Burst Failure Analysis Of Composite Wound Cylinder Considering The Influence Of Fiber Crossover And Undulation

In order to promote the upgrading of energy system,hydrogen energy has been widely concerned as an efficient and low-carbon secondary clean energy.The hydrogen storage vessel,which is the core component for hydrogen energy storage and transportation,has developed from type I(the all metal cylinder)to type III and type IV(the filament-fully wapped composite cylinders).The storage density and reliability of the hydrogen tank has been greatly improved.Burst pressure is the primary parameter to evaluate the safety of filament-wound composite cylinders.At present,burst pressure of the filament-wound composite cylinders is commonly predicted based on the traditional laminated plate model,where the impact of fiber crossover and undulation are not taken into account.As a result,it’s difficult to evaluate the influence of winding structural characteristics on the burst pressure of filament-wound composite cylinders,and large numbers of physical tests are needed to determine the strength reduction coefficient of winding layer.To address the problem,the influence of the crossover and undulation characteristics of fiber bundles on the bearing capacity of the winding structure are studied in this paper by the combination of finite element simulation and experimental method,the improved design method for filament-wound composite cylinders and the prediction method of burst pressure based on finite element model are proposed.The specific research works and main results are as follows:Firstly,a mesoscale finite element model,which takes into account of the crossundulating morphological characteristics of fiber bundles,was developed.In this model,3D Hashin failure criterion was used to predict the damage initiation,the energy-based damage evolution criterion was adopted to describe the failure process,and the nonlinear shear behavior of materials was also considered.Based on this model,the bearing capacity of filament-wound flat plate was analyzed under uniaxial tensile load.The differences of the global and local deformation characteristics between wound structure and laminated structure were compared and discussed.And the influences of fiber crossover and undulation on the bearing capacity of the structure were explored.At the same time,physical tensile tests of the wound plate were carried out.Evolutions of the strain field were monitored by digital image correlation(DIC)technology during loading process,and were used to compare with the finite element analysis.It is shown that the simulated results are in good agreement with the experimental ones.Compared with the laminated structure,the wound structure gives a lower apparent stiffness.There is obvious strain concentration in the fiber crossover area,which is mainly caused by the resin enrichment and fiber fluctuation in the wound area.The finite element model created in this paper can effectively capture the strain concentration and related mechanical behavior characteristics in the fiber crossover and undulating region,and can be used to analyze the influence of the cross-undulating characteristics of fiber bundles on the bearing capacity of winding structures.Based on the mesoscale detailed fiber winding finite element model created in this paper,according to the structural characteristics of the helical wound layer of the filament-wound cylinder,the failure behaviors of wound structure and laminated structure under uniaxial tensile load along the fiber direction were analyzed,and the reduction coefficient of fiber strength for helical wound layer was determined.Afterwards,filament-wound composite cylinders were designed and manufactured based on the strength reduction coefficient of the helical wound layer,and the burst pressures of the cylinder were predicted and verified by experiment.It is found that the error between simulation results and burst test results is reduced from about +10% to about-4% by application of the reduction coefficient proposed here.The burst pressure prediction method based on the detailed model corrected strength proposed in this paper has given a higher predicting accuracy,and the subsquent layup design scheme is prefer to safety for engineering applications.