Study on the adaptability of aluminum alloy and CFRP adhesive joints after extreme environments

Abstract

Adhesive joints are increasingly utilized in the aeronautical industry due to their advantageous properties. However, the durability of these joints remains a major concern in the context of aircraft, particularly due to the inherent characteristics of the polymeric materials involved. In this work, the effects of thermal aging on the adhesively bonded joints with both similar (Al/Al and CFRP/CFRP) and dissimilar (CFRP/Al) adherends were experimentally examined by double cantilever beam (DCB) tests. In order to estimate their long-term performance, the aging process was performed on adhesively bonded joints at different temperatures (−55 °C, 50 °C, and 90 °C) with variable exposure periods (7, 14, and 21 days). The load–displacement response, failure modes, and fracture toughness of the three types of joints studied have been introduced and compared. The results indicated that adhesives and bonded joints are influenced not only by extreme environments but also by the aging duration. Notably, the maximum load-carrying capacity and fracture toughness of bonded joints exhibited a non-monotonic change after thermal aging. Furthermore, bonded joints displayed different failure modes, which can be attributed to the varying degrees of impact on the adhesive, bonding interface, and adherends by the aging environment. Among the tested configurations, CFRP/CFRP joints demonstrated the highest adaptability to extreme environments, followed by Al/Al joints, while CFRP/Al joints showed the lowest adaptability. These findings may provide some insights into the thermal effects on the residual properties of the adhesive joints for aircraft applications.