Estimating and optimizing the flexural strength of bonding welded polypropylene sheets by friction-stir welding method

In recent years, the growing trend of using polymer materials in various industries has led to significant improvements in the methods of production and bonding of polymer materials. The present study aimed to optimize the flexural strength of polypropylene sheets welded by the friction-stir method, which is considered as one of the most efficient methods in this field. The surface quality and mechanical properties of the components produced in this method highly rely on the parameters of rotational speed, linear speed, geometry, and tool tilt. Therefore, this research seeks to evaluate the effect of these parameters on three different levels, both experimentally and statistically, in order to investigate the welding flexural strength. By applying the analysis of variance and Box–Behnken response surface methodology, the results revealed the existence of a significant relationship between the properties and parameters of the process and the possibility to examine the effect of the interaction of different parameters in the process using mathematical modeling and Chart analysis. In addition, optimal models were introduced through process optimization so that the flexural strength of the weld joint was increased by up to 96% of that of the base specimen, after conducting further experimental tests, resulting in confirming the optimal model. Finally, the efficiency of the designed model was evaluated by comparing the measurement errors obtained from the experimental results and the prediction of the model.