Ultrasonic Inspection of Filament Wound Graphite Epoxy Cylinders.

摘要

A nondestructive inspection procedure utilizing ultrasonic C-scan imaging was developed to test cylindrical filament wound graphite epoxy rocket motor cases. These cylinders are part of a joint U.S. Army, Navy, NASA, and Air force (JANNAF) research round robin to evaluate destructive testing techniques for this PM of composite. The rocket motor cases are made from T650/42 graphite fibers (Amoco) in a Lincoln Resin Formulation (LRF) and have six layers (twelve plies). The ultrasonic method used to evaluate the rocket motor cases was immersion, pulse-echo defect C-scans. Difficulties and solutions of using this method to evaluate the rocket motor cases will be discussed. The received ultrasonic signals were evaluated for reflections from discontinuities within the material by means of an electronic gate set between the front and back surface reflections. The signals were then imaged in color on a computer according to the amplitude of the reflections. The resultant color C-scans were evaluated to separate the good from the bad. In some rocket motor cases there appeared to be large delaminations and inclusions. There were also some that showed few or no defect indications. Ultrasonic attenuation and time-of-flight (velocity) scans were performed to evaluate their quality. Contact time-of-flight measurements were also taken on a number of cylinders to verify immersion results. Comparisons will be made with transverse compression, transverse tension, and in-plane shear destructive test results. These comparisons will verify the usefulness of electronically gated ultrasonic immersion, pulse echo, defect C-scans on filament wound cylinders.