A process for making a fiber reinforced composite, comprising a) forming an impregnated multilayer fiber preform comprising i) a fiber mat that includes mass of fibers that have individual fiber diameters of at least 250 nm, ii) a nanofiber sheet applied to the fiber mat, wherein the nanofiber sheet: A) is composed of monofilaments having a diameter of at most 100 nanometers, an aspect ratio of at least 3 and being made of a material that does not melt or degrade under the conditions of step b); B) has a thickness of at most 1 mm and C) has a porosity of at least 30%; wherein the impregnated nanofiber sheet is coextensive with a major surface of the impregnated preform, and the monofilaments of the nanofiber sheet are oriented substantially parallel to said major surface; and iii) a resin composition that includes a liquid phase which impregnates the fiber mat and nanofiber sheet such that the impregnated multilayer preform has a porosity of at most 2 volume-%; and b) solidifying the liquid phase of the resin composition by cooling, curing or both cooling and curing the resin composition to form the fiber reinforced composite in which the impregnated nanofiber sheet is coextensive with a major surface of the fiber reinforced composite with the monofilaments of the nanofiber sheet being oriented substantially parallel to said major surface. a) forming an impregnated multilayer fiber preform comprising i) a fiber mat that includes mass of fibers that have individual fiber diameters of at least 250 nm, ii) a nanofiber sheet applied to the fiber mat, wherein the nanofiber sheet: A) is composed of monofilaments having a diameter of at most 100 nanometers, an aspect ratio of at least 3 and being made of a material that does not melt or degrade under the conditions of step b); B) has a thickness of at most 1 mm and C) has a porosity of at least 30%; wherein the impregnated nanofiber sheet is coextensive with a major surface of the impregnated preform, and the monofilaments of the nanofiber sheet are oriented substantially parallel to said major surface; and iii) a resin composition that includes a liquid phase which impregnates the fiber mat and nanofiber sheet such that the impregnated multilayer preform has a porosity of at most 2 volume-%; and i) a fiber mat that includes mass of fibers that have individual fiber diameters of at least 250 nm, ii) a nanofiber sheet applied to the fiber mat, wherein the nanofiber sheet: A) is composed of monofilaments having a diameter of at most 100 nanometers, an aspect ratio of at least 3 and being made of a material that does not melt or degrade under the conditions of step b); B) has a thickness of at most 1 mm and C) has a porosity of at least 30%; wherein the impregnated nanofiber sheet is coextensive with a major surface of the impregnated preform, and the monofilaments of the nanofiber sheet are oriented substantially parallel to said major surface; and iii) a resin composition that includes a liquid phase which impregnates the fiber mat and nanofiber sheet such that the impregnated multilayer preform has a porosity of at most 2 volume-%; and b) solidifying the liquid phase of the resin composition by cooling, curing or both cooling and curing the resin composition to form the fiber reinforced composite in which the impregnated nanofiber sheet is coextensive with a major surface of the fiber reinforced composite with the monofilaments of the nanofiber sheet being oriented substantially parallel to said major surface.