Issue 48

P. Bernardi et alii, Frattura ed Integrità Strutturale, 48 (2019) 97-104; DOI: 10.3221/IGF-ESIS.48.12

also analysed through DIC image elaboration in terms of horizontal strains, as shown in Fig. 8b, where is evident the localization at crack tip. From the analysis of the vertical displacement field, it is possible to compute the deflection  , removing rigid displacements at the supports, and so representing the specimen response in terms of load - midspan deflection (Fig. 9a). Fig. 9b also shows the experimental results in terms of load - CMOD.

3

 [MPa]

f t,max

2.5

2

f t,mean

1.5

f t,min

1

0.5

 L [mm]

0

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

(a)

(b) Figure 5 : (a) View of the specimen at the end of the test: detail of fibers crossing crack surfaces; (b) stress vs. elongation  L for series 1 specimens under direct tension.

Specimen ID

Width [mm]

Thickness [mm]

Peak Load [kN]

f t,ax

[MPa]

T-1-1 T-1-2 T-1-3 T-1-4 T-1-5 T-1-6

30.06 29.91 30.12 30.06 29.91 29.98

14.64 14.80 15.05 15.24 14.60 15.03

0.523 0.740 0.995 0.632 1.119 0.720

1.19 1.67 2.20 1.38 2.57 1.60

f t,ax,mean = 1.77 MPa Table 1 : Direct tension tests, 1 st series: cross section dimensions of the central part of the specimens, achieved peak load and corresponding axial tensile strength (f t,ax ).

Specimen ID

Width [mm]

Thickness [mm]

Peak Load [kN]

f t,ax

[MPa]

T-2-1 T-2-2 T-2-3 T-2-4 T-2-5 T-2-6 T-2-7 T-2-8 T-2-9

38.17 30.19 33.20 29.27 30.71 30.18 30.17 29.77 29.58

15.40 14.92 14.04 14.60 15.23 14.24 14.03 14.34 13.99

1.194 0.979 1.080 0.860 1.177 0.527 0.719 0.975 1.005

2.03 2.18 2.32 2.01 2.52 1.23 1.70 2.28 2.43

f t,ax,mean = 2.08 MPa Table 2 : Direct tension tests, 2 nd series: cross section dimensions of the central part of the specimens, achieved peak load and corresponding axial tensile strength (f t,ax ).

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