CASE STUDY OF AIRBUS A350-XWB CENTRE FUSELAGEØ INTRODUCTIONA fuselageforms the main body of an aircraft for the making which composites are taking overmetals. The Airbus A350 XWB consists of three long sections: forward, aft andcentre fuselage all made up of four large compositepanels. In any case, the centre fuselage is the longest of the three, whichjoins the fuselage to the wings through lateral intersections. It is developedfrom six sizeable composite boards made by Spirit AeroSystems (Wichita, Kan.
).Fabricated at Spirit’s office in the U.S. (Kinston, N.C.
)Spirit’splan uses “smart manufacturing” practices a physical format thatenhances work process and the most recent automated fibre placement (AFP)technology to expand profitability. Substantial segments are developed frommore straightforward, all the more effortlessly fabricated subcomponents thatare additionally less demanding to repair and keep up.Ø MATERIALSThe AirbusA350 XWB utilises Carbon Fibre Reinforced Plastic (CFRP) to make the compositefuselage. It has properties like high strength to weight ratio, high tensilestrength and high elastic modulus similar to steel. Carbon fibres are producedusing polymeric resins, carbon fibres, rayon or petroleum pitch. Thesematerials are natural polymers. The correct structure shifts from oneorganisation to another.
During the assembling procedure, an assortment ofgases and fluids are utilised. Some of these materials are intended to reactwith the fibre to accomplish a particular impact.The carbonfibre raw material Polyacrylonitrile (PAN) normally costs around $21.5/kg, witha conversion efficiency of just 50%. The raw materials have a great availabilitybut the manufacturing and designing processes are very expensive. Advancement inmanufacturing processes are done like developing highly reactive resins toreduce cycle time for cost reduction.
Ø DESIGNAirbusselected vast fuselage boards, rather than unitising fuselage barrel segments,since they can be custom fitted according to their laminate arrangement,thickness and the load each piece of the airframe has to take. This empowers afuselage upgraded for better performance and weight. The utilisation of less,longer areas additionally implies less joints that are said to be better putfor load and weight streamlining.
The Boeing 787’s fuselage utilised fourshorter, one-piece composite barrels. The Airbus selected outline is requiredto maintain a strategic distance from the fit issues Boeing had when it joinedthe initial 787 barrels made with very different tooling approaches. The A350’scomposite boards join an external copper work to deal with the immediateimpacts of lightning, passing the electrical current around the fuselageinnocuously. This versatility keeps away from added structure related withelectrical structure network (ESN) components which would include more weightthat would balance the light weighting pro of a CFRP fuselage.
Subsequently,the six gathered segments of the centre fuselage, at 19.7m long and 6.7m indiameter, will measure a approx.
4,082 kg.Ø MANUFACTURINGThe centre fuselage is the largest and the most complexcomponent of the aircraft. As the centre fuselage is to be connected with thewing there are two lateraljunction panels with both convex and concave curvatures, which provide anaerodynamic fairing and structural connection to the all-composite wingbox. Themanufacturing method used for making this component is automatedfibre placement (AFP) which is a common process for manufacturing largecomponents. This techniqueenables complex geometries to be produced. The manufacture of section beginswith an ElectroimpactInc.
(Mukilteo,Wash.) S-15 dual-head AFP machine that was designed for these large structures.The machine lays up Hexply M-21Ecarbon fibre/toughened epoxy prepreg from Hexcel(Stamford, Conn.) onto a male Invar tool.· AUTOMATEDFIBRE PLACEMENT (AFP)The process optimises the reinforcement lay-up, closecontrol of process parameters and minimize the number of defects. Anautomated fibre placement machine applies tows (of 3.
175 mm to 12.7 mm width), in theform of a ribbon of unidirectional prepreg with fibres in either thermosettingor thermoplastic matrix onto the surface of a mould through a placement head. In order to obtain the required dimensions, the tape placement isoptimized, controlling the orientations and lengths of the tapes to limitdefects (gaps and overlaps). The AFP process requires pre-impregnatedtapes, as the material is heated locally.
The lack of tack and drape of mostthermoplastic prepregs is a drawback. In general, after tape lay-up byAFP components are consolidated in an autoclave to minimize defects.MTorres supplied Spirit’s two 5m/16.4-ft tall columnar ultrasonic (UT)inspection machinesto achieve simultaneous inspection of inner and outer skins for eachfuselage panel. Most of the frames are composite, but a few are aluminiumto support the electrical structure network.Ø ISSUES IN DESIGNINGAND MANUFACTURING COMPOSITE FUSELAGE Metal-to-composites interfacesDamage tolerance of crown, keel, and side panelBasic detail and assembling costThe high temperature thermoplastic polymers used inaeronautical structures are not suited to AFP with natural fibres.Development of joints for major panel splicesØ PROPOSEDSOLUTIONSAdhesive bonding method shows potential to join thepanels with other components.
