2)-mediated Gliding Arc discharge (GAD(TiO(2)) showed potential application for the treatment of liquid wastes, resulting in the mineralization of the wastewater samples confirmed by chloride, sulphate and phosphate ions formation. In both cases of GAD treatments, with and without photo-catalyst, the plasmagenous process proves efficient in the field of wastewaters degradation.