Space Shuttle filament wound case compressive strength study. I - Testing

Abstract

Immediately before liftoff, ignition of the Space Shuttle main engines places a significant bending moment on the filament wound cases of the solid rocket booster motors. This results in substantial compressive loading of the aft end of the composite case which, because of attachment requirements, has a complicated design including inserted broadgoods and helical ply dropoffs. To investigate the performance of the filament wound cases during the prelaunch load environment, a comprehensive study was initiated which included both testing and analysis. The results of the test program, which included testing of several full-scale and over three hundred subscale articles, will be described. The test program began with a short development effort to establish appropriate subscale test specimens for determining the material compressive strengths. Once these were established, a more comprehensive test program was initiated to determine the effects on strength of both processing and design changes. Full-scale cases were tested in a simulated prelaunch bending environment in order to validate the analysis predictions. In all tests, special attention was given to observation of the failure sequence which involved a complex process of load transfer from the region of helical ply dropoffs to the broadgood termination region.