Toughening of BMI Based Graphite Laminates by Ex-situ Concept

High-performance bismaleimdes （BMI） matrix composites reinforced by graphite fibers were prepared and toughened with a thermoplastic component （PAEK） by using the Ex-situ concept. Experimental matrix was designed for overall toughening of the base resin, periodically interleaving thermoplastic films into each plies （E：c-situ concept） and for varying the film compositions. The highest impact damage resistance characterized by compression after impact （CAI） was obtained for the laminates toughened on the E：c-situ concept, especially, when two-component cast films of a special ration of PAEK/BMI 60 ： 40 were interleaved though the thermoplastic concentration for the overall toughening, interleaving the pure thermoplastic films and the two-component films was comparable. There were two peaks found in the DSC trace of the laminates toughened implying a phase separation process occurred. The glass transition temperature of the laminates toughened was slightly reduced due to the low-temperature PAEK. Morphological study revealed a typical granular structure just in the interplay region as a result of spinodal decomposition and coarsening process. This was in agreement of the result of DSC investigation.