Finite-element Analysis of Composite Pressure Vessels with Progressive Degradation

A degradation model incorporated into the finite-element analysis of the pressure vessel,based on a progressive failure criterion, has been discussed. A stiffness reduction scheme forthe failed laminas has been implemented using package ANSYS along with a reduction in thestrength of the composite (on its undegraded strength after a substantial degradation of itsconstituents). The degradation model used for analysis is sensitive to the mesh and the loadstep size. Computational efficiency (CPU time) of the finite-element model is very importantin the degradation study, and accordingly, equilibrium is not re-established in the nonlinearsolution procedure implemented in ANSYS (single-frame restart analysis). This is offset usinga small load step size for the degradation studies of the pressure vessel.The model is qualified by a comparison with deformation measurements obtained fromhydrostatic tests. The experimental deformations have an excellent match with the degradedmodel in comparison to the undegraded model. The redistribution of stresses in the compositeconstituents as a result of degradation, has been demonstrated. The burst in the pressure vesselis indicated by unusually large displacement and infeasible stress profile in consequence to asubstantial degradation in the fibre material of the composite