Failure prediction of glass/epoxy specimens using NOL ring test and acoustic emission technique

Methods have been evolved for the evaluation of filament wound composite structures making use of Naval Ordnance Laboratory (NOL) ring specimens. Internal pressure could be applied to the ring shaped specimens similar to hydro burst test of actual pressure vessels. In this investigation, suitable testing technique to estimate the tensile strength of NOL rings is presented. Also, in order to demonstrate the advantages of burst test, appropriate testing and evaluation of glass/epoxy rings under defect free as well as adverse conditions is carried out through acoustic emission (AE) monitoring. Thus, the degradation on the strength of glass/epoxy rings is understood through AE technique. Moreover, a mathematical approach is developed to predict the failure load of glass/epoxy rings at relatively lower load level itself with a reasonable error margin. Due to simplicity of this technique, a number of ring tests could be repeated easily as against the burst test of actual pressure vessels.