Polyimide resins that are suitable for processing by resin transfer molding (RTM) and resin infusion (RI) methods at reduced processing temperatures are provided. The inventive RTM and RI processable polyimide resins exhibit melting at temperatures of less than about 200.degree. C. and melt viscosities at 200.degree. C. of less than about 3000 centipoise. A process for synthesizing the inventive resins is also provided, as is a fiber-reinforced composite material. The fiber-reinforced composite material employs the inventive polyimide resin as its resin matrix and demonstrates good heat resistance and mechanical properties.