| Summary: | A postbuckled, carbon fibre reinforced plastic (CFRP)
wing box has been designed, manufactured and tested
for an aerobatic light aircraft, the Cranfield Al.
Methods of analysis have been evaluated including:
i) Non-linear finite element analysis for the
prediction o-f panel postbuckling.
ii) A simpler technique based on an effective
width method. This forms the core of a design program,
'oPTIMIST'. It predicts buckling loads, postbuckled
reduced stiffness and overall column failure of
co-cured hat stiffened panels. It then optimises the
con-Figuration of a box beam for minimum weight.
iii) The use of the effective width method allied
to a large scale, linear finite element analysis.
The work includes the development of a new method
o-F construction for composite box structures. The wing
skin sti-Ffeners and rib flanges are co-cured
together. Integral slotted Joint features are formed
in each part. The structure is then adhesively bonded
together. A full description of the manufacture o-F the
wing box is included.
The structure was also tested in a specially
designed rig. It was tested to ultimate design loads
in:
i) Positive bending to 13.33.
ii) Negative bending to -96.
iii) Pure torsion resulting from full aileron
load.
iv) Torsion with 96 bending.
The compression panels were seen to postbuckle and
recover in each load case. Results are compared with
theory, and with the original aluminium Al wing. The
structure is 257. lighter than its aluminium
counterpart.
Finally, suggestions are made for possible areas
of further research.
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