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In order to investigate the thermal decomposition kinetics and mechanism of nitrocellulose (NC) based nitramine explosives nanocomposite energetic materials, this work prepares NC/RDX (cyclotrimethylenetrinitramine), NC/HMX (cyclotetramethylenetetranitramine), and NC/CL-20 (hexanitrohexaazaisowurtzitane) composites by a combined sol-gel and the freeze-drying technology. The structure is systematically investigated and the results reveal that the explosive particles are dispersed, filled, or embedded homogenously in the gel matrix of NC, thereby restricting the crystal growth of RDX, HMX, CL-20 particles to coarse and achieving submicron/nanometer. The thermal analysis of composites exhibits much lower peak temperature compared with raw explosive crystal, furthermore, the activation energy (E a ) of composites is also lower than that of both NC and explosives. Hence, the unique structure of NC gel matrix embedded explosives inside demonstrated different mechanism of decomposition. Concretely, the rupture of the H-NCO = O bond in the cross-linked structure is detected firstly, subsequently, the macromolecular chains' scission site of gel firstly occurs at -C-O-C-in the ring, and then the scission of -NO 2 (from NC or explosive crystals) bonds happened. Hence, this study may provide promising fabrication strategy and basic theory for the application of NC-based nanocomposite energetics in high-energy propellants and explosives.

To take full advantage of the additive manufacturing technology, an integrated and efficient approach of complex geometry gun propellant form function calculation and geometry optimization design based on Grasshopper (GH) software was proposed as a first attempt to obtain the closed-loop of geometric optimization forward design with performance as the goal and algorithm as the means. The burning surface regression simulation and form function calculation of the entire multi-perforation gun propellant family, multi-perforation web thickness uneven gun propellant family, mixed gun propellant charges were demonstrated by using the parametric model of GH software. With the highest combustion progressivity as the optimization objective, the genetic algorithm in GH software was used to geometrically optimize the parametric model of multi-perforation gun propellant family, and then the en-tire multi-perforation with ball gun propellant family was obtained. The closed vessel test result showed that the form function calculated by the GH approach was in better agreement with the test curve than that of the analytic method. The integral form function of the mixed gun propellant charges was calculated firstly and proved by the interior ballistic performance calculation. The combustion progressivity of rosette-shaped 19-perf with ball gun propellant was significantly improved compared with that before geometry optimization, with the ball-tube, ball-ball, and ball-ball-ball structure increasing by about 15.0 %, 17.7 %, and 17.7 %, respectively. The integrated and efficient approach was dynamically visualized in real-time and required no learning of conventional scripting-type programming, providing the basis for the design and application of gun propellant with any complex geometry.

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