# Influence of Welding Control Mode on the Joint Performance of Ultrasonically Welded Carbon Fiber-Reinforced Polycarbonate

## TL;DR

This study compares different welding control modes for ultrasonic welding of carbon fiber-reinforced polycarbonate and finds displacement control yields the best joint quality and stability.

## Contribution

The paper introduces a detailed comparison of welding control modes in ultrasonic welding of CFRTP with a focus on joint performance and process stability.

## Key findings

- Displacement control mode achieves the highest joint quality and process stability with a maximum lap-shear strength of 30.6 MPa.
- The displacement–energy relationship shows the strongest coupling with a Pearson correlation coefficient of 0.896.
- Significant differences in temperature field evolution and joint failure modes are observed across control modes.

## Abstract

Carbon fiber-reinforced thermoplastic (CFRTP) composites are now widely used in many fields. Ultrasonic welding (UW) is a key technology for joining these materials. The control mode of UW has a great effect on the quality of the welded joints. However, there is still not enough research comparing the different welding control modes. This paper investigates the effects of the time control, energy control, and displacement control modes on the ultrasonic welding quality of carbon fiber-reinforced polycarbonate (CF/PC). A flat PC film is used as the energy director (ED). The evaluation focuses on the lap-shear strength (LSS), macro- and micro-morphology, fracture surface characteristics and power–displacement curves of the welding process. Furthermore, significant differences are observed in the temperature field evolution and joint failure modes across the different control modes and process parameters. Results indicate that the displacement control mode achieves the highest joint quality and process stability, yielding a maximum LSS of 30.6 MPa. A correlation analysis reveals that the displacement–energy relationship exhibits the strongest coupling, and the Pearson correlation coefficient r is 0.896.