Impact of coating and curing temperature on the formation of CFRP/sealant gradient interphase

Flexible sealant joints are extensively utilized for sealing aircraft wing fuel tanks due to the excellent stress transfer release of gradient interphase. This study investigates the impact of coating and curing temperature on the formation of CFRP/sealant gradient interphase. The interphase quality was identified using SEM equipped with EDS, and a detailed analysis of element concentration transition was performed to understand the interplay between different mechanisms. Contact angle calculation and FTIR-XPS combined spectral analysis were conducted to determine the interfacial physicochemical state. The results showed that coating enhances compatibility and broadens interphase, whereas opposite results were observed at higher temperatures. The improvement of surface energy and wettability, chemical groups, and molecular bonding sites provided by coating promotes interfacial reactivity and molecular mobility. Elevated cure temperature accelerates the formation of cross-linked networks that restricts sealant chain mobility, indicating that vulcanization dominates over diffusion under high cure temperature.