Issue 50

M. Baghdadi et alii, Frattura ed Integrità Strutturale, 50 (2019) 68-85; DOI: 10.3221/IGF-ESIS.50.08

stiffness. For this purpose, and in comparison, with the rectangular patch, a patch shaped arrow with a doubly smaller surface and doubly important stiffness (Fig.10) leads practically to the lower values of the shear stresses relative to the YOZ planes, in the adhesive layer, as shown in (Fig. 17 c). These stresses are due to the crack lips opening (fig. 17c) in mode I.

a)

0 1 2 3 4

0 1 2 3 4

a)

-5 0 5 10 15 20 25 30 35 40 45 -6 -5 -4 -3 -2 -1 Shear stress XY (MPa) Rectangular Patch Elliptical Patch Patch ShapedArrow Octagonal Patch Trapezoidal Patch Patch ShapedH Patch shaped butterfly

15,0 15,5 16,0 16,5 17,0 17,5 18,0 18,5 19,0 19,5 20,0 20,5 21,0 -5 -4 -3 -2 -1 Shear stress XY (MPa) Rectangular Patch Elliptical Patch Patch Shaped Arrow Octagonal Patch Trapezoidal Patch Patch Shaped H Patch shaped butterfly

Path (mm)

The total distance of the path (mm)

25

Rectangular Patch Elliptical Patch Patch Shaped Arrow Octagonal Patch Trapezoidal Patch Patch Shaped H Patch shaped butterfly

b)

b)

20

20

15

15

10

Rectangular Patch Elliptical Patch Patch Shaped Arrow Octagonal Patch Trapezoidal Patch Patch Shaped H Patch shaped butterfly

10

5

5

0

Shear stress XZ (MPa)

Shear stress XZ (MPa)

-5 0 5 10 15 20 25 30 35 40 0

15,0 15,5 16,0 16,5 17,0 17,5 18,0 18,5 19,0 19,5 20,0

Path (mm)

The total distance of the Path (mm)

-2 -1 0 1 2 3 4 5 6 7 8 9 1011 12 13 1415 16 17 18 1920 21 22 -64 -62 -60 -58 -56 -54 -52 -50 -48 -46 -44 -42 -40 -38 -36 -34 -32 -30 Shear stress YZ(MPa) Path (mm) Rectangular Patch Elliptical Patch Patch Shaped Arrow Octagonal Patch Trapezoidal Patch Patch Shaped H Patch shaped butterfly c)

0 5 10

c)

-4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 -65 -60 -55 -50 -45 -40 -35 -30 -25 -20 -15 -10 -5 Rectangular Patch Elliptical Patch Patch Shaped Arrow Octagonal Patch Trapezoidal Patch Patch Shaped H Patch shaped butterfly

Shear stress YZ (MPa)

The total distance of the Path (mm)

Figure 17 : Effect of the patch shapes on the shear stresses level in the adhesive layer along the crack propagation path. repaired crack a =18 mm, Applied stress = 150 MPa.

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