Advance Aircraft material: - Essay Example

Advance Aircraft material: A review of literature Department Advance Aircraft material: A review of literature Aircraft designing and all new generation aircrafts are the outcome quintessential efforts in the field of designing as well as in the material necessary for the manufacturing of the aircrafts. In earlier phases of aircraft engineering, the development of better models was greatly affected by the lack of corresponding development in the materials needed for the construction of these models. But the breakthroughs in the technology as well as material science, modern aircrafts can be considered as manufacturing marvel. The research in the field of aircraft material begun with aluminum in 1920s and the metallurgists are now hovering around the composite materials while doing any further research with aluminum alloys. Aircraft structures designed with aluminum based composite materials have given improved results. These materials have helped in developing airframes which are much lesser in weight and at the same time have shown improved strengths. Lighter aircrafts has its own advantages and making a one of this type provides corresponding advantages in terms of maintenance and fuel efficiency. It has its environmental benefits. To achieve best efficiency level in the new design models the material needed for the development of the same should be both strongest and lightest among all substitutes currently available to the technology sector. The research being conducted has the purpose of developing lighter aircrafts through the composite materials with the employment of cheap and high quality manufacturing technologies. Structures can also be developed through the use of conventional aluminum alloys and cheaper to produce but the composite materials despite being costlier both in terms of cost of raw material and development technology are better and are the future of the aircraft engineering (Day). Various components of Boeing made up composite materials Advance aircraft materials are supposed bring further reduction in overall weight of the complete structure and improving the strength with ultimate aim being the increase of the service life of various components of the structure against continuous fatigue and cyclic usage. Materials like fiberglass have got wide spread usage in different components of the aircraft (Quilter). This most common composite material in current scenario was used for the first time in Boeing aircrafts in 1950s. It was developed through embedding process of glass fibers in resin matrix. But with the beginning of 1960s the use of composite materials came under widespread usage with one material acting as a matrix while the others are being embedded in that matrix and serves as reinforcements and holds everything together and intact and with overall effect being greater strength with reduced weight (Quilter). The current researches processes are delving into the development of composite materials with common matrix material under use are epoxy, bismaleimide, or polyimide and glass fiber, boron fiber, carbon fiber and others as reinforcing materials (Day). Taking an airframe developed under the Airbus umbrella, the structure is made up of carbon fiber reinforced plastic and aluminum lithium alloys and sole objective being weight saving structures with best performance in areas where instances of corrosion and fatigue are the most with ease of repair (Day). Manufacturing of composite structures while taking composite material as the raw material begins with the laying out of composite material and then is being put in mold under heat and pressure. The matrix material gets solidified after the removal of heat and then forms various shapes. The strength is increased manifold through the winding of the fibers. Composite materials provide lots of feature through its capability of getting layered. The layering process can help in getting each layer being stretched in different directions so that winding process can achieve best possible result in term of strength. This bending behavior of some of the composite materials makes itself useful in different portions of the aircraft. While under flying conditions different parts of the plane requires different bending requirements. The composite materials help in providing this feature to aircraft designers. The material engineers design the structures accordingly and hence the required behavior can be achieved in certain ways (Day). Component wise a composite a material consists of strong fibers embedded in tough resin matrix. Some of the naturally occurring composite materials are wood consisting of cellulose fibers and lignin matrix. Man-made composite materials as already been stated, have its usage in aircraft structure development. Fiber Reinforcement Carbon fiber reinforced plastic or CFRP and glass-fiber reinforced plastic (GFRP) are the two most widely used when embedded in a matrix of polymer (Quilter). If looking into the polymer, one can see that it is not at all stiff and at the same time lacks strength. But the fibers are stiff and strong but are brittle. Composite materials made out of the two with polymer as matrix and fibers as embedded units are not only strong but also good enough to create bigger structure like the aircraft structure as already discussed. Metal matrix composites (MMC) have also found its usage in aircraft industry. It is a very good example of particulate composites with non-metallic particles embedded in metallic matrix. Silicon carbide particles in combination with aluminum alloy are an example of MMC (Quilter). The benefit with the fibrous composites as compared with metallic materials is the directionality of the property. Reinforcement Individually both fabric particles as well as the metallic materials are isotropic which means properties like strength and stiffness is the same in all-possible directions. But as a single unit inform of composites, these fibrous composites are anisotropic with their property being dependent on the direction of the load with respect to the orientation of the fibers. The composite materials because of the feature of being layered with matrix and fibers can be molded into more complex structures than any of the metallic substitutes available and hence reduce the assembling time considerably. This in the long run makes considerable