Issue 49

L. Restuccia, Frattura ed Integrità Strutturale, 49 (2019) 676-689; DOI: 10.3221/IGF-ESIS.49.61

0.66

  V 

2

3

 





3.87 2.04  





0.76 2.28 

(2)

1





2





1

where α= ( a 0

+ HO)/( d + HO), and l , a 0

, HO, d and b are those indicated in Fig. 3:

Figure 3 : Testing configuration and geometry of specimen [27].

The critical stress intensity factor, K IC

, represents the resistance opposed by the material for a crack extension in plane strain

condition for stress state near the crack tip, with limited plastic deformation. In case of Mode I, the stress intensity factor K IC can be expressed as:

   

   

3 2





P

2 0.5 ) 2 W l d b

a

3(



  

max



K

F

N m

(3)

IC

where:

 





2

1.99 1 

 



2.15 3.93 2.7   



  



F

(4)

3 2

  1 2 1 3    





and α = a/d, P max

= maximum load [N], l, d and b are the span, depth and width, respectively [27]. After the determination

of K IC

, the fracture energy, G F

, has been evaluated according RILEM TC50-FMC [21] as:

W mg 

0 

N       m

0



G

(5)

F

A

lig

Figure 4 : Set up and test of experimental mortars: three-point bending test.

681