Search

In this study, the friction stir extrusion process as a new method was used to produce AA 1050 aluminum composite wires reinforced with silicon carbide (SiC) powder. The effect of process parameters on temperature (T), porosity (P) and ultimate tensile strength (UTS) was evaluated using the response surface method based on the Box-Behnken design. The input parameters included rotational speed (RS), extrusion force (EF) and reinforcement weight percentage (RF). Moreover, the microstructural evaluation of composite samples was conducted using optical microscope and scanning electron microscope. Finally, analysis of variance and regression analysis were used to obtain an appropriate model and confirm the accuracy of the results. The results showed that the temperature was increased by increasing the rotational speed to 1000 r/min and decreasing the extrusion force to 5.5 kN. Moreover, the lowest porosity value (averaged = 0.5%), and the highest tensile strength value (averaged = 153 MPa) were obtained at RS = 750 r/min, EF = 10.5 kN and RF = 3%. This can be attributed to the uniform distribution of reinforcing particles and strong interfacial bonding between SiC particles and the aluminum matrix. Also, the most effective parameter in the process was rotational speed which exhibited the greatest influence on P (53%) and UTS (41%) of composite samples. However, reinforcement weight percentage had the least effect on P (14%) and UTS (28%). [ABSTRACT FROM AUTHOR]

Cellulosic materials were extracted from different agricultural wastes such as corn stalks, olive solid waste, and wood, by using a suitable extraction method. The extracted cellulosic materials were characterized using Fourier transform infrared spectroscopy. The produced cellulosic materials were used as reinforcements for low-density polyethylene to improve its tensile and thermal properties. A two-roll mill was used to mix the cellulosic materials (2.5–10 wt.%) with low-density polyethylene , and then the composite sheets were prepared by using a thermal press molding. The effects of filler type and its content on the mechanical and thermal properties were investigated by using the universal testing machine and differential scanning calorimeter, respectively. In general, with the increase of cellulosic materials content, there is an increase in the modulus of elasticity of the produced composites and a decrease of ductility. The ultimate tensile strength of the produced composites based on low-density polyethylene and cellulosic materials extracted from corn stalks and olive solid waste was found to be less than the tensile strength of low-density polyethylene, whereas the ultimate tensile strength of the composites based on low-density polyethylene and cellulose powder extracted from wood increased with increasing the cellulosic content. The addition of cellulosic materials was found to affect both the melting temperature of low-density polyethylene and its degree of crystallinity, depending on the cellulosic material source. [ABSTRACT FROM AUTHOR]

This study gives a detailed analysis on estimating the ultimate tensile strength of unidirectional fiber reinforced composites and its creep behavior under sustained tension load. We develop two different micromechanical models that allow us to estimate the longitudinal tensile strength and the evolution with time of fiber and matrix stresses around arbitrary array of fiber breaks. The first model is based on the shear-lag theory while the second one is developed using the software Abaqus. The comparison of the above models allowed to validate the fundamental assumptions of the shear-lag theory (first model) as well as several numerical issues related to time integration and spatial discretization. The Monte–Carlo method was used in order to account for the stochastic fiber strength and its impact on the ultimate tensile strength (short-term) and creep (long-term behavior) of unidirectional composites. Finally, a parametric investigation on the fiber type and the load level on the long-term behavior of unidirectional composites was performed showing an accelerating creep effect for fibers of inferior quality such as glass fibers compared to carbon fibers. [ABSTRACT FROM AUTHOR]

Nickel particulate-reinforced aluminum-silicon composites, with 5, 12.5 and 20 wt%Nickel were produced by a hot pressing route. Microstructural characterization showed a uniform distribution of the Nickel particulates in the aluminum-silicon matrix. Ultimate tensile strength and hardness of the composites were found higher than for the aluminum-silicon alloy, while ductility suffered a decrease. Fracture surface analysis showed evidences of load transfer from the matrix to the reinforcement indicating the development of an effective interfacial bonding between Nickel particulates and aluminum-silicon matrix. Energy dispersive spectrometer and X-ray diffraction analyses performed in the particle/matrix interface revealed that it was formed by Al3Ni intermetallic. It was found that the amount of Al3Ni intermetallic has a paramount influence in the composites properties. [ABSTRACT FROM AUTHOR]