CASE STUDY OF AIRBUS A350-XWB CENTRE FUSELAGE
A350 XWB consists of three long sections: forward, aft and centre fuselage all
made up of four large composite panels. In any
case, the centre fuselage is the longest of the three, which joins the fuselage
to the wings through lateral intersections. It is developed from six sizeable
composite boards made by Spirit AeroSystems (Wichita, Kan.). Fabricated at
Spirit’s office in the U.S. (Kinston, N.C.)
Spirit’s plan uses “smart
manufacturing” practices a physical format that enhances work process and
the most recent automated fibre placement (AFP) technology to expand
profitability. Substantial segments are developed from more straightforward,
all the more effortlessly fabricated subcomponents that are additionally less
demanding to repair and keep up.
carbon fibre reinforced high
Airbus selected 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 a fuselage upgraded for better
performance and weight. The utilisation of less, longer areas additionally
implies less joints that are said to be better put for load and weight
streamlining. The Boeing 787’s fuselage utilised four shorter, one-piece
composite barrels. The Airbus selected outline is required to maintain a
strategic distance from the fit issues Boeing had when it joined the initial
787 barrels made with very different tooling approaches. The A350’s composite
boards join an external copper work to deal with the immediate impacts of
lightning, passing the electrical current around the fuselage innocuously. This
versatility keeps away from added structure related with electrical structure
network (ESN) components which would include more weight that 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 in diameter, will measure a approx.
The centre fuselage is the largest and the most complex
component of the aircraft. As the centre fuselage is to be connected with the
wing there are two lateral
junction panels with both convex and concave curvatures, which provide an
aerodynamic fairing and structural connection to the all-composite wingbox. The
manufacturing method used for making this component is automated
fibre placement (AFP) which is a common process for manufacturing large
components. This technique
is used to produced complex geometries. The manufacture begins with an Electroimpact
Wash.) dual-head AFP machine that was
designed 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, close
control of process parameters and minimize the number of defects. An
automated fibre placement machine applies tows (of 3.175 mm to 12.7 mm width), in the
form of a ribbon of unidirectional prepreg with fibres in thermoplastic matrix onto
the surface of a mould through a placement head. In order to
obtain the required dimensions, the tape placement is optimized, controlling
the orientations and lengths of the tapes to limit defects (gaps and overlaps).
The AFP process requires pre-impregnated tapes, as the material is heated
locally. 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 an
autoclave to minimize defects.
MTorres supplied Spirit’s two 5m/16.4-ft tall columnar ultrasonic (UT)
to achieve simultaneous inspection of inner and outer skins for each
fuselage panel. Most of the frames are composite, but a few are aluminium
to support the electrical structure network.
ISSUES IN DESIGNING AND MANUFACTURING COMPOSITE FUSELAGE
Damage tolerance of crown,
keel, and side panel
Basic detail and assembling cost
The high temperature thermoplastic polymers used in
aeronautical structures are not suited to AFP with natural fibres.
sensitivity of these polymers to the temperature, both structural and
has opted to clothe a pre-fabricated fuselage skeleton with large carbon fibre
composite panels. This less radical solution reduces risk, says Airbus, while
also having the advantage that panel properties can be optimised to their
locations in the fuselage (whether crown, belly or sides) with resultant weight
saving. Other benefits include easier handling, less expensive autoclaves and
the fact that having a panel fail at post-manufacture inspection for any reason
is less of a setback than losing a complete barrel.
Hybrid laminates show potential for use in
weight-sensitive and fatigue-and fracture-critical components. Hybrid laminates
offer fatigue crack growth resistance that is signific