Abstract
A nesting ubiquitiform (NU) approach was developed to characterize the mesostructural features of polymer-bonded explosives (PBXs), and then used to predicate some equivalent physical properties of PBXs, which can also be expected to be extended to other composites with complicated internal mesostructures. To verify the availability, two NU models for two kinds of PBX with different compositions are presented, which are PBX 9501 and LX-17, based on which, the equivalent thermal conductivities were calculated. Particularly, it is so encouraging that an analytical expression of the equivalent thermal conductivity was obtained only under a simply assumption of homogeneity. Moreover, it was found that the numerical results calculated by both the recursive algorithm and the analytical expression were in good agreement with the experimental data. In addition, it is also shown that such a physical property as the equivalent thermal conductivity is indeed independent of the meso-configuration of the location distribution of the explosive particles and the voids inside the PBX, which seems consistent with the common expectations and lays the foundations for the application of ubiquitiform to investigating some equivalent properties of composites.
Highlights
Polymer-bonded explosives (PBXs), in which the explosive powder is bound together with the matrix, have been widely used in both the civil and the military engineering applications, due to advantages such as easy shaping and safe machining
The particle size distribution (PSD) of a nesting ubiquitiform (NU) model is a discrete function as Equation (10), which cannot be compared with the continuous PSD of the PBX directly
The parameters in the PSD function for the PBX 9501 used in this study are given by experiment data [21,22], all of them were listed in Table 1, and the subscripts “1”, “2” and “3” represent “the coarse High melting explosive (HMX) particles,” “the fine HMX particles,” and “the voids,” respectively
Summary
Polymer-bonded explosives (PBXs), in which the explosive powder is bound together with the matrix, have been widely used in both the civil and the military engineering applications, due to advantages such as easy shaping and safe machining. To better understand the macroscopic chemical and mechanical behaviors of a PBX, such as its decomposition, combustion, detonation, constitutive behaviors, and so on, it is especially important to characterize its mesostructural features. Since the pioneering work of Mandelbrot [5,6], which introduced an effective nonlinear mathematical tool, fractal has been extensively used in investigating the mesostructure features of various kinds of the quasi-brittle materials, such as concrete [7], rock [8], and soil [9,10]. Carpinteri et al [7] derived the fractal patterns in the tensile failure of concrete specimens from the grain size distributions of the aggregates inside the material, and proposed a fractal cohesive crack model, by which the size-independence of the fracture energy was proven; Katz and Thompson [8].
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