Hybrid laminates could be used in order to achieve abetter fatigue resistance.Biocomposite components can be put into manufacturingaccording to aerospace industry’s specifications. Ø CONCLUSIONthesensitivity of these polymers to the temperature, both structural andbiochemical degradationAirbushas opted to clothe a pre-fabricated fuselage skeleton with large carbon fibrecomposite panels. This less radical solution reduces risk, says Airbus, whilealso having the advantage that panel properties can be optimised to theirlocations in the fuselage (whether crown, belly or sides) with resultant weightsaving. Other benefits include easier handling, less expensive autoclaves andthe fact that having a panel fail at post-manufacture inspection for any reasonis less of a setback than losing a complete barrel.CASE STUDY OF EUROFIGHTER TYPHOON RADOME”If you lost the radome, you’d losethe aircraft” -unknownØ INTRODUCTIONEurofighter Typhoon is the world’s mostadvanced swing-role combat aircraft. An aircraft radome is a dome or a structure shielding radarhardware and produced using material transparent to radio waves, particularlyone on the external surface of an aircraft.
Eurofighter’s radome is a complexstructure manufactured to close tolerances. Eurofighter’s radome is a complexstructure manufactured to close tolerances. It includes layers of frequency-selectivesurface (FSS) materials, comprising metallic micro-arrays that absorb allfrequencies outside the band of the aircraft’s own radar. The radome mustremain transparent to the radar to reduce the Typhoon’s frontal radarcross-sectional area and hence its detectability. Jenoptik is a leadingmanufacturer for making civil and defence aircraft radomes who havemanufactured Eurofighter Typhoon’s Radome for Airbus Group and BAE Systems.Ø MATERIALSThe 2.
30-meter-longradome is made from fibre-glass-reinforced plastic and forms the tip of theaircraft. It acts as a cover for the sensitive radar system behind it and undergoesradar-electrical optimisation so that the radar signals can be received andtransmitted without distortion. fibre-glass-reinforced plastic is made from extremely fine fibres of glass,resins and fillers.
It costs approx. $10 per square metre. It has properties like good heat resistance,high insulating properties, high tensile strength and elastic modulus.Ø DESIGNRadome design very requiresspecial knowledge and techniques and the use of proper tools and materials asdue to the essential properties that a radome needs to bare such as Transmissivity(he ability of a radome to pass radar energy through it), Reflection (thereturn or reflection of the outgoing radar energy from the radome back into theantenna and waveguide system), Diffraction (the bending of the radar energy asit passes through the radome).Radomes suffer ultra-high temperature (1500-2000 °C)which is also a huge challenge for radome material.Ø The design Ø considerations for the radome areØ The design Ø considerations for the radome areØ The design Ø considerations for the radome areØ The design Ø considerations for the radome arHigh performance radar radomes are veryprecisely constructed and sometimes the slightest change in their physicalcharacteristics, such as excessive layers of paint, can adversely affect radarsystem performance. All repairs to radomes, no matter how minor, should returnthe radome to its original or properly altered condition, both electrically andstructurally. An improper minor repair can eventually lead to an expensivemajor repair.
Ø MANUFACTURINGThe Eurofighter Typhoon’s Radome ismade of GRP (Glass Reinforced Plastic) which helps to have overall economy andweight reduction. It weighs approx. 65 kgs.
Themost common process used to manufacture fibreglass radome is Pultrusion. The processis great for producing components that need to be light weight, excellentperforming through the waves (wave transmitting rate is as high as 98%), shapeand size diversity, smoothly adapting to a variety of harsh environment andother characteristics, and this process have been widely used in aerospace.The glass fibre rovings, stitch continuous polyester as reinforcing material,and unsaturated polyester resin (or vinyl resin) thermosetting plastic productsmatrix materials by pultrusion compounded high temperature moulding equipment,can be carried out according to the requirements of the surface of the paintcoating.
To achieve repeatability between production units, manufacturers employan automated fine-tuning system. This corrects the radome electrical thicknessat 4000 points across the entire surface before it goes onto electricalacceptance. These partscan also be oven-cured at temperature up to 400°F or in autoclaves, whichrequire high pressure cures at high temperatures.
Ø ISSUES IN DESIGNINGAND MANUFACTURING RADOMESPoorfabrication techniquesPatchesformed of different thicknessAbruptchanges in cross-sectional areasPoorbonding of skin to coreColorDifference in Pultrusion process: Heating points will lead to uneven shrinkageand the color difference (also known as color transfer) Ø PROPOSEDSOLUTIONSInstead of constant manual inspections duringthe manufacturing like checking the symmetry to avoid component bending thatcould lead to future failure of the product or, automated testing methods canbe developed that can be placed between the manufacturing belts to checkfactors like symmetry, temperature, resin mixture ratio, colour of the component.Especially a very continuous process like Pultrusion can be intervened by a setof automated testing equipment between the production stages in order toimprove the quality of the overall process and to as many unqualified productsat the end of the process. Ø CONCLUSION