Response Characteristics Of Ship Foam Sandwich Structure Subjected To Near-field Underwater Explosive Loading

With the rapid development of military technology and the increasingly serious regional conflicts,the probability of warships being threatened by underwater weapons is increasing.Ship protection subjected underwater explosion put forward more rigorous requirements.Foam sandwich structure with high strength,stiffness and excellent impact protection performance,in the field of engineering and academic research have been a high concern.At present,most of the research on the dynamic response of the sandwich structure focuses on the areas of air blasting and high-speed impact,while less research focus on underwater explosions.And the methods of response to underwater explosion are limited to acoustic-mechanical coupling and plane-wave loading,furthermore the coupling between structure and fluid is not considered enough.In this paper,ALE numerical simulation method of LS-DYNA finite element software was used to directly simulate the underwater blast shock wave load by using JWL equation of state.In consideration of the mutual coupling between structure and fluid,a multi-chamber of foam sandwich structure protective performance has been studied.Firstly,the response characteristics of sandwich panels by underwater explosion load has been studied.Foam sandwich panel has excellent protection characteristics,for that the deflection of the rear panel reduced by about 25% compared with the front panel.While structure energy absorption process showed a multi-stage,which can be divided into rapid uplift,slight oscillation,stable rise and slightly down four stages.Furthermore,the response characteristics of sandwich panels with real outer hull plating were simulated.Compared with the pattern of backwaters,the backside empty sandwich panels can increase the energy absorption and reduce the transmission energy of shockwaves.Secondly,the influence of structural parameters on the response characteristics with regularity of foam sandwich panels has been studied.In this paper,the deformation and energy absorption of foam sandwich structure as the basis of structural protection capabilities.The foam relative density,core height,density gradient,panel thickness and the proportion impact influences have been studied.Results shows that the shock wave transmission in multi-layered medium,the stiffness of the structure and the dynamic response mode are the main reasons for the difference in the deformation and energy absorption of the sandwich structure.Finally,the influence of various parameters on foam sandwich structure provide the protective design guidance.Then,in further evaluation of the protective ability of the sandwich structure,it was found that most of the studies mainly refer to deformation and energy absorption,and do not consider the impact of inertial force on equipment and person.In order to evaluate the protective performance of the sandwich panel in all aspects,this paper used the shock response spectrum method process the acceleration signal.Then used the peak value of the spectral velocity as the criterion for the structural protection.Finally,the impact protection of foam sandwich shipboard structure in underwater contact and explosion process has been studied.The research on the protective capability of the foam sandwich side structure has been carried out,from the aspects of structure deformation,damage,energy absorption and so on.It was found that the foam sandwich shipboard structure has a superior capability of resisting deformation and impact.The main protective vertical bulkhead used foam sandwich structure deformed about 14% less than the single structure.