Bikramjit Sharma

A review of tool wear prediction during friction stir welding of aluminium matrix composite

Abstract Friction stir welding is the preferred joining method for aluminium matrix composites. It is a solid-state process which prevents the formation of the intermetallic precipitates responsible for degradation of mechanical properties in fusion welds of these composites. The major concern in friction stir welding is the wear of the welding tool pin. The wear is due to the prolonged contact between the tool and the harder reinforcements in the composite materials. This paper provides an overview of the effects of different parameters of friction stir welding on the tool wear. It was found that the total amount of material removed from the tool is in direct proportion to the rotational speed of the tool and the length of the weld but inversely proportional to the transverse rate. The results even demonstrate that the tool geometry also has significant influence on the wear resistance of the tool. The tool even converts itself into a self-optimized shape to minimize its wear.

Effect of surface treatment of nanoclay on the mechanical properties of epoxy/glass fiber/clay nanocomposites

Abstract A new method of silane treatment of nanoclays is reported where in the clay is nanodispersed in hydrolyzed silanes. The surface functionalization of Cloisite® 15A nanoclay has been carried out using two different silane coupling agents: 3-aminopropyltriethoxy silane and 3-glycidyloxypropyltrimethoxy silane using varied amounts of silane coupling agents, e.g. 10, 50, 200, and 400 wt% of clay. The surface modification of Cloisite® 15A has been confirmed by Fourier transform infrared spectroscopy. The modified clays were then dispersed in epoxy resin, and glass fiber-reinforced epoxy clay laminates were manufactured using vacuum bagging technique. The fiber-reinforced epoxy clay nanocomposites containing silane modified clays have been characterized using small angle X-ray scattering, transmission electron spectroscopy and differential scanning calorimetry. The results indicate that the silane treatment of nanoclay aided the exfoliation of nanoclay and also led to an increase in mechanical properties. The optimized amount of silane coupling agents was 200 wt%. The nanocomposites containing clay modified in 200 wt% of silanes exhibited an exfoliated morphology, improved tensile strength, flexural modulus, and flexural strength. The improved interfacial bonding between silane modified nanoclays and epoxy matrix was also evident from significant increase in elongation at break.

Effect of mixing parameters, postcuring, and stoichiometry on mechanical properties of fiber reinforced epoxy–clay nanocomposites:

The influence of processing variables was experimentally studied for glass fiber reinforced epoxy–clay nanocomposites manufactured using vacuum-assisted wet layup method. The tensile strength, flexural strength, and interlaminar shear strength of these nanocomposites were significantly influenced by the processing variables including the temperature of resin–clay mixture, speed of homogenization, and ultrasonic probe amplitude during premixing of clay minerals in epoxy. The glass transition temperature of glass fiber reinforced composites increased with incorporation of clay minerals in epoxy. Also, the postcuring of the laminates was carried out at three different temperatures, e.g. 100, 130, and 150 ℃ for 3 h. A decrease in tensile modulus, tensile strength, and flexural strength of nanocomposites postcured at 130 and 150 ℃ was observed. Also, the use of non-stoichiometric epoxy resin and hardener ratios had an adverse effect on mechanical properties of fiber reinforced epoxy–clay nanocomposites. In fiber reinforced composites incorporating clay minerals, a uniform dispersion of clay minerals besides a strong interfacial adhesion between clay minerals and polymer and optimum conditions of curing of matrix is a crucial aspect for improved performance over conventional fiber reinforced composites.