Failure criteria development for dynamic high-cycle fatigue of ceramic matrix composites

Acoustic fatigue in aircraft is typically characterized by random, high-fre quency excitation that results in fully reversed bending in panels. Because of the expense of testing panels in an acoustic environment, traditional m ethods have first tested small cantilevered coupons on electrodynamic shake rs to determine the strain vs number of cycles to failure behavior. A numbe r of variables have been studied to provide failure criteria for the specim ens. Developing criteria are examined for a relatively new class of materia ls, ceramic matrix composites, which are characterized by having a brittle matrix, which has a stiffness that is a significant fraction of the fiber v alue. Also discussed are experimental techniques that reduce the scatter as sociated with such data.