Nanoparticle integration in adhesive and hybrid single lap joints: effect on strength and fatigue life under environmental aging

Examining the mechanical performance of CFRP and aluminum samples subjected to environmental aging is crucial. Additionally, it is essential to develop methods to enhance their mechanical properties. This research investigates the impact of fullerene and single-walled carbon nanotubes (SWCNT) on the fatigue life and static strength of bonded and bonded/bolted joints. The study focuses on composite-to-composite (CTC) and composite-to-aluminum (CTA) substrates under three-point bending, both before and after hygrothermal aging. The samples were divided into four categories: (1) neat specimens, (2) specimens with added fullerene, (3) specimens with added SWCNT, and (4) specimens with a combination of 50% SWCNT and 50% fullerene. The experimental results indicated that the optimal nanoparticle ratio for bonded joints differs from that for bonded/bolted joints. Adding nanoparticles to the adhesive increased the fatigue life of SLJs, particularly in samples containing mixed particles and SWCNT. In some cases, nanoparticles amplified the effect of hygrothermal conditions, enhancing fatigue life further. The integration of nanoparticles into the adhesive and the use of bonded/bolted joints significantly improved joint strength, with the combination of both techniques yielding the best results. These modified joints offer a promising alternative to traditional joints in terms of strength and fatigue life. The study enhances understanding of the aging of adhesive and hybrid joints, especially dissimilar joints (composite to metal), and provides insights into their behavior under various environmental aging conditions. These methods show potential for optimizing joints and composite structures, improving durability, and reducing the likelihood of operational failures.