@article{brown_zikry_2015, title={Behaviour of crystalline-amorphous interfaces in energetic aggregates subjected to coupled thermomechanical and laser loading}, volume={471}, ISSN={["1471-2946"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84956865216&partnerID=MN8TOARS}, DOI={10.1098/rspa.2015.0548}, abstractNote={The behaviour of energetic aggregates was investigated for quasi-static compression and high strain rate thermomechanical compression behaviour that is coupled to laser irradiation. A dislocation-density-based crystal plasticity formulation was used to represent energetic crystalline behaviour, a finite viscoelastic formulation was used for the polymer binder and a coupled electromagnetic (EM)–thermomechanical computational scheme was used to predict aggregate response. Aggregates with different crystal sizes were considered to account for physically representative energetic microstructures and to understand the effects of crystal–crystal and crystal–binder interactions. The presence of smaller embedded crystals in the binder ligaments inhibited viscous sliding, and resulted in global hardening of the aggregate, which led to large stress gradients, localized plasticity and dislocation-density accumulation. The embedded crystals also increased scattering of the EM wave within the binder ligaments and increased the localization of EM energy and laser heat generation. Geometrically, necessary dislocation densities and stress gradients were calculated to characterize how hardening at the binder interfaces can lead to strengthening or defect nucleation.}, number={2184}, journal={PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES}, author={Brown, Judith A. and Zikry, M. A.}, year={2015}, month={Dec} } @article{brown_zikry_2016, title={Coupled infrared laser-thermo-mechanical response of RDX-PCTFE energetic aggregates}, volume={57}, ISSN={["1432-0924"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84961114701&partnerID=MN8TOARS}, DOI={10.1007/s00466-015-1241-3}, number={4}, journal={COMPUTATIONAL MECHANICS}, author={Brown, Judith A. and Zikry, M. A.}, year={2016}, month={Apr}, pages={611–628} } @article{brown_zikry_2015, title={Effect of microstructure on the coupled electromagnetic-thermo-mechanical response of cyclotrimethylenetrinitramine-estane energetic aggregates to infrared laser radiation}, volume={118}, ISSN={["1089-7550"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84942532175&partnerID=MN8TOARS}, DOI={10.1063/1.4931379}, abstractNote={The coupled electromagnetic (EM)-thermo-mechanical response of cyclotrimethylenetrinitramine-estane energetic aggregates under laser irradiation and high strain rate loads has been investigated for various aggregate sizes and binder volume fractions. The cyclotrimethylenetrinitramine (RDX) crystals are modeled with a dislocation density-based crystalline plasticity formulation and the estane binder is modeled with finite viscoelasticity through a nonlinear finite element approach that couples EM wave propagation with laser heat absorption, thermal conduction, and inelastic deformation. Material property and local behavior mismatch at the crystal-binder interfaces resulted in geometric scattering of the EM wave, electric field and laser heating localization, high stress gradients, dislocation density, and crystalline shear slip accumulation. Viscous sliding in the binder was another energy dissipation mechanism that reduced stresses in aggregates with thicker binder ligaments and larger binder volume fractions. This investigation indicates the complex interactions between EM waves and mechanical behavior, for accurate predictions of laser irradiation of heterogeneous materials.}, number={12}, journal={JOURNAL OF APPLIED PHYSICS}, author={Brown, Judith A. and Zikry, M. A.}, year={2015}, month={Sep} } @article{brown_labarbera_zikry_2014, title={Laser interaction effects of electromagnetic absorption and microstructural defects on hot-spot formation in RDX-PCTFE energetic aggregates}, volume={22}, ISSN={["1361-651X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84903137725&partnerID=MN8TOARS}, DOI={10.1088/0965-0393/22/5/055013}, abstractNote={Hot-spot formation in energetic aggregates subjected to dynamic pressure loading and laser irradiation has been investigated. Specialized finite-element techniques with a dislocation-density-based crystalline plasticity constitutive formulation and thermo-mechanical coupling of heat conduction, adiabatic heating, laser heating and thermal decomposition were used to predict hot-spot formation in RDX–polymer aggregates subjected to dynamic pressures and laser energies. The effects of the electromagnetic absorption coefficient coupled with void distribution and spacing, grain morphology, crystal–binder interactions and dislocation densities were analyzed to determine their influence on the time, location and mechanisms of hot-spot formation. Four different mechanisms for hot-spot initiation under dynamic laser and pressure loads were identified, which depend on the localization of plastic shear strain and laser heat absorption within the aggregate. The predictions indicate that hot-spot formation is accelerated by higher absorption coefficients and by localized plastic deformations that occur in areas of significant laser heating.}, number={5}, journal={MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING}, author={Brown, Judith A. and LaBarbera, Darrell A. and Zikry, Mohammed A.}, year={2014}, month={Jul} } @article{brown_vendra_rabiei_2010, title={Bending Properties of Al-Steel and Steel-Steel Composite Metal Foams}, volume={41A}, ISSN={["1543-1940"]}, DOI={10.1007/s11661-010-0343-y}, number={11}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Brown, Judith A. and Vendra, Lakshmi J. and Rabiei, Afsaneh}, year={2010}, month={Nov}, pages={2784–2793} }