Nondestructive evaluation of CFRP rocket motor nozzle holders by acoustic emission1

An acoustic emission criterion of fracture is developed for CFRP rocket motor cases. This criterion can be applied to detect failure extension in FRP dynamically. Both the criterion of the fracture theories and the nondestructive evaluation methods for FRP are discussed. The developed AE criterion is based on statistics which include the prior distribution, the data distribution and the posterior distribution. The AE criterion shows the equivalent pressure which relates to the damage extension of the master sample. Three types of the equivalent pressure criteria, such as the fiber breakage criterion, the fiber breakage and delamination criterion, and the all fracture criterion are based on AE amplitude distribution. Weight functions are used in this treatment based on the AE source characterization theory. The predicted burst pressure and the safety ratio are calculated by the equivalent pressure and the proof test pressure. The results of the evaluation indicate that the predicted burst pressure is 7.9 MPa and the safety is 1.6. These results are in good agreement with the strain measurement.