Effects of rotational speed on the microstructure and mechanical properties of continuous drive friction welding of dissimilar composite polymer rods

Additive manufacturing is a common method for producing diverse functional components. However, its application is constrained by the size limitations imposed by additive manufacturing machines. To address this limitation, continuous drive friction welding emerges as a potential solution to join parts of composite materials together. In this investigation, two welding specimens, composed of polylactic acid (PLA) with copper powder and PLA with aluminum powder, were welded using a turning machine. The assessment of fatigue behaviors in welded joints holds substantial importance in engineering applications. In general, the rotational speed in continuous drive friction welding is fixed. However, there is a lack of research focusing on the fatigue behavior of dissimilar polymer rods filled with metal powder using continuous drive friction welding with different rotational speeds. In addition to fatigue testing, a comprehensive evaluation was performed, including bending tests, surface hardness tests, and material studies such as optical microscopy and differential scanning calorimetry analysis. It was found that the highest temperature in the weld interface are about 150 °C, 136 °C, 108 °C, 96 °C, and 83 °C for rotational speed 1350, 950, 650, 490, and 330 rpm, respectively. The fatigue life of the dissimilar welded parts can be enhanced by approximately 16–30% using enhancing the rotational speed. The bending strength of the dissimilar welded parts can be enhanced by approximately 19–70% using enhancing the rotational speed. The surface hardness in the weld interface can be enhanced by approximately 1–2.5% using enhancing the rotational speed. The weld maintained superior mechanical properties at a rotational speed of 1350 rpm. The findings highlight significant potential applications in the welding industry.