Plasma Deposition of Metal in Composite Panels
manufacturing
Plasma Deposition of Metal in Composite Panels (LAR-TOPS-99)
Processing enables functional design using metals in composites
Overview
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.
The Technology
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.
Benefits
- Metal deposition directly onto fabric eliminates the need for separate foils and provides a better interlayer bonding
- Porosity of coated fabric still allows for resin infusion and improved quality
- Metal provides textured surface for improved matrix bonding
- Variety of fabrics and metal alloys (e.g., aluminum, titanium, copper, glass fabric, carbon fabric, epoxy, polyimide) can be used to meet application requirements
- Tailorable process with flexibility in terms of resin pathways (size, pattern) and finished parts (thickness, texture, permeability, single or multi-sided, etc.)
- Final laminate products can vary in terms of stacking sequences, number of plies, metal/composite ratios, and fabric perform types
Applications
- Aeronautics and aerospace - e.g., functional materials such as embedded lightning strike protection for aircraft, and structural applications such a fuselage skins, leading-edge wings, floors and liners, pressure bulkheads, landing gear doors, flap skins, and blast-resistant cargo containers
- Pressure vessels and storage tanks
- Ballistic protection
- Automotive structures
- Composite doors and windows
Technology Details
manufacturing
LAR-TOPS-99
LAR-17485-1
FIBER METAL LAMINATES MADE BY THE VARTM PROCESS. B. J. Jensen, R. J. Cano, S. J. Hales, J. A. Alexa, E. S. Weiser1, A. C. Loos and, W. S. Johnson. ICCM-17 17th International Conference on Composite Materials, July 27-31, 2009. https://ntrs.nasa.gov/citations/20090028660
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Similar Results
Fabrication of Fiber-Metal Laminates with Non-Autoclave Processes
The FMLs resulting from the NASA process have similar properties to traditionally produced metal/composite hybrid laminates including, as compared to either the composite or metal only structures, improved load carrying capability, lighter weight, improved stiffness, improved impact resistance and damage tolerance, and improved permeation resistance. The NASA process can be applied to various FML types, including GLARE (glass, aluminum, epoxy), and TIGR (titanium, graphite). Typical manufacturing processes are costly and complex shapes are hard to produce, whereby the NASA process enables use of these kinds of laminates without an autoclave or press, thus increasing the size that can be produced and decreasing the cost.
The resin pathways in the foils enable connection between the plies that can improve the interlaminar strength of the final part. Functionally the NASA process creates resin columns in the transverse direction of the plies. NASA is working to optimize the final properties by varying the size and distribution of the pathways.
Fiber-Metal Laminate Manufacturing Technique
Fiber-Metal Laminates (FMLs) are composite materials that consist of conventional fiber reinforced plastics with the addition of a metal component, typically a foil or mesh layer(s). The metal component offers the advantage of incorporating metal-like properties to the composite construction. While a range of potential advantages and applications have been discussed for FMLs, the primary application to date has been for aircraft structures, with one potential advantage being the lightning strike protection (LSP) offered by the improved electrical conductivity. As aircraft construction has moved to composite structures, there has been an increasing need for such conductive composites. Similarly, with increasing use of composites for other large structures, e.g. wind turbines, there are an increasing number of potential applications for lightning strike protection materials. Other advantages of FML are improved impact and fire resistance.
This innovation provides a method for making FML materials that incorporate nanotube reinforcement. The method involves the use of RF plasma spray to directly form and deposit nanotube materials onto fibers/fabrics, which can then be manufactured into composite structures by infiltrating the fiber with resin, and consolidating the structure via autoclave processing or via the use Vacuum Assisted Resin Transfer Molding (VARTM) composite manufacturing methods. Nanotubes incorporated into the structure in this manner can be of several types, for example boron nitride or carbon nanotubes. The objective of this innovation is to incorporate the nanotube materials in the FML in order to improve the mechanical properties.
Functionally Graded Metal-Metal Composite Structures
In order to improve the properties of monolithic metallic materials, alloying additions are made that create secondary phases and/or precipitate structures. These improvements must occur during melt solidification and are governed by the thermodynamics of the process. That is, optimizing the metallic alloy is possible only as much as thermodynamics allow.
Developing novel methods to combine metallic compositions/alloys into a fully dense material is of interest to create materials with novel property combinations not available with monolithic alloys.While various approaches for layering two-dimensional materials exist, their capabilities are typically limited and non-isotropic. Further, while three-dimensional composites may be formed with conventional powder metallurgy processes, it is generally very difficult to control the arrangement of the phases, for example due to randomness created by mixing powders.
This invention is method for creating a multiple alloy composite structures by forming a three-dimensional arrangement of a first alloy composition, in which the three-dimensional arrangement has a substantially open and continuous porosity. The three-dimensional arrangement of the first alloy composition is infused with at least a second alloy composition. The three-dimensional arrangement is then consolidated into a fully dense solid structure.
In-Situ Selective Reinforcement of Near-Net-Shape Formed Structures
This innovation allows the incorporation of metal matrix composite reinforcing material into a metallic structure as part of the structures fabrication process. It does not require secondary processing that may affect the structures mechanical properties. It does not require bonding agents that would limit the benefits of the reinforcing material. It adds reinforcement to only the specific regions of the structure that need enhanced strength, stiffness, and/or damage tolerance, thereby allowing for more efficient design and reduction in structural weight.
Automated Tow/Tape Placement System
This NASA invention enables several benefits that mitigate limitations associated with conventional ATP systems, including the following: (1) avoids obtuse head rotation or cross-tool translation when laying adjunct tape plies, (2) simultaneously places tape on both sides of a part via two robots, (3) eliminates external anchoring frame requirements, and (4) translates parts during build while also translating the applicator head. The ability to perform simultaneous layup on opposite sides of the component, as well as reduction of head rotation reversal during bidirectional tape layup, offers increased layup speed. The invention offers increased placement accuracy as a result of reduced movement between tape layup operations and the eliminated need for an anchoring frame (facilitated by simultaneous pressure extrusion of prepreg by the two robots).
NASAs automated tow/tape placement system has two key unique features: the use of two opposed ATP cars to enable a tool-less process, and an on-the-fly reversal tape/tow laydown tooling head. The system uses two opposing (i.e., underside-to-underside) ATP cars, and can build parts vertically, horizontally, or at any other angle, depending on the workspace available. The ATP die wheels can be reversed or turned to draw the composite back and forth at different angles to create a layer-by-layer composite structure. Both cars can dispense TPC tape thus, either car can function as an opposing tool surface while the other performs prepreg lay-up. For structures that do not vary in thickness, both cars can lay tape at the same time doubling layup speed. Current ATP robots must rotate the large tooling head, or traverse panels without layering tape to achieve bidirectional layup, where each additional movement introduces alignment error. To increase layup rate while simultaneously minimizing misalignment, NASAs system incorporates an on-the-fly reversal tape/tow laydown tooling head to enable efficient bidirectional layup.