Issue 44

A. Saoud et alii, Frattura ed Integrità Strutturale, 44 (2018) 25-34; DOI: 10.3221/IGF-ESIS.44.03 32  Guitard, knowing that the density of wood is d = 0.60 g / cm 3 [14]. To facilitate the comparison of results with the literature, while knowing that almost most researchers in this component uses this database. S 11 -1 (MPa) S 22 -1 (MPa) S 33 -1 (MPa) S 12 -1 (MPa) S 23 -1 (MPa) S 31 -1 (MPa) S 44 -1 (MPa) S 55 -1 (MPa) S 66 -1 (MPa) 1355.5 922.5 19355 2842 45950 51750 893.35 1173 117.8 S ij : The components of the compliance matrix which are in function of the elastic constants of the wood Table 4: Elastic constants of Thuja.  The GIIC mode II initiation fracture toughness. G, the initiation fracture toughness corresponding to a small crack increment can be computed using the analytical form according to IRWIN-KIES [6]:    P C B a 2 II G 2 (1) where B is the thickness of the specimen; P is the applied load and a the crack length.     c a a c C G B a 2 IIC p 2 (2) The critical value of G II , G IIc , is then found by measuring the critical load Pc needed to fracture a specimen containing a crack of length ac, and using the slope of the compliance curve at this same value of a[13] : We note that: C = ma 3 + C 0 (3) Where m and C 0 are determined by a linear regression of the experimental curve C as a function of a 3 The critical stress intensity factor K IIC Mode II initiation fracture toughness G II and stress intensity factor K II , assuming elastic linear behavior, are related to each other. The relationship between these two quantities is obtained using the following equation [14]:                      1 1 2 2 2 12 66 IIC 11 22 IIc 11 11 2S S K S S G S 2S 2 (4) Table 5 : Mode II initiation fracture toughness and corresponding stress intensity factors. a(mm) G II N/m Mean value Standard deviation K II MPa.√m Mean value Standard deviation 4 113.95 33.37 0.40 0.06 6 221.99 37.14 0.56 0.05 8 174.65 9.20 0.50 0.05 10 237.20 11.87 0.58 0.05 12 267.06 62.51 0.61 0.02