| Mulitifunctional Energetic Structural Materials (MESMs) are evolving as a new class of mixture which usually including thermites, intermetallics, metal-polymer mixture, metastable intermolecular composites. As the MESMs could provide dual functions of structural strength and energy release characteristics under intensive shock loading, there is a promising application in both efficient damage and protection field. The shock-induced chemical reaction (SICR) behavior of MESMs is significantly influnced by their mesostructure. During the shock compression process, particles of MESMs collide with each other, followed by temperature rising in the surface interface, hot spot formed and reaction initiation. Therefore, chemical reaction is controlled by the mesoscale characteristics, such as the mean particle size, the variation in particle size, shape and distribution of the particles. In this work, such a complex shock compression problem that refers the spatial from mesoscale to macroscale and couple thermal-mechanical-chemical response is investigated. Al/W/PTFE which is typical MESMs is seleted and mesoscale numerical simulation, theoretical analysis and experimental research are used to conducted on such the problem. The main contents could be summaried as follows:(1) Based on the multi-components with porosities mixtures characteristics of MESMs, the shock equation of state for MESMs and temperature controlled shock-induced chemical model were been investigated.In order to analyze the dynamic behaviour and temperature rise of MESMs, an equation of state for multi-components with porosities was developed by combining the equation of state for solid, cold energy mixture theory and Wu-Jing model. Then, the temperature rise under shock compression is calculated from isobaric path incorporate with thermodynamic relations, in which the contribution of free electrons was considered. Finally, the Arrhenius reaction rate and Avrami-Erofeev kinetic models that are controlled by shock temperature are used to calculate the extent of reaction of MESMs. A thermochemical model for shock-induced reactions, which includes the reaction efficiency, is given by combining shock temperature rise with chemical reaction kineties. Theoretical calculations are compared with experimental results for several typical MESMs.(2) According to the mesoscale distribution characterstics of MESMs, a method which could generate the mesoscale model of MESMs following the real mesoscale distribution was developed.Based on the mesoscale structural characteristics of the particles metal materials, several control parameters including particle shape, particle size and particle position were introduced to describe its meso-scale characteristics. Methods as random number generation method, intelligent optimization algorithm and relevant constraint were adopted, for the purpose of making the simulation model gradually approaching to the real particle distribution in meso-scale. It shows that the randomly generated simulation model which meets the statistical laws could reproduce the distribution of real particles. With the method, mesoscale model of Al/W/PTFE with different schemes were generated.(3) Based on the multi-materials Euler algorithm, the shock compression response of typical MESM were been investigated in mesoscale.By exploiting AUTODYN FEM software, after appropriate algorithm, material model, boundary and loading conditions were selected and loading, the shock compression of MESMs in mesoscale were simulated without considering the chemical reaction. Typical MESMs (Al/W/PTFE) was selected to investigate the effect of material component and particle size on the Hugoniot parameters and thermodynamic response under shock compression. The results show that the Al/W/PTFE material component ratio, particle size size to a large extent influence the impact of compression the Hugoniot parameters as well as the thermodynamic response.(4) The shock compression response of MESMs in mesoscale was associated with the shock reactions model in macroscale by consider the thermodynamic response from simulation as an input parameters.The shock compression responses of MESMs in mesoscale were incorporated with the shock-induced chemical reaction model in macroscale by multiscale method. Therefore, the shock compression responses were extent to themo-mechanic-chemical response. And the shock reaction results under different shock velocity, material component ratio, particle size were obtained.(5) The shock compression response of MESMs under different material component ratio, and particle size were investigated by experimental verification.Molding and sintering process were used to manufacture the Al/W/PTFE speciments with different material component ratio and particle size. Then, quasi-static and low-speed dynamich shock compression experiments were conducted on the speciments, the effect on the strength was acquired from strain-stress curve. Post-shock microstructural analysis of recovered material with SEM and comparison of calculated and measured product states is used to establish the criterion for reaction occurring in different granular or mesostructure characteristics At the same time the hypervelocity flyer plate impact experiment was carried out to investigate the reaction response of typical MESMs and time resolved stress measurement (using PVDF gauges) which is to be used to determine the shock state. |
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