Process for making an injection molded fan blade

摘要

A variable pitch fan for a helicopter equipped with a NOTAR TM mechanical antitorque directional control system comprises a plurality of blade assemblies. Each blade assembly includes a blade portion, which is molded from a blended material which includes fiber reinforced polypropylene. A key to the invention is the use of long fibers, having a length of at least approximately one-half inch, for reinforcement, the long fibers providing for about twice the pull-out strength of short or chopped fibers. Another key aspect of the invention is the use of a blowing agent in the blended material, which serves to reduce weight and warpage by creating a foamed structure having a variable density, the structure retaining considerable strength because of the fiber reinforcement. The blade portion is molded about a spar which has holes therethrough, the holes providing a mechanical interlock between the blade and the spar.