Strength Analysis Of Composite Sandwich Superstructure

The application of composite materials in ship superstructure can reduce weight,leading to a lower center of gravity and an improvement of stability and speed.Other advantages include sound insulation and stealth capability.Currently,research about composite superstructure on steel hull is still at an initial stage,and it is rare to see public research findings about the deformation law of composite superstructure.Therefore,conducting researches about composite superstructure is of great significance.Firstly,a static loading experiment is conducted,in which hogging bending load is applied to a ship model.The model consists of a steel hull and a superstructure which is made of composite sandwich material with foam core.The experiment model,devices and measuring point layout scheme are introduced in detail.The following results are obtained according to this experiment:strain distributions of the cross sections,strain distribution along the breadth direction of different decks,strain distribution of the interface between composite superstructure and steel hull,and the superstructure effectiveness.Then,a strength analysis of foam core composite sandwich superstructure is performed using finite element method,and such method is verified by comparing the experimental and numerical results.In addition,the differences between experimental result and finite element result of the deck strain distribution are discussed.A study about how material parameters of FRP layer in sandwich structure affects the side wall deformation law is carried out,which indicates that elastic modulus and shear modulus of the FRP layer are the main factors leading to the side wall deformation difference between composite superstructure and steel superstructure.Then,this paper analyzes the deformation of independent superstructure under vertical and horizontal force,discovering that elastic modulus has the same effect on bothσ_{x p}andσ_xq.When the elastic modulus increases,the absolute value ofΔσ_xp orΔσ_xq per unit height will increase.However,the shear modulus has different effects onσ_{x p}andσ_xq.When the shear modulus increases,the absolute value ofΔσ_xp per unit height will increase,while that ofΔσ_xq will decrease.An analysis is made about the superstructure effectiveness,considering both length and material ofthe superstructure.It is found that when the superstructure made of foam core sandwich composite material has the same length as the hull,the bending moment undertaken by the superstructure is less than 10%of the total bending moment.By comparing composite superstructure and steel superstructure with the same structure form,it is found that the material has a great influence on the superstructure’s participating in total longitudinal bending.Meanwhile,the double beam theory is used to analyze two superstructure models（M2-20%and M2-80%）made of foam core sandwich composite material with 20%and 80%of the ship length,and a modified formula of the double beam theory is suggested and compared with the finite element result.