Papers by Author: Nesar Merah

Abstract: The mechanical and physical properties of epoxy-clay nanocomposites are known to be significantly affected by the dispersion and distribution of the clay particles in the epoxy matrix. The degree of dispersion of the clay particles in the epoxy matrix depends mainly on the processing parameters used to synthesize the nanocomposite.In this paper, the optimized high shear mixing parameters determined in an earlier work were used to disperse five different loadings of Nanomer I.30E nanoclay (1, 1.5, 2, 3 and 5 wt%) into DGEBA epoxy matrix. A systematic approach was adopted to optimize the degassing process of the mixture. X-Ray Diffraction (XRD) analyses showed that the optimum nanoclay dispersion was achieved for a degassing temperature of 120 °C. The flexural strength of the developed nanoclay/epoxy composite is found to increase by 15% for 1.5 wt% and due to the high stiffness of the clay, as compared with epoxy resin, the flexural modulus improved continuously with clay loading. The observed reduction in strength and fracture strain at high clay loadings is mainly attributable to the presence of clay agglomerations and voids formation. The diffusion of water molecules and maximum moisture uptake of epoxy are reduced considerably by the presence of nanoclay.

Abstract: Addition of organoclay to polymer matrix has recently attracted industry attention due to improved physical properties with an overwhelming potential in crude oil and water pipe applications. In this work, electrical grade-corrosion resistant (E-CR) glass fiber mats were used to prepare glass fiber reinforced epoxy (GFRE) nanoclay composites using hand layup method. Three different hybrid GFRE composites were made using 0, 1.5 and 3 wt% loading of I.30E nanoclay. High shear mixing was used to prepare the epoxy/clay nanocomposite. XRD results revealed a disordered intercalated morphology. The effect of nanoclay on mechanical properties were investigated by carrying out flexural and fracture toughness tests. The test results showed that addition of nanoclay up to 1.5 wt% improved both flexural strength and fracture toughness. However, these properties deteriorated when the clay content increased to 3 wt%.

Abstract: The technique of adhesively bonded composite patch repair has been successfully applied in pipeline of API X65 components repair and has recently been expanded to commercial pipeline industry. In the present paper, the crack growth behavior of cracked pipeline API X65 repaired with bonded composite patch was investigated. The finite element approach was applied in order to analyses the circumferential crack’s behavior repaired by a carbon-epoxy composite patch. The effects of the properties of the patch on the evolution of the stress intensity factor, according of angle crack tip, were discussed. The adhesive properties were optimized to increase the performance of the repair of structures by such reinforcement. Moreover, a relatively new method was developed to stop the external corrosion and the structurally reinforce steel pipes by external wrapping of damaged sections, using fibre reinforced polymer (FRP) materials. The results indicated that the defect width around the circumference had little impact on the ultimate rupture pressure of the repaired vessel. On the other hand, it was found that the defect width around the circumference was affected by the stress state in the underlying pipe substrate.

Abstract: Epoxy-clay nanocomposites were prepared by high shear mixing method using Nanomer I.30E nanoclay as nano-reinforcement in diglycidyl ether of bisphenol A (DGEBA). The effect of mixing speed and time on the nature and degree of clay dispersion were investigated by varying the mixing speed in the range of 500-8000 RPM and mixing time in the range of 15-90 minutes. The effect of degassing temperature on the morphology of the resultant nanocomposites was also studied. Scanning and transmission microscopy (SEM & TEM) along with x-ray diffraction (XRD) have been used to characterize the effect of shear mixing speed, mixing time and degassing temperature on the structure of the resultant nanocomposites. The SEM, TEM and XRD examinations demonstrated that the degree of clay dispersion was improved with increasing the high shear mixing speed and mixing time. The results showed that the optimum high shear mixing speed and mixing time were 6000 rpm and 60 min, respectively. It was observed that the structure of the nanocomposites that have been degassed at 65oC was dominated by ordered intercalated morphology while disordered intercalated with some exfoliated morphology was found for the sample degassed at 100oC for the first 2 hours of the degassing process.

Abstract: Proper dispersion of nano thin layered structure of nanoclay in polymer matrix offers new and greatly improved properties over pristine polymers. The degree of nanoclay dispersion and hence the improvements in the physical and mechanical properties depend greatly on the technique used and processing parameters. In this work, 2 wt.% epoxy-clay nanocomposites were fabricated using different mixing techniques to study the effect of mixing methods on the nanoclay dispersion and thus on the enhancement of the properties of the resultant nanocomposites. Three mixing techniques were explored: high shear mixing (HSM), ultrasonication and their combination as well as hand mixing. The effect of mixing techniques on morphology and mechanical properties of the resultant nanocomposites was investigated using scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscope (TEM) and tensile testing. The results of XRD and TEM showed that both exfoliated and disordered intercalated morphology were developed for the nanocomposites synthesized by HSM, while ordered intercalated morphology was observed for samples prepared by sonication. The tensile test results show that among the mixing techniques considered in this study HSM results in the optimum mechanical properties as a whole while hand mixing resulted in the worst physical and mechanical properties.