This study deals with the Rotary Friction Welding, (RFW) as a variation of friction welding in which the energy required to make the weld is supplied primarily by the stored rotational kinetic energy of the welding machine. The mechanical energy generated in overcoming friction is continuously transformed into heat. In most circumstances the thermal energy generated is regarded as undesirable, but under controlled conditions it can be used to join materials, as in the case of rotary friction welding. In this paper, similar and dissimilar joints of Acrylonitrile butadiene styrene (ABS) (chemical formula (C8H8)x· (C4H6)y· (C3H3N)z) and Polyethylene (PE) or polyethene or poly(methylene)) are studied. The effects of different rotational rates, plunge depths, and traverse speeds on the microstructure and tensile strength of joints were investigated. Some defects such as pores and cracks were found at inappropriate processing parameters. The tensile test was carried out as the mechanical properties of joints. Different significant parameters were discussed. The maximal and minimal tensile strength indicated and evaluated.

Fibre-reinforced polymer composite has many uses in structural components that required high strength, stiffness, and damping capacity. Cross and quasi-laminated epoxy composites with and without nano Al2O3 were used in this investigation to determine flexural modulus, natural frequency, damping ratio, and mode shapes by using analytical, experimental, and numerical (ANSYS) methods. It was demonstrated that adding 2 % nano Al2O3 improved the flexural modulus and the damping ratio while decreased the natural frequency. Cross number 2 and quasi number 2 had the highest natural frequency for cross and quasi laminate groups which are equal to 23.5 Hz and 20.25 Hz experimentally, respectively. On the other hand, the higher damping ratio was achieved for cross number 1 with nano Al2O3 and quasi number 2 with nano Al2O3 for both cross and quasi laminates, which are equal to 0.707 % and 0.693 %, respectively. The flexural modulus and damping ratio are inversely related to each other. However, the novelty in this article is that by adding two glass plies at the outer surface of quasi group laminate the flexural modulus, natural frequency, and damping ratio are increased simultaneously, as in the configurations quasi number 2 and quasi number 2 with nano Al2O3 in comparison with quasi number 1 and quasi number 1 with nano Al2O3.

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