New glass fiber/bismaleimide composites with significantly improved flame retardancy, higher mechanical strength and lower dielectric loss

•Flame retarding glass fiber (GF) composites with new resin (BDDP) were prepared.•BDDP resin is composed of phosphorous flame retardant (DDP) and bismaleimide.•GF/BDDP composite with a small loading of DDP reaches excellent flame retardancy.•GF/BDDP composites also have higher mechanical strength and lower dielectric loss.•The origin behind attractive properties of GF/BDDP composites was studied.