Resin formulation and composite fabrication

Comparison between strengths of etched and unetched carbonized fibers 

A bold scheme was embarked upon to establish whether it was feasible to use carbon fiber, which hardly existed at this time, into the Tristar engine. Trial sets of carbon fiber 

Problems associated with the use of prepreg for composite fabrication included a high bulk factor and difficulties in obtaining an optimum resin pre-cure to ensure correct consolidation. One approach was to use pressure assisted resin injection, where a fiber preform contained in a mold was evacuated and a fairly mobile resin pumped in under pressure [64]. To help maintain the accurate alignment of the fiber in the perform, it was held in place by a resin binder made of about 4% polysulfone applied as a solution in methylene chloride, drying to remove solvent and then followed by a short treatment at 320° C to fuse the polysulfone onto the fiber. Next, a laminate of primed sheets was prepared, which was about 2.5 times the bulk volume of the finished composite (i.e., when compressed at 0.65 f/). Two techniques were used to consolidate a preform. 

The other method, which was successfully used for the production of nose cones, was to add a measured amount of methylene chloride solvent onto the laminate in the die, applying minimal pressure and when consolidated, warming the die to evaporate the solvent, which boiled at 40° C, again producing a similar preform. The individual laminates could then be peeled apart and relocated to build a de-bulked cone-shaped preform. 

A method of manufacturing thermoplastic composite materials by a modified film stacking process was patented [131] involving sandwiching sheets of unidirectional carbon 

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