The preparation and performance of non-woven carbon tissue reinforced adhesive film for bonding CFRP-aluminum

This study developed a kind of non-woven carbon tissue reinforced adhesive film (NWCTRAF) with high bonding strength and reliability by interleaving the NWCT into the adhesive film. The manufacturing process, bonding strength, Weibull distribution, metallography of cross-section, and fracture surface morphology of NWCTRAF specimens were investigated. The results showed that the average bonding strength and Weibull characteristic strength (WCS) of single lap joint (SLJ) were 27.4a and 28.2 MPa, which increased by 17.6% and 15.1%, respectively compared with the blank specimen, and the Weibull modulus risen from 9.51 to 18.72, which indicated that NWCTRAF specimens had higher bonding reliability. The mechanism of micro-crack formation was obtained by analyzing the cross-section of loading 95% WCS without visible damage. The metallographic section showed that the microcracks of the blank specimen originated from the interface between carbon fiber-reinforced polymer (CFRP) and adhesive layer, while the microcracks of the NWCTRAF specimen originated from the resin-rich regions between the carbon fiber fabric layers in CFRP. Typical failure modes were gained from optical microscope and SEM. Failure modes of blank specimen included more interface failure of CFRP-adhesive and Al-adhesive, while NWCTRAF specimen had more carbon fiber tearing and delamination of CFRP. The fracture morphology of adhesively cohesive failure included the pull-out of short carbon fibers and the appearance of rough and multi-stage resin in the NWCTRAF specimen, which improved the toughness of the adhesive layer. The bridging effect of short carbon fibers in the NWCTRAF disperse and transfer stress to CFRP and fail at resin-rich regions of CFRP, decrease the bonding interface's direct failure, and improve the bonding strength and reliability.