Issue 53

A. Desai et alii, Frattura ed Integrità Strutturale, 53 (2020) 426-433; DOI: 10.3221/IGF-ESIS.53.33 428 composites. In order to overcome such difficulties, the applied loads are recorded. Using recorded values of peak load, the fracture toughness K IC and K IIC will be calculated. The magnitudes of K IC and K IIC have been calculated by analytical formulations given in Eqns. (1) and (2) [3]. Figure 1: fiber directions of glass laminate obtained in (0/45)° and (0/90)° respectively The analytical formulations of K I and K II (He and Hutchinson) [3] are as follows: 6 2 sQ a a K F I I W W         (1) 3/ 2 ( / ) 1/ 2 1/ 2 (1 / ) Q a W a K F II II W W a W         (2) where ( ) ( ) F L d Q L d    (3) The functions F I and F II were defined by Murakami [14], as polynomial functions: 2 3 4 5 ( / ) 1.122 1.121( / ) 3.740( / ) 3.873( / ) 19.05( / ) 22.55( / ) / 0.7 I F a W a W a W a W a W a W for a W        (4) 2 3 4 ( / ) 7.264 9.37( / ) 2.74( / ) 1.87( / ) 1.04( / ) 0 / 1 II F a W a W a W a W a W for a W        (5) 2 2 K K K eff I II   (6) (a) (b) 45° lamina 0° lamina 45° lamina 0° lamina 0° lamina 90° lamina 0° lamina 90° lamina