Original Date: 10/14/1988
Revision Date: 01/18/2007
Information : Complex Cross-Section Composite
Bell Helicopter Textron, Inc. (BHTI) has developed a manufacturing process for the fabrication and subsequent bonding of complex shaped I-beam stiffeners to the V-22 wing structure. Utilizing a combination of thermal draping and vacuum compaction, uncured stiffeners are formed which do not exhibit ply deformation, cap thinout, or web taper when cured and co-bonded to the wing planks.
Preplied stacks or charges of up to 22-plies of graphite epoxy are formed over a graphite epoxy C-channel mandrel. Forming is accomplished under vacuum once the lay-up has been heated to 150 degrees F. After the C-channels are formed they are placed back-to-back and pinned to form the basic I-beam configuration. The I-beam is subsequently compacted under vacuum at room temperature for a minimum of eight hours. During this time, compaction forms the web and foot shapes to within ten percent of the final part thickness. Formed radius fillers and additional cap materials are added to the I-beam which is then subjected to another vacuum compaction cycle.
Uncured I-beam stiffeners, still incorporating the graphite epoxy C-channel mandrels, are placed on the wing skin and are cured and co-bonded to the surface under standard autoclave pressures and temperatures. Finished, cured in place stiffeners require no additional trimming or machining.
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