Automated fiber placement alloys precision fabrication of complex composite structures, but significant thickness reduction may occur during cure due to the presence of voids and excess resin in fiber placed parts. Zero-bleed toughened epoxy resin systems required for many aerospace applications (including Cytec 977 or Hexcel 8552) are particularly difficult to debulk, and hot vacuum bag debulking or interim autoclave processing are widely used with these materials to avoid fiber wrinkling (marcelling). Foster-Miller's Ultrasonic Tape Lamination (UTL) is a highly effective debulking method, capable of providing net thickness as-placed parts. UTL induces virtually instantaneous viscoelastic and frictional heating and intraply nesting. Insitu debulking and controlled staging of thermoset prepreg can be achieved through the use of closed loop temperature control and advanced process modeling. Used in conjunction with E Beam curing or novel thermal techniques, such as solid state postcure, UTL provides an avenue for out-of-autoclave curing of high quality fiber placed structures. This approach offers the possibility of out-of-autoclave processing without the development and qualification of new resin formulations. This paper covers the development of UTL for in-situ debulking and staging. It also includes a discussion of viscoelastic materials characterization and process modeling for carbon fiber/Hexcel 8552 thermoset prepreg.
UTL consolidation and out-of-autoclave curing of thick composite structures
2000
11 Seiten, 11 Quellen
Conference paper
English
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