FATIGUE DATA ON A VARIETY OF NONWOVEN GLASS COMPOSITES FOR HELICOPTER ROTOR BLADES.

Abstract

Fatigue is one of the most critical design considerations for a helicopter, especially its rotor blades. The acceptance of glass fiber reinforced composites for the rotor blade structure has created a need for fatigue data. The fatigue testing described here was undertaken to determine which of the many raw material variables could contribute to improving this specific property. A series of thirty curves, alternating stress versus cycles to failure (S-N), have been developed for a number of the raw material variables in nonwoven glass fiber reinforced epoxy composites. The S-N curves indicate differences in the reproducibility and data scatter in the two orientations studied. The O-deg orientation gave greater scatter in data than the plus or minus 45-deg. Of the two orientations used, the plus or minus 45-deg orientation gave greater spread between the variables being studied. The variation between the poorest and best materials tested was 85 percent.