Composite Materials Used in Aerospace Applications - Essay Example

Composite materials used in Aerospace applications Composite materials used in Aerospace applications Background In the aerospace industry, applications development focuses on the use of lightweight, high-temperature materials for engine applications. Towards this course, it is apparent that the aerospace industry aims at reducing weight, direct operations cost, and fuel consumption. (Edwards, 2008)Numerous researches demonstrate that the significant economic and performance benefits can be attained using lightweight, high-temperature materials that can attain technology readiness. Traditionally, aerospace construction materials include Titanium, Aluminium, and Steel. Aluminium use in Aerospace industry was limited to fatigue and corrosion. Compared to current composites, aluminium corrosion was faster with minute striations indicating airframe fatigue. The striations were at times invisible to the bare eye and this meant that the Aluminium airframes were subject to host checks and other non-destructive tests to identify cracks that could end up being disastrous. Consequently, aerospace industry adopted suitable repair schemes to enhance fatigue metal fatigue life. Fatigue promotion also resulted from compression stresses that called for precautionary measures using various management methods. These management methods included torque tightening and shot peening that became very famous. Additionally, use of metals in aerospace industry was limited to difficulties in further improvement of metallurgy and restricted scope for metal weight reduction(Edwards, 2008). For instance, although Aluminium-lithium achieves weight reduction, the cost of lithium is high and compared to convectional aluminium, while the machining process calls for extreme care. These limitations paved way for the development of superior compound materials to substitute aluminium alloy components for use in the airframes in the 1970s. Composite material and their SWOT analysis Composite materials are composed of minimum of two technologies and/or materials with properties that are specific for a given application and that differ from those of each forming material independently(Edwards, 2008). The resulting composite materials comprise of fibrous fortifications that bind collectively with a matrix material and comprise polymer composites. These composites are mostly plastics strengthened with carbon fibres. Reinforcement process involves setting carbon fibres into resin to form piles or sheets then layered on each other forming sub-components whose strength and stiffness vary depending on the direction of laying down different piles together(Dwarakinath, 2013). In the airframe industry, the formation of carbon components involves arranging carbon piles with the fibres directed towards the main stress. This direction is useful in wings that bend during take-off, flight, and landing given the need for stress endurance across them. Engineers achieve this through 60% fibre orientation along the skin of the wings and the span-wise internal stiffness. In addition, the wings are subject to parallel stresses referred to as shear stresses that engineers combat by directing the piles at 450(Edwards, 2008). Further, spars and ribs components inside the wings are designed in ways that permit them to bear shear stresses and comprise of 80% components of 450 piles. This arrangement promotes minimum dependable material volume and weight with sufficient strength. This reliability is very crucial for engineers who can choose the stiffness properties for the materials under use. The design of aircraft wings is crucial and should be done with the knowledge that their shape affects and is altered by the distribution of their load and lift and this is achievable through collaboration with aerodynamicists(Dwarakinath, 2013). Other applications of polymer composites in aircrafts include flight control surfaces, landing gear doors, propellers, turbine engine’s fan blades, vertical and horizontal stabilizer primary structure, floor beams and floorboards, and other interior components. SWOT Analysis Strengths Composite materials in aircraft applications offer numerous advantages. Some advantages are high strength to weight ratio especially through angle piles arrangements; and fatigue resistance derived from high structural performance in Carbon Fibre Reinforced Plastic or CFRP embedded in epoxy matrix(Edwards, 2008). In addition, composite materials offer tailored resistance within a part enhanced by CFRP moldingto improve aerodynamic and structure performance; reduction of materials waste; and corrosion resistant that reduces costs incurred during aircraft life maintenance and repair. Other advantages include possibility to design complex shapes, reduction in material waste, low pressure cooling, and reduction in parts and fastener count through the reduction of number of joints that are useful for cabin pressure and fuel leakage reduction. These advantages promote stability of panels and guarantee ride comfort(Dwarakinath, 2013). Weaknesses The use of composite materials in aerospace industry has a share of demerits like high vulnerability to impact damage that needs specialized repair techniques and analysis procedures that require additional improvement. Impact damages include dents, piles displacements, porosity, deviations of thickness and height, accumulation and bridging of resin, and starvation of splintered piles of resin(Dwarakinath, 2013). These damages arise from low damage tolerance, and lack of design data and tools with the current ones being under improvement. Composite materials also comprise of uncertainties in prediction of failures and improvements are still underway. Opportunities The promising advancement opportunities for the use of composite materials include innovative manufacturing towards automation, development, and improvement of smart/functional materials through self-healing, heating, morphing, and SHM or structural health monitoring. In addition, there are new