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

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 degrees C while maintaining the shear strength of 10.8 MPa at 316 degrees 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 degrees 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.

Automated summary

In this study, a high-temperature resistant BMI structural film adhesive was successfully prepared with excellent heat resistance and bonding performance. The addition of VTBN and PPENK synergistically improved the toughness of the adhesive film. The co-cured composite joint exhibited good shear strength and peel strength.