چكيده به لاتين
Polymer matrix composites include two categories of thermoplastic and thermoset composites. Thermoplastic composites, due to their superior features such as higher impact resistance, higher damage tolerance, ability to melt and reprocess, have led to the creation of new unique manufacturing and joining methods, which are much faster compared to thermoset composite manufacturing methods and will increase productivity. Continuous ultrasonic welding of thermoplastic composites, which was the main subject of this research, as a new joining method, has features such as high speed and strength, automation capability and in-situ monitoring of the process. In this research, with the aim of experimentally studying the process of continuous ultrasonic welding of thermoplastic composites, first, the creation of a continuous ultrasonic welding machine for composite materials was conducted; Then, by making polyamide 6 reinforced with continuous glass fibers composite, the composite samples were ready for welding; In the following, considering the three main parameters of welding power, speed and pressure as input parameters and welding shear strength as output parameter, continuous ultrasonic welding tests were planned based on the central composite design using the response surface method. After the welding tests, based on the existing standards, the lap shear strength test was performed on the welded samples and the appropriate mathematical model was obtained to predict the shear strength of the continuous ultrasonic weld joint. Finally, in order to investigation the welding quality and justify the behaviors observed in the continuous ultrasonic welding process of composite materials, a microscopic examination of the connection fracture surfaces and the overlapping cross-section of the composite plates was carried out using optical and scanning electron microscopes. Based on the results of analysis of variance in Design Expert software, power-pressure interaction had the greatest effect on the shear strength of continuous ultrasonic welding, and pressure factor and power-speed interaction were found to be ineffective. The presence of a large percentage of fibers and the observation of the failure mechanisms of the fibers at the fracture surface of the joints indicate the creation of a weld with penetration, uniformity and high strength.
