Illumination and Recording Accessories for High-Speed Photography to Study Dynamic Fracture of Brittle Solids
[Technical Report, Final Report]
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Lightweight transparent armor structures are generally layered structures. The interface strengthand toughness play a critical role in deflecting or promoting branching of growing cracks and effectively absorbenergy. This helps in the development of failure resistant transparent armor alternatives to thick single layerdesigns. A mechanics-based research in this regard would require understanding how a dynamically growing crackinteracts with one or more interfaces. This in turn demands development of new experimental techniques toperform full-field mechanical measurements at high spatial and temporal resolutions. The PI has an ongoing AROgrant W911NF-16-1-0093 entitled Dynamics of Crack-Interface Interaction in Layered Transparencies AnExperimental Investigation using Novel Optical Technique. The present Research Instrumentation RI grant W911NF-17-1-0355 was to acquire instrumentation in support of the above effort. The specific items acquiredwere i a high energy LED pulsed laser light source, ii a high-intensity flash illumination system, iii a long focallength zoom lens and accessories. Item i minimizes blur in the recorded images in the vicinity of a rapidly growingcrack when used in conjunction with an ultrahigh-speed camera currently available in PIs lab. Item ii is a generalpurpose high energy solid-state flash lamps to replacesupplement aged ones currently used by the PI. Item iii isto perform paraxial imaging of fracture events at very high framing rates 1 million fps from relatively longdistance yet achieve the necessary exposure during photography.