Crack-tip damage zone

Chakachery, E.A. and Bradley, W.L. (1987). A comparison of the crack tip damage zone for fracture of HexccI FI85 neat resin and T6T145/FI85 composite. Polym. Eng. Sci. 27, 33-40. 

In the SCG region failure occurs through formation and extension of a fibrillar crack-tip damage zone (following inter-lamellar cavitation and breakdown of inter-lamellar ligaments) as Kc decreases the fibrillar features become progressively finer. 

Fig. 20 a Side-view of the crack-tip damage zone in a CT specimen of iPP with Mw of 455 kg mol-1 deformed at about 3 m s 1. b Oblique view of the damage zone showing the curved deformation front, c TEM micrograph of the collapsed fibrillar structure of the crack-tip craze, d Detail of structure at the craze-bulk interface [19]... 

Fig. 22a-c BSE-SEM images of crack-tip microdeformation in iPP containing approximately 80 wt% ji phase tested at 0.001 m s 1 and 25 °C. a Overview of the crack-tip damage zone, b and c details from the periphery of the damage zone. The arrows indicate the loading direction [24]... 

Fig. 8.17 Cavitation at GBI junctions in the vicinity of a crack tip damage zone created by cyclic fatigue loading in AI2O3/S1C composite tested at 1400°C in air.S7...

Figure 2. Bright-field TOM image of BCB-MI resin,. showing the plane-strain core region of the DN-4PB crack-tip damage zone. The crack propagates from right to left.

For transmission optical microscopy (TOM) investigations, thin sections (c.a. 40 pm) of the mid-section of the DN-4PB crack tip damage zone were obtained by sectioning and polishing. These thin sections were then examined using an Olympus BX60 optical microscope under bright field. 

The two samples were further studied by the DN-4PB technique to reveal the toughening mechanisms. Crack tip damage zone was examined by TOM and TEM (Figures 3-4). Extensive shear yielding (Figure 3a) and massive... 

Figure 3. TEM Micrographs of DN-4PB Crack Tip Damage Zone in Sample B specimen (a) Crack Wake and Shear Yielding and (b) Crazing.

Figure 5. Schematic of a Crack Tip Damage Zone with Two Typical Toughening Mechanisms Shear Yielding and Crazing.

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