Numerical and experimental investigations of low-velocity impact on composite overwrapped pressure vessel with different stacking sequences

Composite overwrapped pressure vessels are designed to contain fluids that operate under high pressures. In addition to internal pressure, the design needs to account for out-of-plane loading in the form of low-velocity impact. In this study, a numerical analysis of four models of composite overwrapped pressure vessels with different stacking sequences is performed. A three-dimensional explicit finite element model using multi-layer stacked shell elements was used in the impact zone region to obtain reasonable computation time. Utilizing the bilinear traction-separation law, cohesive zone elements were used to simulate the delamination failure and as bonding between eight layers of CFRP covering the aluminum liner. The simulation results were then validated using drop-weight impact tests, which revealed that the response of contact force to impact time was comparable for both types of analysis. Prediction of failure was carried out by assessing the quantity of energy absorbed by the CFRP layers and was confirmed by shell element data that failed during simulations. In addition, the Hashin damage model confirmed that the matrix tensile failure mode was the predominant failure mode for all discussed impact scenarios. Model-A with Al + [90]8 stacking sequence was found to have the highest impact resistance based on the prediction of the composite's failure area and the energy absorbed by the CFRP layers. Furthermore, it was found that COPVs with combinations of helical and hoop sequences tend to have larger areas of delamination due to high interlaminar shear stress between the CFRP layers.