Fracture behavior of high-performance carbon fiber composites toughened by reactive polyetherimide

Carbon fiber-reinforced epoxy composites (CFECs) continue to grow in demand for aerospace, mass transportation, electric vehicle, and energy efficient architecture due to their lightweight, high strength, and high modulus. However, CFECs are susceptible to delamination upon impact which can lead to premature structural failure. This paper investigates the interlaminar fracture toughness of unidirectional CFECs based on reactive polyetherimide (rPEI) modified multifunctional epoxy matrix system. The matrices were cured formulations of tetraglycidyl diamino diphenyl methane, triglycidyl para-amino phenol, rPEI having different molecular weights (MW) and diaminodiphenyl sulfone. Multi-phase morphologies were observed from the resin castings and CFECs containing different MW rPEI modifiers. Results show that the mode I fracture toughness (G(IC)) of the rPEI-toughened CFECs can be increased by as much as 150% over the unmodified CFECs based on the MW and type of phase morphology that promotes crack-bridging mechanism. In addition, rPEI-modified CFECs exhibit better property retention (similar to 80% of G(IC)) after prolonged solvent exposure.