The Carrying Capacity Analysis For COPVs Considering The Manufacturing Techniques

Carbon fiber reinforced plastic (CFRP) laminates were attractive structural materials in aerospace structures because of high specifc stiffness and strength. To achieve radical structural weight reduction of space launch vehicles, application of composite overwrapped pressure vessels (COPVs) had been widely attempted. The carrying capacity of COPVs with metal inner, which is a key factor for structural and personnel security, was a widespread concerned simulation problem. Convincing experimental and simulation results indicated that winding layers of COPVs suffered from matrix crack and delamination, even just under rated pressure. Thus, the damage and corresponding stiffness reduction of winding layers, which bear the majority of pressure, should be considered while calculating the carrying capacity. The mechanical properties and carrying capacity of COPVs strongly depended on processing, for instance, winding tension system, curing system and autofrettage pressure. These processing factors were rarely considered in previous FEM analysis of COPVs.The author employed the Hashin's failure and stiffness reduction criterion to determine the modeling of the gradual failure process to study on the carrying capacity of COPVs, based on user subroutine of ANSYS. The detailed analysis procedure was as follows:firstly, winding tension system and autofrettage pressure were both considered. The stress fields in winding layers were calculated based on thick-wall shell theory. Secondly, Fiber volume fractions of each layer were determined by elastic deformation theory. Mechanical and strength properties of layers were computed employing bridging model. In addition, the best autofrettage pressure was determined by a series of autofrettage loop. Finally, the carrying capacity of COPVs was analyzed considering present winding tension system and autofrettage pressure.