The Use of Kevlar 29 for Main Rotor Hub Structures

Work has been conducted at Hughes Helicopters, Inc. (HHI) to develop an Advanced Rotor System which reduces part count, weight, and cost compared to a standard rotor system. The use of composite materials to achieve these objectives has been investigated. Specifically in regard to the hub, a flexbeam system has been developed which eliminates hinges and heavily loaded bearings. The primary structural material for this flexbeam is Kevlar 29. Material tests were conducted on this fiber which produced design allowables for the design and stress analysis of the hub flexbeam. The design methods are presented. In addition, component fatigue testing which led to further flexbeam improvements is discussed. This work shows the benefi ts of Kevlar 29 in this appli cation which have culminated in flight tests of the flexbeam system.