Progressive Failure Analysis of Internally Pressurized Noncircular Composite Cylinders

Abstract

A progressive failure analysis, based on the capabilities of the finite-element program STAGS, is used to study initial matrix cracking and the subsequent progression of cracking with increased pressure in a small-scale internally pressurized laminated fiber-reinforced quasi-isotropic elliptical composite cylinder. Primary interest is in whether or not a continuous path of matrix cracks occurs through the cylinder wall, thereby providing a potential leakage route for fuel. However, here there is also interest in using various material degradation schemes and a number of failure criteria to predict initial and subsequent cracking to determine how sensitive the predictions are to these variations. Specifically, comparisons are made between the case of degrading both E 2 and G 12 when matrix cracking is detected, and the case of degrading just E 2 . The degradation can be a one-time degradation, or it can occur recursively so that at each load step previously failed material is further degraded. Several levels of degradation are investigated. Additionally, predictions using the maximum stress criterion to detect failure are compared with predictions based on the Hashin and Tsai-Wu failure criteria. The various material degradation schemes used with the maximum stress criterion do not influence the progression or the number of matrix cracks. Use of the Hashin criterion results in the prediction of more initial cracking, but a very similar crack count and progression scenario as the pressure increases. Use of the TsaiWu criterion results in the same crack progression scenario, but more cracks.