A simplified model for ballistic initiation of thin energetic targets by micro-flier impact

• Novel diagnostics and applications involve small-scale energetic components.
• A model is posed for high-speed impact of micro-fliers with thin energetic targets.
• The model accounts for early-time waves and late-time target deformation mechanics.
• Impact induced detonation is based on measured critical shock energies.
• Micro-flier–target configurations are predicted that detonate without perforation.

Novel techniques involving high-speed impact (~500–1500 m/s) of laser generated micro-fliers with thin metallic targets having a layer of reactive solid deposited on their back side (~10–100μm) are being developed to interrogate its shock-induced chemistry. Because mass spectrometry is performed in vacuo on the reactive side of the target to identify the chemical species produced, it is important to initiate chemistry without perforation of the target plate by the flier. An analytically tractable model is formulated in this paper to guide experimental development by predicting the ballistic response of large numbers of micro-flier–target configurations in a computationally inexpensive manner. The model is posed in terms of multi-component conservation principles and interaction terms that account for important features of both the early-time wave mechanics and the longer-time target deformation mechanics including flier–target adhesion. The model, validated using published data for larger scale inert flier–target configurations, is used to predict the response of micro-scale configurations consisting of aluminum fliers and steel targets. Scanning Electron Microscopy (SEM) of post-impact, inert flier–target micro-scale configurations is used to both highlight target deformation and damage and to motivate modeling simplifications. To illustrate the model, configurations that result in initiation (detonation) of the high-explosive PETN (C5H8N4O12) without perforation of the steel substrate are parametrically characterized in the form of ballistic initiation maps based on its empirical critical shock energy.