Numerical investigation of pre-flawed FGM tubes repaired with different composite jackets under sequential gaseous detonation loading

• Stress analyses of cracked FGM tubes repaired with composite jackets/patches under internal moving pressure using finite element method. • Different loading types and FGM materials are defined to assess the effect of material orientation on the tube response. • Sequential moving pressure (with five cycles) are modeled to analyze stress oscillation with time. • Delamination analyses of different composite patches are done for all the FGM tubes. • Results show the effect of each FGM tube and effect of different loadings on the final repaired tube response. Investigation on the structural response of pre-flawed functionally graded material (FGM) cylindrical tubes submitted to sequential detonation loading is the main contribution of this study. Analyses are made for repaired and unrepaired tubes using three different composite patch (CP) geometric shapes: full cylindrical, semi-cylindrical, and circular. The effect of non-homogeneous FGM materials (ceramic-to-aluminum, aluminum-to-ceramic, and steel-to-ceramic) and CPs on the stress field in the tube is studied using three-dimensional finite element (FE) models. The FE analyses are conducted for two distinct categories of detonation loading: low- and high-pressure detonations. This approach helps to enhance the understanding of how material gradation influences stress distribution and damage assessment in tubes subjected to these specific loading conditions. The FE analyses revealed that both forward and reflective waves coming from detonation load significantly contribute to crack propagation by elevating stresses near crack tips. The application of CPs, made of boron/epoxy material, effectively mitigated stress concentrations across all FGMs, with full cylindrical CPs providing the best results. Delamination was observed in CPs with two composite layers under high-pressure loading, particularly in aluminum-to-ceramic FGM. Graphical abstract