A curable resin composition containing a blend of multifunctional benzoxazines, and composite materials derived therefrom. The benzoxazine blend contains the combination of (A) a difunctional benzoxazine component and (B) a multifunctional benzoxazine component with functionality of greater than 2. Cured matrix resins and cured composite materials containing such benzoxazine blend exhibit a significant retardation in the rate of organic solvent uptake as compared to the same cured matrix resins and composite materials without component (B).