Investigation Of Joint Between Lattice Composite Superstructure And Steel Main Hull And Design

The Conflict and confrontation on Maritime rights and interests in the whole world becomes fierce increasingly,which makes lightweight and stealth performance is more urgent to warship.Composite material is concerned widely by ship domain because of its high specific stiffness and specific strength,excellent electromagnetic performance and corrosion resistance.As a new type of lightweight sandwich composite materials,lattice sandwich materials has an application prospect to build warship for its design feature.However,composite material owns low ductility,which lows the ability of composite joint to redistribute load,likely resulting in partial damage or global damage.Experiences have shown that most damage occurs in the joint structure of composite materials,severely restricting the application and construction of composite in superstructure of warship.Therefore,it is of great military significance to carry out design and optimization of joint between lattice composite superstructure and steel main hull and research of ultimate bearing capacity and damage mechanism of typical joint for application of composite superstructure on warship and large-scale of composite structure.Based on contimuum damage mechanics a three-dimentional finite element model of composite laminate,taking use of progressive damage method,has been established.Hashin strength criterion and Ye delamination criterion are adopted in this FEM model.User material subroutine UMAT has been compiled based on ABAQUS FEM software,which includes the constitutive relationship of composite material,damage initiation criterion and damage evolution criterion.The ultimate bearing capacity of laminate specimens with different stacking sequence and a hole under uniaxial tension/compression and the numerical rusults agree well with the experimental data of the referrence,which verifies the validation of the FEM model.Using a certain type of lightweight steel superstructure as the prototype,numerical analysis method based on CFD is adopted to study the wind load distribution characteristic of the superstructure and the wind load is simplified to circumferential average pressure coefficient for application of engineering.The law of the influence of additional inertia moment of composite superstructure on structural response is researched.The rolling period and the rolling amplitude of warship in the condition of rolling and pitching is deduced according to the current military criterion and the calculation method of inertia load of warship and the load of green water on superstructure is shown.Based on "building block" of composite material structure design,stacking sequence of laminate joint is designed and specimens are manufactured by hand lay-up molding.Two tests,tension test and tension and compression fatigue test,are carried and ultimate bearing capacity and N-S curve of joint is retained.The good consistency of experimental results verify the stability of manufacture technology and the accuracy of the numerical algorithm of progressive damage analysis,which provides support to design lattice joint further.The combination of theoretical research,numerical analysis and experimental verification is used to study the mechanical properties of sandwich plate with lattice core.Based on displacement method,the deformation mechanism is analyzed and the relationship between macro shear stress of sandwich plate and the stress of truss of lattice core and the method of numerical simplification analysis of sandwich plate are deduced as well.The properties of flatwise compression,edgewise compression,shear and bending of sandwich plate are researched by tests and the mechanical parameters are retained,which verifies the accuracy of the numerical algorithm of sandwich plate based on stiffness.Aimed at the joint between sandwich plate with lattice core and steel structure,a modified T-style joint configuration is put forward and the design of joint parameters,the stacking sequence of laminate facesheet in joint region and transition region are carried out.A series of specimens are manufactured to conduct tests and the experimental results have verified the validation of the method of joint design and numerical algrithm,which shows that the joint owns characteristics of simply configuration and high bearing capacity.Finally a method of composite joint design based on "Building lock" is concluded and some improvement approaches and advises are provide to enhance the mechanical properties of joint further.The distribution regularity of deformation and and stess of the joint between composite superstructure and steel main hull is analyzed,which confirms the indicators for performance chesk.Two different kinds of loading programs are presented and the effect of the condition of DOF constraint on the distribution regularity of deformation and stress is investigated as well.Finally the preliminary test program of combination load is adopted through comparison.The research result can be applied to joint design and optimization between composite superstructure made from fiber-reinforced sandwich plate and main hull.