reduction in the usage of fasteners and joints. There has been a unanimous fact that all structures irrespective of strength of the material and simplicity are weak at joints. Joints and fasteners may pose a weak link in the whole structure (Quilter). Boron nitride fibers can be used as reinforcement while matrix material can be an organic resins or ceramics or aluminum metal. The use of composite materials has now moved on to the designing of primary structure also. Initially only secondary structures were developed from this technology. Taking a stealth bomber as a case; this plane necessitates the usage of radar-absorbing material, which actually adds extra weight to the whole structure. This extra weight can be compensated through the use of composite materials. The continuous research in the field of materials needed for aircraft development is only because of performance degradation of the conventional aluminum planes due to corrosion of aluminum alloys. It not only decreases the thickness of corroded structure but also results fatigue cracks. It finally reduces the material's fatigue life and fracture toughness (Quilter). The advancement in the composite material have often led to the predictions that in future more than two thirds of the aircraft structure will be manufactured with the use of composite materials but its not that much easy to achieve. The most important factor, which is behind the popular usage of composite material, is lightness, which actually affects the overall performance of the plane in term of fuel efficiency, but these materials have its own shortcomings. The composites cannot be termed as a complete solution to all sorts of problem related to the development of aircraft and its maintenance. There have been cases when the material absorbed considerable amount of moisture and the only solution being the complete replacement of the whole portion. A composite material cannot be hammered back to its original shape. So the maintenance cost of structures with composite materials can be much higher than the one made up of aluminum. The higher cost of maintenance have compelled the aircraft manufactures to use greater percentage of composite material only in military planes because of the fact that planes maintained in defense hangers are treated in very different way than the one at any commercial maintenance unit. So, one can zero in to the fact that composites use have necessitated to the development of life management plan (Schoeppner & Curliss, 2002). Polymer matrix which is used in high temperature applications like turbine engines and exhaust system sees continuous degradation and hence continuous inspection as well repair. The high temperature, pressure and presence of moisture limit the life of the polyimide composites during operation. The material life management plan is for ensuring the development of high temperature resistant polymer and its life expectancy factor for the actual prediction of the life component (Schoeppner & Curliss, 2002). Aluminum if compared with the composite materials is easier to obtain and maintain. At the same time, it is extremely tolerant and can withhold great quantity of pressure. The aluminum structure doesn't require immediate repair and the structure can be expected to withhold some more pressure. The composite structures have to be repaired immediately with best possible solution being the complete replacement which means the solution required is only immediate in nature but also very expensive. So aluminum is still the most useful material while aircraft structures are being developed. The aluminum alloys are also another domain of research with most particular being the aluminum-lithium, which is lighter than standard aluminum and has been successfully tested and later used for Space Shuttles (Day). The aluminum is also seeing a series of experiments with all round stress being paid on the creation of alloys. U.S. Department of Energy's Ames Laboratory has succeeded in developing a new aluminum alloy which will see wide spread integration in the development of new jet fighters of US air force (Physicsorg, 2006). The aluminum-yttrium-nickel alloy will also be provided to commercial plane manufacturers for new generation passenger aircrafts. The material is set to replace heavier components of the cooling section of the jet engines and will later be used in the creation of structure of other portions of plane including wing spars. This high quality raw material ensures the reduction by 350 pounds in the overall weight of the plane. Further use of the Al-Y-Ni alloy can result in astronomical reduction in the weight. The alloy has actually powdered form but this powdered metal has to undergo bonding process which results into a partially amorphous, partially crystallized structure with improved performance of factors like strength and ductility. Commercially available Al-Y-Ni alloy has exceeded the tensile strength of 100,000 pounds psi and hence is almost 30,000 psi more than aluminium. To avoid problem of oxidation this alloy is manufactured in an inert environment (Physicsorg, 2006). Thermoplastics provide other dependable option. It is not only light but can easily replace as a matrix material. It has its future in aviation industry because of durability and extended toughness. Ceramics are also an option because of ability to withstand hotter temperature but again its brittle nature makes it less reliable and may make it difficult to maintain (Day). References Physics Org (2006, January 05) "New alloy could boost next generation jet fighter" http://www.physorg.com/news9584.html Schoeppner, G. A. & Curliss, D. B. (2002, September) "Model-based design for composite materials life management", 9th AIAA/ISSMO Symposium on Multidisciplinary Analysis and Optimization Day, D. A, "Composites and Advanced Materials", U. S. Centennial for Flight Commission, http://www.centennialofflight.gov/essay/Evolution_of_Technology/composites/T ech40.htm Quilter, A. "Composites in Aerospace Applications" Head of Strength Analysis Group, ESDU International (an IHS company) http://www.engineers.ihs.com/NR/rdonlyres/AEF9A38E-56C3-4264-980C- D8D6980A4C84/0/444.pdf "Reinforcement" http://www.hardwirellc.com/images/HSR_Beam_lg.jpg "Boeing" http://www.aviation-history.com/theory/composite.jpg "Fiber Reinforcement" http://www.astm.org/IMAGES/SNIMAGES/Laminatefinal.gif Read More