Molecular Dynamics Simulation Study On The Structure And Properties Of CL-20 And Their Composite Materials

CL-20(hexaisowurtzitane,HNIW)is by far recognized as the most powerful compound explosive,but its sensitivity is high. In this thesis, molecular dynamics were employed to explore the structure,energetic and mechanical properties and their relationships in detail for CL-20 and its based polymer bonded explosives(PBXs).Firstly, to provide reference for follow-up researches on ε-CL-20 based composite materials,comparative studies were performed for ε-CL-20 crystal with different crystalline surfaces.Then several ε-CL-20/polyvinyl alcohol(PVA) models were simulated,in which any one of the models has different numbers of molecular chain,but all of them have the same repeating unit numbers.The simulating results show that in this situation the length of molecularchain has almost no effect on the explosive crystal.The results are beneficial to set upappropriate simulation models.On the above research basement,as an adhesive,PVA and poly(ethylene glycol)(PEG) separately make up three PBXs models with s-CL-20 crystalline surfaces(001),(110)and(020).Comparing with ε-CL-20/PVA PBX,the ε-CL-20/PEG is more insensitive and has better ductibility. In this thesis, ε-CL-20/grapheme(GE) PBX model was also set up.and was simulated at 195K,245K,295K,345K and 395K by MD.The results show that, with increasing temperature, the maximum bond lengthof the N-N trigger bond(Lmax) increases monotonously,and the cohesive energy density(CED) and the interaction energy between two boned by trigger bond N-NO2(EN-N) all decreased monotonously.These results are in accordance with increasing temperature.And the elastic properties of ε-CL-20/GE were calculated by fluctuation method and found that the tensile modulus, bulk modulus and shear modulus all decrease with increasing temperature.Finally, to explore and compare the properties of ε-CL-20 based PBXs with stearic acid(SA), ethylene-vinyl acetate copolymer(EVA) and butadiene rubber (BR), respeactively,on condition that every weight percentage of the three adhesive was about 5%,the three PBX models with SA, EVA and BR were built up and simulated by MD. The results the order of stability and safety is:s-CL-20/BR>s-CL-20/EVA>ε-CL-20/SA. And small amount of these adhesives can improve the mechanical properties of ε-CL-20 crystal.