Plasma Deposition of Metal in Composite Panels

NASA's plasma-deposition process provides the ability to tailor various properties while designing functional parts by selecting specific materials and processing parameters to meet the end goal. Specifically, the plasma process deposits metal particles that are heated as they travel axially at low velocity through an inert gas plasma. The accelerated powder particles become molten, strike the substrate fabric (uniaxial, biaxial, and multiaxial) and rapidly solidify, imparting very little heat to the substrate while forming a metal-to-fiber bond, as well as a metal-to-metal bond. The resulting metal-coated fabric is porous, so the polymer matrix can pass through the product precursor during the infusion process. The amount of metal deposited can be controlled, as can the number of plies of fabric that are ultimately stacked to produce the preform for the polymer matrix infusion process. A variety of infusion processes can be utilized to prepare the FML, including resin transfer molding (RTM), resin film infusion (RFI), and vacuum-assisted resin transfer molding (VARTM). The tailorable aspect of the process allows for specific product design. By varying the combination of metal particle, fiber, fabric type, metal layer thickness, fabric direction, number of layers, polymer matrix resin, infusion process, and cure conditions, the characteristics of the final part can meet the needs of various applications. NASA's Langley Research Center has developed a new technique to enable the preparation of metal/composite hybrid laminates, also known as fiber metal laminates (FML), by depositing metal directly onto fabric using a plasma deposition process. FMLs provide a useful combination of structural and functional properties for both aerospace and non-aerospace applications. Currently, FMLs are prepared in a compression process utilizing a press or autoclave with metallic layers (foils) sandwiched between layers of glass or graphite prepreg (preimpregnated fibers with a matrix resin). The NASA process deposits the metal on the fiber via plasma deposition. The porosity of the coated fabric allows for resin infusion.