Xiaoyu Zhang presented his research at the Gordon Research Seminar
The title of Xiaoyu’s presentation was: “Experimental and Computational Investigations of Interface Chemistry Dependence and Parameter Sensitivity of Dynamic Response and Fracture in Energetic Materials”
Energetic materials are sensitive to mechanical shock and defects caused by a high velocity impact may result in unwanted detonation due to hot-spot formation. In order to understand the underlying mechanism, characterization of high strain rate mechanical properties needs to be studied. One of the key factors that can contribute to this type of defect is the failure initiated at the interfaces such as those between Hydroxyl-terminated polybutadiene (HTPB)-HMX (or HTPB-Ammonium Perchlorate (AP)). In this work, interface mechanical properties of HTPB-HMX (and HTPB-AP) interfaces are characterized using nano-scale impact experiments at strain rates up to 100 s-1 and laser shock experiments at strain rates approaching 106 s-1. For HTPB-HMX samples, Dantocol is used as the binding agent and for HTPB-AP samples, Tepanol is used as the binding agent. The impact response is determined in the bulk HTPB, HMX, and AP as well as at the HTPB-HMX and HTPB-AP interfaces. A mechanical Raman spectroscopy setup is used to measure interface separation energy and cohesive traction values with change in interface chemistry, and power law viscoplastic constitutive model is fitted to experimental stress-strain-strain rate data. For the HMX particles, a crystal plasticity finite element (CPFE) model that incorporates thermal activation and phonon drag mechanism is employed to capture its plastic deformation evolution under impact loading, temperature rise and interactions with HTPB. Both the viscoplastic interface and the CPFE particle models are used in a micromechanical cohesive finite element model (CFEM) based framework to predict the dynamic response of the energetic materials. The model predictions as well as the experiments may exhibit significant variations due to uncertainties associated with loading, microstructure state, experimental setup, as well as the model assumptions and parameters. In particular the parametric uncertainties and sensitivities associated with the mechanistic models and microstructure employed in the numerical model are analyzed through global sensitivity analysis.