Abstract: BIS (4-maleimidodiphenyl) methane (BMI) offer outstanding thermal/ hygrothermal machanical properties. But due to a high backbone aromatic content and crosslinking density after curing, BMI appear brittle nauture. Considerable formulation work has been carried out to improve fracture toughness and processability while retaining high temperature properties. Only this way BMI can be used as an matrix of advanced composites.QY8911 is a kind of modified BMI. It can be dissolved in common organic solvents and can be cured with traditional condition and has excellent thermo-mechanical property.For evaluating the toughness of QY8911, eight items have been carried out. They are compressive strength after impact, impact property on pre-compression stress, Charpy impact, impact/damage evaluation, interlaminar fracture toughness, criterion of edge de-lamination, tension strength with open hole and compression strength with open hole etc.The results from testing show that QY8911 has good toughness.Its toughness is nearly equal to that of narmeo 5250-2. Most of testing is conducted in U. S. A., so there are common base of comparing with each other.

Key words: bismaleimide, QY8911 BMI resin system, impact toughness