Explosive Performanc And Mechanical Properties Of Aluminum Fiber Explosive

Traditionally, aluminum is incorporated in the composite explosives in the form of powder, which is expected to result in improving the blast performance of composite explosives due to superior heat of formation. However, impact sensitivity is improved owing to aluminum powder becomes hot spots in composite explosives. In addition, aluminum particle size ranges from nanometer to micrometer, which may lead to the problems of environmental pollution, complex production process, and dust explosion during the production process. The activity of aluminum powder decreases with an increase in storage time because the specific surface area of aluminum powder. Explosives is subjected to all kinds of loading under different environment, such as productive process, packing, handing, transportation, launch, and so on. Mechanical properties of explosives become increasingly significant. A new non-ideal composite explosive is proposed by replacing aluminum powder in traditional aluminized explosives with aluminum fiber. The disadvantage of traditional aluminized explosives may be solved by using aluminum fiber in composite explosive and the better mechanical properties may be obtained because aluminum fiber is used in the new composite explosive. It is helpful to understand the detonation mechanism of traditional aluminized explosives by the study of aluminum fiber explosive.The pressure history curves of aluminum fiber explosive and traditional aluminized explosives are measured by air blast experiments and the curves are analyzed by wavelet analysis. The results show that the decomposition levels have a great effect on the signal to noise ratio after denoising and the wavelet kernel function has less effect on the signal to noise ratio after denoising. Based on the comprehensive judgment of signal to noise ratio, root mean square error and denoising effect, the signals of pressure are processed by db4of Daubechies wavelet series. Details of shock wave signal in each frequency band can be obtained by the wavelet analysis. There are periodic interference signal in d4(781kHz to1562kHz) and three obvious mutation signals, the incident shock wave, secondary shock wave and the reflected shock wave, in d9and dl2. The energy of air blast shock wave is mainly distributed in the0-8e5Hz, which could provide a reference for filter. The amplitude and occurring time of secondary shock wave of aluminum fiber explosive as same as traditional aluminized explosives and the occurring time of secondary shock wave of aluminum fiber explosive is earlier than matrix explosives (RDX), which shows that the amplitude and occurring time of secondary shock wave is associated with the types of explosive. The shockwave impulse of aluminum fiber explosive is close to that of the traditional aluminized explosive. Compare with RDX, the impulse of aluminum fiber explosive increase by18%.The pressure-time curves for the shock wave and bubble pulse of aluminum fiber explosives and traditional aluminized explosives are measured by underwater explosion experiments. The peak pressure, impulse, shock wave energy and bubble energy are obtained by analyzing the curves. The peak pressure, impulse and shock wave energy of aluminum fiber explosive are close to that of traditional aluminized explosives. The detonation velocity and bubble energy of aluminum fiber explosive are greater than that of traditional aluminized explosives. Compare with RDX, the shock wave impulse of aluminum fiber explosive increase by14%-21%. The first pulsation period of aluminum fiber explosive is close to that of traditional aluminized explosives, but the peak pressure and impulse of bubble pulse are lower than that of traditional aluminized explosives. The low content aluminum fiber has less effect on the peak pressure of aluminum fiber explosives, but the high content aluminum fiber has a significant effect on the peak pressure. Detonation velocities of aluminum fiber explosives are decreased with an increase of Al fiber contents. It indicates that the potential of secondary reaction of aluminum fiber and detonation products does not support the detonation propagation. The first pulsation period and bubble pulse of aluminum fiber explosive are increased with an increase of Al fiber contents. The peak pressure and impulse of bubble pulse are reduced with an increase of Al fiber contents. The shock wave energy of aluminum fiber explosive increased firstly and then decreased with an increase of Al fiber contents. The specific shock energy of aluminum fiber explosive is maximum when the content of aluminum fiber is20%.The mechanics experiment of aluminum fiber explosive was carried out by MTS and SHPB. The analysis of experimental results shows that the ultimate stress and residual strength of aluminum fiber explosive are increased with an increase of Al fiber contents. The reinforcement coefficient is8.19, which obtained by fitting experimental data of elastic modulus. The fitting effect on experimental data is satisfactory. The coefficient shows that the enhanced effect of aluminum fiber on RDX is marked. The loading time of SHPB is extended by pulse shaping technique, which ensures the dynamic stress equilibrium in the specimen and to obtain a constant strain rate. The shaping technique could improve the quality of the incident wave and reduce dispersion effects of stress waves. The ultimate stresses of aluminum fiber explosives are related to strain rate by the analysis of experimental results. The relationship of ultimate stresses and strain rate is weakened with an increase of Al fiber contents. The normal distribution function is taken to fit stress strain curves of aluminum fiber explosive in a quasi-static state. The aluminum fiber explosive is destroyed under shock loading when the aluminum fiber contents below20%and the aluminum fiber explosive keep integrity under shock loading when the aluminum fiber contents more than20%. It indicates that aluminum fiber explosive has anti-overload ability.SPH-FEM coupled method could overcome the problem of mesh distortion and improve computational efficiency. The model (SPH-FEM) of underwater explosion is established by MATLAB and LS-DYNA. The region of SPH is a sphere. In order to ensure that the coordinates of particles are agreeing with the grid coordinates of the element on the sphere. The particles of SPH are generated by a new method. The method solves the problem of mesh distortion in the zone of cube tip and penetration of SPH particles to FEM element. After underwater explosion of aluminum fiber explosive was simulated by using the SPH-FEM model, the pressure-time curves of numerical simulation and experiment were compared and the result show that the peak pressure of numerical simulation can match with that of experiment. It indicates that the model of the underwater explosion is presented to testify the validity and precision of SPH-FEM coupled method. The pressure-time curves of aluminum fiber explosive in near-field are obtained by numerical simulation. The decaying exponential function is adopted to fit peak pressure of aluminum fiber explosive at different positions and it is excellent in fitting.