recycling technologies under improvement to reduce wastage. Threats The major threats to using composites in aerospace industry include the threat of emerging Titanium cost reduction technologies like FFC-Cambridge technology, which reduces oxygen from Titanium oxides, and the presence of high profile failures for composite materials. Other threats include material shortages, metal innovations like super plastic formation, legislation, and recycling issues(Edwards, 2008). Components of advanced polymer composites Fibres Composite materials comprise of fibres and Matrix. The main use of fibres is reinforcement. The most common fibres used are glass, carbon, and aramid while modest quantities of exotic fibres like boron are also used. These fibres are applicable in high service temperatures hence applied in materials used in aircraft skinning. The main considerations for fibres include density, tensile strength, filament diameter, elongation at break, and tensile module. Improvements are continuing from precursors giving more excellent properties mechanically. Matrices Matrices are crucial ingredients for fibre embedding and offer them a supporting medium. The presence of excellent mechanical properties in fibres depends on the ability of matrices to transfer stresses and so is the final performance of the resultant composites(Key To Metals, 2014). Further, the transfer of stresses in matrices depends on the criteria of stress strain behaviour and adhesion properties. The matrix is essentially plastics in form of polymers grouped into two categories thermosetting and thermoplastics. In the recent past, thermoplastics are a promising matrix materials candidate given their appropriate stress-strain performance, reprocessibility, and imprecise shelf life. As a result, unsaturated polyesters resins slowly face replacement. Polymer-Matrix Composites PMCs Compared to other matrices, polymer-matrix composites are the lightest under study in the advanced High Temperature Engine Materials Technology Program (HITEMP). From their recent applications like in General Electric’s F-404, PMCs demonstrated substantial reductions production costs and engine weight(Key To Metals, 2014). However, some PMCs face low-thermal oxidation stability limits that limit their applications. For commercial use, the available PMCs offer sophisticated high temperature advantages that make them capable to withstand hours of use at high temperatures between 2900 and 3450 C like in graphite fibre/PMR-15 and graphite fibre/PMR-11-55. For full advantages of PMCs applications in aircraft impulsion system, improvements are required on the existing composites especially on the enhancement of thermal oxidative stability such that they can be used in higher temperatures of about 4250 C(Key To Metals, 2014). This is possible with further improvements in polymer matrices stability, improvements in interfaces between fibres and polymer, processing of composites and development of oxidation-resistant coatings. In addition, continuing research on HITEMP PMCs Include: study of the impact of resin/fibre interactions on high-temperature and stability of composites; and extending innovative techniques of processing; investigation of oxidation-resistant coatings. Other ongoing research involves putting together novel polymers with superior thermal-oxidation stability and processability(Key To Metals, 2014). Other matrices include intermetallic –matrix composites and ceramic-matrix composites. The limitations for ceramic-matrix composites are demonstration of metal-like buckle performance, noncatastrophic breakdown, and potency properties that are susceptible to processing-and service-engender faults. Conversely, intermetallic-matrix composites limitations are due to poor low-temperature ductility, and incompatible chemicals and CTE incongruity between potential matrix material and reinforcing fibres. Other limitations include poor low-temperature ductility and trivial temperature oxidation resistance of intermetallic materials. Future of Composite materials Ceramic matrix composites are promising given their lightweight, high-temperature composite materials applicable in aircraft components. These materials promise temperatures as high as 16500 C that is applicable for aircraft parts such as turbine inlet(Reather, 2013). With the use of ceramic matrix composites, advanced engines will permit higher engine operation hence increased productivity. However, the applications of ceramic matrix composites have to consider its limitations and apply it only where necessary. Spider silk fibre is also promising for applications in aerospace industry given its high ductility that allows stretching of up to 140% its normal length and its excellent abilities to retain strength at -400C(Scott, 2014). These composites are then useful in aircraft’s wing joining where varying stresses are experienced. Another advantage is that spider silk is highly biodegradable unlike other composites. The major limitation is that there has not been any successful attempt in the production of the composite and the process is ongoing. Conclusion Compared to metallic materials used in aerospace industry, composite materials have high strength-to-weight ratio and this increase their preference for aircraft applications despite high fabrication expenses. However, metallic alloys are still in use and the biodegradability of composites leaves room for no complete replacing. Bibliography Dwarakinath, N. S., 2013. Rising Adoption of Composites Signify Innovations in the Aerospace Industry, Singapore: Quest. Edwards, T., 2008. Composite Materials Revolutionise Aerospace Engineering. Ingenia, Issue 36, pp. 24-26. Key To Metals, 2014. Composite Materials for Aircraft Industry. [Online] Available at: http://www.keytometals.com/Article103.htm [Accessed 10 July 2014]. Reather, F., 2013. Ceramic Matrix Composites-An Alternative for Challenging Construction Tasks. Technology insights, 1(1), pp. 45-49. Scott, A., 2014. Spider Silk Poised For Commercial Entry. Chemical engineering news, 92(9), pp. 24-27. Read More