Metallic Weight Reduction in Composite Materials and their Physical Properties
Danut Dragoi, PhD
As a fact metallic weight reduction is happening in many industries like aeronautics, automobiles, building materials industries. This requirement is dictated by the energy consumption factors that guides daily every human activity. In some engineering applications including health science and human care, the metals and alloys are used as substitutes for mechanical properties, which in general exceed those of natural bio-materials in human body. As an example, an implant of Ti has about four times more strength than cortical bones in compression mode. In this example the interface metal/bone inside the human body is not perfectly bonded, therefore the metal has to be coated with a bio-ceramic layer. In this way a composite material is created. As we know Ti has a density of about 4.54 g/cc, which is greater than the average human body density, that is close to 1.01 g/cc. In fact a more proper comparison of Ti density should be done with the value of 1.9 g/cc, the density of the compact bone.
Because Ti is the only metal that work well in human body, other metals are not taken into consideration. Therefore, engineered porosity has to be introduced as the solution for light-weighting of the implant in this case. Materials science calculations as well as lab tests show that solution is real and can be done. The newly developed Medical 3D printing machines for Ti prosthetic includes porosity as empty spaces defined by trusses. Today, the principle of porosity becomes a trend not only in the health science application explained before, but in aeronautics too. Boeing announced recently that a super light air metal structure that has a porosity of about 99.99% was realized with same scope of light-weighting reduction of a composite material. A decade ago, NASA announced the aerogel the material with 99.8% porosity. Using the same principle of porosity, researchers at NASA created also open spaces within a polymeric structure by eliminating the content of water. These new polymer aerogels have improved mechanical properties if they are reinforced with polymeric fibers, tiny stainless steel wires or even graphene, the 2D one-layer Carbon atoms structure. These very light material composites become more interesting when fabricated in thin films. Their main physical characteristic is the thermal insulation effect that can be considered in many applications. The increase of the porosity in composite material by preserving physical properties, such as mechanical strength as in the bulk materials is definitely a trend in actual efforts of materials scientists to make new materials.
Another area of interest for Materials Science is the replacement of costly and rare earth metals for producing high energy magnetic product BHmax permanent magnet for electrical automobile industry. In fact the on going project in permanent magnets, “Project for High Performance Anisotropic Nanocomposite Permanent Magnets with Low Rare-Earth Content”, shows that the endless metallic combinations for producing permanent magnet is a viable and realistic approach.
Another area of interest is on non-conventional energy. Tesla’s Powerwall product is using Li-ion batteries for storage of electrical energy produced by Solar Photo-voltaic Cells.
The improvements of the Li-composites electrodes in Li-ion batteries is the actual trend that defines the Powerwall products but also the usage of the Li-ion batteries for electrical cars and portable apparatus like iPhones, laptop computers, and electronic instruments. Reducing the car weight as well as the weight of the car batteries is also an important trend in Materials Science. As we can see, the powers sources like Li-ion batteries and the electrical motors based on Neodymium magnets as the main driving force of electrical cars require improvements in different areas of metals research.
The complexity of hybrid metallic and organic composites is discussed at molecular size scale. The Gold/Alginate is an example of metal/organic nanocomposite in which the metal as a nano-wire is improving the electrical conductivity of the composite used as a patch tissue for repair of tissue damaged by myocardial infarction,
SOURCE
Patent, http://www.google.com/patents/US9114009
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