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Polymer Reinforced DNAN/RDX Energetic Composites: Interfacial Interactions and Mechanical Properties

Qian W., Chen X., Luo G.

Central European Journal of Energetic Materials

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2017

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Vol. 14, no. 3

726--741

EN

2,4-Dinitroanisole (DNAN) has excellent properties as a replacement for 1,3,5-trinitrotoluene (TNT) in melt-cast explosives, and the polymeric modifier used is critical to the mechanical modification of the DNAN/RDX energetic composite. In our research, the typical polymeric modifier acrolein-pentaerythritol resin (APER) was successfully added experimentally to the DNAN/RDX system, and the effects of interfacial interactions on the mechanical properties of these polymers in reinforcing the DNAN/RDX energetic composites were investigated by molecular dynamics simulations, scanning electron microscopy (SEM) and mechanical testing. The results showed that strong attractive interactions exist between the polymer and the explosives, wherein van der Waals forces were found to play the main role. The morphological micro-images also showed tight binding between the polymer/explosive interfaces, which supported the calculated strong interfacial interactions. The mechanical tests confirmed that adding the polymers can obviously reinforce the mechanical strength and toughness of DNAN/RDX systems. The above observations revealed that the cooperative effects of the APER polymer can help to reinforce the interfacial interactions and mechanical properties of DNAN/RDX composites, which is of importance in the formulation and mechanical evaluation of advanced energetic composites.

2

The Reinforcement of the TNT System by a Newly-designed GAP-based Polyurethane-Urea: a Molecular Simulation Investigation

Qian W., Shu Y., Ma Q., Li H., Wang S., Chen X.

Central European Journal of Energetic Materials

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2016

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Vol. 13, no. 2

411--426

EN

A glycidyl azide (GAP)-based polyurethane-urea (PUU) modifier used in the 1,3,5-trinitrotoluene (TNT)-based composite explosive was investigated by molecular simulation. Inter-molecular interactions were investigated using quantum chemistry calculation on the dimer of TNT and GAP-PUU, and attractive forces were found between the two molecules. The cohesive energy densities and the solubility parameters were obtained through molecular dynamics simulations combined with thermodynamic calculations on the TNT and GAP-PUU amorphous cell models, and the miscibility of the modifier in molten TNT was predicted to be good. The interaction energies and the mechanical properties were then obtained by molecular simulations and mechanical calculations on the solid-phase models of the GAP-PUU with TNT along three crystalline directions, and an improvement in the mechanical properties was predicted.

3

Thermal Expansion of Explosive Molecular Crystals: Anisotropy and Molecular Stacking

Qian W., Zhang C., Xiong Y., Zong H., Zhang W., Shu Y.

Central European Journal of Energetic Materials

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2014

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Vol. 11, no. 1

59--81

EN

Molecular dynamics simulations of three typical explosive crystals, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), 1,1-diamino-2,2- dinitroethene (FOX-7) and 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), were carried out under NPT ensemble and selected force field. The equilibrium structures at elevated temperatures were obtained, which show that the stacking behaviour of the molecules does not change with temperature. The coefficient of thermal expansion (CTE) values were calculated by linear fitting methods, and the results show that the CTE values are close to the experimental results and are anisotropic. The total energies of the cells expanding along each single crystallographic axis were calculated by the periodic density functional theory method, indicating that the energy change rates are anisotropic, and correlation equations of the energy change vs. CTE values were established. The essence of the anisotropy of the explosive crystal’s thermal expansion was compared and elucidated.

4

An improved two-stage estimator in a partly linear model.

Qian W., Mammitzsch V.

Badania Operacyjne i Decyzje

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2000

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Nr 3-4

91-116

EN

Consider the partly linear model y/sub i/=x/sub i//sup T/ beta +g(t/sub i/)+e/sub i/, 1[left angle bracket]or=i[left angle bracket]or=n Chai et al. (1995) suggested a two-stage estimator of beta . In this paper, an improved two-stage estimator beta /sub n/ of beta and an estimator g(.) of the unknown function g(.) are established. The strong consistency and consistency rate of beta /sub n/ to beta is given and the asymptotic normality of beta /sub n/ is studied. We also obtain the optimal uniform convergence rate of g/sub n/ to g under rather weak assumptions.

PL

Rozpatrzono model częściowo liniowy y1=xTi B + g(ti) + ei, 1<=I<=n, zamieszczony w pracy Chai G.X. i współautorów (1995), w którym sugerowano zastosowanie dwustopniowego estymatora parametru B. Zaproponowano poprawiony dwustopniowy estymator Bn parametru B, a także estymator gn(.) nieznanej funkcji g(.). Wykazano silną zgodność, a także stopień zbieżności estymatora Bn z B oraz asymptotyczną normalność estymatorów Bn. Uzyskano ponadto optymalny stopień jednostajnej zbieżności gn do g przy bardzo słabych założeniach.