Issue 49

L. Restuccia, Frattura ed Integrità Strutturale, 49 (2019) 676-689; DOI: 10.3221/IGF-ESIS.49.61 681     2 3 1 2 0.66 0.76 2.28  3.87 2.04 1 V            (2) 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 2 3( 0.5 ) 2 max IC P W l a K F N m d b              (3) where:          2 3 2 1.99 1 2.15 3.93 2.7 1 2 1 3 F                (4) 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: 0 0 F lig W mg N G A m          (5) Figure 4 : Set up and test of experimental mortars: three-point bending test.