Multilayer radar-absorbing laminate for aircraft made of polymer matrix composite material with graphene nanoplatelets, and method of manufacturing same

A multilayer radar-absorbing laminate made of composite material with polymeric matrix containing graphene nanoplatelets for use on an aircraft, wherein the multilayer radar-absorbing laminate comprises a plurality of juxtaposed blocks, the plurality of juxtaposed blocks including:

• a first electrically conductive block to be placed in use toward the inside of the aircraft, having an electromagnetic radiation reflection coefficient greater than −1 dB;
• a second intermediate electromagnetic absorber block, comprising a stack of electrically non-conductive dry fiber sheets, wherein each electrically non-conductive dry fiber sheet is at least partially permeated with the graphene nanoplatelets, to achieve a periodic and electromagnetically subresonant layer in which conductive layers containing the graphene nanoplatelets alternate with non-conductive layers;
• a third block of electrically non-conductive material to be arranged toward the outside of the aircraft in use and forming part of an outer surface of the aircraft;
• wherein the second intermediate electromagnetic absorber block is obtainable by a process comprising the steps of:
• a) providing the graphene nanoplatelets with a thickness between 2 nm and 100 nm and lateral dimensions between 100 nm and 10 microns;
• b) dispersing the graphene nanoplatelets in a polymeric mixture consisting of a solvent and a polymer, to obtain a suspension of the graphene nanoplatelets in the polymeric mixture;
• c) depositing by air spraying the suspension of the graphene nanoplatelets on one or both opposite sides of the electrically non-conductive dry fiber sheets, with controlled penetration of the graphene nanoplatelets into the respective electrically non-conductive dry fiber sheets;
• and
• d) forming the second intermediate electromagnetic absorber block by overlapping a plurality of electrically non-conductive dry fiber sheets sprayed with the suspension of the graphene nanoplatelets;
• and
• wherein forming the second intermediate electromagnetic absorber block is followed by the steps of:
• e) executing a lay-up including the first electrically conductive block, the second intermediate electromagnetic absorber block, and the third block of electrically non-conductive material;
• f) infusing unpolymerized thermosetting synthetic resin into the lay-up thus obtained;
• and
• g) applying heat and, if necessary, pressure to cause polymerization of the thermosetting synthetic resin and homogeneous and uniform distribution of the graphene nanoplatelets within a thickness portion of the electrically non-conductive dry fiber sheets forming the second intermediate electromagnetic absorber block.