Fig. 1: Loading and imaging complex 3D cracks.
From: Complexity of crack front geometry enhances toughness of brittle solids
a, Schematic of the experimental setup. Confocal microscopy is used to image fluorescent light emitted from the sample in the focal plane. The experiment is carried out in water to match the optical index. Remote mode-I tensile loading is applied. b, A volumetric reconstruction of a complex crack tip near the critical stress required for propagation. The geometry of the crack tip is clearly not symmetric through the thickness, as can readily be seen by the features on the crack surface. c, Volumetric reconstructions of the same crack at different values of the applied strain demonstrate the experimental procedure: a complex crack tip is loaded with incrementally more strain, and allowed to equilibrate. Strain steps are kept very small to ensure resolution of the value of strain immediately below that for crack propagation, defining the critically loaded crack geometry.
