Research On The Dynamic Response Of Single-layer And Multi-layer Plates Under Confined Blast Loading

From the view of statistics of actual combats and target tests,the semi-armor-piercing missile has been the major threat to the surface vessel,due to its outstanding ability in striking distance,defense penetration ability and destructive force.The confined blast load from explosion of warhead in the cabin has been a major consideration in the design of blast-resistant structures of the surface vessel,which also attracts a massive amount of attention from researchers.Recently,with the development of materials science and manufacturing technology,metal and fiber reinforced composites are combined to form a new hybrid structure,which is called ‘fiber metal laminates’ and abbreviated as FMLs.It is found that the damage tolerance of FMLs structures has been improved greatly compared to that of monolithic metal and fiber reinforced composite.It has a wide application prospect in the field of ship engineering due to its light-weight,high specific strength,high specific stiffness,excellent performance in fatigue resistance and impact resistance.The combination use of traditional metal plate structures and novel composite structures is an important developing direction of the ship structures in the future.From various demands in the damage research of ship structure under confined blast load and design of blast-resistant structures,experimental test,numerical simulation and theoretical analysis have been conducted in this thesis to study the dynamic response of the typical basic unit of ship structures under confined blast load,which refers to thin metal plate,stiffened metal plate and fiber metal laminate.With regard to the dynamic response of thin and stiffened metal plate under confined blast load,experimental tests are firstly carried out to investigate the behaviors of metal plates with different types of reinforcement under confined blast load.Then,the numerical simulations of experimental tests are carried out by means of nonlinear FEM software.Firstly,the accuracy of numerical simulation method in evaluating the confined blast load and structural response is validated by comparing the experimental and numerical results.Then,the influences of the boundary condition,strain rate,mass ratio of stiffeners and the size of opening on the dynamic response of metal plates under confined blast load are studied numerically.The loading from a confined blast,which consists of the initial shock wave,the several reflected waves and long duration quasi-static pressure,is close related to the confined space and is influenced by the interaction effect between the blast load and structures.It results in a great difficulty in the evaluation of damage effect on structures from the confined blast load.In present thesis,numerical studies have been carried out to investigate the characteristics of the confined blast load.Then,a simplified method for predicting the confined blast load is proposed.The parameters of the simplified blast load is also determined,which can be used to provide accurate input load to structural dynamic response analysis.With consideration of the influence of bend and membrane force,a theoretical model is developed to analyze the elastic-plastic deformation of metal plates under confined blast load.By comparing the theoretical results to numerical results,the accuracy and effectiveness of the theoretical model are verified.On the basis of dimensional analysis,a new dimensionless damage number is proposed for the deformation prediction of plates in cubic cabin under confined blast load.The main influence factors of structural response are considered in the new dimensionless damage number,and each parameter in it can be easily obtained in the process of actual application.Through analysis of the experimental results in the related references,it shows a clear linear relationship between the mid-point deflection-thickness ratio and the new dimensionless damage number.By introducing the shape influence factor,the modified dimensionless damage number is also proposed to evaluate the deformation of plates in the confined cuboid cabin under confined blast load.Based on the new dimensionless damage number,an empirical expression with good correlation is presented for deformation prediction of plates under confined blast load.The reasonability of the new dimensionless damage number and the empirical expression for deformation prediction is verified through the comparison between the results of numerical simulations and the empirical expression.The numerical calculation method is used to investigate the dynamic response of multi-layered metal plates under confined blast load.The deformation mode,strain distribution and deformation energy of the multi-layered metal plates are obtained in the numerical simulations.Besides,a comparison analysis is conducted between the dynamic responses of the multi-layered metal plate and the single layered metal plate with same areal density.In addition,numerical simulations are carried out to further investigate the influence of the number of layers and the standoff distance on the dynamic response of the multi-layered and the single layered metal plate,which can provide references to the design of the protective bulkhead of the surface vessel.Experimental tests are carried out to investigate the dynamic response of thermo-plastic fiber metal laminates(TFMLs)under confined blast load.Based on the experimental results and the new dimensionless damage number,empirical expressions are proposed for the deformation prediction of the front face and the back face of the novel fiber metal laminates.Besides,based on the Hashin’s 3D failure criteria,a vectorized user material subroutine(VUMAT)is developed to define the mechanical constitutive behavior,the damage initiation and the growth of subsequent damage in each direction of the fiber reinforced composites.It also incorporates the effect of strain rate on the damage initiation.The subroutine is implemented into the commercial finite element code ABAQUS/Explicit,then the numerical calculation method is developed to model the deformation and failure mechanisms in the novel fiber metal laminates under confined blast load.Numerical simulations are carried out to investigate the dynamic response of fiber metal laminates in the experimental tests.Good agreement is obtained between the measured experimental and numerical displacements.The dynamic response process and failure distribution of the fiber reinforced composite in the TFMLs are also obtained in the numerical simulations.In addition,the comparison analysis is carried out between the anti-blast performances of the novel fiber metal laminate and the monolithic metal plate with same areal density.