SEM fractography of a porous SiC (nEOI)

Ceramic materials are being more and more used in bi-layer shielding solutions. When impacted, substantial tensile damage creates within the ceramic tile that manifests as numerous oriented cracks. Understanding the dynamic fracture response under high strain-rates and at the level of a single dynamic crack is of major importance in pushing forward the design of resilient ceramic-based armour solutions. Single fragmentation of brittle materials in dynamic is possible with adapted experimental techniques. For that, one of these methods is the notched-Edge-On-Impact (nEOI). This experimental method enables the study of a single quasi-straight dynamic crack which propagates through a single-notched rectangular specimen. When the projectile impacts the specimen, a compressive pulse propagates and reflects to the free end of the sample, thus changing of sign and becoming a tensile pulse. Once the tensile pulse arrives on the notch, if the stress intensity resulting from the stress concentration at the notch tip is sufficient, a crack initates. The crack propagation process is filmed with an ultra-high-speed camera with 5 million frames per second (5 Mfps), that is 0.2 μs of exposure time. → This experimental technique, performed on a silicon carbide ceramic (Saint-Gobain's Forceram® SiC), can be used to characterise the dynamic crack velocity when coupled with Digital Image Correlation (DIC). This image shows two locations of the fracture surface based on Scanning Electron Microscopy (SEM) with secondary electrons giving topography information. A transgranular brittle fracture is observed.