Comparative analysis on the adhesion of carbon-fiber-reinforced thermoplastic composite/aluminum joints after dielectric barrier discharge and localized low-pressure plasma discharge treatments

Abstract

Joining dissimilar materials has become increasingly important as lightweight and recyclable materials like carbon fiber reinforced thermoplastic polymer (CFRTP) are being applied in the aerospace and automotive industries. Although adhesion with plasma treatment is highly effective, conventional plasma systems have key limitations, such as modest adhesion improvements, long process durations, and limited applicability to large-scale components. A novel plasma device, the localized low-pressure plasma discharge (LLPD), was designed to overcome these issues. The LLPD enables faster plasma treatment than atmospheric-pressure plasma and significantly reduces overall process duration, including evacuation time, while still achieving adhesion strength comparable to the highest value reported. This notable advancement is driven by the rapid and predominant formation of C–O functional groups over other oxygen functional groups, which directly promote epoxy ring-opening reactions and are crucial for substantial adhesion enhancement. The superior formation of C–O groups in LLPD, compared with other plasma devices, was clearly demonstrated through optical analysis of the plasmas. Building on these findings, LLPD is a promising candidate for the aerospace and automotive industries, as it offers greater industrial compatibility and higher throughput than other existing plasma treatments, providing a solution for large-scale structures that remain unattainable with conventional plasma devices. © 2026 The Authors.