X Li et al/ Materials Science and Engineering C 28(2008)1501-1508 o Crack propagation direction 10. Optical image of in situ observation of bridging and crack deflection within the BN interfacial layer in specimen BS-5. Fig. 11. Optical image of in situ observation of broken bridging ligaments in the BN interfacial layer in specimen BS-5 2.5 Fig 12 AFM image of the area in front of the crack tip along the crack propagation direction in the bn interfacial layer in specimen BS-5, showing coalescence of the pre-exiting t Delamination cracking Crack kinking and propagation Fig. 13. Opt ges of in sin observation of crack propagation in an unsteady-state manner in specimen BS-5 with crack deflection, kinking out of the BN interfacial layers, andFig. 13. Optical images of in situ observation of crack propagation in an unsteady-state manner in specimen BS-5 with crack deflection, kinking out of the BN interfacial layers, and through-thickness cracking. Fig. 10. Optical image of in situ observation of bridging and crack deflection within the BN interfacial layer in specimen BS-5. Fig. 11. Optical image of in situ observation of broken bridging ligaments in the BN interfacial layer in specimen BS-5. Fig. 12. AFM image of the area in front of the crack tip along the crack propagation direction in the BN interfacial layer in specimen BS-5, showing coalescence of the pre-exiting microvoids and microcracks. 1506 X. Li et al. / Materials Science and Engineering C 28 (2008) 1501–1508