A mechanisms-based fracture model applicable to a broad class of cemented aggregates and, among them, plastic-bonded explosive (PBX) composites, is presented. The model is calibrated for PBX 9502 using the available experimental data under uniaxial compression and tension gathered at various strain rates and temperatures. We show that the model correctly captures inelastic stress-strain responses prior to the load peak and it predicts the post-critical macro-fracture processes, which result from the growth and coalescence of micro-cracks. In our approach, the fracture zone is embedded into elastic matrix and effectively weakens the material's strength along the plane of the dominant fracture
Additive manufacturing (AM) is an attractive approach for the design and fabrication of structures capable of achieving controlled mechanical response of the underlying deformation mechanisms. While there are numerous examples illustrating how the quasi-static mechanical responses of polymer foams have been tailored by additive manufacturing, there is limited understanding of the response of these materials under shockwave compression. Dynamic compression experiments coupled with time-resolved X-ray imaging were performed to obtain insights into the in situ evolution of shockwave coupling to porous, periodic polymer foams. We further demonstrate shock wave modulation or “spatially graded-flow” in shock-driven experiments via the spatial control of layer symmetries afforded by additive manufacturing techniques at the micron scale.
Microstructure-based numerical modeling method for effective permittivity of ceramic/polymer composites J. Appl. Phys. 97, 104104 (2005); 10.1063/1.1897071Finite-element modeling method for the prediction of the complex effective permittivity of two-phase random statistically isotropic heterostructures Abstract. We have used data from image analysis to guide us in creating a finite element mesh of PBX 9501. Information about the binder concentration at different length scales taken from micrographs allows us to create a mesh that naturally incorporates inhomogeneities of the microstructure in a manner that is statistically consistent with the observed microstructure. We then apply constitutive models that are consistent with the different binder concentrations and run finite element simulations. We will present our technique for incorporating the image analysis information into the mesh, our mechanical models, and results of the simulations.
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