CASE STUDY OF AIRBUS A350-XWB CENTRE FUSELAGEØ INTRODUCTIONThe AirbusA350 XWB consists of three long sections: forward, aft and centre fuselage allmade up of four large composite panels.
In anycase, the centre fuselage is the longest of the three, which joins the fuselageto the wings through lateral intersections. It is developed from six sizeablecomposite boards made by Spirit AeroSystems (Wichita, Kan.). Fabricated atSpirit’s office in the U.S. (Kinston, N.C.
)Spirit’s plan uses “smartmanufacturing” practices a physical format that enhances work process andthe most recent automated fibre placement (AFP) technology to expandprofitability. Substantial segments are developed from more straightforward,all the more effortlessly fabricated subcomponents that are additionally lessdemanding to repair and keep up.Ø MATERIALcarbon fibre reinforced highperformance thermoplasticsPEEK (polyetheretherketone)Ø DESIGNAirbus selected vast fuselage boards,rather than unitising fuselage barrel segments, since they can be custom fittedaccording to their laminate arrangement, thickness and the load each piece ofthe airframe has to take. This empowers a fuselage upgraded for betterperformance and weight. The utilisation of less, longer areas additionallyimplies less joints that are said to be better put for load and weightstreamlining.
The Boeing 787’s fuselage utilised four shorter, one-piececomposite barrels. The Airbus selected outline is required to maintain astrategic distance from the fit issues Boeing had when it joined the initial787 barrels made with very different tooling approaches. The A350’s compositeboards join an external copper work to deal with the immediate impacts oflightning, passing the electrical current around the fuselage innocuously. Thisversatility keeps away from added structure related with electrical structurenetwork (ESN) components which would include more weight that would balance thelight weighting pro of a CFRP fuselage. Subsequently, the six gathered segmentsof the centre fuselage, at 19.
7m long and 6.7m in diameter, 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 techniqueis used to produced complex geometries. The manufacture begins with an ElectroimpactInc.
(Mukilteo,Wash.) dual-head AFP machine that wasdesigned for these large structures. The machine lays up Hexply M-21E carbon fibre prepreg from Hexcel(Stamford, Conn.) onto a male Invar tool.
· AUTOMATED FIBRE 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 thermoplastic matrix ontothe surface of a mould through a placement head. In order toobtain the required dimensions, the tape placement is optimized, controllingthe orientations and lengths of the tapes to limit defects (gaps and overlaps).The AFP process requires pre-impregnated tapes, as the material is heatedlocally. The lack of tack and drape of most thermoplastic prepregs is a drawback.
In general, after tape lay-up by AFP components are consolidated in anautoclave 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.· ISSUES IN DESIGNING AND MANUFACTURING COMPOSITE FUSELAGEMetal-to-compositesinterfacesDamage 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.· PROPOSED SOLUTION 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. Ø POTENTIAL TRENDAdhesive-bonding Hybrid laminates show potential for use inweight-sensitive and fatigue-and fracture-critical components. Hybrid laminatesoffer fatigue crack growth resistance that is signific biocomposite components.