Issue 53

A. Desai et alii, Frattura ed Integrità Strutturale, 53 (2020) 426-433; DOI: 10.3221/IGF-ESIS.53.33

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].

90° lamina

45° lamina

0° lamina

0° lamina

90° lamina

45° lamina

0° lamina

0° lamina

(b)

(a)

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:

2 sQ a 

a       I W W

6



K

F

(1)

I

3/ 2 ( / )

Q a W

a      



K

F

(2)

II

II W

1/ 2

1/ 2 (1 / ) 

W a W

where

( ) F L d Q L d    (

)

(3)

The functions F I and F II were defined by Murakami [14], as polynomial functions:

2 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) 3

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)

428