Optimizing The Resistance Of Filament Winding Composite Cylinders Under Hydrostatic Pressure

Underwater vehicle is an important tool in the development and utilization of ocean resource,and is also an important platform for consolidating the national security in coastal defense.For an underwater vehicle operated in deepsea,pressure resistance is an important guarantee to ensure the performance of equipment and personal safety.The requirements of reducing weight,providing buoyancy and increasing load capacity for underwater vehicles,can be easily meet by filament winding composite material which has an excellent specific strength and stiffness.In addition,the danger of being detected by sonar can be reduced while the resistance to corrosion can be increased because the filament winding composite material has excellent sound absorption and non-magnetic properties and is stable against the chemical reaction.Those are of great significance to the life cycle and anti-reconnaissance capability of submersible vehicles.Filament winding composite materials are increasingly used in pressure-resistant structure.The pressure resistance performance of shell structure mainly includes two aspects: stability and strength.For the shell structure,buckling,strength damage,or both may occur.From the perspective of protecting the submersible working ability and personal safety,it has an important application background and practical significance to solve these problems.This thesis investigates the the critical buckling load and instability mode of filament winding composite cylinders with different geometric features and filament winding patterns through theoretical analysis.The failure extension path and the effect of fiber winding angle on layer failure are studied.Considering buckling and material failure,an optimization framework is set up.The resistance performance of filament winding composite cylinder is optimized and metal lining reinforcement method is proposed.The test platform for the shell under hydrostatic pressure is set up and the experimental research is carried out.The main contents and innovations of this study are as follows:(1)The numerical solution solving the critical buckling pressure of filament winding cylindrical shell is extended to mid-thick shell,initiativly.Based on the theory of shell,combined with the anisotropy of filament winding composite,by introducing additional loads,the buckling governing differential equations are derived.According to the boundary condition and buckling mode characteristics,selecting approximation function,the critical buckling load and instability mode are solved.By introducing dimensionless parameters,this thesis studies the influence of shell geometry parameters(D/t and L/D)and filament winding patterns on the stability.The law of critical buckling pressure and buckling mode was obtained.Based on theoretical analysis model,an optimization design is developed to study the influence of the winding patterns on the stability.The framework's efficient and accurate are verified by finite element analysis.(2)Based on the Tsai-Wu failure criterion,a model for judging the strength failure of the fiber-wound cylindrical shell under hydrostatic pressure is established.The deformation of filament winding composite cylinder is studied in the static state and post-buckling state.The resistance performance and the deformation trend of the shell are obtained.According to the first-order buckling mode,the layer failure under the post-buckling is numerically analyzed,by tracking Tsai-Wu coefficient,the effect of the fiber winding angle on layer failure is studied,and the law of failure expansion is summarized.An optimization design is developed to study the influence of fiber winding angle and the number of layers on the failure load.(3)This thesis proposes the imbalance between buckling and strength failure of filament winding composite cylindrical shell,and provides a solution for the first time.An optimization framework is set up.The resistance performance of Carbon/epoxy,Boron/epoxy and Glass/epoxy composites cylinder is optimized,respectively.The effects of fiber winding angle and number of layer on pressure resistance are investigated under different wall thickness.After the optimization,the "Cask Effect" is significantly reduced,and the carrying capacity can meet the requirements of stability and strength.Two enhancement methods of aluminum alloy lining and titanium alloy lining are proposed.The influence of the metal lining on the critical buckling pressure,critical failure pressure and the carrying capacity of filament winding composite cylinders is analyzed,and the reinforcement mechanism is summarized.(4)The test platform was designed and built,and the experiment of carbon fiber cylindrical shell under static condition and blasting condition is carried out.The dynamic strain-displacement analysis system is used to collect the strain and displacement information of the measuring points.The strain response of the carbon fiber composite cylinders,metal control sleeves and different head models are studied.The displacement analysis is carried out to reseaech the deformation feature of the carbon filament winding composite cylindrical shell.The blasting test is carried out to investigate the nonlinear mechanical behavior the composite cylinder and metal control sleeves.The relationship between the nonlinear behavior and the crack propagation path is analyzed.