High temperature and toughened bismaleimide structural film adhesive for high performance CFRP bonding over 300 °C

Abstract

Structural adhesive play an important role in the manufacturing of composite structures. Here, a high-temperature resistant bismaleimide (BMI) structural film adhesive was prepared by using a chemically modified BMI resin as the matrix with poly(phthalazinone ether nitrile ketone) (PPENK) as the film-forming agent. The toughness of the adhesive was greatly enhanced by adding vinyl-terminated butadiene acrylonitrile (VTBN). The performance of the high-temperature resistant BMI structural film adhesive was optimized with 15 phr of PPENK and 6 phr of VTBN, which exhibits outstanding heat resistance, excellent bonding and peeling performance. Its glass transition temperature is as high as 272 °C while maintaining the shear strength of 10.8 MPa at 316 °C. The synergistic toughening effects of VTBN and PPENK significantly improve the toughness with a high peel strength of 41.7 N mm/mm. The co-cured composite joint formed between BMI prepregs and modified BMI adhesive exhibits shear strength of 10.7 MPa at 316 °C and peel strength of 21.8 N mm/mm, indicating an effective bonding between the modified BMI adhesive and BMI prepreg. The phase at the bonding interface is proved to be an important factor for high-performance at the bonding joint.