Research On Non-geodesic Winding And Strength Analysis Of Composite Pressure Vessels

With the development of filament winding technology,high-performance and lightweight filament wound composite structures are widely used in various industries.During the winding process,the fiber slippage and non-full-coverage will reduce the mechanical properties of the products,which have been neglected by most researchers.This leads to the difference between the theoretically predicted strengths and the experimental values.At present,most design of filament winding process can not simultaneously satisfy the demands of windability and uniformly full coverage for the given structural size.The winding angles are determined by the polar radius and the stable winding equation with the using of the netting theory to design the winding pattern of pressure vessels.The turn-around angles are determined by the feed eye moved back and forth,producing the fibers which cover the mandrel overlapping and leaving seam because the fibers cannot strictly partition the distance of a fiber band width after winding a complete cycle.It is an effective way to solve this problem by exploring a new winding theory which is able to satisfy both windability and uniformly full coverage for the given product size.In this thesis,a composite pressure vessel was considered as the object.Based on satisfying both windability and uniformly full coverage for the given product size,the non-geodesic winding patterns were studied.Firstly the winding parameters to meet the process requirements were determined and the finite element models according to winding parameters were established.Then the strength of pressure vessels were analyzed and the filament-winding vessel was tested.Finally,the accuracy of winding-pattern design and structural analysis considering manufacturability was verified.The main contents are concluded as follows:(1)The structural models of the primary structure and strength criterion of composite materials were explored to provide the theoretical basis for structural analysis.The netting theory was studied for the cylindrical and domed sections of pressure vessels.The limitations of mechanical analysis based on grids theory were analyzed.(2)The optimal match of the composite material system T800/EW-60 D was selected from a collection of combinations among T700,T800 carbon fibers and three epoxy resins.The mechanical properties of fabricated one-way plate was tested.(3)In order to solve the process parameters which satisfies the conditions of windability and uniformly full coverage under the given product size,the filament winding pattern was studied.The 2nd-order non-linear equation of the central angle of fiber trajectories was derived.Under the given product size,the corresponding relation among the winding angle,the slippage coefficient,and the turn-around angle were calculated,and the winding parameters for ensuring winding stability were determined.The winding parameters of uniformly full coverage were solved using the internal penalty function method.Considering the fiber band width,the winding process was simulated and the winding patterns were presented.The influence of yarn width and the number of the partition point on the winding patterns were studied.The feed eye paths and the turn-around angles of the mandrel were calculated by transformation method of dynamic and static coordinates.The changes in the feed eye path and the turn-around angles were outlined when the winding parameters and the hanging-yarn length were changed.(4)The finite element model was established according to the process parameters of the winding process.The stresses of the pressure vessel under the internal pressure of 30 MPa was determined and the burst pressure was predicted to be89.1MPa.The 5-axis numerically controlled winding machine was used for actual winding and the fibers were arranged in a regular and uniform way.The fiber slippage was not observed.After curing,the burst pressure was 85 MPa,and the difference between the experimental values and the theoretically predicted value was 4.82%.Therefore,the experimental results were in good agreement with the simulated results.Non-geodesic theory which satisfies both windability and uniformly full coverage under the given product size was proposed in this paper and the predicted burst strength of the non-geodesics-based product agreed well with the experimental values.It was demonstrated the theories and methods for designing non-geodesic winding patterns considering the manufacturability were accurate.The strength analysis considering winding process was also reliable.This thesis offers a basic foundation for the production of high-performance and high-level filament wound products.